Monday, November 10, 2014

Winter is Coming... And Not in a Good Way.

Winter is coming! But probably not in the way that you want it to. I guess this year it decided to come three weeks early and it looks like it's here to stay.

As many of you have probably heard by now, the "polar vortex" is coming and we're all going to freeze to death!

No, just kidding.

But this is how many media outlets are presenting the latest outlook for the period of mid-late November.

And it's a myth. It's a sensationalist fabrication of the journalist attempting to make a "newsworthy" story.

First, the "polar vortex" is not coming down from the Arctic. It didn't even technically come down "last winter" either. In reality, intense warming in the lower stratosphere, aided by a meridional polar jet stream caused the polar vortex to split, forcing the cold air southward on both sides of the hemisphere. It was a "piece" of the polar vortex, but it wasn't the "polar vortex" itself.

What's happening right now is the same thing.

Second, it isn't "comparable" to Hurricane Sandy or any other extreme event. The only thing "extreme" about it is that temperatures in the core of the Arctic air mass associated with it will be nearly three standard deviations below the mean temperature for this time of year. In other words, temperatures will be colder than approximately 99% of all recorded Novembers for many locations. It will definitely be cold and definitely close to historic in terms of longevity and intensity.

So, let me give a brief synopsis of what's happening, and what we expect to happen over the next few weeks.

Let's begin with looking at today's weather map. Right now, we have a sprawling low-pressure system centered in the Central Plains and quickly developing to the northeast. By late tonight, the surface low will become closed and quickly move eastward. By Tuesday night, the storm system will swing a polar front through the region, dropping temperatures into the upper 20's by early morning.

WPC North American surface analysis

By Wednesday, a vast Canadian vortex will be centered to our north, pivoting multiple minor waves across the area at the same time. The vortex will keep the cold-air mass in place through the weekend. By Sunday, the general model consensus is that a slight moderation in temperatures will occur, as another wave of low pressure approaches from the west. While nothing major is anticipated, we could see a few snow showers and/or light snow during the day. Temperatures will likely be in the mid-upper 30's.

This is when major model discrepancies come into play. There are numerous variations between model solutions right now in terms of the strength, placement, and timing of another wave of Arctic air into the region. The only thing that is somewhat certain at this point is that temperatures will likely be colder than what they will be with the first wave of Arctic air. Models continue to contradict each other in terms of when this cold wave will make it to the area, how long it will last, and ultimately, how cold it will get. At this point, there's nothing much else I can say.

However, given current observations and trends in long-term indicators, it appears to me that a more prolonged period of Arctic air is likely. This is due to two significant factors:

1. Intense ridging across Alaska and far northwestern Canada will be nearly three standard deviations above normal, which indicates an incredibly strong ridge of high-pressure. This will likely cause an omega block to form, which will trap cold, Arctic air in most of the United States, especially east of the Continental Divide. Blocking across Greenland could become a major factor as well, depending upon the strength of the Scandinavian ridge that is expected to develop in response to the polar-vortex breakdown.

2. Snow-cover build up has accelerated once again across Canada and now across the Northern Plains and Upper Midwest [especially after the current snowstorm]. This will lessen any air mass modification that might occur over the next few weeks and help to lock the cold-air in. This will especially be the case if we see several more winter weather events in the next two weeks or so. Right now, I am monitoring the possibility for a possible snow-accumulation event occurring sometime next week, but the details are too uncertain to say much else.

http://www.hpc.ncep.noaa.gov/medr/d7500wbg.gif

While I do not expect this wave of cold-air to last much longer than a week or two at the current time, it is possible that this colder-than-normal weather sticks around for Thanksgiving time. Given the fact that long-range meteorologists are even surprised at the magnitude of this event, it would not even surprise me if we see a significant winter weather event around the time of Thanksgiving.

Tuesday, November 4, 2014

Comparisons Between November 1976 and the Present Pattern




Differences and comparisons between Nov. 1976 pattern and current predicted pattern for the 8-14 day period:

As I was doing research today during school on the ensemble forecasts for the next few weeks, as well as the analogues that the Climate Prediction Center puts out on a daily basis, I found an interesting trend. Nov. 1976 keeps appearing as one of the analog years.

So, I decided to do a comparison between the two.

First, the overall pattern for Nov. 1976 was one in which there was an enormous trough stretching from western Siberia to just south of the Aleutian islands. This is the type of trough that is currently being forecasted by ensemble guidance due to the influence of the incredible remnants of the super typhoon. Due to this influence on the global longwave pattern, I don't expect that this longwave trough will break down very quickly. And as long as this trough remains in place, the pattern will remain blocked and stuck, meaning that a mean trough will continue over Canada and the Central/Eastern United States.

THIS DOES NOT MEAN THAT THERE WON'T BE ANY PERIODS OF ABOVE NORMAL TEMPERATURES. It just means that the pattern will be dominated by bouts of Arctic air, and occasional waves of Pacific air [due to the fact that blocking won't be as prevalent as we would like it until the effects of the SSW become more prevalent].

Given that the longwave won't necessarily be locked in place across North America, I still expect quite a bit of volatility, meaning the potential for large temperature swings and major storm-systems [mainly cutters and possibly a Nor'easter].

As for other comparisons, the Western North American ridge is pretty much in the same location that it was in Nov. 1976. Given this, and holding other factors constant, I would not doubt that this will become a more permanent feature of the winter. But this is still rather uncertain [as there always with comparisons to past analogue years]. Blocking should also be slightly farther west than what occurred in 1976-1977, which may mean that the colder air may be positioned farther west than what one would normally expect in an El Nino-like pattern.

The only main difference is that the Canadian-vortex in Nov. 1976 seems to have been much stronger, but I don't doubt that the Canadian vortex that is forecast to drop into the United States sometime next week could be just as intense. I just don't expect the Canadian vortex to be as consistently strong as it was in '76.

Another difference is perhaps the fact that there was a lack of strong blocking across the poles. Based upon the mean 500 MB pattern from Nov. 1976, it appears that the PV was stronger across the poles, but this is more likely due to the fact that the Arctic regions were well below the 1981-2010 normal [average column temperatures] in comparison to today. I don't know if this will have any impact on the going forecast for late Nov. to early Dec. but it could be significant in terms of potential winter-storms, and Arctic outbreaks.



Thursday, October 16, 2014

NOAA's Winter Outlook and My Criticisms

Okay, I would like to begin by saying that I am not a "degreed" meteorologist. I am not paid by the government. I am not even in college *yet. I don't have much experience either. I've been attempting to forecasting the weather for about three or four years now, based upon my limited knowledge of atmospheric science and the countless hours I've spent reading books and participating in internet discussions. I'm certainly not a professional by any definition of the word.

With that being said, I would like to share a few of my thoughts on the National Oceanic and Atmospheric Administration's latest released winter-outlook.

Today, the Climate Prediction Center released its forecast outlook for the months of December 2014 through February 2015, which is generally considered the winter-outlook period by NOAA. Keeping consistent with CPC "tradition", they have released both the temperature outlook and the precipitation outlook.

For one thing, you'll notice that the CPC's outlooks are relatively similar to most other winter-outlooks; they both show expected precipitation and temperature anomalies.

However, the difference between the CPC's outlook and most other outlooks is that the CPC relies upon probabilities for the map. If you'll notice the maps [see above], the defining feature of the shaded regions is that of probabilities. The probabilities indicate the amount of certainty that climate forecasters at the Climate Prediction Center have for that particular forecast. For instance, in the case of the precipitation map, the "wetter" regions are actually regions where the CPC is MORE confident that higher-than-normal precipitation will occur during the winter months. In the case of the temperature maps, the "warmer" regions denote regions where the CPC is more confident that higher-than-normal temperatures will occur.

There is also a large region of "equal chances" on both maps. This is a category that the CPC uses when it is most uncertain about a specific forecast. In reality, it just means that the outlook for these regions is highly uncertain and could swing either way.

But I have a major criticism of this type of forecasting.

And take them for what they are-- opinions. That's it.

My problem with the CPC's forecast is two-fold. In the first place, the forecast is too general and vague for anyone in the general public to take seriously. The CPC would be better off not releasing a public forecast such as this and keeping quiet about press-releases. Of course, it is the job of the CPC to release long-range outlooks such as this. But it is all too easy for the general public to misunderstand what is actually being said. Most will take a first glance at the maps and then conclude that the Great Lakes will be dry and normal for the winter [probably good news for anyone who hates snowy, cold weather!]. Yet, that is precisely what the CPC is NOT saying! In other words, the CPC is about as bad at communicating statistical information to the public as USAToday is.

My second criticism has more to do with my own personal thoughts on the winter.

First, I think the forecast is too reliant upon the fact that an El Nino is developing in the Equatorial Pacific. While it is not certain how strong the El Nino will become in the next few months, recent strengthening of warm SST anomalies along the Equator has lead many forecasters to believe that a long-term El Nino is finally developing [having been forecast to do so two years ago].

According to what the "textbooks" say about a general El Nino pattern, a general rule of thumb for the winter-outlook is that the winter will feature above normal temperatures across the northern United States, Canada, and Western North America. Also included in this "rule of thumb" is that the Ohio Valley and Great Lakes will generally see below normal precipitation, along with equal chances of being warm or cold for the winter-months. Most importantly, an El Nino usually correlates with a cold, wet Southern winter.

As you can see, this "textbook" definition almost exactly matches the forecast released by the CPC today.

I agree that an El Nino is developing in the Pacific. A more dominant +PDO, along with warmer waters in the Western Pacific will definitely allow it to develop further.

However, given the weak state of the El Nino currently [in fact, it isn't even officially classified as an "El Nino" until SST anomalies have been consistently above +0.5 C for three months or longer], there is no reason to believe that it will be the main factor driving the winter-time pattern, as it was with last winter season. Generally, the stronger the El Nino, the stronger the response farther north. However, in this case, the response probably won't even develop in time for the early winter season.

From what I have seen, there are much greater factors that must be taken into account.

First, I think that we will see an active Pacific jet, with a stronger southern jet towards the end of the winter. Why? Because a strong Aleutian low will likely dominate off the West Coast of North America, likely leading to a stormy pattern along the coast and farther inland. With an active Pacific jet, snow-cover across Canada will likely have a much longer chance to build southward, allowing for the long-term development of a stronger Arctic air mass.

Secondly, I believe that a lack of blocking will characterize at least part of December. Unless we see a return to an overall blocking pattern soon, I see no reason why it should rebuild before December. Of course, it's very likely that blocking will redevelop by later in the winter [for several reasons], but December will likely feature near normal temperatures for most of the United States, with a general stormy trend.

Lastly, I believe that blocking will return by the latter portion of the winter. Stratospheric warming events have a much higher likelihood this winter, and when they do happen, they generally lead to an increase in blocking over the Arctic regions. If this is the case, I expect a downtick in storminess towards January and February, but with overall colder conditions. While storminess may increase along the East Coast and South, drier and colder conditions will likely prevail in the Northern Plains and Midwest.

Even though I have a lot of respect for the CPC and their forecasts, I do not believe that their winter outlooks are overly helpful, and in many cases, I strongly disagree with their conclusions.

*I am going to be going to college soon however. I will probably be going into the field of meteorology or some related mathematics/physical science.

Tuesday, September 9, 2014

SEVERE WEATHER OUTLOOK

After a seemingly long period of rather warm, humid weather to end the summer, the pattern is finally transitioning to something that is far more recognizable as fall weather. Along with this cooler weather, however, comes the possibility for more organized storm systems, as well as severe weather. In this instance, we have a strong potential for severe weather that could be fairly widespread across the Great Lakes and Ohio Valley regions.

Here's what's going on: A strong trough in west central Canada is digging southward into the United States right now. A shortwave is expected to eject from the trough within the next few hours, causing a developing frontal zone to drop southward and allow rapid cyclogenesis to commence.

Here's the position of the surface low pressure system right now:





Today, this low pressure system will continue to organize along the front, and eventually move to the northeast. By tomorrow, the low-pressure system will likely be in Wisconsin, traveling northeast into Canada at a rather rapid pace.

At the same time that this cyclogenesis occurs, a strong cold-front will develop alongside the low-pressure system, drawing colder, drier air out of Canada and into the United States. Warm and moist "return-flow" from the Gulf of Mexico will also be drawn into the "battleground", setting the stage for an unstable and volatile atmosphere in the lower Great Lakes and Ohio Valley region. At the same time, strong winds in the upper atmosphere will allow the system to continue to organize and will also provide the support that tomorrow's thunderstorms will need in order to become severe.

All of this is expected to come together to allow for a decent severe weather outbreak to unfold across the area. However, there are still a few uncertainties as to what  will happen.

1.) Cloud-cover/early morning rainfall- Many forecasters are concerned that early morning cloud-cover across the region will remain through the afternoon, suppressing rising temperatures from making it into the 80's. This will lead to a significant reduction in instability for the afternoon hours. While it won't rule out severe weather, it will definitely limit the impact of the severe thunderstorms later in the afternoon and early evening.

At the same time, however, some models, such as the NAM and SREF, are predicting moderate instability to develop across the area, in response to rising boundary-layer moisture and some breaks in the cloud-cover. If this occurs, the severe weather threat will be much more imminent.

2.) Stronger low-level jet winds may shift to the east of the area before the actual cold-front arrives, possibly limiting some of the severe potential. Although I do not see this as a potential problem as of yet, it is something that I will continue to monitor.

Given the above considerations and the factors going into this outbreak, it appears that our main threat will be widespread damaging winds. Even if we don't see enough instability tomorrow, damaging winds will still be a major threat with these thunderstorms. It is also possible that some areas see significant winds above 65 kts [75 mph] in some thunderstorms. If conditions are more unstable than currently forecast, we may in fact see a few isolated tornadoes as well.


Damaging wind threat for the area is at the forty-fifth percentile

I will keep you updated on our FB page.

Monday, August 11, 2014

Rain and Thunderstorms Today

Today's forecast is rather gloomy for the late summer months. Showers and thunderstorms are expected to development and move repeatedly over the area late this morning and early afternoon. The incredibly humid air mass, in combination with weak-moderate instability will lead to heavy, slow-moving thunderstorms which could lead to localized flooding in some areas.

Showers and thunderstorms should end across the area by the late evening, giving way to cloudy skies and drier conditions by the morning.




Sunday, June 29, 2014

In Remembrance of the Great "Land Hurricane"

The massive storm that swept through the area on Friday, June 29th, 2012, will not soon be forgotten by many folks around the northwest Ohio and northeast Indiana region. Packing winds of over 80 mph, the derecho [pronounced "day-RAY-cho"] raced through, uprooting trees, tearing off roofs, and knocking down hundreds of power-lines across the region. But it wasn't just our area that was impacted by this record-setting storm. The monster caused widespread and intense damage from northwest Indiana all the way to the East Coast, making it one of longest and most intense derechoes to ever impact the United States east of the Mississippi River. In total, the storm caused billions of dollars in damage and cut-off electricity to more than three million people.

In any given year, northwest Ohio and northeast Indiana are usually impacted by one or two derechoes in the summer. However, derechoes as violent as the one we experienced in late June 2012 are rare across the area. Derechoes, by the Storm Prediction Center definition, most produce significant wind damage [winds of 60 mph or greater] over a distance of 200 miles. However, this derecho produced winds in excess of 70 mph over a distance of over 800 miles. The Storm Prediction Center received around 900+ wind reports from the system that day. This made the event unique, rare and not likely to occur again for many years. So what factors lead up to this impressive event?

One of the major factors in the production and the sustenance of the system over a long distance was the fact that a weak, Canadian cold-front had settled across the area. North of the front, temperatures had dropped into the lower 90's, with dew points in the low-mid 60's. South of the front [the front was basically along the U.S. 30 corridor], temperatures were in the mid-upper 90's and dew points were in the low-mid 70's [Fort Wayne had reached the mid-90's with a dew point in the low-mid 70's by noon]. The incredibly hot and humid air mass present south of the front caused instability levels to sky-rocket. One of the parameters used to measure instability is known as CAPE [or Convective Available Potential Energy]; normal values of CAPE range from 1000-3000 J/kg on any given summer day. On this particular summer day, values were as high as 5000-6000 J/kg, especially in Southern Ohio. When instability levels are this high, thunderstorm formation can be explosive and deadly, which is exactly what happened.

At the same time, the intense levels of instability in the atmosphere allowed the thunderstorms to force the dry-air downward into the lower-atmosphere, which is what contributed to the very strong wind gusts that were observed at the surface. Because of the hot, humid atmosphere south of the front, the storm system was able to maintained all the way to the East Coast. This was unusual because most storm systems of this magnitude require a great deal of wind-shear throughout the atmosphere, and on this particular day, there was little or no shear.

The most damaging aspect of this storm system was the fact that it hit with little or no warning. Early in the morning on Friday, June 29, Storm Prediction Center forecasters noted that thunderstorms were possible across the area, but they were not originally expecting severe weather. They believed that the cap, a warm-layer in the mid-levels of the atmosphere, would inhibit widespread thunderstorm formation. However, by the mid-morning hours, the SPC realized that storms were already breaking through the cap and becoming organized over northeast Illinois and northwest Indiana, which lead them to include the threat of severe weather.

By this time, the thunderstorms had already organized and were racing eastward at speeds of up to 70 mph, giving little or no advanced warning time to those in the path of the storm. That is why severe thunderstorm and tornado warnings were only issued minutes in advance of the strongest wind gusts impacting areas. The local NWS did not realize that the storm system was developing so rapidly and had to race to issue warnings in advance to protect lives and property.

The problem was made worse by the fact that people were also caught off-guard. The storms were not forecasted in advance and were only able to be tracked after it had already done considerable damage. The damage it caused was further compounded, especially when hundreds of thousands of people were without power during one of the worst heat waves that has ever hit the eastern United States. The record heat and humidity contributed to several deaths after the storm was over with.

The good news is that this system isn't one that we will likely see again for several years, if not decades. The aftermath of this massive storm has caused us to realize how important it is to remain prepared and protected during forecasted severe weather events, and hopefully a re-analysis of the event by forecasters around the nation will help to improve forecasts of similar events and save lives in the future.

Monday, June 16, 2014

WPC 500 MB FORECAST; MEDIUM-RANGE OUTLOOK

Based upon the latest ensemble and global model forecasts, it appears that a relatively active weather pattern will continue through at least the end of June. The jet-stream will remain relatively zonal and progressive, allowing for fast moving systems to move through occasionally. On the flip-side, temperatures will likely remain near or above normal, especially with every surge of heat from the Desert Southwest. No major heat waves or ridging is expected over the next few weeks [outside of tomorrow, Wednesday and Thursday], but there is the possibility of the Southeast ridge building into the United States by the end of June and early July which could contribute to the first heat wave we've had all summer. An active thunderstorm pattern will also remain in place, continuing the possibility of periodic heavy rain and even severe weather.

Friday, May 30, 2014

Warm, Pleasant Weather to Continue; Storms Next Week


Has everyone enjoyed the gorgeous weather we've had over the past few days? Because I certainly have! Looking back through the archives of the weather from the past year or so, it appears that this has been the longest stretch of pleasant warm weather that we've seen since the beginning of 2014! It certainly is nice after the terribly harsh winter we had this year.

As of now, it looks as if this stretch of nice, warm weather will continue through the weekend before a humid, tropical air mass moves into the region, allowing for several days of high humidity and the possibility of thunderstorms. Each day will feature isolated to scattered thunderstorms with intervals of partly cloudy skies and sometimes even sunny conditions. This will make the afternoons feel uncomfortable, with nighttime conditions not feeling much better [lows will likely be in the mid-upper 60's]. By mid-week, a cold front out of Canada will likely side-sweep the area, bringing drier and cooler air to the region. This cooler period does not look to last too long with the return of warmer weather and humid conditions in the long-term period for the second-week of June.

Synopsis:
Here's the general synopsis of what's going on: a weak, upper-level circulation across the South is contributing to the very slow and weak development of an overarching ridge which stretches into Canada over the next few days. Once this weak upper level low breaks down, strong moist flow from the Gulf of Mexico will surge into the area, setting up the potential for several rounds of thunderstorms. For the first two days, likely Sunday and Monday, thunderstorms will be sparse and isolated. However, as the upper-level trough descending out of Canada approaches the area, there is the potential for more organized severe weather activity along the cold front.




The upper-level trough will approach the area, driving the cold front into the region by Tuesday and Wednesday. Thunderstorms will become numerous on Tuesday, with the possibility of severe weather given moderate instability and increasing deep-layer shear. At this time, however, severe weather does not appear to be a strong threat, but I will continue to monitor the possibility. The cold front will sideswipe the area by mid-late next week, bringing temperatures down to normal levels [after a few days in the mid-80's] and much drier conditions. However, the upper-level ridge will begin to quickly re-build into the region after this, bringing warmer and drier weather once again. This appears to be the general pattern that will continue to face the region through at least early-mid June.


More details on this later.

Monday, May 26, 2014

Summer Weather's Arrival; Upcoming Blogposts

Now that school is about ready to get out, I'll be able to blog more often than I have been able to over the past few months. I realize that my last blog post on here was way back in early February, and I do apologize for that. There were plenty of winter storms that I had been following since then and other inclement weather events, but I never had the time to post on here. However, if you have been following my FB page @ Northwest Ohio Storm Prediction Center, you'll know that I've been making periodic updates over the past few months.

That being said, I have established a more regular schedule of blog posts this summer, which will deal with various topics. Depending upon how busy I am with getting ready for college, my work, etc. I will likely post at least two times a week, hopefully three times a week. Blog-posts will generally feature updates on the weather forecast, various weather topics, and even some issues that might currently be featured in the media. I will keep you updated on the various topics that I will be posting about!

Now, let's get down to business. After a long struggle for spring and summer to actually arrive, it finally has. The weather has finally settled down, and I do not expect the strong variations in temperatures that we've been seeing over the past few weeks. In fact, this entire week is expected to be at least 80 degrees or warmer, with the highest temperatures occurring today in the upper 80's to possibly lower 90's. By next week, things get sketchier with the possibility of a lingering SE Canadian trough developing and pushing a "backdoor" cold front through. Even so, I do not expect temperatures to drop much below normal; high temperatures will likely remain in the upper 70's to lower 80's. However, by early-mid June, the possibility of a much warmer period  of weather is possible, so we will have to keep an eye on that.

And given the dominance of warmth over the area for the next two weeks or so, be on the lookout for severe weather. I will keep you updated on that as well.

Sunday, February 2, 2014

Winter-Storm Potential and Model Disagreement


If you haven't heard by now, you will soon, but there is yet ANOTHER winter-storm expected to affect the area this week [and this isn't the only winter-weather event that will affect us this week; there is another system that will develop along the leading edge of the Arctic boundary by next weekend, which could bring more wintry weather to the area, but right now, we will be focusing on the more imminent threat]. Another winter-storm in the middle of an already record-breaking snowy and cold season will just add salt to the wound, the wound that could become disastrous for the area by Spring [more on that later]. At this point, the winter-storm looks to be fairly significant and it looks to produce enough snowfall to rival several of the snowstorms we've seen this year already, most notably the December 14th storm [which produced 6-10" of snow area-wide] and quite possibly even the January 5th snowstorm that we had. However, there are a few vital differences between this upcoming event and past events that we have seen. Not only this, but I want to discuss one possible analogue that could have strong implications for a major-winter storm across the area.

First, model agreement on the track of the storm is not ideal at this point. There are some differences between the global model solutions [the GFS and the GGEM being the furthest southeast, and the ECMWF being the furthest northwest of the global guidance], but nearly as severe as the differences between the global solutions and the mesoscale-model solutions, most notably with the NAM. While the GFS is indicating a weaker primary low tracking into C. Pennsylvania, the NAM is indicating that the low-pressure system will track from S. Indiana and into SW Ohio, with the low tracking just to the south of Toledo. As you can see, there is still some relative uncertainty as to the track of the storm. If the GFS's rather progressive solution verifies [which is possible, but unlikely], we will likely see a longer period of light-moderate snow, with some heavier snowfall rates in the deformation zone behind the storm. Snow-ratios would be rather high, and in combination with QPF totals of 0.3-0.5 inches [according to the GFS; not a forecast], we would see snow-totals in the range of 5-9". That is still rather impressive with how far east the GFS solution is. If the NAM's more-amped and western solution verifies, most of the area will see a long duration of heavy snow, with sleet and freezing rain mixing in for those who are near Lima and southeast. QPF totals, if this solution were to verify, would be in between 0.6-1", yielding snow totals around 8-12". At this point, it is hard to say which model is correct. The shortwave itself has not made it onshore yet to be sampled by the upper-air data. However, where the current wave is located is not in a data sparse region and just offshore of the West-Coast. Tonight will then be the night when we should see the final model trends coming into play.



At this point, I am favoring a compromise between the NAM and the global models. The NAM is likely too far northwest. Even though these types of events tend to lean "left-of-track", the NAM probably isn't handling the offshore energy all too well just yet. By tonight and early tomorrow morning, the NAM should have a better handle on the storm, and will most likely shift southeast. On the other-hand, the global models are likely too progressive. With the presence of a strong Hudson Bay vortex in a farther west position, it puts the storm in a prime position to take a shift west. Not only this, but it appears that the global models are too flat with the initial shortwave ejecting out of the SW. Even though a strong shortwave will flatten the SE ridge slightly today and tomorrow, rebuilding heights behind the system should cause the next storm-system to go much farther northwest, hence my preference towards a compromise. Given this, I expect that the storm will track from the lower Mississippi Valley [Arkansas, Louisiana, Mississippi, etc.] into Kentucky and then into Eastern Ohio. Until I have seen other-wise, I do not expect a track farther west than that. And given the above reasons, I do not believe the storm has as significant chance of taking the further south and east route. Either way, the storm will be weakened and shoved eastward by the development of a secondary low by late Tuesday night into Wednesday morning. Whether this has a significant impact on snow totals or not is too difficult to pinpoint at this time.

And as for the overall event, given the uncertainty above, I cannot give any details with any exactness or uncertainty, but at this point, I am expecting an all-snow event for most of the area. If the farther north track verifies, some portions of the area, especially near Lima and southeast could see periods of sleet and freezing rain, but that's about all of the mixing that we will have to worry about. Snow totals should range around 6-10", with the possibility of 8-12" if a stronger and slower system verifies. As for timing, there is still too much uncertainty to say anything for certain at this point.

Friday, January 24, 2014

Two Clipper Systems and the Arctic "Hounds" Awaken Once Again

After a "brief" hiatus from extremely cold, snowy and blustery weather, our exceptional winter has brought another round of weather that only seems to be suitable for regions north of the Arctic circle [not literally, but you get my point]. After seeing a full weak with temperatures slightly above normal along with rainfall, temperatures have drastically fallen with temperatures below freezing for nearly a week now [discounting Sunday-night into Monday when temperatures rose above freezing for a brief time]. Not only this, but temperatures have fallen below zero for the past several nights, and along with strong, gusty winds at times has lead to wind-chills far below zero on all three nights. Today, breezy conditions have caused another problem; intense blowing and drifting snow. This has lead to near "ground-blizzard" conditions across the region, mainly in the rural areas and has made some roads nearly impassable.

After all this crazy weather, you'd think that Mother Nature would be done by now. I'm here to bring you the solemn news that this is not so. At least two more rounds of light-moderate snowfall is expected over the next three days, followed by a longer period of bitterly cold temperatures and biting Arctic winds. The first round of snow begins tonight, with the potential for 2-4" likely across most of the area [potentially more depending upon if lift/dynamics is focused more in the dendritic-snow growth layer] through Saturday morning. Although I am not expecting heavy snowfall rates [it is possible that snowfall rates could become moderate to heavy in some areas, but it is unlikely at this time, and if it does, it will be brief, small periods of it], I do expect that extremely windy conditions will lead to incredibly low visibilities, with possible whiteout conditions at times. At the same time, the good news is that temperatures will be rising all night, to a peak of 22 or 23 by the early morning hours. However, this will not be enough to affect road conditions until windy conditions subside.

There are several potential factors that could affect snowfall amounts tonight, including:

1.) Moisture- an unusual surge of moisture will affect regions along the front, which will aid in precipitation/snowfall development. Depending upon how much moisture interacts with the DGZ layer [-10 to -18 C temperature range in the mid-levels of the atmosphere], this could enhance snowfall amounts in some parts of the area.

2.) Dynamics- Upper-level forcing could be rather significant tonight, especially as the main wave dives southward towards the region. This in combination with some jet-streak dynamics and WAA will allow light-moderate snow to develop across the area. If dynamics become more focused in the DGZ region of the atmosphere, we could see more efficient snowfall production and thus higher snowfall amounts.

While there are a few other minor issues, they won't have near the effect on snowfall tonight. For instance, if we see less WAA, but colder mid-level temperatures, we will see higher snow ratios, but less overall moisture/forcing. However, if we see slightly warmer mid-level temperatures, we will see more moisture/forcing but lesser snow ratios. At this point, I'm leaning towards slightly higher mid-level temperatures, which could aid in heavier snow totals, even though snow ratios could be a bit lower [around 15:1 or 16:1]. Also, given the fact that clipper systems tend to over-perform on many occasions, I'm willing to bet on 3-4" of snow occurring in some areas.

After the snowfall begins to wane on Saturday, gusty winds behind the front will lead to more blowing and drifting snowfall, as well as falling temperatures. By the end of the day, temperatures will be below 10 degrees again, with lows around 0 Saturday night.

By Sunday, there is still some disagreement between models on precip. amount and heaviest snowfall placement, but at this point it appears that it will be a similar event to what is happening tonight, but perhaps with stronger dynamics and slightly more moisture. For this reason, I believe Sunday's event will be more along the lines of 2-4"/3-5" instead of 1-3"/2-4". This is especially the case if the mid-level instability that is expected can overspread parts of the area, causing mesoscale-banding. However, there is still some uncertainty, especially given the fact that snow-ratios will likely be lower than tonight [around 13:1 or 14:1]. Even so, gusty winds are still expected, leading to more blowing and drifting snowfall. Temperatures will fall throughout the night Sunday into the lower single-digits. Highs on Monday behind the cold front will barely make it above this low, with temperatures falling well below-zero Monday night. By Tuesday and Wednesday, temperatures could be even colder. Tuesday it doesn't look like the area will make it above 0 [some models are indicating highs around -5 to -10 below], with Tuesday-night lows around -10 to -15 [some models are indicating that temperatures could drop below -20, which isn't out of the realm of possibility]. By Wednesday and Thursday, temperatures begin warming up again, with only a slow moderation likely. Given model discrepancy at this point, it appears that the warmest temperatures will get by Thursday is about 19 degrees.

I'll have more updates later. 

Monday, January 13, 2014

The Myth of the Polar Vortex and the "Mega-storm".

This post isn't going to be so much of a forecast as it is going to be a clarifier, but I will add in some medium-long range forecast details about what I expect to occur across the region during the next few weeks.

With that being said, however, there seems to be this persistent "hype" going about the media over the past few weeks about the so-called "polar vortex". So many people have been "fooled" into believing that it should be something to be concerned about when it really isn't. So, I'm here to clarify what is meant when meteorologists and atmospheric scientists use the term "polar vortex".

Unlike what the media has made it seem to be, the "polar vortex" is not something that can be seen with the eyes. It is not a rare or unusual phenomena, and its certainly nothing to panic about either. The "polar vortex" is actually a semi-permanent feature of the Arctic region, which is occasionally displaced when periods of anomalous warming occurs over the poles [known as "blocking" in "weather slang"] and can then break-off and slide southward into the temperate regions. This is the reason why we occasionally see exceptionally strong blasts of Arctic air into the region. It is not because the polar vortex itself has actually moved into the area, but it originates from the polar vortex. In more "scientific" terms, the polar vortex is actually a climatological pattern of the Arctic which results in upper-level troughing and the formation of a cold-dome. As a result, a large cyclonic circulation develops, which contributes to the development of long-wave troughs across the temperate zones, and hence the formation of the main jet-stream pattern. It is not a rare occurrence, and its not something that can be seen, or something to be afraid of.

Secondly, I've been having people ask me all day if there's going to be a "big storm" coming soon. I can emphatically say that this is false as well. It IS true that we will be going into a pattern more conducive to winter-weather for the area, including the establishment of a mean long-wave trough across the East, which will lead to below-normal temperatures for the second-half of January. It IS true that at times, this pattern will become conducive to strong clipper-systems moving into the region, and the potential for a Colorado low to bring us some decent snowfall. HOWEVER, as of this point, there is no indication of any major storm hitting the area. Zilch. None. I don't know where these rumors began, but we have a very low chance of seeing another "big storm" this winter. We will definitely see several 4-6"+ events through February, but I think its going to be very difficult for the area to see another 10"+ storm like we had just last week. However, I will not rule out the potential, given how volatile this winter has been so far. I will keep you updated. For now, however, there is no major storm coming, and all I'm expecting is several clipper systems, and temperatures dropping into the 10's and 20's.

Friday, January 3, 2014

Major Update and Analysis.


After looking at the 12z data [and some of the 18z data], I will give you my latest thoughts on the system, as well as certain, specific details in the evolution of the system, and how I expect the system to impact us over the next several days.

Short Technical Discussion:

The 12z model suite came in rather well at a modest consensus among guidance. Nearly all guidance was tracking the storm-system from the lower Mississippi Valley and into Kentucky and South Central Ohio before rapidly deepening across the Northeast. There were still model differences, especially in the track and intensity of the system, but all in all it was nearly similar across the board. And because of this, I do think it is safe to conclude that parts of our area [N. Indiana and NW Ohio] will at least get clipped by the heaviest snow, if not rest in the axis of heaviest snowfall. Again, this is all dependent upon the actual development of the system. However, there is still evidence that the storm might shift paths ever so slightly and affect snowfall amounts. Today's 18z guidance [particularly the GFS and NAM] did not present such a "good" snowfall solution for us. In fact, the NAM trended much drier across the forecast area and moves the system out of the area much quicker than other guidance. For now, the NAM is seen as an outlier given its flat, progressive bias in amplified patterns [as evidenced by what happened with the last storm-system]. The bad news is that the GFS also followed suite, even though it kept the intensifying low and heavier precipitation back west [and we still got a decently heavy snow event]. At this point, I'm favoring the 12z guidance for two major reasons:

1.) The way the shortwave trough is amplifying currently, as well as short-range extrapolations of the shortwave indicate much more digging at the base of the trough AS WELL AS much more interaction of the primary shortwave [seen here over Montana and North Dakota] with a piece of the Polar Vortex farther north [which is ultimately going to be the factor which draws the intense Siberian air mass south into the United States behind the Arctic front]. All of this rules out the NAM solution as of now. We should be expecting a more amplified solution and it appears that models have not caught on quite yet [even the more amplified models]. On this point, the WPC and NWS IWX agree, and in this afternoon's AFD, the NWS did say that they were concerned that the entire storm-system could be stronger and farther northwest than currently predicted [as in the SREF solutions].

2.) The interaction of the strong clipper-system along the U.S./Canadian border currently and the cold-front which will be shifting through our area Saturday night will also allow a further west solution; the reason I say this is because of the fact that the cold front will rapidly slow down as the mean-flow above surface-frontal boundary becomes parallel to it. By this time, the shortwave will interact with the frontal boundary and produce another surface-trough, which, if the shortwave is oriented correctly, will rapidly develop into a 1004 MB low-pressure system by the time it reaches Central and Eastern Ohio. Due to the strong nature of the high-pressure system behind the front, a strong pressure gradient will also set-up. Regardless, I do not see this scenario reflected in the weaker guidance such as the 18z NAM, and hence why I do not believe it will come to fruition. However, better judgements can be made after the 00z guidance comes in tonight.

Now that I've cleared that up, I think we can quite confidently say that the 18z NAM [and possibly the 18z GFS] are both outliers. My own solution is in line with the ECMWF and CMC forecasts, although I believe a slight shift east or west is possible. A more substantial eastward shift is altogether unlikely but it is quite possible and not something to be dismissed at this time.




Now to the actual precipitation.

While snow-totals across the region will largely be dependent upon the track, speed and intensity of the low, another major factor which could affect snow-amounts is the moisture input into the area. Right now, we have too extremes/outliers in the guidance. On the one hand, the ensemble SREF mean is indicative of a very wet system over the area. Although it has a difficult time accurately printing out mean snow-totals that are realistic across the area, the amount of moisture that gets involved in the system [in the mean] is incredible and likely overdone. On the other-hand, we have the NAM and the high-res NAM which appear to be the "driest" solutions on the board. And the very reason why they are drier is for the very same reason that I described above; they do not amplify the shortwave aloft enough, and thus under-develops the surface-low, which in turn limits Gulf-return flow aloft. Even though moisture profiles will be less than ideal [mixing ratios only near 4 g/kg], I do believe we will see plentiful moisture from the Gulf of Mexico, and due to the anafrontal nature of the original wave, most of the precipitation will be behind the front [hence why we are seeing a major snowstorm].

Because of this, I believe QPF [Quantitative Precipitation Forecast] totals will exceed 0.5-0.6 inches across the entire area for the total event [Saturday night through Sunday evening], with localized higher amounts of 0.8-1 inches, especially along and southeast of the U.S. 24 corridor. Given that average snow-ratios will be around 16:1 or 17:1, snowfall totals should easily reach the 8-12" snowfall range especially along and southeast of the U.S. 24 corridor. However, if the cold-front does end up moving faster across the region and we see colder air, ratios could be as high as 20:1, which will enhance snowfall amounts.

Any other details regarding precipitation will have to be refined in now-casting and the use of mesoscale models, because right now it is extremely uncertain as to where heavier bands of snow will set up across the area, when and for how long. However, it is certainly possible that bands of 1"/hr could set up around the area and to our southeast, which could easily enhance snow totals.

NON-TECHNICAL DISCUSSION
In brief, here is what I expect from this winter storm across the area:

Snowfall totals will range from six inches in the northwest [especially in N. Central Indiana and SW Michigan] to as much as 12 inches along and southeast of the U.S. 24 corridor. However, this is subject to change [given what I discussed above], and especially if we see a stronger storm-system. If we see a weaker storm, snowfall amounts across the area will range from four inches in the NW to nearly eight inches in the east/southeast.

Blowing and drifting snow will be a major concern, especially after the snowfall ends as the storm "bombs" out to our east. However, as I discussed above, if we can get the storm to strengthen faster, we will likely see near blizzard conditions DURING the storm. Again, its very contingent upon a few seemingly minor details in the current upper-air analysis.

And because of this, we will have to also remain cautious about wind-chills, given that temperatures will fall down to about -11 Sunday-night after the storm passes through. Wind-chills with winds of 25 mph produces wind-chills of -30 to -40, which isn't pleasant for the human-body. Similar conditions will continue Monday into Tuesday and early Wednesday.

I will have more details tomorrow on this potentially crippling winter-storm.

**WINTER STORM UPDATE**

While I am still waiting on the rest of the 12z guidance to come out to get a full update, I think we have enough of a consensus this morning from the 00z guidance to have more confidence in the winter-storm solution. So I will release a brief update here and then another more detailed post later this afternoon detailing several potential factors in regards to the track of the system and its development.

First, several things need to be pointed out.

1.) Most, if not all of the 00z guidance came into agreement with the ECMWF [or at least close to it]. There are, however, still some disparity between the different tracks of the system which needs to be watched for the placement of the axis of heaviest snow.

2.) There is still large disagreement on final snow totals. While the global models seem "hell-bent" on producing 8-12" amounts [especially the GFS and ECMWF], the longer-range mesoscale models are showing much less snowfall [although the latest NAM was more bullish with snow amounts; however it hasn't been all that consistent]. This is largely due to the progressive nature of the storm on the NAM. However, I've already noticed some questionable features on the NAM's forecast that makes me doubt its weaker solution.

3.) Snow-ratios should begin around 11:1 on Saturday-night given the mini "heat-wave" that we will be seeing [temperatures in the upper 20's/lower 30's], with snow-ratios gradually increasing throughout the day Sunday as the Arctic front pushes through the area [possibly ratios of 16:1 or 17:1 during the heaviest snowfall]. This could enhance snow totals if we can see stronger banding and/or greater moisture transport into the system.

4.) Blowing and drifting snow will be a major concern, especially after the snow has ended. As the low bombs out over the NE and Southern Canada, winds should increase to the 20-25 mph range with higher gusts likely. This will lead to dangerous and nearly impassable roadways in the hours following the end of the storm. On top of that, temperatures will plummet into the -10's Sunday-night, which will prevent any melting of the snow on roadways. It will make it nearly impossible for snow-trucks to clear roads.

5.) Extreme cold will follow the winter-storm. Wind chills will likely drop into the -30's and -40's starting Sunday night and lasting through Tuesday, especially in the morning hours. Temperatures are not likely to make it above zero from Sunday-night through early Wednesday morning.

UPDATE: The NWS has issued a Winter-Storm Watch for the area, calling for 6-12" of snow areawide, with the potential for heavier snowfall along and  southeast of U.S. 24. 

Thursday, January 2, 2014

WINTER-STORM POTENTIAL UPDATE

Okay, we have a bit more information on the upcoming winter-storm this Sunday. But first, a brief summary of today's storm.

As originally anticipated several days ago, snow totals ranged from 6-10" across the region, with the heaviest snow amounts across lower Michigan due to the clipper system on Tuesday-Tuesday night. However, because of the fluffy nature of the snow, there will be a lot of blowing and drifting this afternoon. And this won't even be the worst of it; with the decoupling of the boundary-layer tonight and under clearing skies, it appears that many areas will see temperatures rapidly falling below-zero tonight. If light winds hold on longer, we could see wind-chills as low as -15 to -20, which approaches dangerous criteria.

However, for the weekend-storm, we have a different scenario. As of now, model consensus seems to indicate that most of the area, especially across the east and southeast [east and southeast of Fort Wayne that is], will see a significant snowfall event. While the exact track of the storm and its intensity is still in question, confidence is growing in a major snowstorm for the area, especially if the ECMWF and CMC verify. Given that the 12z GFS and the 12z NAM are outliers compared to most guidance, it appears that the forecast will favor the ECMWF and CMC solutions right now. And both models are currently indicating snowfall amounts in the 10-12" range, based off of 10:1 ratios. And if the storm develops as quickly as guidance is currently indicating, it appears that we may see reduced visibilities and near blizzard conditions. However, this is not set in stone yet, and there is still some model variability [hence why the NWS will not issue any advisories, watches or warnings until Friday night or Saturday for this event] and hence some uncertainty. There is still the question of phasing and storm-track, which will definitely affect how much snow we get from the system.

As of now, I do not really have an anticipated range for snow accumulations, as there is still too much uncertainty, but I would venture to guess that 8-12" accumulations are not out of the question, but I'm willing to bet that a safer guess is going to be around 4-7" [but likely a lot more if the stronger-storm scenario verifies].

HOWEVER, what we do have more confidence in is the record-breaking cold that will follow the storm. Temperatures are likely to reach their maximums on early Monday morning before dipping below zero, which means early morning temperatures in the lower single digits. IF the cold-front blasts through as currently predicted, temperatures late Monday afternoon will be below-zero with gusty winds and possible lake-effect. This will cause wind-chills around -25 [thus the possibility of wind-chill warnings]. However, the coldest weather is expected Monday-night through Tuesday-night. High temperatures on Tuesday are expected to reach a maximum around -5 to -8 [according to WPC forecasted highs]. Lows Monday-night will dip down to about -16 to -19 across the area. By Wednesday, however, we should see temperatures rebounding to the upper single-digits [still well-below normal] and lower teens before another clipper-system moves through with the potential for more snowfall.

I will have more updates on this potentially significant event tomorrow morning.

***WINTER WEATHER UPDATE***


Here's a brief summary of what I expect to occur over the next few hours for the area:

1.) Light to moderate snow will continue into the late morning, possibly early-afternoon, before tapering off. Some periods of heavier snow and reduced visibilities are possible, especially as the surface-low moves to our east, and causes some heavier bands from our south to move northward. However, this period of heavier snow will be brief as the storm transfers to the coast.

2.) Snow-ratios are likely to increase as the day progresses, and especially as the snow becomes lighter later this morning. This will allow for a snow that can accumulate more than the small crystals that we saw last night and into this morning. At the same time, temperatures will likely be dropping as frigid Arctic-air sags in from the north. This in combination with gusty winds will cause blowing and drifting snow through the afternoon and evening hours. The cold temperatures will make it rather difficult for roads to melt as well, leading to nasty road conditions [even on the main highways].

3.) Additional snow accumulations of 2-3" are possible today, especially along and southeast of the U.S. 24 corridor. This will lead to storm-total accumulations of 6-10" area-wide [36-hour accumulations from Tuesday-night and Wednesday included].



Monday, December 30, 2013

POTENTIAL WINTER STORM

***POTENTIAL WINTER-STORM***

Since the holidays are almost over, I'll be making more weather-related posts here during the next few weeks. I do not expect to be absent and I should be able to provide you with the most up-to-date weather forecasts now. 

But for now, it appears that we have a potential winter-storm on our hands for the mid-week period. Right now, models have come to a general consensus on the formation and track of a low-pressure system from S. Colorado through the Southern Plains and into S. Ohio from Wednesday through Thursday. This same primary low will then weaken as an intense secondary-low develops off of the East Coast. Overall, depending upon the track of the storm, the intensity of the initial shortwave and the timing of secondary development, we could be seeing a major winter-storm, stretching from Iowa and Illinois through N. Indiana and Ohio and into the Northeast/New England. Due to the bombing nature of the secondary-low [due to CISK and its interaction with the baroclinic zone generated by the Gulf stream], an intense winter-storm is expected for areas farther east.

Several factors need to be monitored for snow accumulations with this storm-system.

1.) Moisture- Generally, Colorado-lows are not moisture-starved and have ample-access to Gulf-moisture. At this time, moisture does not appear to be a concern that will hamper snow accumulations.

2.) Snow-ratios/depth of cold air- Unlike the last winter storm [December 14th], this winter-storm is likely to bring much higher ratios. 850 MB temps during the height of the storm are only likely to be around -7 to -9 C and surface temperatures are likely to be in the upper-teens. This in combination with a deep DGZ layer [Dendritic Growth Zone] will likely produce snow-ratios on the order of 15:1 to as much as 18:1. However, this needs to be ironed out over the next few days, as it is notoriously difficult for models to get thermal profiles correct even one day out. However, in general, it is highly likely that snow-ratios will be higher for this event.

3.) Intensity/track of the primary-low: This is likely to be the trickiest detail to forecast as of now, and it will likely be the most significant factor in determining who receives the most snow from this system.

At this point, the NWS and WPC are both leaning towards the ECMWF solution, which shows a stronger primary low tracking into S. Ohio as a highly amplified short-wave induces cyclogenesis. The 00z run late last night and early this morning continued the trend of a more amplified primary short-wave, which leads me to believe that the primary low will be stronger. However, given that the shortwave appears to be more amplified, the primary-low is likely to track farther south than what the GFS and other models are currently predicting. IF this is the case, then I can definitely see higher snowfall amounts for the area. Because at this point, the GFS and long-range NAM both have the low-pressure system tracking farther north and bringing the heavier snow totals to areas in S. and Central Michigan.

Right now, the ECMWF appears to have a better handle on the system, but this needs to be watched. If the ECMWF solution verifies, its likely that most of us see 4-8"+, with the heavier snow totals falling north of U.S. 24. And because of this, the NWS has issued a Special Weather Statement for the entire area, detailing the potential for a winter-storm. I will continue to monitor this event over the next few days.


I will have a map out sometime this week [likely before Wednesday].

Monday, December 16, 2013

Tonight's Winter Weather Event and Winter-Storm Potential [for 12/20-22]

After this past weekend's massive snow-storm across the area, with most areas recording in between 5-9" of snow for the total event, we are still expecting an active winter-weather pattern. Unlike last-winter, as most people recall did not feature many significant winter-weather events until early March, this year, the weather-pattern seems loaded with winter-weather events and fresh Arctic air for the area. And it doesn't appear that the end is in sight anytime before Christmas.

There are two major things that bear mentioning right now. First, the Alberta Clipper, which could dump a quick 2-3"+ of snow across much of the area [mainly north and east of U.S. 30]. Secondly, a potentially major winter-storm for the upcoming weekend, which will occur in two-segments.

Tonight's Alberta Clipper

Although this will not likely be a major-event, I do expect that this clipper system will be a bit of a nuisance for the region, especially in exasperating already icy-road conditions, and making for ideal blowing snow Tuesday morning and afternoon. As you can see [below] from radar imagery, the system is not all that impressive. However, this system has unusually high amounts of moisture for a clipper-system, as well as strong omega in an already saturated DGZ [Dendritic Growth Zone; the most efficient layer for snow-crystal formation processes] layer, allowing for a brief burst of moderate-heavy snow, putting down 1-3" of snow across the area.





Not only this, but there are certain other mesoscale processes that could come into play to enhance overall snow-totals tonight, including, but not limited to mesoscale-banding [frontogenesis], higher mid-level lapse rates, and possible slowing of the system itself. All of these factors will go into producing a quick two or three inches of snow for parts of the area [most of the area will likely see about an inch of snow].

However, this is not the only clipper-system that will be moving through in the next 48-hours. By Tuesday morning, another clipper-system will be on its way into the area, and produce a quick burst of moderate snow for the area. This time, its possible that the clipper tracks farther south and thus produces some slightly "heavier" snow totals than originally anticipated. However, at this time, it appears that snow will be around an inch for tomorrow's event. After the clipper passes through, it appears that windy conditions will set-up across the area, leading to significant blowing and drifting snow. This will definitely cause hazardous travel on Tuesday night and Wednesday, and something that needs to be monitored.

Both of these events will put one to as much as four or five inches of new snow on top of an already widespread snow-pack of 4-8". This will continue to allow temperatures to be colder than usual, and will likely temper the coming warm-up this week and weekend [instead of temperatures in the 50's, its likely that temperatures only reach the upper 30's and lower 40's.]. However, how much snow we see before the warm-up comes will also determine how the next storm-system impacts the area.

Major Weekend Storm-System At this time, there is little to be certain of in regards to what will happen with the storm-system that will impact the area by the end of the week. At this point, all we can say is that the area will be impacted by a significant winter-storm, whether it be heavy rain [and thus cause flooding], heavy icing [a major ice-storm is also possible], and/or a very heavy snow-storm [some models are indicating 1-2 feet of snow possible]. At this point, all of these solutions will be on the table, and will be determined by the strength of an Arctic high across the Northern Plains, as well as the depth of the snow-pack across the area after the Thursday-Friday event ends.

Right now, I am entirely uncertain of what is likely to occur. Each model has their own solution at this point, and although there are not significant differences between runs, there are just enough differences that lead to drastically different solutions. For example [see below], the 12z ECMWF dumps over 2 feet of snow across parts of the area through Sunday. The ECMWF pushes the baroclinic boundary south of the area after the Thursday-Friday event, while at the same time develops an intense low-pressure system in the lower Mississippi Valley. At the onset of the next storm-system, the ECMWF predicts a changeover from ice/rain to heavy snow as the Arctic front pushes southward. While I believe this solution is plausible, there isn't enough certainty to say that its the most likely solution. The GFS brings the area a weaker system, but slightly warmer, with the potential for anything from moderate-snow to heavy rain/ice. On the warm-side of the guidance, the 12z CMC/GGEM brings the area a significantly heavy-rain event while bringing a massive snow-storm to the Great Lakes and Southern Canada.



At this point, I will rule out the GFS solution, because it does appear that whatever system does develop, it will be a significant one, and likely stronger than what the GFS was depicting. The NWS is currently keeping the forecast as a chance of snow [or rain/snow] for the area until details can be hammered down. As for my own opinion, I do believe the current weather pattern does support a possible system like the ECMWF has. The pattern is currently similar to the pattern just before the Groundhog Day blizzard, which we know was one of the worst Midwestern blizzards since the Blizzard of 1999.

Wednesday, December 11, 2013

UPDATE ON WINTER-STORM POTENTIAL

This won't be a very big update, as I have other things to look at before making any more detailed forecasts, but I do want to get the word out about this winter-storm that will likely affect the region Friday night through Saturday.

First, the main points of what I expect to happen [and then the gritty "details"].

1.) This will not likely be a "blockbuster-event" like the Groundhog Day blizzard of 2011 was. I am not expecting crippling snowfall and impassable roadways or anything like that. However, this storm will be rather significant for the area, causing quite a few travel delays and accidents. The "good" news is that this storm will be hitting on a weekend, and thus will not disrupt schools or cause any major travel disruptions [especially considering that the snow is likely to begin falling AFTER rush-hour on Friday].

2.) Secondly, I am not expecting any other precipitation type besides snow; thermal profiles throughout the event will remain below-freezing, with max. saturation likely residing in the DGZ [Dendritic Growth Zone], or at least in the lower-half. This will allow for efficient ice-crystal development processes, and thus we shouldn't have much trouble with developing snow over the area Friday-night. The only caveat will be the potential for dry-air at the onset, which will lead to evaporational-cooling.

3.) Lastly, it looks as if snow-totals will be in the 4-6 inch range overall; I know many area meteorologists are going conservative right [many are placing accumulation amounts around 2-4" or 2-5"], but I'm going to go right out and say what the model consensus has. And even this on the low-side of much of the guidance today. Models like the ECMWF, the CMC, and NAM all have a good 5-8 inches of snow for the area, unlike the GFS, which gave us about 3-6 inches of snow. However, I'm not willing to bet on such high snow totals yet, due to problems with actual precipitation production and moisture transport. As for timing, expect snow to begin around 9-11 p.m. Friday night, and last through at least the early afternoon hours Saturday; 18+ hours of moderate snowfall will likely contribute to decent snow totals area-wide.

Now for the "gritty" details.

One of my main concerns as of this point is the potential for mesoscale-snow banding, and frontogenetical-enforcement. When I say "frontogenetical-enforcement", I'm mainly referring to the tightening of the horizontal temperature gradient [in other words, the temperature contrast from one place to another increases, leading to upward vertical motion on a slanted-scale].

In regards to mesoscale-banding, this could potentially lead to the enhancement of snowfall amounts. In fact, the latest 18z NAM run is pointing towards the formation of heavy-snow bands across NW Ohio and N. Indiana late Friday night before the main event gets underway; if this occurs, and the lower-levels saturate quickly enough, it is quite possible that we pick up a quick 2-3 inches of snow in a short-period of time. However, considering that the NAM seems to be having problems with the timing of drier pockets of air [and thus, lulls in snowfall during the overnight hours], it may just be a fluke run. I'll have to monitor the 00z NAM [which is coming out currently] for further trends. However, it is likely that we do see some kind of mesoscale-banding with this event, which will mainly enhance snow totals along and southeast of U.S. 24.

Not only this, but strong, jet-streak circulations will likely enhance the development of moderate-heavy snow bands. The 18z NAM also showed that a small, macro-scale jet over C. Indiana will "couple" with a jet-streak over Canada, producing intense upward vertical motion in between [this happens due to the fact that strong upward motion usually occurs in the left-exit region and the right-entrance region of jet-streaks, and when these are interposed on each other, they enhance dynamics greatly]. If this were to occur, we would expect the development of heavier periods of snow during the day Saturday or in the early morning hours. This will be yet another factor in my snowfall forecast.

But for now, I'm sticking with the 3-5"/4-6" forecast, as it appears to be reasonable at this time.

Saturday, November 23, 2013

Short-Term Forecast

County warning map for today from the NWS

After a mostly clear night across the area, temperatures have dropped into the mid-20's for most of the area. Even so, mostly clear conditions this morning should begin to give way to partly to mostly cloudy skies by the afternoon as the cold front passes through the area in the vicinity of an upper-level vorticity lobe [which, if it "deepens" correctly, could provide slightly more forcing for snow showers along and behind the front later this afternoon and evening]. Cold air advection behind the front will be strong enough to keep temperatures from rising much past the lower 30's and upper 20's today, with temperatures likely in the low to mid 20's by the late afternoon and evening. Behind the front, we will see a brief period of snow showers, which could produce a brief accumulation of up to a half inch or an inch in some areas, but generally, accumulations should range between a dusting and an inch. Later tonight, extremely large delta-T's across Lake Michigan [between the surface and 850 MB, as well as the surface and 700 MB] will produce several convective snow-bands across the main lake effect areas; this time in North-Central Indiana, and SW. Michigan, which is why the NWS has issued a Lake Effect Snow Watch with the possibility of 3-7 inches of snow or more in these areas. Farther east and south, although we are not likely to see much in the way of lake-effect snow, we could still see periods of snow showers in the overnight hours, possibly with some additional light accumulations, if anything.

However, by Sunday, snow showers should be tapering off, and giving way to a bitterly cold day [bitterly cold by November's standards], with highs only reaching the mid-20's across the area. With warm-air advection and rising upper-level heights, expect conditions to begin warming by Monday, with highs back into the low-mid 30's. On Tuesday and Wednesday, yet another system will be approaching the area [which will influence the development of a possibly strong "coastal-runner", or a low that will track along the East Coast and produce a heavy snowstorm in the Interior Northeast], allowing for the possibility of snowfall and cloud-cover once again. Although models are still in disagreement over whether we will see any precipitation, I believe moisture profiles and dynamics will be strong enough to produce at least light snow across the area, especially Tuesday into Tuesday night. However, I will continue to monitor this system. By Thanksgiving, temperatures will be dropping back into the upper 20's and lower 30's for highs, making it one of the colder Thanksgiving days that we've seen since perhaps 2007. However, by next weekend, temperatures should be rebounding once again as another flattening ridge builds into the region. BUT, this "warm-up" [into the upper 30's and lower 40's at the warmest] will not last long, as a series of storm-systems will be approaching from the North American West Coast, which will cause another cold-front to dive into the region by the end of the 10-day period. But like I have said before, things are still uncertain on what exactly will happen, so I will keep you updated.