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.

Friday, November 22, 2013

Current Wx Analysis; Short Term Forecast

After yesterday's, and this morning's chilly, rainy weather, conditions are finally beginning to change, with clearing cloud-cover and much colder conditions on the way. The cold-frontal passage today will cause temperatures to drop into the upper 20's tonight, with a secondary cold front passing through tomorrow which should drop temperatures even further. By Sunday, high temperatures will likely not even breach 25 across most of the area, with only a few places west of the area reaching the upper 20's. Even so, some lake-effect snow showers will also reach parts of the area from Lake Michigan, with the possibility of a few brief flurries in the afternoon Saturday and Saturday night. For next week, below-normal temperatures and dry conditions are expected for the entire week. In fact, temperatures are not even expected to exceed 36 this week, quite possibly making it one of the coldest Thanksgiving weeks that we've seen in a while.

At the same time, the weather pattern over the next few weeks does bring up some concern for the overall winter pattern; with a generally normal to below normal pattern for most of November, and the most recent examples of cold air flooding southward from Canada, I believe that this will be a foretaste of what is to come. Although I expect December to be a "roller-coaster" ride overall [possibly warmer than normal in the middle of the month when storm activity revamps], I believe that we will see a fairly wintry month compared to the last two winter seasons. It appears that the area will see at least a few clipper systems during the month, with the possibility of one or two major Ohio Valley storms [as evidenced from the major storm systems we've seen this fall in the Midwest]. This will allow for at least a normal December in regards to snowfall, precipitation and temperatures. As for the rest of the winter, it remains to be seen what will happen; at this time, it appears that December does appear to give us a gradual shift into winter [unless something drastic happens on model forecasts which convinces me that there will be a pattern-shift into a majorly cold winter season].

**The Problem With Modern-Forecasting**

This was originally posted in a weather forum that I am, so please excuse specific references. Thanks. :)

**The Problem With Modern-Forecasting**

I don't know if this is a subject that will interest many of you, but recently, it has for me. I decided to back and look through my introductory forecasting books during the past few days, and I found some really disturbing things that I find lacking in today's meteorological world. Albeit I am not a professional in the least, and could barely be considered an amateur forecaster.

One thing that I find really great about many in this group is that we don't have consistent "modelology". Most people here are aware that models do not constitute the completeness of what it means to forecast; in fact, if anything, models are just guides; not forecasts. The best that a model can do is SIMULATE how the assumed variables will change through a specific period of time [and remember, simulations can be FAR from reality], not forecast. There is a big difference. However, I still feel as if something is missing.

With the many advances in science and technology over the past decade or so, society has really begun to advance at an accelerating rate; however, I believe we are finally beginning to realize the worst fears of the dystopian sci-fi novels; progress ISN'T always good. And I believe something similar could be said of meteorology. Progress in model and computer development has progressed so much that it has almost removed the human-element from forecasting. At some NWS offices, they are now being told to go with the 24-hour MOS data instead of questioning it; at other offices, model-forecasts are taken at face value for medium-range forecasts. Among many meteorologists, looking at short-range model forecasts for mesoscale events has replaced real analysis [even though it would be almost always advisable to ignore any mesoscale-model within 12-hours of the event, which is the time period in which human-forecast skill exponentially increases over the short-term model forecast] of surface-maps and satellite imagery. Essentially, a lot of modern-meteorology has become an "interpret and regurgitate" mentality; i.e. "we can't have any possible idea of what the next seven-days will do, therefore, regurgitate what the medium-range model showed and hope to apologize when the system changes". I will be the first to admit that I have done this; and I know many of us have done it on here. But don't you realize that the human-element is completely gone? Even when we look at various models and compare various features, and then take a collective "total" so to speak of each forecast [or decide whether or not to throw out outliers], do not ensembles already do this? Isn't there a component of humanity that is needed here? I mean, we are the only self-aware beings on this planet [as far as we know], and we are the only organisms in this solar system attempting to understand our universe, shouldn't the human still be playing the higher part that a computer doesn't and can't ever play? And that directs me to the article I was going to post: http://www.flame.org/~cdoswell/forecasting/human_role/future_forecasters.html I urge anyone interested to read this article, because he first addresses issues in the NWS itself, and then goes on to critique private forecasting use of models. He then goes on to argue why human forecasters will always be essential.

What we are doing now is not forecasting; whether or not we have individuals who can forecast in an excellent way [which we do; I know many who can], its something that is affecting all meteorologists. The surge in technological capabilities has lead to an even greater reliance on computers in themselves to do the forecasting for us, and essentially, we leave without any understanding of what's going on.

This brings up another article that I wanted to post; a speech by Dr. Len Snellman on this problem from National Weather Digest in 1991. http://www.nwas.org/members/snellman.php

Of course, I think there are other problems with meteorology today, including observational limitations, knowledge of our atmosphere, technology, etc. But I also think that this is a hidden problem that we sometimes ignore. Not to say that all meteorologists do this [by no means!], its just that many meteorologists fall into this trap.

What I think is necessary for forecasting is this:

I mean, I think we do have a real problem; because the forecast process should be sort-of like any scientist. We must apply the scientific method in a way that is unique to meteorology. I wouldn't even doubt that using a practical way from mechanics or other field would work. What is needed, however, is one that is structured to include human reasoning, cognitive abilities and intuition into the forecast, rather than just interpreting model-charts and adding some insight every now and then.

Since the scientific method [in general] begins with a question, I believe that the forecasting process should begin with a question of "what is going on". In other words, all forecasts should begin with analysis. Analyzing includes looking at the atmosphere, whether through surface observations, satellite-imagery, radar, and even processed-data fields from super short-range models.

In the next step of the scientific method, we develop a possible answer to our problem/solution. This would be analogous to diagnosis in meteorology. We must first synthesize our analysis into something that can lead to other questions and/or be a possible explanation for what is going on through what we observed in the analysis. If we haven't done a sufficient analysis, we can't do a sufficient diagnosis. We must be able to explain what we see on the weather-map in terms of our own experience, knowledge, conceptual models, etc. This will be more difficult for the amateur with less atmospheric knowledge than the professional with experience and much more atmospheric knowledge.

In the next-step of the scientific method, a scientist will develop a test/experiment for the hypothesis. This is essentially a continued step of what is required of diagnosis in meteorology. We continually monitor what we are analyzing, and now we synthesize model-output with the observations to try to develop a coherent picture of what exactly is going on; since the atmosphere is a continuous fluid and in constant motion, we only get a brief snapshot of what is going on through our analysis. That is why diagnosis is necessary, to get the "dT/dt" [change in the temperature with respect to time] part of analyzing a surface temperature map or the "dV/dt" [change in the wind vector with respect to time] part of analyzing surface observations, and thus we can then at least approximate the change that will occur in a specific period of time. That is essentially what forecasting is all about; predicting what "x" is going to be by estimating the current "dx/dt" [with "x" standing for any scalar variable, or a vector].

This is going to be a lot harder with longer-range forecasts; especially after the 1-4 day period. This is when we have to rely upon ensemble and operational model forecasts for determining what will happen. But that doesn't give us the right to rely completely on models; that's why we have global satellite imagery! That's why we have conceptual models and correlations/experience! I believe that is good to use as well with our model-data. But like I said, in this period, I think its unavoidable that we use models if we are planning on forecasting for the 6+ day time-frame.

Of course, I don't have anything against models, and I would definitely have to say that without models, modern-forecasting would not have made near the advances that we have made. But on the other hand, misuse of model forecasts doesn't make us better forecasters.

Friday, November 8, 2013

A Quick Update

First of all, I would like to say that once again, I am incredibly sorry for not posting lately; I've been busy with school, and looking at colleges [just FYI, I am going into meteorology for my undergraduate studies], and I just haven't found the time to post on here [apart from my Facebook "debates"]. I will attempt to be more reliable and consistent on posting over the next few weeks and months [especially considering that we have an interesting weather pattern that could begin our winter season this year]. So, if I do not post for several weeks, its probably because I'm busy with school; don't worry. Just follow me on Twitter or on NWOSPC's Facebook page, where I post updates at least once a week. I will also be revising my forecast technique, so that I can write posts that are more understandable to the general public, so as to increase communication to those who follow what I write. Hopefully this will improve the amount of people following this blog of mine.

Secondly, I would like to briefly comment on the weather pattern; it appears that we will see a brief "taste" of winter [dare I say] for most of next week; a major Arctic front is expected to dive down from the Eastern Canadian Prairies, and right into the Great Lakes region, with brisk, gusty north winds causing temperatures to drop rapidly on Monday and Tuesday; in fact, high temperatures should struggle to make it above 32 on Wednesday, and possibly Thursday if the cold air mass decides to stick around for a bit longer. Other than that, we have the slight possibility of lake effect snow showers, and thus the possibility for a brief dusting of snow on Tuesday and Wednesday. After Wednesday, temperatures will begin to moderate into the upper 30's and lower 40's, with temperatures likely returning to near normal by the weekend. The pattern thereafter appears to be warming up a lot for this time of year, with the return to a zonal, progressive pattern, and repeated waves of warmer Pacific air into the region. However, it seems that a *real* pattern change will occur either at the very end of November, and/or early-mid December, which could give us a very decent introduction to winter.

Finally, the winter pattern looks rather conducive to a volatile pattern this year; especially in regards to temperatures. As for precipitation, I expect more than normal precipitation, with a higher frequency of storm systems through the Ohio Valley, leading to an increased chance for wintry precipitation and snow. However, there will be varying periods of warmth and cold during the winter [much more than usual], which would in fact allow for periods of rain and flooding as well. Overall, I expect this winter to end-up near normal temperature wise for the area, with above-normal precipitation, and most likely above-normal snowfall. My confidence level? I'm at best 20% confident on this; the analogues and other data is not at all clear as to what exactly is going on; and once again, there is no real parallel with any other year. However, I will continue to monitor what is going on, and I will continue giving brief updates on what I expect.

Saturday, October 12, 2013

Subtle Weather Gives Way to Possible Pattern Shift

After a week of nice, and somewhat chilly weather following last week's massive storm system, which dropped literally multiple feet of snow across South Dakota, brought heavy rains to the Midwest and Ohio Valley, and tornadoes to Iowa, Nebraska and Missouri, we are now beginning to anticipate the next big pattern shift in our current weather pattern, which could have some foreboding signs for what awaits us this winter.

However, let's first begin with a brief analysis of the current weather.

Right now, we have a slowing and weakening cold front approaching the area from the Central Plains, the left-overs of a rapidly strengthening storm in the lee of the Rockies earlier this week. This cold front is driving an area of showers and thunderstorms from the Gulf coast, upwards into the middle Mississippi Valley. Very little shower and thunderstorm activity is occurring farther north in the Midwest, but a few showers and thunderstorms are expected to develop as afternoon instability increases and moisture transport increases in a very thin region ahead of the cold front. Even so, I would not expect much rain at all.



Current 500 MB map of the United States
After the cold front sweeps through, expect a gradual decrease in the mean temperature over the next three or four days. By mid-week, models are in general agreement that a series of split-wave troughs will creep into the country, and along with them, a few weak surface systems which would bring back the chance for showers and light rain. Even with these systems, I do not expect any kind of significantly warm air along with it. Temperatures will remain near normal in the mid-60's from about Monday through Wednesday. Behind these systems, temperatures will gradually drop, with highs by the end of the week only in the mid to upper 50's, a few degrees below average for this time of year.




After about 168 hours out, it is rather uncertain about what will happen. Models diverge here on the speed of a larger trough that will drop into the Midwest and eventually the East by the weekend. If the ECMWF is correct, the main trough will remain slower, with a series of smaller troughs bringing somewhat colder air. Finally, once the main trough begins to move, it will allow for the first wave of cold air of the season, with average temperatures likely 15-20 degrees below normal [meaning 40-45 here] by the middle of next week. As of right now, this is NOT set in stone, but remains a definite possibility.

Saturday, October 5, 2013

Significant Storm System: Blizzard, severe weather AND heavy rain?

If you haven't heard already, the storm system that has been predicted on the models since last Sunday and Monday has finally consummated, and occluded in the Midwest. It is currently weakening very slowly as we speak. But even so, it packed a pretty significant punch to the Midwest.

Just to recap the last few days of weather from this storm system:

1.) It produced feet of snow and impassable travel conditions Thursday night in parts of the Rocky mountains.

2.) It strengthened further Friday morning into the afternoon, producing high winds, extremely heavy snowfall, and cold air across South Dakota and Nebraska. Snow totals have exceeded 45 inches in some areas, with the vast majority of the region receiving well over a foot of snow. The heavy, wet nature of the snow has caused a lot of tree damage and quite a few power-outages.

3.) On the NW side of the storm, within the blizzard, high winds became so strong that it broke records across South Dakota. For instance, Rapid City, SD observed wind speeds exceeding 70 MPH during the highest part of the storm! This caused widespread whiteout conditions within the heavy snow-bands, as well as causing interstate highways to be nearly impassable.

4.) In the warm-sector, heavy rain, flash-flooding and severe weather has been prevalent from Iowa and Missouri into the upper Ohio Valley. Yesterday afternoon, parts of NW Ohio recorded several inches of rain due to training thunderstorms, and most areas saw at least a period of heavy rain. In Iowa and Missouri, large, violent tornadoes destroyed several towns and caused many injuries.

5.) The storm system is still expected to produce very heavy rain across a large part of the Midwest, even with the storm system weakening. This is because of its interaction with the moisture plume associated with Karen, and the fact that it is slowing down significantly.

Take a look at the latest visible satellite imagery:


Notice the spiral band shape of the entire cyclone. Clearly, this indicates that the entire system has already occluded, and is beginning to weaken. Also notice the prevalence of convection on the eastern flank. What this means is that we should see a strong increase in thunderstorm activity over the next hours, and days perhaps if computer models are right.


The strong, closed-low in the Midwest will continue to propagate slowly eastward, drawing rich, Gulf moisture from the south, and causing repeated rounds of showers and thunderstorms. Today, expect showers and thunderstorms to rapidly build-up due to the marginally unstable and humid air mass in place. These storms will move rather slowly, allowing for the possibility of heavy rains before the main events comes under way.

By later this weekend, expect the showers and thunderstorms to organize into more organized structures, and allowing for the possibility of repeated waves of heavy rain.  It will then become possible that we see several inches of rain through Monday.

Monday, September 30, 2013

WINTER OUTLOOK COMING IN MID-LATE OCTOBER

I'm currently planning on releasing my preliminary winter-outlook for the season towards the end of October, or possibly early-mid November. It will all depend upon how certain I am of the winter forecast. 

Storm System Potential: Model Consensus

After many consecutive runs of indicating some kind of "major" storm system later this week, models have finally reached general agreement on the track of the storm system itself. Other issues such as intensity, precipitation, and thunderstorms still need to be sorted out, but over all, we are reaching a model consensus on when and where this storm will form. The timing issues that need to be sorted out are related to the mesoscale movement of the cold front into the area, which will be discussed on Tuesday and Wednesday.

And now, on to the model run-down.

12z GFS takes a shift west and south with Saturday's system, while at the same time weakening its overall amplitude and anomalous structure [instead of having a 540-546 DM core at 500 MB, it has a 552-558 DM core]. It will be some time before the GFS quits shifting the intensity and track of the system, but I think I can get a general track and intensity of the system.




The storm will likely track from Western Kansas and Eastern Colorado into Eastern Minnesota and NW Wisconsin. From both the latest runs of the GFS and the ECMWF, it appears the storm will have a maximum strength at occlusion near 1000-996 MB [if the wave is as amplified as currently forecast; right now, there are only moderate differences on the issue of amplitude; all that needs to be watched now is differences in run to run consistency] in the Western Great Lakes region before translating eastward across the Great Lakes and into Ontario. 



I'll keep watching this, especially on WV imagery, as that will help determine how well the models are currently handling the wave.



More details coming later on this potential storm system.

Sunday, September 29, 2013

POTENTIAL STORM SYSTEM LATER THIS WEEK AND WEEKEND

 While other people are going gung-ho on winter outlooks.. I decided I would post something on the upcoming storm system.

Take a look at the 12z GFS and 12z ECMWF: They are coming into agreement on a rather large trough pivoting into the Midwest and amplifying by late this week and early weekend. A strong cold front will plow through the Midwest [regardless of how amplified the surface reflection becomes], causing sharp temperature drops across the front. This could quite possibly be the first major storm system of the season if everything pans out correctly. So far, the strength of the upper level wave and the surface low has been increasing between runs, so I wouldn't doubt that we see at least a slight similar trend to continue. Even without an amplified surface trough, both models are still predicting a strong cold front to move through the Midwest and eventually the East.
The key to predicting this system will most likely be dependent upon which model is over-developing/under-developing the system. At this time, I would say that a consensus of both the 12z GFS and 12z ECMWF with some uncertainty is our best bet. I think we should keep an eye on this system.
12z GFS 850 TEMP map
12z GFS 500 REL. VORTICITY



12z ECMWF


Saturday, September 28, 2013

WX Analysis


***CURRENT WX ANALYSIS***

Even though the weather over the next few days won't necessarily be "exciting", I'm still going to be watching out for the potential of scattered to numerous showers and thunderstorms during the day Sunday, due to the influence of a strong and amplified short-wave trough.

A number of factors will be in play during this event, including but not limited to:

High moisture content in the atmosphere [PWATs will approach 1.9 IN, which is about the 99th percentile for late September.].

A strong, driving cold front, with strong temperature advection behind it [even though the temperature difference behind the cold front will only drop about 10-12 degrees or so].

Weak-moderate upper level dynamics and jet core circulations. This will all be dependent upon the eventual track of the short-wave trough, as well as how quickly the storm system de-amplifies. [See image below].

Weak mid-level instability [which will ultimately lead to the possibility of thunder and thunderstorms].

Because of the weaker levels of instability, I do not expect to see much in the way of thunderstorm activity, although it does remain to be a possibility.

As for the upcoming pattern, some very significant changes could possibly occur, and it will all be dependent upon the movement of the incredible Alaskan vortex [which can be seen on the image below]. If the Alaskan vortex continues to shift eastward and retains its shape, we have a decent chance at seeing a highly amplified pattern. If the Alaskan vortex only breaks down into a series of smaller waves, we will certainly see a more *active* pattern, but it will flatten out the pattern into a more zonal, and definitely less active pattern eventually. Considering the model variability on this issue, it remains to be seen what exactly will happen. Continue to follow my page for further details in upcoming days.