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Archive for February 2013

28
Feb

February 28-March 2, 2009 Upper Low Snowstorm

A moderately strong upper low developed in the northern Rockies in late February of 2009 and began to drop southward through the Plains.  The upper features that drove this system were a building western Ridge.  Antecendant conditions were extremely wet all across the interior Southeast for several days, with minor flooding throughout Alabama, Georgia and the Carolinas where several inches of rain fell for a few days right up to the point where the upper low came through and switched the rain to snow almost instantly.

march_2009_nesisAccums

Despite a soaked ground, the snow accumulated quickly, especially for areas just north and west of the Upper Low track, where the isentropic lift  was maximized via a trowal signature and thundersnow.  As the upper low pivoted from Memphis through the Deep South, snow began to increase rapidly as the low aloft began to take on an increasingly negative tilt at 500mb.  By the time the upper low was at it’s maximum strength in central Alabama to western Georgia, the low was already pumping out 1″ per hour snow rates and thundersnow and aloft the closed low was nearly 3 contours cutoff.  This location, trajectory and orientation of the trough was placed exquisitely to pull in copious moisture to the wrapping up system as it barrelled through Georgia, the Carolinas and eventually up the Eastern Seaboard.  Precipitable waters (PW) was very much above normal along the entire East Coast.

Here’s a look at the Upper Levels as the system came into the Rockies and began to dive and strengthen through the Southeast.

Feb28_2009_00z

Feb28_2009_18z

March01_2009_00z

March01_2009_12z

March01_2009_21z

March02_2009_00z

March02_2009_12z

March02_2009_21z

As the upper level low reached an inflection point upon entering Georgia, the system finally opened up but the snow rates began to increase on the northwest shield of the precipitation band, leading to conditions right for thundersnow. Frequently when systems in early Spring begin to turn negative tilt (especially cold upper lows), there is enough instability that can be created on the northwest flank of the circulation in the lee of the Southern Appalachians, as has been shown with several upper lows taking that path.

SPCmesoscalemapthunder

There was heavy snow recorded with several sites on the northern and northwest shield of the Upper low as it traversed the South and East.  The Memphis region was hit with some 14″ around Crockett County in the northern and eastern sububurbs with over a foot falling as well in northeast Arkansas as the low reached it’s first inflection point (bend or changing directions). A maximum of 16″ of heavy wet snow fell just east of Memphis.

March01_Feb28_2009_MEMsnow

 

As the system aloft took on neutral tilt, it slowed down and during the middle of the day much of Central Alabama switched from rain to snow under surface temperatures just barely conducive to support snow reaching the surface. Yet, major accumulations occurred deep in the heart of the South.  Had this event been timed differently for Georgia and Alabama, accumulations would  have been significantly more, as the snow was continuously melting from underneath. Yet the rate of snowfall (sometimes 2″ per hour) still allowed significant accumulations during the middle and late afternoon in Georgia and Alabama.

March01_2009_BHMsnowmap2

 

As the system crossed central Georgia, the snowrates increased and thanks to the time of snowfall, the actual accumulations began to increase dramatically around Athens and points northeastward.  The Upper Low was now beginning to turn to the northeast and round the bend of the Southern Appalachians and developed a well developed comma head as it was reaching the height of full maturity on all levels, both aloft and at the surface.

March01_2009GASnow

By dark the Interstate 85 corridor just east of the Southern Apps was being hit hard with 2″ to even 3″ per hour snow rates at times in the extreme northwest shield of the Upper low.  Isentropic lift surfaces revealed a strong lift from east to west, wrapping around the core of the upper low and working on and increasingly cold atmosphere in the western Carolinas. Ironically enough, as sometimes is the case, a small mesoscale warm pocket at the surface and aloft developed just in the extreme immediate lee of the Southern Apps near Marion, NC and Oconee County SC where there was little to no snowfall.  The snow accumulations map bears out western McDowell and Burke County, NC (just east of the Blue Ridge Mountains).  There has been several examples of a warm eddy trapped against the escarpment where it’s just too warm to snow, yet all areas further east, south and north would end up changing from rain to heavy snow.

March01_2009_IsentropicLift300k2

RUC (Rapid Update Cycle)

March01_2009_18zRUCanalysis

 

 

March01_02_2009SnowmapGSPzone3

AnimationGSPradarMarch1_2_2009Smallestcorrected

As the system reached the maximum tilt on it’s bend overnight on March 1st, the snow became so heavy and wet and fell over 2″ per hour along Interstate 85 in the Western Carolinas, along with thundersnow, the power lines began to succomb to the weight of the clinging, extremely wet snow.

Mar1_2_2009PowerOutageMap

 

March01_02_2009_RAHstatemap

Satellite pictures from March 2 and 3 revealed the snowcover underneath and west of the track of the strong upper low

March3_2009SatelliteGASCNCAL2

 

March2009SnowCoverModis2

 

The modeling ahead of the storm was well handled by Canadian and European Models.  The NAM as well did extremely well with the 7h moisture feed wrapping into the comma head feature on the northwest side of the system as it travelled up the East Coast.

 

European Model from 48 hours Out:

euroday2

 

European Model from 72 Hours out:

euroday3

GFS Deformation Band at 7H shown from 48 Hours out:

gfsdefamation48

The storm of late February and early March 2009 went on to relieve several areas of the Southeast and MidAtlantic of a long lived snow drought.  Areas from Tennessed, Alabama, Georgia, the Carolinas and Virginia receieved their biggest snowfall of the season and the biggest in several years in some cases (like Richmond) from this system.

28
Feb

Updated Discussion On Next Week

It’s still too early to know the exact track but now is the time to be monitoring the trends of all the models.  The most important thing to watch for is the closed blocking still showing up and remaining persistent and in place in eastern Canada.  The European is probably the best with this right now and how much energy is rolling around that southern periphery and also around the 50/50 low will determine if it phases or not with the Plains cutoff.

Here’s a look at todays ECMWF run and I’ve noticed it has trended southward some, and doesn’t fully phase with the Southeast Wave until it’s offshore the NC coast.

ecmwf120

This run goes on to “wobble” the cutoff from Nebraska through Georgia and really get its act together by the Carolina Coast. This run would pull the snow further south from the MidAtlantic and focus it on the northern strip of Ark, Ms,Al, Ga, much of TN, NC and upper SC.  But it’s wayyyy too early to expect this track and for several reasons.  The biggest one is that the system is still well out in the Pacific and won’t be sampled well until it gets onshore Saturday night.

watervapsmall

 

Closely looking at today’s 12Z GFS and you can see it’s faster than most models and takes an even further south track thanks to that blocking ridge.  There will be  a fundamental question on Monday night and Tuesday of the location of the shortwave near the Lakes that will attempt to phase into the Plains wave soon.  It’s too early to say, but the ECMWF is holding off just a bit on that, but I don’t trust any model yet on the location of either feature. The GFS gets shunted, instead of phasing or even partially absorbing that additional energy.  If the block is still strong, I think the northern stream could phase with the developing Upper low and become several contours closed.  Right now, no model has a big closed low until offshore the Carolina Coast, but instead GFS “wobbles’ the low…notice on all the animations that low is gyrating around itself, a sign of a not too well developed system.  Only time will tell once we get this system near the West Coast of how well developed it will be.  The better developed, the more strong the storm will be.

GFS120vort

GFS 132 hour:

GFS132vort

GFS 144 Hour:

GFS144vort

GFS ensembles are a little north of the operational but have a very strong closed block in eastern Canada, so there’s no doubt the system will begin to dive more southward through the Plains (GGEM Canadian looks too far north)

GFSensemble120hts

None of the specifics of the storm really matter yet until we can start to get a really good idea of the track.  I still favor the Tennessee Valley, NC and VA and the MidAtlantic coast as a high impact region from the system.

One specific I can go ahead and put there is that the best area for snow initially will be on the northern and northeast shield of the incoming upper low, and then transitioning to the northwest side of the Upper low.  That’s how most upper lows work on a trajectory like this.   The track rougly resembles the March 2009 upper low from the northern Rockies through the Western TN Valley, swooping into Georgia ..but in this case, no model takes it northeast ward, only east bound. We’ll have to see about that.  Almost every system I’ve ever watched has made an attempt to turn northeast from GA, SC, NC region, but that’s no guarantee this will.  It will depend on a lot of features aloft in the Northeast.  Regardless, When well developed upper lows reach their inflection point (begin to bend) or turn negative tilt, then thats when the system deepens rapidly and pulls in cold aloft. So far no model has a good strong closed low with comma head look to it’s precip panel (but does explode over eastern NC). However,  I won’t be surprised to see this upper low trend stronger with each run and more well developed.  There is an excellent ridge developing behind it and there’s good wavelength spacing, so I see no reason not to deepen this upper low into 3 contours closed coming through the Southeast or Tenn. Valley or MidAtlantic.  We will see.

I wouldn’t concern myself with snow rates, snow amounts or time of day for the event yet, although these are very important in March Snows.  Rates always trump surface air temps.  As always in March, many places south and east of the Upper Low will at first get rain before going to snow, but there could easily be several hours of heavy snow and accumulations under and north of its path, and then if the system slows and feeds on additional Great Lakes energy, a major system can occur and be more widespread.  It’s just too early to tell and there’s a ton of things to consider from 6 days out. How ironic that March (And December) are usually the times when snow can fall in the South or Mid Atlantic over the last decade, bookending a warm core of January it seems.

 

 

 

28
Feb

Possible Major Snowstorm Appalachians, MidAtlantic States Next Week

Mar5_7_2013_threatmap2

The ECMWF model has been consistent for 3 nights now on a Major storm affecting the East Coast from somewhere in eastern NC roughly to Long Island roughly.  The models are still adjusting to the northern block in Canada that will still be in place, but the details are still unknown at this point.  If the block is near Baffin Island, usually climatologically that favors the ECMWF track toward the Mid Atlantic. However if the block isn’t as strong (still unknown) then the storm could pull further north than the ECMWF model shows.

The GFS has been waffling back and forth on this track, and sometimes doesn’t have any interaction with the northern stream, and instead leaves a “bowling ball” type of upper low detached from the stream which allows it to roll across the upper Southeast, and then possibly merges with an upper disturbance offshore.  That solution would not be a big snow for anyone, but could spread some light snow and rain along its track in the Southeast.

If the northern stream (disturbance gets pushed south from the block) can merge with the main system as it drops from the Plains toward the MidAtlantic, then the storm will slow down in NC and then reform and deepen rapidly just offshore the Outer Banks of northeast NC, which could spread a near Blizzard for eastern NC through Virginia and the MidAtlantic.  With so much incoming energy that phases with that storm, the heavy snow will extend back through the Appalachians and Piedmont, but downsloping in southern NC and much of SC would allow only scattered light snows in the lee of the Southern Apps.

The track is still uncertain at this point, as is the case on most storms from 5 and 6 days out, but the ECMWF has been maintaining some decent continuity, but it will take a few more runs  and more model agreement to nail down the exact track and depth of the storm, and whether it will slow down and phase with northern energy (which would be a major “Foot Plus” dropping type of snowstorm in northern and eastern NC, much of Virginia, West Virginia, Maryland and southern New Jersey and Delaware.  If the block is weaker at that time, the storm will pull north, if the block is stronger than shown, that could actually send the storm slightly further south and more of northern Georgia and most of the Carolinas to southern and eastern Virginia would get hit.

The Canadian model is weaker and further north but doesn’t have much of a storm.

(GGEM Tuesday PM)

GGEMtuepm

GFS Tuesday PM (further south)

GFStuepm5h

GFS Wednesday AM:

GFSwedam5h

 

If the ECMWF maintains continuity, the threat of a major snowstorm in the MidAtlantic region will really increase rapidly for the Tuesday evening through Thursday timeframe.  This models has been good on big Eastern Storms since Sandy and the Northeast Blizzard, but since we are now entering a pattern change with a Baffin Island block, it’s hard to say. In the past those Greenland to Baffin blocks have been notorious for delivering big Southeast to Mid Atlantic Snowstorms as I mentioned a week ago when I saw the block coming.  And now the models are responding.  If the European model is right in holding the upper feature as closed the entire track and then phasing and stalling, this will be a top 10 or top 5 Eastern Virginia and eastern NC snowstorm, with blizzard conditions, high winds, heavy blowing snow and thundersnow with snow rates over 3″ per hour at times in those locations and possibly total accumulations well over a foot.  But everything will have to come together perfectly for that type of big storm to verify. Right now I’m leaning toward a very significant event.  Regardless, right now all models have a closed upper low entering the West Coast and then dropping southward, and the way the GFS rounds the bend of the Southern Apps still sends strong alert signals that a major storm is possible, even though that model doesn’t respond quite yet. Strong closed “bowling ball” upper lows in March that enter the Southern Apps and Piedmont region with cold enough air almost always are accompanied by heavy wet snow on the northwest shield of its track and sometimes Thundersnow, but for a much smaller region than what the ECMWF model shows.

Check back with WxSouth.com for updates.

 

27
Feb

Colder Weather In the South (Daily Snowshowers Mountains)

There’s some of the best skiing for March coming up, if you have a trip planned anywhere in the Apps over the next few days.  Daily snow showers will fall in northerly, northwesterly flow with several disturbances embedded in the flow. On strong vort may still try to cutoff somewhere in the Deep South briefly, but it doesn’t look very likely or strong, if it happens.  All models do have a weak inverted trough or lee trough extended across the Savannah River on Saturday, so a weak low may develop near the SC or GA coast and have a small focus that mid level moisture can work on in northern Ga to Upstate SC and parts of NC.  But I think anywhere in the South will have scattered flurries on Friday night and much of Saturday, just passing flurries, with the most being in the mountains and again a possible little bit more around the lee of the Southern Apps in the Carolinas and Georgia at some point, but this shouldn’t amount to much.  I’ll keep an eye on the models, particularly RAP model on any mid level closed circulation as time gets nearer, because a meso scale enhancement can’t be ruled out.

namcombined

 

After this cold wave (and yes Florida will go to freezing by Monday morning) then the pattern relaxes briefly, but already there is another wave that will be dropping in from the Rockies.  The ECMWF still has the block in place and both it and GFS drop that wave suddenly southward around next Tuesday or Wednesday through the TN Valley and Carolinas.  This is too far out in time to have any faith in, but the big picture shows the closed ridge to the north in Canada, so odds are this will be a diver. But how far south means everything. The temps will begin warmer in GA and AL and SC, but get colder north of there, but the closed low itself could have snow with it under and north of the track and it’s too early to know that track yet.

It could be that it merges with additional (unseen ) energy from the lakes and pulls more northward, or that the block in Canada is still strong enough to keep it more southward. This could trend into a very significant Snowstorm for a few areas in just the right spot along its track. AGain, its too early to make that call, just something to watch. As you can see by all models around that time frame it appears that the system will affect areas just northeast of TX/MS Arklatex region, so areas in TN, AL, GA, NC, SC , KY, VA regions are the ones in the Southeast that could be affected by a rain or rain to snow scenario.  If the storm can develop offshore and merge with andditional energy like last nights ECMWF run, thena  bigger system could evolve. But we can only take this one run at a time in this changing flow and the models will waver. I like to look at the bigger picture and work inward with time, giving a heads up and not ruling out scenarios until it’s safe. If the system closes off and slows down, then the MidAtlantic region will really have to pay close attention, and we’ll talk about this more as time goes by. For now, I’d prefer to keep my eyes on this sneaky weak system this weekend and the cold air. Enjoy the break from the rain!

26
Feb

Another Close Call With Upper Low?

The next system to watch is going to dig due south from the Plains toward Arkansas and Miss. later Friday and possibly close off, but the models aren’t sure whether to fully cut it off or just shear it out.  It will be a complicated mess for the models since we are now entering a retrograding flow up north.  YOu can see the flow from Scandinavia backing up to Southern Greenland and this will begin to buckle the pattern.  This is a crucial time for s/w digging south from the Pacific, and also to further complicate the setup is the Pacific itself….it’s still loaded with features and each day the models and ensembles show different s/w’s and different strength and track.  Thats the danger of looking too far out in time especially in this active flow and now that we have a definite retrograding and blocking up flow, I think the models are going to have a particularly hard time.

Here’s a look at the ECMWF ensemble as early as Saturday (96hr).  You can see up north a nice ridge in Greenland which has squeezed off and will stay put basically, creating a “Rex Block” type of look.  In the past, many times features have took a dive due south and created a Southeast and Mid Atlantic storm, but in this case, the Vortex off the Northeast coast could be stuck in position, so that would be at odds with the s/w closing off so close to it in the Southeast.  It’s going to be hard to do, unless the Northeast Vortex moves out of the way, or unless the Plains wave can dive any further south and west, more toward eastern Texas than say the Tennessee Valley, so thats something to watch in the next few runs.

ECMWFens96

 

The GFS briefly closes the low around western TN and generates pockets of snow with weak development , but it never really pulls any moisture from the Gulf. Mostly this snow will be light under it’s core and just east in the small brief window of time of lift under the divergence or weak shortwave ridge it can develop as it moves east across the South.  Again , in the big picture, this is very similar to what we saw a couple weaks ago when the models all showed East Coast development and went back and forth with that longwave axis being just a fraction too far east to allow good development and instead what happened was brief snow bands developed in the Carolinas, and the system ended up bombing and forming an eye in Eastern Canada. This time though, it will be all snow , everywhere in the South, if there is moisture.

gfssnowtotals

Odds are in this new flow, the rainy pattern is over with for a while, but there could be development since the models keep that blocking up north.   And I will say that in the past, with blocking in that location (And GFS and ECMWF keep it there over a week) then in the past that has coincided with a Winter Storm in the Southeast or MidAtlantic.  But also keep in mind this has been a very unusual 2 year period, especially lately when almost none of the indices and teleconnections have worked as they normally do.

I’m on board with a colder pattern for sure the next week or 2 to start Meteorological Spring and in fact could be colder for the Southeast than part of January was!

This will be a hard pattern to predict the movements of systems and no model will get it right, so it’s up to the forecaster to use good judgment on how the past has worked with this kind of flow.  And my number one rule on backing or retrograding flow in eastern Canada is that systems can dive extremely far south, so the NAM and GGEM lately could be on to something.   I wouldn’t be surprised to see the models dig that wave so far south it cuts off near the Gulf States or the Florida panhandle with snow deep into Georgia or even the Florida panhandle with such extremely cold air aloft.

I’ll get more in to the next system and the one after that soon…there are many things to follow in this new flow, and odds are that snow does fall once again somewhere in the South, but the timing and amounts are still up in the air.

 

 

 

 

 

25
Feb

Wild Weather Pattern Is Here..And To Stay

If you’ve read my columns lately you know where I’ve been headed. The NAO is going down, the AO too and there is a good chance at western ridging..all these are going to be simultaneous, which is something not seen yet this Winter.

First, we have to get through the Blizzard in the Southern Plains and the Severe in the South. Right now all the models continue to converge toward Wxsouth thinking from 3 days ago on the ice.  The high stays inland. I looked back strongly at Christmas 2009 and saw a nearly carbon copy of the 5H and surface features, so I’m not sure why other forecasters were writing this off as ice goes. That was a severe (but very localized event) in southern Yancey, much of Watauga, Ashe, southern eastern Avery, and eastern Buncombe to eastern Henderson County NC event where the event began early in the morning predawn and locked in the coldest readings. This looks the same roughly.  For Roanoke and points north, the timing is a little bad, but I think that area will have a moderate ice storm, but areas where it begins predawn will be the worst.  In this micro scale event, Jonas Ridge to Deep Gap to Galax is about the worst setup possible, with temps dropping into the upper 20′s and there’s no way to warm it except from the top down, and that is always a slow process. By the time its warm enough, the precip is ending, so I’m going with 1″ of pure ice and downed power lines in roughly the same regions that got hit in 2009.  The 850′s are being captured nicely on Hi Res NAM as being cold enough for snow for several hours around the high country, but that won’t last.  For eastern West VA it will last longer as snow, and then go to sleet and ZR but the overall amounts and time of day isn’t the best for a really HUGE hit of an icestorm like it will be further south and southwest I think.  The NAM and GFS both have 1″ or more of QPF in nw NC and extreme SW VA region as mostly ice and the easterly flow will keep adiabatic cooling from upslope going in the event, despite the fact at Beech, Sugar, Mitchell and Rogers level it will be much warmer.  You can see how this is a unique ice storm setup and one that favors elevations between 1500 feet and 4000 feet roughly in a narrow zone.

NAMdevastateIcetotal24

When the cold front and squall line moves east into the cold dome in GA, NC, SC tomorrow afternoon, ther could be a meso low spin up like last January (Concord Tornado) somewhere in the vicinity of the 85 corridor from Athens to Raleigh and points east. Further north and west, the dome of CAD will hold strong, and there is going to be a huge temp gradient from north to south across the region.  Roanoke could be 32 while Charleston could be 72 at midday.

The good news is the wet pattern I promised over a week ago has come to fruition for GA and SC where rain is badly needed. Now with supressed flow coming up, I’m sure we’ll look at more chances of that, plus I’ll get into the snow storm chances.

Did I say snow?  Yes I believe I see Winter storm chances increasing as we begin meteorological Spring….ahhhh weather in the South, where January is flip flops and tank tops and March is snow skiing.

satelliteFeb25_2013

 

 

24
Feb

More Southeast Rains (IceStorm Valleys/Apps Escarpment)

The deep low will turn toward Missouri with snow and thundersnow on it’s northwest side, and blizzard conditions there, even some wrap around snow showers for Arkansas, western TN and much of Kentucky later Tuesday evening.  Severe threat will again occur in the southern sector, and Tornado Watches could be issued.  For the icing part of the storm, there’s no change from yesterday, as all models keep about the same look.

 

Total Precip:  Another soaking for the Southeast.

GFStotalprecip

So this will still be a very close call, but the zone of impact is narrow and only affects a few areas with snow and ice. First the 850′s will cool slightly as you can see on the models, with pockets of Zero scattered through the first half of the event around Monday night and early Tuesday morning in western NC and western VA.  The surface temps will drop to near freezing as well in some valleys just east of Asheville and points north and northeast through the northern NC mountains, where Boone will start as snow and then have a mix of snow, to sleet and eventually mostly freezing rain.  In the end, this storm still looks similar to the Christmas Day 2009 storm in many aspects.

Here’s the GFS surface temps at 7 AM Tuesday, with 32 at the surface down to northwest NC.  It doesn’t capture the pockets of freezing that will be even further south. As you can see this will be  a narrow zone, like the big Jonas Ridge and Valley icestorm in 2009, with temps around 30 or 32 for much of the event and about 1″ of qpf being thrown down.  Several inches of snow is likely to start but the snow won’t last long with such warm advection aloft, leaving sleet and freezing rain.  Usually when the High pressure strengthens in the Northeast and remains inland, thats a sign that the cold air at the surface will NOT get eroded in the areas that fall to freezing, until after the event is over. This is where WxSouth differs greatly from say the NWS on this region. I think this will be a very big deal for the folks that get the ice.

GFS48_surface

Even as the event is ending mid day Tuesday, the GFS shows the zero line at the surface still hugging NC/VA border.  It’s much harder for freezing rain to occur in the lower elevations during the daylight, but this will still be a problem in nw NC mountains and western VA, but the bulk of the heaviest precip looks to be maximized with falling at night and early morning as well as heavier amounts around the northern NC mountains.

GFS54_surface

The pattern will turn colder and drier after this storm, but the longer range is filled with uncertainty.  Exactly how the blocking to the north and if any western ridging can develop will determine if there will be a strong cutoff low at some point near the Southeast. The models almost show that, but not quite. Euro run is getting very close to doing that next weekend for the Coastal Carolinas and has some snow with deepening trough and a s/w digging throug the Gulf States. This could be something to watch, but we still have a lot of disagreement on the upcoming pattern with GFS and ECMWF being quite different.

The GGEM digs a due north to south system later on as it builds a big western ridge and sees teh closed block in eastern Canada. If that type of meriodonal flow occurs, then that would be something to watch as far as a system closing off.  We’re in that time frame of year where they are more notorious, more common and when you add the fact we’re in a retrograding , blocking up flow, then I have little doubt a big cut off is very possible. I just can’t say when or where.

GGEM168northerlyflow1

The European run lately has shown some bizarre looks , so the models are going to be in a chaos state as they try to adjust to the backing/retrograding/blocking flow.  This is an unusual look for the models, since we haven’t seen much of this in the last few years, and to be honest, anything is still very possible with the upcoming pattern. It looks active, colder than normal and will have to watch individual s/w tracks as they could go places the models don’t predict a week out.

One odd note about observing the models lately…the ECMWF has been building the western ridge strongly, GFS has not.  This is a reversal from usual biases and roles, and we’ll have to wait to see how it goes.

 

 

23
Feb

Could A Big March Snow Storm Be Lurking ?

March2013_PossibleStorm

Before any readers skew this, I’m not calling for a major snowstorm to paralyze any part of the East Coast or Southeast, like what happened in March 1980.  I’m only noticing some synoptic recognition to see how past events can foretell future events if you look for patterns. For several days, I have been keenly studying the models and ensembles and where they may be going regarding the overall look at 5H in North America (and the Northern Hemisphere).  There are some striking resemblances to past big Winter or Early Spring Storms showing up, but so far, I’m only giving this as a 30% or less chance of becoming a reality.

First, we don’t know if the Southern Greenland ridging will become real, or actualized. Several times this Winter, the models have thrown up blocking there and it never worked. Not yet anyway.  But all models and ensembles for a few days now have agreed that it will come.  They take Scandinavian ridging, and roll it westward (retrograding flow–which is rare) to a point where southern Greenland and eventually much of Canada is under above normal heights.  Take a look for yourself.

GFS 192 hour Anomalies:

GFS192Anomalies

Since this is still over a week away, I have a little skepticism, but I am very surprised at the GFS and ECMWF ensembles all being adamant at bringing this type of upper level anomaly closer and closer.  We will see soon if the models keep this up. I should mention the GFS is more east based eventually than the ECMWF and lacks the big Western Ridge the ECMWF has in its operational and ensemble run–which will be critical if a storm is to form.  But just using general synoptics, I see that all models do have an unusually north to south flow (meriodonal flow) which only occurs to this extreme every few years.

Even the Canadian (GGEM) has this strong amplified look, with a strong western ridge which forces the flow due south through the Plains and maybe toward Texas, before hooking strongly northward again.  Usually when flows get this amped up, a cut off will form.  So far, most models aren’t doing that.  But at WxSouth.com over the years I’ve often forgave the operational models in their errors and looked beyond the explicit runs, to dig deeper into the possibilities. Occasionally, models will pick up on major events well ahead of time, like “Sandy” or “Superstorm 93″, and  a few others.  But many times they will show a look at something possible, without giving the expected actual result.  I’m not sold this will happen , and think the odds are still low, but based on some past history, and including this own Winter, I think it’s worth mentioning this far ahead in time, just because of how historic it “could ” be later on.  The GFS showed a severe deep anomaly in early to mid February from 10 days out in the Tennessee Valley and Southeast, and in which case a very close call occurred, with a snowstorm in the Carolinas.  That storm ended up bombing out in eastern Canada to around 950mb low and formed an “eye” .  In the big picture, once again, that was very , very close to a major system paralyzing the East Coast.  But ended up in the Ocean more than affecting the states.

GGEM at 192 hour:  Shows a very amplified flow with energy topping the western ridge and forming a system just off the Southeast Coast.  Any error here could have major results.

GGEM192PossibleSEstorm2

 

By day 6, the ECMWF has a strong western ridge with a developing Greenland Block.  The location of Greenland Blocking will be crucial, as in the past it has shown that if its more southerly based, then the odds for a supressed storm in the South go up substantially. Further north, then the storm is more likely to affect New England or be out to see.

Day 6:

euro6day

Even at day 8, the ECMWF model still has such strong +PNA ridging and it “tips” the ridge inland to western Canada enough that the energy topping the ridge can possibly dive due south toward the Gulf of Mexico or the Gulf States.  If that happens, that would be extremely rare.  But then again, the ECMWF handled Sandy very well and used the Greenland ridging to develop a strong hybrid storm and cutoff in the Apps during that time as well, from 10 days out, which is very good for any model.  The key here will be the southern Greenland Ridge, and if the model is right on that western ridge as well. The GFS doesn’t have that much western ridging, which is odd because it has handled western ridging much better all Winter long this season than ECMWF…so I’m skeptical at this point.

Euro8day

Both GFS and ECMWF models have a strong Negative NAO pattern coming, and this time, for the first time all Season, combine it with some +PNA pattern.   But verbatim, the models are still not synched exactly right to deliver a powerful east coast or Southeast storm, but it’s so close to happening, it’s worth a mention.

00zecmwfensnao

12zensnao

As you can see the NAO numbers are very low. This will combine with very negative AO numbers as well, and only time will tell if the AO study I did earlier this season indicating it’s prevalence to Southeast Winter Storms will eventually be justified. Or if this will be the one time it didn’t work out.

The odds are the pattern coming up will be cold and just cold, mostly dry. There will be periods of snow in the Apps and downwind the Great Lakes just from northerly flow.  There will be cold rains in Florida (possibly even a few sleet pellets somewhere in one morning) with such a supressed flow and blocking going on in Greenland. Only time will tell if the models have once again over did the Block in Greenland. But if they are right this time on that, combined with a strong western ridge, then the odds of a cutoff forming in the Southeast or near the East Coast is atleast 30% in my opinion, which is pretty high.  That also means that any storm that forms will still be mostly an ocean storm, but if the pattern lines up exactly right, and there is a due south flow at some point with extreme western ridging and perfect placement on Baffin Island/Greenland Ridging, than just using the anomalies alone lends credence to the idea that a major Winter Storm could be in the forecast in early March.

Compare March 2 and 3, 1980, with the last few runs of the ECMWF model.

March021980Heights

Anomaly forecasting is very important, and could provide some general answers, but it’s too early to be that specific. As I mentioned earlier, I don’t think a major storm has much more chance than 30% of hitting the East or Southeast yet.  It could be that we only have enough High Latitude Blocking and western ridging to produce just a general northerly flow with some cold air and have a very cold early March period. And most of us are left just cold and dry, and partly cloudy. But the anomalies alone lately have been enough to justify a deeper look into the chances.

 

23
Feb

Stormy ! No Rest For Meteorologists.

Tired of the rain yet? I’m sure not for those that need it.  This has been one of the cloudiest Winters I can recall…very few truly sunny days, with each day either starting sunny and ending in clouds or starting cloudy and ending in sunshine.  On to the weather…

Big things are going on and there’s no rest for the weatherman. First, there is a chance at a major snow and ice storm for the Apps, roughly for Jonas Ridge/Black Mountain and points northeast along the escarpment.  The GFS has been most consistent here.

By Monday night the 850 line reaches down to NC/VA border and includes the northern mountains. Most likely this will be snow to start but warm aloft will come in and change it to something else.  By early Tuesday the precip will be moving through the Spine.  It depends on how strongly the damming can occur, and exactly when the high pressure slides out to sea. The ECMWF pinches off a high and leaves it inland, thats why its colder.

GFS66microanalysis

GFS 72 Surface temps (Tuesday 7 AM)

GFS72microanalysis

The ECMWF is a little colder and would threaten more of the nw piedmont of NC, and southwest VA with ice, but its the cold outlier right now.

Severe is possible ahead of the upper low and closer tothe Gulf Monday and Tuesday.  And on the northwest side of the upper low, heavy blizzard like snow. Already Blizzard warnings for Oklahoma.  This upper low will likely drop a few flakes on its southwest side near MEM and BNA later Tuesday, but the lions share will be near and west of ST. Louis back to Tulsa area.  Another big rain event for the Southeast.  And then things get all blocked up and change for the colder.

Before I get to that, here’s  a look at the Christmas Day Icestorm and what happened to a very small sliver of the Apps or the escarpment of the Apps during that event. It began early morning and ended mid afternoon, and was mostly around 32 degrees in Boone (temps varied around the region from upper 20′s to 33.8) but the idea is that local effects are common there and this 5H setup is nearly identical to that event, with a strong damming and confluent zone in the Northeast to the upper low west of the Apps and small but very  strong damming right along a very small sliver of the chain.  This will come down to micro climate effects.  I have little doubt that some areas of Yancey, Burke, Caldwell, McDowell, Avery , Watauga, Ashe Counties will feel atleast some part of the Winter storm with the worst probably being around Watauga, Ashe and northern Burke regions due to local climatology.  The GFS drops 1.10″ liquid as subfreezing in Boone!  That is a terrible ice or snowstorm for the region, but I think most will be ice (sleet and ZR) not snow, but some snow to start.

One thing to consider on micro studies like this is the Placement of the HP and how it grows, skews, and slides or evolves.  This one is progged to strengthen from 1020 to 1028 during the event. This could be crucial.  At WXSOUTH I always prefer to look at old synoptics and work inward.  As opposed to using something like soundings from the model runs.  Either way in this case, usually GFS is very good with damming, the best the last few years.  One thing that could save or atleast reduce the ice accums could be the high sliding out to sea just before the bulk of precip arrives pre-dawn. But usually diabatic cooling in CAD is strong and hard to eradicate, so once temps get locked in at 32, usually there they will remain.  So I’m placing that region mentioned above on high alert for a high impact Winter Storm Monday night and through midday Tuesday.

Christmas Day 4 Panel (2009) Nearly identical setup

ChristmasDay2009_4Panel

(Jonas Ridge, NC)

BooneIce3_Dec25_2009

Once this system passes through, the blocking at Greenland begins to take over and I’ll reserve that for another post. I’ll say that parts of GA and SC are on their way to a top 5 wettest Februarys on record. Way to go. I think Augusta will top 10″ of rain this month…amazing considering they’re also coming off a super dry January.

 

22
Feb

Saturday Update…March Will Come In Cold!

“Happiness is like a butterfly: the more you chase it, the more it will elude you, but if you turn your attention to other things, it will come and sit softly on your shoulder.”

- Henry David Thoreau

Interesting dilemma coming up on how the pattern goes. First, we’re certain to have a colder pattern (or an extended part of the pattern we’re in now) but even colder is coming to the entire Southeast.  The GFS and ECMWF get there in slightly different ways.

The GFS has a big upper low drive through Kansas and MO then uses that to cutoff a big deep trough in the heart land and eastern US for a while. It has several different systems passing through or rounding the bend of the trough. It even shows a slightly retrograding flow, and if that happens, that will most definitely open the door to a Winter Storm coming up from the Gulf sometime next weekend, and maybe another system after that. But it’s too dangerous as this year has proved, to go too far out.  First we have to get the Greenland ridging to show up and verify, and it’s still a few days out.  But the trend on the mid week storm is further south and stronger…this in it’s own right will cause some problems with more snow in the Plains and on the northwest side of the track.

The NAM also is more like ECMWF with that strong cutoff barrelling through the lower Midwest. It’s so far south that snow would fall in Arkansas, western TN, KY areas once the upper low comes through Tuesday.  Also, I’m keeping my eye on another damming event for VA and NC ahead of that storm.

NAM 84 (NAM has been the best model by far on upper lows coming through the South).  ECMWF concurs.

nam_namer_084_500_vort_ht

On thing worth a mention on the NAM and ECMWF track with the upper low is the increasing threat of severe weather along the Gulf ahead of the storm.  We’ve had tornadoes in lesser systems, so I think SPC will be highlighting that region of the western TN valley region to eastern Texas soon.

 

ECMWF shows an extremely close call with very close thickness and 850 pattern for the northern mountains of NC and into West Virginia (Allegheny Mtns).  If the system trends even further south, or if the damming trends a fraction stronger, this could be a big snowfall around Boone, NC Tuesday and maybe another Winter advisory for the northwest piedmont and western VA region in the CAD areas that just got hit again.

The GFS retrogrades this big trough and in tandem builds  a stout western ridge.  So it appears we will now have something we haven’t had all Winter long…namely, negative AO, NAO and western ridging. You can hardly ask for more in the indices.  But recall the indices have yielded odd results all Winter long.

NAOforecast

The ECMWF run uses the big eastern trough to just deliver cold to the Country, but also has a strong storm affecting the Northeast, so it batters Boston again with a major snowstorm. That entire trough is so large that it almost splits, with a secondary lobe nearly cutting off in the Deep South by day 8 or 9.  This will be something to watch. I don’t think ECMWF has  a good handle on this flow at that time range. Regardless both it and GFS show a big eastern trough with several disturbances rounding the bend of the trough and both show strong Greenland Blocking and western ridging. This is a pattern that can trend into a Major Winter Storm for the Southeast, even though no model yet explicitly shows it.

I’d say if the ECMWF is right with its more eastern trough axis and broad based trough, it would be hard to form a southern storm.  But if the GFS is right with it’s more western based trough axis, then a storm would be likely to form.  Both are close, but the devil is still in the details.

 

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