Blog Has Moved Locations

My blog is now active...but I have moved it to a more user friendly FB page. You can find my forecasts and thoughts at this address now

http://www.facebook.com/Wxeast

Or you can just visit our Forum

http://www.tnweatherspot.com/

Boring Weather Alert

This Blog is not currently active...and will likely not be updated again until sometime around Hurricane season or Fall. If you are still interestsed in discussing the current weather then there is a link to the right that will get you to our weather forum...where there is active discussions going on :)

Thanks
Toot

Late Season Snowfall North of I-40 Sunday Night

Good Afternoon...After a rough night of severe thunderstorms old man winter could pay one last visit before taking a vacation. A late season clipper system will race into the region sunday and bring clouds and limited moisture. However enough moisture apprears likely for light snow accumulations on the plateau.. the mountains and areas in the valley north of I-40 up into the Tri Cities. Since this snow looks to fall of the night wet accumulations appear likely. Temps sunday night will drop below freezing so hazardous driving conditions will also be possible.

Significant Tornado Outbreak Possible Tomorrow

A vigorous low pressure system will traverse the western midsouth into the great lakes region. This low will probably be very well organized and will likely go sub 990 milibars as the LPS matures. As it starts to move northeastward an associated warm front will move through the area overnight and there could be a few severe storms that fire along this warm front tonight into the early a.m.

IMO this warm front will be the most important equation that will ultimately decide how significant tomorrows threat will be. If the warm front moves through rather quickly then look out... its gonna get nasty. The slower the warm front retreats northward the less significant this threat will be. With a slower moving warm front you will have junk convection trying to stabilize the atmosphere ahead of a very powerful cold front.

There's gonna be severe weather either way but if that warm front and its associated convection moves through the area rather quickly the surface layer airmass will establish a very favorable thermodynamic enviroment where the sun will begin to break through the clouds warming surface temps...then the atmosphere will become VERY unstable due to the high cape/high shear.

If that happens discrete rotating supercells will likely invade middle and east Tennessee transforming into line segments as the cold front nears the spine of the Appalachians. There could also be embedded supercells in these line segments. If things do go downhill tomorrow it looks like the western plateau area would be right in the bullseye and folks in east TN will have to endure a nocturnal Tornado threat which is a whole other creature itself.

There's alot of if's involved in this setup and this event could wind up being either a standard severe weather outbreak or an extreme one... so I would just stay tuned to my local NWS office and its radar.

~ Toot

2012 Severe Weather Outlook

Well...It looks like spring is almost here (even though as I type this there is strong cold advection doing its dirty work outside my window) and its time to try and poke my head into the future to see what spring may hold in terms of severe weather. Ive looked at a few sign and signals and this post will portray if they point to a more normal season which is pretty intense itself here in the southeast...or if the potential for severe weather is above or below normal.

I was gonna do some analogs for this season but since that didnt work out to well for the winter outlook I will stick to the facts here..nothing but the facts.

First lets look at where we are headed in terms of ENSO


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What we see here is us headed out of La Nina and into weak El Nino territory most likely... but during spring we should be near neutral ENSO conditions and that will not hamper severe weather in any way that I can find. The important thing here is that we have two major changes going on with winter transitioning into summer and La Nina transitioning into El Nino.


Next we will look at severe weather trends over the first part of 2012 and compare them to the same time last year in 2011

Here we have the spc reports since the first of January this year..as you can see its been pretty active for what is supposed to be a cold time of the year.



When we look back at last years graph we can see that severe weather was almost nil for this time of year before the active timeframe spike occured.


One can draw several different conclusions from that... but the conclusion I am drawing already is that the Gulf of Mexico is very warm and will be primed by the time our "spike" gets here.


Now speaking of the Gulf of Mexico lets look at the water temps because this is the fuel for severe weather in our area.

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Sure enough they are above normal. The lack of an extended period of colder weather over the southeast has allowed the waters of the gulf of Mexico to stay pretty warm and this is a pretty important signal that says an above normal severe wx season is likely. Now before you get too worked up there are some things that could possibly argue for a more normal or even below normal severe weather season.

The main thing that comes to mind is that the North Atalntic Oscillation has been mostly positive for many months and one could argue that it should be mostly negative this spring and this could offset an above average season to more of a normal type season. A negative NAO would try to suppress a Jet stream thats trying to come north due to seasonal change and could keep the stormtrack right over us or to our south mostly.

After looking at these and several more features I expect an average to above average severe weather season in terms of reports and there will likely be at least one major and widespread severe weather outbreak in the southeastern United States.

Snowstorm set to hit Tennessee

Im too busy to post a wrietup with this so here is my call map...If u have questions...register on our forum if youre not a member and you can read my thoughts there...the link is to the right of this post

Wintry Mess of Ice Sleet Snow and Rain

This is a forecast put together with todays SREF and NAM models..this forecast is highly dependant on the temp profiles of those models. If they are off a hair it could make for big changes in the outcome...this will ultimately be a nowcast situation but it seemed to be a rough one so I thought I would give it a shot

Light snow...sleet and freezing rain accumulations will be possible across most of the state on Monday and Tuesday. Particularly concerned for the East TN valley where I think the most ice accumulations will be possible.

Looking at soundings and mostly SREF data it appears that a mixed bag of weather will move into the state from west to east. With very low dewpoints already in place precip will move into the area as Virga but as the column becomes saturated precip will start to fall in the form of snow.

The snow could fall at impressive rates at times in the western and southern parts of the state. At some point the snow will transition to wintry mix and then to rain over most of the state. I imagine the plateau and mountain regions of the state could pick up several inches of snow in a fairly quick fashion.

The east TN valley poses a unique threat for Ice accumulation in excess of more than .10 inches due to the nature of local topography. After some possible light accumulations of snow the cold air might become trapped in low lying valley areas and freezing temps could stick around for a longer period of time but meanwhile the upper atmosphere temps will warm to above freezing resulting in longer periods of ice accumulations on top of light snow accums. Light Ice accums appear likely for parts of East TN valley

Old man winter has returned

A well developed southern stream shortwave will merge with a strong spoke of energy from a Upper low diving down out of canada and winter weather will result as a baroclinic zone sets up. A band of precip will develop along and in advance of an arctic cold front and will slide through the state tomorrow and Saturday. Where these two energies meet up will be ever important as to the outcome.

This precip will probably start as rain in most places but will quickly and dynamically change to snow due to strong cold air advection and wet bulbing. Flash like freezes will take place and driving conditions could become hazardous very quickly.

Due to the uncertainties I have just made a probability map and counties in grey have the best shot of seeing an inch or more of snow.

Eastern US Snow Storm threat Feb 11th-14th

Good Morning

After what has been an extremely warm winter things are changing as part of the Polar vortex relocates itself in Southeastern Canada. This feature may combine itself with a couple of other large scale features to produce a Noreaster the weekend before Valentines day. It all depends on where a subtropical jet strean shortwave starts to phase with the polar jet stream and its related vortex. This will set up a baroclinic zone along the east coast and a powerful low pressure system may form and ride up this zone in Miller A fashion.

The GFS has been the most consistant model showing this possibility and this remains the biggest eastern US winter threat of the season. The trend all winter has been for these southern stream shortwaves to cuttoff in the southwestern United States and remain cuttoff... but this shortwave is modeled to continue across the southern part of the conus without getting cuttoff from the polar jet and will likely phase with the northern stream at some point.

At the same time a northern stream wave of energy is moving across the northern tier of the US in tandem with the southern one. This will likely result in the most signifigant snowstorm in the eastern US this season but where the snow falls has yet to be determined. At this time guidance suggests a Gulf low threat and I have a higher than normal confidence level in accumulating snow in the Tennesseee valley.

Nothing written in stone yet but there is certainly a threat of winter weather in the eastern US near Valentines day or a couple of days before...the exact track of the stormcenter will decide who sees the accumulating snow.

My Feb - March Forecast for the SE

As you know...you have heard signs of a colder pattern change coming. I can somewhat agree with that although I think it will be short lived.The NAO/AO are already moderately negative.... I expect our area to end January on a frigid note as a deep trough with accompanied snow drops down into the Southeast. This pattern will be locked in place for at least the first half of Febuary and this will be the coldest around here its been all winter.








With the fading NINA and a pronounced NAO block in the baffin island to greenland location you will get that deep trough here in the united states. With 2-3 winter threats. Enjoy the first half of Febuary because I think the PNA and EPO will start to overwhelm the pattern by Feb 20th.





The old SE ridge will start flexing his muscle then... and that will spring us towards spring weather.






Thats not to say we wont get a bowling ball ULL come rolling out of Texas and produce snow in Late Feb or Early March..but by March the 15th cold winter weather will be all but gone.





Current NAO/AO is heading torwards the tank




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Severe Weather Likely In Late January

Being that there is a substancial warm up coming in about a week or so the chances for severe weather will be higher than normal for this time of year...so I went to looking for something to track and wa la..look what the euro model is showing at Hr 240.

Its still a long ways out but what some models show is definately a severe look with arctic air just pouring down into the western US and moist tropical like air being sucked up into the warm sector in the eastern US. This would cause fireworks where those two airmasses butted heads..not only that but that type of storm could definately flip a pattern completely over.

This storm could possibly bring the change that us winter wx lovers have been looking for since winter began. But there have many things that have fooled us on that particular aspect.

Alberta Clipper Round Two

Snow accumulations will be likely tonight/early morning as an Alberta clipper system will quickly track across the area tonight and producing light snow accumulations. Snow accumulations of a dusting to two inches will be possible.

Clipper To Bring Snow To The TN Valley

This setup is pretty unique being that the current system will continue to pull away and its NW flow off of the lakes will combine with the clipper trying to tap the gulf. This was a very confusing aspect of this timeframe and lead me to believe that this would be a pure NW flow event several days ago..but that is not the case. Anyways it will be interesting to see how this evolves on radar. At any rate I think the plateau area will do extremely well with this one as they will change over very quickly but everybody in east TN looks to get in on the action although places in SE TN may get downsloped pretty badly.

I would think that most of the snow will stick to the roads and ground with the very strong cold advection being modeled. Look for temps to drop like a bat out of hell tomorrow evening making for an exciting night.

Snow will be in the air tomorrow

A vigorous upper level disturbance will swoop thru the region on monday and bring a period of snow to the tennessee valley. I expect the snow to accumulate up to 6 inches in the highest elevations of east TN. The plateau counties and the northern valley could also see an inch or two...while most of the valley could see a dusting but I wouldnt rule out a little more than that due to the expected intensity of some of the snow showers and the long duration of the event. These snow showers will be accompanied by strong NW winds that will usher in the coldest air of the season...Glad to see the prospect of some real winter weather finally

Good Signs Of The Long Awaited Pattern Change

Good Evening and Happy Holidays

The weather lately has been pretty boring unless you like rain (It's certainly not my cup of tea) if you are a regualr reader of this blog you have probably heard me speak of a pattern change to more winter like conditions in several different posts and each time they never seem to stick and that has been due to the lack of blocking signals.

The pattern of late has been one of a "here today and gone tomorrow" type but several well trusted models are in general agreement that this is gonna change abrubtly in the new year. Blocking signals are starting to show up strongly in the NAO and PNA regions....lets not confuse the 500mb signals with the teleconnection signals because they are two different signals and dont always support each other. I expect a strong cold front near New Years that will be transported by what looks to be a clipper type system and if enough cold air is already in place we might get to witness one of those rare snow squall lines that set up along the cold front of some clippers during favorable conditions.

Several forecasters originally called for a cold winter but several of the same long range forecasters have since changed their tune to more of a warmer winter. Not me...im sticking with my guns and I fully expect the pattern change to happen around New Years. The AO has been off the charts positive for nearly two months and that is about as long as that usually happens so our saving grace is that it went positive early in fall and now has nowhere to go but to more neutral or negative values.


Toot

Winter Cancel? What?

Im growing tired of the cancel winter calls I am hearing...meteorological winter so far has not been a torch by any means...its been near normal to slightly above tempwise so far this December... Calendar winter has not even started yet and yeah that does have meaning..it's called winter solstice. With that said.... long periods of a tanking AO and a NAO block are not the normal December conditions here either... no matter how bad you may want to see those conditions...Wild swings in temps and patterns are more normal at this lattitude during the period of seasonal change from fall to winter.

Now I realize that people (including me) were expecting the neg NAO/AO to happen in December and it hasn't but it seems people have been spoiled by the last two winters and somehow think that cold and snowy is the normal pattern in December...its not!! People seem to forget that this is the southeastern united states and most unelevated places around here only average one or two days of an inch or more of snowfall during winter. Just remember there has already been two snow events already in the south even though they might have not been in your backyard.

Anybody making such broad statements as "cancel winter weather in so and so month" is completely wacko..I dont care who they are or what forum they post on. Nobody can make such a broad statement like that with ANY accuracy. If they cancelled winter weather for the months of November and December they are already wrong for parts of the mid-south... as they have already had two winter events no matter how long it may have stayed on the ground.

When there is not much confidence in any guidance it's pretty hard to argue with January climatology (which would be our snowiest month) especially if your basing your argument on relatively new teleconnect indices in the long range. People seem to think its allright to trust forcasted teleconnections in the long range but not model graphics when neither is very accurate for some reason. So no thanks...I will stick with climatology at this point

Rumors of Christmas snow

Good evening

Its been a beautiful day today with highs in the 60's to near 70 in some locations and it felt great...but I like to think of this as the calm before the storm. Mid to late December is climatalogically a favorable time for cold and snow around here and when it gets this warm in December you know big changes are coming. There are rumors flying around of some possible snow around Christmas and thats just what they are at this point..rumors!! With that said the pattern is starting to look more favorable after Dec 20th and it is possible that  a major pattern changing storm will occur with possible severe wx. I am talking about the storm around the 20th...

I think a STRONG lakes cutter with possible severe wx along a nice cold front that it will eventually push into the gulf of mexico around the 20th where another low pressure system MAY form along that boundary and ride up it in a path similar to a Miller A...of course this will need great timing and all but the possibility seems to be there. These two systems may be enough to dislodge the PV feature from eastern Canada and Greenalnd long enough where higher heights would then be able to form and in theory high lattitude blocking could then initiate in the NAO region near the new year. At least thats my take on the long range ensembles and teleconnections and any help from the PNA might speed this process up.

Importance of the Polar Vortex

Good afternoon

Most of the time on sundays I find myself wanting to research or write about a related aspect of the current pattern and today is no different.


Since there is a buzz going around about a possible stratospheric warming event I thought i would write about the relationship between the Arctic Oscillation...North Atlantic Oscillation and the Polar Vortex. These features are very important regarding sudden stratospheric warming and the Polar Vortex is the engine that drives NAO/AO. The polar vortex and the AO/NAO are directly related to each other and a general rule of thumb is a strong Polar Vortex equals a positive AO/NAO and a weak Polar Vortex equals a negative AO/NAO. A negative Arctic Oscillation (weakPV) generally means colder temperatures in the eastern United States during Boreal winter and a Positive Arctic Oscillation (Strong PV) generally means warmer temperatures in the eastern United States during boreal winter.

A strong Polar Vortex tends to be more concentated near the pole and circular in shape... it will generally keep the cold air bottled up near the polar regions (as seen in the past 60 days)... but a weaker Polar Vortex will become less concentrated near the polar regions and will become elongated and may even split into several smaller vorticies (as seen in the current pattern)...these smaller vorticies tend to move away fron the polar region and this allows higher pressures to settle in near the polar and arctic regions (yet to be seen). As higher pressures take hold near the pole... lower pressures and Arctic air are transported southward via the smaller vorticies that once were a strong polar vortex.

Strong Polar Vortex
 
Weak Polar Vortex




There is also a direct relationship between the AO and the NAO due to the NAO being measured in close vicinity to the Arctic region. When stratospheric warming occurs lower pressures are generally replaced with higher pressures in the Arctic regions. This usually means some type of blocking occurs in the high lattitudes of the NAO region due to these higher pressures. When this blocking pattern occurs the colder temperatures of the Arctic are forced southward into the eastern United States by a buckle in the jet stream caused by this blocking pattern that is the negative NAO/AO.


To illustrate just how related the NAO and AO are.. here is a graph showing the fall readings of the AO and NAO indicies. Notice how they behave in a very similar fashion to each other




Hopefully this little writeup will help somebody get a better understanding of how the Polar Vortex is the most important feature regarding a cold and snowy pattern here in the eastern United States. I have been watching this feature becoming weaker and displaced here on our side of the globe lately... this and the recent changes in modeling of the AO indice is a VERY good sign that the NAO/AO could be headed to a more conducive value for us winter wx lovers this season... only time will tell.

Persistent Polar Vortex

Good evening.. its December and it sure feels like it outside also. As long as the circumpolar vortex is positioned over northeastern North America its going to be seaonably to unseasonably cold over the eastern US overall. Any forecast that tells you there will be longterm warm spells including teleconnections and/or model graphics should be taken very lightly and with a huge grain of salt. This feature is currently controlling our weather and doesnt look to let up anytime soon. 

GFS at Day 8

Is Winter Over?

I wanted to talk a little about the pattern of the last 45-50 days. The fall/winter pattern that has developed is very unusual and is not behaving in any form or fashion the way it should. During October you had a raging negative PNA which in theory should have torched us...but we come out tempwise well below normal for that month. During the month of November the NAO and AO went positive... but the southeast managed to score an anomalous snow storm in November.

The Arctic oscillation (AO) is raging positive and at near record levels...but as you can feel it's still decently cold outside. On top of all that we are in a La Nina ENSO state... but yet there is a very active and visible El Nino like subtropical Jet stream. Despite La Nina conditions that say we should be warm and dry... we have actually been more cold and wet. We have been able to stay near or below normal despite unfavorable teleconnection indices and a pesky little southeast ridge..also there seems to be an abundance of strong cutoff lows this fall/winter.

Those that say winter is in trouble are totally looking way too much at numbers and teleconnection indices. They're not taking synoptics and verified data into account. As we get closer to a more climatalogical favored time period for winter weather... I see no reason why there wont be nice winter events with plenty of cold air. This fall/winter so far has been very wet compared to most and there has already been two snow events pretty far south for this time of year. We're getting closer to the real winter season here and when we have a nice arctic airmass in place I can totally see one of those big bowling ball cutoff lows dumping snow in a very widespread fashion despite a positive AO/NAO if that is still the case.

Our winter will happen...it's just not going to happen the way we have gotten used to it happening the last two years.