Texas Winter 2012-2013

[orangeblood]

thanks for posting that image NDG. A classic textbook upper air pattern to deliver extreme cold down into the southern plains....Building big highs over western Canada along with the polar vortex positioned just right to force these highs down the spine of the Rockies. That SE ridge could be icing on the cake as it would cause a heck of a fight (winter storms) to break out along the boundary. Slow clap for that ensemble run!!

[Portastorm]

:uarrow: thanks for posting that image NDG. A classic textbook upper air pattern to deliver extreme cold down into the southern plains....Building big highs over western Canada along with the polar vortex positioned just right to force these highs down the spine of the Rockies. That SE ridge could be icing on the cake as it would cause a heck of a fight (winter storms) to break out along the boundary. Slow clap for that ensemble run!!

The one thing that puzzles me, and NDG I think you brought this up the other day, the PNA is predicted to remain negative through 1/20. Yet, we continue to see the modeling suggest a very positive PNA pattern developing. I realize the teleconnection indices forecasts are sometimes flawed ... but I wonder if this would be a case where the other teleconnections overwhelm the PNA and turn it positive. That lack of a positive PNA still concerns me.

[NDG]

:uarrow: thanks for posting that image NDG. A classic textbook upper air pattern to deliver extreme cold down into the southern plains....Building big highs over western Canada along with the polar vortex positioned just right to force these highs down the spine of the Rockies. That SE ridge could be icing on the cake as it would cause a heck of a fight (winter storms) to break out along the boundary. Slow clap for that ensemble run!!

Yeap, somebody in the deep south could get a nasty ice storm and snow event where the cold is deep enough with that set up.

[Portastorm]

Now here's a meteogram you don't see too often for Austin, Texas ... heh, .52 of ice pellets?!



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[NDG]

:uarrow: thanks for posting that image NDG. A classic textbook upper air pattern to deliver extreme cold down into the southern plains....Building big highs over western Canada along with the polar vortex positioned just right to force these highs down the spine of the Rockies. That SE ridge could be icing on the cake as it would cause a heck of a fight (winter storms) to break out along the boundary. Slow clap for that ensemble run!!

The one thing that puzzles me, and NDG I think you brought this up the other day, the PNA is predicted to remain negative through 1/20. Yet, we continue to see the modeling suggest a very positive PNA pattern developing. I realize the teleconnection indices forecasts are sometimes flawed ... but I wonder if this would be a case where the other teleconnections overwhelm the PNA and turn it positive. That lack of a positive PNA still concerns me.

As you may know you don't really need a positive PNA for a 1040mb+ Arctic high to slide down east of the Rockies along the Plains down to TX, which in my opinion could still be a possibility before all is set and done before the end of the month.

[Snowluvr]

The weather channel said they expect the southeast to be spared from any any significant cold air in the long range. it's done this many times where it spreads to about Texarkana and you wind up having a 20-30 degree difference in about a 100 mile distance to the east. If this happens, should make it more likely Texas and Arkansas get some snow or ice

[Portastorm]

Actually, while doing some research now on negative PNAs and Arctic Outbreaks, I just came across a pretty good read on this subject and speculation on the month ahead. I recommend folks check this out:

http://theweathercentre.blogspot.com/

[Ntxw]

With regards to the SSW and other factors, I have some questions (to Ntxw):

1. What values was the AO during January and then into February 1985? A link to past AO records?
2. I read on the weather centre's blog with its excellent in-depth analysis on the coming cold talking mostly about the SSW, that the Polar Vortex has to remain in some form to prevent the atmosphere from becoming "chaos"...what does that actually mean?

Link to Fantastic Polar Vortex Collapse News: http://theweathercentre.blogspot.ca

I can only find links to monthly average AO values. Haven't had any luck finding daily values, I suppose those with -2SD's or lower probably had some extreme daily's.

http://www.cpc.ncep.noaa.gov/products/p ... scii.table

I do not fully understand SSW yet, so I'm not sure what that means either. It's greatest role is to predict the AO, everything else depends on patterns in order to move the cold. Putting the possible cold snap on the SSW probably is not the best thing to do. I've tried to put out evidence of the many reasons why the pattern has been changing (SOI crash, AO's correlation from October to December to the rest of winter, snow cover, Aleutian low etc) and that these players have been set in motion whether by force or coincident to potentially deliver and SSW is just one of them.

The one thing that puzzles me, and NDG I think you brought this up the other day, the PNA is predicted to remain negative through 1/20. Yet, we continue to see the modeling suggest a very positive PNA pattern developing. I realize the teleconnection indices forecasts are sometimes flawed ... but I wonder if this would be a case where the other teleconnections overwhelm the PNA and turn it positive. That lack of a positive PNA still concerns me.

The AO is forecasted to go -5SD's below normal. That will overwhelm any other signal. With the -EPO on it's side, unstoppable. We don't really want a very +PNA anyway, rockies ridge will slide everything to our east. We benefit mostly from the PNA near neutral between the west and east. It's best to say the core of the cold will head down the west and plains. The other signals will eventually force a transient +PNA and the cold may spread eastward from there slowly

[orangeblood]

Portastorm - With a pattern such as this, a simple way I've looked at the PNA index value is to give me an idea of where the upper level ridge axis is aligned. The more positive a PNA value gets the more the ridge axis moves into the interior of Western North America - not good for the southern plains as it would direct the core of the cold into the eastern US. I've noticed that a neutral to slightly positive PNA value (less than 1 STD above) has given Texas some of it's greatest Arctic Outbreaks - I'm assuming that this is due to the ridge axis being aligned directly along the west coast or slightly off the coast rather than the interior.

The EPO is a good indicator of how long the cold will last (Rex Block) while the PNA usually coordinates where the cold air will be directed. Both indices are measured a little differently so you need to look at both to give you a better picture of what's evolving.



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[SaskatchewanScreamer]

Quit it! Do NOT hope, dream, or pray for cold.........because if we get the FULL MONTY of Old Man Winter I WILL be sending him down and he is NOT a pretty sight. He is OLD, MEAN and UGLY and he will be your worst nightmare!!!

Please DO NOT tempt him!

No use posting this in this thread, I did and had posts beginning with "No Offence" a few times . What I don't get is any negative response is never pointed at you...they must be used to you .

If we were looking at anything in the normal winter range of temps I wouldn't care but the -50's And one map that they gleefully put up had the -70's (if my shell shocked brain remembers that correctly). I just can't see those temps being good for any of us (up North we will certainly suffer but we are prepared for those temps....now if we have already cooled Texas down with the minor winter temps we have sent their way what would the above ones do??????

Now it will be a race between me and Nick to see who gets to Jamaica first.

It'll be a race between how fast you can put the fire wood in the stove and how cold the house will get . I haven't checked the Canadian thread yet but I have a feeling Nick is more then not okay with this .

Actually we never get as cold as Saskatchewan so go ahead and feel free to leave ... Looking at the models... the cold will not be as strong by the time it comes here.

I think SS knows this, referring to just very cold weather bothering you more because even if its not -50ºC in Montreal, you still wouldn't like the coldest your region can give you.

[Portastorm]

Learn things around here every day! I've always held an incorrect assumption that a positive PNA was almost necessary for Arctic outbreaks, forgetting that we have seen some severe Arctic outbreaks with a negative PNA and a La Nina pattern. The dialogue this morning and subsequent research reminds me that a positive PNA essentially places a ridge-trough pattern over the CONUS. If the ridge is too far east, we in Texas get mild and dry. The East Coast, of course, gets cold and wet. Sure these are generalities ... but the point is that a the teleconnection indices predictions of a negative PNA don't necessarily preclude this pattern from unfolding. Thanks all!

Guess those PWC mets better spend more time in research and less time with the Grey Goose.

[NDG]

Learn things around here every day! I've always held an incorrect assumption that a positive PNA was almost necessary for Arctic outbreaks, forgetting that we have seen some severe Arctic outbreaks with a negative PNA and a La Nina pattern. The dialogue this morning and subsequent research reminds me that a positive PNA essentially places a ridge-trough pattern over the CONUS. If the ridge is too far east, we in Texas get mild and dry. The East Coast, of course, gets cold and wet. Sure these are generalities ... but the point is that a the teleconnection indices predictions of a negative PNA don't necessarily preclude this pattern from unfolding. Thanks all!

Guess those PWC mets better spend more time in research and less time with the Grey Goose.

That's exactly right, most times you guys in TX don't want a PNA ridge too far east.

[Cyclenall]

I can only find links to monthly average AO values. Haven't had any luck finding daily values, I suppose those with -2SD's or lower probably had some extreme daily's.

http://www.cpc.ncep.noaa.gov/products/p ... scii.table

I do not fully understand SSW yet, so I'm not sure what that means either. It's greatest role is to predict the AO, everything else depends on patterns in order to move the cold. Putting the possible cold snap on the SSW probably is not the best thing to do. I've tried to put out evidence of the many reasons why the pattern has been changing (SOI crash, AO's correlation from October to December to the rest of winter, snow cover, Aleutian low etc) and that these players have been set in motion whether by force or coincident to potentially deliver and SSW is just one of them.

Great, thanks for the reply and the link. I too think of the SSW as the main item that could drive the cold outbreak even though its not exactly the best way to look at things.

Actually, while doing some research now on negative PNAs and Arctic Outbreaks, I just came across a pretty good read on this subject and speculation on the month ahead. I recommend folks check this out:

http://theweathercentre.blogspot.com/

That link really is moving around the block quick, I posted it just a hour or so before you did. Its the go-to place to read daily on this cold coming.

[Ntxw]

I think the remote chance of the rex block "pop" in the epo has become possible. GFS continues to trend with delivering a big high (1047 today along the US/Canadian) while not (yet) what I think it will be, the model is giving in slowly. It does not get any better for something big in the making than how the models have trended.

[CYCLONE MIKE]

Just got home from work and trying to play catch up. What's going on with the possible outbreak? Looking less likely now, models backed off, or are they just going off one run from last night? Our nws discussion said this about it...

REGARDING THE END OF THE WEEK AND WEEKEND...MODEL SOLUTIONS HAVE
SOFTENED ON AMPLITUDE AND INTEGRITY OF COLD AIR ADVECTION WITH
NEXT LONG WAVE. PROSPECTS OF WINTRY WEATHER SEEM LESS LIKELY BASED
ON LATEST MODEL SOLUTIONS.

[Ntxw]

REGARDING THE END OF THE WEEK AND WEEKEND...MODEL SOLUTIONS HAVE
SOFTENED ON AMPLITUDE AND INTEGRITY OF COLD AIR ADVECTION WITH
NEXT LONG WAVE. PROSPECTS OF WINTRY WEATHER SEEM LESS LIKELY BASED
ON LATEST MODEL SOLUTIONS.

Which forecast area? They may be talking about an individual storm/event rather than the broad based pattern sypnotics. The models have trended more amplified for North America. I'm not sure any model really showed any kind of wintry event for Louisiana thus far.

[jerryh421]

I'm guessing by where the models are placing the cold air, southeast Texas won't see much of a cold snap?

[gboudx]

REGARDING THE END OF THE WEEK AND WEEKEND...MODEL SOLUTIONS HAVE
SOFTENED ON AMPLITUDE AND INTEGRITY OF COLD AIR ADVECTION WITH
NEXT LONG WAVE. PROSPECTS OF WINTRY WEATHER SEEM LESS LIKELY BASED
ON LATEST MODEL SOLUTIONS.

Which forecast area? They may be talking about an individual storm/event rather than the broad based pattern sypnotics. The models have trended more amplified for North America. I'm not sure any model really showed any kind of wintry event for Louisiana thus far.

Mike is in Gonzales so that's LIX - Baton Rouge/NO.

[BigB0882]

I never understood those discussions for our area of LA. Next weekend had never been progged to be very cold to begin with and the possible severe cold outbreak is more than a week away, for sure.

[Ntxw]

Thanks gboudx, yeah after reading their discussion they may be talking about the second southern plains system. That system is more likely to bring severe weather to Louisiana than snow or ice. Behind that system will be the first polar/arctic front likely aimed at the plains, but by far is not the period we are looking at.

We can start to see the the PV slowly begin settling into Hudson Bay. Notice the cold air pool around it