2008-09 Texas Winter Weather Thread

[cctxhurricanewatcher]

NWS San Angelo joining NWS OU (Norman) in noticing a potential Arctic front. First NWS in Texas to note it.

ALSO...THE GFS AND ECMWF IS ADVERTISING A
POSSIBLE VERY COLD PATTERN WHICH INCLUDES A POSSIBLE ARCTIC COLD
FRONT MOVING SOUTH ACROSS WEST CENTRAL TEXAS IN THE DEC 13 TO DEC
16 TIME FRAME. THERE IS STILL A LOT OF UNCERTAINTY THIS FAR
OUT...HOWEVER THIS POSSIBLE SCENARIO NEEDS TO BE CLOSELY WATCHED

[jasons2k]

SJT is usually one of the first offices to speak up.

Don't quite get why they need to "closely" watch it though. Arctic fronts don't mean a whole lot in WC Texas. They're used to cold weather out there, unlike us down in Houston.

[vbhoutex]

I've even seen Frank Billingsley at Channel 2 refer to the possibility of a trans-siberian express(with graphics no less) coming in next weekend. He mentioned it is all the buzz on many weather websites now. Wonder if he read S2K???

[zaqxsw75050]

I've even seen Frank Billingsley at Channel 2 refer to the possibility of a trans-siberian express(with graphics no less) coming in next weekend. He mentioned it is all the buzz on many weather websites now. Wonder if he read S2K???

I am pretty sure he is talking about khou forum. One of the poster work there.

Speaking of khou, a great post by wxman57 on there:

Usually the 18Z GFS isn’t worth much, but I do see that the upper-level pattern is beginning to match what the European is forecasting for around the 17th, and each GFS run has been consistent with the 500mb flow lately. Sharp ridge axis into Alaska, east-west trof across the northern U.S. with cross-Polar flow dumping Arctic air east of the Rockies. We’ve seen this setup many times in the past. In a classic error, the GFS identifies the 500mb pattern correctly but makes the mistake of developing a low along the eastern slopes of the Rockies then drives the Arctic air back to the north on the 18th. I have some MRF charts from 1995, I believe, with a very similar error. The GFS had the Arctic front moving north through Kansas but it was actually well off the Texas coast. The GFS just can’t handle this pattern, particularly at the surface. The upper levels may still be ok.

I recommend reading the McFarland paper on the patterns which led to major Arctic outbreaks in Texas:
http://www.srh.noaa.gov/ssd/techmemo/tm88.htm

The pattern predicted by both the GFS and EVMWF in about 10 days is a classic McFarland pattern of a vortex over Baffin Bay, east-west trof axis across northern U.S. and a ridge axis building into the Gulf of Alaska. This drives Arctic air across the Pole and into Canada then the U.S.

I think that the signals are getting stronger for a major Arctic air intrusion lee of the Rockies around the 15th-17th. Hard to say just how cold it might get. Unlike 1983, there isn’t a deep snow pack in the Central and Northern Plains yet. Once the air crosses into Canada over the next week we may have a better idea how cold it might get down to the Gulf coast. I wouldn’t be surprised if such a pattern brought temps into the low 20s to inland areas along the coast. Could easily be colder, depending on the airmass that comes down. Way too early to speculate about any threat of freezing/frozen precip. But the trof orientation might well support post-frontal precip. Areas at greater risk of freezing/frozen precip would be north of here – Dallas into Oklahoma. Maybe northern LA and AR.

This event is in the range of the GFS when it sometimes sees things clearly. Over the coming week, I expect that the GFS may well lose the event, particularly at the surface. It may have problems with the upper flow, too. This typically happens in the 3-9 day range prior to the event – the mid range. Within 72 hours, the GFS should start to catch on again, though it’ll likely still be too slow with the cold air and way too warm with temps. So beware.

[Portastorm]

And speaking of the McFarland signature . . . once again, the European (Saturday, 0z run) is showing a classic "McFarland" at about 240 hours.

[srainhoutx]

And speaking of the McFarland signature . . . once again, the European (Saturday, 0z run) is showing a classic "McFarland" at about 240 hours.

Yep Portastorm, it's looking "classic". Hold Lucy back.

[HouTXmetro]

But 10 days out? I wouldn't count on it. Plenty of time for things to change.

[Ed Mahmoud]

Hmmm, an East-West oriented trough near the Canadian border, with Northerly flow North of it, and zonal flow below. I was just re-reading the McFarland paper yesterday...

As shown in Figure 4, the 500 mb patterns during the 1951 and 1962 Arctic outbreaks were very similar; a deep polar vortex over Baffin Bay, a major trough over the northern United States with an east-west trough line, zonal flow south of the trough line and northerly flow from a high amplitude ridge north of the trough line. The events preceding these patterns were also very similar.

From the breakdown of a high-latitude short wave omega-type block in the long wave ridge, the trough associated with the eastern low moved southward, intensifying while maintaining a general east-west orientation. The combination of the ridge aloft and surface radiative cooling facilitated the development and maintenance of the surface anticyclone, which also began to move southward under the northerly flow aloft. In the four days from 5 Jan to 9 Jan 1962, the surface anticyclone built from a 1025 mb central pressure over the Bering Straits to a 1060 mb high over Alberta.

In both cases, the omega block opened up as the leading trough line moved southward. The closed high circulation of the block became joined with the full latitude long wave ridge over the western coast and the southward moving trough line became linked to the deep low over Baffin Bay.

Another key feature was the cyclogenesis associated with the developing system. In each case, pronounced cyclogenesis occurred as the low occupying the mean long wave trough position over the U.S. was ejected. In January 1962, the surface low deepened from 1006 mb central pressure to 980 mb in a 24-hour period with the cyclogenesis.

Cyclogenesis did not occur with the southward moving trough. A consequence of a lack of cyclogenesis was that the cold air was not deflected eastward from its southward trajectory (Means, 1948). The history of the 500 mb and surface patterns from the first appearance of the block for the 1962 outbreak is presented in Figure 5 and the 500 mb sequence for the 1951 outbreak is presented in Figure 6.

Consistency check- seeing the Euro forecast 500 mb from 2.5 days apart for about the same time period.




Close, but I liked the old forecast better...

[KatDaddy]

Joe B stated he sees shades of 1983 in the ensembles.

[srainhoutx]

Joe B stated he sees shades of 1983 in the ensembles.

One concern with the 1983 analog is the fact that it was a once in fifty year or so event. With that said, things do look interesting to say the least. I still remember the ice that formed in the shallows in what is now Barbours Cut near Morgans Point after 5 days below freezing.

[jinftl]

Similarities between the CPC Outlook and the model run below?



From the CPC Discussion:
FOR THE WEEK 2 PERIOD MODEL SOLUTIONS ARE IN BETTER AGREEMENT COMPARED TO THE
DAY 6-10 PERIOD AFTER THE EXPECTED LONGWAVE PATTERN CHANGE OCCURS. A LONGWAVE
TROUGH BECOMES ESTABLISHED ACROSS THE WESTERN CONUS, WHILE A WEAK RIDGE
DEVELOPS ACROSS THE SOUTHEASTERN CONUS. THIS EXPECTED LONGWAVE PATTERN
YIELDS BELOW NORMAL TEMPERATURES ACROSS MUCH OF THE WESTERN AND CENTRAL CONUS
WITH ABOVE NORMAL TEMPERATURES ACROSS THE SOUTHEASTERN CONUS.

Close, but I liked the old forecast better...

[cctxhurricanewatcher]

NWS San Angelo strikes again.

NEXT WEEKEND...A SIGNIFICANT PATTERN CHANGE CONTINUES TO BE
FORECAST BY THE MODELS BY NEXT WEEKEND. DEEP TROUGHINESS DEVELOPS
ACROSS WESTERN NORTH AMERICA DOWNSTREAM FROM AN AMPLIFYING RIDGE
OVER THE EASTERN PACIFIC THAT NOSES UP INTO THE GULF OF ALASKA.
THIS WILL ALLOW FOR ARCTIC AIR TO PLUNGE SOUTH INTO THE CONUS EAST
OF THE ROCKIES...AND WILL UNDERCUT WEST SOUTHWEST FLOW ALOFT
DOWNSTREAM FROM THE WESTERN CONUS TROUGH. THIS WILL BE A PERFECT
SET UP FOR SHALLOW ARCTIC AIR TO INTRUDE SOUTH INTO THE SOUTHERN
PLAINS INCLUDING TX. THE MAIN QUESTION IS NOT "IF" IT WILL
HAPPEN...BUT "WHEN" IT WILL HAPPEN. THE ECMWF STALLS THE FRONT ALONG
THE RED RIVER VALLEY BY SUNDAY AND KEEPS MY FCST AREA IN THE WARM
AIR. THE GFS APPEARS TO BRING AN INITIAL SURGE IN BY
SATURDAY...BUT THEN BRINGS THE MAIN SURGE IN AROUND MONDAY OF NEXT
WEEK. GIVEN THIS IS AT DAY 7 AND BEYOND...WILL NOT MAKE ANY
SIGNIFICANT CHANGES TO THE CURRENT FCST TODAY. HOWEVER...IF THIS
PATTERN COMES TO FRUITION...SIGNIFICANTLY COLDER AIR AND POSSIBLY
SOME PRECIPITATION...EVEN WINTRY...COULD INTRUDE WEST CENTRAL TX
GOING INTO MID DECEMBER. STAY TUN

[srainhoutx]

NWS San Angelo strikes again.

NEXT WEEKEND...A SIGNIFICANT PATTERN CHANGE CONTINUES TO BE
FORECAST BY THE MODELS BY NEXT WEEKEND. DEEP TROUGHINESS DEVELOPS
ACROSS WESTERN NORTH AMERICA DOWNSTREAM FROM AN AMPLIFYING RIDGE
OVER THE EASTERN PACIFIC THAT NOSES UP INTO THE GULF OF ALASKA.
THIS WILL ALLOW FOR ARCTIC AIR TO PLUNGE SOUTH INTO THE CONUS EAST
OF THE ROCKIES...AND WILL UNDERCUT WEST SOUTHWEST FLOW ALOFT
DOWNSTREAM FROM THE WESTERN CONUS TROUGH. THIS WILL BE A PERFECT
SET UP FOR SHALLOW ARCTIC AIR TO INTRUDE SOUTH INTO THE SOUTHERN
PLAINS INCLUDING TX. THE MAIN QUESTION IS NOT "IF" IT WILL
HAPPEN...BUT "WHEN" IT WILL HAPPEN. THE ECMWF STALLS THE FRONT ALONG
THE RED RIVER VALLEY BY SUNDAY AND KEEPS MY FCST AREA IN THE WARM
AIR. THE GFS APPEARS TO BRING AN INITIAL SURGE IN BY
SATURDAY...BUT THEN BRINGS THE MAIN SURGE IN AROUND MONDAY OF NEXT
WEEK. GIVEN THIS IS AT DAY 7 AND BEYOND...WILL NOT MAKE ANY
SIGNIFICANT CHANGES TO THE CURRENT FCST TODAY. HOWEVER...IF THIS
PATTERN COMES TO FRUITION...SIGNIFICANTLY COLDER AIR AND POSSIBLY
SOME PRECIPITATION...EVEN WINTRY...COULD INTRUDE WEST CENTRAL TX
GOING INTO MID DECEMBER. STAY TUN

Strong wording from the forecaster from San Angelo...

THE MAIN QUESTION IS NOT "IF" IT WILL
HAPPEN...BUT "WHEN" IT WILL HAPPEN.

[southerngale]

I'm waiting for you, Portastorm.

[vbhoutex]

Latest from Jeff Lindner:

Much to speak about this afternoon...major storm system progged for early next week and now growing confidence in a significant arctic air event in about 10 days.

Will tackle the Monday-Wednesday storm first. Polar high will move eastward Sunday allowing weak return flow to develop. Return flow will greatly increase Monday as strong trough develops over the NW US in the polar jet and cut-off low off the CA coast moves E across TX. Sub-tropical jet overhead along with rapid increase in low level Gulf moisture points toward increasing rain chances Monday afternoon with chances peaking Tuesday. Indication continue to suggest a period of severe potential Tuesday as strong polar front and surface low blast into the area with increasing moisture. Details are still working out...but the threat remains for a decent squall line on Tuesday.

Strong polar front blast into the Gulf Tuesday night...will go with gale conditions all waters Tuesday night into Wednesday as surface low cranks up over the MS valley. Expect frequent 45+mph gust over the waters and 35-40mph inland Tuesday night within the post frontal cold air advection regime. Cold polar high builds into the region with clouds clearing out Wednesday morning....ECMWF is slower and does not clear the clouds until late Wednesday. Will go with the coldest guidance on Wednesday with highs only in the lower 50's under sunny skies and 40's if clouds linger. Sub-freezing temps. expected most areas Thursday morning before gradual warm up begins.

Mid December:

I have seen many times before models suggestive of historical cold air outbreaks...but it is rare when the pattern is so apparent in all the guidance and the guidance has remained so consistent. GFS is showing the upper air pattern, but is all messed up at the surface...as is usually the case with shallow dense arctic air. ECMWF continues to show a classic McFarland upper air blocking pattern at 500mb with Polar vortex over Canada backing WSW and sharp intense ridge axis plowing northward through AK into the Arctic Circle. This allows a massive trough to be carved across the entire US with very cold Siberian air mass unleashed across the North Pole and then straight southward into the Gulf of Mexico. Million dollar question is how cold is the air mass when it leaves Siberia and begins its southward treck and how much snow is on the ground over the N and C plains to slow modification of this air mass. Confidence continues to grow that a significant possibly record breaking cold air event will occur in the December 17-22 time frame. Will also need to continue to dabble with the idea of frozen precipitation in the post frontal air mass...

I would say that the next two weeks is going to be interesting to say the least. And colder than I like it!!!!

[Portastorm]

Um .... Portastorm is not here right now. He's frantically searching for his kicking shoes in the hall closet.

[srainhoutx]

Latest from Jeff Lindner:

Much to speak about this afternoon...major storm system progged for early next week and now growing confidence in a significant arctic air event in about 10 days.

Will tackle the Monday-Wednesday storm first. Polar high will move eastward Sunday allowing weak return flow to develop. Return flow will greatly increase Monday as strong trough develops over the NW US in the polar jet and cut-off low off the CA coast moves E across TX. Sub-tropical jet overhead along with rapid increase in low level Gulf moisture points toward increasing rain chances Monday afternoon with chances peaking Tuesday. Indication continue to suggest a period of severe potential Tuesday as strong polar front and surface low blast into the area with increasing moisture. Details are still working out...but the threat remains for a decent squall line on Tuesday.

Strong polar front blast into the Gulf Tuesday night...will go with gale conditions all waters Tuesday night into Wednesday as surface low cranks up over the MS valley. Expect frequent 45+mph gust over the waters and 35-40mph inland Tuesday night within the post frontal cold air advection regime. Cold polar high builds into the region with clouds clearing out Wednesday morning....ECMWF is slower and does not clear the clouds until late Wednesday. Will go with the coldest guidance on Wednesday with highs only in the lower 50's under sunny skies and 40's if clouds linger. Sub-freezing temps. expected most areas Thursday morning before gradual warm up begins.

Mid December:

I have seen many times before models suggestive of historical cold air outbreaks...but it is rare when the pattern is so apparent in all the guidance and the guidance has remained so consistent. GFS is showing the upper air pattern, but is all messed up at the surface...as is usually the case with shallow dense arctic air. ECMWF continues to show a classic McFarland upper air blocking pattern at 500mb with Polar vortex over Canada backing WSW and sharp intense ridge axis plowing northward through AK into the Arctic Circle. This allows a massive trough to be carved across the entire US with very cold Siberian air mass unleashed across the North Pole and then straight southward into the Gulf of Mexico. Million dollar question is how cold is the air mass when it leaves Siberia and begins its southward treck and how much snow is on the ground over the N and C plains to slow modification of this air mass. Confidence continues to grow that a significant possibly record breaking cold air event will occur in the December 17-22 time frame. Will also need to continue to dabble with the idea of frozen precipitation in the post frontal air mass...

I would say that the next two weeks is going to be interesting to say the least. And colder than I like it!!!!

Jeff spelled it out pretty well. Interesting days ahead.

[Ed Mahmoud]

Double Post Alert


Originally posted on EWG's Southern Plains winter thread .

The 00z GFS run looks like it finally may be starting to catch on. It is showing a nice blast of arctic air trying to make it south by early next week. It still looks to hang up the cold air a little too much, not letting it get as far south as it probably will, but this definitely looks better than previous runs. Things could certainly get interesting (and COLD) in about 8-10 days...

180 hrs: http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_180l.gif

192 hrs: http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_192l.gif

204 hrs: http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_204l.gif

216 hrs: http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_216l.gif

228 hrs: http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_228l.gif

That could be a joyous and happy occasion, with 500 mb pattern suggesting a good push of cold air down toward the Canadian border (and hopefully cold, dense air and high pressure does the rest) with SW flow at 500 mb over Texas and precip.
500 mb forecast in 8 days from GFS


I can't remember which pro-met (might be JB, not sure, might be WxMan57 at KHOU forum) who has mentioned the GFS error pattern with shallow cold air producing 500 mb progs that aren't bad but surface features in bad places. Perhaps hour 216 surface map above's cold front in East Texas with 850 mb freeze line Northwest of Dallas and surface freeze line near Dallas is off by a hundred or three hundred miles, and Dallas is into the snow, and the surface freezing line might be approaching Houston with warm air still just above the surface, producing a school and work cancelling ice storm. The kids and I bundled up, slipping around on our icy lawn.


Eternal optimist in me, I guess.

[Portastorm]

The models this morning are a bit muddled as compared to Saturday. Ed has already posted about the 0z GFS, although I contend that the 500mb pattern at 8 days doesn't look "classic McFarland" at all with that upper level low off the Pacific coastline.

The 0z Euro doesn't have that look it had yesterday ... here it is at 192 hrs:



Then at 216 hrs, we lose the sharp ridge axis over Alaska not to mention a more SW-NE trough digging into the West.



All of this to say that what was looking like a slam dunk yesterday . . . doesn't look as guaranteed as a Florida-Oklahoma BCS title game. Granted, it's only one model run, but this weather weenie ain't putting on his kicking shoes just yet. I may have found 'em in that closet though!

Edit update: And to add to at least my confusion, taking a look at the 850mb map (from the DuPage website) for the Euro for 7 days out, it does look like it's about to, or already has, unleased some Arctic air down the east side of the Rockies which would pour down right into Texas. So ... I dunno. Look forward to discussing with y'all today.

[Portastorm]

Several Texas-based NWSFOs this morning are talking now re: next weekend's potential Arctic outbreak.

NWSFO Amarillo says: "MODELS CONTINUE TO INDICATE POSSIBLE COLD AIR INTRUSION NEXT WEEKEND."

NWSFO Lubbock says: "MODELS ARE ALSO STARTING TO HINT AT A VERY STRONG DUMP OF COLD AIR BEYOND
THE END OF THE FORECAST THAT BEARS WATCHING."