Texas winter wx thread (2009-2010)

[Portastorm]

And so it begins ... here is a snippet from the Amarillo NWSFO afternoon forecast discussion:

SOMETHING BREWING ON THE HORIZON...

LATEST GFS AND EURO RUNS ARE IN FAIRLY GOOD AGREEMENT WITH THE NEXT
UPPER SYSTEM THROUGH ABOUT WEDNESDAY. MODELS BEGIN TO DIVERGE FROM
THAT POINT...BUT GIVEN THE GENERAL CONSISTENCY THROUGH EARLY
WEDNESDAY FELT MORE CONFIDENT IN THE SOLUTIONS. AS THE MODELS STAND
RIGHT NOW...THERE APPEARS TO BE SNOWFALL HEADING TO THE PANHANDLES
SOMETIME WEDNESDAY OR THURSDAY. SINCE THERE CAN BE SIGNIFICANT MODEL
CHANGES BETWEEN NOW AND THEN...DECIDED AGAINST HITTING THE SNOW TOO
HARD. IN FACT...GUIDANCE TEMPS REMAIN ABOVE FREEZING DURING THE
EVENT...SO JUST LEFT LIQUID RAIN IN FOR NOW ESPECIALLY SINCE THE BEST
SHOT FOR SNOW CURRENTLY LOOKS TO BE DURING THE DAY 8 TIME FRAME.
BUT...GIVEN THE 1000-500MB THICKNESS FALLING WELL BELOW 540
DAMS...AND SUB 0 850MB TEMPS ENCOMPASSING MUCH OF THE UNITED STATES
NORTH OF INTERSTATE 40...THE AIRMASS APPEARS PLENTY COLD TO SUPPORT
FROZEN PRECIP. SO AT THIS POINT...WILL ONLY OFFER THE TEASER AND
START TO FINE TUNE THE PRECIP TYPE AS THE MODELS IRON OUT THE
DETAILS.

A snippet from NWSFO New Braunfels from this afternoon:

JUST BEYOND THIS FORECAST WEDNESDAY NIGHT AND THURSDAY. THE MODELS SHOW
THIS TO BE THE STRONGEST FRONT YET THIS SEASON WITH SOME 30S
POSSIBLE IN THE HILLS NEAR HALLOWEEN, ALTHOUGH WE SHALL SEE. HAVE
GENERALLY GONE WITHIN A DEGREE OR TWO OF MAV/MEX TEMPERATURES.

And NWSFO Midland/Odessa:

BEYOND THE EXTENDED FCST...GFS IS HINTING AT AN ARCTIC BLAST NEAR
HALLOWEEN...W/THE DGEX AND ECMWF CONSIDERABLY
WARMER.

[srainhoutx]

Got to love the ensembles and the operational GFS today. We shall see, but it is nearing that time of year.

http://weather.unisys.com/gfsx/loop/gfsx_850_loop.html

[snow and ice]

EURO-Ensemble comparison 8-10 day means:

http://www.meteo.psu.edu/~gadomski/ECMW ... tcomp.html

[Ntxw]

Lucy! Well certainly does look like chilly weather is coming way or another lol

[gboudx]

Larry Cosgrove from Houston agrees with this:

http://www.examiner.com/x-3775-Houston- ... iner-email

Next week will see at least TWO major rain events, with the prospect in view for a possible record cold snap during the Halloween weekend. Notice that the equatorial Pacific Ocean has two major tropical cyclones and a large Kelvin wave which are becoming linked to the polar westerlies. Passing so much energy into the northern branch, a large elongated ridge complex will likely build from Alaska. At the same time, the subtropical jet stream (seen clearly on the GOES WEST image) will roll through Florida into the Gulf of St. Lawrence, providing a perfect teleconnection for a deep trough and closed low at 500MB over Ontario. This alignment of features could produce widespread record cold temperatures across much of the U.S., in two sequences between October 28 and November 6.

[msstateguy83]

per the 18z run of the gfs iam not sure iam buying into the coldair mass outbreak
just yet, need to give it several more runs and see if we see any consistency in the
model runs. I wouldnt be to shocked if the earlyer scenario pans out as iam expecting
a very active pattern across the central/southern plains this winter with multiple snow/ice
storm events. I will post more thoughts in the coming days but i did like the 12z run this am
just would like to see more of that v.s. the 18z which painted more of a warmer scenario for
ok/tx region.


edit: i would add after more closer detailed inspection i do see the cold pockets, but they
dont seem like they are going to last long at all per the latest run, also no sign of winter precip
as the 12z run had prev shown... more runs will likely tell the story though...

[Portastorm]

Models are now backing off some on the strength of next week's cold fronts.

The 0z GFS run from this morning (Thursday) no longer shows a full latitude trough rolling through Texas around Halloween. Instead, it shows two fairly significant but less deeper troughs rolling through in two parts: Oct. 29th (180h) and Nov. 2nd (264h).

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/00/fpc.shtml

The Euro is suggesting similar:

http://www.ecmwf.int/products/forecasts/d/charts/medium/deterministic/msl_uv850_z500!Geopotential%20500%20hPa!168!North%20America!pop!od!oper!public_plots!2009102200!!/

[msstateguy83]

I still am holding out some hope for this event as I do fully expect this season
to be very active as I said in my last post and also start earlyer then most
seasons. I would not be surprized to atleast see a widespread snow and or ice event
across portions of oklahoma into northwestern, northcentral tx sometime between
halloween and thanksgiving. I will take a look @ the 12z gfs run later on this
morning and post some other thoughts after reviewing it.

[msstateguy83]

just wanted to add another quick thought could the models now
be under estimateing the whole setup? becouse how often is it we see a huge plunge of cold air like that this early in the season... just a thought... more later...

[Portastorm]

just wanted to add another quick thought could the models now
be under estimateing the whole setup? becouse how often is it we see a huge plunge of cold air like that this early in the season... just a thought... more later...

Some things come to mind here:

1) The GFS is notorious for underestimating the strength and speed of polar fronts as they encroach on the Southern Plains

2) The GFS is notorious for fumbling with pattern changes in the spring and fall

3) The GFS is notorious for capturing events in the long range, losing them in the middle range, then getting closer to being spot on at the short range

4) The Euro is a more trusted model in dealing with fall/winter, in my opinion, but it is not totally infallible.

[srainhoutx]

Sound all too familiar, doesn't it. Larry Cosgrove's discussion yesterday gave some "hints" regarding the problems ahead re: guidance from the WPAC systems. We have seen this before as models struggle with such an active pattern in El Nino years. I suspect we will see guidance flip flop until latching on to a reasonable solution late this weekend. Should make for an interesting fall/winter season for us.

[msstateguy83]

I have posted a graphic i made just my thoughts on overall how this winter is
going to pan out for the tx/ok region, let me know if you agree or disagree. its likely
far from perfect but its best what i can picture at this time.

[msstateguy83]

12Z is coming in after just brushing over it, appears it going back to the colder possibilty for around
nov 6th-7thish with the 32 degree line down to near dallas-fortworth with poss some light winter precip
into western/nwrn tx

MORE DETAIL EDIT:
after looking for this my overall take is expect a MUCH colder halloween then previous years
temps hovering likely between 35-45 across the region some areas might be closer to frzing..
this HAS to be watched closely as the gfs might be under est precip with this system, if thats
the case this could be the first winter storm of the 09/10 season... rightnow i wouldnt be shocked
if highs from oct 31st thru atleast nov 7thish dont get out of the mid 40s as far south as dfw....
iam starting to strongly think the gfs is under est this system from the back/fourth it has done.

if there is going to be any precip out of this system gfs has it over nw tx/western tx into the tx
panhandle region on or around halloween which then again raises my eyebrows more with the ?
trace amounts or major winter storm amounts? time will tell.

[ntxweatherwatcher]

That would not surpise me that Halloween this year is cold, and possible rainy. It is a bummer because we have a big front yard haunt and we always get lots of trick or treaters. Last year we gave out about 40 pounds of candy! If cold and wet holds true, maybe I should scale back on the candy!

[Portastorm]

Um, I'm not seeing what you are seeing with the 12z GFS. I do see some chilly air impacting Texas around Halloween and highs in Austin may only be in the mid and upper 50s with lows in the lower 40s ... maybe not quite as chilly as you seem to be thinking but then a warm-up occurs after Halloween. Dallas would probably have highs in the lower 50s with lows in the upper 30s.

As we have discussed, there will be lots of variability in the model runs and we should be focusing on trends. I think the one clear trend for Texas is to look for a major cooldown around Halloween.

[snow and ice]

The Ensembles still continue to show a fairly sharp trough late next week for the central US. Source region of the air mass will determine how cold it gets.

12z ENSEMBLES;
http://www.meteo.psu.edu/~gadomski/ENSH ... /f192.html

As far as a winter forecast is concerned, I agree with the above posters prognostications with the exception of the Austin area. I think they will be warm and dry this winter while Waco and San Antonio receive record cold and snowfall.

[Portastorm]

As far as a winter forecast is concerned, I agree with the above posters prognostications with the exception of the Austin area. I think they will be warm and dry this winter while Waco and San Antonio receive record cold and snowfall.

He's probably right. The coast will get snow and we'll get cloudy and virga.

[srainhoutx]

As far as a winter forecast is concerned, I agree with the above posters prognostications with the exception of the Austin area. I think they will be warm and dry this winter while Waco and San Antonio receive record cold and snowfall.

He's probably right. The coast will get snow and we'll get cloudy and virga.

And we'll have an Ice Storm. ~Sigh~

[Portastorm]

The Friday morning 0z GFS run is back to a more amplified pattern and full latitude trough passing through the southern Plains on Oct. 29-30th. If this run would verify, AUS would see a low temperature Halloween morning in the mid 30s!!

This is a very cold looking run for sure.



The latest Euro run, however, holds back a lot more energy in the Desert Southwest and is less progressive with the trough.

[srainhoutx]

Interesting disco from Amarillo this afternoon...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AMARILLO TX
342 PM CDT FRI OCT 23 2009

.DISCUSSION...
INITIAL FORECAST CHALLENGE SHOWS UP SATURDAY. LEE SIDE TROUGH
DEVELOPING WILL BRING SOUTH TO SOUTHWEST WINDS BACK TO MOST OF THE
PANHANDLES. THE WARM DOWNSLOPING WIND SHOULD HELP HIGH TEMPS RISE
INTO THE 70S MOST AREAS. HOWEVER...A COLD FRONT WILL BE HEADING THIS
WAY AND PROVIDE ANOTHER SHOT AT PRECIP ON SUNDAY THROUGH MONDAY
MORNING. PREVIOUS MODEL RUNS WERE NOT AS OPTIMISTIC ABOUT PRECIP
CHANCES...AND THE CURRENT GFS IS STILL RUNNING DRY. BUT THE EURO AND
NAM BOTH PULL SOME MID LEVEL MOISTURE INTO THE PANHANDLES AND TRIGGER
A FEW SHOWERS. SO LEFT POPS IN THE FORECAST...BUT PUSHED THE TIMING
BACK TO START SUNDAY MORNING AS OPPOSED TO SATURDAY NIGHT. EXPECTING
COOLER CONDITIONS ON SUNDAY ACROSS MOST OF THE PANHANDLES...WITH
ANOTHER COOL DAY IN STORE MONDAY.

THE NEXT BIG CHALLENGE BEGINS ON TUESDAY AND WEDNESDAY WHEN A DEEP
AND COLD AIRMASS MOVES INTO THE NORTHERN CONUS FROM CANADA. THERE
IS EVEN A SLIGHT HINT THAT THIS IS AN ARCTIC AIRMASS HEADING INTO THE
CONUS...BUT DECIDED AGAINST GOING TOO COLD THAT FAR OUT FOR THE
PANHANDLES. THE OTHER CONCERN IS THE LACK OF CONSISTENCY IN THE
TIMING OF THE NEXT SYSTEM FROM THE GFS TO THE EURO. THE GFS HAS BEEN
MOST CONSISTENT RUN TO RUN...WHILE THE LAST TWO RUNS OF THE EURO ARE
SHOWING A SIMILAR AIRMASS AS THE GFS...WITH THE INCONSISTENCY
INVOLVING TIMING AND LOCATION. SO AS IT STANDS RIGHT NOW...DECIDED
TO TREND CLOSER TO THE GFS. BUT FELT THE GUIDANCE TEMPS WERE FAR TOO
WARM AT THIS POINT. SO COOLED OFF TEMPS WEDNESDAY AND ESPECIALLY
THURSDAY MORNING. THEN KEPT THE COOLER TREND GOING THURSDAY AND
FRIDAY. THERE IS STILL ROOM TO GO COOLER ON THURSDAY IF MODEL TRENDS
CONTINUE ON THEIR CURRENT PATH.

AS FOR PRECIP...THIS WILL BE A CHALLENGE. WITH THE GFS BEING THE
FASTER SOLUTION...IT APPEARS THE COLD AIR WILL HIT DURING THE DAY
WEDNESDAY WITH PLENTY OF UPPER SUPPORT AS THE LOW DIGS SOUTH INTO NEW
MEXICO. THIS COULD BRING SNOWFALL AS EARLY AS WEDNESDAY
EVENING...CONTINUING THROUGH THURSDAY MORNING. ON THE OTHER
HAND...THE SLOWER EURO SOLUTION PAINTS THE LOW OVER ARIZONA WHICH
WOULD KEEP WARMER AIR IN PLACE OVER THE PANHANDLES THROUGH THURSDAY.
THE EARLIEST CHANCE AT SNOWFALL COMING LATE THURSDAY INTO FRIDAY
MORNING. LIKEWISE...THERE IS ROUGHLY A 12 TO 18 HOUR DIFFERENCE IN
FRONTAL PASSAGE TIMING. THE GRIDS DEPICT THE GFS TREND WHICH
INTRODUCES SNOW WEDNESDAY NIGHT INTO THURSDAY MORNING. BASED ON
FORECAST SOUNDINGS...850 MB TEMPS...AND 1000-500MB THICKNESS
VALUES...THIS APPEARS TO BE AN ALL SNOW...OR MAYBE A RAIN SNOW MIX
EVENT WITH A VERY MINIMAL CHANCE FOR ICE.

JJB