Severe weather outbreak AR/LA/OK/TX for November 13th?

[Ed Mahmoud]

12Z GFS shows a pretty intense upper system.

12Z GFS also seems to suggest decent moisture return and some intability by early afternoon.

0Z Euro shows a less pronounced upper feature than the 12Z GFS...

But pretty good low level winds, and decent directional shear between 500 and 850 mb...



Canadian 12Z seems sort of similar to 12Z GFS.

I noticed the 6Z DGEX is quite a bit quicker with the system, so 6 days out, there is still some uncertainty, but a bowling ball style upper low moving through Texas or Oklahoma, assuming quality air returns after the latest cool dry surge into the Gulf, could make for an interesting early to mid week.

[Ed Mahmoud]

Not to honk my own horn too loudly, but I started the 10/18/07 tornado thread on 10/12/07.


I will admit (I can't see it anymore, I didn't photobucket the Euro) the 500 mb Euro forecast 6 days out for that looked better than the current 500 mb Euro, but the GFS and Canadian seem promising.

[RL3AO]

The SPC didn't seem too bullish but we will see what they say in the next couple days.

[Ed Mahmoud]

The SPC didn't seem too bullish but we will see what they say in the next couple days.

Models don't agree either. Relevant snip from HPC afternoon discussion

THERE ARE QUITE A FEW GUIDANCE DIFFERENCES WITH INDIVIDUAL SYSTEMS
THAT OUR BLEND SEEMS TO ADDRESS BUT ONE OF THE MORE STARK
CONTRASTS IS THAT THE 06/12 UTC GFS AND 00/12 UTC CANADIAN AND 00
UTC NOGAPS...BUT NOT THE NEWER 12 UTC RUN...SEPARATE A MORE CLOSED
SRN POLAR CLOSED LOW SUN-WED FROM THE SWRN US SLOWLY EWD INTO THE
S-CENTRAL US. THERE ARE A FEW GFS AND ECMWF ENSEMBLE MEMBERS IN
THIS VEIN BUT OVERALL THIS SEEMS TO BE A LESS LIKELY ALTERNATE
SOLUTION CONSIDERING THE LACK OF A WELL DEFINED AND AMPLIFIED
UPSTREAM MID-UPPER LEVEL RIDGE. THE NEW 12 UTC ECMWF AND UKMET
ALSO STILL OFFER MORE PROGRESSIVE SOLUTIONS.

[CrazyC83]

I'm sensing more the 14th and (yes, once again!) the 15th, as I think this is going to slow down.

14th in the regions listed, 15th farther east in the same areas as October 18th.

[Ed Mahmoud]

Model differences still have SPC saying "Predictability Too Low" on 4-8 day outlook

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0302 AM CST THU NOV 08 2007

VALID 111200Z - 161200Z

THE MEDIUM RANGE MODELS ARE IN BETTER AGREEMENT FOR THIS WEEKEND
SHOWING AN UPPER-LEVEL RIDGE OVER THE MS VALLEY. THIS RIDGE MOVES
EWD TO THE ATLANTIC COASTAL STATES WITH AN OPEN TROUGH DEVELOPING IN
THE ROCKIES BY EARLY NEXT WEEK. THE MODELS DIVERGE SHARPLY AT THIS
POINT WITH THE GFS MOVING A WELL-DEVELOPED UPPER-LEVEL TROUGH INTO
THE PLAINS STATES AND THE ECMWF REMAINING ZONAL ACROSS THE CNTRL AND
NRN STATES. THIS DIFFERENCE IN THE UPPER-LEVEL PATTERN PRESENTS A
LOT OF UNCERTAINTY CONCERNING THE SEVERE POTENTIAL. HOWEVER...IT
APPEARS LOW-LEVEL MOISTURE WILL BE ABLE TO RETURN NWD INTO THE
MID-MS VALLEY THIS WEEKEND. THIS WILL SET THE STAGE FOR THUNDERSTORM
ACTIVITY AS A COLD FRONT MOVES SEWD ACROSS THE CNTRL PLAINS AND
MID-MS VALLEY MONDAY AND TUESDAY AS DEPICTED BY THE ECMWF. IF ENOUGH
INSTABILITY DEVELOPS ALONG THE BOUNDARY...SEVERE THUNDERSTORMS WILL
BE POSSIBLE. HOWEVER...THE TIMING OF THE FRONT AND STRENGTH OF THE
UPPER-LEVEL TROUGH REMAIN HIGHLY UNCERTAIN AND A SEVERE WEATHER
THREAT AREA CAN NOT BE OUTLOOKED ATTM.

..BROYLES.. 11/08/2007

[CrazyC83]

Model differences still have SPC saying "Predictability Too Low" on 4-8 day outlook

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0302 AM CST THU NOV 08 2007

VALID 111200Z - 161200Z

THE MEDIUM RANGE MODELS ARE IN BETTER AGREEMENT FOR THIS WEEKEND
SHOWING AN UPPER-LEVEL RIDGE OVER THE MS VALLEY. THIS RIDGE MOVES
EWD TO THE ATLANTIC COASTAL STATES WITH AN OPEN TROUGH DEVELOPING IN
THE ROCKIES BY EARLY NEXT WEEK. THE MODELS DIVERGE SHARPLY AT THIS
POINT WITH THE GFS MOVING A WELL-DEVELOPED UPPER-LEVEL TROUGH INTO
THE PLAINS STATES AND THE ECMWF REMAINING ZONAL ACROSS THE CNTRL AND
NRN STATES. THIS DIFFERENCE IN THE UPPER-LEVEL PATTERN PRESENTS A
LOT OF UNCERTAINTY CONCERNING THE SEVERE POTENTIAL. HOWEVER...IT
APPEARS LOW-LEVEL MOISTURE WILL BE ABLE TO RETURN NWD INTO THE
MID-MS VALLEY THIS WEEKEND. THIS WILL SET THE STAGE FOR THUNDERSTORM
ACTIVITY AS A COLD FRONT MOVES SEWD ACROSS THE CNTRL PLAINS AND
MID-MS VALLEY MONDAY AND TUESDAY AS DEPICTED BY THE ECMWF. IF ENOUGH
INSTABILITY DEVELOPS ALONG THE BOUNDARY...SEVERE THUNDERSTORMS WILL
BE POSSIBLE. HOWEVER...THE TIMING OF THE FRONT AND STRENGTH OF THE
UPPER-LEVEL TROUGH REMAIN HIGHLY UNCERTAIN AND A SEVERE WEATHER
THREAT AREA CAN NOT BE OUTLOOKED ATTM.

..BROYLES.. 11/08/2007

I think timing is the big issue. There are time differences in the models, as normally expected this far out.

[Ed Mahmoud]

After a wet Spring and Summer, Autumn has been rather dry here in SE Texas. I can do without tornadoes, but a big, loud, windy thunderstorm with frequent, vivid lightning next week wouldn't be all bad, at all.

[CrazyC83]

Models are so split right now that there is a wide variance of potential. GFS doesn't do much as the front will be off balance with a weak low.

[Ed Mahmoud]

The GFS flips every run on whether one big trough will come through, or whether a low will cut off and hang out in the Southwest or Baja California.

[Ptarmigan]

It's kinda dry, so some rain would be welcomed. Local news have 60% chance of rain on Tuesday.

[Ed Mahmoud]

Latest Euro looks like GFS did a few days ago, while GFS continues to flip almost every run. If 12Z Euro pans out, might be an interesting Tuesday in TX & OK

[CrazyC83]

Latest Euro looks like GFS did a few days ago, while GFS continues to flip almost every run. If 12Z Euro pans out, might be an interesting Tuesday in TX & OK

I still think farther east is the more likely place on the 14th and/or 15th. Climatologically speaking, the Midwest and South are far more likely to get severe weather in November due to the clash of the air masses.

Speaking of the 15th, that day seems so infamous for severe weather recently...

[TexasStooge]

This is something to look out for in the next few days.

[CrazyC83]

Models are still badly split. GFS doesn't develop anything (keeping the systems all above 55°N) while NAM delays them and has the low still over West Texas at 0000/13.

[Ed Mahmoud]

Relevant snip from HGX AFD

THE MODELS SEEM TO BE
HAVING A DIFFICULT TIME INITIALIZING THE ALEUTIAN LOW AND STRONG
POLAR JET OVER THE PACIFIC NW. THE INITIALIZATION FOR THE 12Z
RUNS SEEMS TO BE BETTER TODAY. SHORT RANGE MODELS CONTINUE TO
BRING A STRONGER SHORTWAVE TROUGH INTO THE DESERT SW MONDAY AND
THEN INTO W TX ON TUESDAY. THE 12Z GFS AND CANADIAN MODELS SEEM
TO HAVE SOME GOOD AGREEMENT WITH THIS EVOLUTION. THE ECMWF SEEMS
TO DIG THE SHORTWAVE A LITTLE FARTHER SOUTH THAN THESE AND
RESULTS IN A MORE CUTOFF SYSTEM. THE GFS HAS TRENDED TO A MORE
PROGRESSIVE SOLUTION AS HAS THE CANADIAN. THE FORECAST HAS BEEN
TRENDED TOWARDS THESE SOLUTIONS ALTHOUGH HIGHER POPS MAY BE
POSSIBLE TUE/WED. THE GFS/CANADIAN TAKES THE POTENT SHORTWAVE
OVER MUCH OF TX TUE INTO WED WITH HEAVY RAINFALL AND SEVERE
WEATHER POSSIBLE. THE FORECAST WILL STICK WITH MAINLY 40 POPS FOR
NOW JUST IN CASE THE MODELS FLIP AGAIN ON THEIR SOLUTIONS. TUE
LOOKS TO BE THE BEST TIME FRAME FOR ORGANIZED THUNDERSTORM
ACTIVITY WHICH MAY COME TO AN END LATE WED. BOTH MODELS BRING A
STOUT COLD FRONT THROUGH THE AREA DURING THE DAY WED WHICH SHOULD
ALLOW FOR COOLER/MORE SEASONABLE TEMPS FOR THE END OF NEXT WEEK
IN THE EXTENDED FORECAST. FORECAST CONFIDENCE IS A LITTLE HIGHER
WITH SOME BETTER AGREEMENT AMONG THE MODELS. STILL...CONFIDENCE
IS NOT HIGH ENOUGH TO REALLY PUSH THE THREAT FOR SEVERE WEATHER.
IT DOES BEAR WATCHING AS PARTS OF TX COULD BE PRIMED FOR MORE
WIDESPREAD SEVERE WEATHER.

[RL3AO]

It seems like the SPC took a step back today.

...DISCUSSION...
00Z ECMWF/GFS AND MOST MEMBERS OF THE LATEST NCEP-GEFS SUGGEST THAT
THE SRN STREAM UPR LOW THAT DROPS INTO NRN MEXICO EARLY NEXT WEEK
MAY NOT EJECT EWD INTO TX UNTIL AFTER FRIDAY 16 NOV. MEANWHILE...A
SERIES OF MID-LEVEL WAVES MOVING QUICKLY SEWD FROM THE N PAC BASIN
WILL GRADUALLY CARVE OUT A COLD...BUT PROGRESSIVE ERN STATES TROUGH
BY MID-LATE NEXT WEEK FOLLOWED BY MORE OF A ZONAL WNWLY FLOW PATTERN
BY THE WEEKEND. THIS SCENARIO WILL LIKELY SPELL A REINFORCEMENT OF
DRY/STABLE CONTINENTAL POLAR AIR THAT WILL SPREAD QUICKLY SEWD FROM
THE NRN PLAINS/GRTLKS REGION INTO FL AND THE NRN GULF BASIN BY
WEEK/S END. THOUGH A BAND OF SHOWERS/TSTMS WILL ACCOMPANY THE FRONT
ACROSS THE OH/TN VLYS...MID-SOUTH AND PARTS OF THE SRN PLAINS...POOR
MOISTURE/LAPSE RATE RECOVERIES AHEAD OF THE FRONT WILL PRECLUDE ANY
ORGANIZED SVR WEATHER OUTBREAKS.

..RACY.. 11/10/2007

[CrazyC83]

Looks like the low will not develop, and we will get through mid-month without significant activity. However, the GFS now picks up something in the super-long term for Thanksgiving weekend...

The nearest low to potentially bring down a front is forecast to be at about 55°N latitude, and that is too far north to entrench into the Gulf moisture needed (anything above 50°N in November will almost never pick up the moisture needed).