Test-Euro ability to prdct SVR WX Tue/Wed post Arctic front

[Ed Mahmoud]

Usually, when I see strong 850 mb flow from the South ahead of a cold front, and srong winds with a Westerly component aloft, I think severe weather is at least a good chance. Has worked pretty well, so far.


The one bug, the Arctic front, per the Euro, will be halfway into the Gulf just two days prior, and real return flow starts 24 hours or less before this event. So, will the Arctic airmass have modified enough to allow thunderstorms?

As Tonto says, Qemosabe?






That might be an interesting system for places like Kansas and Oklahoma, strong temperature change and a variety of weather.

[Ed Mahmoud]

New Euro a little faster



PSU e-Wall reveals good 850 mb relative humidities, but low 700 mb RH, and Southwest winds. Besides questions about how quickly Canadian airmass can recover, also a question of capping.


But that is why we test these things, I guess.

[Ed Mahmoud]

ECMWF web page shows 50 to 60 knot 850 mb jet in Northwest Texas and Oklahoma Tuesday at 6 am, while the PSU e-Wall depiction of the model shows the 10ºC 850 mb isotherm approaching Houston with relative humidity in excess of 90%.



Now, the 24 hour times steps make it hard to be certain, but perhaps dewpoints approaching 60ºF and a 50 knot LLJ will meet somewhere near/North of SETX later in the day for some interesting early Winter convection.




GFS shows the lifted index barely going negative Tuesday afternoon, but I'm a glass helf full kind of guy.


The winter weather before that here in HOU looks unlikely, but if it does get down to 26ºF like Joe Bastardi says, well, that'll be something, and both the GFS and NAM show about an inch of precip with Friday's storm in BOS and NYC, and while GFS suggests a change to rain in NYC, both models show snow in BOS, and with 850 mb temps below -10ºC at BOS on both models, and upward velocities of 20 microbars per second, I think BOS may get 15 inches of snow.

Note: My late Grandmother was from the Boston area, and when she passed, we took her back to Marshfield, MA, where she was born, for burial. While my first baseball game was the Yankees at Shea Stadium (no, not Yankee Stadium), Catfish Hunter pitching against the White Sox, my second baseball game was at Fenway Park, as Grandma lived on the subway line in North Quincy.


My family moved to Texas in 1980, while I was still young enough to avoid the horrible New York accent. My older sister, God bless her, sounds like Fran Drescher.

[Ed Mahmoud]

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0313 AM CST FRI DEC 19 2008

VALID 221200Z - 271200Z

...DISCUSSION...
PRIMARY FOCUS OF THE PERIOD WILL BE ON AN EAST-ADVANCING UPPER
TROUGH THAT APPEARS LIKELY TO CROSS THE ROCKIES/CENTRAL STATES EARLY
NEXT WEEK. HOWEVER...CONSIDERABLE UNCERTAINTY EXISTS BETWEEN THE 00Z
ECMWF AND 00Z GFS/GEFS WITH THE TIMING OF THIS TROUGH AND
CORRESPONDING SURFACE FEATURES. REGARDLESS...AS THE UPPER TROUGH
GENERALLY SHIFTS EASTWARD AND A SURFACE HIGH SPREADS ACROSS THE
EASTERN STATES...AN INCREASE IN TSTMS WILL BE A DISTINCT POSSIBILITY
ACROSS THE ARKLATEX/LOWER MISSISSIPPI VALLEY/MID-SOUTH REGION WITHIN
A MOISTURE RETURN REGIME ON DAY 5/TUESDAY AND DAY 6/WEDNESDAY.
SUFFICIENT MOISTURE/INSTABILITY AND AMPLE VERTICAL SHEAR MAY SUPPORT
A RISK OF SEVERE TSTMS ACROSS THIS REGION DAY 5/TUESDAY AND DAY
6/WEDNESDAY. HOWEVER...AFOREMENTIONED MODEL VARIABILITY AND
UNCERTAINTIES REGARDING MOISTURE RETURN TIMING/QUALITY PRECLUDES A
SEVERE OUTLOOK AT THIS TIME.

..GUYER.. 12/19/2008

[Ed Mahmoud]

Todays outlook- almost, not quite, a risk area...

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0358 AM CST SAT DEC 20 2008

VALID 231200Z - 281200Z

...DISCUSSION...
00Z ECMWF AND 00Z GFS/GEFS ARE IN RELATIVELY GOOD GENERAL AGREEMENT
WITH THE OVERALL PATTERN THROUGH THE POST-CHRISTMAS WEEKEND. THE
INITIAL FOCUS WILL BE ON AN EAST-ADVANCING UPPER TROUGH THAT WILL
LIKELY CROSS THE ROCKIES/CENTRAL STATES EARLY NEXT WEEK ON DAYS 4/5
TUESDAY AND WEDNESDAY. IN THE WAKE OF A FRONTAL INTRUSION INTO THE
GULF OF MEXICO THIS WEEKEND...A MODIFIED GULF AIRMASS SHOULD RETURN
RELATIVELY QUICKLY AHEAD OF PLAINS CYCLOGENESIS...WITH AN INCREASE
IN TSTMS LIKELY ACROSS THE ARKLATEX/LOWER MISSISSIPPI
VALLEY/MID-SOUTH THROUGH TUESDAY/WEDNESDAY. ACROSS THIS
REGION...SUFFICIENT MOISTURE/MODEST INSTABILITY AND AMPLE VERTICAL
SHEAR SUGGESTS A SEVERE RISK FOR DAY 4/TUESDAY INTO DAY
5/WEDNESDAY...ALTHOUGH QUESTIONS REGARDING THE TIMING/QUALITY OF
MOISTURE RETURN PRECLUDES A 30% DAY-1 EQUIVALENT SEVERE RISK AT THIS
TIME.