Severe weather Dec 22-23

[EF-5bigj]

It looks like there could be a severe weather Dec 22-23 I'm not going to say it will be a tornado outbreak but that could happen. Although the media might just be overhyping it...

[WeatherGuesser]

Not good!



NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CST TUE DEC 22 2015

VALID 231200Z - 241200Z

...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF THE MID-SOUTH
AND TN VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ENH FROM PARTS
OF THE LOWER GREAT LAKES REGION TO THE CNTRL GULF COAST...

...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLGT FROM PARTS
OF THE LOWER GREAT LAKES REGION TO THE CNTRL GULF COAST...

...SUMMARY...
THE POTENTIAL FOR SEVERE THUNDERSTORMS WILL EXTEND FROM THE CENTRAL
GULF COAST TO THE LOWER GREAT LAKES REGION ON WEDNESDAY INTO
WEDNESDAY NIGHT. THE GREATEST POTENTIAL FOR SEVERE THUNDERSTORMS IS
FORECAST FROM PORTIONS OF THE MID-SOUTH REGION TO THE TENNESSEE
VALLEY...WHERE TORNADOES...SOME POSSIBLY SIGNIFICANT...ALONG WITH
DAMAGING WINDS AND HAIL WILL BE POSSIBLE.

...SYNOPSIS...

WITHIN A BELT OF BROADLY CYCLONIC MID-LEVEL FLOW COVERING MUCH OF
THE WRN TWO-THIRDS OF THE CONUS...A SHORTWAVE TROUGH IS FORECAST TO
QUICKLY PROGRESS FROM THE SRN GREAT PLAINS TO THE GREAT LAKES
REGION. AS THIS OCCURS...A SFC CYCLONE WILL DEVELOP NEWD FROM THE
CNTRL GREAT PLAINS TO LAKE SUPERIOR...WITH A STRONG LLJ IN THE WARM
SECTOR ATTENDANT TO THE SFC CYCLONE. THIS WILL ENCOURAGE INLAND
FLUXES OF GULF-MODIFIED MOISTURE...WITH A BROAD CORRIDOR OF 60S SFC
DEWPOINTS BECOMING ESTABLISHED ACROSS THE SERN QUARTER OF THE CONUS
EXTENDING AS FAR N AS THE OHIO VALLEY. THE WRN EXTENT OF THE RICHER
MOISTURE WILL BE MARKED BY A BOUNDARY EXTENDING SWWD FROM THE
AFOREMENTIONED SFC LOW TO S TX.

...CNTRL GULF COAST TO THE OHIO VALLEY...

AS THE BROAD WARM/MOIST SECTOR BECOMES ESTABLISHED FROM PORTIONS OF
THE GREAT LAKES REGION TO THE CNTRL GULF COAST AND COINCIDES WITH
AMPLE DEEP SHEAR...A LONG-DURATION/SPATIALLY EXTENSIVE SVR RISK WILL
EXIST THROUGH THE D2/WED PERIOD. MULTIPLE CORRIDORS OF STRONG TO SVR
TSTMS WILL BE LIKELY ACROSS THE WARM SECTOR...FOCUSED IN A VARIETY
OF REGIMES. DCVA PRECEDING THE SHORTWAVE TROUGH AND RELATED
DESTABILIZATION WILL ENHANCE TSTM ACTIVITY FROM PARTS OF THE MID-MS
VALLEY TO PORTIONS OF THE LOWER GREAT LAKES AND OHIO VALLEY
REGION...WHERE BUOYANCY WILL BE RELATIVELY MARGINAL.
MEANWHILE...AMPLE LOW-LEVEL MOISTURE CHARACTERIZED BY LOWER/MIDDLE
70S SFC DEWPOINTS CURRENTLY RESIDES OFF THE GULF COAST. GIVEN
ANTICIPATED NWD TRANSPORT OF THE RICH MOISTURE...AT LEAST ISOLATED
SVR TSTMS WILL BE POSSIBLE SWD TO THE GULF COAST THROUGH THE PERIOD.

THE OVERLAP OF STRONGER DEEP ASCENT PERIPHERAL TO THE SHORTWAVE
TROUGH...AND MLCAPE OF 500-1250 J/KG AIDED BY SFC DEWPOINTS AROUND
63-66F...IS FORECAST TO EXIST FROM PARTS OF THE LOWER MS VALLEY TO
THE TN VALLEY AND VICINITY DURING PEAK HEATING. WITH AT LEAST
POCKETS OF INSOLATION SUPPORTING STEEPENING LOW-LEVEL LAPSE RATES
ACROSS THIS AREA...AND AN INFLUX OF MODESTLY STEEP MID-LEVEL LAPSE
RATES...DIURNAL SUPERCELL DEVELOPMENT WILL BE MORE LIKELY IN THIS
REGION. THIS WILL BE AIDED BY 50-60 KT OF DEEP SHEAR ORIENTED WITH
AT LEAST SOME ORTHOGONAL COMPONENT TO THE SFC BOUNDARY. WITH 60-70
KT OF H7 FLOW ABOVE 45-55 KT OF H85 FLOW...LOW-LEVEL SHEAR WILL BE
ADEQUATE FOR TORNADOES...SOME POTENTIALLY SIGNIFICANT. DMGG WIND
GUSTS AND HAIL MAY ALSO ACCOMPANY THIS ACTIVITY. SVR-TSTM POTENTIAL
WILL BE MORE ISOLATED FARTHER S TOWARD THE GULF COAST AS DEEP ASCENT
WILL BE MORE LACKING...THOUGH STRONGER INSTABILITY WILL BE AIDED BY
RICHER LOW-LEVEL MOISTURE IN PROXIMITY TO THE COAST.

THE SVR TSTM POTENTIAL -- INCLUDING RISK FOR TORNADOES AND DMGG
WINDS -- WILL SPREAD EWD/ENEWD ACROSS THE RISK AREAS THROUGH WED
NIGHT. SVR TSTM POTENTIAL MAY LAST WELL INTO THE OVERNIGHT HOURS
FROM THE TN VALLEY SWD...WHERE NOCTURNAL GAINS IN MLCINH WILL BE
LIMITED BY THE RETURNING LOW-LEVEL MOISTURE.

..COHEN.. 12/22/2015

[WeatherGuesser]

They say Day 2, but mention 12/22 which is today, so I guess there is a time boundary somewhere. Maybe 8AM? I can never figure out the Z times for 'Effective'. Maybe this kicks off later today into the overnight and tomorrow?

Code: Select all

Day 2 Risk   Area (sq. mi.)   Area Pop.   Some Larger Population Centers in Risk Area
ENHANCED   63,549   6,613,600   Memphis, TN...Nashville, TN...Huntsville, AL...Clarksville, TN...Murfreesboro, TN...
SLIGHT   303,395   35,520,807   Indianapolis, IN...New Orleans, LA...Atlanta, GA...St. Louis, MO...Cincinnati, OH...

[WeatherGuesser]

I wish they'd just use Eastern Time, or maybe Central Time since SPC is there.

VALID 231200Z - 241200Z

12Z is Noon tomorrow? So, this would be 12/23 0600 Central to 12/24 0600?

[Ntxw]

UTC (universal) time is basically a 24 hour clock.

0z is 6pm
6z is midnight
12z is 6am
18z is Noon

After 23z (5pm) it goes back to 0z or 6pm

Increments of 6hours so just convert

01z is 7pm..2z is 8pm..3z is 9pm etc

These conversion I used central standard time(winter), you would up an hour for daylight savings time (summer) for the time change as UTC doesnt move.

[EF-5bigj]

The hatched area is 30% although could go up I suppose.

[psyclone]

This looks like a significant event. I wouldn't be shocked if an upgrade to moderate risk happens. Dr Forbes from TWC has high tornado probs. Western and middle TN, Eastern AR, Northern MS and AL...among others really need to be on alert for what looks to be a substantial cold season SVR WX outbreak.

[EF-5bigj]

Yesterday D.Forbes said he was very concerned about violent,long-tracked tornadoes in those the hatched area.

[Alyono]

To be fair, Forbes has generally overstated the threats this year. NWS has been more spot on. The lack of a moderate has me thinking his TORCON may be 3 too high. Maybe a 4 out of 10 instead of 7

[EF-5bigj]

I've been watching James Spann's coverage he said it could be a high impact event. My local weather isn't concerned for my area really a strong storm or two on Wed.

[WeatherGuesser]

ENH expanded. I'm in it now.

[psyclone]

To be fair, Forbes has generally overstated the threats this year. NWS has been more spot on. The lack of a moderate has me thinking his TORCON may be 3 too high. Maybe a 4 out of 10 instead of 7

Forbes previous 7 torcon numbers this year were 5-9 and 5-16, both of which were prolific svr wx days.

[EF-5bigj]

Stay safe I'm in the slight risk but it seems like N MS and N AL have a history of strong/violent tornadoes.

[WeatherGuesser]

I have other things to do tomorrow. I'd rather not be staring at radar.

[Alyono]

usually, on high end outbreaks, like Forbes is advertising, the NWS also has at least a moderate out by now. Something may be missing from this. Wonder if it is simply the dew points will be lower that we would see in a springtime setup is what may keep a lid on things.

This is not my specialty so I am only speculating

[EF-5bigj]

My local weather says there isn't a lot of confidence in a outbreak all over the area. He said there are a lot of peramiters that have to come into place.

[EF-5bigj]

Hmmm the SPC has the enhanced risk father up north then before.

[WeatherGuesser]

Hoping for an all out total bust.

NOBODY needs this now.

[EF-5bigj]

Hoping for an all out total bust.

NOBODY needs this now.

I don't need this but Dixie Alley is being Dixie Alley

[WeatherGuesser]

FARTHER N...THE STRONGEST FORCING FOR ASCENT WILL BE MAXIMIZED
ACROSS MO/IL DURING THE AFTERNOON AS THE UPPER WAVE TRACKS NEWD
ACROSS THE REGION. PRIMARY UNCERTAINTY HERE IS THE DEGREE OF
DESTABILIZATION CAN OCCUR IN THE WAKE OF THE AFOREMENTIONED EARLY
PRECIPITATION...ESPECIALLY WITH A COOL/MODIFIED AIR MASS IN PLACE.
HOWEVER...A CONDITIONAL THREAT FOR A COUPLE TORNADOES MAY EXIST
NEAR/E OF THE SFC LOW GIVEN VERY STRONG LOW-LEVEL SHEAR.

If that's MetSpeak for 'it might not be too bad if we get rain early in the day to cool things off', I'm all for it. Don't why they can't just use English.