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Dec. 26th-27th Severe Events


Quincy

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An active pattern continues with what looks like another late day/evening event over portions of Texas and vicinity Saturday, followed by a continued threat further east on Sunday.

 

Low pressure is forecast to eject from the Rio Grande into Texas late Saturday, in response to an amplifying trough over the southern Rockies/northern Mexico. Low-level winds out of the south-southeast to southeast will have no problems advecting warm, moist air into much of Texas. The NAM/GFS/Euro all show SBCAPE reaching 1000-2000 J/kg (NAM is even more robust) by late-day.

 

Substantial height falls during the second half of the day will be accompanied by favorable mid-level lapse rates across much of Texas. The best overlap of shear/instability looks to target central to North Texas.

 

Like other events over the past couple of months, the timing is not ideal, nor does the limited amount of daylight help matters. While the NAM shows some convection over North Texas and Oklahoma late in the afternoon, the signal for more robust convection doesn't show up until overnight. Any early storms would probably have more of a hail threat than anything, given lapse rates, but into early evening, I suspect that damaging winds and perhaps a tornado or two could also develop.

 

Through the night, a squall line will likely form over West/central Texas and spread east. Any tornado threat will hinge heavily upon storm mode, as any discrete storms out ahead of the line would have the greatest tornado potential. Even still, damaging winds and brief, embedded tornadoes could accompany the line as well.

 

Given poor instability, the severe threat further north into southern/southeastern Oklahoma appears minimal, although I suppose a few damaging wind gusts could impact that area as well.

 

The threat shifts into East Texas into Sunday morning and based on the latest high resolution guidance, particularly the 12z 4km NAM, this could feature an enhanced risk of tornadoes.

 

The surface low is forecast to occlude in northeastern Texas during the afternoon, maintaining a stout, backed flow in the low-levels. Storm mode will be important here, as a tendency toward storms merging into a squall line could mitigate the tornado threat with time. The threat, based on current guidance, appears maximized from East Texas into far southeastern Oklahoma, southwestern Arkansas and western Louisiana.

 

The setup reminds me of January 24-26, 2012. The 25th was associated with an outbreak of tornadoes from East Texas into the Lower Mississippi Valley, largely within a long, wavy squall line. The caveat is that this event features profiles that appear more saturated and lapse rates look modest at best by Sunday. 

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Environment in East-Central TX will be impressive tomorrow per 18Z NAM. If any storms are able to be discrete/semi-discrete and maintain supercellular structures, possibly could see a few tornadoes. Perhaps even an isolated strong tornado, but that threat is pretty conditional.

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Holy smokes at this wording from FWD. Should say that if supercells continue developing later on with increasing deep layer wind fields from what they already are (18z FWD sounding was nasty), things could get ugly.

 

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE FORT WORTH TX
208 PM CST SAT DEC 26 2015

.DISCUSSION...

WITH A TORNADO WATCH IN EFFECT FOR ALL OF NORTH AND CENTRAL
TEXAS...WILL KEEP THE FORECAST DISCUSSION FOCUSED ON THE MAIN
THREATS ASSOCIATED WITH THE UPPER LEVEL STORM SYSTEM APPROACHING
FROM THE WEST.

SEVERE WEATHER THREAT: THE MAIN WINDOW OF OPPORTUNITY FOR SEVERE
STORMS IS THIS AFTERNOON THROUGH OVERNIGHT TONIGHT...PRIMARILY
ALONG AND SOUTHEAST OF A COLD FRONT MOVING SLOWLY SOUTHEAST ACROSS
THE REGION.

FOR THIS AFTERNOON AND EVENING: THE 18Z FWD RAOB INDICATED OVER
2000 J/KG OF SURFACE BASED CAPE IN PLACE OVER THE REGION...WITH NO
SIGNIFICANT CAP IN PLACE INHIBITING CONVECTION. DEEP LAYER AND
LOW-LEVEL SHEAR PROFILES ARE SUPPORTIVE OF SUPERCELL THUNDERSTORMS
CAPABLE OF PRODUCING TORNADOES. THE 18 UTC FWD RAOB NUMBERS RANK
HIGHLY IN THE PARAMETER SPACE SUPPORTIVE OF SIGNIFICANT TORNADOES
ACCORDING TO THE STORM PREDICTION CENTERS SEVERE WEATHER
ENVIRONMENT CLIMATOLOGY. AS A RESULT...THINK THAT SUPERCELL
THUNDERSTORMS CAPABLE OF PRODUCING TORNADOES WILL POSE A
SIGNIFICANT THREAT TO THE REGION THROUGH THIS EVENING. THE ONLY
MISSING INGREDIENT THAT WOULD SUPPORT A MORE WIDESPREAD SEVERE
WEATHER OR TORNADO OUTBREAK IS STRONG LIFT OVER THE REGION. LIFT
IS GENERALLY WEAK AND LACKS FOCUS...HOWEVER THE ENVIRONMENT IS
UNCAPPED. EVEN WEAK LIFT MAY BE ENOUGH FOR SCATTERED SEVERE
STORM/SUPERCELL DEVELOPMENT ACROSS THE REGION THROUGH THIS
EVENING. A TORNADO WATCH REMAINS IN EFFECT THROUGH 8 PM FOR ALL OF
NORTH AND CENTRAL TEXAS AS A RESULT. ASSUMING SUPERCELL
THUNDERSTORMS CONTINUE TO DEVELOP IN THIS
ENVIRONMENT...SIGNIFICANT TO VIOLENT TORNADOES ARE POSSIBLE. THE
TORNADO THREAT MAY DIMINISH LATE THIS EVENING AFTER SEVERAL HOURS
OF COOLING...THOUGH THE SEVERE WEATHER THREAT WILL LIKELY PERSIST
ALONG AND SOUTHEAST OF THE COLD FRONT.
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SEVERE WEATHER STATEMENT

NATIONAL WEATHER SERVICE FORT WORTH TX

606 PM CST SAT DEC 26 2015

 

TXC113-139-270045-

/O.CON.KFWD.TO.W.0146.000000T0000Z-151227T0045Z/

ELLIS TX-DALLAS TX-

606 PM CST SAT DEC 26 2015

 

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 645 PM CST FOR NORTH

CENTRAL ELLIS AND CENTRAL DALLAS COUNTIES...

    

AT 605 PM CST...A CONFIRMED LARGE AND EXTREMELY DANGEROUS TORNADO WAS

LOCATED OVER OVILLA...OR NEAR GLENN HEIGHTS...MOVING NORTHEAST AT 35

MPH.

 

THIS IS A PARTICULARLY DANGEROUS SITUATION.

 

HAZARD...DAMAGING TORNADO. 

 

SOURCE...WEATHER SPOTTERS CONFIRMED TORNADO. 

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TXC113-139-270045-

/O.CON.KFWD.TO.W.0146.000000T0000Z-151227T0045Z/

ELLIS TX-DALLAS TX-

614 PM CST SAT DEC 26 2015

 

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 645 PM CST FOR NORTH

CENTRAL ELLIS AND CENTRAL DALLAS COUNTIES...

    

AT 612 PM CST...A CONFIRMED LARGE AND EXTREMELY DANGEROUS TORNADO WAS

LOCATED OVER DESOTO...MOVING NORTH AT 40 MPH.

 

THIS IS A PARTICULARLY DANGEROUS SITUATION.

 

HAZARD...DAMAGING TORNADO. 

 

SOURCE...WEATHER SPOTTERS CONFIRMED TORNADO. 
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