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Quincy

Nov. 16th-17th Severe Event

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Another dip in the jet stream, this time further south than the event on Wednesday, will kick off a threat for severe thunderstorms early in the coming week.

 

While some of the finer details are yet to be ironed out, the overall setup is fairly clear. Upper level trough digs into the Southwest/Four Corners region on Monday, later sparking surface cyclogenesis in the vicinity of the Texas/Oklahoma panhandles. Moist flow from the Gulf of Mexico draws 60F+ dew-points into the southern Plains and Lower Mississippi Valley Monday afternoon/evening as a potent upper level jet rounds the base of the trough.

 

Monday looks to target much of Texas, with the Euro fairly consistent in pegging the threat from central to eastern parts of the state, while the GFS/NAM are somewhat slower/further west and get western parts of the state into the action. The low may be wrapped up enough to drive the severe threat into parts of Oklahoma as well, especially if the system cuts into the central Plains.

 

Guidance has shown a consistent signal of a potent squall line moving from eastern Texas and eastern Oklahoma Tuesday morning, into the Lower Mississippi Valley through the day. Instability appears to be maximized early in the day, followed by a trend for the wind fields to become more unidirectional with time.

 

All severe hazards are possible, particularly late Monday across Texas (perhaps Oklahoma). Damaging winds with flash flooding become the main threats for Tuesday, although embedded tornadoes could occur, particularly early in the day as instability and the strength of the low-level jet are maximized.

 

The GFS also shows a stronger signal of flooding across the Mississippi Valley with this system, but the Euro is more progressive. For what it's worth, the 00z Euro ensembles were more of a compromise, so perhaps the OP Euro is too quick to boot the system out.

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I really like this setup. I'm surprised on how long the instability lasts and even increases throughout the nighttime of Monday. Overall looks like a good setup with the LLJ and the bulk shear being just enough. Only question is morning convection as represented by GFS. 

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Some pretty impressive forecast soundings in the west-central Texas vicinity Monday evening. It's too bad that forcing arrives just a little bit late, as initiation holds off until near or after 00z. Also signs of capping on top of that. Will be interested to see how the convective trend looks overnight Monday into early Tuesday. Could be a rocky ride approaching DFW first thing Tuesday.

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While nothing about Monday in W TX (possibly W OK) is ideal -- instability, hodo shape, or timing -- it's still pretty impressive for the second half of November. Seems like a slight shift in favor of daytime CI along the dryline/CF with this evening's guidance, on average. Should daytime storms initiate, the environment looks favorable for some of the most intense supercells the region has seen this time of year in awhile and a nonzero (although relatively modest) tornado threat.

 

post-972-0-33123900-1447565291_thumb.gif

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Considering the time of year, this could be a pretty good potential. I mean it could be worse, we could be talking about snow in the Panhandle instead.

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While nothing about Monday in W TX (possibly W OK) is ideal -- instability, hodo shape, or timing -- it's still pretty impressive for the second half of November. Seems like a slight shift in favor of daytime CI along the dryline/CF with this evening's guidance, on average. Should daytime storms initiate, the environment looks favorable for some of the most intense supercells the region has seen this time of year in awhile and a nonzero (although relatively modest) tornado threat.

00z 4km NAM shows CI shortly before 00z and keeps storm mode relatively discrete into the first part of the evening. I'm still kind of concerned for DFW in the morning, given increasing moisture return and instability through the overnight. A mess of Tuesday morning commute at the least.

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DAY 2 CONVECTIVE OUTLOOK  

   NWS STORM PREDICTION CENTER NORMAN OK

   1130 AM CST SUN NOV 15 2015

 

   VALID 161200Z - 171200Z

 

   ...THERE IS AN ENH RISK OF SVR TSTMS SRN GREAT PLAINS...

 

   ...THERE IS A SLGT RISK OF SVR TSTMS CNTRL/SRN GREAT PLAINS...

 

   ...THERE IS A MRGL RISK OF SVR TSTMS NEB TO WRN GULF COAST...

 

   ...SUMMARY...

   SEVERE STORMS ARE EXPECTED TO INITIATE ACROSS THE CENTRAL AND

   SOUTHERN HIGH PLAINS LATE AFTERNOON TO EVENING ON MONDAY. AN

   EXTENSIVE SQUALL LINE SHOULD FORM MONDAY NIGHT AND PUSH EASTWARD

   ACROSS PARTS OF OKLAHOMA AND TEXAS. TORNADOES...DAMAGING WINDS...AND

   LARGE HAIL ARE ANTICIPATED.

 

   ...SYNOPSIS...

   AMPLIFIED UPPER TROUGH OVER THE WEST WILL SHIFT ONTO THE HIGH PLAINS

   THROUGH EARLY TUE. POTENT EMBEDDED SHORTWAVE IMPULSE SHOULD

   TRANSLATE THROUGH THE BASE OF THE TROUGH FROM AZ/NM TOWARDS THE WRN

   KS VICINITY. A 100-KT 500-MB SPEED MAX SHOULD DEVELOP ACROSS WRN OK

   BY 12Z/TUE. A DEEP SURFACE CYCLONE IN THE LEE OF THE SRN ROCKIES

   SHOULD GRADUALLY SHIFT INTO CNTRL KS. A PACIFIC COLD FRONT SHOULD

   OVERTAKE THE SRN HIGH PLAINS DRYLINE...ACCELERATING E TOWARDS THE

   I-35 CORRIDOR.

 

   ...SRN/CNTRL GREAT PLAINS...

   PRIMARY CHANGES THIS OUTLOOK ARE TO EXPAND ALL PROBABILITIES

   NWD/SEWD AND ADD A SIGNIFICANT SEVERE AREA. PARTS OF THE REGION

   CENTERED ON THE RED RIVER APPEAR PLAUSIBLE FOR AN UPGRADE TO A

   TORNADO OR WIND-DRIVEN MODERATE RISK IN D1 OUTLOOKS.

 

   WHILE THE RICHEST MARITIME TROPICAL AIR REMAINS ACROSS THE SWRN GULF

   THIS MORNING PER GOES PW IMAGERY...MODIFICATION FARTHER N IN TX IS

   WELL UNDERWAY AND WILL CONTINUE TO INCREASE THROUGH THE D2 PERIOD.

   LOW 60S SURFACE DEW POINTS SHOULD REACH THE WRN OK/KS BORDER BY MON

   EVENING WITH MID 50S TO THE NEB/KS BORDER. TSTM INITIATION IS LIKELY

   BETWEEN 21-00Z AS ROBUST MID-LEVEL HEIGHT FALLS/DCVA OVERSPREAD THE

   DRYLINE. UNCERTAINTY IN THE DEGREE OF DIABATIC SURFACE HEATING AHEAD

   OF THE DRYLINE DOES EXIST AS GUIDANCE VARIES IN THE DEGREE OF

   STRATUS. NEVERTHELESS...EVEN IF HEATING IS LIMITED...STEEPENING

   MID-LEVEL LAPSE RATES WILL SUPPORT WEAK TO MODERATE BUOYANCY. STRONG

   LOW TO DEEP SHEAR WILL YIELD ELONGATED AND ENLARGED HODOGRAPHS

   FAVORABLE FOR SUPERCELLS. THE TEMPORAL WINDOW FOR MAINLY DISCRETE

   CONVECTION SHOULD BE LIMITED TO A FEW HOURS AFTER INITIATION GIVEN

   THE DEGREE OF FORCING AND SURGING OF THE COMPOSITE PACIFIC

   FRONT/DRYLINE. AN INCREASINGLY EXTENSIVE SQUALL LINE IS EXPECTED MON

   NIGHT FROM KS TO TX THAT SHOULD RAPIDLY PROGRESS TO THE I-35

   CORRIDOR OVERNIGHT. ADDITIONAL PRE-SQUALL LINE TSTMS MAY FORM EARLY

   TUE ACROSS PARTS OF CNTRL/ERN TX WITHIN THE RICHLY BUOYANT MARITIME

   TROPICAL AIR MASS.

 

   SETUP SHOULD FAVOR A MULTI-FACETED SIGNIFICANT SEVERE THREAT WITH

   THE TORNADO RISK BEING THE MOST PROMINENT...ESPECIALLY ALONG THE RED

   RIVER. HIGHER-END SEVERE WIND POTENTIAL MAY WEAKEN TOWARDS 12Z/TUE

   OWING TO THE INCREASINGLY MERIDIONAL COMPONENT TO THE MEAN WIND

   FIELDS RELATIVE TO THE SQUALL LINE/FRONT. BUT THIS COULD BE

   COMPENSATED BY RICHER LOW-LEVEL MOISTURE WITH UPPER 60S SURFACE DEW

   POINTS EXPECTED TO REACH THE RED RIVER AND STRENGTHENING FLOW ALOFT.

 

   ..GRAMS.. 11/15/2015

  

 

SPC with strong wording on 1730z outlook. Possible Moderate risk at 06z Day 1.

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18Z 4K/12K NAM both show a pretty volatile setup for monday night... STP of 6-8 at 03Z across W OK. Main question as with every setup in 2015 will be crapvection across the warm sector... As well as if things can stay discrete and not messy. 4K NAM has several decent UH tracks.

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Dr. Forbes has a TORCON of 5 tomorrow. Pretty impressive. Sounds like another good chase day.

The only problem is that storms will likely initiate around sunset, so most of Monday's action will probably happen during darkness.

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The initial development on the 4km NAM looks pretty nasty. And yeah, looks like things will really start around 9PM local time... way past sunset. I'd imagine it's quite rare to have a possible outbreak start this far past sunset. 

 

3MsWkYk.png

BK05WC2.png

 

West OK

iLcI5BI.png

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Yeah, overall the parameters look impressive enough, but chase conditions could be downright bad. Not only is the early onset of darkness an issue, but standard time puts chasers an hour behind too. That's on top of possible issues with the Red River yet again. I've been planning on a chase for a few days now, but I could easily scrap it based on how things look tomorrow morning.

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Paige Burress did some research and found that it is incredibly uncommon to have a severe weather outbreak start so far west in the winter months. We had a few tornadoes back in December of 2012 in the eastern Panhandle. Other than that we haven't had a outbreak in a good ten years during the fall months so far west. A fall event during the night in populated areas not accustomed to either scenario is definitely concerning. Steep lapse rates and the 65+ knot low level jet won't make it difficult to get those winds to mix down to the surface. 

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Paige Burress did some research and found that it is incredibly uncommon to have a severe weather outbreak start so far west in the winter months. We had a few tornadoes back in December of 2012 in the eastern Panhandle. Other than that we haven't had a outbreak in a good ten years during the fall months so far west. A fall event during the night in populated areas not accustomed to either scenario is definitely concerning. Steep lapse rates and the 65+ knot low level jet won't make it difficult to get those winds to mix down to the surface. 

Thankfully it looks like the window for discrete supercells is limited because of how quick it's expected to grow upscale. That's essentially what SPC is saying with the day 1 outlook... when the hodographs enlarge at night, that's when the storm mode is gonna turn linear. Still might get a moderate risk for tornadoes with the 1630z or 20z update if the threat looks big enough during that window of opportunity, IMO

Sxc8j0x.gif

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1205 AM CST MON NOV 16 2015

VALID 161200Z - 171200Z

...THERE IS AN ENH RISK OF SVR TSTMS PARTS OF N-CNTRL TX INTO

CNTRL/WRN OK AND THE ERN TX PANHANDLE...

...THERE IS A SLGT RISK OF SVR TSTMS FOR PARTS OF WRN NEB/KS INTO

MUCH OF OK AND TX...

...THERE IS A MRGL RISK OF SVR TSTMS OVER THE CNTRL PLAINS SWD TO

THE GULF COAST...

...SUMMARY...

SEVERE STORMS ARE EXPECTED TO DEVELOP INITIALLY OVER THE CENTRAL AND

SOUTHERN HIGH PLAINS DURING THE LATE AFTERNOON AND EVENING. AN

EXTENSIVE SQUALL LINE SHOULD FORM TONIGHT AND PUSH EASTWARD ACROSS

PARTS OF OKLAHOMA AND TEXAS. TORNADOES...DAMAGING WINDS...AND LARGE

HAIL ARE ANTICIPATED.

...SYNOPSIS...

A POWERFUL 150 KT JET STREAK WILL MOVE EWD ACROSS NRN MEXICO INTO

SWRN TX DURING THE DAY 1 PERIOD CONCURRENT WITH AN INTENSE MID-LEVEL

TROUGH/LOW PROGRESSING EWD FROM THE 4 CORNERS INTO THE SRN-CNTRL

HIGH PLAINS. A SURFACE LOW IS FORECAST TO DEVELOP OVER THE CNTRL

HIGH PLAINS AND SLOWLY MIGRATE EWD WHILE A DRYLINE WILL EXTEND SWD

THROUGH THE SRN HIGH PLAINS DURING THE AFTERNOON. A PACIFIC COLD

FRONT IS FORECAST TO OVERTAKE THE DRYLINE DURING THE EVENING AND

SURGE EWD ACROSS W TX AND THRU THE OK I-35 CORRIDOR OVERNIGHT.

...SRN AND CNTRL GREAT PLAINS...

THE NWD TRANSPORT OF PARTIALLY MODIFIED GULF MOISTURE ON STRONG

LOW-LEVEL SLY FLOW THIS MORNING FROM S TX INTO W-CNTRL TX AND INTO

THE CNTRL HIGH PLAINS WILL OCCUR AS A SLOW-TO-ABATE SURFACE RIDGE

OVER THE CNTRL GULF COAST STATES ACTS TO PARTIALLY INHIBIT

DESTABILIZATION ACROSS ERN TX INTO ERN KS DURING THE MUCH OF THE

DAY. A NARROWING PLUME OF RICHER LOW-LEVEL MOISTURE WITH NWD EXTENT

WILL PROBABLY RESULT IN SURFACE DEWPOINTS PERHAPS REACHING THE MID

50S OVER NWRN KS TO LOWER 60S SWD TO THE E OF THE DRYLINE IN TX.

STRONG H5 HEIGHT FALLS /IN EXCESS OF 90 M PER 12 HR/ ARE FORECAST TO

INITIALLY OVERSPREAD THE DRYLINE OVER THE NRN TX PANHANDLE AND WRN

KS DURING THE MID AFTERNOON. DESPITE SURFACE DEWPOINTS RANGING FROM

THE LOW-MID 50S OVER SWRN NEB TO UPPER 50S OVER THE NRN TX/OK

PANHANDLE REGION...MID-LEVEL COOLING WILL PROBABLY YIELD UPWARDS OF

250-750 J PER KG MLCAPE. STRONGLY SHEARED AND VEERING WIND PROFILES

IN THE EXIT REGION OF AN APPROACHING 100 KT MID-LEVEL SPEED MAX WILL

SUPPORT A COUPLE OF SUPERCELLS POTENTIALLY CAPABLE OF HAIL/WIND AND

PERHAPS A FEW TORNADOES. INCREASINGLY MERIDIONAL FLOW AND STRONG

DEEP-LAYER FORCING FOR ASCENT WILL FAVOR UPSCALE GROWTH INTO LINE

SEGMENTS.

FARTHER S...SURFACE-BASED INITIATION WILL PROBABLY BE DELAYED UNTIL

THE LATE AFTERNOON. SCTD STORM DEVELOPMENT IS EXPECTED DURING THE

21-00Z PERIOD ALONG THE DRYLINE. AN AXIS OF MODERATE BUOYANCY IS

PROGGED BY MODEL GUIDANCE /1000-1500 J PER KG SBCAPE/ AND STRONG

DEEP-LAYER SHEAR. THE STRONGER UPDRAFTS WILL DEVELOP INTO

SUPERCELLS AND THE INITIAL SEVERE RISK WILL INCLUDE LARGE TO VERY

LARGE HAIL...SEVERE GUSTS...AND ISOLD TORNADOES. DURING THE

EVENING...HODOGRAPHS ARE FORECAST TO ENLARGE /300-500 M2 PER S2

EFFECTIVE SRH/ ALONG WITH A GRADUAL MOISTENING IN THE PBL ACTING TO

TEMPER NOCTURNAL COOLING AND MAINTAIN SURFACE-BASED OR NEAR

SURFACE-BASED BUOYANCY PROFILES ACROSS SRN OK AND WRN N-CNTRL TX.

AT THE SAME TIME...A RAPID PROGRESSION IN UPSCALE GROWTH IS EXPECTED

TO OCCUR AS THE PACIFIC FRONT SURGES E AND STORM MERGERS OCCUR. IT

IS PLAUSIBLE A SEVERE-WIND PRODUCING SQUALL LINE WITH EMBEDDED

BOWS/LEWPS AND MESOVORTICES YIELDS SWATHS OF WIND DAMAGE AS THE WIND

FIELDS INTENSIFY BY MID-LATE EVENING. LESS CERTAIN/LOWER

PROBABILITY IS MAINTAINING CELLULAR MODES FARTHER E THAN ANTICIPATED

AND/OR ADDITIONAL STORMS DEVELOPING AHEAD OF THE LINE WHICH WOULD

PERHAPS FAVOR A GREATER TORNADO RISK. NONETHELESS...A GRADUAL

DECREASE IN BUOYANCY FARTHER E TOWARDS THE ARKLATEX WILL TEMPER THE

THREAT FOR WIND DAMAGE COMPARED TO AREAS FARTHER W.

 

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To add: a meaningful tornado threat should still exist along the squall line well after dark, as well as with any storms that manage to stay ahead of/develop in front of the line. Potentially dangerous situation especially if either of the NAM's solutions were to verify with 1000-2000 J/KG of CAPE, 50-100J/KG of which will be in the lowest 0-3KM, lasting well into the morning hours coinciding with marked low level shear and strong speed shear.

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Other than that we haven't had a outbreak in a good ten years during the fall months so far west. A fall event during the night in populated areas not accustomed to either scenario is definitely concerning.

 

Last time I recall we had a significant after dark situation in the S Plains out of season, it ended tragically. Referring to 2/10/09 here of course. One rogue supercell in the wrong place with the degree of shear available in this setup and we don't have a pretty situation. It's kind of like Dixie has shifted west for a day.

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This looks like an impressive November system.  OK/TX borders back to the east 100 or so miles, including the Red River valley seem to be at the highest risk for Tornadoes.  However, the NAM and GFS, while in disagreement with timing and speed, show pretty impressive shear/helicity values over much of Oklahoma.  Discrete cells could pose a real tornado threat and any squall that develops could see spinups along the leading edge.  I can only remember a couple of other November setups that looked this impressive.  

I hope people are paying attention and aware.  I would suspect 5-7pm discrete cells go up.  What remains a big question is how quickly it goes linear.  That will decrease the threat of significant tornadoes considerably but with the atmosphere primed I'm just not sure if this isn't going to be on the higher end of the current forecast.  

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Latest D2 really upped the wording for tomorrow, given the potential for pre-squall discrete supercells within a very moist and strongly sheared environment.

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Latest D2 really upped the wording for tomorrow, given the potential for pre-squall discrete supercells within a very moist and strongly sheared environment.

1992 may be a good November analog for this event.

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Instability already building in across TX, and making its way in to OK. 500-1000J/KG already... Persistent low-level cloud deck over much of the plains is making insolation negligible across the eastern half of the ENH risk, should burn off at some point I'd think?

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HRRR is picking up on some semi-discrete cells about 2-3 hours before what we thought was the main event. If these cells form, they could be nasty.

odlQGN1.png

There's already initiation and one severe warning in the OK panhandle.

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