April 14th Severe Weather Discussion and Chase Details

–update 18:37Z – Mesoscale Discussion

ACUS11 KWNS 141834
SWOMCD
SPC MCD 141833
OKZ000-TXZ000-142100-

MESOSCALE DISCUSSION 0425
NWS STORM PREDICTION CENTER NORMAN OK
0133 PM CDT THU APR 14 2011

AREAS AFFECTED…PORTIONS CENTRAL/N-CENTRAL/NE TX…ERN OK.

CONCERNING…SEVERE POTENTIAL…WATCH LIKELY

VALID 141833Z – 142100Z

EXPECT DEVELOPMENT OF SEVERAL POTENTIALLY LONG-LIVED SUPERCELLS
ALONG/AHEAD OF DRYLINE BEGINNING IN 20-22Z TIME FRAME…COVERAGE
INCREASING THROUGH REMAINDER AFTERNOON/EVENING AS ACTIVITY MOVES EWD
TO NEWD.  DAMAGING HAIL IS LIKELY…SOME EXCEEDING 3 INCHES
DIAMETER.  THREAT WILL INCREASE FOR TORNADOES AS TSTMS MATURE AND
MOVE INTO PROGRESSIVELY MORE MOIST/HIGH-SRH AIR MASS…WITH TIME AND
EWD EXTENT.

18Z SFC MESOANALYSIS SHOWS DRYLINE JUST E OF US-81 CORRIDOR IN OK
THEN SWWD ACROSS JACK COUNTY TX…WHERE VIS IMAGERY INDICATES
CONCENTRATION OF DEEP CU.  DRYLINE SHOULD CONTINUE TO MIX/ADVECT EWD
ACROSS I-35 FROM PVJ AREA NWD…BEFORE DECELERATING AROUND 23Z.  TX
DRYLINE SEGMENT SHOULD MOVE EWD TO JUST W OF DFW METROPLEX…NEAR
PRESENT LOCATION OF CONFLUENCE LINE THAT EXTENDS NNEWD FROM HILL
COUNTRY.  DRYLINE MAY SHARPEN FURTHER…GIVEN COMBINATION OF
1. CONTINUING MOST ADVECTION TO ITS E…
2. BACKING 850-MB WINDS EVIDENT PAST COUPLE HOURS IN CENTRAL OK
VWP/PROFILER DATA…AND
3. GEOMETRY OF PRESSURE FALLS OVER KS/OK THAT MAY KEEP SLGT ELY
COMPONENT TO SFC FLOW IN MOIST SECTOR IN CORRIDOR FROM OSAGE COUNTY
SWD TO DUA AREA THROUGH 00Z.

EXPECT CONTINUED STG SFC HEATING…DEW POINTS RANGING FROM UPPER 50S
F IN NRN OK TO MID 60S FROM ADM-ATOKA AREA SWD ACROSS RED
RIVER…AND STEEPENING LAPSE RATES ALOFT.  THIS WILL BOOST MLCAPE TO
2000-3000 J/KG RANGE OVER PORTIONS N TX AND SERN OK BASED ON
MODIFIED 18Z FWD/OUN RAOBS…AND 1500-2000 J/KG NEAR OK/KS BORDER.
MEANWHILE…DEEP-LAYER SHEAR WILL STRENGTHEN…AS ALREADY EVIDENT
WITH LOWERING OF 50-KT MIDLEVEL ISOTACH AT TCU PROFILER.  EFFECTIVE
SHEAR SHOULD INCREASE TO 50-60 KT.  HODOGRAPH SIZE…NOW INDICATING
SOME WEAKNESSES AROUND 1-3 KM AGL…WILL INCREASE MARKEDLY DURING
LATE AFTERNOON AND EARLY EVENING OVER ERN OK…BECOMING POTENTIALLY
FAVORABLE FOR SIGNIFICANT TORNADO PRODUCTION.  STG ORTHOGONAL
COMPONENT OF MEAN WIND AND DEEP-SHEAR VECTORS…RELATIVE TO
DRYLINE…INDICATES STORMS CAN REMAIN DISCRETE FOR AT LEAST A FEW
HOURS AFTER INITIATION.  COVERAGE SWD INTO CENTRAL TX SHOULD BE MORE
ISOLATED/CONDITIONAL.

SRN END OF KS CONVECTIVE ARC REGIME — SEE MESOSCALE DISCUSSION 424
FOR DETAILS — MAY BACKBUILD INTO PORTIONS N-CENTRAL/NERN OK AFTER
ABOUT 21Z AS WELL.

..EDWARDS.. 04/14/2011

…PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT…

ATTN…WFO…SHV…TSA…FWD…OUN…SJT…

LAT…LON  31749881 33009777 34999746 36999738 36959512 34449494
32919559 31549697 31379781 31749881

 

—-updated 18:31Z

Severe Weather Discussion for April 14, 2011.
Issued:  04/14/2011.

Highlights:

– Significant severe weather event today with large tornadoes possible.  Additionally, destructive hail and damaging winds will occur.

Discussion:

Models in good agreement with the evolution of today’s severe weather event.  Dryline has firmed up over Oklahoma City/I-35, as consistently progged by all models.  To the east, dewpoints are in the upper 50s to mid 60s (especially south) and CAPE values above 2500 J/Kg and LIs AOB -7.  As such, it appears the stage is set for a significant severe weather event across eastern Oklahoma.  SPC has hinted at a high risk for southeast sections and we’ll see if they do it.  I think the high risk will be more for overnight tornadoes than coverage but either way, the threat is real and dangerous.

HRRR model consistently ignites storms around 4pm, which has been the going forecast for me since yesterday.  The dryline is likely to move little the next 2-3 hours but in general remain very near I-35.  Once storms ignite and mature, they’ll produce destructive hail.  The initial tornado threat may be reduced due to low level shear but given backed surface flow in eastern Oklahoma, this may be moot.

The most dangerous storms appear to be destined for southeast Oklahoma where activity will remain discrete much longer and well into the night time hours.  In northeast Oklahoma, linear storms should evolve by mid-evening as they race eastward.  HRRR models wants to go linear rather rapidly from Ponca City northward and then no activity south until I-40 at which time there are scattered supercells to the Red River.  Not sure if the break in activity across north-central OK is correct but either way we’re going to commit to that area.

At this juncture, appears Oklahoma City has dodged this one but a severe warn could occur in eastern OK Co if conditions are just right.

Probabilities:

N/A

Chase Status:

Level 1 – leaving at 3pm, target is Wellston.

 

Quick update – dryline is just west of the OKC metro area near Hinton at 17Z.  We may have to shift a little east of our previous target of I-35.  Most models are stalling the dryline right around the OKC metro.

 

Here are a few time sensitive images that show current conditions.  We’re heading out around 3 PM – probably going to hang around OKC until storms initiate.  Storm speed won’t be terrible so we’ll be able to get anywhere quickly.

 

 

 

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