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Mid to Late May 2019 Severe Threats


Quincy
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5 minutes ago, lokee said:

Very light returns are popping up to the NW and to the SW of Okc. Looks much like what happened earlier this morning at this point.

You should anticipate this throughout the day. WAA regime storms, owing to intense low-level moisture advection into the area. Some of them later on may be able to become surface-based and become tornadic. 

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24 minutes ago, jojo762 said:

Current VAD at KFDR shows some pretty significant lower level backing above 6Kft... anybody happen to know if previous models had been showing VBV in the morning around 15Z?

Mesoanalysis shows S/SSE flow at 700mb in the area, but it veers to SW just to the west.

4E179FDF-BA00-4A4E-99FA-B7F971EEE2E9.thumb.jpeg.358f8e85f0f4b53610ab58b9cfbe3111.jpeg

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9 minutes ago, Upper Level LOL said:

MCD for what will be the first watch of the day. Wording makes it sound like a PDS watch is at least possible if not probable

 

 

mcd0698.gif.e1c38b4e8e8c64ce1b323a1e5f5bda14.gif

Mesoscale Discussion 0698
   NWS Storm Prediction Center Norman OK
   1041 AM CDT Mon May 20 2019

   Areas affected...portions of northwest TX...TX Panhandle...and
   western OK

   Concerning...Severe potential...Tornado Watch likely 

   Valid 201541Z - 201815Z

   Probability of Watch Issuance...95 percent

   SUMMARY...A tornado watch will likely be needed by 1pm CDT.  Storm
   initiation is expected as early as 1-2pm along the dryline.

   DISCUSSION...Visible satellite imagery shows the initial stages of a
   bubbling cumulus field across the Texas South Plains from near
   Midland northward to Lubbock.  Late morning surface observations
   show south-southeasterlies with rapid moisture advection occurring
   with dewpoints rising to near 70 degrees F near the Low Rolling
   Plains.  Despite the scattered low cloud cover, additional heating
   and moistening will contribute to extreme buoyancy (4000-5000 J/kg
   MLCAPE) developing by early-mid afternoon east of a sharping dryline
   in parts of northwest and west TX.  The aforementioned theta-e
   increase and weak large-scale forcing will likely lead to storms
   explosively developing during the 1pm-3pm period.  

   Strong and veering low-level winds beneath very strong deep-layer
   wind fields will likely result in sickle-shaped hodographs over the
   TX Panhandle and western OK this afternoon.  0-1km SRH around 250
   m2/s2 coupled with the extreme buoyancy will favor long-track and
   potentially violent tornadoes with the strongest storms.  Giant hail
   (3-4+ inches in diameter) will be possible.

   Farther south, tornadoes and very large hail are possible with any
   supercells that develop near the Permian Basin.

   ..Smith/Hart.. 05/20/2019

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...OUN...SJT...LUB...AMA...MAF...
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PDS Tornado Watch coming for W and C OK by 1-2pm CDT - https://www.spc.noaa.gov/products/md/md0699.html

 

mcd0699.gif.5f88b96b46a7da84f061968bf7c38750.gif

 

 Mesoscale Discussion 0699
   NWS Storm Prediction Center Norman OK
   1117 AM CDT Mon May 20 2019

   Areas affected...southwest into central OK...western north-central
   TX

   Concerning...Severe potential...Tornado Watch likely 

   Valid 201617Z - 201845Z

   Probability of Watch Issuance...95 percent

   SUMMARY...A Particularly Dangerous Situation Tornado Watch will
   likely be needed for portions of central and western OK. 
   Observational trends and short-term model guidance suggest a watch
   being issued during the 1pm-2pm period.

   DISCUSSION...Visible satellite imagery shows a bubbling cumulus
   field over western north-central TX into southwest and south-central
   OK.  Rapid moisture advection is occurring late this morning with
   surface dewpoints rising into the lower 70s over southern OK. 
   Upwards of 4000 J/kg MLCAPE is expected by early to mid afternoon
   across western and central OK with intensifying wind profiles.  

   Short-term model guidance appears to have a reasonable depiction of
   free warm sector initiation occurring over southwest and
   south-central OK during the 2-3pm period.  The observational trend
   in visible satellite imagery showing more pronounced bands of low
   cloud cover ---perhaps indicative of horizontal convective rolls
   and/or low-level confluence zones is supportive evidence for this
   model-based depiction.  The expectation is for storms to develop on
   the northern half of these cloud features with explosive supercell
   development likely thereafter.  Forecast soundings show a very rare
   combination of intense low-level SRH, very moist boundary, and
   extreme buoyancy.  As such, the risk for strong to violent tornadoes
   appears to be increasing later this afternoon into the early
   evening.

   ..Smith.. 05/20/2019

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...OUN...

 

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ESOSCALE DISCUSSION 0699  
NWS STORM PREDICTION CENTER NORMAN OK  
1117 AM CDT MON MAY 20 2019  
  
AREAS AFFECTED...SOUTHWEST INTO CENTRAL OK...WESTERN NORTH-CENTRAL  
TX  
  
CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY   
  
VALID 201617Z - 201845Z  
  
PROBABILITY OF WATCH ISSUANCE...95 PERCENT  
  
SUMMARY...A PARTICULARLY DANGEROUS SITUATION TORNADO WATCH WILL  
LIKELY BE NEEDED FOR PORTIONS OF CENTRAL AND WESTERN OK.   
OBSERVATIONAL TRENDS AND SHORT-TERM MODEL GUIDANCE SUGGEST A WATCH  
BEING ISSUED DURING THE 1PM-2PM PERIOD.  
  
DISCUSSION...VISIBLE SATELLITE IMAGERY SHOWS A BUBBLING CUMULUS  
FIELD OVER WESTERN NORTH-CENTRAL TX INTO SOUTHWEST AND SOUTH-CENTRAL  
OK.  RAPID MOISTURE ADVECTION IS OCCURRING LATE THIS MORNING WITH  
SURFACE DEWPOINTS RISING INTO THE LOWER 70S OVER SOUTHERN OK.   
UPWARDS OF 4000 J/KG MLCAPE IS EXPECTED BY EARLY TO MID AFTERNOON  
ACROSS WESTERN AND CENTRAL OK WITH INTENSIFYING WIND PROFILES.    
  
SHORT-TERM MODEL GUIDANCE APPEARS TO HAVE A REASONABLE DEPICTION OF  
FREE WARM SECTOR INITIATION OCCURRING OVER SOUTHWEST AND  
SOUTH-CENTRAL OK DURING THE 2-3PM PERIOD.  THE OBSERVATIONAL TREND  
IN VISIBLE SATELLITE IMAGERY SHOWING MORE PRONOUNCED BANDS OF LOW  
CLOUD COVER ---PERHAPS INDICATIVE OF HORIZONTAL CONVECTIVE ROLLS  
AND/OR LOW-LEVEL CONFLUENCE ZONES IS SUPPORTIVE EVIDENCE FOR THIS  
MODEL-BASED DEPICTION.  THE EXPECTATION IS FOR STORMS TO DEVELOP ON  
THE NORTHERN HALF OF THESE CLOUD FEATURES WITH EXPLOSIVE SUPERCELL  
DEVELOPMENT LIKELY THEREAFTER.  FORECAST SOUNDINGS SHOW A VERY RARE  
COMBINATION OF INTENSE LOW-LEVEL SRH, VERY MOIST BOUNDARY, AND  
EXTREME BUOYANCY.  AS SUCH, THE RISK FOR STRONG TO VIOLENT TORNADOES  
APPEARS TO BE INCREASING LATER THIS AFTERNOON INTO THE EARLY  
EVENING.  
  
..SMITH.. 05/20/2019  

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47 minutes ago, jojo762 said:

Most of the 12Z CAMs caved to the HRRR and depict numerous discrete supercells across the high risk area later this afternoon. Buckle up. Scary day evolving for OK and TX.

Even the NAM NEST has caved a bit.  At this point, i would discount that solution anyway since it has very poorly handled MCS development/movement earlier in the day.

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AY 1 CONVECTIVE OUTLOOK    
NWS STORM PREDICTION CENTER NORMAN OK  
1126 AM CDT MON MAY 20 2019  
  
VALID 201630Z - 211200Z  
  
...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS FROM PARTS OF  
NORTHWEST TEXAS AND THE EASTERN TEXAS PANHANDLE TO WESTERN AND  
CENTRAL OKLAHOMA...  
  
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF  
EASTERN NEW YORK AND NEW ENGLAND...  
   
..SUMMARY  
  
AN OUTBREAK OF TORNADOES, SOME POTENTIALLY LONG-TRACK AND VIOLENT,  
IS EXPECTED TODAY INTO THIS EVENING OVER PORTIONS OF NORTHWEST TEXAS  
INTO WESTERN AND CENTRAL OKLAHOMA.  MORE ISOLATED BUT STILL  
POTENTIALLY DANGEROUS SEVERE WEATHER, INCLUDING TORNADOES AND  
DESTRUCTIVE WINDS AND HAIL, IS POSSIBLE IN SURROUNDING PARTS OF  
TEXAS, OKLAHOMA, KANSAS, AND ARKANSAS.  
   
..SOUTHERN PLAINS  
  
A TORNADO OUTBREAK IS FORECAST TO UNFOLD THIS AFTERNOON AND EVENING  
ACROSS PARTS OF NORTHWEST TX AND WESTERN/CENTRAL OK.  MOISTURE  
CONTINUES TO STREAM NORTHWARD ACROSS THE REGION, WITH DEWPOINTS IN  
THE 70S YIELDING VERY HIGH AFTERNOON MLCAPE VALUES OF 3000-5000  
J/KG.  MEANWHILE, SHEAR PROFILES ARE ALSO RAPIDLY INCREASING AS A  
50-60 KNOT SOUTHERLY LOW-LEVEL JET STRENGHENS ACROSS THE AREA.  THIS  
IS LEADING TO A RARE COMBINATION OF EXTREME INSTABILITY AND LARGE  
HODOGRAPHS AS DEPICTED ON FORECAST SOUNDINGS THROUGHOUT THE REGION.  
  
GIVEN THE WEAK CAPPING INVERSION, STRONG LOW-LEVEL THETA-E  
ADVECTION, AND APPROACHING LARGE-SCALE FORCING, ALL SIGNS POINT TO  
THE DEVELOPMENT OF NUMEROUS INTENSE SUPERCELLS THIS AFTERNOON ACROSS  
THE MDT AND HIGH RISK AREAS.  ANY STORM THAT PERSISTS IN THIS  
ENVIRONMENT WILL POSE A RISK OF STRONG TORNADOES, VERY LARGE HAIL,  
AND DAMAGING WINDS.  THE CORRIDOR OF GREATEST CONCERN, INCLUDING A  
THREAT OF LONG-TRACK AND POTENTIALLY VIOLENT TORNADOES, WILL EXTEND  
FROM THE SOUTHEAST TX PANHANDLE INTO WESTERN AND CENTRAL OKLAHOMA.  
  
MULTIPLE ROUNDS OF SEVERE STORMS ARE EXPECTED TO AFFECT THESE AREAS,  
WITH NEW STORMS FORMING THIS EVENING OVER WEST TX AND SPREADING  
ACROSS NORTH TX AND MUCH OF OK OVERNIGHT.  THESE STORMS WILL  
MAINTAIN A RISK OF LARGE HAIL, DAMAGING WINDS, AND ISOLATED  
TORNADOES THROUGH THE NIGHT IN SOME AREAS.  
   
..NORTHEAST STATES  
  
RELATIVELY STRONG HEATING IS OCCURRING OVER NEW ENGLAND AND EASTERN  
NY, WHERE A MOIST AND MODERATELY UNSTABLE AIR MASS IS PRESENT.   
SCATTERED AFTERNOON THUNDERSTORMS ARE EXPECTED TO FORM IN THIS AREA,  
AND SPREAD EASTWARD TOWARD THE NEW ENGLAND COAST DURING THE LATE  
AFTERNOON.  STEEPENING LOW LEVEL LAPSE RATES AND WESTERLY FLOW ALOFT  
WILL PROMOTE A RISK OF GUSTY/DAMAGING WINDS AND SOME HAIL IN THE  
STRONGER CELLS.  
  
..HART/KARSTENS.. 05/20/2019  

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