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TOR Watch for S MN, N IA, and extreme W WI.

 

http://www.spc.noaa.gov/products/watch/ww0180.html

any idea where SPC got that storm vector from? most of the indications I am seeing says the storm vector will start at 180 and shift eventually to 220 or maybe 230. 260@30 kts just doesn't seem right, unless I am missing something here.

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MESOSCALE DISCUSSION 0698
   NWS STORM PREDICTION CENTER NORMAN OK
   0145 PM CDT SUN MAY 19 2013
  
   AREAS AFFECTED...NRN...CNTRL...AND SRN OK
  
   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
  
   VALID 191845Z - 191945Z
  
   PROBABILITY OF WATCH ISSUANCE...95 PERCENT
  
   SUMMARY...TSTM INITIATION APPEARS INCREASINGLY PROBABLE OVER THE
   NEXT 1-2 HRS ACROSS NRN/CNTRL OK. STORMS SHOULD QUICKLY INTENSIFY
   AND POSE A THREAT FOR VERY LARGE HAIL...DMGG WINDS...AND A FEW
   TORNADOES. A TORNADO WATCH WILL LIKELY BE NEEDED IN THE NEXT HOUR OR
   SO.
  
   DISCUSSION...SFC ANALYSIS FROM 18Z SHOWS A DRYLINE RAPIDLY MIXING
   EWD ACROSS WRN OK...ATTENDANT TO A DEEPENING SFC LOW OVER NWRN
   OK...WITH UPPER 60S TO LOWER 70S F DEWPOINTS WIDESPREAD ACROSS CNTRL
   OK. A REMNANT OUTFLOW BOUNDARY FROM OVERNIGHT CONVECTION REMAINS
   DRAPED ACROSS FAR NRN OK...BUT UNIFORM SLY WINDS WERE NOTED ON BOTH
   SIDES OF THIS BOUNDARY. MEANWHILE...AN INCREASINGLY AGITATED LINE OF
   CU WAS NOTED PRECEDING THE DRYLINE...ORIENTED SW-NE FROM NEAR A 30 E
   CSM TO 15 NW END LINE...WITHIN A ZONE OF WEAK LOW-LEVEL CONVERGENCE.
   THIS AREA APPEARS TO BE THE MOST LIKELY FOCUS FOR INITIAL CONVECTIVE
   DEVELOPMENT THIS AFTERNOON...AS A PROGRESSIVE UPPER IMPULSE
   CURRENTLY POSITIONED OVER THE OK AND NRN TX PANHANDLES SHOULD
   CONTINUE EWD NEAR THE OK/KS BORDER.
  
   STRONG SFC HEATING IS UNDERWAY ACROSS MOST OF OK...WITH BOUNDARY
   LAYER CU FORMING MORE RECENTLY BUT STILL EXHIBITING CAPPED/FLAT
   CHARACTER. PERSISTENT CONVERGENCE ALONG THE DRYLINE...ALONG WITH
   FURTHER BOUNDARY LAYER HEATING WITH TEMPERATURES REACHING THE UPPER
   80S/LOWER 90S F WITHIN THE MOIST AIR...SHOULD RESULT IN EROSION OF
   THE SIGNIFICANT CAPPING INVERSION NOTED IN THE 18Z OUN SOUNDING. AS
   THIS OCCURS...DISCRETE TSTM DEVELOPMENT ALONG THE DRYLINE APPEARS
   LIKELY...WITH AN ACCOMPANYING THREAT FOR LARGE HAIL AND DMGG WINDS.
   TORNADO POTENTIAL SHOULD STEADILY INCREASE THROUGH THE LATE
   AFTERNOON/EVENING ACCOMPANYING SUSTAINED SUPERCELLS...AS WIND
   PROFILES CONTINUE TO STRENGTHEN.
  
   RECENT SUITE OF HIGH-RESOLUTION MODEL GUIDANCE INDICATES CONVECTION
   SHOULD INITIATE ACROSS THE NRN HALF OF THE HIGHLIGHTED AREA BETWEEN
   20-21Z...AND PERHAPS AFTER 21Z ACROSS SWRN/S-CNTRL OK. A TORNADO
   WATCH WILL LIKELY BE ISSUED WITHIN THE NEXT HOUR.
  
   ..ROGERS/KERR.. 05/19/2013
  
  
   ATTN...WFO...TSA...OUN...
 

 

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any idea where SPC got that storm vector from? most of the indications I am seeing says the storm vector will start at 180 and shift eventually to 220 or maybe 230. 260@30 kts just doesn't seem right, unless I am missing something here.

You're right. The mesoanalysis shows the storm motion should be at 225 degrees or maybe a bit more toward 190 or 200.

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70/30 watch up 

 

 

 
DISCUSSION...RAPID BOUNDARY LAYER DESTABILIZATION IS UNDERWAY ACROSS
CENTRAL AND EASTERN KANSAS...WHERE FORCING FOR UPWARD VERTICAL
MOTION IN THE EXIT REGION OF A 500 MB JET STREAK WILL AID STORM
INITIATION DURING THE NEXT FEW HOURS.  DISCRETE SUPERCELLS APPEAR
LIKELY... ESPECIALLY INITIALLY...BEFORE CONVECTION BEGINS TO
CONSOLIDATE... WITH THE UPSCALE GROWTH OF A SEVERE MESOSCALE
CONVECTIVE SYSTEM EXPECTED BY EARLY EVENING.  STORMS WILL SPREAD
INTO ADJACENT PORTIONS OF SOUTHEAST NEBRASKA...SOUTHWEST IOWA AND
WESTERN MISSOURI.  STRONGEST STORMS WILL BE CAPABLE OF PRODUCING
VERY LARGE HAIL...A FEW TORNADOES...SOME POSSIBLY STRONG...BEFORE
DAMAGING WINDS BECOME A MORE PROMINENT RISK THIS EVENING.
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I don't think it would be a PDS, as the highest probs are where the tor watch was just issued.

 

I disagree that the stronger parameters are in the northern target.  The cap breaking earlier has a chance to really make the northern stuff messy.  The instability and even the bulk shear and shear vector orientation are more impressive in OK, IMO... however, terrain can be more an issue if things go into Osage County.

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Central OK is still rather capped.

 

Yes, but it is still REALLY early... I want the area to stay capped until around 4 pm personally... things are more likely to stay discrete that way.  It also waits for convection to get going while the better parameters move into place.

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I doubt we get a PDS today ... upscale growth and borderline LCLs are working against it.  Then again, they tossed that one out for the OH Valley a while back so who knows.

 

I doubt the PDS watch also...mainly because of the uncertainty.  However, I do not see LCLs being a huge problem. The warm sector is moistening very impressively.  Storms may start out with higher LCLs but by evening it shouldn't be an issue, even into OK.  I guess they could be up around 1000-1200 meters, but in that range strong tornadoes can still form.

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Another 70/30 watch 

 

DISCUSSION...THE INITIATION OF DISCRETE SUPERCELLS APPEARS LIKELY
ALONG THE DRYLINE ACROSS CENTRAL OKLAHOMA DURING THE NEXT FEW
HOURS...BEFORE ADVECTING AWAY FROM THE DRYLINE ON 40-50 KT DEEP
LAYER SOUTHWESTERLY MEAN FLOW. AS ACTIVITY PROGRESSES THROUGH A
MOIST UNSTABLE BOUNDARY LAYER WITH SIZABLE CAPE...THE RISK FOR VERY
LARGE HAIL AND TORNADOES IS EXPECTED TO INCREASE THROUGH THE EVENING
HOURS. BY EARLY EVENING...A STRENGTHENING SOUTHERLY LOW-LEVEL JET
WILL CONTINUE TO ENLARGE LOW-LEVEL HODOGRAPHS...MAINTAINING THE RISK
FOR TORNADOES ACROSS EASTERN OKLAHOMA. A COUPLE OF LONG-LIVED/LONG
TRACK SUPERCELLS ARE POSSIBLE...WITH A RISK FOR A FEW STRONG
TORNADOES.

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