2005

Mesoscale Discussion #0343


CONCERNING...TORNADO WATCH 66...

   

VALID 221937Z - 222100Z

   

THREAT EXISTS FOR STRONG TORNADOES NEXT FEW HOURS OVER SRN GA AND EXTREME NRN FL.  THREAT WILL INCREASE OVER SRN PORTIONS OF WW AS WELL.

   

18Z TLH RAOB IS FAVORABLE FOR STRONG TORNADOES.  ALTHOUGH BOUNDARY LAYER IS SOMEWHAT COOL...STRONGER SURFACE BASED INSTABILITY EXISTS FARTHER E WHERE TEMPERATURES HAVE RISEN INTO THE UPPER 70S AND 80S.

   

HODOGRAPH IS QUITE FAVORABLE FOR TORNADOES WITH 0-1 SRH  IN EXCESS OF 200 M2/S2.  AREA VAD WIND PROFILES SHOW 200-300 0-1KM SRH VALUES IN VICINITY OF WARM FRONT AS WELL.

   

SURFACE ANALYSIS INDICATES STRONG PRESSURE FALLS OVER THE ERN FL PANHANDLE / NRN FL AND SRN GA. WITH LOW LEVEL JET STRENGTHENING AND SHIFTING EWD...ADDITIONAL TORNADIC SUPERCELLS MAY DEVELOP OVER NRN FL LATER THIS AFTERNOON.  VERY LARGE HAIL WILL BE LIKELY AS WELL.

Mesoscale Discussion #2112


CONCERNING...TORNADO WATCH 755...

   

VALID 291804Z - 291930Z

   

THREAT FOR TORNADOES APPEARS TO BE INCREASING OVER ERN PORTIONS OF WW 755...WITH HIGHEST THREAT OVER SERN AL...SWRN GA...AND PERHAPS THE ERN FL PANHANDLE.

   

LATEST SATELLITE IMAGERY AND RADAR ECHO TOPS INDICATE STORMS STRENGTHENING OVER ERN PORTIONS OF WW...WHERE INSTABILITY HAS INCREASED WITH TEMPERATURES INTO THE MID 80S. SHEAR PROFILES CONTINUE TO BE EXTREMELY FAVORABLE FOR EMBEDDED SUPERCELL TORNADOES...WITH SMALL BUT STRONG COUPLETS NOW SEEN ON LOCAL RADARS. TORNADO THREAT WILL SHIFT NWD WITH TIME.

Mesoscale Discussion #2381


CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

   

VALID 060813Z - 060945Z

   

SRN PORTION OF THE SQUALL LINE HAS EVOLVED INTO DISCRETE SUPERCELLS THIS MORNING.  THE 2-6KM MEAN WIND HAS LARGELY REMAINED NORMAL TO THE LINE THROUGH THE LAST SEVERAL HOURS...SUGGESTING A MIXED-MODE OF LINE SEGMENTS AND INDIVIDUAL CELLS.  VWP/S SUGGEST VERY STRONG LOW-LEVEL WIND FIELDS OWING TO A STRONG AGEOSTROPHIC RESPONSE TO PRESSURE FALLS ACROSS THE LWR GRTLKS REGION.  0-1KM SRH IN EXCESS OF 340 M2/S2 HAVE BEEN OBSERVED AT LOUISVILLE.  GIVEN NEARLY 70 KTS OF H85-H7 FLOW...MODEST BOUNDARY LAYER MOISTURE AND PRESENCE OF SUSTAINED DISCRETE SUPERCELLS...THERE WILL BE THE THREAT FOR AN ISOLD TORNADO OR TWO ACROSS SRN IND AND WRN KY.  OTHERWISE...A CONTINUED DAMAGING WIND THREAT WILL EXIST...ALONG WITH HAIL.

   

PORTIONS OF SEVERE THUNDERSTORM WATCH 844 MAY REQUIRE AN UPGRADE TO A TORNADO WATCH SHORTLY.


**This MCD was published as the Evansville, IN EF3 was ongoing

Mesoscale Discussion #2407


CONCERNING...TORNADO WATCH 858...

   

VALID 122240Z - 122345Z

   

CYCLIC SUPERCELLS WERE MOVING NEWD ACROSS CNTRL IA AT 40KT....AS WELL AS NWRN IA. ENVIRONMENT AHEAD OF THIS ACTIVITY REMAINS SUPPORTIVE FOR TORNADOES WITH LATEST DIAGNOSTIC DATA AND CELL MOTIONS RESULTING IN EFFECTIVE SRH AROUND 350 M2/S2.

   

FARTHER NW...AREA ACROSS SERN SD INTO SWRN MN CONTINUES TO FAVOR STRONG UPWARD MOTION IN STEEP LAPSE RATE ENVIRONMENT. EFFECTIVE SHEAR IS SLIGHTLY WEAKER BENEATH UPPER TROUGH AND INTENSE STORMS WITH HAIL WILL SPREAD INTO SWRN MN OVER THE NEXT HOUR.

Mesoscale Discussion #2427


CONCERNING...TORNADO WATCH 864...865...

   

VALID 151613Z - 151815Z

   

TORNADO THREAT CONTINUES TO INCREASE.  GREATEST RISK FOR TORNADOES...A COUPLE OF WHICH COULD BE SIGNIFICANT...WILL EXIST IN A REGION BOUNDED BY A LITTLE ROCK AR-VICHY MO-SALEM IL-EVANSVILLE IND-CROSSVILLE TN LINE THROUGH AT LEAST MID-AFTN.

   

STRONGEST PRESSURE FALLS EXIST FROM THE KSTL AREA NEWD INTO CNTRL IL. DEEPENING SFC LOW OVER SWRN MO WILL RAPIDLY DEVELOP NEWD TOWARD THESE FALLS THROUGH MID-AFTN.  THE WARM/MOIST BOUNDARY LAYER ALONG THE OH VLY WAS BEGINNING TO ADVECT N OF THE OH RVR... BUT WAS A LITTLE SLOW TO ERODE ACROSS THE OZARKS.  AS THE LOW REDEVELOPS NEWD...THE WARM AIR SHOULD ADVANCE INTO ECNTRL MO-CNTRL IL-CNTRL IND LINE BY MID-AFTN.

   

STRONGEST LLJ AXIS IS EXPECTED TO EXIST FROM THE MS DELTA NWD INTO WRN KY AND CNTRL IND BENEATH INCREASING SWLY FLOW OF 100+ KTS AT H5. RESULTANT DEEP/LOW-LEVEL SHEAR WILL BE MORE THAN SUFFICIENT FOR SUPERCELLS/TORNADOES.  THE STRONGEST LOW-LEVEL SHEAR WILL EXIST CLOSER TO THE TRACK OF THE SFC LOW/WARM FRONT...MAINLY FROM PARTS OF AR INTO ECNTRL MO...CNTRL/SRN IL...SRN IND...WRN KY AND WRN TN.

   

PRE-FRONTAL CONFLUENCE BANDS...ALREADY DEVELOPING ACROSS CNTRL AR AND SRN MO WILL GRADUALLY INTENSIFY WITH BOTH DISCRETE AND MIXED LINEAR-DISCRETE MODES LIKELY TO EXIST. THE SEVERE THREAT WILL GRADUALLY DIMINISH FROM W-E ACROSS SRN MO/AR/NERN TX AS THE COLD FRONT BEGINS TO ACCELERATE EWD.

Mesoscale Discussion #2429


CONCERNING...TORNADO WATCH 864...865...866...

   

VALID 151834Z - 152030Z

   

HIGH PROBABILITY FOR STRONG TORNADOES WILL EXIST THROUGH AT LEAST 22Z ACROSS EXTREME SERN MO...SRN IL...SWRN IND...WRN KY AND WRN TN.

   

SFC LOW HAS MOVED INTO ECNTRL MO AS OF 18Z...JUST W OF KSTL.  THE WARM FRONT HAS ADVANCED INTO SRN IL AND SRN IND AHEAD OF THE LOW WITH A WARM/HUMID BOUNDARY LAYER NOW IN PLACE OVER ALL OF SERN MO...SRN IL...SWRN IND SWD INTO THE LWR MS VLY.  THE LOW IS EXPECTED TO TRACK INTO CNTRL IL BY LATE AFTN...WITH THE WARM FRONT CONTINUING NWD INTO THE I-70 CORRIDOR.  A COLD FRONT WILL SWEEP EWD ACROSS SRN MO AND AR THROUGH THE AFTN.

   

TSTMS ALONG A PRE-FRONTAL TROUGH ACROSS ERN AR HAVE INTENSIFIED RAPIDLY ACROSS THE MS VLY AS THEY ENCOUNTER THE PRIMARY LOW-LEVEL THETA-E AXIS.  OTHER STORMS HAVE ALSO INTENSIFIED FROM NEAR KSTL SWWD INTO CNTRL AR ALONG THE SYNOPTIC COLD FRONT.  

   

STRONGEST LOW-LEVEL SHEAR PROFILES EXIST FROM THE MEMPHIS AREA NWD INTO SERN MO...SRN IL EWD INTO SWRN IND...FAR W KY.  PAH/MEM VWPS SHOW 0-1KM SHEAR IN EXCESS OF 30 KTS AND 0-3KM SRH OF 300-500 M2/S2...MORE THAN ENOUGH TO SUPPORT STRONG TORNADOES.  GIVEN THE EVOLUTION INTO DISCRETE CELLS NOTED ALONG THE PRE-FRONTAL TROUGH...IT APPEARS THE HIGHEST THREAT FOR STRONG TORNADOES WILL EXIST FROM ALONG THE MS RVR FROM MEMPHIS NWD INTO SRN IL...THEN EWD INTO SRN IND...FAR W KY AND WRN TN THROUGH 22Z.

   

FARTHER W AND S...THE COLD FRONT WILL BEGIN TO SURGE EWD.  THE LOW-LEVEL SHEAR PROFILES HAVE RELAXED SOMEWHAT OWING TO A WEAKENING/VEERING LOW-LEVEL WINDS.  BUT...THEY WILL REMAIN STRONG ENOUGH TO SUPPORT A MIXED MODE OF DISCRETE CELLS/SHORT LINES WITH DAMAGING WINDS/ISOLD TORNADO THREAT ACROSS CNTRL/SRN AR ALONG THE FRONT.

Mesoscale Discussion #2431


CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

   

VALID 151932Z - 152100Z

   

THERE WILL BE A HIGH POTENTIAL FOR STRONG TORNADOES ACROSS THE OH VLY REGION FROM SRN IL/NWRN TN EWD INTO CNTRL/SRN IND... WCNTRL/SWRN OH AND NWRN KY.  TORNADO WATCH WILL BE NEEDED DOWNSTREAM OF WWS 865/866 BY 21Z.

   

A 999 MB LOW WAS LOCATED JUST NE OF KSTL AT 19Z.  THE WARM FRONT HAS JUMPED TO THE I-70 CORRIDOR IN INDIANA AND IS MOVING INTO WCNTRL OH ATTM.  BOUNDARY LAYER HAS BECOME INCREASINGLY UNSTABLE ALONG/S OF THE FRONT WITH MUCAPE OF 1000-2000 J/KG NOSING NWD INTO THE OH/TN VLYS.  PRESSURE FALLS HAVE ALSO BEEN INCREASING WITHIN THE WARM SECTOR ACROSS THE OH VLY. 

   

PRE-FRONTAL BAND OF TSTMS INTENSIFIED FROM SRN IL INTO WRN TN AS IT MOVED INTO THE INSTABILITY AXIS WITH NUMEROUS DISCRETE SUPERCELLS NOTED. OVERLAY OF 18Z RAOB DATA AND RUC ANALYSIS SHOWS THAT THE STRONGEST CROSS-OVER BETWEEN SLY H85 WINDS AND THE WSWLY H5 WINDS EXISTS ACROSS SRN IND/NWRN KY/SWRN OH AT MID-AFTN.  LATEST VWP FROM PAH/EVANSVILLE/WILMINGTON OHIO SHOWS IMPRESSIVE LOW-LEVEL SHEAR PROFILES /0-1KM SHEAR 35+ KTS/ AS THE BOUNDARY LAYER FLOW BACKS WITHIN SERN QUADRANT OF THE SFC LOW/PRESSURE FALL AXIS.  DISCRETE SUPERCELLS AND MIXED MODES OF LINE SEGMENTS/ DISCRETE CELLS WILL REMAIN LIKELY DOWNSTREAM INTO SRN IND...NWRN KY...WRN TN AND SWRN/WCNTRL OH WITH A HIGH PROBABILITY OF STRONG TORNADOES AND DAMAGING WIND GUSTS.

Mesoscale Discussion #2435


CONCERNING...TORNADO WATCH 868...869...

   

VALID 152358Z - 160130Z

   

LONG TRACK SUPERCELLS PRODUCING OCCASIONAL TORNADOES CONTINUE TO TRACK ACROSS PORTIONS OF TORNADO WATCHES 868 AND 869 THIS EVENING.

   

SOME OF THE MORE INTENSE AND PERSISTENT CELLS OVER THE PAST HOUR HAVE BEEN MOVING TOWARD MIDDLE TN AND SCNTRL KY. THIS ACTIVITY WAS CROSSING A CORRIDOR WHERE INTENSE LOW LEVEL SHEAR AND ABUNDANT LOW LEVEL MOISTURE CONTINUES TO SUPPORT LONG-LIVED ROTATING STORMS AND TORNADOES...AS WELL AS DAMAGING WINDS. ONE OF THESE CELLS HAS JUST CROSSED BWG AREA AND ADDITIONAL INTENSE AND POTENTIALLY DANGEROUS STORMS ARE NOW MOVING RAPIDLY TOWARD THE NASHVILLE AREA FROM THE WEST AT 40-50KT.

Mesoscale Discussion #2441


CONCERNING...TORNADO WATCH 869...871...872...

   

VALID 160418Z - 160445Z

   

INTENSE PRE-FRONTAL SQUALL LINE WITH EMBEDDED LEWPS/BOWS WILL MOVE EAST AND INTO TORNADO WATCH 872 WITHIN THE HOUR. SEVERE WEATHER POTENTIAL WILL SUBSIDE ACROSS MIDDLE TN AS THE STRONG FRONTAL PASSAGE OCCURS OVER THE REGION AND TORNADO WATCH 869 WILL EXPIRE AS SCHEDULED AT THE TOP OF THE HOUR.

Mesoscale Discussion #2479


CONCERNING...TORNADO WATCH 876...

   

VALID 272307Z - 280100Z

   

THREAT FOR ISOLATED STRONG LONG TRACK TORNADOES IS EXPECTED TO PERSIST INTO MID EVENING. GREATEST THREAT APPEARS TO BE FROM W CNTRL THROUGH CNTRL AR NEXT COUPLE HOURS. LARGE HAIL MAY ALSO ACCOMPANY THE STRONGER STORMS.

   

EARLY THIS EVENING A LINE OF DISCRETE TORNADIC SUPERCELLS EXTENDS FROM POPE COUNTY SWWD THROUGH HOWARD COUNTY IN W CNTRL AR. THE LINE IS MOVING SLOWLY EWD WHILE INDIVIDUAL STORMS MOVE NE AT 30 TO 35 KT. OTHER SEVERE STORMS EXTEND SWWD INTO NERN TX. THE 50+ KT LOW LEVEL JET IS CO-LOCATED WITH THE AXIS OF MAXIMUM INSTABILITY ACROSS CNTRL AR. THIS REGION IS WITHIN A ZONE OF RELATIVELY STRONG PRESSURE FALLS AND BACKING LOW LEVEL WINDS ACCOMPANYING EXIT REGION OF UPPER JET THAT IS ROUNDING BASE OF UPPER TROUGH. MLCAPE OF 1000 TO 1500 J/KG AND LARGE LOW LEVEL HODOGRAPHS WITH 0-1 KM STORM RELATIVE HELICITY IN EXCESS OF 400 M2/S2 WILL SUPPORT POTENTIAL FOR STRONG TORNADOES AS SUPERCELLS MOVE THROUGH W CNTRL AND CNTRL AR NEXT FEW HOURS.

Mesoscale Discussion #2489


CONCERNING...TORNADO WATCH 882...

   

VALID 280840Z - 281015Z

   

PARAMETERS REMAIN FAVORABLE FOR TORNADOES ACROSS NERN LA INTO WRN AND CENTRAL PORTIONS OF MS.

   

REGIONAL RADARS AT 0830Z INDICATED A LINE OF STORMS WITH EMBEDDED SUPERCELLS...PER NUMEROUS SHEAR COUPLETS...EXTENDING FROM SUNFLOWER COUNTY MS SSWWD TO FAR NERN LA.  DESPITE MUCAPE VALUES AOB 500 J/KG...STRONG DEEP LAYER SHEAR VALUES WILL CONTINUE TO SUPPORT ORGANIZED STORMS THE NEXT SEVERAL HOURS AS THIS LINE OF STORMS CONTINUES TO MOVE EWD ACROSS MS.  0-3 KM SRH VALUES REMAIN VERY STRONG AT 300-550 M2/S2...SUGGESTING THE POTENTIAL FOR STRONG TORNADOES.

Mesoscale Discussion #2501


CONCERNING...TORNADO WATCH 884...

   

VALID 282239Z - 282345Z

   

TORNADO THREAT APPEARS TO BE INCREASING IN THE SHORT TERM ACROSS CNTRL/SCNTRL AL IN TORNADO WATCH 884...NAMELY IN A CORRIDOR FROM BIRMINGHAM TO NEAR MONTGOMERY.

   

STRONG MESOCYCLONES HAVE BEEN COMMON OVER THE PAST HOUR OR TWO ALONG/SOUTH OF THE BIRMINGHAM AREA. WITHIN WEDGE OF WARM/UNSTABLE AIR...ADDITIONAL TSTMS WEST OF THE SELMA AL AREA WILL CONTINUE TO INTENSIFY AND PROGRESS NEWD. THESE STORMS WILL INTERACT WITH/CROSS EFFECTIVE WARM FRONTAL WEDGE ARCING NW-SW FROM CNTRL AL INTO THE FL PANHANDLE OVER THE NEXT FEW HOURS. NEAR THIS BOUNDARY...LOW LEVEL FLOW IS BACKED TO SELY...WITH 0-1 SRH VALUES OF 300 M2/S2 OR GREATER BEING VERY FAVORABLE FOR STORM ROTATION/TORNADOES.