2007

Mesoscale Discussion #0108


CONCERNING...TORNADO WATCH 

   

wVALID 020935Z - 021030Z

   

CONTINUE WW.  AN ADDITIONAL WW MAY NOT BE NEEDED...BUT CURRENT WW MAY NEED TO BE EXTENDED LOCALLY FOR AN HOUR OR TWO...FROM NEAR TAMPA INTO AREAS NORTHWEST OF MELBOURNE.

   

LONG-LIVED TORNADIC SUPERCELL IS IN THE PROCESS OF ADVANCING OFFSHORE...SOUTH/EAST OF DAYTONA BEACH.  BUT...SIGNIFICANT CONVECTIVE DEVELOPMENT PERSISTS UPSTREAM INTO AREAS NORTH OF TAMPA...ALONG PRE-FRONTAL CONFLUENCE NEAR 50+ KT LOW-LEVEL JET AXIS. AND...LOW-LEVEL HODOGRAPHS REMAIN VERY LARGE BENEATH THIS AXIS...FAVORABLE FOR THE POSSIBILITY OF ADDITIONAL TORNADIC DEVELOPMENT ACROSS THE CENTRAL PENINSULA...INCLUDING THE ORLANDO AREA...THROUGH 10-11Z. BEYOND THAT TIME...LATEST RUC SOUNDINGS CONTINUE TO SUGGEST THAT LOW-LEVEL HODOGRAPHS WILL SHRINK AS WIND FIELDS BEGIN TO VEER TO A MORE WESTERLY COMPONENT.  THIS MAY BE ACCOMPANIED BY A DIMINISHING RISK FOR ISOLATED TORNADOES...POSSIBLY AT LEAST A TEMPORARY DIMINISHING TREND TO CONVECTIVE DEVELOPMENT IN GENERAL.


**This MCD was issued minutes before the devastating Deland, Florida EF3 touched down

Mesoscale Discussion #0194


MESOSCALE DISCUSSION 0194

NWS STORM PREDICTION CENTER NORMAN OK

1035 AM CST SAT FEB 24 2007

   

AREAS AFFECTED...NW LA...SRN AR

   

CONCERNING...TORNADO WATCH 

   

VALID 241635Z - 241830Z

   

TORNADO THREAT IS INCREASING ACROSS WW 30.  TRENDS ARE BEING CLOSELY MONITORED FOR ADDITIONAL WWS NORTH/EAST OF WW.

   

CORE OF INTENSIFYING CYCLONIC...WESTERLY 500 MB JET STREAK HAS SHIFTED EASTWARD INTO CENTRAL TEXAS...AND SOUTHERLY LOW-LEVEL JET ACROSS THE ARKLATEX CONTINUES TO INTENSIFY.  LATEST RUC GUIDANCE AND VWP DATA INDICATE 850 FLOW IS NOW AROUND 60-70 KTS... CONTRIBUTING TO EXTREMELY LARGE LOW-LEVEL VERTICAL SHEAR.  SURFACE TEMPERATURES ACROSS THE ARKLATEX...EVEN AS FAR NORTH/EAST AS THE EL DORADO AREA...ARE NOW AROUND 70F...WITH SURFACE DEW POINTS CLIMBING THROUGH THE LOWER/MID 60S.  WITH INCREASINGLY FAVORABLE BOUNDARY LAYER CONDITIONS...TORNADO THREAT IS INCREASING.  ISOLATED STRONG OR VIOLENT TORNADOES ARE EXPECTED TO BECOME INCREASINGLY LIKELY THROUGH THE 18-21Z TIME FRAME IN INTENSIFYING SUPERCELLS NEAR/ NORTH OF SHREVEPORT THROUGH EL DORADO AND PINE BLUFF AR.

   

   ..KERR.. 02/24/2007


Mesoscale Discussion #0197


MESOSCALE DISCUSSION 0197

NWS STORM PREDICTION CENTER NORMAN OK

0145 PM CST SAT FEB 24 2007

   

AREAS AFFECTED...N CNTRL/NE LA THRU SE AR...NW MS

   

CONCERNING...TORNADO WATCH 30...32...

   

VALID 241945Z - 242145Z

   

CONTINUE WWS.  TORNADO POTENTIAL REMAINS RELATIVELY HIGH ACROSS PARTS OF NORTHEAST LOUISIANA/SOUTHEAST ARKANSAS LATE THIS AFTERNOON.

   

INTENSE CYCLONIC MID/UPPER JET CONTINUES TO NOSE NORTHEASTWARD INTO/THROUGH THE LOWER RED RIVER VALLEY/OZARK PLATEAU REGION.  AS THIS OCCURS...60-70 KT 850 JET IS GRADUALLY SHIFTING EASTWARD INTO THE LOWER MISSISSIPPI VALLEY...AHEAD OF SECONDARY SURFACE LOW MIGRATING ACROSS NORTH CENTRAL INTO NORTHEAST ARKANSAS.  LOW-LEVEL COLD ADVECTION IS INCREASING ALONG TRAILING SURFACE TROUGH/DRY LINE INTO EASTERN TEXAS...AND BOUNDARY MAY SERVE TO FOCUS SOLIDIFYING LINE OF STORMS NEXT FEW HOURS.  STORMS ON SOUTHERN FLANK OF LINE... AND ISOLATED SUPERCELLS DEVELOPING JUST AHEAD OF FRONTAL BAND... WILL CONTINUE TO POSE HIGHEST RISK FOR TORNADIC ACTIVITY NEXT FEW HOURS.  GREATEST RISK THROUGH 22-23Z APPEARS TO BE NORTHWEST OF MONROE LA INTO AREAS NEAR/NORTH OF GREENVILLE LA...WHERE SURFACE DEW POINTS ARE RISING INTO/THROUGH THE LOWER/MID 60S...AND STORMS ARE LIKELY ROOTED CLOSEST TO THE SURFACE.  GIVEN EXTREME MAGNITUDE OF LOW-LEVEL SHEAR...RISK FOR ISOLATED STRONG OR VIOLENT TORNADOES APPEARS RELATIVELY HIGH.

   

   ..KERR.. 02/24/2007

Mesoscale Discussion #0199


MESOSCALE DISCUSSION 0199

NWS STORM PREDICTION CENTER NORMAN OK

0349 PM CST SAT FEB 24 2007

   

AREAS AFFECTED...NRN LA...SE AR...WRN MS

   

CONCERNING...TORNADO WATCH 30...32...

   

VALID 242149Z - 242315Z

   

CONTINUE REMAINING VALID PORTION OF WWS.  RISK FOR TORNADOES... POSSIBLY STRONG OR VIOLENT...APPEARS HIGHEST NEAR/NORTH OF MONROE LA THROUGH AREAS NEAR/WEST OF GREENVILLE MS INTO AREAS JUST SOUTH OF MEMPHIS TN NEXT FEW HOURS.

   

INTENSE LINE OF STORMS...WITH SUPERCELLS EMBEDDED WITHIN THE LINE AND AHEAD OF THE LINE...CONTINUES TO EVOLVE AHEAD OF DRY LINE.  110 KT 500 MB JET CORE IS NOW PROPAGATING ACROSS THE ARKLATEX REGION...WITH STRONGEST FORCING FOR UPWARD VERTICAL MOTION SHIFTING ACROSS THE OZARK PLATEAU TOWARD THE LOWER OHIO VALLEY.  JUXTAPOSITION OF SOUTHERN FRINGE OF THIS STRONGER FORCING...AND NOSE OF BETTER BOUNDARY LAYER MOISTURE RETURN...WILL CONTINUE SPREADING ACROSS THE LOWER MISSISSIPPI VALLEY BETWEEN MONROE LA AND MEMPHIS TN THROUGH 25/00Z.  HIGHEST RISK FOR TORNADOES WILL EXIST ACROSS THIS REGION...WITH EXTREME LOW-LEVEL SHEAR BENEATH 60-80 KT SOUTHERLY LOW-LEVEL JET SUPPORTING CONTINUING POTENTIAL FOR ISOLATED STRONG OR VIOLENT TORNADOES.

   

   ..KERR.. 02/24/2007

Mesoscale Discussion #0237


CONCERNING...TORNADO WATCH 43...44...

   

VALID 011633Z - 011830Z

   

THREAT FOR TORNADOES CONTINUES OVER REMAINING PARTS OF WW 43 AND 44 WITH GREATEST THREAT FOR A FEW LONG TRACK STRONG TORNADOES NEXT FEW HOURS ACROSS MUCH OF MS...SRN AL AND NWRN AL. TORNADO THREAT WILL GRADUALLY SPREAD NEWD INTO WRN AND MIDDLE TN.

   

LATE THIS MORNING A COLD FRONT EXTENDS FROM A SURFACE LOW IN EXTREME SRN IA SWD THROUGH WRN IL...ERN AR...NWRN LA AND SERN TX. RICH LOW LEVEL MOISTURE WITH DEWPOINTS IN THE MID TO UPPER 60S ARE ADVECTING NWD ALONG A STRONG SLY LOW LEVEL JET INTO PRE-FRONTAL WARM SECTOR WITH MID 60S DEWPOINTS AS FAR N AS N CNTRL MS. AXIS OF GREATEST INSTABILITY EXTENDS FROM ERN LA THROUGH MUCH OF MS...SWRN TN AND WRN AL WITH MLCAPE 500 TO 1000 J/KG. DESPITE WIDESPREAD CLOUDS...LOW LEVEL THETA-E ADVECTION ASSOCIATED WITH THE BROAD LOW LEVEL JET WILL CONTRIBUTE TO NWD DESTABILIZATION INTO THE TN VALLEY WITH TIME.

   

WEAK CAP AND A DIVERGENT UPPER FLOW ASSOCIATED WITH UPPER JET EXIT REGION WILL MAINTAIN A FAVORABLE ENVIRONMENT FOR STORMS TO DEVELOP IN PRE-FRONTAL WARM SECTOR THROUGH THE AFTERNOON. THE 15Z RAOB FROM JACKSON MS SHOWS MODERATE SURFACE BASED INSTABILITY...LOW LEVEL HODOGRAPHS AND VERTICAL SHEAR FAVORABLE FOR SUPERCELLS CONTAINING LOW LEVEL MESOCYCLONES. STORMS CURRENTLY SPREADING INTO SWRN MS WILL POSE A THEAT FOR STRONG TORNADOES AS THEY MOVE ENEWD THROUGH THE WRM SECTOR OF SRN AND CNTRL MS NEXT FEW HOURS. OTHER POTENTIALLY TORNADIC STORMS ARE CURRENTLY MOVING NEWD THROUGH NERN MS AND EXTREME NWRN AL...EVENTUALLY SPREADING INTO WRN AND MIDDLE TN.

Mesoscale Discussion #0238


CONCERNING...TORNADO WATCH 44...46...

   

VALID 011748Z - 011945Z

   

CORRECTED TO CHANGE REFERENCE TO SEVERE THUNDERSTORM WATCHES TO TORNADO WATCHES

   

THREAT FOR LONG TRACK STRONG TORNADOES APPEARS TO BE INCREASING AND WILL PERSIST THROUGH THE AFTERNOON FROM SERN MS THROUGH SRN AND CNTRL AL...THE FL PANHANDLE AND EVENTUALLY INTO CNTRL AND NRN GA.

   

NUMEROUS STORMS INCLUDING DISCRETE SUPERCELLS CONTINUE DEVELOPING WITHIN ZONE OF LOW LEVEL CONFLUENCE AND ISENTROPIC LIFT IN WEAKLY CAPPED ENVIRONMENT OVER THE CNTRL GULF COAST REGION. STRONGEST STORMS ARE CURRENTLY FROM SERN MS...SRN AND CNTRL AL INTO THE FL PANHANDLE AND ARE MOVING NE. THE STRONG SLY LOW LEVEL JET IS ADVECTING MID TO UPPER 60S DEWPOINTS NWD THROUGH THE WARM SECTOR...AND THIS WILL CONTRIBUTE TO NWD DESTABILIZATION THIS AFTERNOON DESPITE WIDESPREAD CLOUD COVER. AN AXIS OF MLCAPE FROM 500 TO 1000 J/KG EXISTS ACROSS PARTS MS INTO AL AND THE FL PANHANDLE. LARGE LOW LEVEL HODOGRAPHS WITH 0-1 KM STORM RELATIVE HELICITY IN EXCESS OF 300 M2/S2 PERSISTS OVER A LARGE AREA...AND THIS WILL MAINTAIN A FAVORABLE ENVIRONMENT FOR TORNADIC SUPERCELLS NEXT SEVERAL HOURS.

   

STORMS DEVELOPING OVER NRN GA CURRENTLY APPEAR ELEVATED. THE STRONG LOW LEVEL JET WILL RESULT IN NWD DESTABILIZATION WITH TIME AS FAR N AS NRN GA LATER THIS AFTERNOON...AND THIS WILL CONTRIBUTE TO AN INCREASING TORNADO THREAT AS STORMS BECOME SURFACE BASED.

Mesoscale Discussion #0241


CONCERNING...SEVERE THUNDERSTORM WATCH 46...

   

VALID 011940Z - 012045Z

   

HP SUPERCELL IN DALE COUNTY OF SERN AL WILL POSE A HIGH RISK OF A LONG TRACK STRONG TORNADO AND VERY LARGE HAIL AS IT CONTINUES ENE AT 37 KT. A TORNADO HAS ALREADY BEEN CONFIRMED EARLIER WITH THIS STORM IN COFFEE COUNTY. THIS STORM HAS DEVELOPED ALONG THE SRN END OF A LARGER CLUSTER OF STORMS WHERE THE LOW LEVEL MOIST UNSTABLE INFLOW IS RELATIVELY UNIMPEDED. THE SUPERCELL WILL MOVE THROUGH PARTS OF HENRY COUNTY IN SERN AL AND CROSS THE GA BORDER INTO EARLY AND CLAY COUNTIES AROUND 2030Z.

Mesoscale Discussion #0243


CONCERNING...TORNADO WATCH 44...46...

   

VALID 012041Z - 012215Z

   

THREAT FOR TORNADOES CONTINUES OVER THE REMAINING PARTS OF WW 44 AND 46 WITH GREATEST THREAT FOR STRONG TORNADOES NEXT FEW HOURS FROM ERN MS THROUGH NCNTRL...CNTRL AND SRN AL...THE FL PANHANDLE AND PARTS OF WRN GA.

   

A COLD FRONT EXTENDS FROM WRN TN SWD THROUGH EXTREME WRN MS INTO SERN LA AND IS MOVING EAST. LOW LEVEL MOISTURE CONTINUES TO ADVECT NWD THROUGH PRE-FRONTAL WARM SECTOR INTO MUCH OF THE SERN STATES. LOWER 60S DEWPOINTS HAVE SPREAD AS FAR N AS NRN AL WITH UPPER 60S FROM SERN MS THROUGH SRN AND CNTRL AL INTO THE FL PANHANDLE. AN AXIS OF MLCAPE NEAR 1000 J/KG EXTENDS FROM THE FL PANHANDLE NWD INTO CNTRL AND SRN AL AND ERN MS WITH MORE MARGINAL INSTABILITY FARTHER N IN WRN AND MIDDLE TN. VERY STRONG VERTICAL SHEAR WITH LARGE LOW LEVEL HODOGRAPHS PERSIST THROUGH MUCH OF THE WARM SECTOR. THE BEST COMBINATION OF LOW LEVEL SHEAR AND INSTABILITY CURRENTLY EXISTS FROM ERN MS...N CNTRL THROUGH SRN AL INTO THE FL PANHANDLE. STORMS DEVELOPING IN THIS ENVIRONMENT WILL POSE THE GREATEST THREAT FOR STRONG TORNADOES NEXT SEVERAL HOURS.

Mesoscale Discussion #0246


CONCERNING...TORNADO WATCH 44...46...

   

VALID 012322Z - 020045Z

   

POTENTIAL FOR SIGNIFICANT TORNADOES IS EXPECTED TO CONTINUE ACROSS THE REGION THIS EVENING...NAMELY ACROSS CNTRL/SRN PORTIONS OF AL/GA AND THE FL PNHDL.  CONTINUE WW/S.

   

23Z MESOANALYSIS INDICATED PACIFIC COLD FRONT /DELINEATING WRN EDGE OF SYNOPTIC SYSTEM WARM SECTOR/ FROM MSL SWWD TO PIB. EFFECTIVE...COMPOSITE OUTFLOW BOUNDARY HAS BECOME ESTABLISHED TODAY IN MORE OF AN W-E FASHION FROM INTERSECTION WITH PACIFIC FRONT NE OF MEI ESEWD THROUGH MGM TO NEAR CSG TO AYS.  AIR MASS ALONG AND S OF THIS BOUNDARY REMAINS SLIGHTLY TO MODERATELY UNSTABLE /MLCAPES OF 500-1000 J PER KG/ OWING TO DEWPOINTS IN THE MID/UPPER 60S AND TEMPERATURES IN THE LOW/MID 70S.  TO THE N OF THIS BAROCLINIC ZONE...PERSISTENT AND MORE WIDESPREAD CONVECTION HAS LIMITED HEATING AND RESULTANT DESTABILIZATION WITH TEMPERATURES COMMONLY IN THE 60S.  

   

BROAD ZONE OF LOW-LEVEL WAA IN ADVANCE OF PACIFIC FRONT AND ASSOCIATED UPPER TROUGH WILL LIKELY MAINTAIN CLUSTERS OF TSTMS WITHIN THIS ZONE OF STRONGER INSTABILITY TO THE S OF COMPOSITE OUTFLOW BOUNDARY.  REGIONAL VWPS INDICATE VERTICAL SHEAR QUITE FAVORABLE FOR SUPERCELLS CAPABLE OF TORNADOES WITH 0-1 KM SRH OF 300-400 M2/S2 AND EFFECTIVE BULK SHEARS OF 55-70 KT.

   


TO THE N OF OUTFLOW BOUNDARY ACROSS NRN PORTIONS OF AL/GA...SUPERCELL/TORNADO THREAT STILL EXISTS...HOWEVER THIS THREAT APPEARS TO BE LESS THAN THAT WITHIN MORE UNSTABLE WARM SECTOR TO THE S.

Mesoscale Discussion #0361


CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   

VALID 282029Z - 282200Z

   

TORNADO WATCH WILL BE NEEDED SHORTLY FOR MOST OF WRN KS AND SURROUNDING AREAS.

   

VISIBLE SATELLITE IMAGERY INDICATES CU INCREASING IN DEEPLY MIXED/DRY AIR ACROSS ERN CO...WITH ADDITIONAL CU FARTHER E INTO WRN KS. NW-SE ORIENTED CLOUD BILLOWS ALSO INDICATE CAPPING IN PLACE OVER MUCH OF NEB INTO KS. MODIFIED 18Z DDC SOUNDING SHOWS LITTLE CIN REMAINS ALONG AND W OF THAT LONGITUDE WITH STEEP MID/UPPER LAPSE RATES IN PLACE WITH VERY STRONG SHEAR PROFILES. CONTINUED PRESSURE FALLS W OF DRYLINE WILL KEEP LOW LEVEL FLOW BACKED WITH INCREASING SFC DEWPOINTS. SUPERCELLS ARE LIKELY TO FORM ALONG THE CO/KS BORDER REGION WITH VERY LARGE HAIL AND TORNADOES LIKELY. A FEW TORNADOES MAY BE STRONG.

Mesoscale Discussion #0481


CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   

VALID 131951Z - 132045Z

   

RAPID BOUNDARY LAYER RECOVERY IS UNDERWAY ACROSS NCNTRL TX THIS AFTERNOON AS WARM FRONT LIFTS THROUGH THE METROPLEX...NWWD INTO NWRN TX JUST SW OF SPS WHERE LONG-LIVED POTENTIALLY TORNADIC SUPERCELL IS TRACKING SOUTH OF SEY.  STRONG HEATING IS ALSO OCCURRING WEST OF I-35 AND THIS WILL UNDOUBTEDLY ASSIST NEW UPDRAFT DEVELOPMENT OVER THE NEXT FEW HOURS AS CAP ERODES.  STRONG LOW LEVEL SHEAR IS NOTED ACROSS MOST OF THE WARM SECTOR...ESPECIALLY FOCUSED ALONG NW-SE ORIENTED WARM FRONT. LATEST THINKING IS ADDITIONAL THUNDERSTORMS WILL EVOLVE OVER THE NEXT FEW HOURS WITHIN STRONGEST ZONE OF HEATING...TO THE NW-SW OF THE METROPLEX...THEN SPREAD NEWD INTO ZONE OF FAVORABLE LOW LEVEL SHEAR WHERE TORNADO DEVELOPMENT APPEARS LIKELY.

   

PDS TORNADO WATCH WILL BE ISSUED BY 21Z FOR MUCH OF NCNTRL/CNTRL TX. ADDITIONALLY...THIS REGION WILL BE UPGRADED TO A HIGH RISK.

Mesoscale Discussion #0495


CONCERNING...TORNADO WATCH 142...143...

   

VALID 150009Z - 150215Z

   

THROUGH 01-02Z...THE GREATEST SUPERCELL/TORNADO THREAT WILL EXIST FROM FAR SERN AL INTO SWRN AND PERHAPS CNTRL GA.  ELSEWHERE...THE SEVERE WEATHER THREAT FOR TORNADO WATCH 142...143...CONTINUES.

   

COMPLEX MCS IS ONGOING AS OF 2355Z FROM NERN GA SWWD INTO SRN AL AND THE WRN FL PNHDL WITH THE MOST INTENSE STORMS /HP SUPERCELLS/ OVER RUSSELL/BARBOUR AND COFFEE/DALE COUNTIES IN SERN AL.  LATEST MESOANALYSIS INDICATES THAT RELATIVELY STRONG PRESSURE FALLS ARE OCCURRING AHEAD OF THESE MORE INTENSE STORMS OVER SERN AL WITH LATEST FT. RUCKER SHOWING A RESULTANT INCREASE IN LOW-LEVEL SHEAR OVER THE LAST HOUR.  INDEED...KINEMATIC ENVIRONMENT HAS BECOME QUITE FAVORABLE FOR TORNADIC SUPERCELLS GIVEN THE MOIST/UNSTABLE BOUNDARY LAYER WITH 0-1 KM SRH OF 300-350 M2/S2 AND EFFECTIVE BULK SHEARS OF 55-60 KT.

   

DESPITE THE RELATIVELY COMPLEX NATURE OF ONGOING STORMS...POTENTIAL WILL EXIST FOR EMBEDDED LONG LIVED SUPERCELLS CAPABLE OF TORNADOES...SOME OF WHICH COULD BE STRONG.  THIS MORE FAVORABLE ENVIRONMENT APPEARS TO BE BOUND BY WARM FRONT /CURRENTLY EXTENDING FROM INTERSECTION WITH MCS NEAR OR S OF CSG ESEWD TO OFF THE SERN GA COAST/ SWD INTO WARM SECTOR OVER SWRN GA WHERE AIR MASS REMAINS FAVORABLY MOIST AND SURFACE WINDS HAVE MAINTAINED AN ELY COMPONENT.

Mesoscale Discussion #0531


MESOSCALE DISCUSSION 0531

NWS STORM PREDICTION CENTER NORMAN OK

0741 PM CDT SAT APR 21 2007

   

AREAS AFFECTED...TX/OK PANHANDLES...TX SOUTH PLAINS

   

CONCERNING...TORNADO WATCH 157...

   

VALID 220041Z - 220245Z

   

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 157 CONTINUES.

   

CLUSTER OF SUPERCELLS /SOME TORNADIC/ WILL CONTINUE TO MOVE NEWD AROUND 30 KTS ACROSS THE CENTRAL OK/TX PANHANDLE AND NRN SOUTH PLAINS AREA IN THE NEXT FEW HOURS. THE COMBINATION OF STRONG LOW LEVEL VERTICAL MOTION EVIDENT BY THE 00Z AMA SOUNDING AND A STRONG PRESSURE FALL MAX CENTERED OVER THE TX PANHANDLE...INCREASING LOW LEVEL JET AND SUPERCELLULAR CONVECTION APPROACHING AN OLD DIFFERENTIAL HEATING BOUNDARY EXTENDING FROM DUMAS TO NEAR AMA TO SWISHER/BRISCOE COUNTIES SUGGESTS THAT THE POTENTIAL FOR SIG TORNADOES MAY INCREASE OVER THE NEXT 1-2 HRS. STRENGTHENING PRESSURE RISES OVER SERN NM WILL SUPPORT A SURGING DRYLINE/PACIFIC COLD FRONT INTO THE WRN PANHANDLES/WRN SOUTH PLAINS OVER THE NEXT FEW HRS. IT IS ANTICIPATED THAT DEVELOPING SVR CONVECTION ALONG THIS SURGING DRYLINE WILL OVERTAKE THE MORE DISCRETE SUPERCELLS IN THE 03-05Z TIME FRAME ACROSS THE ERN TX/OK PANHANDLES AND LOW ROLLING PLAINS WITH THE PRIMARY SVR THREAT OVER THE REMAINDER OF WW 157 LIKELY TRANSITIONING TO DMGG WINDS.

   

   ..CROSBIE.. 04/22/2007

Mesoscale Discussion #



Mesoscale Discussion #0698


CONCERNING...SEVERE POTENTIAL...WATCH NEEDED SOON 

   

VALID 051352Z - 051445Z

   

ENVIRONMENTAL CONDITIONS HAVE BECOME FAVORABLE FOR SEVERE STORMS AND A WATCH ISSUANCE WILL BE COORDINATED BETWEEN THE SPC AND THE AFFECTED LOCAL NATIONAL WEATHER SERVICE OFFICES SHORTLY.

   

SEVERE THREAT IS EXPECTED INCREASE RAPIDLY THIS MORNING...WITH POTENTIAL FOR SUPERCELLS CAPABLE OF PRODUCING STRONG TORNADOES LIKELY BY MIDDAY.

   

12Z SOUNDING FROM DODGE CITY INDICATES POTENTIALLY STRONG INSTABILITY IN THE WARM SECTOR OF CENTRAL HIGH PLAINS SURFACE CYCLONE.  MIXED LAYER CAPE IS ALREADY ON THE ORDER OF 3000 J/KG... AND THIS WILL INCREASE FURTHER WITH DAYTIME HEATING.  A MID-LEVEL CAP IS PRESENT...BUT GENERALLY WEAK AND IT MAY NOT TAKE LONG FOR THE INITIATION OF CONVECTIVE DEVELOPMENT WITH MID/UPPER FORCING ASSOCIATED WITH ANOTHER IMPULSE ALREADY BEGINNING TO LIFT NORTHEAST OF THE COLORADO/NEW MEXICO ROCKIES.  DRY LINE NEAR/WEST OF GARDEN CITY INTO THE GOODLAND AREA MAY PROVIDE ONE FOCUS...WITH REMNANT OUTFLOW BOUNDARY ANOTHER...SOUTHWEST OF CONCORDIA INTO DRY LINE INTERSECTION NEAR MCCOOK NEB.  GIVEN LARGE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS NEAR 40 KT SOUTHERLY LOW-LEVEL JET AXIS ACROSS CENTRAL OKLAHOMA INTO SOUTH CENTRAL NEBRASKA...BENEATH 50-70 KT CYCLONIC 500 MB FLOW...CONDITIONS ARE BECOMING VERY FAVORABLE FOR TORNADIC SUPERCELLS.  RISK FOR STRONG TORNADOES WILL INCREASE AS BOUNDARY LAYER CONTINUES TO WARM THROUGH MID DAY.

Mesoscale Discussion #0701


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 232 CONTINUES.

   

TORNADO POTENTIAL IS RAPIDLY INCREASING ACROSS PARTS OF NORTHWEST KANSAS INTO SOUTHWEST/SOUTH CENTRAL NEBRASKA.

   

INITIATION OF BOUNDARY LAYER BASED CONVECTION NOW APPEARS TO BE UNDERWAY TO THE NORTHWEST OF HILL CITY KS.  AND...FAIRLY RAPID INTENSIFICATION SHOULD ENSUE GIVEN FAVORABLE LARGE SCALE FORCING IN ENVIRONMENT WITH STEEP LAPSE RATES AND MIXED LAYER CAPE UP TO 3000 J/KG.  A CYCLONIC VORTICITY CENTER IS BECOMING BETTER DEFINED AS IT MIGRATES NORTHEASTWARD ACROSS EASTERN COLORADO...ASSOCIATED WITH AN IMPULSE LIFTING OUT OF AMPLIFIED WESTERN U.S. TROUGH.  AND A SURFACE LOW PRESSURE CENTER HAS DEVELOPED NEAR MCCOOK...IN THE VICINITY OF REMNANT OUTFLOW BOUNDARY/DRY LINE INTERSECTION.  CONVERGENT FLOW FIELD WITH SOUTHEASTERLY COMPONENT TO SURFACE FLOW EAST OF THIS FEATURE WILL CONTRIBUTE TO TORNADIC POTENTIAL...WHICH SEEMS LIKELY TO INCREASE BY 18-19Z IN AREA FROM HILL CITY TO MCCOOK...EAST NORTHEASTWARD TOWARD HASTINGS NEB.  THIS IS WHERE SURFACE TO 1 KM LOW-LEVEL HODOGRAPHS ARE MAXIMIZED...AND SUPPORTIVE OF STRONG TORNADOES.  VERY LARGE HAIL IS ALSO LIKELY IN DEVELOPING STORMS.

Mesoscale Discussion #0704


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 233 CONTINUES.

   

TORNADO POTENTIAL APPEARS LIKELY TO INCREASE OVER THE NEXT 1-2 HOURS ACROSS FAR NORTHEAST NEB INTO SOUTHEAST SD...INCLUDING THE YANKTON SD VICINITY.

   

LATEST SURFACE MESOANALYSIS DEPICTS WEST-EAST BOUNDARY SLOWLY LIFTING NORTHWARD ACROSS CENTRAL/EASTERN NEB...MOST AGGRESSIVELY ACROSS EASTERN NEB WHERE THE BOUNDARY IS UNIMPEDED BY EXISTING CONVECTION. OVER THE PAST HOUR...TEMPERATURES HAVE WARMED TO NEAR 70 F IN AREAS NEAR THE MISSOURI RIVER AS FAR NORTH AS SIOUX CITY IA. AS THE BOUNDARY LAYER CONTINUES TO DESTABILIZE...CELLS DEVELOPING NEAR THE MODIFYING/NORTHWARD LIFTING FRONT WILL HAVE TO BE CLOSELY MONITORED FOR AN INCREASING TORNADO POTENTIAL OVER THE NEXT FEW HOURS. PER WSR-88D VWP DATA FROM SIOUX FALLS/OMAHA...KINEMATICS STRONGLY SUPPORT ROTATING STORMS AND THE POTENTIAL FOR LOW LEVEL MESOCYCLONES GIVEN THE ENLARGED LOW LEVEL HODOGRAPHS/HIGH SRH ENVIRONMENT...WITH 0-1 KM SRH IN EXCESS OF 250 MS/S2.

Mesoscale Discussion #0708


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 234 CONTINUES.

   

LEADING EDGE OF 700 MB COOLING...ASSOCIATED WITH IMPULSE PIVOTING ACROSS THE NORTH CENTRAL HIGH PLAINS...HAS SLOWED EASTWARD PROGRESS ACROSS THE SOUTH CENTRAL HIGH PLAINS.  AND...FLOW FIELDS APPEAR LIKELY TO BEGIN TO GRADUALLY BACK LATE THIS AFTERNOON...AHEAD OF IMPULSE STILL DIGGING INTO THE SOUTHERN PLATEAU.  ANOTHER IMPULSE MAY BE IN THE PROCESS OF LIFTING NORTH NORTHEAST OF THE FOUR CORNERS REGION...AND COULD AID RENEWED CONVECTIVE DEVELOPMENT ALONG DRY LINE ACROSS PARTS OF WESTERN KANSAS...SOUTHWARD THROUGH PARTS OF NORTHWEST TEXAS BY 06/00Z.  DRY LINE MAY ALREADY BE RETREATING WEST OF DODGE CITY/HILL CITY KS...AND SOME RETREAT WESTWARD ACROSS THE WESTERN OKLAHOMA/TEXAS BORDER AREA COULD OCCUR PRIOR TO EARLY EVENING.  GIVEN..WEAKLY CAPPED MOIST BOUNDARY LAYER WITH CAPE TO 3000 J/KG...RISK FOR AT LEAST ISOLATED TO WIDELY SCATTERED TORNADIC SUPERCELL DEVELOPMENT WILL PERSIST LATE THIS AFTERNOON IN STRONGLY SHEARED FLOW REGIME.

Mesoscale Discussion #0709


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 233 CONTINUES.

   

SEVERE THREAT IS QUICKLY INCREASING/EXPANDING NORTHWARD ACROSS MUCH OF NORTHEAST NEB INTO SOUTHEAST SD...FROM THE AINSWORTH/NORFOLK NEB AREAS INTO THE WINNER/YANKTON SD VICINITIES...AND OTHER LOCALES NEAR/WEST OF SIOUX FALLS. IN ADDITION TO LARGE HAIL AND ISOLATED DAMAGING WIND GUSTS...ENVIRONMENTAL CONDITIONS SUPPORT THE POSSIBILITY OF A FEW STRONG TORNADOES THROUGH EARLY EVENING...ESPECIALLY IN AREAS ALONG/SOUTH OF I-90. A REPLACEMENT TORNADO WATCH IS LIKELY SOON...WITH A NORTHWARD EXPANSION ACROSS SD.

   

VOLUMETRIC RADAR TRENDS AND VISIBLE SATELLITE CHARACTERISTICS SUGGEST STORMS CONTINUE TO BECOME INCREASINGLY SURFACE BASED/BETTER ROOTED OVER THE PAST HOUR ACROSS NORTHEAST NEB. THIS INCLUDES A MATURE/TORNADIC SUPERCELLS MOVING NORTHWARD ACROSS CENTRAL KNOX COUNTY AND BROWN/KEYA PAHA COUNTIES AS OF 21Z. IN ADDITION TO AN INFLUX OF HIGHER BOUNDARY LAYER THETA-E AND AN INCREASINGLY UNSTABLE AIRMASS...WSR-88D VWP DATA FROM SIOUX FALLS SAMPLES THE VERY IMPRESSIVE LOW LEVEL WIND FIELDS...WITH AN ENLARGED/STRONGLY CURVED HODOGRAPH IN THE LOWEST 1-2 KM. ESTIMATES OF 0-1 KM SRH IN EXCESS OF 400 MS/S2 FAVOR THE POSSIBILITY OF LOW LEVEL MESOCYCLONES/TORNADOES...A FEW OF WHICH MAY BE STRONG THROUGH EARLY EVENING.

Mesoscale Discussion #0711


MESOSCALE DISCUSSION 0711

NWS STORM PREDICTION CENTER NORMAN OK

0616 PM CDT SAT MAY 05 2007

   

AREAS AFFECTED...SOUTHERN NEB...KS...NWRN OK

   

CONCERNING...TORNADO WATCH 232...234...235...

   

VALID 052316Z - 060015Z

   

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 232...234...235...CONTINUES.

   

SUPERCELLS CONTINUE TO GENERATE ACROSS NWRN OK/SCNTRL KS ALONG DRYLINE.  VERY STEEP LOW LEVEL LAPSE RATES ACROSS THE TX PANHANDLE/WRN KS HAVE ALLOWED THIS BOUNDARY TO ORIENT IN A SW-NE FASHION WHICH APPEARS TO BE CONDUCIVE FOR LONG-LIVED PARCEL RESIDENCE TIME IN MOST FAVORED ZONE OF CONVERGENCE.  POTENTIAL FOR TORNADOES REMAINS HIGH WITHIN HIGH INSTABILITY AIRMASS DOWNSTREAM INTO PORTIONS OF CNTRL KS AND SOUTH CENTRAL NEB.  THERE IS SOME REASON TO BELIEVE THAT ADDITIONAL DEVELOPMENT MAY SOON OCCUR ACROSS THE ERN TX PANHANDLE AS MUCH HIGHER BOUNDARY LAYER MOISTURE IS NOW SURGING NWWD THROUGH CDS WITH 68F TD AT 23Z.

   

   ..DARROW.. 05/05/2007

Mesoscale Discussion #0712


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 236 CONTINUES.

   

PARTICULARLY DANGEROUS TORNADO WATCH 236 CONTINUES ACROSS NORTH CENTRAL/NORTHEAST NEB AND CENTRAL/EASTERN SD INTO FAR SOUTHWEST MN/NORTHWEST IA THROUGH 04Z. THREAT FOR LARGE HAIL AND TORNADOES CONTINUES...INCLUDING THE POSSIBILITY FOR A STRONG TORNADO OR TWO THROUGH MID EVENING...ESPECIALLY ACROSS SOUTHEAST/EAST CENTRAL SD.

   

SURFACE MESOANALYSIS FEATURES SURFACE LOW ALONG THE SOUTH CENTRAL SD/NORTH CENTRAL NEB BORDER...WITH A WARM FRONT GRADUALLY LIFTING NORTHWARD ACROSS FAR SOUTHEAST SD INTO WEST CENTRAL IA...WITH RELATIVELY STRONG PRESSURE FALLS MAXIMIZED ALONG/NORTH OF THE FRONT. A NUMBER OF TORNADOES HAVE ALREADY BEEN REPORTED OVER THE PAST SEVERAL HOURS FROM FAR NORTHEAST NEB INTO SOUTHEAST SD...AND CONDITIONS WILL REMAIN RIPE FOR TORNADOES/LARGE HAIL OVER THE NEXT SEVERAL HOURS...INCLUDING THE POSSIBILITY FOR A STRONG TORNADO OR TWO. PRIMARY CONCERN WILL REMAIN IN A GRADUALLY NORTHWARD-SHIFTING CORRIDOR ACROSS SOUTHEAST SD INTO EAST CENTRAL SD...IN LOCALES ALONG AND JUST NORTH OF THE WARM FRONT. VWP DATA FROM THE SIOUX FALLS WSR-88D CONTINUES TO SAMPLE THE STRONGLY VEERED LOW LEVEL WIND PROFILES THAT EXIST ACROSS MUCH OF TORNADO WATCH 236...WITH 0-1 KM SRH IN EXCESS 500 M2/S2 REMAINING EXTREMELY FAVORABLE FOR LOW LEVEL MESOCYCLONES/TORNADOES.

Mesoscale Discussion #0867


MESOSCALE DISCUSSION 0867

NWS STORM PREDICTION CENTER NORMAN OK

0220 PM CDT WED MAY 23 2007

   

AREAS AFFECTED...TX/OK PNHDLS...EXTREME WRN OK...SWRN KS...NERN NM AND EXTREME SERN CO

   

CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   

VALID 231920Z - 232015Z

   

A DEEPENING CUMULUS FIELD WAS ACCOMPANYING A WWD SURGE OF LOW-LEVEL MOISTURE ACROSS THE SWRN KS...THE TX/OK PNHDLS AND WRN OK.  18Z AMA/DDC SOUNDINGS WERE STILL CAPPED...BUT STRONG HEATING...UPSLOPE MOISTURE ADVECTION AND INCREASING CONVERGENCE ALONG THE CAPROCK/RESIDUAL BOUNDARIES WERE BECOMING INCREASINGLY FAVORABLE FOR CONVECTIVE INITIATION.  LARGER SCALE HEIGHT FALLS WERE STILL UPSTREAM OVER NRN NM/SCNTRL CO...BUT WILL SPREAD EWD ATOP THE RETURNING MOISTURE LATER THIS AFTN.  UNTIL THEN...THE AFOREMENTIONED POSITIVES MAY ALONE BE SUFFICIENT FOR AT LEAST ISOLD STORM INITIATION ACROSS THE CNTRL/ERN TX PNHDL AND EXTREME WRN OK...WITH MORE WIDESPREAD DEVELOPMENT EXPECTED LATE AFTN/EARLY EVE OVER ALL OF THE PNHDLS...SERN CO...NERN NM AND SWRN KS. 

   

GENTLY BACKING LOW-LEVEL FLOW WILL BEGIN TO BOOST VERTICAL SHEAR VALUES THROUGH THE AFTN.  VERY STRONG INSTABILITY AND THE INCREASING SHEAR WILL BE HIGHLY CONDUCIVE FOR SUPERCELLS WITH VERY LARGE HAIL AND POSSIBLE TORNADOES OVER THE ENTIRE DISCUSSION AREA.  THREATS FOR ISOLD STRONG TORNADOES WILL BE HIGHEST ACROSS SWRN KS SWD INTO PARTS OF THE CNTRL/ERN TX/OK PNHDLS WHERE MID-60S SFC DEW POINTS WILL SURGE NWD ALONG/E OF THE CAPROCK AND NE-SW ORIENTED BOUNDARY INTO SWRN KS 22-03Z.

   

   ..RACY.. 05/23/2007

Mesoscale Discussion #0872


MESOSCALE DISCUSSION 0872

NWS STORM PREDICTION CENTER NORMAN OK

0606 PM CDT WED MAY 23 2007

   

AREAS AFFECTED...TX/OK PANHANDLE INTO NWRN OK AND SWRN KS

   

CONCERNING...TORNADO WATCH 293...

   

VALID 232306Z - 240030Z

   

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 293 CONTINUES.

   

PARAMETERS BECOMING EVEN MORE FAVORABLE FOR TORNADIC SUPERCELLS ACROSS WW 293.  EFFECTIVE BULK SHEAR VECTORS HAVE INCREASED AND ARE ORIENTED MORE NORMAL TO THE SURFACE BOUNDARY RETREATING NWWD ACROSS TX/OK PANHANDLES AS LOW LEVEL WINDS CONTINUE TO BACK WITH APPROACH OF STRONG SRN ROCKIES SHORT WAVE TROUGH.  THEREFORE...INCREASING DEEP LAYER AND LOW LEVEL SHEAR WILL SUPPORT TORNADOES AND VERY LARGE HAIL AS THE AIR MASS REMAINS MODERATELY UNSTABLE INTO THE EVENING.  LOW LEVEL MOISTURE/STRONGER INSTABILITY WILL CONTINUE TO RETREAT NWWD ACROSS THE TX/OK PANHANDLES AND SW KS IN RESPONSE TO PERSISTENT SURFACE PRESSURE FALLS FROM ERN NM TO SWRN KS.  THUS... NEW TSTMS SHOULD TEND TO DEVELOP ALONG AND W/NW OF CURRENT ACTIVITY AS ASCENT WITH SRN ROCKIES TROUGH SPREADS EWD ATOP RETURNING MOISTURE.  NEW UPDRAFTS WILL ALSO BE POSSIBLE ACROSS THE SW TX PANHANDLE REGION WHERE THE RETURNING MOISTURE BOUNDARY INTERSECTS THE DRY LINE OVER FAR W TX.

   

   ..PETERS.. 05/23/2007

Mesoscale Discussion #2108


MESOSCALE DISCUSSION 2108

NWS STORM PREDICTION CENTER NORMAN OK

1026 AM CDT THU OCT 18 2007

   

AREAS AFFECTED...PARTS OF NRN MS/NW AL THRU WRN AND MIDDLE TN...WRN/CNTRL KY INTO SRN IND

   

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   

VALID 181526Z - 181730Z

   

TRENDS ARE BEING CLOSELY MONITORED FOR AN INCREASING SEVERE THREAT AND THE POSSIBILITY OF ONE OR MORE WATCHES...PERHAPS BY EARLY AFTERNOON.

   

IN THE WAKE OF AN INITIAL SHORT WAVE IMPULSE NOW PIVOTING NORTHWARD INTO THE GREAT LAKES REGION...MID-LEVEL INHIBITION HAS BEEN WEAKENED ABOVE A MOISTENING PRE-FRONTAL CONFLUENT SOUTHERLY FLOW REGIME TO THE EAST OF THE MISSISSIPPI VALLEY CYCLONE.  MID-LEVELS ALREADY APPEAR TO BE WARMING FROM THE LOWER MISSISSIPPI VALLEY INTO THE WESTERN SLOPES OF THE CENTRAL/SOUTHERN APPALACHIANS.  HOWEVER... LATEST RUC GUIDANCE SUGGESTS INHIBITION MAY REMAIN FAIRLY NEGLIGIBLE ALONG AN AXIS FROM NORTHERN MISSISSIPPI THROUGH PARTS OF NORTH CENTRAL KENTUCKY.  AND...A ZONE OF MID-LEVEL MOISTENING/ LARGE-SCALE ASCENT IS EVIDENT IN WATER VAPOR IMAGERY RAPIDLY APPROACHING THIS REGION.  ADDITIONALLY... BREAKS IN CLOUD COVER LIKELY WILL BE SUFFICIENT TO ALLOW HEATING OF A BOUNDARY LAYER CHARACTERIZED BY UPPER 60S/LOWER 70S SURFACE DEW POINTS.

   

THUS...IT SEEMS PROBABLE THAT THE RISK FOR AT LEAST SCATTERED BOUNDARY BASED THUNDERSTORM DEVELOPMENT WILL INCREASE THROUGH THE 18-21Z TIME FRAME.  AS THIS OCCURS...SEVERE THREAT WILL INCREASE CORRESPONDINGLY WITHIN STRONG DEEP LAYER SHEAR FAVORABLE FOR SUPERCELLS...BETWEEN STRONG SOUTHWESTERLY POLAR AND SUBTROPICAL JET AXES.  ALTHOUGH LOW-LEVEL SHEAR MAY ONLY BE CHARACTERIZED BY WEAK CLOCKWISE TURNING WITH HEIGHT...HODOGRAPHS BENEATH 30-40 KT SOUTHWESTERLY 850 MB FLOW WILL BE FAVORABLE FOR TORNADOES...WHICH COULD BECOME STRONG.

   

   ..KERR.. 10/18/2007

Mesoscale Discussion #2111


MESOSCALE DISCUSSION 2111

NWS STORM PREDICTION CENTER NORMAN OK

0144 PM CDT THU OCT 18 2007

   

AREAS AFFECTED...PARTS OF SRN/ERN IL INTO INDIANA

   

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

   

VALID 181844Z - 182045Z

   

TRENDS ARE BEING MONITORED FOR AN INCREASING SEVERE THREAT.  AN ADDITIONAL TORNADO WATCH IS LIKELY LATE THIS AFTERNOON.

   

AS NEXT SIGNIFICANT IMPULSE TURNS THROUGH THE BASE OF UPPER TROUGH TO THE SOUTH OF UPPER MISSISSIPPI VALLEY CYCLONE...ASSOCIATED FORCING FOR UPWARD VERTICAL MOTION APPEARS TO BE AIDING INITIATION OF CONVECTIVE DEVELOPMENT ACROSS WESTERN KENTUCKY/TENNESSEE.  THIS FORCING IS EXPECTED TO GRADUALLY DEVELOP NORTH/NORTHEAST OF THE LOWER OHIO VALLEY LATE THIS AFTERNOON.  AND...STRENGTHENING UPWARD VERTICAL MOTION IS EXPECTED TO SUPPORT INCREASING CONVECTIVE DEVELOPMENT IN PRE-FRONTAL INSTABILITY AXIS ACROSS ILLINOIS/ INDIANA.  

   

MIXED LAYER CAPE IN EXCESS OF 1000 J/KG...AND STRONG DEEP LAYER SHEAR BENEATH 90+ KT SOUTHWESTERLY 500 MB POLAR JET...WILL BE SUPPORTIVE OF SUPERCELLS...WITH POTENTIAL FOR LOCALIZED VERY LARGE HAIL/DAMAGING WINDS. ADDITIONALLY...LARGE LOW-LEVEL HODOGRAPHS BENEATH 40 TO 50 KT 850 FLOW...LIKELY TO BACK FROM SOUTHWESTERLY TO SOUTHERLY LATE THIS AFTERNOON...WILL BE FAVORABLE FOR TORNADOES.  THIS INCLUDES THE RISK FOR STRONG TORNADOES.

   

STORM DEVELOPMENT SEEMS MOST PROBABLE FROM PARTS OF SOUTHERN ILLINOIS THROUGH THE INDIANAPOLIS IND AREA DURING THE 18/21Z- 19/00Z TIME FRAME.  BUT...ACTIVITY MAY DEVELOP NORTHWARD...EITHER SIDE OF THE ILLINOIS/INDIANA BORDER AREA...INTO THE GREATER CHICAGO METROPOLITAN AREA.

   

 ..KERR.. 10/18/2007

Mesoscale Discussion #2117


MESOSCALE DISCUSSION 2117

NWS STORM PREDICTION CENTER NORMAN OK

0634 PM CDT THU OCT 18 2007

   

AREAS AFFECTED...LOWER MI...ERN IL...IN...

   

CONCERNING...TORNADO WATCH 724...

   

VALID 182334Z - 190130Z

   

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 724 CONTINUES.

   

THREAT FOR TORNADOES AS WELL AS PARTICULARLY DAMAGING WIND GUSTS HAS BECOME HIGH FROM SRN MI SWD.

   

SURFACE ANALYSIS SHOWS MAIN SURFACE DRYLINE/WIND SHIFT WELL TO THE WEST OVER WRN IL AND MO...WITH NUMEROUS STORMS TO THE E IN THE WARM SECTOR. SHEAR PROFILES ARE EXCEPTIONALLY STRONG...WITH 0-6KM SHEAR OF 70-80KT AND 0-1 SHEAR IN EXCESS OF 30 KT. PRIMARY STORM MODE IS THUS EXPECTED TO REMAIN SUPERCELLULAR WITH A THREAT OF TORNADOES...POSSIBLY STRONG...AND VERY STRONG WIND GUSTS.

   

WHILE INSTABILITY IS NOT PARTICULARLY HIGH...SURFACE ANALYSIS DOES SHOW DEWPOINTS RISING INTO THE MID 60S ALONG THE OH RIVER. A PERSISTENT AND STRONG LOW LEVEL JET MAY BRING THE HIGHER LEVELS OF MOISTURE NWD...POSSIBLY INCREASING THE TORNADO THREAT INTO IN AND WRN OH LATER THIS EVENING.

   

   ..JEWELL.. 10/18/2007

Mesoscale Discussion #2118


MESOSCALE DISCUSSION 2118

NWS STORM PREDICTION CENTER NORMAN OK

0751 PM CDT THU OCT 18 2007

   

AREAS AFFECTED...LWR OH VLY AND MID-SOUTH

   

CONCERNING...TORNADO WATCH 722...

   

VALID 190051Z - 190215Z

   

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 722 CONTINUES.

   

THE THREAT FOR TORNADOES...SOME POSSIBLY STRONG AND/OR LONG TRACKED...WILL CONTINUE TO INCREASE THROUGH LATE EVENING FROM SRN IND SWD INTO CNTRL/WRN KY...MIDDLE/WRN TN AND EXTREME NRN MS.  

   

NUMEROUS SUPERCELLS...A FEW EXHIBITING SIGNIFICANT LOW-LEVEL ROTATION...CONTINUE FROM WEST OF KSDF SWWD TO JUST E OF THE MS RVR IN NWRN MS AT 0030Z.  DOWNSTREAM AIR MASS CONTINUES TO DESTABILIZE OWING TO INCREASING BOUNDARY LAYER MOISTURE WITH 00Z BNA SOUNDING EXHIBITING ABOUT 1700 J/KG OF MLCAPE.  VWPS AND SOUNDINGS SHOW TREMENDOUS LOW-LEVEL SHEAR AND 50+ KTS OF 0-6KM SHEAR...ALL INDICATIVE OF SUPERCELLS WITH THE THREAT FOR STRONG TORNADOES OVER A VERY LARGE REAL ESTATE CENTERED ON THE LWR OH VLY/MIDWEST INTO THE MID-SOUTH.

   

THROUGH LATE EVENING...GREATEST POTENTIAL FOR TORNADOES WILL EXIST ACROSS MIDDLE/WRN TN NWD INTO IND WHERE MODELS FCST AN ACCELERATION OF THE SLY LLJ IN EXCESS OF 55 KTS BENEATH 95+ KTS OF MID-LEVEL SWLY FLOW.  EVENTUALLY...THE NUMBER OF STORMS MAY BEGIN TO MODULATE STORM MODE SOMEWHAT AS CELLS BEGIN TO MERGE.  BUT...SUCH STRONG AMBIENT SHEAR WILL MAINTAIN THE THREAT FOR EMBEDDED ROTATING STORMS WITH POSSIBLE TORNADOES AND HIGH WINDS.

   

   ..RACY.. 10/19/2007