2004

Mesoscale Discussion #0161


CONCERNING...TORNADO WATCH 19...

   

VALID 041443Z - 041545Z

   

...TORNADO WATCH #19 WILL BE REPLACED BY 16Z...

   

UPPER TROUGH IS FINALLY EJECTING NEWD INTO WEST TX THIS MORNING. LOW LEVEL RESPONSE TO THIS STRONG SHORTWAVE WILL BE A DEEPENING SFC LOW AS IT LIFTS NEWD ALONG EXISTING WARM FRONT ACROSS NWRN TX. IMPRESSIVE SHEAR PROFILES AND MORE THAN SUFFICIENT INSTABILITY WARRANT EXTENDING THE TORNADO WATCH DOWNSTREAM TO ACCOUNT FOR THE LIKELIHOOD OF SUPERCELLS AND TORNADOES.

Mesoscale Discussion #0162


CONCERNING...OUTLOOK UPGRADE 

   

VALID 041528Z - 041630Z

   

...AN UPGRADE TO A HIGH RISK OF SEVERE THUNDERSTORMS WILL BE ISSUED AT 1630Z...

   

A HIGH RISK OF SEVERE THUNDERSTORMS WILL BE ISSUED AT 1630Z DAY1 OUTLOOK.  AN OUTBREAK OF TORNADOES...DAMAGING WINDS AND LARGE HAIL WILL ACCOMPANY THE STRONGEST STORMS AS THEY DEVELOP NEWD ACROSS NRN TX...CENTRAL/ERN OK INTO NWRN AR.  REFER TO THE 1630Z DAY1 OUTLOOK FOR MORE DETAILS.

Mesoscale Discussion #0166


CONCERNING...TORNADO WATCH 22...

   

VALID 041902Z - 042030Z

   

...DANGEROUS WEATHER SITUATION FROM NORTHWEST TEXAS NEWD INTO SOUTHWEST AND CENTRAL OKLAHOMA...

   

WIDESPREAD WIND DAMAGE AND TORNADOES ARE LIKELY ACROSS NORTHWEST TEXAS DURING THE NEXT HOUR...AND WILL SHIFT RAPIDLY INTO SOUTHWEST AND CENTAL OKLAHOMA THROUGH THE AFTERNOON. THESE STORMS ARE EXPECTED TO REACH THE OKLAHOMA CITY METRO AREA AROUND 300 PM.

   

AT 18Z SURFACE LOW WAS LOCATED ABOUT 60 MILES WEST OF SPS AND WAS HEADING NEWD AT 65 KT. A WARM FRONT EXTENDS FROM THE SURFACE LOW NEWD TO THE OKLAHOMA CITY METRO AREA AND NEWD TO NEAR TULSA. A LINE OF SUPERCELLS IS ACCOMPANYING THE LOW PRESSURE SYSTEM AND ENVIRONMENTAL CONDITIONS ARE FAVORABLE FOR WIDESPREAD WIND DAMAGE AND TORNADOES WITH THESE STORMS. THE MOST INTENSE STORMS ARE EXPECTED TO BE LOCATED CLOSE TO THE LOW PRESSURE SYSTEM WITH THE POSSIBILITY OF STRONG TORNADOES AND WINDS IN EXCESS OF 80 MPH.

   

SOUTH OF THE LOW...A LINE OF SUPERCELLS IS MOVING ENEWD AT 60 KT THROUGH NORTHWEST TEXAS WITH TORNADOES AND WIND DAMAGE ALSO LIKELY.

Mesoscale Discussion #0396


CONCERNING...TORNADO WATCH 95...

   

VALID 202300Z - 210100Z

   

THE THREAT OF LOW-TOPPED SUPERCELLS CAPABLE OF PRODUCING TORNADOES CONTINUES IN VICINITY OF WARM FRONT EXTENDING WEST-EAST ACROSS THE WW 95 AREA. FRONT EXTENDS FROM ROUGHLY 25 NE MLI TO 45 S CGX TO 45 NW MIE AT 23Z. WARM FRONT WILL CONTINUE TO SHIFT NEWD DURING THE EVENING HOURS...WITH LOW-LEVEL WARM ADVECTION ALLOWING FOR SUFFICIENT DESTABILIZATION TO SUPPORT SEVERE THUNDERSTORMS INTO PORTIONS OF NRN IL AND NRN IND. SBCAPE VALUES OF 1000-1500 J/KG ARE PRESENT IN VICINITY OF SCATTERED SUPERCELLS ACROSS CENTRAL IL EWD INTO IND VICINITY. LOW-LEVEL HODOGRAPH CURVATURE IS VERY IMPRESSIVE PER IND VAD WIND PROFILE...CONTRIBUTING TO 0-3KM SRH VALUES IN EXCESS OF 400 M2/S2 ALONG THE WARM FRONT. DESPITE MARGINAL CAPE...LOW LCL HEIGHT ENVIRONMENT COMBINED WITH VERY FAVORABLE LOW-LEVEL SHEAR WILL HELP TO SUSTAIN LOW TOPPED SUPERCELLS WITH TORNADOES DURING THE NEXT 2-3 HOURS.

Mesoscale Discussion #0675


CONCERNING...TORNADO WATCH 193...

   

VALID 130008Z - 130115Z

   

OBJECTIVE ANALYSES CONTINUE TO SUPPORT SUPERCELLS WITH TORNADOES AND LARGE HAIL/DAMAGING WINDS ACROSS CENTRAL/SRN KS INTO NWRN OK. STRONGEST LOW-LEVEL CONVERGENCE EXISTS AT THE INTERSECTION OF SURFACE LOW/DRY LINE/QUASI-STATIONARY KS BOUNDARY FROM BARBER COUNTY TO PRATT/COMANCHE COUNTIES...AND NEWD ALONG SURFACE FRONT TO ERN PORTION OF CENTRAL KS AROUND MARION COUNTY.  DEEP LAYER SHEAR OF 35-55 KT AND A VERY UNSTABLE AIR MASS /100 MB MLCAPE 2500-4000 J/KG/ IN THE WARM SECTOR EXTENDS ACROSS S CENTRAL AND SW KS.

   

ALTHOUGH A STORM EXISTS ACROSS THE NERN PORTION OF WW 193 OVER MARION COUNTY...WEAK VIL VALUES SUGGEST STORM IN THIS AREA ARE STRUGGLING TO SUSTAIN UPDRAFTS.  HOWEVER...GIVEN A VERY UNSTABLE AIR MASS OVER THIS REGION WITH DEEP LAYER SHEAR ON THE ORDER OF 35-40 KT ADJACENT TO WW 193...SUPERCELLS WOULD BE LIKELY.  THUS... PORTIONS OF ERN KS WILL CONTINUE TO BE MONITORED FOR A WW IF ACTIVITY CAN INCREASE IN INTENSITY.

Mesoscale Discussion #0798


CONCERNING...SEVERE THUNDERSTORM WATCH 231...

   

VALID 211859Z - 212100Z

   

WW MAY NEED TO BE REPLACED WITH NEW TORNADO WATCH ACROSS PARTS OF NORTH CENTRAL/NORTHEAST IOWA SHORTLY.

   

WEAK SHORT WAVE ASSOCIATED WITH MID-LEVEL JET STREAK NOW NOSING INTO SOUTHERN MINNESOTA IS SUPPORTING EVOLUTION OF GROWING CLUSTER OF STORMS ACROSS THE LA CROSSE AREA.  ACTIVITY APPEARS TO BE FOCUSED ALONG BAROCLINIC ZONE IN THE 925 TO 850 MB LAYER...NORTH OF CONVECTIVE OUTFLOW WHICH HAS REMAINED GENERALLY STATIONARY FROM THE FORT DODGE AREA SOUTHEASTWARD TOWARD MOLINE.  BOUNDARY LAYER NORTH OF OUTFLOW REMAINS GENERALLY COOL STABLE...LIMIT DAMAGING WIND THREAT WITH CONVECTIVE SYSTEM AS IT PROGRESSES ACROSS CENTRAL WISCONSIN...NORTHWEST OF MADISON NEXT COUPLE OF HOURS. HOWEVER...RISK OF LARGE HAIL WILL PERSIST.

   

OTHERWISE...NEW CONVECTION CONTINUES TO DEVELOP/INTENSIFY NEAR INTERSECTION OF OUTFLOW AND SYNOPTIC SURFACE FRONT...NEAR/EAST OF FORT DODGE.  ACTIVITY APPEARS TO BE INCREASINGLY ROOTED IN VERY MOIST UNSTABLE BOUNDARY LAYER WITH MEAN MIXED LAYER CAPE IN EXCESS OF 2000 J/KG.  FURTHER INTENSIFICATION IS LIKELY NEXT COUPLE OF HOURS AS IT DEVELOPS EAST SOUTHEASTWARD.  STRONGER 2 HOUR SURFACE PRESSURE FALL CENTER HAS DEVELOPED ACROSS THE WATERLOO/ MARSHALLTOWN AREA...WHERE HODOGRAPHS ARE BECOMING INCREASINGLY FAVORABLE FOR TORNADIC SUPERCELLS.

Mesoscale Discussion #0811


CONCERNING...TORNADO WATCH 243...

   

VALID 220301Z - 220430Z

   

THREAT FOR TORNADIC SUPERCELLS REMAINS ACROSS WW 243...ESPECIALLY ACROSS NRN HALF OF TORNADO WW. IN ADDITION...VERY LARGE HAIL REMAINS POSSIBLE ACROSS ALL OF WW 243 OWING TO VERY UNSTABLE AIRMASS/FAVORABLE SHEAR PROFILES. WW 243 CONTINUES.

   

ONGOING SUPERCELLS ACROSS NE/NCNTRL NEB INTO FAR SE SD HAVE A HISTORY OF PRODUCING TORNADOES/VERY LARGE HAIL. CONTINUATION OF TORNADIC THREAT WILL REMAIN ACROSS NCNTRL/NE NEB AND FAR SE SD THIS EVENING...ESPECIALLY INVOF QUASI-STATIONARY FRONT...WHERE LOW LEVEL HODOGRAPH LENGTH/CURVATURE IS MAXIMIZED IN MIDST OF RELATIVELY LOW LCLS/LFCS. 

   

FURTHER SOUTH ACROSS FAR SCNTRL NEB/NCNTRL KS...HIGHER LCLS/LFCS SUGGESTS RELATIVELY LESSER TORNADIC THREAT WITH HIGHER BASED SUPERCELLS...WITH MAIN HAZARD BEING LARGE HAIL.

Mesoscale Discussion #0823


CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

   

VALID 222002Z - 222100Z

   

...TORNADIC SUPERCELLS SHOULD DEVELOP BY EARLY EVENING FROM SRN NEB INTO SRN IA.  TORNADO WATCH WILL BE ISSUED BY 21Z...

   

RAPID AIRMASS DESTABILIZATION IS EXPECTED TO CONTINUE ACROSS THE LOWER MO VALLEY INTO SOUTH CENTRAL NEB OVER THE NEXT FEW HOURS.  LATEST DIAGNOSTIC FIELDS INDICATE AN AXIS OF 3000-4000 J/KG SBCAPE CURRENTLY EXTENDS NWWD ALONG THE NEB/KS BORDER AHEAD OF INCREASING THUNDERSTORM ACTIVITY SPREADING EWD OFF THE HIGH PLAINS.  A SIGNIFICANT INCREASE IN CONVECTION IS OCCURRING AHEAD OF SHORTWAVE TROUGH...INDICATIVE OF LARGE SCALE ASCENT WHICH WILL SPREAD EWD THIS EVENING.  IN ADDITION...A RAPID INCREASE IN LLJ WILL IMPINGE ON E-W BOUNDARY ALONG THE KS/NEB...IA/MO BORDERS OVER THE NEXT 3-6 HOURS. SUPERCELL THUNDERSTORM DEVELOPMENT IS EXPECTED WITHIN THE WARM ADVECTION ZONE WHERE SHEAR/INSTABILITY STRONGLY SUPPORTS TORNADIC DEVELOPMENT. A FEW TORNADOES MAY BE STRONG...IN ADDITION TO VERY LARGE HAIL.  TORNADO WATCH WILL BE ISSUED BY 21Z.

Mesoscale Discussion #0829


CONCERNING...TORNADO WATCH 251...

   

VALID 230011Z - 230145Z

   

VERY DANGEROUS SITUATION CONTINUES WITHIN WW ALONG WARM FRONT AND E OF DRYLINE, FROM NEAR FRANKLIN/ADAMS COUNTIES NEWD TOWARDS OMAHA AND INTO WRN IA.

   

LOW LEVEL SHEAR WILL CONTINUE TO INCREASE AS LOW LEVEL JET STRENGTHENS. VERY STRONG INSTABILITY COMBINED WITH SHEAR PARAMETERS IN PLACE WILL CONTINUE THE THREAT OF STRONG TORNADOES.

   

GREATEST THREAT...CURRENTLY OVER ERN NEB...WILL SHIFT EWD WITH TIME...WITH STRONG TORNADOES EXPECTED INTO CENTRAL AND SWRN IA THIS EVENING.

Mesoscale Discussion #0831


CONCERNING...OUTLOOK UPGRADE 

   

VALID 230023Z - 230130Z

   

01Z OUTLOOK WILL UPGRADE PORTIONS OF THE CURRENT MDT RISK TO HIGH RISK BASED ON LONG-TRACK STRONG TO VIOLENT TORNADO POTENTIAL OVER PARTS OF SERN NEBRASKA AND SOUTHWEST IOWA THIS EVENING.

Mesoscale Discussion #0833


CONCERNING...TORNADO WATCH 254...

   

VALID 230158Z - 230330Z

   

CONDITIONS REMAIN VERY FAVORABLE FOR SUPERCELLS AND TORNADOES ACROSS THE WRN PORTIONS OF TORNADO WATCH 254. WIDELY SCATTERED STRONG TO ISOLD SEVERE TSTMS ARE ALSO POSSIBLE ACROSS PARTS OF NRN IL.

   

LATEST MESOANALYSIS PLACES DEEPENING SURFACE LOW OVER SERN NEB WITH A STRONG AND CONVERGENT WARM FRONT EXTENDING EWD ACROSS SRN IA. NUMEROUS SUPERCELLS CONTINUE TO DEVELOP ON THE WARM FRONT OVER IA WITH ACTIVITY NOW MERGING INTO A LARGE MASS OF DEEP CONVECTION FROM GUTHRIE COUNTY ENEWD TO MARSHALL AND TAMA COUNTIES. INTENSE CLUSTER OF STORMS...WITH A POSSIBLE BOW AND COMMA HEAD...WAS FORMING OVER SHELBY COUNTY AND WILL MOVE INTO THE WRN PARTS OF WATCH 245 SHORTLY. ADDITIONAL CELLS HAVE RECENTLY APPEARED ACROSS SRN JOHNSON COUNTY.

   

STRONG FORCING WITH THE DEVELOPING SURFACE LOW WHICH WILL TRACK INTO SWRN IA OVER THE NEXT FEW HOURS...COUPLED WITH 50-70 WLY MID LEVEL FLOW AND INTENSIFYING LLJ...WILL CONTINUE TO SUPPORT WIDESPREAD INTENSE TSTM DEVELOPMENT. STRONG STORM ROTATION AND POSSIBLE LONG TRACK TORNADOES AS WELL AS BOWING LINE SEGMENTS WITH DAMAGING WINDS WILL BE LIKELY ALONG WITH VERY LARGE HAIL.

Mesoscale Discussion #0836


CONCERNING...TORNADO WATCH 256...

   

VALID 230433Z - 230600Z

   

...DANGEROUS BOW ECHO MOVING ACROSS SRN IA...

   

INTENSE BOX ECHO COMPLEX MOVING AT 50-60KT AND PRODUCING WINDS POSSIBLY IN EXCESS OF 80KT CONTINUES MOVING EAST ACROSS SRN IA. APEX OF THE BOW WILL CONTINUE TO ENCOUNTER INTENSE INFLOW AND LOW LEVEL SHEAR AS IT ENCOUNTERS OUTFLOW BOUNDARY EXTENDING ENEWD FROM MADISON COUNTY. DAMAGING TO EXTREME WINDS MAY OCCUR ACROSS NRN WARREN/MARION COUNTIES EAST TO JASPER AND POWESHIEK COUNTIES OVER THE NEXT HOUR.

   

TO THE WEST...ANOTHER BOWING LINE OF INTENSE CONVECTION WAS DEVELOPING EAST FROM OTOE AND JOHNSON COUNTIES IN EXTREME SERN NEB. THIS ACTIVITY WAS TRACKING EAST AT 50KT AND WILL PROBABLY PRODUCE WIND DAMAGE ALONG THE MO/IA BORDER WITHIN THE NEXT HOUR.

Mesoscale Discussion #0869


CONCERNING...TORNADO WATCH 273...

   

VALID 241939Z - 242115Z

   

DEVELOPING TSTMS WILL BE CAPABLE OF STRONG TORNADOES AND VERY LARGE HAIL.

   

AS OF 19Z...MESOANALYSIS PLACED PRIMARY SURFACE LOW W OF CNK WITH ATTENDANT WARM FRONT ARCING NEWD INTO SERN NEB/FAR NWRN MO AND THEN SEWD INTO E-CNTRL MO. MEANWHILE...DRYLINE HAS MIXED EWD TO JUST W OF SLN/HUT. SATELLITE/RADAR IMAGERY INDICATE TSTMS DEVELOPING NE OF SURFACE LOW/WARM FRONT INTERSECTION OVER CLAY/ADAMS COUNTIES IN S-CNTRL NEB WITH AN ADDITIONAL SEVERE TSTM BECOMING BETTER ESTABLISHED ALONG WARM FRONT OVER RICHARDSON/NEMAHA COUNTIES IN FAR SERN NEB. AIRMASS S OF DEVELOPING TSTMS HAS BECOME EXTREMELY UNSTABLE THIS AFTERNOON /PER 18Z TOP SOUNDING/ WHERE MLCAPES HAVE INCREASED TO 4000 J/KG.

   

EXPECT CONTINUED INTENSIFICATION OF ONGOING TSTMS OVER THE NEXT FEW HOURS WITH ADDITIONAL DEVELOPMENT INVOF OF SURFACE LOW EWD ALONG WARM FRONT. BACKED LOW-LEVEL WINDS WITHIN FRONTAL ZONE COUPLED WITH MOIST BOUNDARY-LAYER CONDITIONS /LCL HEIGHTS 800-1000 M/ WILL SUPPORT STRONG LOW-LEVEL MESOCYCLONES WITH THE POTENTIAL FOR STRONG AND POTENTIALLY LONG-TRACKED TORNADOES. ADDITIONALLY... EXTREME BUOYANCY ALONG WITH SUPERCELL STORM STRUCTURES WILL PROMOTE VERY LARGE HAIL GROWTH.

Mesoscale Discussion #0873


CONCERNING...SEVERE THUNDERSTORM POTENTIAL 277...

   

VALID 242143Z - 242230Z

   

CORRECTED FOR UGC CODING

   

A NEW WATCH WILL BE ISSUED TO THE EAST OF WW 277.

   

NUMEROUS SUPERCELLS ACROSS SEVERE TSTM WATCH 277 AT THIS TIME. LARGE HAIL...DAMAGING WINDS...AND ISOLD TORNADOES ARE QUITE LIKELY FROM THIS ACTIVITY. HIGHEST TORNADO THREAT IN THE SHORT TERM APPEARS TO BE WITH RIGHT-MOVING SUPERCELL MOVING INTO DELAWARE COUNTY IN SERN NY. THIS APPEARS TO BE A DANGEROUS STORM. ACTIVITY CONTINUES TO DEVELOP WITHIN VERY UNSTABLE AIRMASS CO-LOCATED WITH SURFACE LOW. PORTIONS OF THE REGION MAY NEED TO BE UPGRADED TO A TORNADO WATCH SHORTLY.

Mesoscale Discussion #0878


CONCERNING...TORNADO WATCH 275...

   

VALID 242357Z - 250045Z

   

CORRECTED SPELLING ON GRAPHIC

   

EXTREMELY DANGEROUS CONDITIONS DEVELOPING FOR STRONG LONG TRACK  TORNADOES ACROSS PARTS OF NERN KS NEXT 1-2 HOURS. ONE LONG TRACK SUPERCELL CONTINUES TO DEVELOP SEWD AT ABOUT 25KT TOWARD NERN RILEY COUNTY KS. ADDITIONAL DEVELOPMENT IS NOTED ON HORIZONTAL CONVECTIVE ROLLS (HCRS) TO THE SOUTH OF TOPEKA. ENVIRONMENT ACROSS THE WATCH AREA REMAINS PRIME FOR EXPLOSIVE TSTM DEVELOPMENT. SHEAR PARAMETERS ARE ALSO IDEAL FOR LOW LEVEL STORM ROTATION...VERY LARGE AND DAMAGING HAIL AND STRONG TORNADOES.

Mesoscale Discussion #0880


CONCERNING...TORNADO WATCH 275...281...

   

VALID 250115Z - 250245Z

   

...VERY DANGEROUS TORNADO AND DAMAGING WIND SITUATION ACROSS AREAS OF NERN KS AND NRN MO THIS EVENING...

   

TWO VERY LARGE SUPERCELL STORMS WERE MOVING EAST ACROSS DOUGLAS AND OSAGE COUNTIES IN ERN KS AND WILL CONTINUE TO TRACK EAST WITH POSSIBLE DESTRUCTIVE TORNADOES CROSSING PORTIONS OF NRN DOUGLAS COUNTY AND CNTRL AND ERN OSAGE COUNTY IN THE NEXT HOUR. A NEW CELL HAS ALSO DEVELOPED OVER LYON COUNTY. THESE POTENTIALLY TORNADIC STORMS MAY THEN CONTINUE ON EAST INTO PARTS OF JOHNSON/FRANKLIN COUNTIES...AND THE SOUTH KANSAS CITY METRO.

   

TORNADO THREAT IS ALSO VERY HIGH WITH A PERSISTENT AND INTENSE SUPERCELL ANCHORED TO THE WARM FRONT OVER LINN AND MACON COUNTIES IN NERN MO.

   

VERY STRONG SQUALL LINE WAS DEVELOPING SEWD ACROSS NERN KS AND NWRN NWRN/NRN MO...FROM BROWN/DONIPHAN COUNTIES IN KS NEWD TO GRUNDY AND MERCER COUNTIES IN NRN MO...THIS LINE MAY CONTAIN EMBEDDED ROTATING STORMS/TORNADOES AND EXTREME WIND SPEEDS AS IT DEVELOPS ESEWD ACROSS ERN KS/NRN MO...AND THE KANSAS CITY AREA OVER THE NEXT FEW HOURS.

Mesoscale Discussion #0972


CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

   

VALID 291802Z - 292000Z

   

INITIATION OF INTENSE CONVECTION APPEARS POSSIBLE WITHIN NEXT 2 TO 3 HOURS. STORMS WILL RAPIDLY BECOME SEVERE...WITH TRANSITION TO LONG-LIVED SUPERCELLS WITH POTENTIAL FOR STRONG TORNADOES THEREAFTER.

   

WATER VAPOR IMAGERY INDICATES PERSISTENT BAND OF LOW/MID-LEVEL MOISTENING/LARGE-SCALE ASCENT NOW SHIFTING NORTHEASTWARD ACROSS THE TEXAS/OKLAHOMA PANHANDLE REGION.  THIS APPEARS TO BE IN RESPONSE TO WARM ADVECTION IN WAKE OF SHORT WAVE TROUGH ALREADY LIFTING OUT OF THE CENTRAL PLAINS...AND AHEAD OF SHORT WAVE/JET STREAK DIGGING ACROSS THE GREAT BASIN.  STRONGER FORCING WILL CONTINUE INTO THE CENTRAL PLAINS EARLY THIS AFTERNOON...AND BY THE 20-21Z TIME FRAME APPEARS LIKELY TO CURVE ALONG AN AXIS FROM THE VICINITY OF HILL CITY THROUGH AREAS NEAR/NORTH AND EAST OF SALINA.

   

OBJECTIVE ANALYSIS INDICATES BOUNDARY LAYER IS ALREADY BECOMING VERY UNSTABLE ACROSS CENTRAL/NORTHERN KANSAS...EAST OF SURFACE LOW NOW DEVELOPING TO THE WEST OF RUSSELL.  LOWER/MID TROPOSPHERIC CAP IS CURRENTLY INHIBITING CONVECTIVE DEVELOPMENT...BUT AS LARGE-SCALE ASCENT INCREASES IN CAPPING LAYER NEXT FEW HOURS...STORMS LIKELY WILL DEVELOP.

   

CURRENT INDICATIONS ARE THAT INITIATION COULD OCCUR AS EARLY AS 21Z EAST OF HILL CITY...WITH SUBSEQUENT DEVELOPMENT EAST NORTHEASTWARD INTO THE CONCORDIA KS/HASTINGS AND BEATRICE NEB AREAS. GIVEN MAGNITUDE OF POTENTIAL INSTABILITY...STORMS WILL RAPIDLY BECOME SEVERE WITH VERY LARGE HAIL...BEFORE HODOGRAPHS BECOME INCREASINGLY FAVORABLE FOR TORNADIC SUPERCELLS IN THE 29/21-30/00Z TIME FRAME. BY THIS TIME...BOUNDARY LAYER DEW POINTS ARE EXPECTED TO CLIMB TO AROUND 70F...CONTRIBUTING TO FAVORABLE LOW-LEVEL THERMODYNAMIC ENVIRONMENT FOR STRONG...POSSIBLY LONG-TRACK...TORNADOES.

Mesoscale Discussion #0976


CONCERNING...TORNADO WATCH 322...

   

VALID 292157Z - 292300Z

   

SCATTERED SUPERCELLS CONTINUE TO MATURE ALONG/EAST OF DRY LINE FROM BECKHAM COUNTY OK...NNEWD INTO STAFFORD COUNTY KS.  THIS ACTIVITY SHOULD CONTINUE TO INTENSIFY AS CONVECTION ENCOUNTERS INCREASINGLY MOIST BOUNDARY LAYER DOWNSTREAM.  TORNADO THREAT WILL INCREASE INTO SOUTH CENTRAL KS/NORTH CENTRAL OK OVER THE NEXT FEW HOURS.

Mesoscale Discussion #0978


CONCERNING...TORNADO WATCH 323...

   

VALID 292216Z - 292315Z

   

EXPANDING CLUSTER OF SUPERCELLS IS DEVELOPING NWD FROM MITCHELL COUNTY KS...NWD INTO FILLMORE COUNTY NEB.  STRENGTHENING LLJ OVER CENTRAL KS WILL MAINTAIN DEEP CONVERGENCE AHEAD OF SFC LOW INTO THIS REGION SUPPORTING THE CONTINUED DEVELOPMENT OF POTENTIAL TORNADIC DEVELOPMENT.  SATELLITE IMAGERY SUPPORTS MASS FIELDS WITH EXPLOSIVE ANVIL EXPANSION ATOP THIS MATURING CLUSTER.  WITH TIME SUPERCELLS WILL SPREAD NEWD INTO REMAINDER OF ERN NEB.

Mesoscale Discussion #0985


CONCERNING...TORNADO WATCH 327...328...

   

VALID 300423Z - 300530Z

   

ARCING LINEAR MCS HAS EVOLVED ACROSS CENTRAL NEB INTO NRN KS.  THIS ACTIVITY IS SURGING NEWD ACROSS NEB AT ROUGHLY 40KT...WITH SOMEWHAT SLOWER MOVEMENT ALONG THE COLD FRONT INTO KS.  IT APPEARS CONVECTIVE DEVELOPMENT MAY STRUGGLE TO BUILD SOUTH OF INTERSTATE 70 IN THE NEAR TERM.  OTHER TORNADIC ISOLATED STORMS PERSIST JUST EAST OF LOW LEVEL JET ACROSS NWRN MO.  THIS MAY EXPLAIN THE VERY SLOW MOVEMENT AND THE RELUCTANCE FOR THIS ACTIVITY TO LIFT SIGNIFICANTLY NEWD.

   

FARTHER SOUTH...MORE DISCRETE LONGER LIVED TORNADIC SUPERCELLS HAVE YET TO DISSIPATE ACROSS SRN KS AND NRN OK...ESPECIALLY THE LINCOLN/CREEK COUNTIES OK THUNDERSTORM.  VERY STRONG LOW LEVEL SHEAR APPEARS TO BE AIDING TORNADIC POTENTIAL WITH THIS SUPERCELL.

Mesoscale Discussion #0996


CONCERNING...TORNADO WATCH 330...333...334...

   

VALID 301944Z - 302145Z

   

RISK OF STRONG TORNADOES IS INCREASING.  NEW WW WILL BE NEEDED WITHIN NEXT HOUR OR TWO ACROSS NORTHEAST/EAST CENTRAL ARKANSAS.

   

SUPERCELLS ARE INTENSIFYING FROM THE ARKLATEX INTO THE MISSOURI OZARKS AS PEAK HEATING HOURS ARE APPROACHED.  VERTICAL SHEAR PROFILES ARE STRENGTHENING AS STRONGER FLOW IN BASE OF LARGER SCALE TROUGH...BETWEEN POLAR AND SUBTROPICAL JET AXIS...OVERSPREADS REGION.  THOUGH LOW-LEVEL HODOGRAPHS ARE NOT STRONGLY CURVED...SHEAR BENEATH 40 KT SOUTHWESTERLY LOW-LEVEL JET AXIS IS STILL STRONG AND SUPPORTIVE OF TORNADOES GIVEN VERY MOIST AND POTENTIALLY BUOYANT BOUNDARY LAYER WITH LOWER/MID 70S DEW POINTS.

   

LONG-LIVED MULTIPLE TORNADO PRODUCING MESOCYCLONES APPEAR LIKELY TO EVOLVE...WITHIN AND AHEAD OF BROKEN SQUALL LINE...WITH POTENTIAL FOR STRONG TORNADOES.  AS MID-LEVEL INHIBITION CONTINUES TO WEAKEN ACROSS CENTRAL/EASTERN ARKANSAS WITH APPROACH OF UPPER TROUGH...ACTIVITY WILL DEVELOP INTO AREAS NEAR/WEST THROUGH NORTHEAST OF LITTLE ROCK AR BY 31/00Z.

Mesoscale Discussion #0998


CONCERNING...TORNADO WATCH 331...335...

   

VALID 302005Z - 302200Z

   

THREAT FOR TORNADOES IS EXTREMELY HIGH OVER SRN IND AND CENTAL AND ERN KY.  THREAT WILL MOVE INTO SWRN OHIO OVER THE NEXT SEVERAL HOURS AND ANOTHER TORNADO WATCH APPEARS LIKELY LATER THIS AFTERNOON.

   

LATEST SURFACE ANALYSIS SHOWS WARM FRONT FROM CENTRAL INDIANA SEWD ACROSS NRN AND ERY KY. LIFT ALONG THIS FRONT AND COMBINATION OF STRONG/ ENHANCED LOW LEVEL SHEAR ALONG WITH CONTINUED DESTABILIZATION WILL KEEP THE THREAT OF TORNADOES HIGH.  A FEW TORNADOES COULD BE PARTICULARLY STRONG.

Mesoscale Discussion #0999


CONCERNING...TORNADO WATCH 332...

   

VALID 302016Z - 302215Z

   

CONTINUE REMAINING VALID PORTION OF WW.  NEW WW WILL BE NEEDED ACROSS THE REMAINDER OF NORTHERN ILLINOIS/SOUTHERN WISCONSIN WITHIN NEXT HOUR OR TWO.

   

INCREASING/INTENSIFYING CONVECTION IS ONGOING IN INSTABILITY AXIS ALONG/AHEAD OF INITIAL WEAK COLD FRONT ADVANCING INTO THE MID/UPPER MISSISSIPPI VALLEY.  MOST INTENSE THUNDERSTORMS REMAIN NEAR/SOUTHEAST OF WAVE AT INTERSECTION OF FRONT AND RETREATING OUTFLOW BOUNDARY...NOW NORTHEAST OF KEOKUK IA. THIS ACTIVITY IS BEING SUPPORTED BY FORCING IN EXIT REGION OF CYCLONIC POLAR JET STREAK NOSING INTO THE MISSOURI OZARKS.  ENHANCED LOW-LEVEL HODOGRAPHS NEAR UPPER JET AXIS CONTINUE TO SUPPORT POTENTIAL FOR STRONG TORNADOES WITH ONGOING SUPERCELLS...IN VERY MOIST BOUNDARY LAYER WITH 70F DEW POINTS AND CAPE UP TO 2000 J/KG.

   

FAVORABLE LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION MAY SUPPORT UPSCALE DEVELOPMENT INTO LARGER MESOSCALE CONVECTIVE SYSTEM NORTHEASTWARD ACROSS NORTHERN ILLINOIS THROUGH 31/00Z.

Mesoscale Discussion #1000


CONCERNING...TORNADO WATCH 330...333...334...336...

   

VALID 302210Z - 302345Z

   

...HIGH TORNADIC THREAT ACROSS MUCH OF THE LOWER MS VALLEY INTO SRN IL...

   

ENVIRONMENTAL CONDITIONS ARE BECOMING EXTREMELY FAVORABLE FOR DAMAGING TORNADOES ACROSS PORTIONS OF THE LOWER MS VALLEY INTO SRN IL.  VERY STRONG SFC-1KM SHEAR...ON THE ORDER OF 30M/S...HAS DEVELOPED ACROSS REGION THAT HAS A WELL ESTABLISHED TROPICAL AIRMASS...SFC DEW POINTS IN THE MID 70S.  IN ADDITION...LONG TRACK SUPERCELLS HAVE DEVELOPED AND ARE DISPLAYING STRONG TORNADIC SIGNATURES...ESPECIALLY ACROSS AR.

Mesoscale Discussion #1187


CONCERNING...OUTLOOK UPGRADE 

   

VALID 111510Z - 111645Z

   

AN UPGRADE TO A MODERATE RISK OF SEVERE THUNDERSTORMS IS PLANNED ON THE 1630Z DAY 1 OUTLOOK ACROSS NRN IA...SRN MN...AND SWRN WI.

   

CONVECTIVE DEVELOPMENT IS EXPECTED ACROSS N-CENTRAL IA NWD INTO SRN MN DURING MID-LATE AFTERNOON...WITH SUFFICIENT CAPE/SHEAR FOR SUPERCELLS. ACTIVITY IS EXPECTED TO MOVE EWD INTO SWRN WI BY LATE EVENING. POTENTIAL FOR TORNADOES...PARTICULARLY IN VICINITY OF THE WARM FRONT EXPECTED TO EXTEND NW-SE ACROSS S-CENTRAL MN LATE THIS AFTERNOON...WARRANTS THE UPGRADE TO MODERATE RISK. ADDITIONAL METEOROLOGICAL DETAILS ARE FORTHCOMING IN THE CONVECTIVE OUTLOOK.

Mesoscale Discussion #1645


CONCERNING...TORNADO WATCH 619...

   

VALID 131839Z - 131945Z

   

SEVERE THUNDERSTORMS ARE RAPIDLY DEVELOPING ON THE OUTFLOW FROM THE INTENSE TORNADIC SUPERCELL NOW MOVING SEWD THRU LA SALLE COUNTY. THESE NEW STORMS IN SRN LEE AND NRN BUREAU COUNTY ARE IN A VERY FAVORABLE ENVIRONMENT TO BECOME POTENTIALLY TORNADIC SUPERCELLS AS WELL.  THE AIR MASS FEEDING THE STORMS FROM THE WEST IS EXTREMELY UNSTABLE WITH MLCAPES IN EXCESS OF 4000 J/KG ALONG WITH 30-40 KT OF DEEP LAYER SHEAR.

Mesoscale Discussion #1726


CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

   

VALID 182206Z - 190030Z

   

THUNDERSTORMS ARE EXPECTED TO DEVELOP FROM PARTS OF ERN ND THROUGH NW MN BY 23-00Z. SUPERCELLS WITH LARGE HAIL...ISOLATED TORNADOES AND DAMAGING WIND GUSTS WILL BE THE MAIN INITIAL THREATS. WW WILL LIKELY BE NEEDED WITHIN THE NEXT HOUR OR TWO.

   

THIS EVENING A SURFACE TROUGH EXTENDS FROM NERN ND SWWD TO A SURFACE LOW IN S CNTRL ND. A BOUNDARY INDUCED BY EARLIER CLOUDS AND PRECIPITATION OVER MN EXTENDS N-S ALONG THE ND-MN BORDER. THE ATMOSPHERE HAS BECOME QUITE UNSTABLE ACROSS ERN ND WITH MLCAPE FROM 2500 TO 3000 J/KG. THE THETA-E GRADIENT IS SHARP E OF THE N-S BOUNDARY INTO WRN MN WHERE MLCAPE DROPS OFF TO LESS THAN 1500 J/KG. MODEST SWLY LOW LEVEL JET MAY INCREASE IN RESPONSE TO SHORTWAVE TROUGH DROPPING SEWD INTO ND THIS EVENING. THIS WILL RESULT IN DESTABILIZATION EWD WITH TIME INTO NWRN MN. STORMS MAY DEVELOP NEXT HOUR OR TWO IN CONVERGENCE ZONE ALONG THE SURFACE TROUGH ACROSS NERN ND. SHEAR PROFILES EXHIBIT VEERING IN THE LOW LEVELS WITH 0-1 KM STORM RELATIVE HELICITY FROM 100 TO 150 M2/S2 AND 0-6 KM SHEAR 35 TO 40 KT...SUPPORTIVE OF SUPERCELLS. LOW LEVEL HODOGRAPHS WILL INCREASE FURTHER AS THE LOW LEVEL JET UNDERGOES SOME STRENGTHENING THIS EVENING. OTHER STORMS MAY DEVELOP IN ZONE OF INCREASING LOW LEVEL WARM ADVECTION AND DESTABILIZATION OVER NWRN MN.


**This MCD preceded the high-end F4 near Marion, ND

Mesoscale Discussion #1987


CONCERNING...TORNADO WATCH 749...

   

VALID 131504Z - 131630Z

   

GREATEST POTENTIAL FOR ISOLATED TORNADOES THROUGH 16-17Z APPEARS TO BE INTERIOR SRN PENINSULA W/S OF LAKE OKEECHOBEE.

   

CONVECTIVE BAND ATTENDANT TO HURRICANE CHARLEY HAS INTENSIFIED OVER THE PAST HOUR FROM PORTIONS OF MIAMI-DADE/MONROE COUNTIES NNWWD INTO COLLIER AND HENDRY COUNTIES. SYNTHESIS OF LATEST OBJECTIVE FIELDS AND OBSERVATIONAL DATA INDICATES A QUITE FAVORABLE ENVIRONMENT FOR SUPERCELLS AND ISOLATED TORNADOES AS MLCAPES HAVE INCREASED TO 1000-1500 J/KG WITH 0-1KM SRH VALUES CURRENTLY 150-200 M2/S2.

   

THIS SAME GENERAL CORRIDOR IS EXPECTED TO REMAIN FAVORABLE FOR ISOLATED TORNADOES WITH ANY SUBSEQUENT CONVECTIVE DEVELOPMENT THROUGH 16-17Z. AS CHARLEY CONTINUES NWD THIS AFTERNOON...EXPECT A CORRESPONDING SHIFT OF STRONGER SHEAR AND INSTABILITY TO LOCATIONS W OF U.S. HIGHWAY 27 AND S OF INTERSTATE 4.

Mesoscale Discussion #2219


CONCERNING...TORNADO WATCH 825...

   

VALID 160335Z - 160530Z

   

TORNADO WATCH 825 REMAINS IN EFFECT FOR SRN AL...SWRN GA AND FL PNHDL AND IS SET TO EXPIRE AT 07Z.  ANOTHER TORNADO WATCH WILL BE NEEDED AFTER THAT TIME...AND THE NRN EDGE COULD BE SHIFTED FARTHER INTO CNTRL AL AND WCNTRL GA.

   

THE CENTER OF HRCN IVAN CONTINUES TO MOVE CLOSER TO SHORE...0330Z POSITION 40NM SOUTH OF THE AL BORDER. OUTER SPIRAL RAINBAND THAT HAS BEEN ROTATING NWWD ACROSS THE CNTRL FL PNHDL INTO SERN AL HAS INTENSIFIED AGAIN.  USING A STORM MOTION OF 150/45...STORM RELATIVE HELICITY VALUES CALCULATED OFF THE DOTHAN VWP ARE IN EXCESS OF 530 M2/S2. STRONGER WIND FIELDS WILL EXPAND NWD INTO SRN AL AND SWRN GA THROUGH FRIDAY MORNING AND THE TORNADO THREAT WILL CORRESPONDINGLY TRANSLATE NWD.

Mesoscale Discussion #2231


CONCERNING...OUTLOOK UPGRADE 

   

VALID 171503Z - 171630Z

   

MUCH OF CNTRL AND PARTS OF ERN NC INTO SRN VA WILL BE UPGRADED TO MODERATE RISK ON THE 1630Z OUTLOOK TO ACCOUNT FOR INCREASING THREAT OF TORNADOES INTO THE AFTERNOON.

Mesoscale Discussion #2442


CONCERNING...TORNADO WATCH 885...

   

VALID 232330Z - 240130Z

   

CONTINUE TORNADO WW.  RISK OF ISOLATED STRONG TORNADOES APPEARS LIKELY TO INCREASE ACROSS CENTRAL/NORTHEAST LOUISIANA NEXT COUPLE HOURS.

   

BROAD AREA OF CONVECTION CONTINUES BENEATH DIFLUENT/DIVERGENT UPPER FLOW ASSOCIATED WITH COUPLED HIGH LEVEL JET STREAKS.  THIS AREA OF UPPER FORCING WILL CONTINUE TO LIFT NORTHWARD THROUGH THE LOWER MISSISSIPPI VALLEY...TOWARD THE LOWER OHIO VALLEY OVERNIGHT. 

   

MOST INTENSE THUNDERSTORMS...WITH RELATIVELY HIGH PROBABILITY OF CONTINUING TORNADIC ACTIVITY...WILL REMAIN ON SOUTHERN FLANK OF CONVECTIVE CLUSTER.  THIS IS WHERE LOW-LEVEL HODOGRAPHS ARE ENHANCED BENEATH SOUTHERLY LOW-LEVEL JET AXIS...WHICH EXTENDS OFF THE WESTERN GULF OF MEXICO THROUGH THE WESTERN HALF OF LOUISIANA.  AS UPSTREAM HIGH LEVEL JET STREAK LIFTS OUT OF THE LOWER RIO GRANDE VALLEY THIS EVENING...30 TO 35 KT LOW-LEVEL JET IS PROGGED TO INTENSIFY TO AROUND 50 KT...AND LIFT NORTHWARD JUST EAST OF DEEPENING SURFACE LOW ALONG RED RIVER WEST OF TEXARKANA.  THIS MAY SUPPORT INCREASING RISK OF STRONG TORNADOES NORTH NORTHEAST OF ALEXANDRIA LA INTO AREAS NEAR/NORTHWEST OF VICKSBURG MS BY AROUND 02-03Z.

   

OTHERWISE...NEW SUPERCELLS LIKELY WILL CONTINUE TO FORM ALONG LOW-LEVEL JET AXIS SOUTHWARD ACROSS CENTRAL/SOUTHWEST LOUISIANA.

Mesoscale Discussion #2449


CONCERNING...TORNADO WATCH 888...890...

   

VALID 240314Z - 240515Z

   

CONTINUE WWS.

   

LOW-LEVEL CONFLUENT ZONE ALONG/JUST EAST OF SOUTHERLY LOW-LEVEL JET STRENGTHENING TO NEAR 50 KT LATE THIS EVENING REMAINS FOCUS FOR INTENSE CONVECTIVE DEVELOPMENT...INCLUDING ISOLATED SUPERCELLS. THIS BAND EXTENDS FROM NEAR ALEXANDRIA LA THROUGH THE VICINITY OF VICKSBURG MS INTO AREAS SOUTH OF GREENWOOD...WHERE BOUNDARY LAYER DEW POINTS NEAR 70F ARE CONTRIBUTING TO NARROW TONGUE OF MEAN MIXED LAYER CAPE UP TO AROUND 1000 J/KG.  GIVEN MOIST AND BUOYANT BOUNDARY LAYER...STRONG LOW-LEVEL SHEAR PROFILES AND STRENGTHENING FLOW ALOFT WILL CONTINUE TO PROVIDE FAVORABLE ENVIRONMENT FOR TORNADIC SUPERCELLS INTO THE OVERNIGHT HOURS.