2014

Mesoscale Discussion #0435


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 100 CONTINUES.


SUMMARY...NEAR-TERM RISK FOR A SIGNIFICANT TORNADO WEST/NORTHWEST OF LITTLE ROCK IS HIGH.


DISCUSSION...A DISCRETE SUPERCELL STORM HAS DEVELOPED A STRONG/TIGHT LOW-LEVEL CIRCULATION WEST OF LITTLE ROCK AND MAY DEVIATE TO THE RIGHT OF ITS MOTION. SUFFICIENT BUOYANCY RESIDES NORTH OF A WARM FRONT WHERE 0-1-KM SRH SAMPLED BY THE LZK VWP IS AROUND 450 M2/S2 FOR A SIGNIFICANT TORNADO THREAT IN THE SHORT TERM.

Mesoscale Discussion #0459


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 108 CONTINUES.


SUMMARY...DANGEROUS TORNADO OUTBREAK UNDERWAY WITH MULTIPLE SUPERCELLS CAPABLE OF PRODUCING LONG TRACK...STRONG/VIOLENT TORNADOES NEXT FEW HOURS.


DISCUSSION...MULTIPLE DISCRETE AND CLUSTER SUPERCELLS ARE MOVING NEWD FROM CENTRAL MS INTO NW AL. RADAR AND SPOTTER REPORTS HAVE CONFIRMED A DAMAGING TORNADO NEAR TUPELO MS IN THE PAST HOUR...WHILE OTHER MORE DISCRETE STORMS HAVE FORMED FARTHER TO S INTO CENTRAL MS. ALIGNMENT OF THE STORM INITIATION AND SPACING OF THE STORMS IN CENTRAL MS SUGGEST THAT THESE STORMS WILL REMAIN DISCRETE FOR SEVERAL HOURS...SUPPORTING THE POTENTIAL FOR LONG-TRACK TORNADOES. ADDITIONALLY...LOCAL VWP/S HAVE SHOWN THE EXPECTED STRENGTHENING OF WIND PROFILES AND SOME BACKING OF LOW-LEVEL FLOW ASSOCIATED WITH SURFACE PRESSURE FALLS...WHICH IS BOOSTING EFFECTIVE SRH TO NEAR 300 M2/S2.  STRONG TO VIOLENT TORNADO DAMAGE WILL BE POSSIBLE WITH THE MOST INTENSE SUPERCELLS THE NEXT FEW HOURS

Mesoscale Discussion #0566


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 142 CONTINUES.


SUMMARY...SIGNIFICANT TORNADO THREAT WITH LEAD SUPERCELLS ALONG WARM FRONT IN SE NEB...WITH LONG-TRACK/DAMAGING TORNADOES POSSIBLE THE NEXT FEW HOURS.


DISCUSSION...THE LEAD SUPERCELL NOW ENTERING NW FILLMORE AND YORK COUNTIES IN SE NEB WILL LIKELY TRACK ALONG THE SURFACE WARM FRONT FOR THE NEXT FEW HOURS.  SURFACE OBSERVATIONS SHOW THE BOUNDARY LIFTING NWD IN SW IA/SE NEB...SUCH THAT THE SUPERCELL WILL BEGIN TO ENCOUNTER A MORE FAVORABLE TORNADO ENVIRONMENT ALONG AND IMMEDIATELY N OF THE WARM FRONT WHERE THE LOW LEVELS CONTINUE TO WARM/MOISTEN. THE ORIENTATION OF THE WARM FRONT WILL REMAIN LARGELY PARALLEL TO THE STORM MOTION...WITH THE SUPERCELL EXPECTED TO REMAIN WITHIN A FAVORABLE ZONE OF ENHANCED LOW-LEVEL SHEAR AND MOISTURE ALONG THE BOUNDARY FOR SEVERAL HOURS.  THIS WILL SUPPORT AN ENHANCED RISK OF LONG-TRACK/DAMAGING TORNADOES FOR THE NEXT FEW HOURS...POTENTIALLY REACHING LINCOLN BY 23Z AND OMAHA/AREAS IMMEDIATELY TO THE S AROUND 00Z. THE MAIN UNCERTAINTY WILL BE THE DEGREE OF STORM INTERACTIONS/INTERFERENCE WITH NEW STORM FORMATION AHEAD OF THE INITIAL SUPERCELL...AND OTHER STORMS NOT FAR BEHIND.

Mesoscale Discussion #0570


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 142 CONTINUES.


SUMMARY...SIGNIFICANT TORNADO THREAT CONTINUES FROM NEAR LINCOLN NEB TOWARD OMAHA INTO SWRN IA. AN ADDITIONAL TORNADO THREAT WILL BE PRESENT WITH SUPERCELLS DEVELOPING TO THE WEST OF THE LONG-LIVED TORNADIC STORM.


DISCUSSION...AT 2315Z...A LONG-LIVED TORNADIC SUPERCELL WAS IN NRN LANCASTER COUNTY NEBRASKA JUST NORTH OF LINCOLN. THIS STORM HAS EVOLVED AN HP-SUPERCELL STRUCTURE WITH SUBSTANTIAL CONVECTION DEVELOPING ON ITS REAR FLANK. THIS STORM EVOLUTION CASTS SOME UNCERTAINTY REGARDING THE MAGNITUDE OF THE TORNADO THREAT AS IT MOVES ENEWD...BUT IT REMAINS IN A VERY FAVORABLE ENVIRONMENT AS IT MOVES ALONG A WARM FRONT WHICH HAS BECOME NEARLY STATIONARY TO THE SOUTH OF OMAHA. MLCAPE OF 2000-3000 J/KG COMBINED WITH O-1 KM SRH OF 300-400 M2/S2 WILL CONTINUE TO SUPPORT A THREAT OF DAMAGING TORNADOES WITH THIS CELL AS IT APPROACHES OMAHA BY 00Z AND MOVES INTO SWRN IA THEREAFTER. 


FURTHER TO THE WEST...ADDITIONAL SUPERCELLS HAVE DEVELOPED ALONG THE NEARLY STATIONARY FRONT AND WILL RIDE ALONG THE BOUNDARY IN A SIMILAR FASHION...POSING AN ADDITIONAL TORNADO THREAT NEAR LINCOLN BY 00Z. VERY LARGE HAIL AND SIGNIFICANT WIND DAMAGE WILL ALSO BE POSSIBLE WITH THESE CELLS IN ADDITION TO THE TORNADO RISK.

Mesoscale Discussion #1020


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 303 CONTINUES.


SUMMARY...VOLATILE TORNADIC ENVIRONMENT FOR THE DISCRETE SUPERCELL AS IT MOVES DOWNSTREAM TOWARDS THE MO RIVER.


DISCUSSION...THE 19Z OAX RAOB DISPLAYED AN EXTREMELY UNSTABLE AIRMASS WITH MLCAPE 4200 J PER KG WITH A VERY LARGE LOOPING HODOGRAPH SUPPORTING 500 J PER KG EFFECTIVE SRH.  RADAR DATA HAS SHOWN THE STANTON COUNTY TORNADIC SUPERCELL CYCLE WITH PEAK LOW-LEVEL ROTATIONAL VELOCITIES /70-80 KT/ SUPPORTING HIGH PROBABILITIES FOR AN INTENSE TORNADO.  TEMPS CONTINUE TO WARM INTO THE LOWER TO MIDDLE 80S DOWNSTREAM OVER WRN IA WITHIN A VERY MOIST BOUNDARY LAYER.  CURRENT THINKING IS LONG TRACK INTENSE TORNADOES/RELATIVELY HIGH CHANCE FOR AN EF3+ INTENSITY TORNADO/ WILL BE POSSIBLE WITH THIS STORM AS IT MOVES TOWARDS THE MO RIVER VALLEY AND INTO WRN IA OVER THE NEXT 1-2 HRS.

Mesoscale Discussion #1048


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 315 CONTINUES.


SUMMARY...VERY STRONG LOW-LEVEL ROTATIONAL VELOCITIES LIKELY INDICATIVE OF A VIOLENT TORNADO. THE NEAR-STORM ENVIRONMENT REMAINS VERY SUPPORTIVE FOR INTENSE TORNADOES FOR THE NEXT HOUR OR MORE.


DISCUSSION...KOAX RADAR IMAGERY SHOWS PEAK 0.5 DEG ROTATIONAL VELOCITIES 90+ KT SUPPORTING A HIGH PROBABILITY /60 PERCENT OR GREATER/ FOR A VIOLENT TORNADO BASED ON RADAR ALONE.  THE 00Z OMA RAOB SHOWED A AN EXTREMELY UNSTABLE AIRMASS AND LOW-LEVEL SHEAR IS BEGINNING TO INCREASE PER KOAX VWP DATA.INPUTTING THE CEDAR COUNTY TORNADIC SUPERCELL MOTION YIELDS OVER 300 M2/S2 0-3 KM SRH. EXPECTING A CONTINUED THREAT FOR INTENSE TORNADOES /EF3+/ FOR THE NEXT HOUR OR SO.

Mesoscale Discussion #0799


PROBABILITY OF WATCH ISSUANCE...95 PERCENT


SUMMARY...SIGNIFICANT TORNADO AND WIND DAMAGE THREAT IS INCREASING ACROSS PARTS OF FAR ERN NEB INTO SW IA/NRN MO NEAR THE WARM FRONT. THIS THREAT WILL SHIFT E/SE INTO SE IA/NE MO LATER THIS EVENING. A NEW TORNADO WATCH WILL BE NEEDED IN THE NEXT 1-2 HOURS...PRIOR TO THAT...A LOCAL EXTENSION TO THE EAST FOR TORNADO WATCH 207 IS LIKELY.


DISCUSSION...A VERY FAVORABLE ENVIRONMENT FOR TORNADOES AND EXTREME WINDS IS EVOLVING ACROSS PARTS OF THE MID-MO VALLEY IN THE VICINITY OF THE WARM FRONT. THIS FRONT EXTENDS E/SE ACROSS CENTRAL NEB INTO SW IA AND N-CENTRAL MO. SFC DEWPOINTS IN THE MID 60S TO LOW 70S AND STRONG SFC HEATING HAVE RESULTED IN SBCAPE VALUES APPROACHING 4500 J/KG IN THE WARM SECTOR. SUPERCELLS HAVE DEVELOPED ON/NEAR THE WARM FRONT NEAR THE MO/IA BORDER AND WILL CONTINUE TO POSE A THREAT FOR STRONG WINDS...LARGE HAIL AND TORNADOES. FURTHER UPSTREAM...A BOWING SEGMENT NEAR OMAHA SHOULD THRIVE IN THIS ENVIRONMENT AND CONTINUE ON A SEWD TRAJECTORY ALONG THE WARM FRONT/INSTABILITY GRADIENT. SIGNIFICANT WINDS IN EXCESS OF 65KT WILL CONTINUE TO BE POSSIBLE WITH THIS BOWING SEGMENT...IN ADDITION TO LARGE HAIL. 


AS THE LOW LEVEL JET INCREASES THIS EVENING...CONDITIONS WILL BECOME MORE FAVORABLE FOR TORNADO DEVELOPMENT AS LOW LEVEL HODOGRAPHS BECOME MAXIMIZED IN THE VICINITY OF THE BOUNDARY. ANY SUPERCELLS THAT CAN REMAIN SEMI-DISCRETE WILL POSE A STRONG/SIGNIFICANT TORNADO THREAT. EVENTUALLY...STORMS ARE EXPECTED TO GROW UPSCALE INTO A FORWARD PROPAGATING BOWING QLCS ACROSS SE IA/NE MO WITH THE POTENTIAL FOR A WIDE SWATH OF EXTREME/DAMAGING WINDS ACROSS THE MCD AREA. 


TORNADO WATCH 207 HAS BEEN EXTENDED EWD FOR THE TIME BEING ACROSS PARTS OF SRN IA/NRN MO. A NEW WATCH WILL LIKELY BE ISSUED IN THE NEXT HOUR OR TWO.

Mesoscale Discussion #0800


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 207...209...CONTINUES.


SUMMARY...ONGOING TSTMS ARE EXPECTED TO PERSIST WITH A CONTINUED THREAT OF VERY LARGE HAIL...DAMAGING WINDS IN EXCESS OF 65 KT...AND TORNADOES. A FEW TORNADOES COULD BE STRONG...PARTICULARLY ACROSS S-CNTRL NEB.


DISCUSSION...MESOANALYSIS AND SURFACE OBSERVATIONS REVEALS AN ENVIRONMENT VERY FAVORABLE FOR SUPERCELLS OVER CNTRL NEB. KLNX RADAR IMAGERY SHOWS AN OUTFLOW BOUNDARY EXTENDING S OF THE ONGOING ACTIVITY IN HOOKER AND THOMAS COUNTIES...LIMITING THE TORNADO THREAT WITH THOSE STORMS. LARGE HAIL AND DAMAGING WINDS ARE STILL POSSIBLE.


FARTHER E /CNTRL NEB/...SUPERCELL NEAR ODX CONTINUES TO SHOW STRONG LOW-LEVEL ROTATION AND WDSS-II MESH NEAR 3 INCHES. THIS SUPERCELL IS MOVING INTO A VERY FAVORABLE ENVIRONMENT CHARACTERIZED BY DEEP LAYER SHEAR OF 60 KT...20 KT BACKED SURFACE WINDS...0-3 KM SRH OVER 600 M2/S2...DEWPOINTS IN THE MID 60S...AND MID-LEVEL LAPSE RATES NEAR 7 DEG C PER KM. EFFECTIVE-LAYER STP IS 12. ALL OF THESE FACTORS INDICATE AN ENVIRONMENT CAPABLE OF SUPPORTING A STRONG TORNADO. IT APPEARS THE ONGOING SUPERCELL WILL HAVE A HIGH PROBABILITY OF PRODUCING A STRONG TORNADO AS LONG AS THE IT CAN REMAIN SEMI-DISCRETE AND AVOID NEGATIVE STORM INTERACTIONS. 


ANY ADDITIONAL DEVELOPMENT S OF THE ONGOING STORMS /SUCH AS THE RECENT UPDRAFT IN CUSTER COUNTY/ IN THIS FAVORABLE ENVIRONMENT WOULD LIKELY BE SUPERCELLULAR AS LONG AS IT CAN REMAIN DISCRETE.