What is Storm Anticipation (SA)? Using the SPC mesoanalysis fields to anticipate what is likely to occur.

Transcription

1 Fisher 2018

2 What is Storm Anticipation (SA)? Using the SPC mesoanalysis fields to anticipate what is likely to occur. Why do I need it? I have read the SPC outlooks and discussions (part of SA) I have read the LOT outlooks and discussions (part of SA) SPC has issued a watch Our weather operation is up and running Life is good, I can sit back now and react to the weather. NO! NO! NO! NO! NO! You never want to react to the weather. You want to be proactive, thinking about storm anticipation, thinking about what is most likely to occur. Making the correct decisions based on science.

3 This table is the reason for SA. Sixty+ years of weather reality. SA tells you the most likely reality of the day.

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9 ...SUMMARY... WIDESPREAD DAMAGING WIND GUSTS WITH SOME GREATER THAN 70 MILES PER HOUR ALONG WITH TORNADOES AND ISOLATED LARGE HAIL ARE EXPECTED THIS AFTERNOON AND EVENING FROM NORTHEAST IOWA INTO EXTREME SOUTHERN WISCONSIN...NORTHERN ILLINOIS...SOUTHWEST LOWER MICHIGAN...NORTHERN TO CENTRAL INDIANA AND PARTS OF WESTERN OHIO. A WIND DAMAGE THREAT MAY ALSO AFFECT THE UPPER OHIO VALLEY AND CENTRAL AND SOUTHERN APPALACHIANS....UPPER MS VALLEY/MIDWEST/OH VALLEY TO APPALACHIANS... WATER VAPOR IMAGERY FEATURES AN EAST/SOUTHEASTWARD-MOVING LOW-AMPLITUDE SHORTWAVE TROUGH/RELATED SPEED MAX OVER SOUTHERN MANITOBA/NORTHERN ND AT LATE MORNING...WITH THIS IMPULSE EXPECTED TO REACH THE UPPER GREAT LAKES THIS EVENING. AHEAD OF THIS SYSTEM...12Z UPPER-AIR ANALYSIS FEATURES A SEASONALLY VERY STRONG BELT OF 50+ KT WEST-NORTHWESTERLY MID-LEVEL WINDS OVER THE NORTH-CENTRAL/NORTHEAST CONUS...AS FAR SOUTH AS THE MIDDLE MO VALLEY AND OH RIVER/CENTRAL APPALACHIANS. SCATTERED SHOWERS/NON-SEVERE THUNDERSTORMS CONTINUE LATE THIS MORNING ALONG AND NORTHEAST OF WARM FRONT THAT EXTENDS FROM SOUTHEAST IA INTO CENTRAL IL AND SOUTHERN INDIANA. WHILE THE CONTINUED PERSISTENCE OF THIS CONVECTION/RELATED CLOUD CASTS SOME UNCERTAINTY ON ITS EFFECTIVE SPATIAL LOCATION/TIMING...THE WARM FRONT WILL CONTINUE A GENERAL NORTH-NORTHEASTWARD ADVANCEMENT TODAY AS A SURFACE LOW CURRENTLY OVER EASTERN NEB DEVELOPS EASTWARD TOWARD EASTERN IA BY EARLY EVENING. MORNING UPPER-AIR DATA AND RECENT SURFACE ANALYSIS/TRENDS SUGGEST THAT AN INCREASINGLY MOIST AIR MASS /CHARACTERIZED BY AROUND 70F SURFACE DEWPOINTS AND 1.7+ INCH PRECIPITABLE WATER VALUES/ WILL DEVELOP NORTHEASTWARD ACROSS THE REGION IN TANDEM WITH THE PROGRESSION OF THE WARM FRONT. WHILE MID-LEVEL LAPSE RATES WERE NOT PARTICULARLY STEEP IN MOST 12Z REGIONAL OBSERVATIONS...AN EASTWARD-EXPANDING ELEVATED MIXED LAYER /OMAHA 12Z OBSERVED SOUNDING/ WILL CONTRIBUTE TO STRONG BUOYANCY /3000+ J PER KG MLCAPE/ BY LATE AFTERNOON PARTICULARLY FROM EASTERN IA INTO IL AND CENTRAL/SOUTHERN INDIANA. CONSIDERABLE INSTABILITY AND SIGNIFICANTLY STRONG VERTICAL SHEAR /50-70 KT EFFECTIVE/ NEAR AND SOUTH OF THE OUTFLOW/DIFFERENTIAL HEATING-INFLUENCED WARM FRONT WILL SUPPORT INITIAL SUPERCELLS CAPABLE OF LARGE HAIL AND TORNADOES...A FEW OF WHICH COULD BE SIGNIFICANT /EF2+/. THIS INITIAL SUPERCELLULAR DEVELOPMENT CURRENTLY APPEARS MOST PROBABLE ACROSS NORTHERN IL/FAR EASTERN IA AND POSSIBLY ADJACENT EXTREME SOUTHERN WI BY MID/LATE AFTERNOON NEAR/JUST AHEAD OF THE SURFACE LOW AND NEARBY WARM FRONT. THESE STORMS SHOULD EVENTUALLY GROW UPSCALE INTO A FAST-MOVING QUASI-LINEAR MCS...POTENTIALLY WITH A DERECHO-RELATED SIGNIFICANT SWATH OF WIND DAMAGE EVOLVING EAST-SOUTHEASTWARD THROUGH THE EVENING /AND POTENTIALLY CONTINUING INTO THE OVERNIGHT/. THE DAMAGING WIND POTENTIAL MAY REACH THE OH RIVER/CENTRAL APPALACHIANS LATE TONIGHT.

10 ...UPPER MS VALLEY EWD ACROSS THE OH VALLEY... RECENT SURFACE ANALYSIS PLACES THE SURFACE LOW OVER W-CNTRL IA WITH A WEAK INVERTED TROUGH EXTENDING NWD TO ANOTHER LOW NEAR THE ND/SD/MN BORDER INTERSECTION. WARM FRONT EXTENDS FROM THE W-CNTRL IA LOW ENEWD INTO FAR NE IA AND THEN SEWD ACROSS CNTRL IL TO NEAR CMI IN E-CNTRL IL. THIS BOUNDARY HAS BEEN REINFORCED BY DIFFERENTIAL HEATING WITH CLEAR SKIES AND TEMPERATURES IN 80S TO ITS SOUTH WHILE PARTLY TO MOSTLY CLOUDY AND TEMPERATURES IN THE MID 70S TO ITS NORTH. THIS BOUNDARY IS EXPECTED TO MOVE GRADUALLY NEWD OVER THE NEXT FEW HOURS AND TO ACT AS THE NRN DELIMITER OF THE MORE SUBSTANTIAL SVR RISK. 19Z SOUNDING FROM ILX SAMPLED 13 DEG C AT 700 MB AND THE RESULTING CAP SHOULD LIMIT CONVECTIVE POTENTIAL SOUTH AND WEST OF CNTRL IL WITH NO NEED TO EXPAND ANY SEVERE PROBABILITIES SWWD. 19Z SOUNDING FROM DVN SAMPLED FAIRLY STEEP MID-LEVEL LAPSE RATES BUT SIGNIFICANT WARMING AROUND 850 MB /ABOUT 5 DEG C SINCE 12Z/ HAS KEPT CONVECTIVE-INHIBITION IN PLACE. CONTINUED WARMING AND MOISTENING ARE ANTICIPATED HERE AS THE AIRMASS TO THE SW /CHARACTERIZED BY TEMPERATURES IN THE LOW 90S AND DEWPOINTS IN THE LOW 70S/ CONTINUES TO ADVECT NEWD. FORCING FOR ASCENT ASSOCIATED WITH THE APPROACHING SURFACE LOW COMBINED WITH THE ANTICIPATED AIRMASS MODIFICATION IS STILL EXPECTED TO RESULT IN CONVECTIVE INITIATION IN THE VICINITY OF CID/DVN. ONCE THIS OCCURS THE ENVIRONMENT WILL BE VERY SUPPORTIVE FOR INITIAL SUPERCELLS CAPABLE OF ALL HAZARDS /INCLUDING A TORNADO OR TWO/. QUICK UPSCALE GROWTH INTO A LINEAR MCS IS STILL ANTICIPATED WITH A DAMAGING WIND THREAT EXTENDING ACROSS MUCH OF THE OH VALLEY. THIS SCENARIO MATCHES PREVIOUS OUTLOOK THINKING WELL AND NO CHANGES WERE MADE TO THE OUTLOOK ACROSS THIS REGION.

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30 The results of my storm anticipation, what am I expecting as a most likely severe weather outbreak? Most concentrated severe storms near the warm front Long lasting supercells easily of 3 4 hours Large hail 2+ inches Supercells to produce multiple tornadoes Likely EF2 EF3 tornadoes Immediate Chicago area in the cool stable air, no tornado threat

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