MESOSCALE DISCUSSION 0747
NWS STORM PREDICTION CENTER NORMAN OK
0926 PM CDT SUN MAY 04 2003
AREAS AFFECTED...SERN MO...NERN AR...NRN MS...WRN TN...WRN
KY...EXTREME SRN IL
CONCERNING...TORNADO WATCH 239...
VALID 050226Z - 050430Z
THREAT FOR STRONG TORNADOES CONTINUES WITHIN WW 239...AND IS
ESPECIALLY HIGH FROM WRN TN INTO WRN KY.
LATEST SURFACE ANALYSIS SHOWS PRESSURE RISE/FALL COUPLET FROM SERN
MO INTO WRN KY/TN. THE FALLS ARE CENTERED FROM WRN TN INTO WRN
KY...WITH VALUES UP TO 2 MB IN THE LAST HOUR ALONE...INDICATIVE OF
NWD RETURN OF MOIST UNSTABLE AIR SOUTH OF RETREATING WARM FRONT.
OBJECTIVE ANALYSIS SHOWS MODERATE INSTABILITY WITH MLCAPES UP TO
2500 J/KG.
PAH AND NQA VWPS SHOW TREMENDOUS LOW LEVEL HELICITY...WITH 0-3 KM
SRH VALUES OF 500-800 M2/S2. GIVEN HIGH LEVELS OF BOUNDARY LAYER RH
AND EXTREME SHEAR VALUES...ANY STORMS IN THIS ENVIRONMENT WILL HAVE
A HIGH PROBABILITY OF PRODUCING STRONG TORNADOES. HIGHEST THREAT
AREA IS OVER WRN TN AND KY...WHERE DEWPOINTS HAVE RISEN INTO THE
UPPER 60S F AND PRESSURES ARE FALLING THE FASTEST. THREAT COULD
EXTEND FURTHER N INTO SRN IL AND INDIANA LATER THIS EVENING AS WARM
FRONT RETREATS. A WW MAY BE REQUIRED N OF CURRENT WATCH BOX.
..JEWELL.. 05/05/2003
