Post by tigergirl on Sept 13, 2007 6:30:36 GMT -6
| MESOSCALE DISCUSSION 1964 NWS STORM PREDICTION CENTER NORMAN OK 0713 AM CDT THU SEP 13 2007 AREAS AFFECTED...PORTIONS SRN LA. CONCERNING...TORNADO WATCH 669... VALID 131213Z - 131415Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 669 CONTINUES. SUPERCELL/TORNADO POTENTIAL WITH HUMBERTO IS FCST TO SHIFT GENERALLY EWD ACROSS SRN LA THROUGH 17Z...REMAINING MOSTLY BETWEEN I-10 AREA AND COASTLINE IN CLOSEST PROXIMITY TO POTENTIAL FOR SFC-BASED BUOYANCY. TO REFLECT THIS TREND...NEW OR REPLACEMENT WW MAY BE REQUIRED BEFORE SCHEDULED 15Z EXPIRATION OF WW 669. THREAT SHOULD REMAIN MOST CONCENTRATED IN AND NEAR PRIMARY OUTER BAND THAT WAS LOCATED FROM ACADIA/WRN LAFAYETTE/VERMILION PARISHES SSEWD OVER GULF AS OF 1145Z. SEVERAL MINI-SUPERCELLS WITH SMALL BUT PRONOUNCED LOW LEVEL HORIZONTAL SHEAR COUPLETS HAVE BEEN OBSERVED DURING LAST SEVERAL HOURS WITH THIS BAND AND WITH RELATIVELY DISCRETE CELLS JUST TO ITS E. IN ADDITION...INNER BANDING STRUCTURES ARE BECOMING MORE PRONOUNCED ACROSS ERN PORTIONS CAMERON/JEFF DAVIS PARISHES ATTM...IN ENVIRONMENT OF STG LOW LEVEL SHEAR THAT ALSO WILL FAVOR MESOCYCLONE DEVELOPMENT ESPECIALLY FOR ANY RELATIVELY DISTINCT OR DISCRETE CELLS. PRIND FAVORABLE LOW LEVEL SHEAR PROFILES EARLIER SAMPLED BY LCH VWP -- AND NOW INDICATED E OF THERE TOWARD LFT -- WILL SPREAD EWD AND NEWD ACROSS MORE OF SRN/CENTRAL LA. NRN/INLAND EXTENT OF NEAR-TERM SUPERCELL/TORNADO RISK...HOWEVER...SHOULD CONTINUE TO BE DEFINED LOOSELY BY EXPANSIVE PRECIP SHIELD AND LOW LEVEL FRONTAL REMNANT OVER CENTRAL LA...WHICH WILL RESTRICT DESTABILIZATION. ..EDWARDS.. 09/13/2007 |
