000 WTPZ42 KNHC 311456 TCDEP2 TROPICAL STORM BARBARA DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP022007 800 AM PDT THU MAY 31 2007 BARBARA APPEARS TO HAVE LOST ORGANIZATION OVERNIGHT. THE FIRST FEW VISIBLE IMAGES...AND QUIKSCAT AMBIGUITIES JUST RECEIVED...SUGGEST THAT ITS SURFACE CIRCULATION COULD BE LOSING DEFINITION WITHIN A LARGER-SCALE TROUGH...A NORTHWARD EXTENSION OF THE ITCZ. BARBARA CONTINUES TO GENERATE A CLUSTER OF STRONG CONVECTION WITH TOPS COLDER THAN -80C NEAR THE CENTER...ALTHOUGH WITH LITTLE STRUCTURE OR BANDING. DVORAK T NUMBERS AND THE QUIKSCAT DATA INDICATE THAT BARBARA HAS WEAKENED AND THE INITIAL INTENSITY IS LOWERED TO 35 KT. QUIKSCAT AMBIGUITIES INDICATE THAT BARBARA IS MOVING SLOWLY EASTWARD. THE TRACK FORECAST TURNS ON HOW MUCH INTERACTION OCCURS BETWEEN BARBARA AND THE MID- TO UPPER-LEVEL TROUGH CURRENTLY DIGGING SOUTHWARD OVER THE WESTERN GULF OF MEXICO. MODEL GUIDANCE CONTINUES TO BE HIGHLY DIVERGENT ON THIS QUESTION. THE ECMWF REMAINS THE EASTERN OUTLIER... TAKING BARBARA INTO GUATEMALA OVER THE NEXT 36 HOURS. THE GFS DRIFTS BARBARA SLOWLY WESTWARD...WHILE THE NOGAPS...UKMET...AND GFDL INDICATE A SLOW NORTHWARD OR NORTHEASTWARD MOTION THAT BRINGS THE CYCLONE OVER OR NEAR THE MEXICAN COAST IN ABOUT 72 HOURS. LATER IN THE FORECAST PERIOD AS THE GULF TROUGH MOVES OUT...RISING HEIGHTS OVER MEXICO COULD TURN THE CYCLONE WESTWARD. THE OFFICIAL FORECAST IS CLOSE TO THE PREVIOUS ADVISORY AND IN BEST AGREEMENT WITH THE NOGAPS AND UKMET SOLUTIONS. THE ENVIRONMENT OF BARBARA IS LOOKING LESS FAVORABLE FOR DEVELOPMENT. WATER VAPOR IMAGERY NOW SHOWS SOME EASTERLY SHEAR UNDERCUTTING THE OUTFLOW...WHILE QUIKSCAT AND VISIBLE SATELLITE IMAGERY IS SHOWING LIMITED LOW-LEVEL INFLOW. IT IS POSSIBLE THAT BARBARA WILL DISSIPATE WITHIN THE ITCZ LATER TODAY. IF IT SURVIVES...HOWEVER...MODEL GUIDANCE SUGGESTS THAT THE SHEAR WILL GRADUALLY LESSEN OVER THE NEXT COUPLE OF DAYS. THIS COULD ALLOW SOME REDEVELOPMENT... ALTHOUGH IT NOW SEEMS LESS LIKELY THAT BARBARA WILL BECOME A HURRICANE. FORECAST POSITIONS AND MAX WINDS INITIAL 31/1500Z 13.1N 95.8W 35 KT 12HR VT 01/0000Z 13.4N 96.3W 35 KT 24HR VT 01/1200Z 13.7N 96.1W 40 KT 36HR VT 02/0000Z 14.1N 95.9W 45 KT 48HR VT 02/1200Z 14.8N 95.9W 50 KT 72HR VT 03/1200Z 15.5N 96.0W 55 KT 96HR VT 04/1200Z 16.0N 97.0W 45 KT...INLAND 120HR VT 05/1200Z 16.5N 98.0W 30 KT...INLAND $$ FORECASTER FRANKLIN