000 WTPZ42 KNHC 301518 TCDEP2 TROPICAL STORM BARBARA DISCUSSION NUMBER 4...CORRECTED NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP022007 800 AM PDT WED MAY 30 2007 ...CORRECTED DEPRESSION TO TROPICAL CYCLONE IN 2ND PARAGRAPH THE SATELLITE PRESENTATION OF THE TROPICAL CYCLONE HAS BECOME A LITTLE STRONGER...WITH A RAGGED BAND IN THE SOUTHEASTERN QUADRANT OF THE CIRCULATION. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE 35 AND 30 KT...RESPECTIVELY...WHILE THE CIMSS ADT GIVES 41 KT. ON THIS BASIS...THE DEPRESSION IS UPGRADED TO A 35 KT TROPICAL STORM. ONLY TWICE BEFORE...IN 1956 AND 1984...HAVE THERE BEEN TWO EASTERN NORTH PACIFIC NAMED STORMS IN MAY. THE TROPICAL CYCLONE REMAINS NEARLY STATIONARY. WATER VAPOR IMAGERY INDICATES THAT A LARGE MID- TO UPPER-LEVEL TROUGH IS DEVELOPING OVER MEXICO AND THE WESTERN GULF OF MEXICO...WITH A LARGE MID/UPPER- LEVEL RIDGE OVER THE PACIFIC WEST OF THE TROUGH. THE IMAGERY ALSO SHOWS MID-LEVEL NORTHERLIES ABOUT TO IMPINGE ON THE CIRCULATION. IN THE SHORT TERM...THIS SHOULD RESULT IN A SOUTHWARD DRIFT AWAY FROM THE MEXICAN COASTLINE...AND MODEL GUIDANCE IS IN GOOD AGREEMENT ON THIS FOR THE FIRST DAY OR TWO OF THE FORECAST. AFTER THAT...HOWEVER...THERE IS A GREAT DEAL OF UNCERTAINTY AS TO WHETHER BARBARA WILL BE STEERED NORTHEASTWARD AHEAD OF THE GULF TROUGH OR SLIDE WESTWARD AS THE TROUGH LIFTS OUT AND RIDGING BUILDS BEHIND IT. IN THE FORMER CAMP ARE THE GFS AND ECMWF...WHILE A MORE WESTWARD TRACK IS INDICATED BY THE GFDL...UKMET...AND NOGAPS. INTERESTINGLY...THE ECMWF ENSEMBLES ARE PRETTY MUCH SPLIT BETWEEN THESE TWO OPTIONS. THE OFFICIAL FORECAST...ADMITTEDLY LOW CONFIDENCE...CONTINUES TO FAVOR THE MORE WESTWARD SCENARIO. THE INTENSITY FORECAST IS DIFFICULT AS WELL. THE MID-LEVEL NORTHERLIES APPROACHING THE CYCLONE WILL ADVECT SOME DRY AIR INTO THE CIRCULATION AND INCREASE THE VERTICAL SHEAR. CONSEQUENTLY... BARBARA COULD STRUGGLE IN THE SHORT RUN. OVERALL...HOWEVER... CONDITIONS APPEAR FAVORABLE FOR DEVELOPMENT...WITH VERY WARM WATERS AND GOOD UPPER OUTFLOW. THE SHIPS AND GFDL MODELS CONTINUE TO FORECAST BARBARA TO REACH HURRICANE STRENGTH IN 48-72 HOURS. THE OFFICIAL FORECAST ENDS UP IN ABOUT THE SAME PLACE BUT WITH LESS DEVELOPMENT INITIALLY. FORECAST POSITIONS AND MAX WINDS INITIAL 30/1500Z 14.2N 97.3W 35 KT 12HR VT 31/0000Z 13.9N 97.2W 35 KT 24HR VT 31/1200Z 13.4N 97.1W 40 KT 36HR VT 01/0000Z 13.0N 97.0W 50 KT 48HR VT 01/1200Z 13.0N 96.8W 60 KT 72HR VT 02/1200Z 13.5N 96.5W 70 KT 96HR VT 03/1200Z 15.0N 97.5W 75 KT 120HR VT 04/1200Z 16.5N 100.0W 70 KT $$ FORECASTER FRANKLIN