000 WTPZ42 KNHC 310836 TCDEP2 TROPICAL STORM BARBARA DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP022007 200 AM PDT THU MAY 31 2007 BARBARA CONTINUES TO GENERATE A CLUSTER OF STRONG CONVECTION WITH TOPS COLDER THAN -80C NEAR THE CENTER...ALTHOUGH THERE IS NO RECENT MICROWAVE IMAGERY TO SHOW THE EXACT CONVECTIVE STRUCTURE. SATELLITE INTENSITY ESTIMATES ARE 45 KT FROM TAFB AND 35 KT FROM SAB. BASED ON THIS...THE INITIAL INTENSITY REMAINS 40 KT. MICROWAVE IMAGES FROM 00Z-03Z SUGGEST THE CENTER WAS A LITTLE TO THE NORTHEAST OF THE PREVIOUS ADVISORY POSITION...SO THE INITIAL POSITION FOR THIS ADVISORY IS NUDGED THAT WAY. THIS YIELDS A HIGHLY UNCERTAIN INITIAL MOTION OF 130/2. BARBARA IS EMBEDDED IN THE INTERTROPICAL CONVERGENCE ZONE EXTENDING FROM A DISTURBANCE OVER THE NORTHWESTERN CARIBBEAN SEA ACROSS CENTRAL AMERICA INTO THE PACIFIC...AND A LARGE MID/UPPER-LEVEL TROUGH IS NORTH OF THE CYCLONE OVER THE GULF OF MEXICO. THE LARGE-SCALE MODELS FORECAST THE GULF TROUGH TO AMPLIFY WITH A SURFACE LOW FORMING DURING THE NEXT 48 HR...THEN MOVING NORTHEASTWARD AWAY FROM BARBARA AFTER THAT TIME. THE GFDL... UKMET...ECMWF...GFDN...AND CANADIAN MODELS ALL BRING BARBARA TO THE COAST OF MEXICO OR GUATEMALA IN 72 HR OR LESS...WHILE THE GFS CALLS FOR THE STORM TO PERFORM A LOOP AND MOVE LITTLE DURING THE NEXT 5 DAYS. BASED ON THE SLIGHTLY FASTER MOTION IN MOST OF THE GUIDANCE AND THE ADJUSTED POSITION... THE NEW FORECAST TRACK IS ADJUSTED NORTH OF THE PREVIOUS TRACK. HOWEVER...IT SLOWER THAN THE MAJORITY OF THE GUIDANCE AND BRINGS THE CENTER NEAR THE COAST OF MEXICO IN 96 HR. AS THE GULF SYSTEM MOVED AWAY...PRESSURES SHOULD RISE NORTH OF BARBARA AND TURN THE CYCLONE MORE WESTWARD...ASSUMING THAT IT HAS NOT MOVED ONSHORE BY THAT TIME. THIS TRACK FORECAST REMAINS LOW CONFIDENCE. BARBARA IS IN A COMPLICATED UPPER-LEVEL WIND PATTERN...WITH HIGH-LEVEL FLOW FROM THE SOUTHEAST BEING UNDERCUT BY NORTHERLY FLOW AT A SOMEWHAT LOWER LEVEL. OVERALL...THE STORM HAS POOR OUTFLOW AND SEEMS TO BE LOSING INFLOW TO THE CARIBBEAN SYSTEM. THESE FACTORS HAVE LIKELY SLOWED THE INTENSIFICATION. THE LARGE-SCALE MODELS SUGGEST THAT THE UPPER-LEVEL WINDS WILL GRADUALLY BECOME MORE FAVORABLE DURING THE NEXT 48 HR...WITH THE GFDL CALLING FOR BARBARA TO BECOME A HURRICANE BY THAT TIME. THE SHIPS MODEL FORECAST SLOWER INTENSIFICATION...AND THE INTENSITY FORECAST IS A COMPROMISE BETWEEN THE TWO CALLING FOR GRADUAL INTENSIFICATION. THE FORECAST NOW CALLS FOR SOME WEAKENING AFTER 96 HR DUE TO THE EXPECTED CLOSE PROXIMITY OF THE CENTER TO THE COAST. HEAVY RAINS NOW OCCURRING OVER PORTIONS OF CENTRAL AMERICA ARE NOT DIRECTLY ASSOCIATED WITH BARBARA. INSTEAD...THIS ACTIVITY IS DUE TO THE DEVELOPING DISTURBANCE OVER THE NORTHWESTERN CARIBBEAN SEA AND THE RESULTING NORTHWARD PERTURBATION OF THE ITCZ. FORECAST POSITIONS AND MAX WINDS INITIAL 31/0900Z 13.2N 96.7W 40 KT 12HR VT 31/1800Z 12.9N 96.6W 45 KT 24HR VT 01/0600Z 12.8N 96.5W 50 KT 36HR VT 01/1800Z 13.3N 96.3W 55 KT 48HR VT 02/0600Z 13.8N 96.1W 60 KT 72HR VT 03/0600Z 14.5N 96.0W 65 KT 96HR VT 04/0600Z 15.5N 96.5W 70 KT 120HR VT 05/0600Z 16.0N 98.0W 65 KT $$ FORECASTER BEVEN