WTPA44 PHFO 191450 TCDCP4 TROPICAL STORM GUILLERMO DISCUSSION NUMBER 30 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP102009 500 AM HST WED AUG 19 2009 GUILLERMO CONTINUES TO HAVE LIMITED DEEP CONVECTION TO THE NORTH OF AN EXPOSED LOW LEVEL CIRCULATION CENTER. LAST EVENING/S QUIKSCAT PASS...AS WELL AS AN 0738Z ASCAT PASS...SHOW THAT THE STRONGEST WINDS WITH GUILLERMO REMAIN CONFINED TO THE NORTHERN SEMICIRCLE. THESE WINDS ARE AT LEAST PARTLY DUE TO THE STRONG PRESSURE GRADIENT BETWEEN GUILLERMO AND A 1026 MB HIGH TO THE NORTHEAST. WE ARE MAINTAINING GUILLERMO AS A 35 KT TROPICAL STORM FOR THIS ADVISORY ISSUANCE BASED ON THE SCATTEROMETER DATA. THE INITIAL MOTION IS UNCHANGED FROM THE PREVIOUS ADVISORY...310/16. GUILLERMO IS CURRENTLY MOVING TOWARD A BREAK IN THE SUBTROPICAL RIDGE TO THE NORTHWEST OF THE CYCLONE. THE TRACK GUIDANCE IS ESSENTIALLY SPLIT INTO TWO CAMPS. ONE GROUP...INCLUDING NOGAPS... HWRF...AND UKMET...INDICATE RECURVATURE INTO THE MID-LATITUDE WESTERLIES AFTER ABOUT 24 HOURS. ON THE OTHER HAND...THE ECMWF... GFS...AND GFDL MAINTAIN A NORTHWEST MOTION LONGER. IN FACT...THE ECMWF IS STILL HANGING ON TO THE IDEA THAT GUILLERMO WILL EVENTUALLY TURN BACK TOWARD THE WEST...WHICH IS STILL PLAUSIBLE IF THE SYSTEM LOSES ITS REMAINING DEEP CONVECTION FASTER THAN EXPECTED. THE OFFICIAL FORECAST CLOSELY FOLLOWS THE PREVIOUS FORECAST THROUGH 24 HOURS...BUT HAS BEEN SHIFTED TO THE RIGHT AFTER THAT IN AGREEMENT WITH THE MAJORITY OF THE MODEL GUIDANCE. THE CYCLONE IS MOVING UNDERNEATH A TROPICAL UPPER TROPOSPHERIC TROUGH THAT IS HELPING TO MAINTAIN DEEP CONVECTION. THE CIMSS SHEAR ANALYSIS AND GLOBAL MODELS INDICATE THAT LATER TODAY THE CYCLONE WILL BE MOVING UNDERNEATH A ZONE OF WEAKER SHEAR ALONG THE TROUGH AXIS...ONLY TO BE REPLACED BY INCREASING NORTHERLY SHEAR ON THE WEST SIDE OF THE TROUGH STARTING IN ABOUT 48 HOURS. GUILLERMO WILL BE MOVING OVER SEA SURFACE TEMPERATURES OF 26 DEGREES CELSIUS FOR THE NEXT 24 HOURS...THEN THE OFFICIAL TRACK TAKES GUILLERMO OVER COOLER WATER. MOST OF THE INTENSITY GUIDANCE IS IN GOOD AGREEMENT ABOUT KEEPING THE CYCLONE NEAR ITS CURRENT INTENSITY THROUGH 48 HOURS...AND OUR INTENSITY FORECAST MAINTAINS GUILLERMO AS A TROPICAL STORM THROUGH 24 HOURS BEFORE BEGINNING A GRADUAL WEAKENING TREND. FORECAST POSITIONS AND MAX WINDS INITIAL 19/1500Z 30.1N 154.9W 35 KT 12HR VT 20/0000Z 31.6N 157.1W 35 KT 24HR VT 20/1200Z 33.3N 159.7W 35 KT 36HR VT 21/0000Z 34.7N 161.9W 30 KT 48HR VT 21/1200Z 35.8N 163.5W 30 KT 72HR VT 22/1200Z 37.5N 165.4W 25 KT...DISSIPATING 96HR VT 23/1200Z...DISSIPATED $$ FORECASTER R BALLARD