ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM HURRICANE GUILLERMO DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP102009 200 AM PDT FRI AUG 14 2009 GUILLERMO IS UPGRADED TO A 65-KT HURRICANE BASED ON THE APPEARANCE OF AN EYE IN MICROWAVE IMAGERY FROM A 0151 UTC SSMIS PASS AND A 0218 UTC AMSU PASS...ALONG WITH CONSENSUS DVORAK T-NUMBERS OF 4.0 FROM TAFB AND SAB AT 0600 UTC. ALTHOUGH THE EYE IS NOT APPARENT IN GEOSTATIONARY INFRARED IMAGERY...THE CENTER APPEARS TO BE LOCATED ON THE NORTHERN SIDE OF THE CDO BETWEEN TWO CURVED BANDS OF COLD CLOUD TOPS THAT HAVE DEVELOPED OVER THE PAST COUPLE OF HOURS. VERTICAL SHEAR IS FORECAST TO REMAIN LOW AND THE SYSTEM WILL REMAIN OVER SSTS ABOVE 26C FOR THE NEXT 12 TO 24 HOURS...SO SOME SLIGHT STRENGTHENING IS FORECAST IN THE SHORT TERM. AFTER 24 HOURS...THE INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS PACKAGE...SHOWING A GRADUAL SPIN DOWN AS THE CYCLONE ENTERS PROGRESSIVELY COOLER WATERS AND VERTICAL SHEAR INCREASES. THE FORECAST IS CLOSE TO THE INTENSITY CONSENSUS ICON THROUGH 72 HOURS...BUT IS BELOW ICON AT DAYS 4 AND 5...AS THE HWRF AND ESPECIALLY THE GFDL SEEM TOO SLOW TO WEAKEN GUILLERMO GIVEN THE HOSTILE ENVIRONMENT EXPECTED AT THAT TIME. MICROWAVE IMAGERY AND AN AMBIGUITY ANALYSIS FROM A 0259 UTC QUIKSCAT PASS SHOW THAT GUILLERMO IS LOCATED SLIGHTLY TO THE NORTH OF THE PREVIOUS FORECAST TRACK...WITH AN INITIAL MOTION ESTIMATE OF 280/13. THE TRACK FORECAST REASONING REMAINS UNCHANGED. GUILLERMO IS MOVING AROUND THE SOUTHWESTERN PERIPHERY OF THE MID-LEVEL SUBTROPICAL RIDGE AND WILL FEEL THE INFLUENCE OF A WEAKNESS IN THE RIDGE THAT DEVELOPS EAST-NORTHEAST OF THE HAWAIIAN ISLANDS BY DAYS 4 AND 5. THEREFORE...A WEST TO WEST-NORTHWEST MOTION IS EXPECTED THROUGH THE PERIOD...EVEN AFTER THE CYCLONE BECOMES A SHALLOWER SYSTEM. THE TRACK FORECAST HAS BEEN ADJUSTED A LITTLE TO THE NORTH OF THE PREVIOUS PACKAGE TO ACCOUNT FOR THE INITIAL MOTION AND A NORTHWARD SHIFT IN THE TVCN TRACK MODEL CONSENSUS. THE INITIAL 34-KT WIND RADII WERE ADJUSTED BASED ON DATA FROM THE THE AFOREMENTIONED QUIKSCAT PASS. FORECAST POSITIONS AND MAX WINDS INITIAL 14/0900Z 17.6N 125.9W 65 KT 12HR VT 14/1800Z 17.9N 127.9W 70 KT 24HR VT 15/0600Z 18.4N 130.5W 70 KT 36HR VT 15/1800Z 19.0N 133.1W 60 KT 48HR VT 16/0600Z 19.6N 135.7W 55 KT 72HR VT 17/0600Z 21.0N 141.0W 45 KT 96HR VT 18/0600Z 22.0N 146.0W 35 KT 120HR VT 19/0600Z 23.0N 151.0W 30 KT $$ FORECASTER BRENNAN NNNN
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Page last modified: Thursday, 31-Dec-2009 12:09:22 UTC