000 WTPZ44 KNHC 300237 TCDEP4 TROPICAL STORM KEVIN DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP142009 800 PM PDT SAT AUG 29 2009 VISIBLE SATELLITE IMAGERY AND A 2113Z 36 GHZ AMSR-E MICROWAVE OVERPASS SUGGEST DEVELOPMENT OF A BANDING EYE FEATURE. A CIMSS/NESDIS/NRL AMSU INTENSITY ESTIMATE AROUND THE SAME TIME PERIOD REFLECTS AN INTENSITY OF 48 KT. THE INITIAL INTENSITY IS INCREASED TO 45 KT BASED ON THESE DATA AND A BLEND OF THE SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB. SOME INTENSIFICATION IS FORECAST DURING THE NEXT 36 HOURS. AFTERWARD...KEVIN IS EXPECTED WEAKEN AS THE CYCLONE MOVES WITHIN INCREASING EASTERLY SHEAR DUE TO THE OUTFLOW ASSOCIATED WITH HURRICANE JIMENA AND SLIGHTLY COOLER WATER. THE INTENSITY FORECAST IS BASED PRIMARILY ON THE ICON INTENSITY CONSENSUS AND IS SIMILAR TO THE PREVIOUS ADVISORY. KEVIN IS CURRENTLY RESIDING WITHIN A WEAK STEERING ENVIRONMENT ASSOCIATED WITH A MID TO UPPER TROUGH EXTENDING SOUTHWESTWARD FROM CENTRAL MEXICO...AND A MID-LEVEL ANTICYCLONE SITUATED BETWEEN THE CYCLONE AND HURRICANE JIMENA. CONSEQUENTLY...THIS SYNOPTIC PATTERN HAS RESULTED IN A NORTHWARD DRIFT 350/5 DURING THE PAST 6 HOURS. AS NOTED IN THE PREVIOUS DISCUSSION...TWO MODEL CLUSTERS DESCRIBE DISSIMILAR FORECAST SCENARIOS. THE GFDL/GFDN/NOGAPS/GFS/GFS ENSEMBLE/UKMET AND THE ECMWF GROUP SUGGEST A GRADUAL NORTH TO NORTHEASTWARD MOTION THROUGH THE ENTIRE FORECAST PERIOD. THE SECOND CLUSTER INCLUDES THE HWRF/FSU SUPERENSEMBLE AND THE CANADIAN. THESE MODELS DIFFER BY SHOWING A TURN TOWARD THE NORTHWEST IN RESPONSE TO A BUILDING MID-LEVEL RIDGE TO THE NORTHEAST OF THE CYCLONE AFTER THE 72 HOUR PERIOD. SINCE THE SPREAD BETWEEN THE TWO MODEL GROUPINGS REMAINS QUITE LARGE...THE OFFICIAL FORECAST FOLLOWS CLOSELY TO THE MODEL CONSENSUS AND SLIGHTLY FAVORS THE MORE DOMINANT CLUSTER. A REDUCTION IN FORWARD SPEED BEYOND 48 HOURS IS ALSO REFLECTED IN THE FORECAST TRACK. FORECAST POSITIONS AND MAX WINDS INITIAL 30/0300Z 13.4N 122.1W 45 KT 12HR VT 30/1200Z 13.9N 122.2W 50 KT 24HR VT 31/0000Z 14.8N 122.0W 50 KT 36HR VT 31/1200Z 15.6N 121.5W 50 KT 48HR VT 01/0000Z 16.3N 121.0W 45 KT 72HR VT 02/0000Z 17.5N 120.0W 45 KT 96HR VT 03/0000Z 18.5N 119.0W 40 KT 120HR VT 04/0000Z 19.0N 118.5W 35 KT $$ FORECASTER ROBERTS/BEVEN