000 WTPZ44 KNHC 300848 TCDEP4 TROPICAL STORM KEVIN DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP142009 200 AM PDT SUN AUG 30 2009 ALTHOUGH KEVIN HAS BEEN UNDER THE INFLUENCE OF SOME EASTERLY SHEAR...THE LOW-LEVEL CENTER IS NOW LOCATED JUST UNDERNEATH THE HEAD OF A CURVED BAND THAT WRAPS AROUND THE WESTERN SIDE OF THE CIRCULATION...AND THIS PATTERN IS YIELDING DVORAK ESTIMATES OF T3.0...45 KT...FROM TAFB AND SAB. IN ADDITION...A 0243 UTC QUIKSCAT PASS SUPPORTS MAINTAINING THE INITIAL INTENSITY AT 45 KT. WITH THE HELP OF A 0045 UTC TRMM AND A 0155 UTC WINDSAT PASS...THE INITIAL MOTION IS ESTIMATED AT 360/6. KEVIN LIES ON THE WESTERN SIDE OF A MID-LEVEL ANTICYCLONE CENTERED BETWEEN IT AND HURRICANE JIMENA...AND THIS IS CAUSING THE CURRENT NORTHWARD MOTION. HOWEVER...THE STEERING CURRENTS ARE EXPECTED TO REMAIN LIGHT DURING THE NEXT SEVERAL DAYS...AND KEVIN IS FORECAST TO MOVE SLOWLY NORTH-NORTHEASTWARD TO NORTHEASTWARD DURING THAT TIME. ONE COMPLICATING FACTOR TO THIS FORECAST IS HOW KEVIN WILL INTERACT WITH THE CIRCULATION OF JIMENA. MOST OF THE GLOBAL MODELS ARE PLAYING A GAME OF PINBALL...PULLING KEVIN NORTHEASTWARD TOWARD JIMENA AND THEN PUSHING IT BACK TO THE SOUTH OR SOUTHEAST TOWARD A NEW AREA OF LOW PRESSURE EXPECTED TO DEVELOP FARTHER EAST. THE HWRF AND CANADIAN MODELS ARE THE ONLY TWO WHICH STILL SHOW KEVIN TURNING NORTHWESTWARD IN RESPONSE TO A BUILDING RIDGE TO THE NORTH. THE NEW OFFICIAL FORECAST IS SHIFTED A LITTLE EAST OF THE PREVIOUS FORECAST TOWARD THE MODEL CONSENSUS AND SHOWS VERY LITTLE MOTION BY DAYS 4 AND 5 DUE TO THE LARGE UNCERTAINTY. THE INTENSITY GUIDANCE SHOWS KEVIN STRENGTHENING VERY LITTLE OVER THE NEXT 24-48 HOURS. KEVIN WILL REMAIN OVER SUFFICIENTLY WARM WATER...BUT THE SHIPS GUIDANCE INDICATES THAT SOME EASTERLY SHEAR WILL CONTINUE OVER THE SYSTEM FOR THE NEXT DAY OR TWO. ALSO...BOTH THE GFDL AND HWRF INDICATE NO FURTHER STRENGTHENING AND STEADY WEAKENING OVER THE NEXT FEW DAYS. THE OFFICIAL FORECAST ASSUMES THAT KEVIN WILL BE ADVERSELY AFFECTED BY HURRICANE JIMENA AND SHOWS SLOW WEAKENING STARTING AT 36 HOURS...BUT IT IS STILL ABOVE THE INTENSITY CONSENSUS. MANY OF THE GLOBAL MODELS LOSE A COHERENT VORTEX BY DAYS 4 AND 5...AND IT IS POSSIBLE THAT KEVIN MAY NOT EXIST AS A TROPICAL CYCLONE BY THEN. FORECAST POSITIONS AND MAX WINDS INITIAL 30/0900Z 14.1N 121.9W 45 KT 12HR VT 30/1800Z 14.7N 121.9W 50 KT 24HR VT 31/0600Z 15.5N 121.4W 50 KT 36HR VT 31/1800Z 16.2N 120.8W 45 KT 48HR VT 01/0600Z 16.9N 120.2W 40 KT 72HR VT 02/0600Z 18.3N 119.1W 40 KT 96HR VT 03/0600Z 19.0N 118.5W 35 KT 120HR VT 04/0600Z 19.2N 118.2W 30 KT $$ FORECASTER BERG