000 WTPZ44 KNHC 250328 TCDEP4 TROPICAL STORM FRANK DISCUSSION NUMBER 14 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092010 800 PM PDT TUE AUG 24 2010 THE CENTER OF FRANK HAS BEEN DIFFICULT TO DISCERN IN INFRARED SATELLITE IMAGERY. HOWEVER...EARLIER AMSR-E AND AMSU MICROWAVE OVERPASSES WERE VERY HELPFUL IN LOCATING THE CENTER...WHICH IS NEAR THE NORTHEASTERN EDGE OF THE DEEP CONVECTION. THE INITIAL INTENSITY IS SET AT 55 KT...IN AGREEMENT WITH DVORAK DATA T-NUMBERS OF 3.5 OR 55 KT FROM SAB AND TAFB. STRONG EASTERLY SHEAR CONTINUES TO IMPACT THE CYCLONE. THE SHEAR IS FORECAST TO DECREASE SOMEWHAT OVER THE NEXT DAY OR SO AND IS EXPECTED TO GIVE FRANK AN OPPORTUNITY TO STRENGTHEN. HOWEVER...THE INTENSITY GUIDANCE SHOWS LESS INTENSIFICATION THAN BEFORE. ALTHOUGH THE 18Z GFDL AND HWRF MODELS HAVE FRANK REACHING HURRICANE INTENSITY VERY SOON...THIS SEEMS UNREALISTIC GIVEN THE CURRENT STRONG SHEAR. THE SHIPS MODEL APPEARS MORE REASONABLE BY STRENGTHENING FRANK AFTER THE SHEAR DECREASES. THE OFFICIAL FORECAST PREDICTS GRADUAL STRENGTHENING DURING THE NEXT 24-36 HOURS AND BRINGS FRANK TO HURRICANE STRENGTH. THIS IS IN BEST AGREEMENT WITH THE SHIPS MODEL...WHICH IS AT THE HIGH END OF THE GUIDANCE. BEYOND 72 HOURS...STEADY WEAKENING SHOULD OCCUR AS FRANK MOVES OVER COOLER WATER AND INTO A MORE STABLE ENVIRONMENT. THE UPDATED FORECAST IS CLOSE TO THE INTENSITY CONSENSUS AT 96 AND 120 HOURS...WHICH IS LOWER THAN THE PREVIOUS ADVISORY. THE TRACK FORECAST REASONING REMAINS UNCHANGED. FRANK IS MOVING WEST-NORTHWEST OR 285/8 KT. THIS MOTION IS EXPECTED TO CONTINUE DURING THE NEXT FEW DAYS AS FRANK IS STEERED BY A DEEP-LAYER RIDGE OVER WESTERN NORTH AMERICA. AT DAYS 4 AND 5...FRANK IS EXPECTED TO DECELERATE AS A TROUGH ALONG THE WEST COAST OF THE UNITED STATES WEAKENS THE WESTERN PERIPHERY OF THE RIDGE. THE TRACK GUIDANCE HAS SHIFTED A LITTLE WESTWARD DURING THE FIRST FEW DAYS OF THE FORECAST PERIOD AND THE OFFICIAL FORECAST HAS BEEN NUDGED IN THAT DIRECTION. FORECAST POSITIONS AND MAX WINDS INITIAL 25/0300Z 16.0N 102.9W 55 KT 12HR VT 25/1200Z 16.4N 104.1W 55 KT 24HR VT 26/0000Z 17.1N 105.9W 60 KT 36HR VT 26/1200Z 17.7N 107.7W 65 KT 48HR VT 27/0000Z 18.3N 109.3W 65 KT 72HR VT 28/0000Z 19.5N 111.8W 60 KT 96HR VT 29/0000Z 20.5N 113.0W 50 KT 120HR VT 30/0000Z 21.5N 113.5W 35 KT $$ FORECASTER BROWN