ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM GIL DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL EP072013 200 PM PDT SAT AUG 03 2013 DEEP CONVECTION HAS CONTINUED TO BURST INTERMITTENTLY NEAR THE CENTER OF GIL DURING THE PAST SEVERAL HOURS. DVORAK CI ESTIMATES RANGE FROM 35 TO 65 KT...A DISCREPANCY THAT CAN BE EXPLAINED IN PART BY THE PULSATING NATURE OF THE CONVECTION. THE INTENSITY HAS BEEN HELD AT 50 KT AS A CONSERVATIVE COMPROMISE BETWEEN THESE ESTIMATES...HOWEVER BASED ON LONG-TERM TRENDS...THIS MAY BE GENEROUS. THE INTENSITY GUIDANCE HAS NOT COME INTO BETTER AGREEMENT. THE STATISTICAL MODELS FORECAST THAT THE INTENSITY WILL NOT CHANGE MUCH DURING THE NEXT COUPLE OF DAYS...AND THAT STRENGTHENING WILL OCCUR AFTER THAT. THE UW-CIMSS SHEAR ANALYSIS SUGGESTS THAT THE SHEAR IS SUBSTANTIALLY HIGHER THAN THE SHIPS ANALYSIS INDICATES...WHICH MAY EXPLAIN WHY THE STATISTICAL MODELS FORECAST INTENSIFICATION. THE OFFICIAL FORECAST HAS NOT BEEN CHANGED SUBSTANTIALLY...AND LEANS TOWARD THE DYNAMICAL MODEL CONSENSUS FORECAST OF GRADUAL WEAKENING. GIL CONTINUES TO MOVE ON A STEADY WESTWARD HEADING AT 11 KT... STEERED BY A MID-LEVEL RIDGE LOCATED TO THE NORTHEAST. THE GLOBAL MODELS AGREE THAT THIS RIDGE WILL BUILD TOWARD THE SOUTHWEST OVER THE NEXT 48 TO 72 HOURS...WHICH SHOULD CAUSE THE CYCLONE TO TURN TOWARD THE WEST-SOUTHWEST. AFTER THAT TIME...THERE IS ONCE AGAIN A LARGE AMOUNT OF SPREAD IN THE TRACK GUIDANCE. IN FACT...THE GFS AND ECMWF MODEL DAY 5 FORECAST POSITIONS ARE NEARLY 600 MILES APART. THE PRIMARY DIFFERENCE BETWEEN THESE MODELS SEEMS TO BE THE DEPTH OF THE CIRCULATION. THE ECMWF FORECASTS A MUCH SHALLOWER SYSTEM THAT IS STEERED PRIMARILY BY LOW-LEVEL EASTERLIES...WHILE THE GFS FORECASTS A DEEPER CYCLONE THAT SLOWS AND TURNS TOWARD THE NORTH. THE OFFICIAL FORECAST IS A BLEND OF THESE TWO SOLUTIONS... AND CALLS FOR WESTWARD MOTION AFTER DAY 3...IN LINE WITH THE INTENSITY FORECAST FOR A WEAKER CYCLONE. FORECAST POSITIONS AND MAX WINDS INIT 03/2100Z 15.3N 133.6W 50 KT 60 MPH 12H 04/0600Z 15.3N 134.9W 45 KT 50 MPH 24H 04/1800Z 14.8N 136.3W 45 KT 50 MPH 36H 05/0600Z 14.4N 137.6W 45 KT 50 MPH 48H 05/1800Z 13.9N 139.2W 40 KT 45 MPH 72H 06/1800Z 13.0N 142.0W 40 KT 45 MPH 96H 07/1800Z 13.0N 145.0W 35 KT 40 MPH 120H 08/1800Z 13.0N 148.0W 30 KT 35 MPH $$ FORECASTER FRANKLIN/ZELINSKY NNNN