800 PM PDT WED JUL 31 2013 GIL HAS BEEN RAPIDLY INTENSIFYING FOR THE PAST 24-30 HR. A SMALL CENTRAL DENSE OVERCAST HAS FORMED WITH EYEWALL CLOUD TOPS COLDER THAN -80C...AND THERE ARE RAGGED OUTER BANDS NORTH AND SOUTHEAST OF THE CDO. HOWEVER...THE EYE SEEN PREVIOUSLY HAS DISAPPEARED... SUGGESTING THE POSSIBILITY THAT THE INTENSIFICATION RATE HAS SLOWED. SATELLITE INTENSITY ESTIMATES ARE 77 KT FROM TAFB AND 65 KT FROM SAB. BASED ON THIS...THE INITIAL INTENSITY IS INCREASED TO 70 KT. THE INITIAL MOTION REMAINS 285/10. GIL CONTINUES TO BE STEERED BY THE FLOW SOUTH OF A SUBTROPICAL RIDGE WHICH IS FORECAST TO PERSIST THROUGH 72 HR. THIS PATTERN WILL KEEP GIL ON A GENERAL WEST- NORTHWESTWARD TO WESTWARD TRACK. AFTER THAT...THE GFS AND ECMWF MODELS SHOW A MID/UPPER-LEVEL TROUGH NORTH OF 20N NEAR 140W THAT SHOULD WEAKEN THE RIDGE. THIS SHOULD CAUSE GIL TO SLOW ITS FORWARD MOTION BY THE END OF THE FORECAST PERIOD. THE NEW FORECAST TRACK IS AN UPDATE OF THE PREVIOUS TRACK AND LIES NEAR THE CENTER OF THE MODEL GUIDANCE ENVELOPE. THE INTENSITY FORECAST HAS TWO COMPLICATING FACTORS. THE FIRST IS THAT THE FORECAST TRACK IS ROUGHLY PARALLEL TO THE SEA SURFACE TEMPERATURE GRADIENT. A MORE NORTHERLY MOTION...SIMILAR TO THE GFS...WOULD BRING THE CYCLONE OVER COOLER SSTS AND INTO STRONGER VERTICAL WIND SHEAR AFTER 24-48 HR. A MORE SOUTHERLY MOTION... SIMILAR TO THE FLORIDA STATE SUPERENSEMBLE...WOULD KEEP GIL OVER WARMER WATER AND IN A LESS HOSTILE SHEAR ENVIRONMENT. THE SECOND FACTOR IS UNCERTAINTY AS TO WHETHER THE RAPID INTENSIFICATION IS OVER OR NOT...WITH THE RAPID INTENSIFICATION INDEX OF THE SHIPS MODEL SHOWING A DECREASED CHANCE OF CONTINUED RAPID STRENGTHENING. THE NEW INTENSITY FORECAST IS CLOSE TO THE INTENSITY CONSENSUS... EXCEPT AT 24 HR WHEN THE FORECAST PEAK INTENSITY IS A LITTLE ABOVE THE GUIDANCE. AN ALTERNATIVE SCENARIO IS THAT GIL CONTINUES TO RAPIDLY INTENSIFY FOR 12-24 HR AND GETS SIGNIFICANTLY STRONGER THAN CURRENTLY FORECAST. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 14.2N 121.8W 70 KT 80 MPH 12H 01/1200Z 14.6N 123.2W 80 KT 90 MPH 24H 02/0000Z 14.9N 125.3W 85 KT 100 MPH 36H 02/1200Z 15.2N 127.2W 80 KT 90 MPH 48H 03/0000Z 15.4N 128.8W 75 KT 85 MPH 72H 04/0000Z 15.5N 132.0W 65 KT 75 MPH 96H 05/0000Z 15.5N 135.5W 50 KT 60 MPH 120H 06/0000Z 15.5N 138.5W 40 KT 45 MPH $$ FORECASTER BEVEN MC
Posted on: Thu, 01 Aug 2013 02:41:41 +0000