000 WTPZ45 KNHC 241436 TCDEP5 HURRICANE DARBY DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP052010 800 AM PDT THU JUN 24 2010 DARBY HAS A SMALL BUT SYMMETRIC CDO WITH SOME BANDING FEATURES OVER THE WESTERN SEMICIRCLE. LATEST DVORAK INTENSITY ESTIMATES ARE 65 KT AND 55 KT FROM SAB AND TAFB RESPECTIVELY...AND DARBY IS BEING UPGRADED TO A 65-KT HURRICANE AT THIS TIME. SINCE VERTICAL SHEAR IS FORECAST TO REMAIN LIGHT FOR THE NEXT COUPLE OF DAYS... ADDITIONAL STRENGTHENING SEEMS LIKELY. THE OFFICIAL INTENSITY FORECAST IS ROUGHLY A BLEND OF THE SHIPS/LGEM AND GFDL MODEL GUIDANCE. BY AROUND 72 HOURS...GLOBAL MODEL PREDICTIONS INDICATE INCREASING SOUTHEASTERLY TO EASTERLY SHEAR OVER DARBY WHICH WOULD INDUCE WEAKENING...AS SHOWN BY THE OFFICIAL FORECAST. HOWEVER SINCE THE TROPICAL CYCLONE IS FORECAST TO REMAIN OVER SEA SURFACE TEMPERATURES THAT ARE QUITE WARM THROUGH 5 DAYS...DARBY MIGHT NOT WEAKEN AS MUCH AS SHOWN BY 4 AND 5 DAYS. THE FORWARD SPEED IS SLOWING AND THE INITIAL MOTION IS NOW ESTIMATED TO BE 285/8. THE LOW- TO MID-LEVEL RIDGE TO THE NORTH OF DARBY IS FORECAST TO GRADUALLY WEAKEN SO A CONTINUED DECELERATION IS EXPECTED OVER THE NEXT COUPLE OF DAYS. AFTER 36 HOURS...THE TRACK GUIDANCE BECOMES QUITE DIVERSE SUGGESTING THAT THE STEERING CURRENTS WILL BECOME VERY WEAK. BY DAYS 4-5...THERE IS STILL THE POSSIBILITY OF SOME INTERACTION BETWEEN DARBY AND THE SYSTEM CURRENTLY SITUATED OVER THE WESTERN CARIBBEAN. THIS WOULD BE MORE LIKELY IF THE LATTER SYSTEM TAKES A MORE SOUTHERN TRACK AND STRENGTHENS OVER THE BAY OF CAMPECHE BY AROUND 96 HOURS AS SHOWN IN THE FORECAST FROM THE ECMWF GLOBAL MODEL. FOR THE TIME BEING THE OFFICIAL TRACK FORECAST...LIKE THE PREVIOUS ONE...ONLY SHOWS A NORTH TO NORTHEAST DRIFT OVER THE LAST 2 DAYS OF THE FORECAST PERIOD. FORECAST POSITIONS AND MAX WINDS INITIAL 24/1500Z 12.8N 98.7W 65 KT 12HR VT 25/0000Z 13.0N 99.8W 70 KT 24HR VT 25/1200Z 13.3N 101.1W 75 KT 36HR VT 26/0000Z 13.5N 102.1W 80 KT 48HR VT 26/1200Z 13.7N 102.9W 80 KT 72HR VT 27/1200Z 14.0N 103.5W 70 KT 96HR VT 28/1200Z 14.5N 103.5W 65 KT 120HR VT 29/1200Z 15.0N 103.0W 55 KT $$ FORECASTER PASCH