000 WTPZ45 KNHC 260850 TCDEP5 HURRICANE DARBY DISCUSSION NUMBER 14 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP052010 200 AM PDT SAT JUN 26 2010 DARBY IS AN INCREDIBLY SMALL HURRICANE. AN ASCAT PASS AROUND 0345 UTC INDICATED THAT TROPICAL STORM FORCE WINDS DO NOT EXTEND ANY FARTHER THAN ABOUT 35 N MI FROM THE CENTER. THE HURRICANE HAD BEEN MAINTAINING A SMALL 10-N MI WIDE EYE SURROUNDED BY DEEP CONVECTION...WHICH SUPPORTED 0600 UTC DVORAK ESTIMATES OF T5.5 FROM BOTH TAFB AND SAB. HOWEVER...THE EYE HAS RECENTLY BECOME OBSCURED...AND THE MOST RECENT ADT ESTIMATE FROM UW-CIMSS IS T5.1. THE INITIAL INTENSITY IS THEREFORE LOWERED TO 95 KT. VERTICAL SHEAR IS EXPECTED TO INCREASE OVER DARBY OVER THE NEXT SEVERAL DAYS...WHICH IS EXPECTED TO INDUCE GRADUAL WEAKENING. THE WEAKENING IS EXPECTED TO BE MORE RAPID FROM 72-120 HOURS AS A STRONG UPPER RIDGE BUILDS OVER MEXICO...CREATING FAIRLY STRONG UPPER-LEVEL EASTERLY WINDS NEAR THE CYCLONE. THE NEW OFFICIAL FORECAST CLOSELY FOLLOWS THE SHIPS AND LGEM INTENSITY GUIDANCE...AND IS NOT TOO DIFFERENT FROM THE PREVIOUS ADVISORY. DARBY HAS BEEN MOVING ALMOST WEST-SOUTHWESTWARD OVER THE PAST FEW HOURS...AND THE INITIAL MOTION IS 260/5. THE STEERING CURRENTS AROUND THE HURRICANE ARE STILL EXPECTED TO COLLAPSE THROUGH THE FORECAST PERIOD...AND DARBY SHOULD BEGIN TO MOVE VERY SLOWLY WESTWARD OVER THE NEXT 24-36 HOURS. THEREAFTER...THE CYCLONE IS EXPECTED TO BEGIN FEELING THE INFLUENCE OF NEWLY-NAMED TROPICAL STORM ALEX IN THE WESTERN CARIBBEAN. THE OFFICIAL FORECAST INDICATES A SLOW NORTHEASTWARD MOTION BETWEEN DAYS 3 AND 5...BUT IT SHOULD BE NOTED THAT THE GUIDANCE ENVELOPE IS STILL RATHER DIVERGENT AND DARBY COULD DRIFT OR MEANDER IN PLACE FOR SEVERAL DAYS. THE ECMWF SHOWS A QUICK NORTHEASTWARD MOTION AND BRINGS DARBY TO THE MEXICAN COAST IN 3 DAYS...BUT THIS SOLUTION IS DISCOUNTED AT THIS TIME. FORECAST POSITIONS AND MAX WINDS INITIAL 26/0900Z 13.5N 102.7W 95 KT 12HR VT 26/1800Z 13.4N 103.4W 90 KT 24HR VT 27/0600Z 13.4N 104.1W 85 KT 36HR VT 27/1800Z 13.6N 104.4W 75 KT 48HR VT 28/0600Z 13.9N 104.1W 70 KT 72HR VT 29/0600Z 14.3N 103.3W 55 KT 96HR VT 30/0600Z 14.7N 102.8W 45 KT 120HR VT 01/0600Z 15.0N 102.5W 35 KT $$ FORECASTER BERG