000 WTPZ44 KNHC 260242 TCDEP4 HURRICANE HILARY DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092011 800 PM PDT SUN SEP 25 2011 WHILE THERE HAS BEEN LITTLE MICROWAVE DATA DURING THE PAST SEVERAL HOURS TO FOLLOW THE INNER CORE EVOLUTION...IT SEEMS THAT HILARY HAS COMPLETED AN EYEWALL REPLACEMENT...AS THE EYE HAS GROWN A LITTLE LARGER AND BECOME MORE DISTINCT THIS AFTERNOON. THE LATEST OBJECTIVE AND SUBJECTIVE SATELLITE INTENSITY ESTIMATES RANGE FROM 5.5 TO 6.0 ON THE DVORAK SCALE...WHICH SUPPORT AN INTENSITY OF 110 KT. HILARY IS FORECAST TO REMAIN OVER WARM WATER AND IN A LOW SHEAR ENVIRONMENT DURING THE NEXT 2-3 DAYS. HOWEVER...THE HURRICANE IS LIKELY TO BEGIN INGESTING SOME DRIER...MORE STABLE AIR THAT IS LOCATED TO ITS NORTHWEST. THIS SHOULD RESULT IN GRADUAL WEAKENING OF THE CYCLONE DURING THE NEXT FEW DAYS. AFTER 72 HOURS...INCREASING SOUTHWESTERLY SHEAR AND COOLER SEA SURFACE TEMPERATURES SHOULD CAUSE A FASTER RATE OF WEAKENING. THE OFFICIAL FORECAST IS NEAR THE ICON CONSENSUS DURING THE FIRST COUPLE OF DAYS...AND THEN IS CLOSER TO LGEM AND FLORIDA STATE SUPERENSEMBLE...WHICH BOTH WEAKEN HILARY MORE RAPIDLY LATE IN THE PERIOD. HILARY HAS BEEN MOVING A LITTLE SOUTH OF DUE WEST THIS AFTERNOON. THE HURRICANE IS FORECAST TO MOVE ON A GENERAL WESTWARD TRACK DURING THE NEXT DAY OR SO...TO THE SOUTH OF A MID- TO UPPER-LEVEL RIDGE THAT EXTENDS FROM NORTHERN MEXICO WESTWARD OVER THE EASTERN PACIFIC. A MID- TO UPPER-LEVEL LOW CURRENTLY NEAR 27N133W IS FORECAST TO MOVE EASTWARD AND WEAKEN THE WESTERN PORTION OF THE RIDGE IN 36 TO 48 HOURS. THIS SHOULD CAUSE HILARY TO SLOW DOWN AND TURN NORTHWARD. AFTER THAT...THE MODELS INDICATE THAT HILARY WILL ACCELERATE GENERALLY NORTHWARD AROUND THE EASTERN SIDE OF THE UPPER LOW. WHILE THE TRACK GUIDANCE AGREES ON THIS SCENARIO... THERE IS A FAIR AMOUNT OF SPREAD AS TO EXACTLY WHEN HILARY TURNS NORTHWARD...AND HOW FAST IT ACCELERATES. FOR NOW...THE NHC TRACK REMAINS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE...BETWEEN THE NORMALLY RELIABLE GFS AND ECMWF MODELS. FORECAST POSITIONS AND MAX WINDS INIT 26/0300Z 16.9N 111.3W 110 KT 125 MPH 12H 26/1200Z 16.9N 112.7W 105 KT 120 MPH 24H 27/0000Z 17.0N 114.2W 100 KT 115 MPH 36H 27/1200Z 17.2N 115.4W 95 KT 110 MPH 48H 28/0000Z 17.6N 116.3W 90 KT 105 MPH 72H 29/0000Z 19.6N 116.4W 70 KT 80 MPH 96H 30/0000Z 22.5N 116.0W 50 KT 60 MPH 120H 01/0000Z 25.5N 116.5W 30 KT 35 MPH $$ FORECASTER BROWN