550 
 WTPZ44 KNHC 252037
 TCDEP4
  
 HURRICANE HILARY DISCUSSION NUMBER  19
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092011
 200 PM PDT SUN SEP 25 2011
  
 SINCE THE PREVIOUS ADVISORY...HILARY HAS MAINTAINED A PRONOUNCED EYE
 FEATURE IN BOTH VISIBLE AND INFRARED SATELLITE IMAGERY...WHICH HAS
 BECOME EVEN MORE DISTINCT AND WARMER DURING THE PAST COUPLE OF
 HOURS. SATELLITE INTENSITY ESTIMATES ARE T6.0/115 KT FROM TAFB AND
 T5.0/90 KT FROM SAB. BASED ON THE RECENT WARMING AND CLEARING OUT
 OF THE EYE...THE INITIAL INTENSITY WILL REMAIN A LITTLE ABOVE THE
 AVERAGE OF THESE INTENSITY ESTIMATES AND AS A MAJOR HURRICANE.
 
 HILARY HAS BEEN MOVING IN A STEADY WESTWARD MOTION OR 270/9 KT FOR
 THE PAST 6 HOURS. THE HURRICANE IS MOVING AROUND THE SOUTHERN
 PERIPHERY OF A STRONG DEEP-LAYER RIDGE EXTENDING WESTWARD TO THE
 NORTH OF THE CYCLONE. THIS STEERING FLOW PATTERN SHOULD RESULT IN A
 WESTWARD MOTION FOR THE NEXT 24 HOURS OR SO...FOLLOWED BY A TURN TO
 THE WEST-NORTHWEST AFTER THAT. BY 72 HOURS...A MID- TO UPPER-LEVEL
 LOW...INDICATED IN WATER VAPOR IMAGERY NEAR 23N 134W...IS FORECAST
 TO MOVE EASTWARD AND ERODE THE WESTERN PORTION OF THE RIDGE AND
 ALLOW HILARY TO MOVE SLOWLY NORTHWARD. BY DAYS 4 AND 5...HILARY IS
 FORECAST TO UNDERGO SOME BINARY INTERACTION WITH THE UPPER-LOW AND
 MOVE NORTHWARD OR EVEN NORTH-NORTHWESTWARD AT A SLIGHTLY FASTER
 FORWARD SPEED. THE NHC FORECAST TRACK IS A LITTLE TO THE LEFT OF
 THE PREVIOUS ADVISORY TRACK...AND LIES ABOUT MIDWAY BETWEEN THE GFS
 AND ECMWF MODEL FORECASTS.
 
 HILARY IS EXPECTED TO REMAIN IN A LOW VERTICAL SHEAR REGIME AND OVER
 WARM WATERS FOR THE NEXT 72 HOURS...WHICH WOULD GENERALLY FAVOR
 STRENGTHENING OR AT LEAST MAINTAIN A STEADY INTENSITY.  HOWEVER...
 THE MID-LEVEL MOISTURE SURROUNDING THE HURRICANE IS ALREADY FAIRLY
 DRY AND IS FORECAST TO DROP BELOW 40 PERCENT HUMIDITY BY 24-36
 HOURS. A 25/1511Z SSMIS MICROWAVE OVERPASS INDICATED DRY AIR
 ALREADY BEGINNING TO WRAP INTO THE SOUTHERN SEMICIRCLE OF THE INNER
 CORE CIRCULATION...WHICH MAY CAUSE EROSION OF THE CONVECTION AROUND
 THE EYE FAIRLY SOON. AS A RESULT...GRADUAL WEAKENING IS FORECAST
 FOR THE NEXT 3-4 DAYS...WITH MORE RAPID WEAKENING AFTER THAT AS
 HILARY MOVES OVER WATER COLDER THAN 24C AND INTO INCREASING
 SOUTHWESTERLY VERTICAL SHEAR. THE OFFICIAL INTENSITY FORECAST
 FOLLOWS THE TREND OF INTENSITY CONSENSUS MODEL...ICON...THROUGH 72
 HOURS AND THEN IS BELOW THE CONSENSUS MODEL AFTER THAT.
 
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  25/2100Z 17.1N 110.3W  110 KT 125 MPH
  12H  26/0600Z 17.2N 111.6W  105 KT 120 MPH
  24H  26/1800Z 17.3N 113.2W  105 KT 120 MPH
  36H  27/0600Z 17.6N 114.7W  100 KT 115 MPH
  48H  27/1800Z 18.1N 115.6W   95 KT 110 MPH
  72H  28/1800Z 19.7N 116.2W   80 KT  90 MPH
  96H  29/1800Z 22.1N 115.8W   60 KT  70 MPH
 120H  30/1800Z 25.0N 116.0W   40 KT  45 MPH
  
 $$
 FORECASTER STEWART