Hurricane HILARY

ZCZC MIATCDEP4 ALL
TTAA00 KNHC DDHHMM
 
HURRICANE HILARY DISCUSSION NUMBER  17
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092011
200 AM PDT SUN SEP 25 2011
 
CLOUD TOP TEMPERATURES AROUND THE EYE OF HILARY HAVE WARMED A BIT
OVER THE PAST FEW HOURS. DVORAK CI- AND FINAL-T NUMBERS AT 06Z FROM
BOTH TAFB AND SAB WERE 5.0 AND 6.0...RESPECTIVELY. LEANING TOWARD
THE HIGHER END OF THE CI/FINAL-T NUMBER BLEND...THE INITIAL
INTENSITY IS LOWERED TO 110 KT. THERE HAS BEEN LITTLE RECENT
MICROWAVE IMAGERY TO SHOW HOW THE INNER CORE OF HILARY HAS
EVOLVED...BUT IT IS POSSIBLE THAT INNER-CORE DYNAMICS SUCH AS
EYEWALL REPLACEMENT CYCLES WILL RESULT IN FLUCTUATIONS IN INTENSITY
OVER THE NEXT DAY OR TWO. OTHER THAN THOSE FLUCTUATIONS...GRADUAL
WEAKENING IS INDICATED BY MOST OF THE INTENSITY GUIDANCE THROUGH 48
HOURS...AND THIS IS REFLECTED IN THE OFFICIAL FORECAST. LATE IN THE
PERIOD...MORE RAPID WEAKENING SHOULD BEGIN AS HILARY MOVES INTO
COOLER WATERS AND VERTICAL SHEAR INCREASES...ESPECIALLY AT DAYS 4
AND 5. THE NEW NHC FORECAST AT THOSE TIMES IS CLOSE TO THE LGEM
MODEL.
 
SMOOTHING THROUGH THE TROCHOIDAL WOBBLES OF THE CENTER OVER THE PAST
12 TO 18 HOURS...THE INITIAL MOTION ESTIMATE IS 275/08...AS HILARY
CONTINUES TO BE STEERED BY A LARGE SUBTROPICAL RIDGE TO ITS NORTH.
DURING THE FORECAST PERIOD...THE RIDGE WILL WEAKEN AS A MID/UPPER-
LEVEL LOW NOW LOCATED NEAR 25N 135W MOVES EASTWARD. AS THE RIDGE
WEAKENS...HILARY SHOULD SLOW DOWN AND TURN TOWARD THE WEST-
NORTHWEST IN ABOUT 3 DAYS. THEN AS THE MID/UPPER-LEVEL LOW
AMPLIFIES TO THE NORTHWEST OR WEST OF HILARY AT DAYS 4 AND 5...THE
CYCLONE SHOULD BE DRAWN NORTHWARD OR NORTH-NORTHEASTWARD WITH SOME
INCREASE IN FORWARD SPEED. THE USUALLY RELIABLE GFS AND ECMWF
MODELS ARE NOW IN BETTER AGREEMENT ON THIS SCENARIO. THE NEW NHC
TRACK FORECAST IS A LITTLE SOUTH OF THE PREVIOUS ONE THROUGH 48
HOURS DUE TO THE INITIAL POSITION. AT DAYS 4 AND 5 THE NHC FORECAST
HAS BEEN NUDGED EASTWARD AND IS CLOSE TO THE TVCE MULTI-MODEL
CONSENSUS AND A BLEND OF THE GFS AND ECMWF MODELS.
 
THE INITIAL 34-KT WIND RADII WERE ADJUSTED INWARD BASED ON DATA FROM
A 0450 UTC ASCAT PASS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  25/0900Z 17.0N 108.4W  110 KT 125 MPH
 12H  25/1800Z 17.1N 109.7W  110 KT 125 MPH
 24H  26/0600Z 17.1N 111.4W  105 KT 120 MPH
 36H  26/1800Z 17.2N 113.1W  105 KT 120 MPH
 48H  27/0600Z 17.3N 114.6W  100 KT 115 MPH
 72H  28/0600Z 18.2N 116.4W   85 KT 100 MPH
 96H  29/0600Z 20.5N 116.0W   70 KT  80 MPH
120H  30/0600Z 23.5N 115.5W   55 KT  65 MPH
 
$$
FORECASTER BRENNAN
 
NNNN