Hurricane HILARY

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HURRICANE HILARY DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092011
800 AM PDT FRI SEP 23 2011
 
HILARY IS MAINTAINING ITSELF AS AN IMPRESSIVE MAJOR HURRICANE WITH
VERY COLD AND SYMMETRIC CLOUD TOPS SURROUNDING A SMALL WARM EYE.
BOTH THE TAFB AND SAB SUBJECTIVE AND ADVANCED DVORAK TECHNIQUES
SUGGEST WINDS OF AT LEAST 125 KT...WHICH IS THE INTENSITY ANALYZED
THIS MORNING. THE SIZE OF THE CYCLONE CONTINUES TO BE QUITE SMALL
AS INDICATED BY A LACK OF TROPICAL-STORM-FORCE WINDS ON THE EAST
SIDE OF A NEARBY ASCAT PASS AND A CIRA AMSU WIND RADII ESTIMATE.
ALSO...NO TROPICAL-STORM-FORCE WINDS HAVE BEEN REPORTED ALONG THE
COAST OF MEXICO THIS MORNING.
 
THE HURRICANE IS MOVING TOWARD THE WEST AT ABOUT 9 KT...PRIMARILY
BEING STEERED BY THE INFLUENCE OF A ZONALLY-ORIENTED DEEP-LAYERED
RIDGE NORTH OF HILARY.  THE CYCLONE SHOULD CONTINUE WITH THIS
GENERAL MOTION FOR THE NEXT THREE DAYS OR SO.  AT THE EXTENDED
RANGE...HOWEVER...THERE EXISTS A LARGE SPREAD IN THE TRACK
GUIDANCE.  THE REGIONAL HURRICANE MODELS RECURVE HILARY TOWARD
MEXICO DUE TO A VIGOROUS SHORTWAVE TROUGH IMPINGING UPON THE
AFOREMENTIONED RIDGE...WHILE THE 00Z UKMET AND ECMWF MODELS
INDICATE A CONTINUED WEST-NORTHWESTWARD MOTION.  OF NOTE IS THAT
THE GFS AND NOGAPS MODELS ARE NOW SPLITTING THE DIFFERENCE WITH A
NORTHWARD MOTION INDICATED AT DAYS 4 AND 5 AFTER PREVIOUSLY SHOWING
A MORE WESTWARD TRAJECTORY. THE OFFICIAL FORECAST SHOWS NO CHANGE
FROM THE PREVIOUS ADVISORY AT THIS POINT...THOUGH MORE OF A TURN
TOWARD THE NORTH OR EVEN NORTHEAST AT THE EXTENDED RANGE COULD BE
MADE LATER IF THE 12Z MODEL SUITE AGREES WITH THE TREND IN THE
GUIDANCE.
 
THE INTENSITY...FOR ONCE...MAY BE EASIER TO PREDICT THAN THE TRACK
FORECAST.  HILARY SHOULD REMAIN OVER VERY WARM WATERS...IN MOIST
AIR...AND WITHIN LOW VERTICAL WIND SHEAR FOR THE NEXT TWO TO THREE
DAYS.  SO IT IS QUITE LIKELY THAT HILARY WILL CONTINUE AS A MAJOR
HURRICANE DURING THAT TIME.  INTENSITY VARIATIONS THAT OCCUR MAY BE
DOMINATED BY INTERNAL DYNAMICS...SUCH AS EYEWALL REPLACEMENT
CYCLES...WHICH WE HAVE VERY LIMITED ABILITY TO ANTICIPATE. BY DAYS 4
AND 5...THE CYCLONE SHOULD ENCOUNTER GRADUALLY DECREASING SSTS...
LESS UNSTABLE AIR...AND INCREASING VERTICAL SHEAR SHOULD LIKELY
RESULT IN A WEAKENING TREND.  THE INTENSITY FORECAST IS BASED UPON
THE LGEM AND SHIPS STATISTICAL MODELS AND IS QUITE CLOSE TO THE
PREVIOUS ADVISORY.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/1500Z 16.1N 102.5W  125 KT 145 MPH
 12H  24/0000Z 16.2N 103.8W  130 KT 150 MPH
 24H  24/1200Z 16.5N 105.5W  125 KT 145 MPH
 36H  25/0000Z 17.0N 107.3W  120 KT 140 MPH
 48H  25/1200Z 17.4N 108.9W  115 KT 135 MPH
 72H  26/1200Z 18.0N 111.5W  105 KT 120 MPH
 96H  27/1200Z 19.0N 114.0W   95 KT 110 MPH
120H  28/1200Z 21.0N 115.0W   80 KT  90 MPH
 
$$
FORECASTER LANDSEA/STEWART
 
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