Hurricane DARBY

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HURRICANE DARBY DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 AM PDT THU JUL 29 2004
 
DARBY HAS BEEN AN AMAZING HURRICANE BY RAPIDLY INTENSIFYING FOR THE
PAST 54 HOURS BY INCREASING FROM 35 KT TO 105 KT...WITH THE LAST 
12 HOURS OF RAPID INTENSIFICATION HAVING OCCURRED OVER SUB-27C
SSTS. THE INITIAL INTENSITY OF 105 KT IS BASED ON A SOLID DVORAK
SATELLITE INTENSITY ESTIMATE OF T6.0...OR 115 KT...FROM BOTH TAFB
AND SAB AND A 29/0229Z AMSU PRESSURE ESTIMATE OF 959 MB. ONLY 90
PERCENT OF THE 115 KT SATELLITE INTENSITY ESTIMATE IS BEING USED
SINCE DARBY IS OVER 26C WATER. I FEEL THAT COMPLETE DOWNWARD MIXING
OF THE STRONG WINDS TO THE SURFACE IS NOT OCCURRING DUE TO THE
COOLER AND MORE STABLE BOUNDARY LAYER. HOWEVER...THIS STILL MAKES
DARBY THE FIRST NORTHEAST PACIFIC MAJOR HURRICANE SINCE KENNA BACK
IN OCTOBER 2002.
 
THE INITIAL MOTION IS 295/12. SATELLITE FIX POSITIONS HAVE BEEN
COMING IN ON TRACK SO THERE REMAINS NO SIGNIFICANT CHANGE TO THE
PREVIOUS FORECAST TRACK AND REASONING. THE STRONG RIDGE TO THE
NORTH SHOULD KEEP DARBY MOVING ALONG ON A WEST-NORTHWEST TRACK...
WITH A GRADUAL TURN TO THE WEST BY 48-72 HOURS AS THE SYSTEM
RAPIDLY WEAKENS AND IS STEERED MORE BY THE EASTERLY LOW-LEVEL TRADE
WIND FLOW. THE OFFICIAL FORECAST TRACK IS JUST AN EXTENSION OF THE
PREVIOUS TRACK AND IS BETWEEN THE GUNS AND GUNA CONSENSUS MODELS.

DARBY WILL BE MOVING OVER SUB-25C SSTS IN ABOUT 12 HOURS AND OVER
SUB-24C WATER BY 36 HOURS...SO RAPID WEAKENING IS FORECAST TO
COMMENCE SHORTLY. THE INTENSITY FORECAST IS CLOSE TO THE SHIPS
INTENSITY MODEL...EXCEPT THE SHIPS MODEL COMPLETELY DISSIPATES THE
CYCLONE BY 84 HOURS.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/0900Z 17.0N 126.8W   105 KT
 12HR VT     29/1800Z 17.6N 128.4W    95 KT
 24HR VT     30/0600Z 18.3N 130.6W    75 KT
 36HR VT     30/1800Z 18.8N 132.8W    60 KT
 48HR VT     31/0600Z 19.1N 135.1W    45 KT
 72HR VT     01/0600Z 19.5N 140.0W    30 KT...DISSIPATING
 96HR VT     02/0600Z 20.0N 145.0W    25 KT...REMNANT LOW
120HR VT     03/0600Z 20.0N 150.5W    25 KT...REMNANT LOW
 
 
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