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Hurricane DANIEL


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HURRICANE DANIEL DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP052006
200 AM PDT SUN JUL 23 2006
 
INFRARED SATELLITE IMAGERY SHOWS THAT CLOUD TOP TEMPERATURES OVER
THE WESTERN SEMICIRCLE CONTINUE TO GRADUALLY WARM AND THE OVERALL
CONVECTIVE PATTERN HAS BECOME ASYMMETRIC ABOUT THE EYE. IT WOULD
APPEAR THAT DANIEL IS BEGINNING TO FEEL THE INFLUENCE OF COOLER
WATERS. THE INITIAL INTENSITY IS LOWERED TO 115 KT WHICH IS A
COMPROMISE BETWEEN 102 KT FROM SAB AND 127 KT FROM TAFB.  THREE-
HOUR AVERAGE ADT VALUES HAVE ALSO BEEN STEADY AT 115 KT.  BEING AT
OR VERY NEAR THE 26C ISOTHERM...DANIEL IS EXPECTED TO CONTINUE
WEAKENING THROUGH THE FORECAST PERIOD.  MODERATE VERTICAL SHEAR MAY
ALSO BEGIN CONTRIBUTING TO THE WEAKENING IN THE 36-48 HOUR TIME
FRAME. STILL...DANIEL DISPLAYS CHARACTERISTICS OF AN ANNULAR
HURRICANE AND THE OFFICIAL FORECAST SHOWS WEAKENING AT A SLOWER
RATE THAN USUAL GIVEN THE AFOREMENTIONED ENVIRONMENTAL CONDITIONS.
THIS FORECAST IS ALSO HIGHER THAN THE SHIPS MODEL...WHICH STUDIES
HAVE SHOWN WEAKENS CYCLONES TOO QUICKLY IN THESE SITUATIONS.
 
DANIEL IS CURRENTLY BEING STEERED BY A STRONG MID-TO-UPPER
TROPOSPHERIC RIDGE TO ITS NORTH RESULTING IN A WEST TO
WEST-NORTHWESTWARD MOTION OR 280/12. THIS OVERALL MOTION IS
EXPECTED TO CONTINUE FOR THE NEXT 12-24 HOURS.  THEREAFTER...MOST
OF THE DYNAMICAL MODELS INDICATE A PRONOUNCED WEAKNESS DEVELOPING
WITHIN THE RIDGE BETWEEN 135W-140W. THIS EVOLUTION IS EXPECTED TO
RESULT IN A REDUCTION IN FORWARD SPEED AS THE CYCLONE MOVES INTO
THE WEAKNESS.  AS WOULD BE EXPECTED IN LIGHT STEERING FLOW
CONDITIONS...DYNAMICAL MODELS BEGIN TO DIVERGE WITH THE GFS AND GFS
ENSEMBLE MEAN SHOWING DANIEL BECOMING...TEMPORARILY..NEARLY
STATIONARY AT 48 HOURS WHILE THE UKMET KEEPS THE CYCLONE MOVING
ALONG AT A STEADY CLIP.  THE OFFICIAL FORECAST SPLITS THE
DIFFERENCE BETWEEN THESE TWO SCENARIOS BY SHOWING DANIEL SLOWING AS
IT MOVES INTO THE WEAKNESS WITHIN THE RIDGE BETWEEN 36 AND 48
HOURS. AS DANIEL BECOMES INCREASINGLY SHALLOW DURING THE LATER
PARTS OF THE FORECAST...THE STEERING IS EXPECTED TO BECOME
DOMINATED BY THE LOW LEVEL EASTERLIES WHICH SHOULD ALLOW THE
CYCLONE TO SPEED UP AGAIN AND TURN MORE TOWARDS THE WEST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0900Z 14.7N 134.6W   115 KT
 12HR VT     23/1800Z 15.0N 135.9W   100 KT
 24HR VT     24/0600Z 15.6N 137.7W    90 KT
 36HR VT     24/1800Z 16.0N 139.2W    80 KT
 48HR VT     25/0600Z 16.4N 140.2W    70 KT
 72HR VT     26/0600Z 17.2N 142.0W    60 KT
 96HR VT     27/0600Z 18.5N 145.0W    50 KT
120HR VT     28/0600Z 20.0N 150.0W    40 KT
 
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FORECASTER RHOME
 
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