Hurricane RICK

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HURRICANE RICK DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP202009
800 PM PDT SUN OCT 18 2009
 
DRY AIR AND SOUTHWESTERLY SHEAR...LOCATED BENEATH THE CIRRUS OUTFLOW
LAYER...HAVE CONTINUED TO ERODE THE DEEP CONVECTION ON THE WESTERN
SIDE OF THE HURRICANE.  THE EYE REMAINS DISTINCT IN INFRARED
IMAGERY...AND A 2101 AMSR-E MICROWAVE PASS SUGGESTED THAT THE
HURRICANE HAD A PARTIAL CONCENTRIC EYEWALL STRUCTURE.  THE
DEGRADATION OF THE CLOUD PATTERN HAS RESULTED IN DVORAK FINAL-T AND
CI NUMBERS OF 6.5/7.0 FROM TAFB AND 6.0/7.0 FROM SAB.  IN
ADDITION...THE OBJECTIVE ESTIMATE FROM UW-CIMSS IS NOW 6.1/6.7...
AND THE ADVISORY INTENSITY IS SET AT 125 KT.
 
RICK IS TURNING NORTHWESTWARD WITH AN INITIAL MOTION OF 305 DEGREES
AT 11 KT NOW THAT THE SUBTROPICAL RIDGE TO ITS NORTH HAS BEGUN TO
WEAKEN.  THE RIDGE IS EXPECTED TO CONTINUE TO BREAK DOWN AS A
SHORTWAVE TROUGH LOCATED WEST OF NORTHERN CALIFORNIA MOVES EAST AND
AMPLIFIES OVER THE WESTERN UNITED STATES OVER THE NEXT 48 HOURS.
AS A RESULT...THE EVOLVING STEERING FLOW WILL TURN RICK TOWARD THE
NORTH AND NORTH-NORTHEAST OVER THE NEXT COUPLE OF DAYS.  ONLY THE
UKMET CONTINUES TO SHOW A WESTWARD MOTION DURING THAT TIME...AND A
CONSENSUS OF THE OTHER DYNAMICAL MODELS SUGGESTS THAT RICK WILL
ACCELERATE TOWARD THE NORTHEAST BY DAY 3.  THE NEW NHC FORECAST IS
VERY CLOSE TO THAT CONSENSUS AND NOT VERY DIFFERENT FROM THE
PREVIOUS FORECAST.
 
ADDITIONAL WEAKENING IS EXPECTED OVER THE NEXT FEW DAYS DUE TO
INCREASING VERTICAL SHEAR AND INGESTION OF DRY AND MORE STABLE AIR
LOCATED TO THE WEST OF THE HURRICANE.  THE NEW OFFICIAL FORECAST IS
A LITTLE FASTER IN WEAKENING RICK THAN WAS SHOWN IN PREVIOUS
FORECASTS...BUT THIS IS MAINLY DUE TO THE FACT THAT THE INITIAL
INTENSITY IS ALREADY LOWER THAN EXPECTED.  MOST IMPORTANTLY...RICK
IS STILL EXPECTED TO BE A SIGNIFICANT HURRICANE AS IT MOVES NEAR
THE SOUTHERN TIP OF BAJA CALIFORNIA AND INTO NORTHWESTERN MEXICO IN
2 TO 3 DAYS.  A 96-HOUR POSITION IS SHOWN TO MAINTAIN CONTINUITY IN
THE INTENSITY FORECAST...BUT IT IS DOUBTFUL THAT A WELL-DEFINED
SURFACE CENTER WILL EXIST AT THAT TIME.
 
A HURRICANE WATCH MAY BE REQUIRED FOR PORTIONS OF SOUTHERN BAJA
EARLY MONDAY.  INTERESTS THROUGHOUT SOUTHERN BAJA AND ALONG THE
WEST-CENTRAL COAST OF MAINLAND MEXICO SHOULD CLOSELY MONITOR THE
PROGRESS OF RICK.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/0300Z 17.0N 110.3W   125 KT
 12HR VT     19/1200Z 17.9N 111.2W   115 KT
 24HR VT     20/0000Z 19.0N 111.8W   105 KT
 36HR VT     20/1200Z 20.2N 111.6W    95 KT
 48HR VT     21/0000Z 21.7N 110.6W    85 KT
 72HR VT     22/0000Z 25.0N 107.5W    70 KT...INLAND
 96HR VT     23/0000Z 26.5N 106.0W    30 KT...INLAND
120HR VT     24/0000Z...DISSIPATED
 
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FORECASTER BERG
 
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