Hurricane CALVIN

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HURRICANE CALVIN DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP032011
800 PM PDT FRI JUL 08 2011
 
RECENT CONVENTIONAL AND EARLIER MICROWAVE SATELLITE DATA SUGGEST
THAT THE LOW-LEVEL AND MID-/UPPER-LEVEL EYE FEATURES MAY HAVE
FINALLY BECOME VERTICALLY ALIGNED. IN ADDITION...A WARM SPOT HAS
DEVELOPED NEARLY IN THE CENTER OF THE SMALLER BUT BETTER-DEFINED
CDO CLOUD PATTERN...SUGGESTING THE PRESENCE OF A MORE VERTICAL EYE
STRUCTURE. SATELLITE INTENSITY ESTIMATES ARE 77 KT AND 65 KT FROM
TAFB AND SAB...RESPECTIVELY. GIVEN THE IMPROVEMENT IN THE OVERALL
CLOUD PATTERN...THE INITIAL INTENSITY HAS BEEN BUMPED UP TO 70 KT.

THE INITIAL MOTION IS 285/10...BUT THIS IS LIKELY JUST A TEMPORARY
MOTION. CALVIN HAS WOBBLED TO THE RIGHT A LITTLE BIT...PROBABLY AS
A RESULT OF THE LOW-LEVEL AND MID-LEVEL EYES BECOMING VERTICALLY
ALIGNED. AS A RESULT...CALVIN IS FORECAST TO RETURN TO A MORE
WESTERLY BASE COURSE WITHIN THE NEXT 12 HOURS OR SO DUE TO THE
STRONG SUBTROPICAL RIDGE SITUATED TO THE NORTH OF THE CYCLONE. THE
AFOREMENTIONED RIDGE IS EXPECTED TO CHANGE LITTLE THROUGH THE
FORECAST PERIOD...WHICH SHOULD ACT TO KEEP CALVIN MOVING IN A
WESTWARD TO WEST-NORTHWESTWARD DIRECTION. BY 48 HOURS...THE CYCLONE
IS FORECAST TO BEGIN DEGENERATING INTO A REMNANT LOW PRESSURE
SYSTEM AS IT MOVES OVER SUB-24C SSTS. AS THE SYSTEM BECOMES
VERTICALLY SHALLOW...IT IS EXPECTED TO SLOW DOWN CONSIDERABLY AS IT
MOVES INTO A REGION OF ABNORMALLY WEAK LOW-LEVEL TRADE WIND FLOW.
THE FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND IS NEAR
THE CONSENSUS OF THE GLOBAL MODELS.

UPPER-LEVEL OUTFLOW HAS IMPROVED AND EXPANDED IN ALL QUADRANTS...
SUGGESTING THAT THE VERTICAL SHEAR HAS ABATED SOMEWHAT.
THEREFORE...SOME SLIGHT STRENGTHENING IS POSSIBLE DURING THE NEXT 6
HOURS OR SO SINCE CALVIN WILL STILL BE OVER AT LEAST 26C SSTS.
HOWEVER...BY 12 HOURS THE CYCLONE WILL BE MOVING OVER MUCH COOLER
WATER AND ALSO BEGIN INGESTING MORE STABLE AIR AS INDICATED BY A
LARGE FIELD OF LOW-LEVEL STRATOCUMULUS CLOUDS LOCATED JUST WEST OF
CALVIN. AS A RESULT OF THE POOR OCEANIC AND THERMODYNAMIC
CONDITIONS AHEAD OF THE HURRICANE...STEADY WEAKENING IS FORECAST
AND AT A FASTER RATE THAN INDICATED BY THE SHIPS AND LGEM
STATISTICAL INTENSITY MODELS.

FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0300Z 16.6N 109.5W   70 KT  80 MPH
 12H  09/1200Z 17.0N 111.0W   60 KT  70 MPH
 24H  10/0000Z 17.5N 112.6W   50 KT  60 MPH
 36H  10/1200Z 17.9N 113.9W   40 KT  45 MPH
 48H  11/0000Z 18.4N 115.1W   30 KT  35 MPH
 72H  12/0000Z 19.3N 117.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  13/0000Z 19.5N 118.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  14/0000Z...DISSIPATED
 
$$
FORECASTER STEWART
 
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