[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 281435
TCDAT3

TROPICAL DEPRESSION RINA DISCUSSION NUMBER  22
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL182011
1000 AM CDT FRI OCT 28 2011

STRONG VERTICAL WIND SHEAR...DRY AIR ENTRAINMENT...AND PASSAGE OVER
LAND HAVE TAKEN THEIR TOLL ON RINA. THE LOW-LEVEL CENTER IS EXPOSED
WELL TO THE SOUTH AND SOUTHWEST OF THE REMAINING DISORGANIZED
CONVECTION AND...BASED ON THE SATELLITE APPEARANCE AND OBSERVATIONS
FROM CANCUN MEXICO...APPEARS TO BE MUCH WEAKER THAN 24 HOURS AGO.
IN ADDITION...THE CIRCULATION IS ELONGATED NORTH TO SOUTH...AND A
SECOND LOW-LEVEL VORITICTY MAXIMUM HAS FORMED ABOUT 90 N MI
NORTH-NORTHWEST OF THE CENTER IN RESPONSE TO CONVECTION IN THAT
AREA. IT IS ESTIMATED THAT RINA HAS WEAKENED TO A TROPICAL
DEPRESSION WITH A 30-KT INITIAL INTENSITY.

THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 025/5. RINA IS CURRENTLY
IN AN AREA OF LIGHT LOW-LEVEL SOUTHWESTERLY TO WESTERLY FLOW AHEAD
OF A SOUTHEASTWARD-MOVING COLD FRONT OVER THE NORTHWESTERN GULF OF
MEXICO. HIGH PRESSURE IS FORECAST TO BUILD ACROSS THE GULF OF
MEXICO BEHIND THE FRONT...AND THIS IS EXPECTED TO TURN RINA
SOUTHWARD IN ABOUT 24-36 HOURS AND SOUTH-SOUTHWESTWARD BY 72 HOURS.
THE DYNAMICAL MODELS SHOW A LITTLE MORE EASTWARD MOTION BEFORE THE
SOUTHWARD TURN THAN PREVIOUSLY...SO THE FIRST 48 HOURS OF THE NEW
FORECAST TRACK IS SHIFTED A LITTLE TO THE EAST OF THE PREVIOUS
FORECAST. THE NEW TRACK LIES A LITTLE WEST OF THE VARIOUS CONSENSUS
MODELS THROUGH 48 HOURS AND NEAR THEM AFTER THAT.

THE DYNAMICAL MODELS FORECAST STRONG VERTICAL WIND SHEAR TO CONTINUE
OVER RINA FOR THE NEXT 48-72 HOURS. THUS...THE CYCLONE IS EXPECTED
TO DENEGENERATE INTO A REMNANT LOW IN ABOUT 36 HOURS...AND THIS
COULD OCCUR EARLIER IF ORGANIZED CONVECTION DOES NOT RE-DEVELOP
NEAR THE CENTER. ALL OF THE DYNAMICAL MODELS NOW FORECAST THE
REMNANTS OF RINA TO WEAKEN TO A TROUGH BY 120 HOURS...SO THE NEW
INTENSITY FORECAST CALLS FOR DISSIPATION AT THAT TIME.


FORECAST POSITIONS AND MAX WINDS

INIT  28/1500Z 21.8N  86.6W   30 KT  35 MPH
 12H  29/0000Z 22.1N  86.2W   30 KT  35 MPH
 24H  29/1200Z 22.1N  85.6W   25 KT  30 MPH
 36H  30/0000Z 21.4N  85.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  30/1200Z 20.6N  85.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  31/1200Z 19.5N  86.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  01/1200Z 18.0N  87.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  02/1200Z...DISSIPATED

$$
FORECASTER BEVEN



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