[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 230858
TCDAT5

TROPICAL DEPRESSION TEN DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL102012
500 AM AST THU AUG 23 2012

DEEP CONVECTION WITH THE TROPICAL DEPRESSION CONTINUES TO BE
SPORADIC THOUGH WITH QUITE COLD CLOUD TOPS.  THE CENTER APPEARS TO
BE NEAR THE SOUTH SIDE OF THE CONVECTION SUGGESTING THAT THE
MODERATE SOUTHERLY VERTICAL SHEAR IS INHIBITING ITS DEVELOPMENT.
AS A RESULT OF THE LACK OF IMPROVEMENT OF THE ORGANIZATION OF THE
DEEP CONVECTION...THE DVORAK CLASSIFICATIONS FROM TAFB AND SAB
REMAIN AT A 2.0...OR ABOUT 30 KT.  IN CONTRAST...TWO RECENT AMSU
SATELLITE PASSES SUGGEST THAT THE CYCLONE MAY BE A 35 TO 45 KT
TROPICAL STORM.  GIVEN THE UNIMPRESSIVE CONVECTIVE STRUCTURE...THE
SYSTEM REMAINS AS A 30-KT TROPICAL DEPRESSION.

A 0406Z AMSU IMAGE FROM THE NRL WEBSITE PROVIDES MODERATE CONFIDENCE
IN THE INITIAL POSITION OF THE TROPICAL DEPRESSION.  THE CURRENT
MOTION OF THE SYSTEM CONTINUES TOWARD THE WEST-NORTHWEST...295
DEGREES...AT 14 KT...AS THE CYCLONE IS BEING ADVECTED AROUND THE
SOUTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE.  THE SYSTEM
SHOULD GRADUALLY TURN TOWARD THE NORTH-NORTHWEST BY DAY FIVE AS IT
REACHES THE WESTERN SIDE OF THE RIDGE.  THE GLOBAL AND REGIONAL
TRACK GUIDANCE SHOWS RELATIVELY TIGHT CLUSTERING AND HAD LITTLE
CHANGE FROM THE PREVIOUS MODEL CYCLE.  THUS THE TRACK FORECAST IS
NEARLY IDENTICAL TO BOTH THE LAST ADVISORY AND THE HFIP TV15
CONSENSUS.

THE INTENSITY PREDICTION IS MORE PROBLEMATIC THAN THE TRACK
FORECAST.  THE AFOREMENTIONED MODERATE VERTICAL SHEAR IS PRIMARILY
BEING INDUCED BY AN UPPER LOW LOCATED ABOUT 600 NM NORTHWEST OF THE
CYCLONE.  THE TROPICAL DEPRESSION AND THE UPPER LOW SHOULD GET
CLOSER TOGETHER OVER THE NEXT THREE DAYS...WHICH WOULD CONTINUE
MODERATE SHEAR ACROSS THE CYCLONE.  ON DAYS FOUR AND FIVE...THE
VERTICAL SHEAR MAY INCREASE DUE TO THE OUTFLOW OF ISAAC.
MOREOVER...THE THERMODYNAMICS ARE NOT CONDUCIVE FOR MUCH
INTENSIFICATION AS SOME DRY STABLE AIR ASSOCIATED WITH A SAHARAN
AIR LAYER...WORKING IN CONCERT WITH THE VERTICAL SHEAR...MAY BE
REACHING THE INNER CORE OF THE CYCLONE DURING THE NEXT TWO TO THREE
DAYS.  THUS ONLY VERY GRADUAL INTENSIFICATION IS SHOWN THROUGHOUT
THE FORECAST PERIOD IN BEST AGREEMENT WITH HWRF AND SHIPS MODELS.
THE PREDICTED INTENSITIES ARE REDUCED SLIGHTLY FROM THE PREVIOUS
ADVISORY. AN ALTERNATIVE SCENARIO DEPICTED BY THE ECMWF AND GFDL
MODELS IS THAT THE CYCLONE COULD SUCCOMB TO THE HOSTILE ENVIRONMENT
AND DISSIPATE BEFORE THE END OF THE FORECAST PERIOD.

FORECAST POSITIONS AND MAX WINDS

INIT  23/0900Z 14.5N  40.6W   30 KT  35 MPH
 12H  23/1800Z 15.2N  42.5W   35 KT  40 MPH
 24H  24/0600Z 16.2N  45.0W   35 KT  40 MPH
 36H  24/1800Z 17.4N  47.7W   35 KT  40 MPH
 48H  25/0600Z 18.8N  50.8W   35 KT  40 MPH
 72H  26/0600Z 22.0N  57.0W   40 KT  45 MPH
 96H  27/0600Z 27.0N  63.0W   45 KT  50 MPH
120H  28/0600Z 31.0N  64.5W   45 KT  50 MPH

$$
FORECASTER LANDSEA



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