[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 050231
TCDAT4
TROPICAL DEPRESSION NINE DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT THU AUG 04 2005

THE CENTER OF TROPICAL DEPRESSION NINE IS A LITTLE DIFFICULT TO
LOCATE THIS EVENING.  AN SSM/I OVERPASS AT 2245Z AND SHORTWAVE IR
IMAGERY FROM METEOSAT-8 SUGGEST THAT THE CYCLONE CENTER IS
ELONGATED NORTH-NORTHEAST TO SOUTH-SOUTHWEST...WITH SATELLITE FIXES
FROM TAFB AND SAB FALLING NEAR THE SOUTH-SOUTHWEST END.  IT IS
POSSIBLE THAT THE MEAN CENTER IS TO THE NORTH AND EAST OF THE
ADVISORY POSITION.  OVERPASSES FROM THE TRMM AND AQUA SATELLITES
LATER TONIGHT MAY HELP RESOLVE THE ISSUE.  DEEP CONVECTION IS
CURRENTLY SOMEWHAT DISORGANIZED...SO THE INITIAL INTENSITY REMAINS
25 KT IN AGREEMENT WITH SATELLITE INTENSITY ESTIMATES.

THE INITIAL MOTION IS AN SOMEWHAT UNCERTAIN 280/11.  THE DEPRESSION
IS ON THE SOUTH SIDE OF A DEEP-LAYER RIDGE.  LARGE-SCALE MODELS
FORECAST THIS SHOULD BE THE CASE FOR THE NEXT 3 DAYS...WHICH SHOULD
PRODUCE A GENERAL WESTWARD TO WEST-NORTHWESTWARD MOTION.  AFTER
THAT...THE CYCLONE COULD BE APPROACHING A WEAKNESS IN THE RIDGE IN
THE MID-ATLANTIC...WHICH WOULD ALLOW A MORE NORTHERLY MOTION.  THE
OFFICIAL FORECAST TRACK FOLLLOWS THIS SCENARIO AND IS AN UPDATE OF
THE PREVIOUS FORECAST.  IT SHOULD BE NOTED THAT THE 18Z GFS MODEL
DID NOT APPEAR TO INITIALIZE THE CYCLONE WELL...WHILE THE 18Z
NOGAPS MODEL DISSIPATED THE SYSTEM IN LESS THAN 72 HR.

LARGE-SCALE MODELS FORECAST LIGHT VERTICAL SHEAR ALONG THE FORECAST
TRACK DURING THE NEXT FIVE DAYS.  THUS...THE BIGGEST CONTROL ON THE
INTENSITY SHOULD BE SEA SURFACE TEMPERATURES.  THE CENTER OF THE
CYCLONE IS CURRENTLY OVER 27C WATER...WHILE REPORTS IN THE
NORTHEASTERN PART OF THE CIRCULATION SHOW 26C WATER.  COMBINE THIS
WITH THE BROAD CIRCULATION AND THE INITIAL INTENSIFICATION SHOULD
SOMEWHAT SLOW...PERHAPS EVEN SLOWER THAN CURRENTLY FORECAST.  THE
FORECAST TRACK BRINGS THE SYSTEM TO 28C WATER BY 72 HR...WHICH
COULD ALLOW MORE STRENGTHENING THAN CURRENTLY FORECAST.  HOWEVER...
ANY MOTION TO THE RIGHT OF THE TRACK WOULD DELAY THE ARRIVAL OVER
WARMER WATER AND SLOW INTENSIFICATION.  THE INTENSITY FORECAST
COMPROMISES BETWEEN THESE EXTREMES AND IS SIMILAR TO...BUT STRONGER
THAN...THE SHIPS MODEL.

THE WIND RADII FORECAST AT 72 HR HAS BEEN REVISED BASED ON
CLIMATOLOGY AND THE BROAD CYCLONIC ENVELOPE OF THE DEPRESSION.

FORECASTER BEVEN


FORECAST POSITIONS AND MAX WINDS

INITIAL      05/0300Z 13.0N  35.2W    25 KT
 12HR VT     05/1200Z 13.3N  36.8W    30 KT
 24HR VT     06/0000Z 13.7N  38.9W    40 KT
 36HR VT     06/1200Z 14.3N  41.1W    45 KT
 48HR VT     07/0000Z 14.9N  43.2W    55 KT
 72HR VT     08/0000Z 16.5N  47.0W    65 KT
 96HR VT     09/0000Z 18.5N  50.5W    75 KT
120HR VT     10/0000Z 20.5N  54.0W    75 KT


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