Tropical Depression SIX

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TROPICAL DEPRESSION SIX DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062006
1100 PM EDT SUN SEP 03 2006

THERE HAS BEEN ONLY A SLIGHT INCREASE IN THE APPARENT ORGANIZATION
OF THE SYSTEM.  BANDING FEATURES NEAR THE ESTIMATED CENTER ARE A
LITTLE BETTER DEFINED...HOWEVER THE HIGH CLOUDS ARE BECOMING A
LITTLE MORE ELONGATED TO THE NORTH AND UPPER-LEVEL OUTFLOW IS NOT
WELL-ESTABLISHED OVER THE SOUTHWEST PART OF THE CYCLONE.  DVORAK
INTENSITY ESTIMATES ARE 30 KT...30 KT...AND 35 KT FROM
TAFB...AFWA...AND SAB RESPECTIVELY.  BECAUSE THE UNCERTAINTY IN
CENTER LOCATION LEADS TO UNCERTAINTY IN SATELLITE-BASED INTENSITY
ESTIMATION...THE WIND SPEED IS HELD AT 30 KT FOR THIS ADVISORY. 
SOME SOUTHWESTERLY SHEAR...ASSOCIATED WITH AN UPPER-TROPOSPHERIC
TROUGH TO THE NORTHWEST OF THE DEPRESSION...COULD INHIBIT
STRENGTHENING DURING THE NEXT COUPLE OF DAYS.  HOWEVER THIS SHEAR
IS NOT EXPECTED TO BECOME PROHIBITIVELY STRONG SO A GRADUAL
INCREASE IN INTENSITY IS FORECAST.  LATER IN THE FORECAST
PERIOD...THE UPPER-LEVEL ENVIRONMENT IS PREDICTED TO BECOME MORE
CONDUCIVE FOR STRENGTHENING.  THE OFFICIAL INTENSITY FORECAST IS
VERY SIMILAR TO THE SHIPS GUIDANCE IN THE LATTER PART OF THE
PERIOD...BUT BELOW THE 1800 UTC GFDL GUIDANCE IN 4-5 DAYS.  WE
BELIEVE THAT THIS PARTICULAR RUN OF THE GFDL MODEL HAD A HIGH
INTENSITY BIAS DUE TO PROBLEMS WITH THE OCEAN COUPLING.

IT IS QUITE DIFFICULT TO LOCATE THE LOW-LEVEL CENTER AT THIS TIME
BUT THE LATEST FIXES ARE ALL TO THE EAST OF PREVIOUS POSITION
ESTIMATES.  THEREFORE THE BEST TRACK HAS BEEN ADJUSTED A LITTLE TO
THE RIGHT AND WITH A SLOWER FORWARD SPEED.  MY INITIAL MOTION
ESTIMATE IS AN UNCERTAIN 310/10.  A WEAKNESS IN THE MID-LEVEL RIDGE
NEAR 50W LONGITUDE SHOULD ALLOW THE CURRENT NORTHWESTWARD MOTION TO
MORE OR LESS CONTINUE FOR THE NEXT DAY OR SO.  THEREAFTER...THE
GLOBAL MODELS SHOW A RIDGE BUILDING EASTWARD TO THE NORTH OF THE
TROPICAL CYCLONE.  THIS CHANGE IN THE STEERING PATTERN WOULD CAUSE
THE TRACK TO BEND TOWARD THE LEFT IN 3-5 DAYS.  THE OFFICIAL TRACK
FORECAST IS CLOSE TO THE DYNAMICAL MODEL CONSENSUS AND ONLY
SLIGHTLY TO THE LEFT OF THAT FROM THE PREVIOUS ADVISORY.  IT SHOULD
BE RECALLED THAT TRACK FORECAST ERRORS CAN BE SEVERAL HUNDRED MILES
IN THE 5-DAY TIME FRAME.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      04/0300Z 14.8N  40.4W    30 KT
 12HR VT     04/1200Z 15.9N  42.0W    35 KT
 24HR VT     05/0000Z 17.0N  43.8W    40 KT
 36HR VT     05/1200Z 18.0N  45.5W    45 KT
 48HR VT     06/0000Z 18.9N  47.3W    50 KT
 72HR VT     07/0000Z 20.5N  51.5W    55 KT
 96HR VT     08/0000Z 21.5N  56.0W    65 KT
120HR VT     09/0000Z 22.5N  61.0W    75 KT
 
$$
FORECASTER PASCH
 
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