WTNT41 KNHC 312049
TCDAT1
TROPICAL DEPRESSION SIX DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062007
500 PM EDT FRI AUG 31 2007
 
AN AIR FORCE RESERVE HURRICANE HUNTER INVESTIGATING A TROPICAL WAVE
EAST OF THE WINDWARD ISLANDS REPORTED A CLOSED SURFACE CIRCULATION
WITH FLIGHT-LEVEL WINDS UP TO 36 KT. THESE WINDS EQUATE TO ABOUT 30
KT AT THE SURFACE...AND AGREE WELL WITH DVORAK SATELLITE INTENSITY
ESTIMATES FROM TAFB/SAB.  THUS THE SIXTH TROPICAL DEPRESSION OF THE
SEASON IS BORN. THE SATELLITE PRESENTATION IS BECOMING IMPRESSIVE
WITH PLENTY OF CURVED BANDS AND AN EXPANDING OUTFLOW PATTERN.
 
GLOBAL MODELS SUGGEST THAT WIND SHEAR NEAR THE DEPRESSION WILL
REMAIN RELATIVELY LIGHT FOR THE NEXT FEW DAYS.  COUPLED WITH THE
WARM WATERS OF THE CARIBBEAN SEA...THIS WOULD SEEM TO BE A RECIPE
FOR AT LEAST SOME SLOW INTENSIFICATION.  HOWEVER MOST OF THE
LARGE-SCALE MODELS DO NOT STRENGTHEN THE DEPRESSION...AND CLOSE
PROXIMITY TO LAND COULD BE AN INHIBITING FACTOR.  FOR NOW...THE
INTENSITY FORECAST IS A BLEND OF THE SHIPS/GFDL/HWRF MODELS...AND
MAY BE A LITTLE CONSERVATIVE.
 
THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 280/14.  GLOBAL MODELS
KEEP A STRONG RIDGE TO THE NORTH OF THE DEPRESSION FOR THE NEXT
SEVERAL DAYS...WHICH SHOULD STEER THE CYCLONE ON A WEST TO
WEST-NORTHWESTWARD TRACK.  TRACK GUIDANCE IS IN VERY GOOD
AGREEMENT...ESPECIALLY FOR SUCH A WEAK SYSTEM.  THE NHC TRACK
FORECAST IS CLOSE TO THE MODEL CONSENSUS AND NOT TOO FAR FROM THE
ECMWF SOLUTION.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      31/2100Z 11.8N  58.6W    30 KT
 12HR VT     01/0600Z 12.2N  60.8W    35 KT
 24HR VT     01/1800Z 12.9N  64.0W    40 KT
 36HR VT     02/0600Z 13.6N  67.4W    45 KT
 48HR VT     02/1800Z 14.3N  71.1W    50 KT
 72HR VT     03/1800Z 15.3N  78.0W    55 KT
 96HR VT     04/1800Z 16.0N  83.0W    65 KT
120HR VT     05/1800Z 17.0N  88.0W    75 KT
 
$$
FORECASTER BLAKE/AVILA
 

WTNT41 KNHC 010303
TCDAT1
TROPICAL DEPRESSION SIX DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062007
1100 PM EDT FRI AUG 31 2007
 
REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER...MICROWAVE
SATELLITE IMAGERY...AND DATA FROM FRENCH RADAR ON MARTINIQUE
SUGGEST THAT TROPICAL DEPRESSION SIX HAS AN ELONGATED LOW-LEVEL
CIRCULATION...WITH THE CENTER FIXES FROM THE HURRICANE HUNTER IN
THE NORTHERN PART OF THE ELONGATION.  THE AIRCRAFT REPORTED A
CENTRAL PRESSURE OF 1008 MB AND MAXIMUM FLIGHT-LEVEL WINDS OF 42 KT
EAST OF THE CENTER.  THIS DATA ALONG WITH QUIKSCAT DATA AND
SUBSEQUENT SATELLITE INTENSITY ESTIMATES SHOW THAT THE DEPRESSION
IS JUST BELOW TROPICAL STORM STRENGTH...AND IT COULD BECOME A
TROPICAL STORM AT ANY TIME AS IT MOVES THROUGH THE WINDWARD
ISLANDS.

THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 280/13.  THE DEPRESSION
IS CURRENTLY IN A SYNOPTIC PATTERN WHICH IS SIMILAR TO THAT OF
HURRICANE DEAN...ON THE SOUTH SIDE OF A WESTWARD BUILDING
LOW/MID-LEVEL RIDGE.  THIS PATTERN SHOULD PERSIST FOR AT LEAST FOUR
DAYS... CAUSING THE TROPICAL CYCLONE TO MOVE GENERALLY
WEST-NORTHWESTWARD.  THE TRACK GUIDANCE IS TIGHTLY CLUSTERED
THROUGH 36 HR...THEN SOME SPREAD OCCURS.  THE HWRF AND THE SHALLOW
AND MEDIUM MEAN LAYER BAM MODELS FORECAST A MORE NORTHWARD MOTION
TO A 120 HR POSITION NEAR THE YUCATAN CHANNEL...WHILE THE REMAINDER
OF THE GUIDANCE TAKES THE CYCLONE TO BELIZE AND THE SOUTHERN
YUCATAN PENINSULA.  THE HWRF SHOWS THE STORM DISSIPATING DURING THE
FORECAST PERIOD...WHICH MAY ACCOUNT FOR ITS MORE NORTHWARD FORECAST
TRACK.  THE TRACK FORECAST IS DOWN THE MIDDLE OF THE REMAINDER OF
THE GUIDANCE AND IS SIMILAR TO THE PREVIOUS FORECAST.

THE LARGE-SCALE MODELS FORECAST THE CYCLONE TO BE IN DEEP-LAYER
EASTERLY FLOW ON THE SOUTH SIDE OF AN UPPER-LEVEL ANTICYCLONE FOR
THE NEXT 5 DAYS...WHICH SHOULD ALLOW SIGNIFICANT STRENGTHENING ONCE
THE SYSTEM CONSOLIDATES.  THE SHIPS MODEL AND THE EXPERIMENTAL LGEM
MODEL BOTH FORECAST A MAJOR HURRICANE IN ABOUT 5 DAYS.  ON THE
OTHER HAND...AS NOTED ABOVE THE HWRF DISSIPATES THE SYSTEM...WHILE
THE GFDL WAITS UNTIL IT IS WEST OF 75W TO FORECAST SIGNIFICANT
STRENGTHENING.  GIVEN THE GOOD OUTFLOW ALOFT AND THE FORECAST
UPPER-LEVEL WINDS...THE INTENSITY FORECAST CALLS FOR STEADY
STRENGTHENING THROUGH THE FORECAST PERIOD.  THERE IS A CHANCE THAT
THE CYCLONE COULD BE STRONGER THAN CURRENTLY FORECAST IF THE
STATISTICAL MODELS ARE CORRECT.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/0300Z 12.0N  59.9W    30 KT
 12HR VT     01/1200Z 12.5N  62.2W    35 KT
 24HR VT     02/0000Z 13.2N  65.5W    40 KT
 36HR VT     02/1200Z 14.0N  69.0W    50 KT
 48HR VT     03/0000Z 14.6N  72.6W    55 KT
 72HR VT     04/0000Z 15.5N  79.0W    60 KT
 96HR VT     05/0000Z 16.5N  84.0W    70 KT
120HR VT     06/0000Z 17.5N  88.5W    80 KT...INLAND
 
$$
FORECASTER BEVEN
 

