WTNT43 KNHC 121440
TCDAT3
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082007
1100 AM EDT WED SEP 12 2007
 
THE AREA OF LOW PRESSURE EAST OF THE LESSER ANTILLES HAS ACQUIRED
ENOUGH ORGANIZATION TO BE DECLARED A TROPICAL DEPRESSION...THE
EIGHTH OF THE ATLANTIC SEASON.  THE CENTER OF THE ELONGATED
CIRCULATION APPEARS TO BE LOCATED JUST EAST OF THE THUNDERSTORM
ACTIVITY DUE TO SOME EASTERLY SHEAR.  DVORAK T NUMBERS FROM TAFB
AND SAB SUPPORT 30 KT...WHICH WILL BE THE INITIAL INTENSITY.

MICROWAVE AND VISIBLE SATELLITE IMAGERY SUGGESTS THAT THE CYCLONE
HAS BEEN MOVING A LITTLE FASTER DURING THE PAST 6-12 HOURS AND THE
INITIAL MOTION ESTIMATE IS A HIGHLY UNCERTAIN 295/10.  THE
DEPRESSION IS CURRENTLY LOCATED SOUTH OF A NARROW MID-LEVEL RIDGE
AND THE TRACK GUIDANCE SUGGESTS A GENERAL WEST-NORTHWESTWARD HEADING
DURING THE NEXT FEW DAYS.  THE RIDGE IS FORECAST TO WEAKEN IN A DAY
OR SO WHICH SHOULD CAUSE THE DEPRESSION TO DECELERATE AND MOVE
SLOWER THAN CLIMATOLOGY.

THE CURRENT EASTERLY SHEAR IS FORECAST TO WEAKEN DURING THE NEXT DAY
OR SO WHICH SHOULD ALLOW FOR SOME STRENGTHENING.  THUS...CONDITIONS
APPEAR FAVORABLE FOR INTENSIFICATION DURING THE NEXT 2-3 DAYS.
BEYOND 72 HOURS....AN UPPER LEVEL TROUGH LOCATED NORTH AND WEST OF
THE CYCLONE IS EXPECTED TO INDUCE SOUTHWESTERLY SHEAR WHICH SHOULD
HALT ANY ADDITIONAL STRENGTHENING.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/1500Z 13.2N  44.6W    30 KT
 12HR VT     13/0000Z 13.6N  45.9W    35 KT
 24HR VT     13/1200Z 14.0N  47.3W    45 KT
 36HR VT     14/0000Z 14.3N  48.4W    50 KT
 48HR VT     14/1200Z 14.6N  49.5W    55 KT
 72HR VT     15/1200Z 15.1N  51.4W    60 KT
 96HR VT     16/1200Z 16.0N  54.5W    60 KT
120HR VT     17/1200Z 17.0N  57.5W    60 KT
 
$$
FORECASTER BROWN
 

WTNT43 KNHC 122038
TCDAT3
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082007
500 PM EDT WED SEP 12 2007
 
THE CLOUD PATTERN OF THE DEPRESSION HAS CHANGED VERY LITTLE SINCE
THIS MORNING WITH THE CIRCULATION CENTER ESTIMATED NEAR THE EASTERN
PORTION OF THE DEEP CONVECTION.  DVORAK INTENSITY ESTIMATES
FROM TAFB AND SAB SUPPORT 35 KT.  SINCE THERE IS SOME UNCERTAINTY
IN THE EXACT CENTER LOCATION...THE INITIAL INTENSITY WILL REMAIN 30
KT. THE DEPRESSION IS CURRENTLY PASSING ABOUT 60 NM SOUTH OF NOAA
BUOY 41041...WHICH HAS REPORTED A PEAK 1-MINUTE WIND OF 28 KT AND A
MINIMUM PRESSURE OF 1008.6 MB.
 
THE INITIAL MOTION ESTIMATE IS 290/10. THE TRACK GUIDANCE IS IN GOOD
AGREEMENT ON A WEST-NORTHWESTWARD MOTION DURING THE NEXT COUPLE OF
DAYS.  THE RIDGE IS EXPECTED TO WEAKEN AS A MID-TO UPPER-LEVEL LOW
DEVELOPS SEVERAL HUNDRED MILES NORTHEAST OF THE LEEWARD ISLANDS. 
THIS IS EXPECTED TO CAUSE THE DEPRESSION TO DECELERATE DURING THE
NEXT COUPLE OF DAYS.  THE NEW TRACK FORECAST REMAINS CLOSE TO THE
PREVIOUS ADVISORY THROUGH 48 HOURS BUT IS ADJUSTED A LITTLE
NORTHWARD THEREAFTER...IN CLOSE AGREEMENT WITH THE CONSENSUS OF
HWRF...GFDL...UMKET...AND GFS MODELS.
 
MOST OF THE INTENSITY GUIDANCE INDICATES THAT THE EASTERLY SHEAR
CURRENTLY AFFECTING THE CYCLONE SHOULD WEAKEN DURING THE NEXT 24
HOURS AND THE GUIDANCE SUGGESTS THAT DEPRESSION SHOULD GRADUALLY
STRENGTHEN.  THE GFDL...HWRF AND SHIPS MODELS BRING THE DEPRESSION
TO HURRICANE STRENGTH IN ABOUT 72 HOURS. THE OFFICIAL FORECAST WILL
REMAIN SLIGHTLY BELOW THIS GUIDANCE AND KEEP THE DEPRESSION
JUST BELOW HURRICANE STRENGTH.  AT DAYS 4 AND 5...STRONG
SOUTHWESTERLY UPPER-LEVEL WINDS SOUTH OF THE MID-TO UPPER-LEVEL LOW
ARE EXPECTED TO PRODUCE INCREASING SHEAR.  THE GFDL RESPONDS TO THIS
BY WEAKENING THE CYCLONE AND THE OFFICIAL FORECAST WILL REFLECT SOME
WEAKENING LATE IN THE PERIOD.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/2100Z 13.5N  45.5W    30 KT
 12HR VT     13/0600Z 13.9N  46.7W    35 KT
 24HR VT     13/1800Z 14.3N  47.9W    45 KT
 36HR VT     14/0600Z 14.7N  48.8W    50 KT
 48HR VT     14/1800Z 15.1N  49.8W    55 KT
 72HR VT     15/1800Z 16.2N  52.2W    60 KT
 96HR VT     16/1800Z 17.5N  55.5W    60 KT
120HR VT     17/1800Z 18.5N  58.5W    55 KT
 
$$
FORECASTER BROWN
 

WTNT43 KNHC 130259
TCDAT3
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082007
1100 PM EDT WED SEP 12 2007
 
THE DEPRESSION HAS NOT APPRECIABLY CHANGED IN ITS CONVECTIVE
ORGANIZATION OR ESTIMATED INTENSITY SINCE THIS AFTERNOON.  WHILE
DVORAK...ADT...AND AMSU ESTIMATES ARE AT MINIMAL TROPICAL STORM
INTENSITY...SSMI AND SSMIS MICROWAVE IMAGERY SUGGESTS INSTEAD THAT
THE CENTER OF THE SYSTEM IS OFFSET ON THE NORTHEAST SIDE OF THE
CONVECTION.  UPPER TROPOSPHERIC MOTION VECTORS SHOW THAT THERE
REMAINS SOME MODERATE NORTHEASTERLY SHEAR THAT CONTINUES TO IMPACT
THE SYSTEM.  SINCE THE ESTIMATED CENTER IS NOT WELL EMBEDDED WITHIN
THE CONVECTION...THIS INDICATES THAT THE SYSTEM REMAINS A TROPICAL
DEPRESSION AT THIS TIME.

TD EIGHT IS SOUTH OF A WEAK DEEP LAYERED RIDGE WHICH IS CURRENTLY
PROVIDING A STEERING OF ABOUT 280/10...SLIGHTLY MORE WESTWARD THAN
INDICATED IN THE PREVIOUS ADVISORY.  ALL OF THE GLOBAL AND REGIONAL
MODELS SHOW THE CYCLONE SLOWING BETWEEN 24 AND 48 HOURS IN RESPONSE
TO THE INFLUENCE OF AN MID- TO UPPER-LEVEL TROUGH THAT IS CURRENTLY
NORTH OF 25N AT THE SAME LONGITUDE OF THE DEPRESSION.  THE TROUGH
SHOULD CUTOFF AND RETROGRADE WEST-SOUTHWESTWARD.  THIS HAS THE
COMBINED EFFECT OF WEAKENING THE WEST-NORTHWESTWARD STEERING AS
WELL AS INDUCING RATHER STRONG SOUTHWESTERLY SHEAR AT THE LONGER
TIME PERIODS.  THE FORECAST TRACK IS THE CONSENSUS OF THE
GFS...UKMET...GFDL...AND HWRF MODELS AND IS SLIGHTLY SOUTH OF THE
PREVIOUS OFFICIAL FORECAST.  THE ECMWF AND NOGAPS MODELS ARE
DISCOUNTED AS THEY UNREALISTICALLY TAKE THE DEPRESSION NORTHWARD
ALMOST IMMEDIATELY.  

THOUGH THE DEPRESSION IS OVER WARM 28C WATERS...NONE OF THE
INTENSITY GUIDANCE TAKES TD EIGHT TO A HURRICANE IN THE NEXT FIVE
DAYS.  THIS MAY BE DUE TO THE CLOSE PROXIMITY TO RATHER DRY AIR
JUST TO THE NORTH AND WEST OF THE SYSTEM IN THE EARLY TIME PERIODS
AND THE RATHER SHARP INCREASE IN SHEAR AT THE LATER TIME PERIODS. 
THE INTENSITY FORECAST IS CLOSE TO THE SHIPS AND LGE MODELS THROUGH
THREE DAYS AND A BLEND OF THESE TWO WITH THE GFDL AND HWRF MODELS
AT DAYS FOUR AND FIVE.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0300Z 13.4N  46.4W    30 KT
 12HR VT     13/1200Z 13.9N  47.6W    35 KT
 24HR VT     14/0000Z 14.3N  48.6W    40 KT
 36HR VT     14/1200Z 14.6N  49.5W    45 KT
 48HR VT     15/0000Z 15.0N  50.6W    50 KT
 72HR VT     16/0000Z 16.0N  53.5W    55 KT
 96HR VT     17/0000Z 17.0N  56.5W    50 KT
120HR VT     18/0000Z 18.0N  59.0W    45 KT
 
$$
FORECASTER LANDSEA/PASCH
 

WTNT43 KNHC 130844
TCDAT3
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082007
500 AM EDT THU SEP 13 2007
 
SATELLITE IMAGES AND MICROWAVE DATA INDICATE THAT THE CLOUD PATTERN
HAS NOT BECOME ANY BETTER ORGANIZED DURING THE PAST FEW HOURS AND
THE LOW-LEVEL CENTER IS LOCATED TO THE NORTH OF A LARGE CIRCULAR
AREA OF DEEP CONVECTION. INITIAL INTENSITY REMAINS AT 30 KNOTS. THE
DEPRESSION STILL HAS THE OPPORTUNITY TO BECOME A TROPICAL STORM
SINCE THE SHEAR IS EXPECTED TO DECREASE IN THE NEXT DAY OR SO.
THEREAFTER...ALL GLOBAL MODELS FORECAST STRONG UPPER-LEVEL
WESTERLIES OVER THE EASTERN CARIBBEAN AND THE ADJACENT ATLANTIC
WATERS ASSOCIATED WITH A STRONGER THAN NORMAL UPPER-LEVEL TROUGH.
THIS PATTERN IS LIKELY TO INHIBIT THE DEPRESSION FROM
STRENGTHENING SIGNIFICANTLY. WEAKENING IS INDICATED BY THE END OF
THE FORECAST PERIOD AS THE CYCLONE APPROACHES THE AREA WELL TO THE
NORTHEAST OF THE LEEWARD ISLANDS WHERE THE SHEAR IS EXPECTED TO BE
LARGE.
 
THE DEPRESSION IS MOVING TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT
9 KNOTS AROUND A WEAK MID-LEVEL HIGH PRESSURE SYSTEM. SINCE STEERING
CURRENTS ARE FORECAST TO FURTHER WEAKEN...THE DEPRESSION IS
EXPECTED TO DECREASE IN FORWARD SPEED DURING THE NEXT 12 TO 24
HOURS. THE CYCLONE SHOULD THEN CONTINUE ON THIS GENERAL SLOW
WEST-NORTHWEST TRACK THROUGH 5 DAYS.  TRACK GUI DACE IS IN GOOD
AGREEMENT BRINGING THE CYCLONE ON A SLOW WEST-NORTHWEST MOTION AND
WEAKENING. THE UK AND ECMWF MODELS KEEP THE CYCLONE A LITTLE BIT
LONGER BUT THIS IS NOT REALISTIC GIVEN THE ANTICIPATED HIGHLY
UNFAVORABLE UPPER-LEVEL ENVIRONMENT AHEAD OF THE CYCLONE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0900Z 13.9N  47.5W    30 KT
 12HR VT     13/1800Z 14.5N  48.8W    35 KT
 24HR VT     14/0600Z 14.8N  49.6W    40 KT
 36HR VT     14/1800Z 15.0N  50.5W    45 KT
 48HR VT     15/0600Z 15.5N  51.5W    45 KT
 72HR VT     16/0600Z 16.5N  54.0W    45 KT
 96HR VT     17/0600Z 17.5N  57.0W    40 KT
120HR VT     18/0600Z 19.0N  60.0W    35 KT
 
$$
FORECASTER AVILA
 

WTNT43 KNHC 131433
TCDAT3
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082007
1100 AM EDT THU SEP 13 2007
 
A 0900Z QUIKSCAT OVERPASS RECEIVED AFTER THE PREVIOUS ADVISORY
SUGGESTED THAT SYSTEM COULD HAVE BEEN A TROPICAL STORM FOR A FEW
HOURS.  THE IMAGE DEPICTED A FEW UN-FLAGGED 35 KT WINDS JUST TO THE
EAST AND SOUTH OF THE CENTER.  SINCE THEN...VISIBLE IMAGERY
INDICATES A SEVERELY SHEARED...POORLY ORGANIZED SYSTEM. 
CONSEQUENTLY...THE INITIAL INTENSITY WILL BE KEPT AT 30 KT.

DURING THE NEXT 24 HOURS...INTENSITY GUIDANCE SUGGEST THAT THERE IS
STILL A CHANCE THAT THE DEPRESSION WILL DEVELOP INTO A TROPICAL
STORM.  AFTERWARD...THROUGH THE REMAINDER OF THE FORECAST
PERIOD...LARGE SCALE MODELS CONTINUE TO FORECAST STRONG
UPPER-TROPOSPHERIC WESTERLIES...ASSOCIATED WITH A DEEP LAYER
MID-ATLANTIC TROUGH...EXTENDING FROM THE EASTERN CARIBBEAN AND
ADJACENT ATLANTIC WATERS.  THE OFFICIAL INTENSITY FORECAST FOLLOWS
SUIT AND IS SLIGHTLY BELOW THE PREVIOUS PACKAGE.

BASED ON THE AFOREMENTIONED QUIKSCAT PASS AND AN EARLIER SSMIS
MICROWAVE IMAGE...THE TRACK HAS BEEN ADJUSTED SLIGHTLY TO THE LEFT
OF THE PREVIOUS FORECAST...REFLECTING AN INITIAL ESTIMATED MOTION
OF 285/7.  THIS GENERAL MOTION SHOULD CONTINUE THROUGH THE ENTIRE
FORECAST...WITH A CONTINUED SLIGHT REDUCTION IN FORWARD MOTION
DURING THE NEXT 12 TO 24 HOURS.  THE OFFICIAL FORECAST IS BASICALLY
A REFLECTION OF THE PREVIOUS ONE...BUT JUST TO THE LEFT...FOLLOWING
A BLEND OF THE UKMET...GFDL...AND THE GFS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/1500Z 13.9N  48.0W    30 KT
 12HR VT     14/0000Z 14.2N  49.0W    30 KT
 24HR VT     14/1200Z 14.5N  49.9W    35 KT
 36HR VT     15/0000Z 14.8N  50.8W    35 KT
 48HR VT     15/1200Z 15.2N  52.0W    40 KT
 72HR VT     16/1200Z 16.0N  54.4W    40 KT
 96HR VT     17/1200Z 17.0N  57.0W    40 KT
120HR VT     18/1200Z 18.2N  59.6W    35 KT
 
$$
FORECASTER ROBERTS/FRANKLIN
 

WTNT43 KNHC 132035
TCDAT3
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082007
500 PM EDT THU SEP 13 2007
 
CONVENTIONAL SATELLITE IMAGERY INDICATES A SMALLER WEAKER LOW
ROTATING ABOUT A MORE DOMINANT...BROAD...CIRCULATION TO THE
SOUTHEAST.  THE INITIAL POSITION WILL BE BASED ON A CENTROID
POSITION OF THE TWO CIRCULATION CENTERS.  THERE ARE NO CHANGES TO
THE DVORAK SATELLITE INTENSITY ESTIMATES FROM THIS MORNING...AND
THE INITIAL INTENSITY REMAINS AS 30 KT.     

THE OFFICIAL FORECAST INTENSITY REMAINS VIRTUALLY UNCHANGED FROM THE
PREVIOUS FORECAST...SUGGESTING A POSSIBILITY OF STRENGTHENING TO A
TROPICAL STORM DURING THE NEXT 12 HOURS.  AFTERWARD...THE INTENSITY
MODELS INDICATE VERY LITTLE STRENGTHENING THROUGH THE 72 HOUR
PERIOD...WITH A WEAKENING THROUGH THE REMAINDER OF THE PERIOD AS
UPPER LEVEL WESTERLIES ARE EXPECTED TO SPREAD FROM THE EASTERN
CARIBBEAN OVER THE ADJACENT ATLANTIC WATERS.
 
INITIAL MOTION IS ESTIMATED AT 290/5...A LITTLE TO THE RIGHT OF THE
PREVIOUS PACKAGE.  THE CYCLONE SHOULD GRADUALLY CONTINUE ON A
GENERAL WEST-NORTHWESTWARD MOTION WITHIN WEAK STEERING FLOW OF A
MID- TROPOSPHERIC RIDGE TO THE NORTH THROUGH THE FORECAST PERIOD. 
THE DYNAMICAL MODELS ARE IN MORE AGREEMENT THAN THIS MORNING...WITH
THE 12Z ECMWF NOW SUGGESTING A MOTION SIMILAR TO THE OTHER MODELS. 
THE NOGAPS...HOWEVER...SHOWS THE MOST VERTICAL DEPTH WHICH APPEARS
TO BE INFLUENCING A DRAMATIC TURN TO THE RIGHT TOWARD A
RETROGRADING UPPER LEVEL TROUGH SITUATED TO THE NORTHEAST OF THE
DEPRESSION.  THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS
FORECAST...WITH A SLIGHT ADJUSTMENT TO THE RIGHT...AND AGREES WITH
A BLEND OF ALL THE AVAILABLE DYNAMICAL GUIDANCE WITH THE EXCEPTION
OF THE NOGAPS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/2100Z 14.2N  48.4W    30 KT
 12HR VT     14/0600Z 14.5N  49.2W    35 KT
 24HR VT     14/1800Z 15.0N  50.2W    35 KT
 36HR VT     15/0600Z 15.5N  51.4W    35 KT
 48HR VT     15/1800Z 15.9N  52.5W    40 KT
 72HR VT     16/1800Z 17.0N  55.4W    40 KT
 96HR VT     17/1800Z 18.0N  58.0W    35 KT
120HR VT     18/1800Z 19.1N  60.5W    30 KT
 
$$
FORECASTER ROBERTS/BEVEN
 

