WTNT44 KNHC 012042
TCDAT4
TROPICAL STORM GASTON DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092010
500 PM AST WED SEP 01 2010
 
THUNDERSTORMS HAVE CONSOLIDATED NEAR THE CENTER OF THE CYCLONE THIS
AFTERNOON...WITH AN INTENSE CONVECTIVE BAND IN THE WESTERN
SEMICIRCLE. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE 45
KT AND 30 KT...RESPECTIVELY...WITH AMSU ESTIMATES FROM CIRA AND CSU
INDICATING 50 KT AND 37 KT. OVERALL THIS SYSTEM APPEARS BETTER
ORGANIZED THAN SIX HOURS AGO...AND A BLEND OF THESE DATA GIVES AN
INITIAL INTENSITY OF 35 KT...MAKING GASTON THE SEVENTH NAMED STORM
OF THE ATLANTIC HURRICANE SEASON.

THERE IS STILL A SIGNIFICANT AMOUNT OF DRY AIR TO THE WEST AND NORTH
OF THE TROPICAL STORM...WHICH MAY HINDER STRENGTHENING.  HOWEVER...
ALL OF THE GLOBAL MODELS SHOW THAT A RELATIVELY LIGHT SHEAR
ENVIRONMENT WILL BE PRESENT NEAR GASTON FOR THE NEXT SEVERAL DAYS. 
THE GUIDANCE NOW INDICATES CONSIDERABLY MORE INTENSIFICATION OF
GASTON...WITH THE NORMALLY CONSERVATIVE LGEM SHOWING THIS SYSTEM
BECOMING A MAJOR HURRICANE BY THE END OF THE PERIOD.  THE NHC
FORECAST IS RAISED FROM THE PREVIOUS ONE...BUT REMAINS LOWER THAN
THE MODEL CONSENSUS.  

AN AMSR-E PASS AT 1613 UTC HELPED WITH THE INITIAL POSITION AND
MOTION...WHICH IS A BIT SLOWER THAN BEFORE AT 280/13. A SUBTROPICAL
RIDGE TO THE NORTH OF GASTON IS FORECAST TO WEAKEN SOON AS A
MID-LATITUDE TROUGH PASSES BY...WHICH WOULD CAUSE THE STORM TO SLOW
DOWN. THIS RIDGE SHOULD REBUILD IN A FEW DAYS AND STEER THE
TROPICAL STORM AT AN INCREASINGLY FASTER RATE TO THE WEST OR WEST-
NORTHWEST. GLOBAL MODELS HAVE COME INTO SOMEWHAT BETTER AGREEMENT
NOW THAT MOST OF THEM ARE INITIALIZING THE STORM...BUT THERE ARE
STILL SOME SIGNIFICANT SPEED DIFFERENCES. THE NHC FORECAST IS
FASTER THAN ALL OF THE GUIDANCE IN THE SHORT TERM AS IT SEEMS LIKE
THE MODELS ARE GENERALLY SHOWING TOO MUCH INTERACTION BETWEEN THE
ITCZ AND GASTON. THE NEW FORECAST DOES END UP CLOSE TO THE PREVIOUS
ONE BY DAY 5...AND IS NEAR A BLEND OF THE GFS/UKMET/HWRF/GFDL
MODELS. 
 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/2100Z 12.9N  37.0W    35 KT
 12HR VT     02/0600Z 13.1N  38.3W    40 KT
 24HR VT     02/1800Z 13.4N  39.9W    40 KT
 36HR VT     03/0600Z 13.7N  41.2W    45 KT
 48HR VT     03/1800Z 14.0N  42.5W    50 KT
 72HR VT     04/1800Z 15.0N  45.5W    55 KT
 96HR VT     05/1800Z 15.5N  50.0W    65 KT
120HR VT     06/1800Z 16.5N  54.5W    75 KT
 
$$
FORECASTER BLAKE
 

WTNT44 KNHC 020255
TCDAT4
TROPICAL STORM GASTON DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092010
1100 PM AST WED SEP 01 2010
 
GASTON HAS MAINTAINED A WELL-DEFINED CURVED BAND OF CONVECTION THAT
WRAPS FROM THE WESTERN TO NORTHERN SIDES OF THE CIRCULATION...AND
DVORAK FINAL-T NUMBERS ARE T2.5/35 KT FROM BOTH TAFB AND SAB.  THE
OBJECTIVE ADT ESTIMATE FROM UW-CIMSS IS CURRENTLY T3.3/51 KT...BUT
A RECENT 0013 UTC ASCAT PASS SHOWS WINDS NO HIGHER THAN 25-30 KT.
THE INITIAL INTENSITY IS KEPT AT 35 KT AS A BLEND OF THESE
ESTIMATES.
 
THE OFFICIAL INTENSITY FORECAST HAS AGAIN BEEN INCREASED A BIT FROM
THE PREVIOUS ADVISORY.  ALTHOUGH THERE IS SOME DRY AIR SURROUNDING
THE CYCLONE...GLOBAL MODEL GUIDANCE SUGGESTS THAT THE VERTICAL
SHEAR SHOULD REMAIN LOW...AT LEAST FOR THE NEXT 2-3 DAYS...AND THIS
COULD PREVENT THE DRY AIR FROM HAVING A SIGNIFICANT EFFECT.
STILL...THERE IS A LOT OF UNCERTAINTY IN THE INTENSITY FORECAST
GIVEN THE DIFFERENCES BETWEEN THE DYNAMICAL AND STATISTICAL MODELS.
OVER THE NEXT 5 DAYS...THE GFDL AND HWRF ONLY STRENGTHEN GASTON TO
A STRONG TROPICAL STORM OR MINIMAL HURRICANE...THE SHIPS MODEL
MAKES IT A CATEGORY 2 HURRICANE...AND THE LGEM BRINGS IT TO
CATEGORY 4 INTENSITY.  THE OFFICIAL FORECAST IS A LITTLE ABOVE THE
INTENSITY CONSENSUS FOR THE FIRST 48 HOURS WHEN ENVIRONMENTAL
CONDITIONS SHOULD BE MOST IDEAL AND THEN VERY CLOSE TO THE
CONSENSUS THEREAFTER WHEN EASTERLY SHEAR COULD INCREASE A BIT.
 
THE LATEST SATELLITE FIXES INDICATE THAT GASTON HAS BEGUN TO SLOW
DOWN...POSSIBLY DUE TO A MID-LEVEL TROUGH LOCATED TO ITS
NORTHWEST.  IT IS ALSO A LITTLE FARTHER NORTH THAN PREVIOUSLY
ESTIMATED AND HAS AN INITIAL MOTION OF 280/10 KT.  WITH THE BREAK
IN THE SUBTROPICAL RIDGE...GASTON IS EXPECTED TO CONTINUE TO
SLOW DOWN OVER THE NEXT COUPLE OF DAYS.  THE MULTI-MODEL CONSENSUS
TVCN IS SLOWER THAN THE PREVIOUS FORECAST...SO THE NEW OFFICIAL
FORECAST SHOWS A SLOWER MOTION OVER THE NEXT 36 HOURS...BUT IS
STILL ON THE SAME GENERAL TRACK AS THE PREVIOUS ADVISORY.  BY DAYS
4 AND 5...THE RIDGE IS EXPECTED TO STRENGTHEN...AND THE CYCLONE
SHOULD BEGIN TO MOVE FASTER TO THE WEST.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/0300Z 13.4N  37.7W    35 KT
 12HR VT     02/1200Z 13.5N  38.5W    40 KT
 24HR VT     03/0000Z 13.7N  39.7W    45 KT
 36HR VT     03/1200Z 13.8N  40.8W    50 KT
 48HR VT     04/0000Z 14.0N  42.1W    55 KT
 72HR VT     05/0000Z 14.5N  45.5W    65 KT
 96HR VT     06/0000Z 15.0N  49.5W    75 KT
120HR VT     07/0000Z 16.0N  54.5W    85 KT
 
$$
FORECASTER BERG
 

WTNT44 KNHC 020845
TCDAT4
TROPICAL STORM GASTON DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092010
500 AM AST THU SEP 02 2010

SATELLITE IMAGES INDICATE THAT GASTON HAS GENERALLY CHANGED LITTLE
IN ORGANIZATION THIS MORNING. THUNDERSTORM ACTIVITY REMAINS CONFINED
TO A CURVED BAND OVER THE WESTERN SEMICIRCLE...BUT THE CLOUD TOPS
HAVE BEEN WARMING SLIGHTLY DURING THE LAST COUPLE OF HOURS. DVORAK
DATA T-NUMBERS ARE 35 KT FROM BOTH TAFB AND SAB...AND THE INITIAL
INTENSITY IS HELD AT THAT VALUE.  CONDITIONS GENERALLY APPEAR
FAVORABLE FOR A GRADUAL INTENSIFICATION DURING THE NEXT SEVERAL
DAYS AS GASTON REMAINS IN A LOW WIND SHEAR ENVIRONMENT AND OVER
WARM WATERS. HOWEVER...WATER VAPOR IMAGERY SHOWS THAT GASTON IS
PARTIALLY EMBEDDED IN A DRY MID- TO UPPER-LEVEL AIR MASS WHICH COULD
PROVE TO BE A LIMITING FACTOR.  GIVEN THE UNCERTAINTY...THE
OFFICIAL INTENSITY FORECAST IS UNCHANGED FROM EARLIER...LYING IN
BETWEEN THE DYNAMICAL MODEL GUIDANCE AND THE MORE AGGRESSIVE
STATISTICAL MODEL OUTPUT.
  
GASTON CONTINUES TO DECELERATE AS IT FEELS THE EFFECTS OF A DEEP
LAYER TROUGH TO ITS NORTH...AND THE INITIAL MOTION ESTIMATE IS NOW
280/8. GASTON IS FORECAST TO SLOW DOWN EVEN MORE OVER THE NEXT
COUPLE OF DAYS AS THE STORM REMAINS IN WEAK STEERING CURRENTS. BY
48-72 HOURS...GLOBAL MODELS SHOW SOME MID-LEVEL RIDGING BUILDING TO
THE NORTH OF GASTON AND THAT SHOULD STEER THE SYSTEM WESTWARD OR
EVEN WEST-SOUTHWESTWARD AT A SLIGHTLY FASTER SPEED. THE OFFICIAL
TRACK FORECAST IS A LITTLE SLOWER AND SLIGHTLY TO THE SOUTH OF THE
PREVIOUS ONE IN BEST AGREEMENT WITH THE MULTI-MODEL CONSENSUS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/0900Z 13.5N  38.2W    35 KT
 12HR VT     02/1800Z 13.6N  39.0W    40 KT
 24HR VT     03/0600Z 13.8N  40.1W    45 KT
 36HR VT     03/1800Z 14.0N  41.2W    50 KT
 48HR VT     04/0600Z 14.2N  42.5W    55 KT
 72HR VT     05/0600Z 14.6N  45.9W    65 KT
 96HR VT     06/0600Z 15.0N  50.0W    75 KT
120HR VT     07/0600Z 16.0N  55.0W    85 KT
 
$$
FORECASTER CANGIALOSI/KIMBERLAIN
 

WTNT44 KNHC 021438
TCDAT4
TROPICAL DEPRESSION GASTON DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092010
1100 AM AST THU SEP 02 2010
 
METEOSAT-9 VISIBLE AND INFRARED IMAGES SHOW THAT DEEP CONVECTION
ASSOCIATED WITH GASTON HAS DECREASED CONSIDERABLY AND IS LIMITED TO
A FRAGMENTED BAND OVER THE WESTERN AND NORTHERN PORTION OF THE
CIRCULATION.  THE PIRATA PREDICTION AND RESEARCH BUOY 13008 LOCATED
ABOUT 80 N MI NORTH-NORTHEAST OF THE CENTER HAS BEEN ONLY AVERAGING
AROUND 17 KT DURING THE PAST 6 HOURS.  DVORAK SATELLITE INTENSITY
ESTIMATES HAVE DECREASED TO 30 KT FROM BOTH TAFB AND SAB.  BASED ON
THESE DATA...GASTON IS LOWERED TO TROPICAL DEPRESSION STATUS.
ALTHOUGH THE UPPER WIND PATTERN IS FORECAST TO BE CONDUCIVE FOR
STRENGTHENING...THE RATHER DRY AND STABLE THERMODYNAMIC ENVIRONMENT
DOMINATING THE EASTERN TROPICAL ATLANTIC SHOULD ONLY PERMIT SLOW
INTENSIFICATION.  A NATIONAL SCIENCE FOUNDATION G-V AIRCRAFT IS
CURRENTLY ENROUTE ON A PREDICT RESEARCH MISSION TO SAMPLE THE
SURROUNDING ENVIRONMENT.  THE OFFICIAL INTENSITY FORECAST FOLLOWS
THE ICON CONSENSUS MODEL...AND IS CLOSE TO THE SHIPS AND LGEM
MODELS AT DAYS 4 AND 5.
 
GASTON IS MOVING A LITTLE SLOWER AND TO THE RIGHT OF THE PREVIOUS
ADVISORY...AROUND 290/6...IN RESPONSE TO A MID- TO UPPER-LEVEL HIGH
AMPLITUDE TROUGH SITUATED ALONG 38W AND TO THE NORTH OF THE
TROPICAL CYCLONE.  THE LARGE-SCALE MODELS AGREE ON A CONTINUED
SLOW WEST-NORTHWESTWARD MOTION WITHIN THE WEAK EASTERLY STEERING
FLOW INFLUENCED BY THE AFOREMENTIONED TROUGH THROUGH ABOUT 36
HOURS.  AFTERWARDS...THE DYNAMICAL MODELS INDICATE THAT THE
SUBTROPICAL RIDGE WILL BUILD EASTWARD OVER THE CENTRAL ATLANTIC
THROUGH THE END OF THE PERIOD WHICH WOULD INFLUENCE GASTON TO MOVE
GENERALLY WESTWARD AT A SLIGHTLY QUICKER PACE.  THE NHC OFFICIAL
FORECAST IS A LITTLE TO THE RIGHT OF THE PREVIOUS TRACK AND IS BASED
ON A COMPROMISE OF ALL OF THE DYNAMICAL MODELS. 
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/1500Z 14.0N  38.9W    30 KT
 12HR VT     03/0000Z 14.1N  39.7W    30 KT
 24HR VT     03/1200Z 14.3N  40.7W    35 KT
 36HR VT     04/0000Z 14.5N  42.0W    45 KT
 48HR VT     04/1200Z 14.7N  43.3W    50 KT
 72HR VT     05/1200Z 15.0N  46.5W    60 KT
 96HR VT     06/1200Z 15.5N  51.0W    70 KT
120HR VT     07/1200Z 16.0N  56.0W    85 KT
 
$$
FORECASTER ROBERTS/PASCH
 

WTNT44 KNHC 022033
TCDAT4
TROPICAL DEPRESSION GASTON DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092010
500 PM AST THU SEP 02 2010
 
CONVENTIONAL SATELLITE IMAGERY AND DROPSONDES FROM THE NATIONAL
SCIENCE FOUNDATION G-V AIRCRAFT INDICATE THAT GASTON HAS
DEGENERATED INTO A REMNANT LOW PRESSURE AREA.  THE SYSTEM CONSISTS
OF A WEAK LOW-LEVEL CIRCULATION WITHOUT ORGANIZED DEEP CONVECTION.
MAXIMUM WINDS ARE ESTIMATED TO BE 25 KT...AND THESE WINDS ARE LIKELY
OCCURRING ONLY IN A SMALL AREA OF SHOWERS WELL TO THE NORTH OF THE
CENTER.
 
THE REMNANT LOW IS SITUATED TO THE SOUTH OF A WEAKNESS IN THE
SUBTROPICAL RIDGE...AND IS DRIFTING WESTWARD.  THE LARGE-SCALE
MODELS PREDICT SOME BUILDING OF RIDGE TO THE NORTH OF THE CYCLONE
OVER THE NEXT FEW DAYS. THEREFORE...THE OFFICIAL FORECAST TRACK
INDICATES A CONTINUED GENERAL WESTWARD MOTION WITH A GRADUAL
INCREASE IN FORWARD SPEED.

ALTHOUGH NOT EXPLICITLY INDICATED HERE...THERE IS A POSSIBILITY THAT
GASTON COULD REGENERATE INTO A TROPICAL CYCLONE DURING THE FORECAST
PERIOD.  THIS IS THE SCENARIO THAT IS BEING SUGGESTED BY SOME OF THE
GLOBAL MODELS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/2100Z 13.5N  39.5W    25 KT
 12HR VT     03/0600Z 13.5N  40.4W    25 KT...POST-TROP/REMNT LOW
 24HR VT     03/1800Z 13.7N  41.7W    25 KT...POST-TROP/REMNT LOW
 36HR VT     04/0600Z 14.0N  43.0W    25 KT...POST-TROP/REMNT LOW
 48HR VT     04/1800Z 14.2N  44.4W    25 KT...POST-TROP/REMNT LOW
 72HR VT     05/1800Z 14.5N  48.0W    25 KT...POST-TROP/REMNT LOW
 96HR VT     06/1800Z 15.0N  52.5W    25 KT...POST-TROP/REMNT LOW
120HR VT     07/1800Z 15.5N  57.5W    25 KT...POST-TROP/REMNT LOW
 
$$
FORECASTER ROBERTS/PASCH
 

