WTNT41 KNHC 212031
TCDAT1
TROPICAL DEPRESSION SIX DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
500 PM EDT SAT AUG 21 2010
 
SATELLITE IMAGES INDICATE THAT THE AREA OF LOW PRESSURE SOUTHWEST OF
THE CAPE VERDE ISLANDS HAS BECOME CONSIDERABLY BETTER ORGANIZED
DURING THE PAST SEVERAL HOURS. THE LOW APPEARS TO HAVE BECOME
MORE SEPARATED FROM THE LARGE AREA OF SOUTHWESTERLY FLOW WHICH HAS
BEEN PRESENT OVER THE TROPICAL ATLANTIC FOR THE PAST SEVERAL
DAYS....THOUGH IT IS STILL A BIT ELONGATED TO THE NORTHEAST. A LONG
CURVED BAND OF CONVECTION ALSO WRAPS AROUND THE SOUTHERN AND
WESTERN SEMICIRCLE. THE INITIAL INTENSITY WILL BE 25 KT...WHICH
AGREES WITH DVORAK CLASSIFICATIONS FROM TAFB/SAB OF T1.5...25
KT...AND A 25 KT ASCAT PASS FROM THIS MORNING.
 
A LARGE UPPER-LEVEL ANTICYCLONE IS FORECAST TO BE NEAR THE
DEPRESSION...WHICH SHOULD CAUSE ONLY WEAK TO MODERATE NORTHEASTERLY
SHEAR FOR THE NEXT SEVERAL DAYS. COMBINED WITH WARM SSTS...AT LEAST
STEADY STRENGTHENING IS EXPECTED UNTIL THE END OF THE FORECAST
PERIOD. BY THAT TIME...SOME INCREASE IN SOUTHWESTERLY SHEAR IS
POSSIBLE AS THE CYCLONE APPROACHES THE MID-OCEANIC TROUGH.  THE
INTENSITY GUIDANCE IS IN RELATIVELY GOOD AGREEMENT FOR SUCH A WEAK
SYSTEM WITH ALL RELIABLE GUIDANCE MAKING THE DEPRESSION A HURRICANE
WITHIN A FEW DAYS. THE NHC FORECAST IS CLOSE TO THE SHIPS/LGEM
MODELS...SHOWING A LARGE POWERFUL HURRICANE OVER THE CENTRAL
ATLANTIC OCEAN IN A FEW DAYS.
 
THE INITIAL MOTION ESTIMATE IS 285/7. A WEST-NORTHWEST MOTION WITH
INCREASING FORWARD SPEED IS EXPECTED AS THE DEPRESSION LEAVES THE
STRONG WESTERLY LOW-LEVEL FLOW ENVIRONMENT OF THE TROPICAL ATLANTIC
AND BECOMES STEERED BY A RIDGE OVER THE CENTRAL ATLANTIC OCEAN.
MOST OF THE MODELS SHOW THE CYCLONE TURNING TOWARD THE NORTHWEST
DUE TO A WEAKNESS IN THE RIDGE ALONG 50W IN ABOUT 3 DAYS. MODEL
GUIDANCE IS FAIRLY CLUSTERED AROUND THIS SOLUTION...WITH THE BIG
OUTLIERS TO THE NORTHEAST BEING THE CMC AND THE ECMWF MODELS. THESE
MODELS SHOW THE SYSTEM MOVING NORTHWEST SOON...WHICH ALLOWS THE
SYSTEM TO RECURVE TOWARD THE NORTH DUE TO A TROUGH ALONG 50W. THE
OFFICIAL FORECAST IS CLOSE TO...BUT SLIGHTLY TO THE LEFT OF...THE
DYNAMICAL MODEL CONSENSUS.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/2100Z 11.0N  32.1W    25 KT
 12HR VT     22/0600Z 11.5N  33.2W    35 KT
 24HR VT     22/1800Z 12.6N  35.4W    45 KT
 36HR VT     23/0600Z 13.6N  38.2W    55 KT
 48HR VT     23/1800Z 14.4N  41.4W    65 KT
 72HR VT     24/1800Z 17.5N  47.5W    85 KT
 96HR VT     25/1800Z 21.0N  52.0W    95 KT
120HR VT     26/1800Z 24.5N  55.5W    95 KT
 
$$
FORECASTER BLAKE
 

WTNT41 KNHC 220243
TCDAT1
TROPICAL DEPRESSION SIX DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
1100 PM AST SAT AUG 21 2010
 
CONVENTIONAL SATELLITE AND A 2202 UTC SSMIS MICROWAVE OVERPASS SHOW
IMPROVED CURVED BANDING...PARTICULARLY OVER THE WESTERN PORTION OF
THE CYCLONE. ALTHOUGH DEEP CONVECTION REMAINS A BIT LIMITED OVER
THE EASTERN SEMI-CIRCLE...A 2300 UTC ASCAT PASS INDICATED A MORE
SYMMETRIC CIRCULATION THAN EARLIER NOTED...AND BELIEVABLE 25 KT
WINDS OVER THE SOUTHEAST QUADRANT. OUTFLOW OVER THE NORTHWESTERN
AREA OF THE SYSTEM APPEARS TO BE IMPROVING AND HAS BECOME MORE
DIFFLUENT. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE 2.0
AND 1.5 RESPECTIVELY. BASED ON THE PREMISE THAT THE WINDS ARE
PROBABLY A LITTLE STRONGER IN THE CONVECTIVE BANDING TO THE WEST
AND NORTHWEST OF THE CENTER...THE INITIAL INTENSITY IS ADJUSTED UP
TO 30 KT. 

THE CYCLONE SHOULD GRADUALLY STRENGTHEN AS IT REMAINS OVER WARM SEA
SURFACE TEMPERATURES AND WITHIN A RELATIVELY LOW NORTHEASTERLY
SHEAR ENVIRONMENT DURING...AT LEAST FOR THE NEXT 3 DAYS. THE SHIPS
AND THE GFDL CONTINUE TO INDICATE THAT THE SYSTEM WILL BECOME A
HURRICANE WITHIN 3 DAYS...AND THIS IS ALSO INDICATED IN THE
OFFICIAL FORECAST.  THROUGH THE REMAINING PERIOD...INCREASING
SOUTHWESTERLY SHEAR IS EXPECTED OVER THE TRACK IN RESPONSE TO A MID
TO UPPER TROUGH MOVING OFF OF THE EASTERN SEABOARD AROUND DAY 5. 
SUBSEQUENTLY...THE INTENSITY FORECAST INDICATES ONLY MODEST
STRENGTHENING DURING THIS TIME-FRAME.

THE SYSTEM HAS BEEN MOVING WEST-NORTHWESTWARD...OR...290/7. THE DEEP
TRADES ASSOCIATED WITH THE SUBTROPICAL RIDGE TO THE NORTH OF THE
DEPRESSION NOW APPEAR TO BE THE MORE DOMINANT STEERING
MECHANISM...WITH LESS OF AN INFLUENCE FROM THE SOUTHWESTERLY
MONSOONAL FLOW.  DYNAMICAL MODELS ARE IN GOOD AGREEMENT WITH THE
RIDGE STEERING THE CYCLONE IN A WEST-NORTHWESTWARD MOTION THROUGH
DAY 3.  AFTERWARD...A TURN TOWARD THE NORTHWEST IS INDICATED IN THE
OFFICIAL FORECAST AS A DEEP-LAYER MID-LATITUDE TROUGH MOVES OVER
THE CENTRAL ATLANTIC AND BREAKS DOWN THE WESTERN PERIPHERY OF THE
RIDGE.  THE NHC TRACK FORECAST IS A LITTLE SLOWER THAN THE PREVIOUS
ADVISORY...AND IS BASED ON THE MULTI-MODEL CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/0300Z 11.3N  32.6W    30 KT
 12HR VT     22/1200Z 12.0N  33.9W    35 KT
 24HR VT     23/0000Z 12.9N  36.0W    40 KT
 36HR VT     23/1200Z 13.8N  38.4W    50 KT
 48HR VT     24/0000Z 14.7N  41.3W    60 KT
 72HR VT     25/0000Z 18.0N  47.0W    80 KT
 96HR VT     26/0000Z 21.5N  51.5W    90 KT
120HR VT     27/0000Z 25.0N  55.0W    95 KT
 
$$
FORECASTER ROBERTS/BEVEN
 

WTNT41 KNHC 220833
TCDAT1
TROPICAL DEPRESSION SIX DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
500 AM AST SUN AUG 22 2010

SATELLITE IMAGES INDICATE THAT THE DEPRESSION IS GRADUALLY BECOMING
BETTER ORGANIZED...WITH THE DEVELOPMENT IN THE LAST SEVERAL HOURS
OF A DISTINCT CURVED BAND WRAPPING NEARLY HALFWAY AROUND THE WESTERN
SIDE OF THE CIRCULATION. HOWEVER...THE CIRCULATION CENTER REMAINS
SEPARATED FROM THE DEEP CONVECTION.  SATELLITE INTENSITY ESTIMATES
ARE AT 2.0 AND 2.5 FROM SAB AND TAFB...RESPECTIVELY.  WITH THE LACK
OF A CONSENSUS FROM BOTH SATELLITE AGENCIES AND LITTLE DEEP
CONVECTION NEAR THE CENTER...THE INTENSITY IS HELD AT 30 KT FOR
THIS ADVISORY.

RECENT CENTER FIXES ARE A BIT UNCERTAIN GIVEN A LACK OF MICROWAVE
DATA BUT YIELD AN INITIAL MOTION OF 295/08...A LITTLE TO THE RIGHT
AND FASTER THAN THE PREVIOUS ESTIMATE.  A DEEP LAYER EAST-
SOUTHEASTERLY FLOW SOUTH OF A SUBTROPICAL RIDGE SHOULD STEER THE
CYCLONE ON A GENERAL WEST-NORTHWESTWARD COURSE FOR THE NEXT COUPLE
OF DAYS...WITH SOME INCREASE IN FORWARD SPEED.  WATER VAPOR IMAGERY
INDICATES A MID- TO UPPER-LEVEL LOW NEAR 27N41W THAT IS FORECAST BY
THE GLOBAL MODELS TO MOVE SOUTHWEST AND CAUSE A DEVELOPING WEAKNESS
IN THE RIDGE BETWEEN 45-50W IN ABOUT 72 HOURS.  THE WEAKNESS IN THE
RIDGE BECOMES MORE PRONOUNCED AS A LARGER MID-LATITUDE TROUGH IS
FORECAST TO DIG OVER THE EAST CENTRAL ATLANTIC LATE IN THE FORECAST
PERIOD. MODEL GUIDANCE IS NOW A BIT MORE DIVERGENT BUT SHOWS THE
DEPRESSION MOVING WEST-NORTHWESTWARD TO NORTHWESTWARD WITH A
DECREASE IN FORWARD SPEED AS IT MOVES INTO THE WEAKNESS.  THE
OFFICIAL NHC FORECAST TRACK IS SLOWED AT LATER FORECAST TIMES AS A
RESULT OF A SLOWER TREND IN THE GUIDANCE AND INCREASING MODEL
SPREAD.

SHIPS MODEL OUTPUT AND UW-CIMSS SHEAR ANALYSES INDICATE MODERATE
EAST-NORTHEASTERLY VERTICAL WIND SHEAR OVER THE CYCLONE...SEEMINGLY
CONFIRMED BY THE EXPOSED NATURE OF THE CIRCULATION CENTER. 
HOWEVER...THE SHEAR IS EXPECTED TO DECREASE AS THE DEPRESSION MOVES
OUT OF THE LOW-LEVEL MONSOONAL FLOW OVER THE EASTERN TROPICAL
ATLANTIC.  THE LOWER SHEAR ENVIRONMENT ALONG WITH INCREASING SSTS
SHOULD FAVOR A GRADUAL INTENSIFICATION...AND THE DEPRESSION IS
FORECAST TO REACH HURRICANE STRENGTH WITHIN 3 DAYS.  THEREAFTER...
AN INCREASE IN SOUTHWESTERLY VERTICAL WIND SHEAR ASSOCIATED WITH
THE DIGGING TROUGH OVER THE CENTRAL ATLANTIC COULD HAMPER FURTHER
INTENSIFICATION.  THE OFFICIAL WIND SPEED FORECAST IS REDUCED ONLY
SLIGHTLY FROM THE PREVIOUS ONE THROUGHOUT THE FORECAST PERIOD AND
IS IN BEST AGREEMENT WITH THE LGEM STATISTICAL INTENSITY GUIDANCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/0900Z 12.1N  33.4W    30 KT
 12HR VT     22/1800Z 12.6N  34.6W    35 KT
 24HR VT     23/0600Z 13.4N  36.6W    40 KT
 36HR VT     23/1800Z 14.4N  39.2W    45 KT
 48HR VT     24/0600Z 15.5N  42.0W    55 KT
 72HR VT     25/0600Z 18.5N  47.5W    75 KT
 96HR VT     26/0600Z 22.0N  52.0W    85 KT
120HR VT     27/0600Z 24.5N  55.0W    90 KT
 
$$
FORECASTER KIMBERLAIN
 

WTNT41 KNHC 221452
TCDAT1
TROPICAL DEPRESSION SIX DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
1100 AM AST SUN AUG 22 2010
 
THE UPWARD TREND IN ORGANIZATION OF THE DEPRESSION APPEARS TO HAVE
STOPPED FOR THE TIME BEING.  THE SYSTEM HAS A WELL-DEFINED
CENTER...BUT THE CIRCULATION IS A LITTLE STRETCHED FROM NORTHEAST
TO SOUTHWEST DUE TO ANOTHER DISTURBANCE LOCATED ABOUT 350 N MI TO
THE NORTHEAST.  THIS HAS ALSO CAUSED THE CENTER TO MOVE ALMOST DUE
NORTH OVER THE PAST FEW HOURS...PULLING IT FARTHER AWAY FROM THE
DEEP CONVECTION.  SATELLITE INTENSITY ESTIMATES ARE 30 KT AND 45 KT
FROM SAB AND TAFB...RESPECTIVELY...AND AN 1134 UTC ASCAT PASS
SHOWED A MAXIMUM OF 30 KT.  THE INITIAL INTENSITY WILL BE KEPT AT 30
KT SINCE THERE HAS BEEN LITTLE CHANGE IN ORGANIZATION.
 
WITH THE RECENT NORTHWARD MOTION...THE SMOOTHED INITIAL MOTION IS
ROUGHLY 310/10.  ONCE THE DEPRESSION ESCAPES THE INFLUENCE OF THE
DISTURBANCE TO ITS NORTHEAST...THE SUBTROPICAL RIDGE CENTERED ALONG
26N SHOULD STEER THE CYCLONE GENERALLY WEST-NORTHWESTWARD WITH
INCREASING FORWARD SPEED THROUGH THE NEXT 72 HOURS.  BY DAYS 4 AND
5 THERE IS GREATER UNCERTAINTY WITH THE TRACK FORECAST DEPENDING ON
HOW THE MID-LATITUDE LONGWAVE PATTERN EVOLVES IN RELATION TO WHEN
THE DEPRESSION ACTUALLY BEGINS MOVING WESTWARD.  THE GLOBAL MODEL
GUIDANCE IS IN GOOD AGREEMENT SHOWING AN AMPLIFYING TROUGH NEAR 45W
BY DAY 4...WHICH SHOULD BE TOO FAR EAST TO INDUCE SIGNIFICANT
RECURVATURE.  THIS PATTERN...HOWEVER...SHOULD CAUSE THE SYSTEM TO
SLOW DOWN A LITTLE BY DAYS 4 AND 5 AS IT BECOMES TRAPPED TO THE
SOUTH OF A MID-LEVEL RIDGE.  THE OFFICIAL FORECAST HAS BEEN SHIFTED
A LITTLE SOUTH AND WEST BY DAY 5...VERY CLOSE TO THE GFS...GFDL
...AND HWRF MODELS...AND LIES A LITTLE TO THE RIGHT OF THE MODEL
CONSENSUS TVCN.
 
THE DEPRESSION IS EXPECTED TO REMAIN UNDER THE INFLUENCE OF MODERATE
EAST-NORTHEASTERLY SHEAR FOR THE NEXT 24 HOURS OR SO...BUT
THEREAFTER THE UPPER-LEVEL ENVIRONMENT BECOMES MORE CONDUCIVE FOR
STRENGTHENING.  HOWEVER...THE SYSTEM MAY STILL HAVE TO CONTEND WITH
DRY AND RELATIVELY STABLE AIR TO ITS NORTH AS IT MOVES ACROSS THE
ATLANTIC...AND MOST OF THE INTENSITY GUIDANCE NOW SHOWS A SLOWER
RATE OF INTENSIFICATION.  THE OFFICIAL FORECAST HAS BEEN NUDGED
DOWN A LITTLE FROM THE PREVIOUS FORECAST BUT IS STILL HIGHER THAN
EVERY INTENSITY MODEL AT DAY 5 EXCEPT FOR THE GFDL.  BASED ON AN
EXPERIMENTAL INTENSITY PROBABILITY PRODUCT AT NHC...THE DEPRESSION
CURRENTLY HAS A 1 IN 5 CHANCE OF REACHING MAJOR HURRICANE STATUS AT
SOME POINT OVER THE NEXT FIVE DAYS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/1500Z 12.7N  34.1W    30 KT
 12HR VT     23/0000Z 13.0N  35.6W    35 KT
 24HR VT     23/1200Z 13.8N  38.1W    40 KT
 36HR VT     24/0000Z 14.7N  40.8W    50 KT
 48HR VT     24/1200Z 15.9N  43.7W    60 KT
 72HR VT     25/1200Z 19.0N  49.0W    70 KT
 96HR VT     26/1200Z 22.0N  53.0W    80 KT
120HR VT     27/1200Z 24.5N  56.0W    85 KT
 
$$
FORECASTER BERG
 

