[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 032351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED AUG 03 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA... GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN
COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURE...
TROPICAL STORM HARVEY WAS NEAR 31.3N 66.5W AT 04/0000 UTC MOVING
ENE 9 KT...OR ABOUT 130 MILES/210 KM WEST-SOUTHWEST OF BERMUDA.
THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 998 MB. THE MAXIMUM
SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. SEE THE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT3/WTNT23 KNHC OR MIATCPAT3/WTNT33 KNHC FOR MORE DETAILS.
ALTHOUGH CONVECTION HAS BEEN RATHER MEAGER IN THE CENTRAL
CORE... THE SUSTAINED WINDS HAVE SIGNIFICANTLY INCREASED...
PERHAPS WITH A LITTLE HELP FROM THE UPPER LOW TO THE SW.
ALTHOUGH HARVEY IS NOT A PURELY TROPICAL SYSTEM... TSTMS ARE NOW
FORMING CLOSER TO THE CENTER THOUGH A COMMA-LIKE APPEARANCE
REMAINS ON SATELLITE.  ONE LARGE BAND EXTENDS CYCLONICALLY
AROUND THE E SEMICIRCLE ABOUT 150 NM FROM THE CENTER WITH
SHOWERS/TSTMS.  WIDELY SCATTERED MODERATE CONVECTION IS WITHIN
60 NM OF LINE 23N67W 28N63W 31N62W 35N65W.  BUILDING UPPER RIDGE
EXTENDS FROM 24N64W TO 34N59W IS CAUSING A HUGE SHIELD OF HIGH
CLOUDS N AND E OF HARVEY ALONG WITH PROVIDING A FAVORABLE UPPER
ENVIRONMENT S AND E OF THE CYCLONE FOR SHOWER/TSTM ACTIVITY.

...TROPICAL WAVES...

COMPLEX E-CENTRAL ATLANTIC TROPICAL WAVE ALONG 32W/33W SOUTH OF
19N MOVING W 10-15 KT.  THE LOW CLOUD CURVATURE SUGGESTS THAT
THE WAVE HAS LEFT A 1008 MB LOW CENTER BEHIND THE WAVE NEAR
11N29W.  TSTMS HAVE MARKEDLY INCREASED SINCE YESTERDAY UNDER A
RATHER DIFFLUENT ENVIRONMENT ALOFT.  MOST COMPUTER MODELS
SUGGEST A WNW TRACK OF THE LOW WITH RELATIVELY LOW SHEAR
FORECAST FOR THE NEXT FEW DAYS WHILE THE WAVE TRACKS WESTWARD AT
A SPEED SLIGHTLY FASTER THAN THE LOW.  LAST VISIBLE SATELLITE
PICTURES SUGGESTED THAT BANDING FEATURES WERE TRYING TO FORM
CLOSE TO THE LOW THOUGH THE CONVECTIVE PATTERN TONIGHT... WHILE
QUITE ACTIVE... DOESN'T APPEAR TOO ORGANIZED.  HOWEVER QUIKSCAT
RECENTLY SHOWED A CLOSED LOW WITH UNCONTAMINATED 25 KT WINDS...
SIGNS OF A STRONG SYSTEM DESPITE THE DISHEVELED CLOUD PATTERN.
WIDELY SCATTERED MODERATE CONVECTION IS FROM 8.5N-13N BETWEEN
27W-33W.

CENTRAL CARIBBEAN TROPICAL WAVE IS ALONG 72W S OF 20N MOVING W
10-15 KT.  THE WAVE IS DIFFICULT TO SEE IN VISIBLE SATELLITE
WITH PERHAPS THE BEST WAY TO TRACK THE SYSTEM USING THE
INCREASING CONVECTION THAT HAS SHIFTED W OVER HAITI TODAY FROM
PUERTO RICO AND THE US VIRGIN ISLANDS YESTERDAY.   A DRIER DAY
IS EXPECTED FOR HISPANIOLA TOMORROW WITH THE HEAVIEST
PRECIPITATION MOVING TO CUBA INTO JAMAICA.  SCATTERED MODERATE
CONVECTION OVER HAITI WITH A FEW TSTMS S TO 16N72W.

W CARIBBEAN TROPICAL WAVE IS ALONG 82W S OF 19N MOVING W 10-15
KT.  WIND OBSERVATIONS OF SE WINDS AT GRAND CAYMAN WITH NE WINDS
AT THE NW CARIBBEAN BUOY HELP POSITION THE WAVE.  SCATTERED
MODERATE TSTMS ARE S OF SAN ANDRES W OF 81W.

...ITCZ...

ITCZ AXIS IS ALONG 13N17W 12N28W 8N37W 6N56W.  WIDELY SCATTERED
MODERATE CONVECTION WITHIN 45 NM OF THE ITCZ FROM 22W-40W.

...DISCUSSION...

GULF OF MEXICO...
WEAK HIGH PRESSURE CONTINUES IN THE NRN GULF WITH LIGHT WINDS
ALMOST EVERYWHERE IN THE REGION.  ILL-DEFINED SURFACE TROUGH
REMAINS FROM NEAR PANAMA CITY TO THE MOUTH OF THE MISSISSIPPI
RIVER AND HELPED TO FIRE DIURNAL TSTMS IN THE REGION.  UPPER
DIVERGENCE PATTERN IS IN PLACE OVER THE NRN GULF WITH PLENTIFUL
DEEP-LAYERED MOISTURE KEEPING SEA-BREEZE TSTMS ACTIVE.  THE
DIVERGENT PATTERN IS BEING CAUSED BY A MID/UPPER TROUGH
EXTENDING FROM NE NEAR 28N102W TO 29N95W COMBINED WITH A
MID/UPPER HIGH OVER THE NW ATLC NEAR 29N77W.. WITH SW WINDS OVER
N FLORIDA AND SE WINDS OVER SE TEXAS ALOFT.  LITTLE CHANGE IS
LIKELY FOR THE NEXT FEW DAYS WITH THE SURFACE TROUGH NEARLY
STATIONARY... PRODUCING A WETTER-THAN-AVERAGE PERIOD FOR THE
GULF COAST.  ACTIVE CONVECTION IS AGAIN POSSIBLE IN THE BAY OF
CAMPECHE IN THE LATE AFTERNOON AS TSTMS FROM YUCATAN MOVE
OFFSHORE INTO THE REGION.  THE BIGGEST CHANGE OVER THE NEXT FEW
DAYS SHOULD BE INCREASING MOISTURE/SHOWERS IN THE SOUTHERN GULF
ASSOCIATED WITH THE NORTHERN END OF TROPICAL WAVES MOVING
THROUGH THE AREA.

CARIBBEAN SEA...
GENERALLY DRY AIR IN THE MID-LEVELS CONTROLS MOST OF THE AREA
EXCEPT AROUND THE TROPICAL WAVES.  AS HAS BEEN THE CASE FOR THE
LAST SEVERAL DAYS...DIURNAL TSTMS OVER THE GREATER ANTILLES ARE
THE MAIN STORY WITH LESS TSTMS OVER PUERTO RICO THAN YESTERDAY.
TWO MAIN UPPER FEATURES CONTINUE IN THE AREA... THE FIRST BEING
A LOW NEAR 19N82W W OF THE CAYMANS... AND A MID/UPPER HIGH OVER
DOMINICAN REPUBLIC. ELY WINDS CONTROL THE E CARIBBEAN E OF 73W
WITH MODERATE TO STRONG SUBSIDENCE OVER WATER.  CENTRAL AMERICA
LOOKS FAIRLY WET UNTIL THE WEEKEND WITH SOME DRYING POSSIBLE N
OF NICARAGUA.  TRADEWINDS ARE BACK TO NEAR TO SLIGHTLY ABOVE
AVERAGE IN THE W AND CENTRAL CARIBBEAN THOUGH PRESSURES ARE
CONSIDERABLY BELOW AVERAGE.  A MID/UPPER LOW IS FORECAST TO MOVE
THRU THE LEEWARD ISLANDS BRINGING RATHER DRY WEATHER FOR THE
LESSER ANTILLES FOR THE NEXT COUPLE OF DAYS WITH THE BEST CHANCE
OF RAIN IN THE SOUTHWARD WINDWARD ISLANDS.  NO SIGNIFICANT
INCREASE IN MOISTURE IS FORECAST UNTIL EARLY NEXT WEEK.

ATLANTIC OCEAN...
UPPER LOW IS SW OF HARVEY NEAR 29N77W AND IS KEEPING THE SYSTEM
LOOKING SOMEWHAT SUBTROPICAL THOUGH THE SHEAR ISN'T TOO STRONG.
THE REMNANTS OF A FRONTAL ZONE ARE RESPONSIBLE FOR A FEW SHOWERS
AND OVERCAST HIGH CLOUDS N OF 28N W OF 75W WITH SOME
REDEVELOPMENT POSSIBLE TOMORROW IN UPPER DIFFLUENCE ON THE N
SIDE OF AN UPPER HIGH NEAR THE NW BAHAMAS.  FARTHER E...A DEEP
MID-OCEANIC TROUGH EXTENDS FROM A LOW NEAR 30N43W SW TO A
SECONDARY LOW DROPPING SW AND BREAKING OFF FROM THE TROUGH NEAR
17N56W WITH THE TROUGH CONTINUING S TO 6N55W.  OTHERWISE SURFACE
HIGH PRESSURE IS ENTRENCHED IN THE E ATLC WITH VERY DRY AIR
ALOFT N OF 16N AND ENHANCED TRADES W OF THE CAPE VERDES.
SURFACE RIDGE RUNS FROM 32N37W TO 23N65W THOUGH THERE HAS BEEN A
SLIGHT WEAKENING OF THE HIGH N OF 20N E OF 40W SINCE YESTERDAY.
ELSEWHERE IN THE NE ATLC... MID/UPPER HIGH IS NEAR 27N28W WITH
STRONG SUBSIDENCE ALOFT N OF 20N BETWEEN 20W-40W.  A CLOSED
UPPER LOW IS NE OF THE CANARY ISLANDS NEAR 30N12W WITH DRY AIR
ALOFT KEEPING THE NW SAHEL A BIT DRIER THAN AVERAGE.  IN THE
DEEP TROPICS... A BUILDING MID/UPPER HIGH IS NEAR 16N28W
VERDES RIDGING SW TO 10N54W WHERE IT MEETS THE MID-OCEANIC
TROUGH.  UPPER CONDITIONS ARE AS FAVORABLE AS THEY HAVE BEEN IN
A WHILE WITH THE MID-OCEANIC TROUGH RETREATING WESTWARD SOME AS
THE RIDGE SHIFTS INTO THE CENTRAL ATLC.   UPPER DIVERGENCE IS
FUELING INCREASING ITCZ CONVECTION S OF THE RIDGE AXIS E OF
45W.

$$
BLAKE

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