[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 030003
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE AUG 02 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...
T.D. EIGHT HAS FORMED THIS AFTERNOON.  IT IS LOCATED NEAR 28.8N
68.8W AT 03/0000 UTC ABOUT 295 NM SW OF BERMUDA MOVING N 11 KT.
MAXIMUM SUSTAINED WINDS ARE 30 KT GUSTING TO 40 KT AND THE
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009 MB.   SEE LATEST NHC
FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC
FOR MORE DETAILS.  THE DEPRESSION FORMED FROM A TROUGH THAT HAD
BROKEN OFF OF A TROPICAL WAVE FROM SEVERAL DAYS AGO... THE SAME
ONE THAT ALMOST DEVELOPED NEAR PUERTO RICO.  A MID/UPPER LOW
NEAR 27N72W HAS BEEN SHEARING THE SYSTEM BUT HAS MOVED S OF THE
LATITUDE OF THE DEPRESSION... A CLASSIC DEVELOPMENT SITUATION
WHERE SHEAR DROPS TO THE N SIDE OF THE LOW AND OUTFLOW EXPANDS
TO THE N.  CONVECTION REMAINS STRONG ON THE N AND E SIDE OF THE
DEPRESSION THOUGH THE SATELLITE APPEARANCE LOOKS A LITTLE
SUBTROPICAL WITH THE UPPER LOW'S PROXIMITY TO THE SURFACE LOW.
A LARGE BALL OF CONVECTION IS NEAR 29N69W WITHIN A DEGREES OF
THE CENTER WITH OTHER WIDELY SCATTERED BANDS OF CONVECTION
BETWEEN 23N-BERMUDA FROM 60W-68W.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE IS ALONG 28W/29W S OF 17N MOVING W 10 KT.
A BROAD 1009 MB LOW IS NEAR 11N28.5W ON THE WAVE AXIS.  VISIBLE
SATELLITE PICTURES AND SURFACE OBSERVATIONS INDICATE A BROAD LOW
HAS FORMED BASICALLY WITHIN THE ITCZ THOUGH THERE ARE ONLY A FEW
TSTMS.  A PLUME OF AFRICAN DUST WRAPS AROUND THE N SIDE OF THE
WAVE N OF 15N E OF THE WAVE AXIS TO 24N.  A MAJORITY OF COMPUTER
MODELS INSIST ON THE GENESIS OF A TROPICAL CYCLONE FROM THIS
WAVE BUT THERE IS LITTLE EVIDENCE TO SUGGEST FORMATION IS LIKELY
ANYTIME SOON.

E CARIBBEAN TROPICAL WAVE EXTENDS FROM NEAR THE US VIRGIN
ISLANDS TO 9N66W MOVING W 10-15 KT.  A BAND OF TSTMS IN PUERTO
RICO EASTWARD TO THE NE LEEWARD ISLANDS IS CLOSE TO THE WAVE
AXIS.  INCREASED TSTMS ARE LIKELY FOR HISPANIOLA TOMORROW WITH
SOME LINGERING EFFECTS TOMORROW IN PUERTO RICO.

CENTRAL CARIBBEAN TROPICAL WAVE IS ALONG 77W/78W S OF 18N MOVING
W 10-15 KT.  BROAD CURVATURE IN THE LOW CLOUDS NW OF COLOMBIA
MIGHT REFLECT THE WAVE AXIS ALONG WITH AN INCREASE IN MID/UPPER
MOISTURE.  THIS WAVE SHOULD INCREASE SHOWER COVERAGE OVER THE W
CARIBBEAN DURING THE NEXT FEW DAYS.

W CARIBBEAN TROPICAL WAVE IS ALONG 92W S OF 17N MOVING W 10 KT.
WAVE HAS LOST ANY SIGNATURE IN THE ATLC BASIN THOUGH IT COULD
HAVE ASSISTED A LARGE BLOWUP OF TSTMS OVER THE YUCATAN TODAY.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 11N16W 12N28W 8N40W 6N53W.  THE ITCZ
IS NOT WELL-DEFINED W OF 50W.  WIDELY SCATTERED MODERATE
CONVECTION IS WITHIN 60 NM OF LINE 7N33W 8.5N46W.  ISOLATED
MODERATE FROM 8N-12N BETWEEN 20W-33W WITH A FEW TSTMS WITHIN 75
NM OF 13N23W.

...DISCUSSION...

GULF OF MEXICO...
ANY SIGN OF THE TROUGH IN THE NORTHERN GULF HAS DISSIPATED WITH
A RATHER WEAK PRESSURE GRADIENT AROUND A 1016 MB HIGH CENTERED
ABOUT 100 NM S OF GRAND ISLE LOUISIANA.   CONSIDERABLE UPPER
DIVERGENCE IS OVER THE CENTRAL AND EASTERN GULF COAST...
PRODUCING PLENTY OF SEA-BREEZE RELATED TSTMS FROM SE TEXAS
EASTWARD THRU MOST OF N FLORIDA.  THIS DIVERGENT PATTERN IS
BEING CAUSED BY A MID/UPPER TROUGH EXTENDING FROM S TEXAS NEAR
27N98W TO 27N92W COMBINED WITH A MID/UPPER HIGH OVER CENTRAL
FLORIDA.. WITH SW WINDS OVER N FLORIDA AND SE WINDS OVER SE
TEXAS ALOFT.  A WETTER-THAN-AVERAGE PERIOD FOR THE GULF COAST
SHOULD CONTINUE FOR THE NEXT COUPLE OF DAYS ALONG A WEAK TROUGH
JUST N OF THE AREA.  ACTIVE CONVECTION IS AGAIN POSSIBLE IN THE
BAY OF CAMPECHE IN THE LATE AFTERNOON AS BIG TSTMS FROM YUCATAN
MOVE OFFSHORE INTO THE REGION.

CARIBBEAN SEA...
RATHER DRY AIR IN THE MID-LEVELS CONTROLS A GOOD PORTION OF THE
AREA EXCEPT AROUND THE TROPICAL WAVES.  A SURGE OF MOISTURE IS
IMPACTING THE WINDWARD ISLANDS TONIGHT WITH SCATTERED SHOWERS
AND A FEW TSTMS... OTHERWISE DIURNAL ACTIVITY OVER THE GREATER
ANTILLES IS THE MAIN ACTIVITY.  TWO MAIN UPPER FEATURES CONTINUE
IN THE AREA... THE FIRST BEING A LOW NEAR 18N82W SW OF THE
CAYMANS... AND A MID/UPPER HIGH N OF PUERTO RICO NEAR 20N67W.
ELY WINDS CONTROL THE E CARIBBEAN E OF 72W WITH MODERATE TO
STRONG SUBSIDENCE OVER WATER.  CENTRAL AMERICA LOOKS FAIRLY WET
FOR THE NEXT COUPLE OF DAYS WITH UPPER-LEVEL DIFFLUENCE PROGGED
OVER THE REGION WITH OCCASIONAL TROPICAL WAVES ENHANCING THE
ACTIVITY EVEN MORE.  IN ADDITION MOISTURE FROM THE TROPICAL WAVE
NEAR JAMAICA SHOULD INCREASE THE SHOWER COVERAGE OVER THE WATER
W OF 80W BY THU.  TRADEWINDS ARE CONSIDERABLY REDUCED FROM LAST
WEEK IN THE CENTRAL CARIBBEAN WITH T.D. EIGHT N OF THE BAHAMAS
HELPING TO WEAKEN THE PRESSURE GRADIENT... THOUGH SOME INCREASE
IN SPEED TO 20 KT SHOULD OCCUR BY TOMORROW AS THE SYSTEM PULLS
AWAY.

ATLANTIC OCEAN...
WELL-DEFINED UPPER LOW IS SW OF THE DEPRESSION NEAR 26N72W STILL
KEEPING A BIT OF SW SHEAR OVER THE SYSTEM.  FARTHER E...A DEEP
MID-OCEANIC TROUGH EXTENDS FROM A POWERFUL LOW NEAR 32N43W SW TO
A SECONDARY LOW DROPPING THRU THE AREA NEAR 23N55W CONTINUING S
TO 10N52W. A FEW TSTMS ARE FORMING IN MID/UPPER DIVERGENCE E OF
THE FIRST LOW WITHIN 60 NM OF 30N40W NEAR A WEAK SURFACE TROUGH
WITH ISOLATED SHOWERS N OF 30N BETWEEN 40W-48W BECAUSE OF
UNSTABLE AIR ALOFT NEAR THE LOW'S CORE.  OTHERWISE SURFACE HIGH
PRESSURE IS ENTRENCHED IN THE E ATLC VERY DRY AIR ALOFT AND
ENHANCED TRADES E OF 55W.  SURFACE RIDGE RUNS FROM 31N31W TO
21N61W THOUGH IS WEAKENED BY THE TROUGH NEAR 31N43W.  ELSEWHERE
IN THE DEEP TROPICS... MID/UPPER HIGH IS NEAR THE CAPE VERDES
RIDGING SW TO 10N50W WHERE IT MEETS THE MID-OCEANIC TROUGH.  W
OF THE TROUGH VERTICAL WIND SHEAR INCREASED ALONG WITH
LARGE-SCALE SUBSIDENCE CREATING A RATHER UNFAVORABLE ENVIRONMENT
FOR TROPICAL CYCLONES TO FORM.  MOISTURE HAS BEEN INCREASING IN
THE MID/UPPER LEVELS S OF 15N E OF 40W WITH LESS SUBSIDENCE/DRY
AIR NOTED ON WATER VAPOR THAN PREVIOUS DAYS... WHICH IS PROBABLY
RELATED TO AN INCREASE IN ITCZ TSTMS TODAY.

$$
BLAKE

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