[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 042334
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON JUL 04 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 FEATURES...

TROPICAL DEPRESSION THREE IS NEAR 22.8N 89.2W AT 2100 UTC ABOUT
435 MILES S OF THE MOUTH OF THE MISSISSIPPI RIVER MOVING NNW 10
KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1010 MB AND THE
MAXIMUM SUSTAINED WIND SPEED IS 30 KT GUSTING TO 40 KT. SEE THE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT3/WTNT23 KNHC AND/OR MIATCPAT3/WTNT33 KNHC FOR MORE
DETAILS.  THE UPPER ENVIRONMENT IS VERY FAVORABLE FOR FURTHER
DEVELOPMENT WITH AN ANTICYCLONE ALMOST SITTING RIGHT ON TOP OF
BROAD LOW-LEVEL CIRCULATION.  SCATTERED MODERATE TO ISOLATED
STRONG CONVECTION IS FROM 20N-25N BETWEEN 86W-90W.  A BAND OF
ISOLATED MODERATE CONVECTION IS FURTHER N FROM 25N-28N BETWEEN
85W-90W.

A STRONG TROPICAL WAVE LIES ACROSS THE LESSER ANTILLES WITH A
1011 MB LOW PRESSURE CENTER IN THE SOUTHERN WINDWARD ISLANDS
NEAR 12N62W MOVING W 15-20 KT.  PRESSURES CONTINUE TO FALL IN
THE AREA WITH WLY WINDS NOTED IN THE WINDWARDS S OF GRENADA AND
SE WINDS AT BARBADOS.  THERE ARE BANDING FEATURES ALL AROUND THE
LOW...AND FLOW ALOFT IS CONDUCIVE TO FURTHER DEVELOPMENT.
COMPUTER MODELS SUGGEST THIS WAVE HAS THE POTENTIAL TO
EVENTUALLY DEVELOP INTO A TROPICAL CYCLONE AS WIND SHEAR IS
FORECAST TO REMAIN WEAK DURING ITS TREK WESTWARD THROUGH THE
CARIBBEAN.  PRESENTLY...SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION IS FROM 11N-14N BETWEEN 60W-68W.  HEAVY RAIN IS
LIKELY ACROSS THE LESSER ANTILLES ESPECIALLY IN THE WINDWARD
ISLANDS FOR THE NEXT COUPLE DAYS WITH INCREASED MOISTURE NOTED S
OF 15N W OF 50W.

...TROPICAL WAVES...

E ATLC WAVE IS ALONG 21W S OF 18N MOVING W 10-15 KT.  THE
SOUNDING FROM DAKAR INDICATED THE WAVE PASSED LATE YESTERDAY.
SATELLITE PICTURES SHOW A LARGE CIRCULATION IN THE LOW CLOUDS
THOUGH THERE IS NO DEEP CONVECTION.

CENTRAL ATLC TROPICAL WAVE IS ALONG 46W S OF 16N MOVING W 15
KT.  THE WAVE IS NOT PARTICULARLY WELL-DEFINED WITH A SMALL
PROTRUSION NORTH OF THE ITCZ MARKING THE WAVE'S POSITION.
MOISTURE AND SHOWERS ASSOCIATED WITH THE WAVE IS FORECAST TO
REACH THE EASTERN CARIBBEAN ISLANDS BY LATE THU.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 14N16W 7N30W 8N50W 12N60W.
SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF 13N56W.
SCATTERED SHOWERS ARE WITHIN 90 NM OF THE ENTIRE ITCZ.

...DISCUSSION...

GULF OF MEXICO...
ATTENTION IS FOCUSED TO T.D. THREE OVER THE SOUTHERN GULF.  THE
PLAYERS IN THE STEERING OF THE CYCLONE ARE A MID/UPPER TROUGH
ALIGNED FROM SW LOUISIANA TO NE MEXICO AND A BUILDING MID/UPPER
HIGH WITH ONE CENTER OVER THE NW BAHAMAS AND ANOTHER CENTER NEAR
24N88W CLOSER TO THE DEPRESSION.  MOST MODEL GUIDANCE SUGGEST
THE TRACK WILL BE BETWEEN THE TROUGH AND THE HIGH WITH THE
CYCLONE GENERALLY STAYING UNDER LIGHT SHEAR FOR A DAY OR TWO
UNDER THE SW FLANK OF AN UPPER RIDGE.  THE NW GULF HAS
MODERATE/STRONG SUBSIDENCE ALOFT WHICH IS SUPPRESSING MOST
CONVECTION WHILE TYPICAL SEA-BREEZE CONVECTION HAS BEGUN IN
EARNEST OVER LOUISIANA EASTWARD THRU THE FLORIDA PANHANDLE.
CONDITIONS LOOK MUCH DRIER THAN AVERAGE IN S FLORIDA FOR THE
NEXT FEW DAYS AS SUBSIDENCE/RIDGING BUILDS IN THE WAKE OF THE
DEPRESSION.

CARIBBEAN SEA...
EFFECTS FROM THE T.D. ARE WANING AS THE SYSTEM PULLS OFF TO THE
NW.  A WET NIGHT IS EXPECTED OVER THE YUCATAN PENINSULA AND IN
THE FAR NW CARIBBEAN DUE TO LOW-LEVEL CONVERGENCE.  STRONG
SUBSIDENCE IS ASSOCIATED WITH AN INVERTED MID/UPPER TROUGH
MOVING QUICKLY WESTWARD NEAR CENTRAL AMERICA TO THE CAYMAN
ISLANDS.  THE DRY CONDITIONS W OF 70W ARE BEING QUICKLY ERODED
AWAY BY MOISTURE FROM THE ADVANCING TROPICAL WAVE IN THE FAR SE
CARIBBEAN.  INCREASING RAIN CHANCES ARE LIKELY FOR THE LEEWARD
ISLANDS OVERNIGHT INTO TOMORROW WITH THE BRUNT OF THE MOISTURE
REACHING HISPANIOLA BY WED.  THE WEATHER LOOKS QUITE WET IN THE
WINDWARD ISLANDS FOR AT LEAST THE NEXT 3 DAYS AS DEEP-LAYERED
MOISTURE IS FORECAST TO REMAIN HIGH.

ATLANTIC OCEAN...
LARGE 1033 MB HIGH NEAR 40N28W DOMINATES THE AREA EXCEPT FOR
TROPICAL WAVES ALONG ITS SOUTHERN PERIPHERY.  VERTICAL WIND
SHEAR IS MUCH BELOW AVERAGE EVERYWHERE ACROSS THE DEEP TROPICS S
OF 20N.. AIDING THE POSSIBLE DEVELOPMENT OF THE SE CARIBBEAN
WAVE.  IN THE UPPER LEVELS...UPPER RIDGING HAS BUILD ACROSS THE
W ATLC AS AN ANTICYCLONE IS POSITIONED NEAR THE NW BAHAMAS WITH
AN AXIS FROM CENTRAL FLORIDA TO BERMUDA.  A THIN TROUGH IS E OF
THE HIGH WITH THE TROUGH RUNNING FROM 30N46W SW THRU PUERTO
RICO.  A LITTLE BIT OF COOLER AIR ALOFT CONTINUES TO SUPPORT A
FEW TSTMS WITHIN 60 NM OF 27N58W.  OTHERWISE MID/UPPER RIDGING
CONTROLS THE CENTRAL ATLC WHILE A WEAK TROUGH DIPS INTO THE NE
ATLC NW OF THE CANARY ISLANDS.  STRONG SUBSIDENCE IS KEEPING THE
AREA NE ATLC RATHER DRY WITH THE TYPICAL SCATTERED TO BROKEN
STRATOCUMULUS OBSERVED.  FARTHER S...UPPER RIDGING COVERS THE
AREA WITH ONE ANTICYCLONE NEAR 15N55W AND THE OTHER ONE OVER NW
MAURITANIA.  THERE IS A WEAK INVERTED TROUGH BETWEEN THE RIDGES
ALONG 38W WITH MODERATE/STRONG SUBSIDENCE AND DRY AIR ALOFT FROM
THE CAPE VERDES TO 50W.  THE DEEP TROPICS ARE CONTROLLED BY
ANTICYCLONIC FLOW WITH RIDGING FROM W MAURITANIA TO THE SOUTHERN
LEEWARD ISLANDS.

$$
FORMOSA


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