[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 251059
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED 25 AUG 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN 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 0600 UTC SURFACE ANALYSIS AND
SATELLITE IMAGERY THROUGH 1015 UTC.

...SPECIAL FEATURE...
TROPICAL DEPRESSION SIX CENTER NEAR 11.4N 37.6W...OR ABOUT
1615 MILES EAST OF THE LESSER ANTILLES...AT 25/0900 UTC MOVING
WEST 15 KT. THE MAXIMUM SUSTAINED WIND SPEED IS 30 KT GUSTS
40 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB. SEE
THE LATEST NHC FORECAST/ADVISORY ISSUED UNDER AWIPS/WMO HEADERS
MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. WIDELY SCATTERED MODERATE
TO ISOLATED STRONG SHOWERS AND THUNDERSTORMS WITHIN 50 NM ON
EITHER SIDE OF 15N37W 12N39W 9N40W. IR IMAGERY INDICATES THAT
THE TROPICAL DEPRESSION IS GRADUALLY BECOMING BETTER ORGANIZED.
DEEP CONVECTION HAS INCREASED A LITTLE...PRIMARILY IN A CURVED
BAND TO THE NORTH...AND THE OUTFLOW IS ESTABLISHED EVERYWHERE
BUT TO THE EAST OF THE CENTER. IT IS LIKELY THAT T.D. SIX WILL
STRENGTHEN SINCE IT IS EXPECTED TO BE EMBEDDED WITHIN A
FAVORABLE ENVIRONMENT OF LOW SHEAR AND WARM SEA SURFACE
TEMPERATURES FOR THE NEXT 2 TO 3 DAYS. THE CYCLONE SHOULD
ENCOUNTER SOME SHEAR AFTER THAT...AS SUGGESTED BY SOME OF THE
COMPUTER MODELS. THE SHEAR IS NOT EXPECTED TO BE STRONG ENOUGH
TO HINDER SLOW STRENGTHENING. THE CYCLONE IS SOUTH OF A STRONG
SUBTROPICAL RIDGE BUT UNANIMOUSLY...ALL GLOBAL MODELS WEAKEN
THE RIDGE AS A MID-LATITUDE TROUGH MOVES EASTWARD ACROSS THE
ATLANTIC.

...TROPICAL WAVES...
TROPICAL WAVE ALONG 57W SOUTH OF 19N MOVING WEST ABOUT 20 KT.
ITCZ ISOLATED MODERATE SHOWERS FROM 8N TO 10N WEST OF 50W.
THIS AFRICAN EASTERLY WAVE SHOULD REACH THE EASTERN CARIBBEAN
SEA ISLANDS DURING THE NEXT 24 HOURS.

...ITCZ...
ITCZ 14N17W 10N32W 8N39W 9N54W 9N63W. ISOLATED MODERATE TO
LOCALLY STRONG SHOWERS AND THUNDERSTORMS FROM 10N TO 12N
BETWEEN 60W AND 64W. WIDELY SCATTERED TO SCATTERED MODERATE/
ISOLATED STRONG SHOWERS AND THUNDERSTORMS FROM 6N TO 10N BETWEEN
AFRICA COAST AND 20W...AND FROM 6N TO 8N BETWEEN 20W AND 30W.

...DISCUSSION...

THE GULF OF MEXICO...
THE GULF OF MEXICO FEATURES STRONG MIDDLE TO UPPER LEVEL RIDGING
FROM SOUTH TEXAS EAST-SOUTHEASTWARD TO WESTERN CUBA. ISOLATED
MODERATE SHOWERS AND THUNDERSTORMS...EAST OF 22N87W 30N85W...
ARE ASSOCIATED WITH THE TAIL END OF AN UNITED STATES EAST COAST
DEEP LAYER TROUGH WHICH REACHES 25N84W. THE SOUTHERN END OF A
SURFACE STATIONARY FRONT REACHES 31N79W IN THE ATLANTIC OCEAN.
SURFACE TROUGH CONTINUES FROM 31N79W TO NORTHEASTERN FLORIDA...
TO THE FLORIDA WEST COAST NEAR 29N83W...INTO THE GULF OF MEXICO
NEAR 27N87W. A RETROGRADING MIDDLE TO UPPER LEVEL CYCLONIC
CIRCULATION CENTER IN WEST CENTRAL MEXICO NEAR 21N105W IS
TAPPING INTO SOME EAST PACIFIC MOISTURE AND PRODUCING SCATTERED
STRONG SHOWERS AND THUNDERSTORMS OVER THE ISTHMUS OF TEHUANTEPEC
AND ADJACENT SOUTHWEST GULF WATERS SOUTH OF 21N WEST OF 94W.
ELSEWHERE...MOISTURE AND DYNAMICS ARE LIMITED WITH CONFLUENT
FLOW S OF THE UPPER RIDGE AXIS PRODUCING DRY/TRANQUIL WEATHER.
THE SURFACE SUBTROPICAL RIDGE GOES FROM THE BAHAMAS TO THE
WATERS JUST NORTH OF THE YUCATAN PENINSULA TO THE MEXICO COAST
NEAR 22N. ISOLATED MODERATE TO LOCALLY STRONG SHOWERS AND
THUNDERSTORMS NORTH OF 24N EAST OF 86W. NUMEROUS STRONG SHOWERS
AND THUNDERSTORMS OFF THE FLORIDA EAST COAST FROM 27N TO 31N
BETWEEN 77W AND THE UNITED STATES COAST...FROM FLORIDA TO
GEORGIA.

THE CARIBBEAN SEA...
MID-OCEANIC TROUGH EXTENDS FROM THE CENTRAL ATLANTIC OCEAN
TO HISPANIOLA TO AN UPPER LEVEL CYCLONIC CIRCULATION CENTER NEAR
17N75W...CONTINUING WEST TO BELIZE. INSTABILITY ASSOCIATED WITH
THE UPPER TROUGH IS PRODUCING ENHANCED SHOWER/THUNDERSTORM
ACTIVITY FROM THE MONA PASSAGE TO CUBA AND THE CAYMAN ISLANDS.
TO THE SOUTH OF THE TROUGH...MODERATE SUBSIDENCE AND DRY AIR
BLANKETS THE AREA TO SOUTH AND CENTRAL AMERICA WHERE A MID/UPPER
LEVEL RIDGE EXTENDS FROM S MEXICO SEWD INTO COLOMBIA. NUMEROUS
STRONG...POSSIBLY ITCZ-RELATED...SHOWERS AND THUNDERSTORMS
IN THE SOUTHWEST CORNER FROM 10N TO 12N BETWEEN 77W AND 81W.

SUBTROPICAL ATLANTIC OCEAN...
THE SUBTROPICAL ATLC FEATURES A LARGE SCALE RIDGE-TROUGH-RIDGE
PATTERN WITH A RIDGE OVER THE W ATLC EXTENDING FROM S FLORIDA
NEWD OVER BERMUDA...MID-OCEANIC TROUGH EXTENDING FROM 30N56W TO
HISPANIOLA...AND BROAD E/W ORIENTED RIDGE OVER THE E ATLC ALONG
18N.  SIGNIFICANT PRECIPITATION IS FOCUSED PRIMARILY OVER THE
WESTERN HALF OF THE ATLANTIC IN ASSOCIATION WITH THE SOUTHERN
END OF AN UNITED STATES TROUGH. INSTABILITY ASSOCIATED WITH THE
MID-OCEANIC TROUGH IS PRODUCING WIDELY SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS N OF 25N BETWEEN 54W AND 68W. ELSEWHERE
OVER THE E ATLC...UPSTREAM MOISTURE IS RIDING UP AND OVER THE E
ATLC RIDGE LEAVING THE AREA EAST OF 50W UNDER CONFLUENT FLOW AND
DRY AIR. SURFACE SUBTROPICAL RIDGE ENTERS THE CENTRAL ATLC ALONG
33N475W TO 28N65W TO THE BAHAMAS. SURFACE TROUGH ALONG 29N44W TO
25N46W TO 18N48W...ISOLATED MODERATE SHOWERS AND THUNDERSTORMS
FROM 25N TO 30N BETWEEN 48W AND 50W.

TROPICAL ATLANTIC...
THE MAJOR FEATURE OVER THE TROPICAL EASTERN ATLANTIC IS TROPICAL
DEPRESSION SIX. A MIDDLE TO UPPER LEVEL RIDGE POSITIONED NORTH
OF THE WAVE ALONG 18N IS PRODUCING DEEP LAYERED EASTERLY WIND
FLOW OVER THE TROPICAL ATLANTIC AND PROVIDING A FAVORABLE
ENVIRONMENT FOR DEVELOPMENT.  A NEW TROPICAL WAVE EMERGING OFF
THE WEST COAST OF AFRICA IS PRODUCING ENHANCED ITCZ SHOWERS AND
THUNDERSTORMS EAST OF 20W. ELSEWHERE...MODERATE SUBSIDENCE AND
DRY AIR PREVAIL LIMITING SIGNIFICANT ACTIVITY.

$$
MT







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