[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 250619
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND
SATELLITE IMAGERY THROUGH 0345 UTC.

...SPECIAL FEATURE...
TROPICAL DEPRESSION DEVELOPED NEAR 11.2N 36.0W...OR ABOUT
870 MILES WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS...AT
25/0300 UTC MOVING WEST 15 KT. THE MAXIMUM SUSTAINED WIND
SPEED IS 25 KT GUSTS 35 KT. THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1009 MB. SEE THE LATEST NHC FORECAST/ADVISORY
ISSUED UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR
MORE DETAILS. SCATTERED STRONG SHOWERS AND THUNDERSTORMS
FROM 11N TO 13N BETWEEN 35W AND 38W. SCATTERED MODERATE TO
ISOLATED STRONG SHOWERS AND THUNDERSTORMS FROM 8N TO 11N
BETWEEN 37W AND 40W. THERE IS PRONOUNCED UPPER-LEVEL OUTFLOW
TO THE NORTH...EAST...AND SOUTH OF THE CENTER...BUT OUTFLOW
IS LIMITED TO THE EAST. ANALYSES FROM THE UNIVERSITY OF
WISCONSIN CIMSS INDICATE WEAK VERTICAL SHEAR ALONG THE PROJECTED
PATH OF THE CYCLONE TO ABOUT 50W LONGITUDE.  FARTHER WEST
AND NORTH...THE SHEAR MAY INCREASE AS SUGGESTED BY THE LATEST
200 MB FORECAST FROM THE GFS MODEL. THEREFORE STRENGTHENING MAY
BE INHIBITED LATE IN THE FORECAST PERIOD...ALTHOUGH THIS IS
HIGHLY UNCERTAIN. DYNAMICAL MODEL PREDICTIONS INDICATE A
WEAKENING OF THE MID-TROPOSPHERIC RIDGE TO THE NORTH OF THE
TROPICAL CYCLONE OVER THE NEXT SEVERAL DAYS...DUE TO THE
INCURSION OF A TROUGH INTO THE CENTRAL ATLANTIC. THIS TROUGH
IS AT RATHER HIGH LATITUDES HOWEVER...SO IT IS NOT LIKELY TO
PLAY A DIRECT ROLE IN STEERING THE TROPICAL CYCLONE.
NOTWITHSTANDING...THE TRACK GUIDANCE GENERALLY SHOWS A SLOWING
OF THE FORWARD SPEED AND A TURN TOWARD THE NORTHWEST LATER IN
THE FORECAST PERIOD.

...TROPICAL WAVES...
TROPICAL WAVE APPROXIMATELY 230 NM EAST OF BARBADOS ALONG
55W/56W SOUTH OF 19N MOVING WEST ABOUT 20 KT. ITCZ ISOLATED
MODERATE SHOWERS FROM 7.5N TO 11N WEST OF 48W. THIS AFRICAN
EASTERLY WAVE SHOULD REACH THE EASTERN CARIBBEAN SEA ISLANDS
DURING THE NEXT 24 HOURS.

...ITCZ...
ITCZ 14N17W 10N32W 8N39W 9N54W 9N63W. SCATTERED MODERATE TO
ISOLATED STRONG SHOWERS AND THUNDERSTORMS FROM 6N TO 8N BETWEEN
15W AND 18W. ISOLATED MODERATE TO LOCALLY STRONG SHOWERS AND
THUNDERSTORMS FROM 5N TO 7N 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. 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.

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. DIFFLUENT
FLOW ALONG THE RIDGE AXIS COUPLED WITH THE ITCZ OVER PANAMA IS
PRODUCING SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM
GUATEMALA TO PANAMA.

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.  OF A LINE FROM S FLORIDA TO
BERMUDA. EARLIER SHOWERS OVER THE BAHAMAS HAVE WEAKENED.
INSTABILITY ASSOCIATED WITH THE MID-OCEANIC TROUGH IS PRODUCING
WIDELY SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS N OF 25N
BETWEEN 53W AND 63W. 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.

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






This weather bulletin was brought to you by:
www.nashvilleweather.net