[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 300005
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI JUL 29 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
2100 UTC.

...SPECIAL FEATURES...

TROPICAL STORM FRANKLIN CENTER NEAR 42.8N 58.9W...OR ABOUT 240
MILES SSE OF HALIFAX NOVA SCOTIA AND ABOUT 390 MILES SOUTHWEST
OF CAPE RACE NEWFOUNDLAND...AT 29/2100 UTC ACCELERATING
NORTHEAST AT 22 KT. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH
GUSTS TO 45 KT AND THE ESTIMATED MINIMUM CENTRAL PRESSURE IS
1003 MB.  SATELLITE IMAGERY INDICATES THAT FRANKLIN IS QUICKLY
BECOMING EXTRATROPICAL.  AS SUCH...THE NHC ISSUED ITS LAST
FORECAST/ADVISORY FOR FRANKLIN AT 2100 UTC UNDER AWIPS/WMO
HEADERS MIATCMAT1/WTNT21 KNHC AND/OR PUBLIC ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC.  SUBSEQUENT FORECAST
INFORMATION CAN BE OBTAINED IN HIGH SEAS FORECASTS ISSUED BY THE
OCEAN PREDICTION CENTER...UNDER AWIPS HEADER NFDHSFAT1 AND WMO
HEADER FZNT01 KWBC.

A VIGOROUS TROPICAL WAVE LOCATED OVER THE E CARIBBEAN AND
PORTIONS OF THE SW N ATLC OCEAN ALONG FROM 10N66W TO 23N61W
CONTINUES TO PRODUCE A LARGE AREA OF CLOUDINESS AND NUMEROUS
SHOWERS/TSTMS BETWEEN 16N-22N FROM PUERTO RICO EWD ACROSS THE
LEEWARD ISLANDS INTO THE ATLC WATERS TO 55W. A 1013 MB LOW PRES
CENTER CONTINUES TO BE ANALYZED ALONG THE WAVE AXIS NEAR 18N OR
JUST SE OF PUERTO RICO.  HOWEVER...DATA FROM AN EARLIER AIR
FORCE RESERVE UNIT RECONNAISSANCE MISSION INDICATED THAT A
CLOSED SURFACE CIRCULATION DID NOT EXIST.
NONETHELESS...ENVIRONMENTAL CONDITIONS STILL APPEAR GENERALLY
FAVORABLE AND SLOW DEVELOPMENT IS POSSIBLE OVER THE NEXT 24-36
HOURS. REGARDLESS OF DEVELOPMENT...SCATTERED SHOWERS AND STRONG
THUNDERSTORMS ACCOMPANIED BY HEAVY RAINFALL AND GUSTY WINDS WILL
CONTINUE TO AFFECT THE LEEWARD ISLANDS AND PUERTO THROUGH SAT.
THIS ACTIVITY WILL ALSO SPREAD OVER HISPANIOLA TONIGHT AND THE
TURKS/CAICOS/S BAHAMAS EARLY SAT.  INTEREST OVER THE N
CARIBBEAN...SW N ATLC...AND THE BAHAMAS SHOULD CONTINUE TO
CLOSELY MONITOR THE PROGRESS OF THIS SYSTEM.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE E ATLC ALONG 36W SOUTH OF 17N MOVING WEST
NEAR 15 KT.  A WEAK LOW TO MID-LEVEL VORTEX REMAINS VISIBLE IN
SATELLITE IMAGERY NEAR 10N/11N AS IS THE BASIS FOR THE WAVE
POSITION.  DEEP CONVECTION CONTINUES TO BE LIMITED OWING TO THE
DOMINANCE OF RELATIVELY DRY AIR ASSOCIATED WITH A LARGE
ELY/AFRICAN SURGE.

TROPICAL WAVE OVER THE CENTRAL ATLC ALONG 47W/48W SOUTH OF 17N
MOVING WEST NEAR 20 KT.  THE WAVE HAS BEEN OVERTAKEN BY THE
LEADING EDGE OF A LOW LEVEL ELY SURGE.  AS A RESULT...THE WAVE
REMAINS LOW AMPLITUDE AND CONVECTION IS LIMITED PRIMARILY TO THE
ITCZ. WIDELY SCATTERED MODERATE CONVECTION FROM 8N-14N BETWEEN
45W-51W.

TROPICAL WAVE OVER CENTRAL AMERICA NEAR GUATEMALA ALONG 90W
SOUTH OF 17N MOVING WEST NEAR 10 KT.  THIS WAVE CONTINUES TO
INTERACT FAVORABLY WITH A LARGE UPPER LOW OVER THE GLFMEX
PRODUCING SCATTERED SHOWERS AND STRONG TSTMS OVER MUCH OF
CENTRAL AMERICA AND S MEXICO FROM COSTA RICA WESTWARD TO THE
ISTHMUS OF TEHUANTEPEC.  THIS ACTIVITY WILL CONTINUE TO SPREAD
SLOWLY WESTWARD DURING THE NEXT 24 HOURS ACCOMPANIED BY LOCALLY
HEAVY RAINFALL.

...THE ITCZ...

ITCZ AXIS EMERGES OFF THE COAST OF W AFRICA NEAR 11N15W
EXTENDING WESTWARD ALONG 11N40W TO 9N60W CONTINUING WESTWARD
OVER N PORTIONS OF S AMERICA.  WIDELY SCATTERED SHOWERS AND
ISOLATED MODERATE CONVECTION WITHIN 500 NM S OF ITCZ E OF 52W.

...DISCUSSION...

GULF OF MEXICO...
A LARGE MID/UPPER LEVEL LOW CENTERED NEAR 22N93W CONTINUES TO
DOMINATE THE S HALF OF THE GULF WITH ASSOCIATED MODERATE
SUBSIDENCE AND DRY AIR ALOFT PRODUCING A RELATIVELY STABLE
ENVIRONMENT S OF 25N.  FURTHER N...A POTENT MIDDLE TO UPPER
LEVEL TROUGH CONTINUES TO DIG SEWD FROM THE OHIO VALLEY SW TO E
TEXAS.  ATTENDANT SURFACE COLD FRONT BECOME INCREASINGLY DIFFUSE
TODAY AS EMERGED INTO THE N GULF AND BECAME MODIFIED BY THE WARM
GULF WATERS.  HOWEVER...THE REMNANT FRONTAL TROUGH CONTINUES TO
PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS OVER THE SE UNITED
STATES WITH ISOLATED SHOWERS/THUNDERSTORMS OVER THE N GULF N OF
25N. THIS TROUGH WILL MOVE LITTLE DURING THE NEXT DAY OR SO AND
CONTINUE TO SPARK SHOWERS/TSTMS OVER THE N GULF THROUGH THE
WEEKEND...ESPECIALLY DURING THE PEAK AFTERNOON HEATING HOURS.
OVER FLORIDA...INCREASED INSTABILITY ASSOCIATED WITH A
RETROGRADING UPPER LOW JUST E OF MIAMI PRODUCED HIGHER THAN
NORMAL COVERAGE OF AFTERNOON SHOWERS/THUNDERSTORMS ACROSS THE
SUNSHINE STATE WITH SCATTERED ACTIVITY LINGERING INTO THE
EVENING HOURS ESPECIALLY OVER N FLORIDA.  EXPECT A CONTINUATION
OF HIGHER THAN NORMAL SHOWERS/THUNDERSTORMS AS THE UPPER TROUGH
CONTINUES TO PUSH WESTWARD PUTTING FLORIDA WITHIN A DIFFLUENT
PATTERN ALOFT.  AT THE SAME TIME...A LOW LEVEL ELY TROUGH
LOCATED OVER THE CENTRAL BAHAMAS WILL MOVE WESTWARD BRINGING
INCREASING LOW LEVEL CONVERGENCE AND MOISTURE.  BOTTOM LINE...A
WET/STORMY PATTERN WILL CONTINUE OVER FLORIDA THROUGH THE
WEEKEND.

CARIBBEAN SEA...
A PAIR OF TROPICAL WAVES...ONE OVER CENTRAL AMERICA AND THE
SECOND OVER THE E CARIBBEAN...ARE THE MAIN WEATHER MAKERS THIS
EVENING.  SHOWERS/TSTMS CONTINUE OVER ESSENTIALLY ALL OF CENTRAL
AMERICA THIS EVENING IN ASSOCIATION WITH A TROPICAL WAVE ALONG
90W.  THE WAVE AND ASSOCIATED MOISTURE WILL CONTINUE TO SPREAD
SLOWLY WESTWARD WITH GRADUALLY IMPROVING CONDITION OVER CENTRAL
AMERICA FROM EAST TO WEST AS MUCH DRIER AIR MOVES IN ON SAT.
FURTHER E...A STRONG TROPICAL WAVE NEARING PUERTO RICO IS
PRODUCING STRONG SHOWERS/THUNDERSTORMS N OF 17N E OF THE MONA
PASSAGE.  THIS ACTIVITY WILL BE SPREADING WESTWARD OVER THE N
CENTRAL CARIBBEAN AND HISPANIOLA TONIGHT AND SATURDAY.
ELSEWHERE...STRONG CONFLUENCE ALOFT IS PRODUCING SUBSIDENCE AND
DRY/STABLE CONDITIONS OVER THE CENTRAL CARIBBEAN FROM 70W TO 82W
WITH GENERALLY TRANQUIL WEATHER.  THIS AIRMASS WILL SLOWLY
TRANSITION WESTWARD OVER THE WEEKEND PRODUCING IMPROVING WEATHER
OVER THE W CARIBBEAN AND CENTRAL AMERICA.

ATLANTIC OCEAN...
AN UNUSUALLY HIGH-AMPLITUDE PATTERN ALOFT EXISTS OVER THE
SUBTROPICAL ATLANTIC WATERS COMPRISED OF A SHARP RIDGE OVER THE
W ATLC FROM N FLORIDA NEWD OVER BERMUDA TO BEYOND 35N60W AND A
PRONOUNCED MID-OCEANIC TROUGH EXTENDING FROM AN UPPER LOW NEAR
32N38W SW THROUGH 26N50W TO A SECOND UPPER LOW NEAR 25N65W
CONTINUING WESTWARD TO YET A THIRD UPPER LOW NEAR THE FLORIDA
STRAITS.  THE UPPER LOW NEAR 25N65W COUPLED WITH A STRONG
TROPICAL WAVE OVER THE E CARIBBEAN AND ATLC WATERS IS PRODUCING
A LARGE AREA OF SCATTERED MODERATE CONVECTION FROM 16N-23N
BETWEEN 50W-70W.  THIS UPPER LOW HAS BEEN PRODUCING SOME WLY
SHEAR OVER THIS AREA OF DISTURBED WEATHER LIMITING DEVELOPMENT.
HOWEVER...WATER VAPOR IMAGERY SUGGEST THAT THE UPPER LOW IS
BECOMING INCREASINGLY CUTOFF ALLOWING A SLIGHTLY FASTER WESTWARD
MOTION NOW ESTIMATED AT 15-20 KT. THIS MAY ALLOW FOR SOME
RELAXATION OF THE SHEAR POSSIBLY PERMITTING SOME SLOW
DEVELOPMENT OF THE TROPICAL WAVE OVER THE NEXT 24-36 HOURS.
REGARDLESS OF DEVELOPMENT...STRONG SHOWERS/TSTMS WILL CONTINUE
TO SPREAD WESTWARD AROUND THE S PERIPHERY OF A WELL-ESTABLISHED
AND STRONG LOW LEVEL RIDGE OVER THE W ATLC ALONG 32N AFFECTING
THE GREATER ANTILLES AND PORTIONS OF THE BAHAMAS.
ELSEWHERE...THE UPPER LOW OVER THE FLORIDA STRAITS COUPLED WITH
A LOW LEVEL ELY DISTURBANCE OVER THE CENTRAL BAHAMAS PRODUCED A
FAIRLY STORM AFTERNOON OVER MUCH OF THE BAHAMAS.  ACTIVITY HAS
SINCE WEAKENED WITH ONLY WIDELY SCATTERED SHOWERS AND A FEW
ISOLATED TSTMS LINGERING INTO THE EVENING HOURS.  THIS ACTIVITY
WILL SLOWLY TRANSITION WESTWARD DURING THE NEXT 24 HOURS
PRODUCING IMPROVED WEATHER SAT.  HOWEVER...SHOWERS/TSTMS WILL
ONCE AGAIN RETURN TO THE BAHAMAS LATE SAT AND SUN AS THE
AFOREMENTIONED TROPICAL WAVE APPROACHES.

$$
RHOME


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