[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 301807
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT JUL 30 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 1200 UTC SURFACE ANALYSIS AND
SATELLITE IMAGERY THROUGH 1730 UTC.

...TROPICAL WAVES...

TROPICAL WAVE ALONG 40W SOUTH OF 18N MOVING WEST 15-20 KT. THE
WAVE IS DEFINED QUITE WELL ON SATELLITE IMAGERY BY A NORTHWARD
BULGE IN THE LOW AND MID LEVEL CLOUDS. SCATTERED MODERATE
CONVECTION IS IN A NARROW BAND FROM 12.5N-13.5N WEST OF THE WAVE
AXIS TO ABOUT 45W. CONVECTION REMAINS DISORGANIZED AS WAVE IS
EMBEDDED IN MID/UPPER LEVEL DRY AIR AND SUBSIDENCE ON THE EAST
SIDE OF A MID/UPPER LEVEL HIGH NEAR 16N52W.

TROPICAL WAVE ALONG 52W/53W SOUTH OF 18N MOVING WEST 20 KT.
CONVECTION ASSOCIATED WITH THIS WAVE IS QUITE ACTIVE...WITH
HIGH RESOLUTION VISIBLE SATELLITE IMAGERY INDICATES A WEAK LOW
LEVEL CIRCULATION NEAR 11N52W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION EXTENDS FROM 10N-14N ALONG AND W OF THE WAVE
AXIS TO 57W. SURFACE OBSERVATIONS SHOW THAT THE WAVE IS AT THE
LEADING EDGE OF A WIND SURGE...WITH WINDS OF 20-25 KT BEHIND THE
WAVE AND 10-15 KT WINDS AHEAD OF THE WAVE NEAR AND OVER THE
LESSER ANTILLES. HOWEVER...LITTLE IN THE WAY OF ORGANIZATION IS
NOTED. CONDITIONS MAY BECOME SOMEWHAT FAVORABLE FOR DEVELOPMENT
DURING THE NEXT 24 HOURS AS THE WAVE MOVES AROUND THE SOUTHERN
PERIPHERY OF THE MID/UPPER LEVEL HIGH NEAR 16N52W. ON ITS
CURRENT MOTION...SHOWERS AND TSTMS WILL BEGIN TO AFFECT THE
WINDWARD ISLANDS LATE TONIGHT OR EARLY SUN WITH GUSTY WINDS AND
LOCALLY HEAVY RAINS.

A WELL-DEFINED TROPICAL WAVE EXTENDS FROM THE ATLANTIC NEAR
22N67W SOUTH ACROSS THE EASTERN DOMINICAN REPUBLIC TO 8N70W
MOVING WEST 15-20 KT. SATELLITE IMAGERY...SURFACE OBSERVATIONS...
AND QUIKSCAT DATA SHOW THE POSITION OF THE WAVE QUITE WELL.
SCATTERED STRONG CONVECTION 120-150 W OF THE WAVE AND S OF
HISPANIOLA HAS DISSIPATED IN THE LAST FEW HOURS...WITH SIMILAR
CONVECTION DEVELOPING OVER THE DOMINICAN REPUBLIC DUE IN PART TO
DIURNAL HEATING. SATELLITE RAINFALL ESTIMATES INDICATE AMOUNTS
OF 4 INCHES ARE POSSIBLE OVER THIS AREA. LARGE AREA OF SCATTERED
MODERATE CONVECTION EXTENDS E FROM THE WAVE OVER ATLANTIC FROM N
COAST OF PUERTO RICO TO 22N AS FAR E AS 59W. WAVE IS UNDERNEATH
AN AREA OF S-SW UPPER LEVEL WINDS WHICH IS PRODUCING A
MARGINALLY UNFAVORABLE ENVIRONMENT FOR DEVELOPMENT. HEAVY RAINS
WILL CONTINUE TO SPREAD WEST ACROSS HISPANIOLA DURING THE NEXT
24 HOURS.

TROPICAL WAVE PREVIOUSLY INLAND OVER THE ISTHMUS OF TEHUANTEPEC
IS NOW MAINLY OVER THE PACIFIC WATERS SOUTH OF THE GULF OF
TEHUANTEPEC.

...ITCZ...

ITCZ AXIS ALONG 10N13W 7N30W 10N39W 9N50W 8N61W. RELATIVELY
LITTLE IN THE WAY OF CONVECTION ALONG THE ITCZ...WITH SCATTERED
MODERATE CONVECTION WITHIN 120 NM OF AXIS E OF 18W TO THE
AFRICAN COAST...WITHIN 60 NM OF AXIS BETWEEN 26W-33W...AND
WITHIN 60 NM OF AXIS BETWEEN 46W-56W.

...DISCUSSION...
GULF OF MEXICO...
MID/UPPER LEVEL LONGWAVE TROUGH EXTENDS OVER THE LOWER
MISSISSIPPI VALLEY TO THE EXTREME NW GULF OFF THE WESTERN
LOUISIANA COAST. WATER VAPOR IMAGERY INDICATES DRY AIR AND
SUBSIDENCE OVER THE COASTAL WATERS OF WESTERN LOUISIANA AND
UPPER TEXAS COAST...LIMITING CONVECTION IN THESE AREAS. A
SURFACE LOW IS OVER THE NORTHERN GULF JUST S OF ALABAMA COAST
NEAR 28N87W 1015 MB...WITH A TROUGH EXTENDING FROM NORTH FLORIDA
NEAR TALLAHASSEE SW TO 26N89W. RADAR DATA INDICATE NUMEROUS
SHOWERS AND TSTMS OVER THE NE GULF FROM THE FLORIDA BIG BEND
AREA WEST TO THE COASTAL WATERS OF ALABAMA...MISSISSIPPI...AND
SE LOUISIANA. WESTERN END OF UPPER LEVEL RIDGE OVER THE NE GULF
IS PROVIDING UPPER LEVEL DIFFLUENCE OVER THIS AREA TO HELP
SUPPORT THE SHOWERS AND TSTMS. FARTHER S...A SMALL MID/UPPER LOW
OVER EXTREME S FLORIDA AND THE SE GULF IS INTERACTING WITH A
SURFACE TROUGH JUST WEST OF THE FLORIDA KEYS TO CAUSE SCATTERED
SHOWERS AND TSTMS OVER S FLORIDA AND THE SE GULF. UPPER LEVEL
LOW OVER THE SW GULF CENTERED 21N94W IS DRIFTING W TOWARDS THE
MEXICO COAST...WITH LITTLE CONVECTION OVER THE SW GULF DUE TO
MAINLY DRY AIR ALOFT. THESE FEATURES WILL CHANGE LITTLE OVER THE
NEXT 24 HOURS...KEEPING THE EASTERN HALF OF THE GULF AND MUCH OF
FLORIDA UNDER THE THREAT OF SHOWERS/TSTMS.

CARIBBEAN SEA...
MID/UPPER LEVEL HIGH OVER NORTHERN HONDURAS IS PRODUCING
ANTICYCLONIC AND MAINLY DRY FLOW OVER MOST OF WESTERN CARIBBEAN
SEA. AT THE OTHER END OF THE BASIN...A MID/UPPER LEVEL RIDGE
EXTENDS W ALONG 15N FROM A HIGH E OF THE ISLANDS NEAR 16N52W.
BETWEEN THESE TWO HIGHS IS A SMALL MID/UPPER LEVEL LOW S OF
HAITI NEAR 15N73W. WHILE THE W CARIBBEAN REMAINS MOSTLY
DRY...THE E CARIBBEAN IS SEEING AN INFLUX OF DEEP TROPICAL
MOISTURE AS SOUTHERLY FLOW FROM SOUTH AMERICA EXTENDS ALL THE N
THROUGH HISPANIOLA AND PUERTO RICO. THESE SOUTHERLY WINDS ALOFT
ARE ALSO PROVIDING MARGINALLY UNFAVORABLE CONDITIONS FOR
DEVELOPMENT OF THE WAVE NEAR 70W. SHOWERS AND TSTMS WILL
CONTINUE TO SPREAD W ACROSS THE CENTRAL CARIBBEAN AS THE WAVE
MOVES ACROSS HISPANIOLA AND TOWARDS E CUBA AND JAMAICA. SHOWERS
AND TSTMS WILL ALSO INCREASE OVER THE E CARIBBEAN AHEAD OF THE
TROPICAL WAVE APPROACHING THE LESSER ANTILLES.

ATLANTIC OCEAN...
SUBTROPICAL RIDGE IS CONFINED TO NW CORNER OF AREA AS LARGE
MID/UPPER LEVEL LOW CENTERED NEAR 26N68W MOVES WEST 15 KT.
SCATTERED SHOWERS AND TSTMS ARE OVER THE NW BAHAMAS AND FLORIDA
COASTAL WATERS NEAR THE EASTERN EDGE OF THE SURFACE TROUGH OVER
EXTREME S FLORIDA. FARTHER E...LARGE MID/UPPER LEVEL HIGH E OF
THE LESSER ANTILLES NEAR 16N52W HAS A RIDGE WHICH EXTENDS NW TO
28N58W. DIFFLUENT S-SW FLOW BETWEEN THIS HIGH AND THE LOW NEAR
26N68W IS SUPPORTING SHOWERS/TSTMS ALONG AND E OF THE TROPICAL
WAVE NEAR HISPANIOLA. OVER THE EASTERN ATLANTIC...LARGE
MID/UPPER LOW IS NEAR 29N41W WITH A SURFACE LOW NEAR 29.5N46W
1019 MB. SCATTERED MODERATE CONVECTION IS IN CLUSTERS N OF 25N
ON EITHER SIDE OF THE MID/UPPER LOW BETWEEN 33W-45W. REST OF
EASTERN ATLANTIC IS CONTROLLED BY MID/UPPER LEVEL HIGH CENTERED
NEAR 20N27W. VISIBLE IMAGERY INDICATES A LARGE AREA OF SAHARAN
DUST FROM 8N-22N E OF 32W.

$$
MOLLEDA


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