Thursday Afternoon Tropical Weather Discussion

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU JUN 12 2008

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 MAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ADDED TO THE 1200 UTC ANALYSIS/SURFACE MAP ALONG 18W S OF 18N BASED ON VIS SATELLITE IMAGERY AND SFC DATA. IN ADDITION...THE SSMI-DERIVED TPW SHOWS A SURGE OF MOISTURE PROTRUDING NORTHWARD IN THIS AREA...AND THE DAKAR VERTICAL SOUNDING FROM THIS MORNING INDICATED THE PASSAGE OF THE WAVE AXIS WITH AN INCREASE IN MOISTURE AND SE WINDS AT LOW LEVELS. CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION ARE FROM 8N-12N WEST OF 20W TO THE AFRICAN COAST.

A TROPICAL WAVE IS ALONG 53W/54W S OF 15N MOVING W NEAR 15 KT. THE WAVE SHOWS UP VERY WELL ON THE UW-CIMSS TPW PRODUCT WITH A NORTH-SOUTH MOISTURE MAXIMUM. THE GFS MODEL 850 MB LOW-LEVEL VORTICITY ALSO SUPPORTS THE POSITION OF THE WAVE. SCATTERED MODERATE CONVECTION IS W OF THE WAVE AXIS FROM 9N-12N BETWEEN 54W-59W. MOISTURE FROM THIS WAVE WILL AFFECT THE WINDWARD ISLANDS LATE THIS AFTERNOON THROUGH FRI...SPREADING OVER THE UK/US VIRGIN ISLANDS AND PUERTO RICO LATER.

A WEAK TROPICAL WAVE IS OVER THE UK/US VIRGIN ISLAND EXTENDING SOUTH TO CENTRAL VENEZUELA. MOISTURE IS MAINLY BEHIND THE WAVE AXIS AFFECTING THE WINDWARD ISLANDS WITH SCATTERED SHOWERS AND ISOLATED TSTMS. BARBADOS REPORTED HEAVY SHOWERS AND GUSTY WINDS OF 30 KT YESTERDAY AFTERNOON WITH THE PASSAGE OF THE WAVE. THIS
SYSTEM STILL SHOWS UP WELL ON THE UW-CIMMS TPW PRODUCT WHERE A HIGH AMPLITUDE BULGE OF MOISTURE IS OBSERVED. THE WAVE WILL MOVE ACROSS PUERTO RICO LATE THIS AFTERNOON AND TONIGHT INCREASING THE CHANCES OF SHOWERS AND THUNDERSTORMS.

A TROPICAL WAVE IS OVER THE SW GULF OF MEXICO AND THE ISTHMUS OF TEHUANTEPEC ALONG 94W S OF 24N MOVING W NEAR 10 KT. WAVE REMAINS EMBEDDED WITHIN AN AREA OF DEEP LAYERED MOISTURE AS DEPICTED ON THE MIMIC-TPW ANIMATION. THE WAVE IS ALSO INTERACTING WITH AN UPPER-LEVEL LOW OVER THE CENTRAL GULF. AS A RESULT...THERE ARE TWO AREAS OF SCATTERED TO NUMEROUS SHOWERS AND TSTMS. ONE IS NEAR THE N END OF THE WAVE AXIS AND THE SECOND ONE IS FROM
24N-28N BETWEEN 85W-90W. THE CITY OF VERACRUZ REPORTED THIS MORNING 5.28 INCHES OF RAIN IN 24 HOURS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N14W 8N20W 3N35W 3N51W. BESIDES THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS NOTED WITHIN 160-200 NM N OF AXIS...AND WITHIN 100 NM S OF AXIS FROM 32W TO 45W.

...DISCUSSION...

GULF OF MEXICO...
AS PREVIOUSLY MENTIONED...THE COMBINATION OF A TROPICAL WAVE AND AN UPPER-LEVEL LOW CENTERED OVER THE CENTRAL GULF IS GENERATING ABUNDANT CLOUDINESS WITH EMBEDDED SHOWERS AND TSTMS OVER A GOOD PORTION OF THE REGION. SEE TROPICAL WAVE SECTION FOR DETAILS. A 1020 MB SFC HIGH REMAINS OVER THE W ATLANTIC NEAR 30N74W EXTENDING A RIDGE MAINLY OVER THE EASTERN PORTION OF THE GULF. PRES GRADIENT BETWEEN THE SFC HIGH AND THE TROPICAL WAVE IS PRODUCING MODERATE TO FRESH SE WINDS OVER PARTS OF THE CENTRAL
AND WESTERN GULF. THESE WINDS ARE EXPECTED TO DIMINISH FRI
AFTERNOON AND EVENING. ACCORDING TO THE GFS MODEL...CLOUDINESS AND SHOWER/TSTM ACTIVITY OVER THE GULF WILL MOVE NW TOWARD THE N GULF STATES IN ABOUT 24 HOURS UNDER A PREVAILING SE FLOW.

CARIBBEAN...
A TROPICAL WAVE IS OVER THE E CARIBBEAN AND A SECOND AND
STRONGER ONE IS APPROACHING THE WINDWARD ISLANDS. SEE TROPICAL WAVE SECTION. MODEL GUIDANCE SUGGESTS THAT THESE TWO TROPICAL WAVES WILL MERGE SOMETIME FRIDAY KEEPING A GOOD SURGE OF MOISTURE OVER THE EASTERN CARIBBEAN. ALSO...EXPECT AN INCREASE IN WINDS AND SEAS TO ACCOMPANY THE PASSAGE OF BOTH WAVES. IN THE MEANTIME...MODERATE TO FRESH TRADEWINDS ARE NOTED THROUGHOUT THE BASIN WITH THE STRONGEST WINDS...AS USUAL JUST OFF THE COLOMBIAN COAST WHERE AN EARLIER QSCAT PASS SHOWED ELY WINDS OF 25 KT. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS OVER THE SW CARIBBEAN ALONG THE COASTS OF PANAMA...COSTA RICA...AND
NICARAGUA...LIKELY DUE TO THE CLOSE PROXIMITY OF THE EPAC ITCZ AND A DIFFLUENT PATTERN ALOFT. IN THE UPPER LEVELS...MOSTLY WLY ZONAL FLOW IS NOTED WITH A FAIR AMOUNT OF UPPER LEVEL MOISTURE PARTICULARLY W OF 75W AND OVER THE FAR SE CARIBBEAN.

ATLANTIC...
A COUPLE OF UPPER-LEVEL LOWS PERSIST OVER THE W ATLC. ONE IS JUST N OF THE NW BAHAMAS NEAR 28N78W...AND CONTINUES TO ENHANCE TSTM ACTIVITY OVER THE STATE OF FLORIDA AND THE NW BAHAMAS. SIMILAR TO YESTERDAY...MOSAIC DOPPLER RADAR FROM THE SE INDICATES THAT STRONG TSTMS ARE FORMING OVER PARTS OF FLORIDA BUT MAINLY ON THE EASTERN SIDE AND NEAR LAKE OKEECHOBEE. THESE SLOW MOVING STORMS WILL BE CAPABLE OF HEAVY RAINFALL...GUSTY WINDS AND FREQUENT LIGHTNING. THE SECOND UPPER-LEVEL LOW IS NE OF PUERTO RICO NEAR 23N62W GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS. AT THE SFC...THE 1021 MB HIGH MENTIONED ABOVE DOMINATES THE AREA. A FRONTAL SYSTEM HAS ENTERED THE FORECAST AREA THROUGH THE CENTRAL ATLC AND NOW EXTENDS ALONG 31N35W 29N45W 30N58W. A BROKEN BAND OF LOW/MID CLOUDS WITH EMBEDDED SHOWERS IS ASSOCIATED WITH THE FRONT. BROAD UPPER-LEVEL TROUGH OVER THE CENTRAL ATLANTIC SUPPORTS THIS FRONT. A SFC RIDGE IS MAINLY SOUTH OF THE FRONTAL BOUNDARY COVERING THE FORECAST AREA EAST OF 50W. NEARLY ZONAL FLOW IS OVER THE E ATLANTIC N OF 20N AND E OF 30W. IN THE TROPICS...AN UPPER LEVEL HIGH IS CENTERED NEAR 14N48W WITH THE ANTICYCLONIC FLOW REACHING THE SE CARIBBEAN TO THE WEST AND THE CAPE VERDE ISLANDS TO THE EAST. THIS UPPER FEATURE IS ASSISTING IN THE DEVELOPMENT OF SHOWERS AND TSTMS RELATED TO THE ABOVE MENTIONED TROPICAL WAVES.


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