[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 071805
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU MAY 07 2009

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 5N10W 2N19W CROSSING THE EQUATOR
NEAR 24W AND CONTINUING S OF THE EQUATOR INTO NE BRAZIL NEAR
3S42W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
240 NM S OF THE AXIS BETWEEN 7W-10W. SIMILAR ACTIVITY IS ALONG
THE EQUATOR BETWEEN 41W-46W.

...DISCUSSION...

GULF OF MEXICO...
WEAK MID AND UPPER LEVEL TROUGHING IS JUST EXITING THE GULF WITH
THE TAIL END OF THE TROUGH EXTENDING FROM S CENTRAL FL SW TO THE
STRAITS OF FL. IN ITS WAKE...MODERATE SUBSIDENCE WITH ASSOCIATED
DRY STABLE AIR IN NW FLOW IS OBSERVED ACROSS THE GULF AS BROAD
MID/UPPER LEVEL RIDGING W OF THE AREA SPREADS EWD KEEPING
TRANQUIL CONDITIONS OVER THE GULF INTO THE WEEKEND. AT THE
SURFACE A RIDGE WAS ANALYZED ALONG 29N E OF 95W. LATEST VISIBLE
SATELLITE IMAGERY SHOWED GENERALLY MOSTLY CLEAR SKIES ACROSS THE
GULF WITH THE EXCEPTION OF UPPER TEXAS AND SW LOUISIANA COASTS
WHERE SCATTERED TO BROKEN LOW CLOUDS ARE BEING REPORTED. A FEW
THIN STRANDS OF HIGH CIRRUS CLOUDS ARE MOVING EWD ACROSS THE FAR
NRN PORTION OF THE NE GULF...WHILE A SMOKE PLUME FROM OVER SE
MEXICO AND THE SW YUCATAN PENINSULA IS NOTED OVER THE SW GULF
AND BAY OF CAMPECHE SW OF A LINE FROM FAR NE MEXICO TO CAMPECHE.
VISIBILITIES OF 5-7 SM ARE
BEING REPORTED BY MEXICAN REPORTING OBSERVATION SITES ALONG THE
COAST.

CARIBBEAN SEA...
WEAK MID/UPPER LEVEL TROUGH IS MOVING E ACROSS THE FAR N CENTRAL
PART OF THE SEA WHILE AT THE SAME TIME DAMPENING MID/UPPER LEVEL
RIDGING TO ITS SW ACROSS CENTRAL AMERICA IS CREATING BASICALLY
ZONAL FLOW OVER MUCH OF THE WRN AND CENTRAL CARIBBEAN. UPPER NW
FLOW FROM THE GULF INTO THE NW PORTION OF THE SEA MERGES WITH
THE ZONAL FLOW RESULTING IN UPPER LEVEL CONFLUENCE INTO THE BASE
OF THE TROUGH WITH SUBSIDENCE PROVIDING STABLE A ENVIRONMENT TO
THE CENTRAL AND WRN PORTIONS OF THE SEA. SCATTERED TO BROKEN
SMALL CUMULUS CLOUDS WITH BRIEF PASSING ISOLATED SHOWERS AND
WEAK ISOLATED TSTMS ARE NOTED OVER THE FAR WRN PORTION OF THE SW
CARIBBEAN TO ALONG AND JUST INLAND THE ADJACENT CENTRAL AMERICA.
TO THE E OF THE MID/UPPER LEVEL TROUGH...THE FLOW GRADUALLY
BECOMES DIFFLUENT WHILE AT THE SURFACE A WEAK TROUGH EXTENDS FROM
17N74W N TO ACROSS THE WINDWARD PASSAGE AND INTO THE SE BAHAMAS.
BOTH QUIKSCAT DATA AND BUOY OBSERVATIONS FROM THIS MORNING SHOWED
MODERATE E-SE FLOW TO THE E OF THE TROUGH AND LIGHTER NE-E FLOW
TO ITS W. THESE IS PRODUCING ENOUGH LOW-LEVEL SPEED CONVERGENCE
UNDER THE DIFFLUENCE TO TRIGGER OFF A PERSISTENT BAND OF
SCATTERED TO NUMEROUS SHOWERS AND TSTMS JUST S OF PUERTO RICO
AND THE DOMINICAN REPUBLIC. LATEST MODEL GUIDANCE SUGGESTS THAT
THIS ACTIVITY SHOULD PERSIST THROUGH THE WEEKEND...WITH LOCALLY
HEAVY AMOUNTS OF RAIN POSSIBLE...UNTIL THE MID/UPPER TROUGH
WEAKENS AS IT SLOWLY SHIFTS EWD INTO THE CENTRAL ATLC THROUGH
SAT. ELSEWHERE S OF THE SHOWER AND TSTM ACTIVITY...THE
ATMOSPHERE BECOMES DRY IN MODERATE SUBSIDENCE WITH VERY NARROW
STREAMERS OF SMALL CUMULUS WITH POSSIBLE ISOLATED LIGHT SHOWERS
EVIDENT S TO ABOUT 12N. CLEAR SKIES ARE SEEN S OF 12N.

ATLANTIC OCEAN...
THE REMAINDER OF THE MID/UPPER LEVEL TROUGH DESCRIBED UNDER
GULF OF MEXICO EXTENDS NE TO BEYOND THE AREA AT 32N76W. TO ITS
E...A MID/UPPER RIDGE EXTENDS FROM NEAR THE CENTRAL BAHAMAS
NE TO NE OF THE AREA AT 32N71W. A SHARPENING SHORTWAVE TROUGH
IS E OF THE RIDGE THROUGH 32N66W TO 25N67W. THE UPPER FLOW
BECOMES ZONAL E OF THIS TROUGH...THEN RESPONDS TO A BROAD DEEP
LAYER TROUGH OVER THE FAR ERN ATLC STRETCHING FROM 32N25W SW TO
NEAR 24N32W. AT THE SURFACE...A TROUGH EXTENDS FROM 26N73W S
THROUGH THE SE BAHAMAS AND INTO THE WINDWARD PASSAGE. SCATTERED
SHOWERS AND A FEW TSTMS ARE WITHIN 90 NM NE OF THE TROUGH WHICH
ARE ALSO ENHANCED BY THE MID/UPPER LEVEL TROUGH JUST TO THE W. A
TINY VORT MAX SPUN OFF FROM THE TROUGH IS RACING N NEAR 30N75W
WITH SCATTERED MODERATE CONVECTION WITHIN 45 NM OF IT. A 1030 MB
HIGH CENTER IS JUST N OF THE AREA NEAR 33N54W WITH A RIDGE WSW
TO 29N72W TO ACROSS NRN FL. PATCHES OF BROKEN LOW AND MID LEVEL
CLOUDS WITH EMBEDDED SCATTERED SHOWERS AN ISOLATED WEAK
CONVECTION ARE MOVING WWD IN MODERATE TO STRONG ESE FLOW S OF
THE RIDGE AND E OF THE SURFACE TROUGH TO NEAR 52W. SOME SIGNS OF
AFRICAN DUST/HAZE ARE NOTED OVER THE ERN ATLC S OF 25N E OF
56W...OTHERWISE THE ENVIRONMENT THERE REMAINS VERY SUPPRESSED
WITH JUST THE TYPICAL SCATTERED TO BROKEN STRATOCUMULUS CLOUD
FIELD PRESENT N OF THE ITCZ.

$$
AGUIRRE




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