[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 271050
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT JUN 27 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1045 UTC.

...SPECIAL FEATURES...

AN ACTIVE TROPICAL WAVE IN THE W CARIBBEAN IS ALONG 86W/87W S OF
23N MOVING W 10-15 KT. LOW LEVEL CONVERGENCE NEAR THE TROPICAL
WAVE IS SUPPORTING SHOWERS AND THUNDERSTORMS OVER PORTIONS OF
THE W CARIBBEAN. IN PARTICULAR...NUMEROUS MODERATE/SCATTERED
STRONG CONVECTION IS FROM 17N-22N BETWEEN 79W-84W AND FROM
18N-20N BETWEEN 85W-87W. ALL OF THIS CONVECTION IS ALSO BEING
SUPPORTED BY UPPER LEVEL DIVERGENCE W OF AN UPPER LEVEL RIDGE
OVER THE CENTRAL CARIBBEAN AND SE GULF OF MEXICO... AS WELL AS
THE PRESENCE OF ABUNDANT DEEP LAYER MOISTURE. SIGNIFICANT
DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED BEFORE IT REACHES THE
YUCATAN PENINSULA LATER TODAY. HOWEVER... ENVIRONMENTAL
CONDITIONS COULD BECOME FAVORABLE FOR DEVELOPMENT ONCE THE
SYSTEM EMERGES INTO THE SOUTHERN GULF OF MEXICO TONIGHT OR
SUNDAY. THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
MEANWHILE...LOCALLY HEAVY RAINS ARE POSSIBLE OVER PORTIONS OF
WESTERN CUBA AND HONDURAS TODAY AND COULD SPREAD WESTWARD INTO
NORTHERN CENTRAL AMERICA AND THE YUCATAN PENINSULA DURING THE
NEXT DAY OR SO.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 13N37W TO 6N38W TO 1N39W MOVING W
NEAR 10 KT AND IS AFFECTING PORTIONS OF THE TROPICAL ATLC. THIS
WAVE IS ANALYZED NEAR THE LEADING EDGE OF AN ELONGATED MAXIMUM
IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER
PRODUCT FROM CIMSS. THE CIMSS WAVETRAK PRODUCT INDICATES THAT
THIS WAVE IS ASSOCIATED WITH AN AREA OF WEAK LOW LEVEL CYCLONIC
CIRCULATION. SCATTERED MODERATE CONVECTION IS FROM 2N-8N BETWEEN
33W-38W. COMPUTER MODEL GUIDANCE SUGGESTS THAT AN AREA OF
STRONGER LOW LEVEL CYCLONIC CIRCULATION IS EMBEDDED FARTHER
EASTWARD INTO THE ELONGATED DEEP LAYER MOISTURE MAXIMUM...
APPROXIMATELY ALONG 29W S OF 9N. THIS AREA WILL CONTINUE TO BE
MONITORED FOR THE PRESENCE OF A TROPICAL WAVE.

A TROPICAL WAVE IS ALONG 69W/70W S OF 20N MOVING W 10-15 KT AND
IS AFFECTING PORTIONS OF THE E CARIBBEAN. THIS WAVE IS ALSO
ASSOCIATED WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE
TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. THE PRESENCE OF DRY
LOW/MID-LEVEL SAHARAN AIR OVER PORTIONS OF THE E CARIBBEAN IS
INHIBITING DEEP CONVECTION NEAR THIS WAVE. HOWEVER...SCATTERED
SHOWERS ARE OCCURRING FROM 16N-18N BETWEEN 68W-71W INCLUDING
PORTIONS OF HISPANIOLA.

AN ACTIVE TROPICAL WAVE IS ALONG 86W/87W S OF 23N MOVING W 10-15
KT AND IS AFFECTING PORTIONS OF THE W CARIBBEAN. THE 1009 MB
SURFACE LOW PREVIOUSLY ANALYZED ALONG THIS WAVE NEAR 17.9N84W AT
27/0000 UTC HAS BEEN REMOVED FOR THE 27/0600 UTC SURFACE
ANALYSIS DUE TO THE ABSENCE OF A CLOSED CIRCULATION IN THIS AREA
BASED ON THE 27/0240 UTC ASCAT PASS. THIS WAVE AND ITS
ASSOCIATED CONVECTION IS DISCUSSED IN THE SPECIAL FEATURES
SECTION ABOVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 8N25W 8N35W 7N45W 5N54W.
SCATTERED MODERATE TO STRONG CONVECTION IS FROM 5N-11N BETWEEN
10W-23W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
6N-9N BETWEEN 23W-28W. SCATTERED MODERATE CONVECTION IS FROM
5N-8N BETWEEN 51W-59W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL LOW IS CENTERED OVER THE BAY OF CAMPECHE NEAR
21N93W. ATMOSPHERIC INSTABILITY ASSOCIATED WITH THIS UPPER LEVEL
LOW IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS S OF 21N W
OF 93W. ALSO...DIFFLUENT SOUTHERLY FLOW ALOFT BETWEEN THE
AFOREMENTIONED UPPER LEVEL LOW AND AN UPPER LEVEL RIDGE OVER THE
SE GULF AND CENTRAL CARIBBEAN...AS WELL AS DEEP LAYER
MOISTURE...ARE SUPPORTING SCATTERED SHOWERS FROM 22N-24N BETWEEN
83W-87W. ELSEWHERE ACROSS THE N AND W GULF...SUBSIDENCE IN NE
FLOW ALOFT BETWEEN AN UPPER LEVEL HIGH OVER N TEXAS AND THE
AFOREMENTIONED UPPER LEVEL LOW OVER THE BAY OF CAMPECHE...AS
WELL AS DEEP LAYER DRY AIR...ARE RESULTING IN GENERALLY FAIR
WEATHER. HOWEVER...UPPER LEVEL MOISTURE STREAMING SOUTHWESTWARD
AROUND THE UPPER HIGH IS SUPPORTING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ACROSS THE N GULF N OF 27N BETWEEN
89W-93W. SHOWERS AND THUNDERSTORMS OVER THE W CARIBBEAN ARE
ASSOCIATED WITH A TROPICAL WAVE ALONG 86W/87W. ENVIRONMENTAL
CONDITIONS COULD BECOME FAVORABLE FOR DEVELOPMENT ONCE THE
SYSTEM EMERGES INTO THE SOUTHERN GULF OF MEXICO TONIGHT OR
SUNDAY.

CARIBBEAN SEA...
SHOWERS AND THUNDERSTORMS OVER THE W CARIBBEAN ARE ASSOCIATED
WITH A TROPICAL WAVE ALONG 86W/87W. PLEASE SEE THE TROPICAL
WAVES SECTION AND SPECIAL FEATURES SECTION ABOVE FOR MORE
INFORMATION ON THIS SYSTEM. ACROSS THE CENTRAL CARIBBEAN...AN
UPPER LEVEL RIDGE IS PRESENT...WITH SUBSIDENCE AND ATMOSPHERIC
STABILITY SUPPORTING GENERALLY FAIR WEATHER ACROSS MUCH OF THE
CENTRAL CARIBBEAN. ACROSS THE E CARIBBEAN...DEEP LAYER DRY
AIR...SUBSIDENCE DUE TO CONFLUENT NORTHWESTERLY FLOW ALOFT...AND
THE PRESENCE OF LOW/MID-LEVEL DRY SAHARAN AIR ARE RESULTING IN
GENERALLY FAIR WEATHER.

ATLANTIC OCEAN...
ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL TROUGH
OVER THE SW NORTH ATLC IS SUPPORTING SCATTERED SHOWERS AND
THUNDERSTORMS N OF 25N BETWEEN 66W-78W. ALSO...ATMOSPHERIC LIFT
IN MOIST SOUTHWESTERLY FLOW ALOFT IS SUPPORTING SCATTERED
SHOWERS AND THUNDERSTORMS N OF 26N BETWEEN 60W-66W. THIS
ACTIVITY IS ALSO BEING SUPPORTED BY LOW LEVEL CONVERGENCE NEAR A
SURFACE TROUGH THAT EXTENDS FROM 31N62W TO 32N61W TO NE OF THE
DISCUSSION AREA. FARTHER TO THE E...GENERALLY FAIR WEATHER IS
PRESENT ACROSS MUCH OF THE CENTRAL AND E ATLC...WHERE SUBSIDENCE
IS OCCURRING NEAR A BROAD SURFACE RIDGE. THIS SURFACE RIDGE IS
ASSOCIATED WITH A 1023 MB SURFACE HIGH NEAR 32N46W AND A 1019 MB
SURFACE HIGH NEAR 22N29W. HOWEVER...AN UPPER LEVEL TROUGH N OF
23N BETWEEN 19W-31W IS SUPPORTING A SURFACE TROUGH THAT EXTENDS
FROM 27N35W TO 30N25W TO 32N22W TO NE OF THE DISCUSSION AREA.
LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS WITHIN 60
NM EITHER SIDE OF THE SURFACE TROUGH. ALSO...ATMOSPHERIC
INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW NEAR 22N53W IS
SUPPORTING SCATTERED SHOWERS FROM 19N-22N BETWEEN 56W-60W.
ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE AXIS EXTENDS
FROM 17N15W TO AN UPPER LEVEL HIGH NEAR 16N36W TO 6N49W. UPPER
LEVEL DIVERGENCE ASSOCIATED WITH THE UPPER LEVEL HIGH AND UPPER
LEVEL RIDGE IS SUPPORTING CONVECTION ASSOCIATED WITH THE ITCZ
AND THE TROPICAL WAVE THAT EXTENDS FROM 13N37W TO 6N38W TO 1N39W.

$$
COHEN




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