[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 270531
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

AN ACTIVE TROPICAL WAVE IN THE W CARIBBEAN IS ALONG 84W FROM
9N-22N MOVING W NEAR 10 KT. A 1009 MB SURFACE LOW IS ALONG THE
WAVE AXIS NEAR 17.9N. LOW LEVEL CONVERGENCE NEAR THE SURFACE LOW
AND TROPICAL WAVE IS SUPPORTING SHOWERS AND THUNDERSTORMS OVER
PORTIONS OF THE W CARIBBEAN. IN PARTICULAR...NUMEROUS
MODERATE/SCATTERED STRONG CONVECTION IS FROM 14N-19N BETWEEN
80W-86W INCLUDING PORTIONS OF HONDURAS AND N NICARAGUA...AND
SCATTERED MODERATE TO STRONG CONVECTION IS FROM 10N-13N BETWEEN
80W-82W. ALL OF THIS CONVECTION IS ALSO BEING SUPPORTED BY
DIFFLUENT SOUTHERLY FLOW BETWEEN AN UPPER LEVEL RIDGE OVER THE
CENTRAL CARIBBEAN AND SE GULF OF MEXICO...AND AN UPPER LEVEL LOW
OVER THE SW 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 WILL CONTINUE
OVER PORTIONS OF CUBA AND HONDURAS THIS EVENING AND SPREAD
WESTWARD OVER NORTHERN CENTRAL AMERICA AND THE YUCATAN PENINSULA
OVER THE NEXT DAY OR SO.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 37W/38W S OF 13N MOVING W NEAR 10 KT
AND IS AFFECTING PORTIONS OF THE TROPICAL ATLC. THIS WAVE IS
NEAR THE LEADING EDGE OF AN ELONGATED MAXIMUM IN DEEP LAYER
MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM
CIMSS. COMPUTER MODEL GUIDANCE ALSO INDICATES THAT THIS WAVE IS
ASSOCIATED WITH LOW LEVEL CYCLONIC CIRCULATION. SCATTERED
MODERATE CONVECTION IS FROM 4N-11N BETWEEN 29W-38W.

A TROPICAL WAVE EXTENDS FROM 20N67W TO 17N68W TO 6N69W 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. THIS WAVE IS
ASSOCIATED WITH LOW LEVEL CYCLONIC CIRCULATION BASED ON THE
CIMSS WAVETRAK PRODUCT. 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 66W-69W INCLUDING PORTIONS OF
PUERTO RICO AND THE DOMINICAN REPUBLIC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 8N25W 5N35W 3N44W 2N51W.
SCATTERED MODERATE TO STRONG CONVECTION IS FROM 5N-12N BETWEEN
12W-25W. SCATTERED MODERATE CONVECTION IS FROM 5N-8N BETWEEN
50W-55W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL LOW IS CENTERED OVER THE BAY OF CAMPECHE NEAR
20N92W. ATMOSPHERIC INSTABILITY ASSOCIATED WITH THIS UPPER LEVEL
LOW IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS S OF 22N
BETWEEN 90W-92W INCLUDING PORTIONS OF THE YUCATAN PENINSULA.
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 AND ISOLATED THUNDERSTORMS FROM
24N-27N 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. SHOWERS AND THUNDERSTORMS OVER THE W
CARIBBEAN ARE ASSOCIATED WITH A TROPICAL WAVE ALONG 84W AND A
1009 MB SURFACE LOW ALONG THE WAVE AXIS NEAR 17.9N.
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 84W AND A 1009 MB SURFACE LOW ALONG
THE WAVE AXIS NEAR 17.9N. PLEASE SEE THE 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
NORTHERLY 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 27N BETWEEN 65W-68W. ALSO...UPPER LEVEL
DIFFLUENCE IN WESTERLY FLOW ALOFT AND DEEP LAYER MOISTURE ARE
SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS FROM 23N-27N
BETWEEN 76W-80W INCLUDING PORTIONS OF THE BAHAMAS AND E CUBA.
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
1025 MB SURFACE HIGH NEAR 33N47W AND A 1020 MB SURFACE HIGH NEAR
23N29W. HOWEVER...AN UPPER LEVEL TROUGH N OF 23N BETWEEN 17W-35W
IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 27N37W TO
30N24W TO 32N21W 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 AND ISOLATED THUNDERSTORMS FROM 20N-23N
BETWEEN 56W-59W. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE
AXIS EXTENDS FROM 17N16W TO AND UPPER LEVEL HIGH NEAR 15N36W TO
7N49W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THE UPPER LEVEL
HIGH AND UPPER LEVEL RIDGE IS SUPPORTING CONVECTION ASSOCIATED
WITH THE ITCZ AND THE TROPICAL WAVE ALONG 37W/38W S OF 13N.

$$
COHEN




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