[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 271728
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1645 UTC.

...SPECIAL FEATURES...

AN ACTIVE TROPICAL WAVE IN THE FAR W CARIBBEAN EXTENDING FROM
21N86W TO 5N88W MOVG W 10-15 KT. LOW LEVEL CONVERGENCE NEAR THE
WAVE IS SUPPORTING DISORGANIZED SHOWERS AND THUNDERSTORMS FROM
CUBA AND THE CAYMAN ISLANDS WESTWARD TO THE YUCATAN PENINSULA.
IN PARTICULAR...NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS
FROM 17N-21N BETWEEN 84W-88W. SCATTERED MODERATE CONVECTION IS
FROM 20N-23N BETWEEN 78W-81W. THIS CONVECTION IS BEING ENHANCING
BY UPPER LEVEL DIFFLUENCE W OF AN UPPER LEVEL RIDGE OVER THE
CENTRAL CARIBBEAN. CURRENT SATELLITE IMAGES INDICATE THAT THE
LOW-LEVEL CIRCULATION IS NOT WELL-DEFINED. SIGNIFICANT
DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED TODAY ALTHOUGH
ENVIRONMENTAL CONDITIONS SHOULD BECOME MORE FAVORABLE FOR SOME
DEVELOPMENT ONCE THE SYSTEM MOVES INTO THE SOUTHERN GULF OF
MEXICO TONIGHT.  THERE IS A MEDIUM CHANCE...30 TO 50
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS. LOCALLY HEAVY RAINS WILL AFFECT PORTIONS OF
WESTERN AND CENTRAL CUBA...THE CAYMAN ISLANDS...AND THE YUCATAN
PENINSULA TODAY AND COULD SPREAD NORTHWARD TOWARDS SOUTH FLORIDA
OVER THE NEXT DAY OR SO.

...TROPICAL WAVES...

A TROPICAL WAVE IN THE CENTRAL ATLANTIC HAS BEEN RELOCATED JUST
E OF THE PREVIOUS ANALYSIS POSITION AND EXTENDS FROM 10N37W TO
1N38W MOVG W 10 KT. THE RELOCATION IS BASED ON SCATTEROMETER
DATA INDICATING A STRONGER CYCLONIC WIND SHIFT FARTHER E OF THE
PREVIOUS POSITION. THE NEW POSITION ALSO COINCIDES BETTER WITH
AN ELONGATED DEEP MOISTURE MAXIMUM BASED ON TOTAL PRECIPITABLE
WATER IMAGERY. THIS WAVE IS EMBEDDED IN THE ITCZ REDUCING THE
CONFIDENCE IN THE EXACT LOCATION AND TRACKING OF THIS WAVE.
ISOLATED MODERATE CONVECTION IS FROM 1N-9N BETWEEN 36W-41W.
MODEL GUIDANCE SUGGESTS THAT AN AREA OF STRONGER LOW LEVEL
CYCLONIC CIRCULATION IS EMBEDDED EVEN FARTHER E ALONG 31W. THAT
AREA WILL CONTINUE TO BE MONITORED FOR THE PRESENCE OF A
TROPICAL WAVE.

A TROPICAL WAVE IS ALONG 71W/72W S OF 20N MOVING W 10-15 KT. THE
PRESENCE OF DRY LOW/MID-LEVEL SAHARAN AIR OVER PORTIONS OF THE E
CARIBBEAN IS INHIBITING DEEP CONVECTION NEAR THIS WAVE.
HOWEVER...ISOLATED SHOWERS ARE OCCURRING FROM 18N-20N BETWEEN
69W-71W INCLUDING PORTIONS OF HISPANIOLA.

AN ACTIVE TROPICAL WAVE EXTENDS FROM
21N86W TO 5N88W MOVG W 10-15 KT AND IS AFFECTING PORTIONS OF THE
W CARIBBEAN. THIS WAVE AND ITS ASSOCIATED CONVECTION IS
DISCUSSED IN THE SPECIAL FEATURES SECTION ABOVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 8N24W 8N36W 7N47W AND
INTO NE S AMERICA NEAR 5N56W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 5N-9N BETWEEN 15W-18W. SCATTERED MODERATE
CONVECTION IS FROM 3N-10N BETWEEN 22W-27W...FROM6N-8N BETWEEN
28W-34W...AND FROM 6N-10N BETWEEN 52W-58W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL LOW CENTERED OVER
THE BAY OF CAMPECHE NEAR 20N94W AND AN UPPER LEVEL HIGH OVER N
TEXAS IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS OFF THE
COAST OF LOUISIANA AND TEXAS N OF 28N BETWEEN 91W-94W. UPPER
LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE OVER THE CENTRAL/E
UNITED STATES AND AN UPPER LEVEL TROUGH IN THE NW ATLC IS
SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS ACROSS N FLORIDA AND
THE ADJACENT COASTAL WATERS N OF 27N E OF 85W. ELSEWHERE ACROSS
THE CENTRAL AND W GULF...SUBSIDENCE AND DEEP LAYER DRY AIR ARE
RESULTING IN GENERALLY FAIR WEATHER. HOWEVER...MOISTURE SURGING
N FROM THE YUCATAN DUE TO THE APPROACH OF AN ACTIVE TROPICAL
WAVE IN THE FAR W CARIBBEAN IS SUPPORTING SHOWERS IN THE FAR SE
GULF OF MEXICO AND YUCATAN CHANNEL E OF 87W S OF 25N.

CARIBBEAN SEA...
SHOWERS AND THUNDERSTORMS OVER THE W CARIBBEAN ARE ASSOCIATED
WITH A TROPICAL WAVE...SEE ABOVE. AN UPPER LEVEL RIDGE IS OVER
THE CENTRAL CARIBBEAN BRINGING SUBSIDENCE AND ATMOSPHERIC
STABILITY SUPPRESSING THE TROPICAL WAVE IN THE CENTRAL
CARIBBEAN...SEE ABOVE... IS SUPPORTING GENERALLY FAIR WEATHER
ACROSS MUCH OF THE CENTRAL CARIBBEAN. ACROSS THE E CARIBBEAN
CONFLUENT NORTHWESTERLY FLOW ALOFT AND THE PRESENCE OF
LOW/MID-LEVEL DRY SAHARAN AIR ARE ALSO RESULTING IN GENERALLY
FAIR WEATHER.

ATLANTIC OCEAN...
UPPER LEVEL DIFFLUENCE ASSOCIATED WITH AN UPPER LEVEL TROUGH
OVER THE SW NORTH ATLC IS SUPPORTING SCATTERED SHOWERS/
THUNDERSTORMS N OF 27N BETWEEN 64W-78W. ALSO MOIST SOUTHWESTERLY
FLOW ALOFT IS SUPPORTING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS N OF 29N BETWEEN 59W-62W. MOIST UPPER LEVEL FLOW
AROUND THE RIDGE OVER THE CENTRAL CARIBBEAN IS SUPPORTING
ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE BAHAMAS S OF 27N W OF
72W. REMNANTS OF A CONVECTIVE BURST ASSOCIATED WITH THE TROPICAL
WAVE IN THE W CARIBBEAN CONTINUES TO AFFECT PORTIONS OF CENTRAL
CUBA AND THE ADJACENT N WATERS S OF 24N BETWEEN 78W-80W. FARTHER
TO THE E...A PAIR OF SURFACE HIGHS...A 1023 MB CENTER NEAR
32N47W...AND A 1021 MB CENTER NEAR 22N30W... ARE RESULTING IN
GENERALLY FAIR WEATHER. AN UPPER LEVEL TROUGH N OF 22N BETWEEN
20W-35W IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 26N34W
TO 31N22W. ACROSS THE TROPICAL ATLC...A BROAD UPPER LEVEL RIDGE
IS PRESENT WITH AXIS EXTENDING FROM AN UPPER LEVEL HIGH NEAR
16N35W IS SUPPORTING CONVECTION ALONG THE ITCZ.

$$
WALTON





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