[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201056
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT JUN 20 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
1015 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 10N44W TO 0N46W MOVING W AROUND
10-12 KT. THIS WAVE HAS BEEN FAIRLY DIFFICULT TO TRACK OVER THE
PAST 24 HOURS OR SO AS IT IS A VERY LOW AMPLITUDE WAVE. THE
FIRST VISIBLE SATELLITE IMAGES FROM METEOSAT9 SHOW CYCLONIC
CIRCULATION IN THE MOTION OF LOW LEVEL CLOUDS NEAR THE WAVE
AXIS. A SMALL CLUSTER OF MODERATE CONVECTION WAS NOTED ALONG
THE WAVE AXIS NEAR 8N45W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 8N13W 4N25W 7N41W AND INTO NE
BRAZIL NEAR 5N53W. SCATTERED MODERATE/STRONG CONVECTION...
REMNANTS OF A SQUALL LINE WHICH EMERGED OFF AFRICA EARLIER
TONIGHT NOW EXTENDS FROM 2N-8N BETWEEN 12W-16W. SCATTERED
MODERATE CONVECTION IS INDICATED ELSEWHERE WITHIN 120 NM N OF
THE AXIS BETWEEN 37W AND THE COAST OF SOUTH AMERICA.

...DISCUSSION...

GULF OF MEXICO...
ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW
CENTERED OVER THE YUCATAN PENINSULA IS SUPPORTING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS OVER THE GULF S OF 23N E OF
88W...EXTENDING ACROSS THE FLORIDA KEYS. ACROSS THE N AND
CENTRAL GULF...DEEP LAYER DRY AIR IS SUPPORTING GENERALLY FAIR
WEATHER...WHERE EASTERLY FLOW ALOFT IS OCCURRING BETWEEN THE
AFOREMENTIONED UPPER LEVEL LOW OVER THE YUCATAN AND A LARGE
UPPER LEVEL HIGH OVER MISSISSIPPI. THIS UPPER LEVEL HIGH IS
ASSOCIATED WITH A 1014 MB SURFACE HIGH OVER THE CENTRAL GULF
NEAR 28N88W. ANTICYCLONIC FLOW AROUND THE SURFACE HIGH IS
AFFECTING MUCH OF THE GULF...WITH SE WINDS OF 15 TO 20 KT
OCCURRING ACROSS PORTIONS OF THE W GULF IN RESPONSE TO A BROAD
SURFACE TROUGH OVER MEXICO AND THE SOUTHERN PLAINS OF THE UNITED
STATES. THIS SURFACE HIGH IS FORECAST TO MEANDER OVER THE
CENTRAL GULF WATERS THROUGH SATURDAY NIGHT...BEFORE A WEAK COLD
FRONT MOVES SOUTHEASTWARD INTO THE NE GULF LATE SUNDAY.

CARIBBEAN SEA...
AN UPPER LEVEL LOW IS OVER THE YUCATAN PENINSULA...MOVING WEST
10 KT AND UNDERCUTTING THE LARGE UPPER HIGH OVER THE SOUTHERN
U.S. ATMOSPHERIC INSTABILITY COMBINED WITH INCREASINGLY
DIFFLUENT FLOW ALOFT SE OF THE UPPER LOW IS SUPPORTING SCATTERED
SHOWERS AND THUNDERSTORMS OVER THE W CARIBBEAN N OF 14N W OF 79W
INCLUDING PORTIONS OF NICARAGUA...HONDURAS AND BELIZE. ACROSS
THE E CARIBBEAN...UPPER LEVEL MOISTURE AND HIGH LEVEL CLOUDS ARE
STREAMING NORTHEASTWARD TO THE E OF AN UPPER LEVEL TROUGH AXIS
THAT EXTENDS FROM 18N69W TO 12N70W. THIS MOISTURE IS INTERACTING
WITH ATMOSPHERIC INSTABILITY TO RESULT IN SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS OVER THE NE CARIBBEAN N OF 16N E OF 72W
INCLUDING PORTIONS OF HISPANIOLA. MODERATE TO FRESH EASTERLY
TRADES ARE FORECAST TO OCCUR S OF 16N THROUGH SUNDAY TO THE S OF
A SURFACE RIDGE OVER THE CENTRAL ATLC.

ATLANTIC OCEAN...
SUBSIDENCE IN NORTHWESTERLY FLOW ALOFT IS SUPPORTING GENERALLY
FAIR WEATHER ACROSS THE SW NORTH ATLC. HOWEVER...UPPER LEVEL
DIFFLUENCE AND UPPER LEVEL MOISTURE ARE SUPPORTING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS FROM 23N-27N W OF 72W
INCLUDING PORTIONS OF THE NW BAHAMAS. TO THE E...AN UPPER LEVEL
TROUGH OVER THE CENTRAL ATLC IS ASSOCIATED WITH A STATIONARY
FRONT EXTENDING FROM 31N46W SOUTHWEST TO 29N52W THEN CURVING
NORTHWEST TO 32N56W. LOW LEVEL CONVERGENCE NEAR THE FRONT
IS INTERACTING WITH MOISTURE IN DIFFLUENT AND MOIST WESTERLY
FLOW ALOFT TO RESULT IN SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS N OF 29N BETWEEN 58W-66W. ACROSS MUCH OF THE
CENTRAL AND E ATLC... GENERALLY FAIR WEATHER IS PRESENT WHERE
SUBSIDENCE IS OCCURRING NEAR A BROAD SURFACE RIDGE. HOWEVER...A
DEEP LAYER LOW OVER THE E ATLC IS ASSOCIATED WITH A SURFACE
TROUGH WHICH BEGINS JUST TO THE NORTH OF THE DISCUSSION AREA
NEAR 32N21W. LOW LEVEL CONVERGENCE NEAR THIS SURFACE TROUGH IS
SUPPORTING SCATTERED SHOWERS N OF 31N BETWEEN 20W-24W. ACROSS
THE TROPICAL ATLC...A BROAD UPPER LEVEL RIDGE IS S OF 15N E OF
53W WITH AN UPPER LEVEL HIGH NEAR 13N23W. UPPER LEVEL DIVERGENCE
ASSOCIATED WITH THE UPPER LEVEL HIGH AND UPPER LEVEL RIDGE IS
SUPPORTING THE CONVECTION ASSOCIATED WITH THE ITCZ AND WITH THE
TROPICAL WAVE THAT EXTENDS FROM 10N45W TO 1N46W.

$$
COBB



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