000 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