000 AXNT20 KNHC 012349 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT AUG 01 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... A TROPICAL WAVE OVER THE TROPICAL ATLC EXTENDS FROM 23N35W TO 20N34W TO 16N31W TO 6N30W MOVING W NEAR 15 KT. SATELLITE-DERIVED WINDS INDICATE CYCLONIC CURVATURE IN THE FLOW WITHIN THE 950-800 MB LAYER NEAR THIS WAVE...AND RECENT SATELLITE IMAGERY INDICATES THAT THIS WAVE COINCIDES WITH A LOW/MID-LEVEL CYCLONIC CIRCULATION CENTER NEAR 13N30W. THE N PORTION OF THIS WAVE IS NEAR A CLOSED UPPER LEVEL LOW NEAR 17N29W...WITH THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS INDICATING AN AREA OF DEEP LAYER MOISTURE ACROSS THE NORTHERN ONE-THIRD OF THE WAVE. NEAR THIS N PORTION OF THE WAVE...SCATTERED SHOWERS ARE OCCURRING FROM 21N-28N BETWEEN 31W-38W. ACROSS THE CENTRAL ONE-THIRD OF THIS WAVE...DRY LOW/MID-LEVEL SAHARAN AIR HAS WRAPPED CYCLONICALLY AROUND THE WAVE INHIBITING THE DEVELOPMENT OF DEEP CONVECTION. ACROSS THE SOUTHERN ONE-THIRD OF THE WAVE...DEEP LAYER MOISTURE IS ALSO MAXIMIZED...WITH SCATTERED MODERATE CONVECTION FROM 8N-11N BETWEEN 27W-32W. A TROPICAL WAVE OVER THE TROPICAL ATLC EXTENDS FROM 24N55W TO 22N56W TO 7N55W MOVING W NEAR 20 KT. RECENT VISIBLE SATELLITE IMAGERY DEPICTS INVERTED-V STRUCTURES ASSOCIATED WITH LOW-LEVEL CLOUD BANDS NEAR THIS WAVE. ADDITIONALLY...THIS WAVE IS AT THE LEADING EDGE OF A BROAD...ALTHOUGH WEAK...MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. THE QUIKSCAT PASS AROUND 01/1300 UTC INDICATED CYCLONIC CURVATURE IN THE LOW LEVEL FLOW NEAR THIS WAVE...WITH NE TO E WINDS OF 10 TO 15 KT WITHIN 60 NM E OF THE WAVE AXIS...AND NE WINDS OF AROUND 15 KT WITHIN 60 NM W OF THE WAVE AXIS. ALSO... SATELLITE-DERIVED WINDS INDICATE CYCLONIC CURVATURE IN THE FLOW WITHIN THE 950-800 MB LAYER IN THE VICINITY OF THIS WAVE. SCATTERED MODERATE CONVECTION IS FROM 9N-12N BETWEEN 52W-55W...WHICH IS BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR THE ITCZ. A TROPICAL WAVE OVER THE W CARIBBEAN EXTENDS FROM 22N81W TO THE COAST OF HONDURAS NEAR 15N84W TO THE E PACIFIC REGION NEAR 1N86W MOVING W NEAR 20 KT. THIS WAVE IS EMBEDDED WITHIN A WELL-DEFINED MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. ALSO...SATELLITE-DERIVED WINDS INDICATE CYCLONIC CURVATURE IN THE FLOW WITHIN THE 800-600 MB LAYER IN THE VICINITY OF THIS WAVE. SCATTERED MODERATE CONVECTION IS FROM 12N-18N BETWEEN 82W-87W INCLUDING PORTIONS OF E HONDURAS AND E NICARAGUA...WHICH IS BEING ENHANCED BY ATMOSPHERIC INSTABILITY CAUSED BY DIURNAL HEATING OVER LAND. ADDITIONALLY...SCATTERED MODERATE CONVECTION IS FROM 19N-23N BETWEEN 78W-85W...WHICH IS BEING ENHANCED BY ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW OVER THE NW CARIBBEAN NEAR 21N84W. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 11N14W 9N26W 10N40W 10N52W 9N61W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 8N-13N E OF 19W. SCATTERED MODERATE CONVECTION IS FROM 7N-11N BETWEEN 36W-41W. SCATTERED MODERATE CONVECTION IS ALSO FROM 8N-10N BETWEEN 47W-50W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL RIDGE EXTENDS EASTWARD FROM AN UPPER LEVEL HIGH OVER NE MEXICO ACROSS THE N GULF OF MEXICO. UPPER LEVEL DIFFLUENCE BETWEEN THIS UPPER LEVEL RIDGE AND A BROAD UPPER LEVEL TROUGH OVER THE E UNITED STATES IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS OVER THE N GULF N OF 27N E OF 90W. ADDITIONALLY...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE OCCURRING S OF 26N E OF 85W...WHICH ARE RESULTING FROM ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL TROUGH. THIS UPPER LEVEL TROUGH EXTENDS NORTHWARD INTO THE FAR SE GULF AND SW NORTH ATLC FROM AN UPPER LEVEL LOW CENTERED OVER THE NW CARIBBEAN SEA NEAR 21N84W. ACROSS MUCH OF THE CENTRAL AND SW GULF...DEEP LAYER DRY AIR AND SUBSIDENCE IN NORTHEASTERLY FLOW ALOFT S OF THE AFOREMENTIONED UPPER LEVEL RIDGE ARE SUPPORTING GENERALLY FAIR WEATHER. THIS SUBSIDENCE IS ALSO SUPPORTING A SURFACE RIDGE ACROSS THE N GULF. THE INCREASED PRESSURE GRADIENT S AND W OF THIS SURFACE RIDGE IS SUPPORTING SE WINDS OF 10 TO 15 KT ACROSS THE W GULF. CARIBBEAN SEA... SCATTERED MODERATE CONVECTION IS OCCURRING OVER THE W CARIBBEAN IN ASSOCIATION WITH THE TROPICAL WAVE EXTENDING FROM 22N81W TO 15N84W TO THE E PACIFIC REGION NEAR 1N86W...AS WELL AS AN UPPER LEVEL LOW OVER THE NW CARIBBEAN CENTERED NEAR 21N84W. THE TROPICAL WAVE AND UPPER LEVEL LOW ARE DISCUSSED IN THE TROPICAL WAVES SECTION ABOVE. ACROSS THE CENTRAL AND E CARIBBEAN...DEEP LAYER DRY AIR...INCLUDING DRY LOW/MID-LEVEL SAHARAN AIR...IS SUPPORTING GENERALLY FAIR WEATHER. HOWEVER...ATMOSPHERIC INSTABILITY NEAR A WEAK UPPER LEVEL TROUGH OVER THE N CENTRAL CARIBBEAN IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS FROM 17N-19N BETWEEN 73W-78W INCLUDING PORTIONS OF JAMAICA. FRESH TO STRONG TRADE WINDS ARE PRESENT ACROSS MUCH OF THE CENTRAL AND S CARIBBEAN TO THE S OF A SURFACE RIDGE OVER THE CENTRAL ATLC. THE STRONGEST WINDS ARE FOUND NEAR THE COAST OF COLOMBIA...WHERE E WINDS OF 25 AND 30 KT ARE OCCURRING. ATLANTIC OCEAN... SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE OCCURRING OVER THE SW NORTH ATLC S OF 25N W OF 79W DUE TO ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL TROUGH. THIS UPPER LEVEL TROUGH EXTENDS NORTHWARD INTO THE SW NORTH ATLC AND FAR SE GULF OF MEXICO FROM AN UPPER LEVEL LOW CENTERED OVER THE NW CARIBBEAN SEA NEAR 21N84W. FARTHER TO THE E...SUBSIDENCE IS OCCURRING NEAR A BROAD SURFACE RIDGE AND IS RESULTING IN GENERALLY FAIR WEATHER ACROSS MUCH OF THE CENTRAL AND E ATLC. THIS BROAD SURFACE RIDGE IS ASSOCIATED WITH A 1027 MB SURFACE HIGH NEAR 36N53W AND A 1027 MB SURFACE HIGH NEAR 35N44W. HOWEVER...ATMOSPHERIC INSTABILITY NEAR AN UPPER LEVEL LOW CENTERED NEAR 32N61W IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS N OF 28N BETWEEN 52W-66W. ANOTHER UPPER LEVEL LOW IS CENTERED NEAR 29N42W WITH ATMOSPHERIC INSTABILITY SUPPORTING SCATTERED SHOWERS FROM 27N-31N BETWEEN 41W-46W. ALSO...AN UPPER LEVEL TROUGH AXIS OVER THE E ATLC EXTENDS FROM AN UPPER LEVEL LOW OVER W AFRICA NEAR 17N14W TO 21N18W TO 23N20W. THIS UPPER LEVEL TROUGH IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 20N28W TO 21N20W TO W AFRICA NEAR 24N12W. THE SURFACE TROUGH IS ASSOCIATED WITH W TO NW WINDS OF 10 TO 15 KT WITHIN 60 NM N OF THE SURFACE TROUGH AND SW TO W WINDS OF 10 TO 15 KT WITHIN 60 NM S OF THE SURFACE TROUGH. ABUNDANT DRY LOW/MID-LEVEL SAHARAN AIR IS INHIBITING PRECIPITATION NEAR THIS SURFACE TROUGH. $$ COHEN