000 AXNT20 KNHC 151724 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT WED JUL 15 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. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 25W S OF 15N MOVING W NEAR 15 KT. VISIBLE SATELLITE IMAGERY INDICATES MID-LEVEL CYCLONIC FLOW IN THE VICINITY OF THIS WAVE. THIS WAVE ALSO COINCIDES WITH A LOW AMPLITUDE DEEP LAYER MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE CONVECTION IS FROM 6N-13N BETWEEN 23W-27W. A TROPICAL WAVE IS ALONG 41W/42W S OF 16N MOVING W NEAR 15 KT. THIS WAVE COINCIDES WITH A LOW AMPLITUDE DEEP LAYER MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. NO DEEP CONVECTION IS CURRENTLY ASSOCIATED WITH THIS WAVE. A HIGHLY-AMPLIFIED TROPICAL WAVE IS OVER THE SW NORTH ATLC AND E CARIBBEAN EXTENDING FROM 24N67W TO 6N68W MOVING W NEAR 20 KT. VISIBLE SATELLITE IMAGERY SHOWS A WELL-DEFINED AND HIGHLY-AMPLIFIED INVERTED-V PATTERN IN THE LOW-LEVEL CLOUDS NEAR THE WAVE. THE WAVE ALSO COINCIDES WITH A HIGH AMPLITUDE MOISTURE MAXIMUM IN TOTAL PRECIPITABLE WATER. THE WAVE IS AT THE LEADING EDGE OF AN ABUNDANT DRY LOW/MID-LEVEL SAHARAN AIR LAYER. THE DRY AIR...ALONG WITH STABLE ATMOSPHERIC CONDITIONS BENEATH AN UPPER LEVEL HIGH OVER THE E CARIBBEAN...ARE LIMITING DEEP CONVECTION NEAR THE WAVE. HOWEVER...SCATTERED SHOWERS ARE WITHIN 100 NM OF THE WAVE AXIS FROM 15N-22N. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 10N14W 11N23W 9N34W 10N45W 9N63W SCATTERED MODERATE CONVECTION IS FROM 6N-12N E OF 23W. SIMILAR CONVECTION IS FROM 9N-11N BETWEEN 62W-68W. ...DISCUSSION... GULF OF MEXICO... A SURFACE RIDGE ANCHORED BY A 1019 MB SURFACE HIGH NEAR 27N85W DOMINATES THE GULF OF MEXICO BRINGING GENERALLY FAIR WEATHER ACROSS THE AREA. HOWEVER...A STATIONARY FRONT N OF THE DISCUSSION AREA IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE NRN GULF N OF 27N BETWEEN 88W-93W AND ACROSS THE FLORIDA PENINSULA N OF 24N E OF 85W. AN UPPER LEVEL HIGH OVER THE NW GULF NEAR 27N96W SUPPORTS THE SURFACE RIDGE. ANTI-CYCLONIC FLOW IS PRESENT AROUND THE SURFACE RIDGE WITH WINDS REACHING 15 KT ACROSS THE S GULF. EXPECT THE SURFACE RIDGE TO PERSIST OVER THE NEXT FEW DAYS. CARIBBEAN SEA... FRESH TO STRONG TRADE WINDS ARE OCCURRING BETWEEN THE SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH OVER NORTHERN SOUTH AMERICA...WITH THE STRONGEST FLOW NEAR THE COAST OF COLOMBIA. IN FACT...GALE CONDITIONS ARE FORECAST TO BEGIN LATER TONIGHT. UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH OVER THE NW CARIBBEAN WITH AXIS ALONG 18N84W TO 22N78W AND INTO THE SW NORTH ATLC AND AN UPPER LEVEL RIDGE CENTERED AROUND AN UPPER LEVEL HIGH OVER HISPANIOLA NEAR 19N72W IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE COAST OF CENTRAL AMERICA S OF 19N W OF 82W. SURFACE CONVERGENCE NEAR A 1010 MB SURFACE LOW OVER PANAMA NEAR 9N79W IS SUPPORTING NUMEROUS SHOWERS/THUNDERSTORMS S OF 12N W OF 78W INCLUDING PORTIONS OF COSTA RICA AND PANAMA. THE REMAINDER OF THE CARIBBEAN IS EXPERIENCING GENERALLY FAIR WEATHER DUE TO DRY AIR AND SUBSIDENCE ALOFT. A TROPICAL WAVE IS IN E/CENTRAL CARIBBEAN...HOWEVER THE DRY AIR ALOFT IS SUPPRESSING ANY DEEP CONVECTION. ATLANTIC OCEAN... A STATIONARY FRONT N OF THE DISCUSSION AREA IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE SW NORTH ATLC N OF 28N W OF 71W. UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL HIGH OVER ALABAMA NEAR 32N86W AND AN UPPER LEVEL TROUGH ACROSS THE NW ATLC SUPPORTS THE FRONT AS WELL AS A PAIR OF SURFACE TROUGHS IN THE SW NORTH ATLC. THE FIRST SURFACE TROUGH EXTENDS FROM 25N74W TO 30N68W. SURFACE CONVERGENCE NEAR THE TROUGH IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS WITHIN 100 NM OF THE TROUGH AXIS..AS WELL AS SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE CENTRAL BAHAMAS AND N OF CUBA FROM 22N-27N BETWEEN 77W-80W. THE SECOND SURFACE TROUGH FORMED AS A FRACTURE OF THE HIGH-AMPLITUDE TROPICAL WAVE IN THE E/CENTRAL CARIBBEAN...AND EXTENDS FROM 26N67W TO 30N63W. SCATTERED SHOWERS/THUNDERSTORMS ARE NEAR THE N PORTION OF THE TROUGH N OF 29N BETWEEN 60W-65W. A BROAD SURFACE RIDGE DOMINATES THE REMAINDER OF THE ATLC ANCHORED BY A 1028 MB SURFACE HIGH N OF THE DISCUSSION AREA NEAR 35N44W...EXCEPT FOR A COLD FRONT THAT ENTERS THE AREA NEAR 32N32W TO 30N37W TO 31N40W. NO SHOWERS ARE CURRENTLY ASSOCIATED WITH THE FRONT. ACROSS THE TROPICAL ATLC...A BROAD UPPER LEVEL RIDGE IS S OF 24N ENHANCING CONVECTION ALONG THE E PORTION OF THE ITCZ. $$ WALTON