000 AXNT20 KNHC 150513 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0445 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 23W S OF 15N MOVING W NEAR 15 KT. SATELLITE IMAGERY DEPICTS MID-LEVEL CYCLONIC CIRCULATION NEAR THIS WAVE. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 7N-12N BETWEEN 22W-29W. A TROPICAL WAVE IS ALONG 40W S OF 18N MOVING W 15-20 KT. THIS WAVE COINCIDES WITH A LOW AMPLITUDE MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. SCATTERED MODERATE CONVECTION IS FROM 12N-15N BETWEEN 36W-40W. A HIGHLY-AMPLIFIED TROPICAL WAVE IS OVER THE N TROPICAL ATLC AND E CARIBBEAN...AND EXTENDS FROM 24N63W TO 13N63W TO 7N60W MOVING W NEAR 20 KT. UPPER AIR DATA FROM BARBADOS AND GUADELOUPE AT 15/0000 UTC INDICATE THAT THE WAVE IS FOLLOWED BY A STRONG EASTERLY 700-650 MB JET...WITH CORE WINDS OF 45 KT. RECENT SATELLITE IMAGERY SHOW A WELL-DEFINED AND HIGHLY-AMPLIFIED INVERTED-V PATTERN EVIDENT IN THE COVERAGE OF LOW-LEVEL CLOUDS NEAR THE WAVE...COINCIDING WITH A MAXIMUM IN TOTAL PRECIPITABLE WATER. THE WAVE IS LEADING AN AREA OF ABUNDANT DRY LOW/MID-LEVEL SAHARAN AIR. THIS IS CONTRIBUTING TO A DENSITY DIFFERENCE SUFFICIENT TO PROVIDE LOW LEVEL ATMOSPHERIC LIFT SUPPORTING SCATTERED SCATTERED SHOWERS WITHIN 90 NM EITHER E OF THE WAVE AXIS N OF 14N...WITH SCATTERED SHOWERS AND THUNDERSTORMS WITHIN 90 NM E OF THE WAVE AXIS S OF 14N WHERE A WEAK UPPER LEVEL SHORTWAVE TROUGH IS PROVIDING ADDITIONAL SUPPORT FOR CONVECTION. THIS DRY AIR IS LIMITING THE AREAL COVERAGE OF DEEP CONVECTION NEAR THE WAVE. THE AFOREMENTIONED DRY AIR IS LIKELY CONTRIBUTING TO STRONG DOWNDRAFTS AND GUSTY OUTFLOW WINDS WITH THE SHOWER AND THUNDERSTORM ACTIVITY. THE TROPICAL WAVE PREVIOUSLY ALONG 97W/98W S OF MEXICO AT 14/1800 UTC IS NOW IN THE E PACIFIC REGION AND IS FURTHER DISCUSSED IN THE TROPICAL WEATHER DISCUSSION FOR THE E PACIFIC FOUND UNDER AWIPS/WMO HEADERS MIATWDEP/AXPZ20 KNHC. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 10N14W 9N29W 9N41W 9N53W 10N62W. NUMEROUS MODERATE TO STRONG CONVECTION IS FROM 6N-15N E OF 21W. SCATTERED MODERATE CONVECTION IS FROM 8N-10N BETWEEN 52W-55W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL RIDGE EXTENDS SOUTHEASTWARD INTO THE GULF OF MEXICO FROM THE SOUTHERN UNITED STATES AND IS ASSOCIATED WITH A SURFACE RIDGE ACROSS THE N GULF AND A 1018 MB SURFACE HIGH NEAR 28N89W. GENERALLY FAIR WEATHER IS PRESENT ACROSS THE GULF. ONE EXCEPTION IS OVER THE N CENTRAL GULF...WHERE SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE PRESENT N OF 27N BETWEEN 86W-91W. THIS ACTIVITY IS BEING SUPPORTED BY ATMOSPHERIC LIFT ASSOCIATED WITH A WEAK UPPER LEVEL SHORTWAVE TROUGH TRANSLATING SOUTHEASTWARD ON THE OUTER PERIPHERY OF THE AFOREMENTIONED UPPER RIDGE. WINDS ARE LIGHT AND VARIABLE IN THE VICINITY OF THE SURFACE RIDGE ACROSS THE N GULF...WITH ANTICYCLONIC FLOW AROUND THE RIDGE SUPPORTING A BROAD SWATH OF E WINDS OF 10-15 KT ACROSS THE S HALF OF THE GULF. NE WINDS UP TO 20 KT ARE OCCURRING NEAR THE COAST OF THE YUCATAN PENINSULA...AND THESE WINDS WILL OCCUR DURING THE LATE AFTERNOON AND EVENING HOURS DURING THE NEXT SEVERAL DAYS NEAR THE COAST OF THE YUCATAN PENINSULA. LITTLE CHANGE IS EXPECTED OVER THE NEXT DAY OR TWO AS BOTH THE UPPER AND SFC RIDGE REMAIN IN PLACE. 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. THE QUIKSCAT PASS AROUND 14/2315 UTC INDICATED A LARGE AREA OF NE TO E WINDS OF 20 TO 30 KT ACROSS THE CENTRAL CARIBBEAN. THESE WINDS WILL REMAIN STRONG OVER THE NEXT SEVERAL DAYS AS THE SUBTROPICAL RIDGE REMAINS IN PLACE AND A TROPICAL WAVE MOVES ACROSS THE AREA. IN FACT...GALE CONDITIONS ARE FORECAST TO BEGIN LATER TODAY THROUGH THE END OF THE WEEK...AS THE LOW LEVEL FLOW STRENGTHENS ACROSS THE CARIBBEAN AND INTERACTS THE LOCAL TOPOGRAPHICAL VARIATIONS NEAR THE COAST OF COLOMBIA. ALOFT...INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW OVER THE N CENTRAL CARIBBEAN CENTERED NEAR 18N82W IS RESULTING IN SCATTERED SHOWERS AND THUNDERSTORMS FROM 15N-20N BETWEEN 80W-85W. THE TROPICAL WAVE MOVING ACROSS THE E CARIBBEAN IS ACCOMPANIED BY...AND FOLLOWED BY...STRONGER WINDS AND A STRONG SURGE OF SAHARAN AIR. ATLANTIC OCEAN... DEEP LAYER MOISTURE IS COMBINING WITH UPPER LEVEL DIFFLUENCE IN NORTHWESTERLY FLOW ALOFT TO RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE SW NORTH ATLC N OF 29N W OF 74W. ALSO...SCATTERED SHOWERS AND ISOLATED TSTMS ARE N OF 24N BETWEEN 65W-72W. THIS ACTIVITY IS BEING SUPPORTED BY LOW LEVEL CONVERGENCE NEAR A SURFACE TROUGH EXTENDING FROM 28N68W TO 26N71W TO 22N73W. THIS ACTIVITY IS ALSO SUPPORTED BY ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER TROUGH OVER THE SW NORTH ATLC. SUBSIDENCE AND GENERALLY FAIR WEATHER ARE PRESENT ACROSS MUCH OF THE CENTRAL AND E ATLC AROUND A BROAD SURFACE RIDGE WITH A 1031 MB HIGH NEAR 35N46W. ACROSS THE TROPICAL N ATLC... NORTHEASTERLY UPPER LEVEL FLOW IS IN PLACE...WITH STRONG UPPER LEVEL DIFFLUENCE SUPPORTING THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVE ALONG 40W S OF 18N. $$ COHEN