000 AXNT20 KNHC 201041 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT SAT JUL 20 2013 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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1022 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS OVER THE CENTRAL TROPICAL ATLC EXTENDING FROM 19N42W TO 08N47W AND MOVING W-SW NEAR 10 KT. THE WAVE AXIS LIES WITHIN A MODERATE MOIST ENVIRONMENT AS DEPICTED IN TOTAL PRECIPITABLE WATER IMAGERY. THE METEOSAT-9 SAL TRACKING IMAGERY SHOW THE WAVE IS ENGULFED BY SAL DRY AIR WITH SOME OF IT SPREADING OVER THE ITS ENVIRONMENT WHICH IS SUPPRESSING DEEP CONVECTION. TROPICAL WAVE EXTENDS FROM 19N78W TO 09N78W MOVING W NEAR 10 KT. THE WAVE AXIS LIES WITHIN A MODERATE MOIST ENVIRONMENT DEPICTED IN TOTAL PRECIPITABLE WATER IMAGERY. ISOLATED SHOWERS ARE WITHIN 150 NM W OF THE AXIS FROM 16N-19N AND WITHIN 60 NM EITHER SIDE OF THE AXIS S OF 10N. TROPICAL WAVE IS MOVING ALONG BELIZE...GUATEMALA AND EL SALVADOR EXTENDING FROM 18N88W TO 10N89W AND MOVING W NEAR 15 KT KT. THE WAVE IS EMBEDDED WITHIN A MODERATE MOIST ENVIRONMENT IN BELIZE AND THE EAST PACIFIC WHILE THE REMAINING WAVE OVER LAND IS WITHIN DRY AIR. SCATTERED MODERATED CONVECTION WITH ISOLATED THUNDERSTORMS ARE OVER SOUTHERN BELIZE AND EASTERN GUATEMALA. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE WEST COAST OF AFRICA NEAR 12N16W TO 09N21W 06N26W. THE ITCZ BEGINS NEAR 06N26W AND CONTINUES ALONG 04N33W TO 08N41W THEN IT RESUMES WEST OF A TROPICAL WAVE ALONG 08N49W TO 06N57W. SCATTERED MODERATE CONVECTION IS WITHIN 100 NM EITHER SIDE OF THE AXES E OF 31W AS WELL AS FROM 07N-10N BETWEEN 53W-60W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL LOW CENTERED OVER LOUISIANA CONTINUES TO EXTEND A TROUGH INTO THE GULF W OF 87W. THIS IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM THE FLORIDA PANHANDLE TO 30N87W 28N90W TO 25N94W. SMALL CLUSTERS OF MODERATE CONVECTION WITH ISOLATED THUNDERSTORMS ARE WITHIN 200 NM SE OF THE TROUGH AXIS. DIVERGENT FLOW ALOFT RESULTING FROM AN UPPER LEVEL HIGH WEST OF MEXICO AND THE TROUGH OVER THE WESTERN GULF IS ENHANCING SCATTERED MODERATE CONVECTION AND ISOLATED THUNDERSTORMS S OF 20N W OF 92W. ANOTHER AREA OF DIVERGENT FLOW ALOFT DUE TO A RIDGE AXIS E OF 87W IS ENHANCING SCATTERED SHOWERS IN THE YUCATAN CHANNEL. RETURN FLOW WITH WINDS RANGING FROM 5-15 KT SPREADS ACROSS THE BASIN. RAINSHOWERS ARE EXPECTED TO CONTINUE OVER THE GULF UNTIL SUNDAY NIGHT WHILE THE SURFACE TROUGH ACROSS THE GULF CONTINUES TO MOVE NW. RETURN FLOW IS ALSO EXPECTED TO PREVAIL DURING THAT TIME. CARIBBEAN SEA... UPPER LEVEL RIDGING COVERS MUCH OF THE WESTERN CARIBBEAN WHICH IS PROVIDING NORTHERLY FLOW ALOFT THAT IS DRAWING MOISTURE SOUTH FROM THE GULF OF MEXICO. THE REMNANTS OF A TROPICAL WAVE THAT IS MOVING ACROSS CENTRAL AMERICA AS WELL AS DIFFLUENT FLOW ALOFT FROM THE UPPER LEVEL LOW OVER THE WESTERN GULF AND THE HIGH TO THE EAST ARE SUPPORTING SCATTERED MODERATE CONVECTION AND ISOLATED THUNDERSTORMS N OF 16N W OF 83W. A TROPICAL WAVE IS MOVING ACROSS THE WESTERN CARIBBEAN JUST WEST OF JAMAICA EXTENDING FROM 19N78W TO 09N78W. ISOLATED SHOWERS ARE WITHIN 140 NM W OF THE AXIS FROM 16N-19N AS WELL AS EITHER SIDE OF THE AXIS S OF 10N. ISOLATED SHOWERS AND THUNDERSTORMS ARE WITHIN 90 NM OF THE COASTLINES OF NICARAGUA...COSTA RICA AND PANAMA. THE REMAINDER OF THE BASIN IS UNDER MOSTLY FAIR CONDITIONS DUE TO DRY AIR AT THE LOWER AND MIDDLE LEVELS ACTING TO SUPPRESS DEEP CONVECTION. TRADEWINDS FROM 15 TO 25 KT SPREAD ACROSS THE BASIN WITH THE MAXIMUM VALUES BEING ACROSS THE CENTRAL CARIBBEAN DUE TO A TIGHTER PRESSURE GRADIENT. THE WAVE OVER CENTRAL AMERICA IS EXPECTED TO BE COMPLETELY OVER THE E PACIFIC EARLY ON SATURDAY WHILE THE SECOND TRAILING WAVE IS EXPECTED TO DISSIPATE DUE TO INTERACTION WITH VERY DRY AIR AT THE LOWER LEVELS. HISPANIOLA... DRY AIR IS ACROSS LA HISPANIOLA LIMITING ANY CONVECTIVE ACTIVITY EVEN THAT A DIVERGENT PATTERN IS ALOFT. A DRY AIR MASS WILL CONTINUE TO BRING FAIR WEATHER TO THE ISLAND UNTIL EARLY SUNDAY AFTERNOON WHEN CONDITIONS CAN START TO DETERIORATE FOR THE DOMINICAN REPUBLIC DUE TO A SURGE OF LOW LEVEL MOISTURE. THIS MOISTURE WILL DRIFT WESTWARD TOWARD HAITI LATE ON SUNDAY AND SHOWERS MAY BE EXPECTED. ATLANTIC OCEAN... A SURFACE TROUGH IS MOVING ACROSS THE BAHAMAS EXTENDING FROM 26N73W TO 23N79W. CONVECTION ASSOCIATED WITH IT HAS AUGMENTED TO A CLUSTER OF MODERATE CONVECTION WITH EMBEDDED THUNDERSTORMS FROM 22N-25N BETWEEN 76W-80W. N OF THAT CONVECTION...SCATTERED SHOWERS ARE W OF 75W. SURFACE RIDGING IS ACROSS THE REMAINDER BASIN ANCHORED BY A PAIR OF 1022 MB HIGHS...ONE NEAR 28N64W AND THE OTHER NEAR 29N32W. BESIDES THE REGIONS FORMERLY MENTIONED...FAIR WEATHER IS ACROSS THE ATLC SUPPORTED BY DRY AIR AT THE LOWER AND MIDDLE LEVELS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ NR