000 AXNT20 KNHC 162350 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON JUL 16 2012 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS ADDED OFF THE COAST OF AFRICA ALONG 19N20W TO 13N17W MOVING W AT 10-15 KT. THE WAVE LIES ON THE E SIDE OF A SURGE OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. THERE IS ALSO A CLEARING IN THE SAHARAN DUST LAYER WITH AN AREA OF DENSE DUST DIRECTLY BEHIND THE WAVE. DUE TO THIS AREA OF DUST...NO DEEP CONVECTION IS CURRENTLY NEAR THE AXIS. TROPICAL WAVE IS ALONG 18N42W TO 10N46W MOVING W AT 15-20 KT. THE WAVE LIES ON THE W SIDE OF A SURFACE OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. IT ALSO COINCIDES WITH 700 MB MODEL DATA THAT INDICATES A MID-LEVEL TROUGH...OFTEN THE STRONGEST INDICATION OF THE WAVE...NEAR THE SURFACE LOCATION. SCATTERED MODERATE CONVECTION IS NEAR THE SRN TIP OF THE WAVE WITHIN THE ITCZ REGION FROM 8N-10N BETWEEN 43W-48W. TROPICAL WAVE MOVES ACROSS THE N CENTRAL CARIBBEAN AND SW BAHAMAS ALONG 23N75W TO 15N76W MOVING W AT 10-15 KT. THE WAVE IS EMBEDDED WITHIN AN AREA OF ENHANCED MOISTURE PRESENT ACROSS MUCH OF THE NRN CARIBBEAN. UPPER LEVEL RIDGE IS DRAWING SOME OF THE MOISTURE TOWARDS THE SE INTO THE SE CARIBBEAN. DAYTIME HEATING HAS HELPED FORM CLUSTER OF STRONG CONVECTION NEAR THE WAVE AXIS. ONE CLUSTER IS ACROSS HAITI FROM 18N-21N BETWEEN 72W-74W. OTHERS ARE OVER JAMAICA FROM 18N-19N BETWEEN 77W-80W...AND ACROSS ERN CUBA FROM 20N-21N BETWEEN 75W-77W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF GUINEA-BISSAU AT 13N17W CONTINUING S OF THE TROPICAL WAVE TO NEAR 9N30W TO S OF ANOTHER TROPICAL WAVE ALONG 11N40W 9N47W. THE ITCZ BEGINS AT 9N47W CONTINUING ALONG 8N52W TO 9N61W. SCATTERED MODERATE CONVECTION IS FROM 8N-10N BETWEEN 31W-34W...AND FROM 7N-9N BETWEEN 48W-53W. ...DISCUSSION... GULF OF MEXICO... A PAIR OF UPPER LEVEL LOWS IS IMPACTING THE GULF OF MEXICO AND IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM THE BIG BEND OF FLORIDA NEAR 30N83W TO THE CENTRAL GULF AT 25N89W TO THE SW GULF NEAR 19N93W. ONE OF THE UPPER LOWS IS CENTERED JUST OFFSHORE OF NE FLORIDA NEAR 30N81W...WHILE THE SECOND COVERS THE SE GULF CENTERED NEAR 23N86W. THE FIRST UPPER LOW IN COMBINATION WITH THE SURFACE TROUGH IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ALL UP THE FLORIDA PENINSULA ALONG WITH A FEW ISOLATED SHOWERS OVER THE GULF WATERS NEAR THE TROUGH AXIS. THE SECOND UPPER LOW IS SUPPORTING SHOWERS/THUNDERSTORMS OVER PORTIONS OF THE YUCATAN PENINSULA AND WRN CUBA. ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ALONG THE REMAINDER OF THE SURFACE TROUGH. DESPITE THE EXPANSIVE SURFACE TROUGH...SURFACE RIDGING COVERS MUCH OF THE NRN GULF EXTENDING FROM A 1018 MB HIGH OVER ALABAMA. THE HIGH IS SUPPORTED BY AN UPPER LEVEL RIDGE CENTERED OVER ARKANSAS THAT EXTENDS INTO THE NRN GULF. MODEL GUIDANCE INDICATES THAT THE SURFACE TROUGH WILL SPLIT LEAVING THE NRN PORTION MAINLY STATIONARY...WHILE THE SRN PORTION DRIFTS W. SURFACE RIDGING WILL REMAIN DOMINANT ACROSS THE REST OF THE BASIN. THE UPPER TROUGH/LOWS WILL ALSO REMAIN OVER THE ERN HALF OF THE BASIN...AND WILL LIKELY CAUSE MOIST CONDITIONS TO STAY OVER THIS AREA. CARIBBEAN SEA... THE UPPER LEVEL LOW OVER THE SE GULF OF MEXICO EXTENDS INTO THE NW CARIBBEAN SUPPORTING SHOWERS/THUNDERSTORMS NEAR THE COAST OF THE YUCATAN PENINSULA...NICARAGUA...AS WELL AS OVER WRN CUBA. SHOWERS/THUNDERSTORMS ARE ALSO OVER COSTA RICA AND PANAMA ASSOCIATED WITH THE MONSOON TROUGH THAT EXTENDS S OF COSTA RICA AND PANAMA TO NRN COLOMBIA. A TROPICAL WAVE APPROACHING JAMAICA AND ERN CUBA IS HELPING PRODUCE SHOWERS/THUNDERSTORMS OVER BOTH THESE AREAS ALONG WITH HAITI. SEE TROPICAL WAVE SECTION ABOVE FOR MORE DETAILS. AN UPPER LEVEL RIDGE COVERS THE CENTRAL CARIBBEAN EXTENDING FROM THE WINDWARD PASSAGE TO COSTA RICA. THE ERN SIDE OF THE RIDGE IS ACCOMPANIED BY DRY AIR WHICH IS HELPING MAINTAIN FAIR CONDITIONS BESIDES NEAR THE WAVE. THE ERN CARIBBEAN IS COVERED BY A DRY UPPER LEVEL TROUGH EXTENDING FROM THE CENTRAL ATLC TO THE VIRGIN ISLANDS TO NW VENEZUELA. VISIBLE SATELLITE IMAGERY ALONG WITH SURFACE OBSERVATIONS INDICATE THAT AN AREA OF SAHARAN DUST COVERS MUCH OF THE ERN CARIBBEAN FURTHER SUPPORTING FAIR CONDITIONS. TRADEWIND FLOW OF 20-25 KTS IS PRESENT OVER THE CENTRAL CARIBBEAN WITH LIGHTER WINDS TO EITHER SIDE. EXPECT THE WAVE TO CONTINUE MOVING WWD DRAWING MOISTURE OVER THE NW CARIBBEAN. ATLANTIC OCEAN... AN UPPER LEVEL LOW CENTERED OFF THE NE COAST OF FLORIDA NEAR 30N81W IS SUPPORTING SHOWERS/THUNDERSTORMS FROM 26N-31N BETWEEN 73W-76W...AS WELL AS FROM 23N-26N BETWEEN 76W-79W. THE REMAINDER OF THE W ATLC IS DOMINATED BY SURFACE RIDGING AROUND A 1020 MB HIGH NEAR 28N67W. THE HIGH IS SUPPORTED BY AN UPPER LEVEL RIDGE E OF THE UPPER LOW. A SECOND UPPER LEVEL TROUGH EXTENDS FROM NEAR 30N47W TO THE VIRGIN ISLANDS IN THE CARIBBEAN. THIS TROUGH SUPPORTS A SURFACE TROUGH ALONG 31N54W TO 27N55W. ISOLATED SHOWERS ARE WITHIN 120 NM E OF THE AXIS. THE ERN ATLC IS COVERED BY SURFACE RIDGING ANCHORED BY A 1030 MB HIGH NEAR 43N16W...WHICH IS PROVIDING FAIR WEATHER ACROSS THE REMAINDER OF THE BASIN. THE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE EXTENDING FROM NEAR 19N39W TO 32N12W. VISIBLE SATELLITE IMAGERY INDICATES AN INTENSE SURGE OF SAHARAN DUST HAS EMERGED OFF THE COAST OF AFRICA BEHIND A TROPICAL WAVE. DUST ALSO EXTENDS BETWEEN THE TWO ATLC WAVES. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON