000 AXNT20 KNHC 172332 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT WED JUL 17 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2245 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 19N25W TO 8N29W MOVING W AT 15-20 KT. THE WAVE COINCIDES WITH A LARGE SURGE OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY ALONG WITH A 700 MB TROUGH AXIS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 7N-10N BETWEEN 25W-33W. TROPICAL WAVE EXTENDS FROM 21N60W TO 13N62W MOVING W AT 20-25 KT. THE WAVE LIES WITHIN AN AREA OF ENHANCED MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY...AND HAS ESCAPED THE DRY SAHARAN AIR LAYER PRESENT OVER MUCH OF THE TROPICAL ATLC. THIS HAS LED TO INCREASED CONVECTION NEAR THE WAVE OVER THE PAST 24 HOURS. CURRENTLY...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 14N-17N BETWEEN 59W-62W. ISOLATED MODERATE CONVECTION IS FROM 18N-21N BETWEEN 57W-62W. TROPICAL WAVE EXTENDS FROM 18N74W TO 11N75W MOVING W AT 20 KT. THE MOISTURE SIGNAL WITH THE WAVE HAS WEAKENED CONSIDERABLY WITH ONLY A WEAK INCREASE IN MOISTURE TO THE WEST OF THE AXIS. THE WAVE ALSO ALIGNS WITH A VERY WEAK SIGNAL IN THE 700 MB FIELDS WHICH IS MOST PROMINENT NEAR THE COAST OF COLOMBIA. ONLY A SMALL CLUSTER OF STRONG CONVECTION IS OVER HAITI FROM 19N-20N BETWEEN 72W-73W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE COAST OF MAURITANIA FROM 17N16W TO 19N22W. THE ITCZ BEGINS ON THE WEST SIDE OF A TROPICAL WAVE ALONG 8N31W 6N43W 4N52W. SCATTERED MODERATE/STRONG CONVECTION IS FROM 4N-8N BETWEEN 39W-50W. ...DISCUSSION... GULF OF MEXICO... A PAIR OF UPPER LEVEL LOWS DOMINATE THE UPPER LEVEL PATTERN OVER THE GULF OF MEXICO. THE FIRST IS CENTERED OVER THE NE GULF NEAR 29N84W PROVIDING DIFFLUENT FLOW ACROSS FLORIDA. IT ALSO SUPPORTS A WEAK SURFACE TROUGH ALONG 28N78W TO 25N82W. CURRENTLY SHOWERS AND THUNDERSTORMS ARE JUST OFF THE WEST COAST OF THE PENINSULA FROM 27N-29N BETWEEN 83W-85W. RADAR IMAGERY ALSO INDICATES HEAVY SHOWERS ARE FROM 27N-28N BETWEEN 80W-81W. THE SECOND UPPER LOW...MUCH WEAKER THAN THE FIRST...IS TO THE SOUTH NEAR 22N90W PROVIDING DIFFLUENT ALOFT OVER THE YUCATAN PENINSULA. SCATTERED SHOWERS/THUNDERSTORMS ARE THROUGHOUT THE PENINSULA AND ACROSS MUCH OF THE REST OF MEXICO AS WELL. SHOWERS/THUNDERSTORMS ARE ALSO MOVING THROUGH THE NW GULF TOWARDS TEXAS ASSOCIATED WITH ANOTHER AREA OF DIFFLUENT FLOW ALOFT ASSOCIATED WITH AN UPPER LEVEL LOW OVER NEW MEXICO. AT THE SURFACE...BROAD RIDGING IS THROUGHOUT EXTENDING FROM A HIGH CENTER OVER ILLINOIS. THIS PATTER IS PROVIDING MAINLY EAST TO SOUTHWEST FLOW OF 10-15 KT WITH A FEW 20 KT WINDS OVER THE NORTH CENTRAL GULF. THE SURFACE TROUGH OVER FLORIDA IS EXPECT TO SLOWLY DRIFT WESTWARD THROUGH THE END OF THE WEEK BEFORE DISSIPATING INLAND OVER THE WEEKEND. THE STRONG UPPER LOW OVER FLORIDA IS ALSO EXPECTED TO DRIFT WEST WHICH WILL PROVIDE A WIDE AREA OF DIFFLUENCE OVER THE EASTERN/CENTRAL GULF LEADING TO SHOWERS/THUNDERSTORMS. CARIBBEAN SEA... WEAK UPPER RIDGING IS OVER THE WESTERN CARIBBEAN. DIFFLUENT FLOW WEST OF THE UPPER RIDGE IS SUPPORTING HEAVY SHOWERS/THUNDERSTORMS OVER BOTH THE NW CARIBBEAN AND THROUGHOUT CENTRAL AMERICA. ACTIVITY OVER THE NW CORNER IS FROM 19N-22N BETWEEN 80W-87W CONTINUING OVER MUCH OF CUBA. ACTIVITY OVER CENTRAL AMERICA IS MAINLY BETWEEN 84W-88W WITH THE STRONGEST ACTIVITY OVER COSTA RICA. ACTIVITY ALSO CONTINUES THROUGH PANAMA ASSOCIATED WITH THE MONSOON TROUGH EXTENDING ALONG 10N TO A 1008 MB SURFACE LOW OVER NORTHERN COLOMBIA. FARTHER EAST...TWO TROPICAL WAVES ARE MOVING THROUGH THE BASIN. THE FIRST IS ALONG 75W...BUT IS NOT ACCOMPANIED BY MUCH MOISTURE LEAVING THIS PORTION OF THE BASIN FAIRLY DRY. DRY AIR ALOFT AROUND A BROAD UPPER TROUGH ALONG 70W IS ALSO CONTRIBUTING TO THE FAIR WEATHER. THE SECOND WAVE IS MOVING THROUGH THE LESSER ANTILLES PROVIDING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS NORTH OF 13N EAST OF 69W. TRADEWIND FLOW OF 15-25 KT IS THROUGHOUT MUCH OF THE AREA WITH THE STRONGEST WINDS IN THE CENTRAL CARIBBEAN. THE WAVE IN THE CENTRAL CARIBBEAN WILL CONTINUE TO MOVE WEST...BUT WILL LIKELY DISSIPATE SOON. THE SECOND WAVE SHOULD CONTINUE THROUGH THE EASTERN CARIBBEAN INTO THE CENTRAL CARIBBEAN PRODUCING SCATTERED SHOWERS...SOME HEAVY AT TIMES. HISPANIOLA... ONLY A SMALL CLUSTER OF SHOWERS/THUNDERSTORMS IS OVER HAITI FROM 19N-20N BETWEEN 72W-73W. THIS IS LIKELY A RESULT OF DAYTIME HEATING WITH LITTLE INFLUENCE FROM THE WEAK TROPICAL WAVE TO THE WEST. A SECOND STRONGER TROPICAL WAVE IS EXPECTED TO REACH THE ISLAND WITHIN THE NEXT 24 HOURS AND WILL INCREASE MOISTURE AND CONVECTION. ATLANTIC OCEAN... THE UPPER LEVEL LOW OVER THE EASTERN GULF OF MEXICO IS PROVIDING DIFFLUENCE ALOFT OVER THE WEST ATLC SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 23N-28N BETWEEN 74W-78W. A WEAK UPPER RIDGE IS ALONG 76W WHILE AN ELONGATED UPPER LOW IS FARTHER EAST SUPPORTING A SURFACE TROUGH FROM 30N67W TO 26N70W. ISOLATED SHOWERS/THUNDERSTORMS ARE FROM 29N-30N BETWEEN 65W-68W. THE REMAINDER OF THE BASIN IS DOMINATED BY BROAD SURFACE RIDGING ANCHORED BY A 1025 MB HIGH NEAR 28N44W. THE RIDGE IS SUPPORTED BY BROAD UPPER RIDGING CENTERED NEAR 20N31W. A DRY SAHARAN AIR LAYER ALSO COVERS MUCH OF THE TROPICAL ATLC FROM THE COAST OF AFRICA AROUND THE TROPICAL WAVE TO NEAR 50W. 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