000 AXNT20 KNHC 181750 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU JUL 18 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 09N35W TO 20N32W MOVING W AT 15-20 KT. THE WAVE COINCIDES WITH AN AMPLIFIED GLOBAL MODEL INDICATED 700 MB TROUGH AXIS ALONG 34W AND MATCHING TOTAL PRECIPITABLE WATER IMAGERY MAXIMUM FROM 08N-20N BETWEEN 24W-34W...PRIMARILY TO THE EAST OF THE WAVE AXIS. NO SIGNIFICANT DEEP CONVECTION ASSOCIATED THE WAVE AT THIS TIME DUE TO THE STABLING EFFECT OF THE SAHARAN AIR LAYER ACROSS THE EASTERN ATLC. TROPICAL WAVE EXTENDS FROM 11N69W TO 20N66W MOVING W AT 20-25 KT. THE WAVE IS ASSOCIATED WITH BROAD LOWER LEVEL TROUGHING ACROSS THE EASTERN CARIBBEAN WITH TOTAL PRECIPITABLE WATER IMAGERY INDICATING A MAXIMUM FROM 14N-22N BETWEEN 61W- 70W...STRETCHING TO THE NE OVER PORTIONS OF THE CENTRAL ATLC. SCATTERED MODERATE CONVECTION HAS SUSTAINED ITSELF OVER THE PAST 24 TO 36 HOURS AND CONTINUES FROM 17N-22N BETWEEN 62W-69W...WITH WIDELY SCATTERED SHOWERS COVERING A LARGER AREA FROM 14N-22N BETWEEN 61W-72W. TROPICAL WAVE EXTENDS FROM 07N79W TO 14N77W MOVING W AT 15-20 KT. THE WAVE CONTINUES TO PROGRESS ACROSS THE SW CARIBBEAN SEA BENEATH NORTHERLY FLOW ALOFT...WHICH IS LIMITING SIGNIFICANT DEEP CONVECTION TO AN AREA S OF 10N...HOWEVER THE WAVE COINCIDES WITH A WEAK 700 MB TROUGH AND AREA OF MAXIMUM VORTICITY IN THE VICINITY OF 11N78W. THE WAVE IS EXPECTED TO CROSS PORTIONS OF CENTRAL AMERICA THIS AFTERNOON INTO EARLY FRIDAY AND EMERGE INTO THE EASTERN PACIFIC REGION THEREAFTER. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION STRATTLES PANAMA FROM 04N-10N BETWEEN 76W-81W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 11N16W TO 10N22W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 10N22W TO 12N30W TO 07N38W TO 04N51W. ISOLATED MODERATE CONVECTION IS FROM 06N-12N BETWEEN 12W-19W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 04N-10N BETWEEN 35W-59W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES A UPPER LEVEL LOW IS CENTERED OVER THE NORTH-CENTRAL GULF NEAR 28N89W THAT CONTINUES TO CREATE LIFT AND ADVECT MOISTURE OVER PORTIONS OF THE EASTERN GULF AND FLORIDA PENINSULA...AS WELL AS PORTIONS OF THE WESTERN GULF THIS AFTERNOON. MUCH OF THE PRECIPITATION AND CONVECTION IS FOCUSED ALONG A PAIR OF SURFACE TROUGHS...ONE ANALYZED ACROSS THE SOUTHERN FLORIDA PENINSULA TO 27N82W TO 23N90W...AND THE OTHER ANALYZED FROM ACROSS SOUTHERN TEXAS NEAR 28N98W TO 21N95W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING FROM 23N-28N BETWEEN 81W-88W WITH THE EASTERN-MOST SURFACE TROUGH AND FROM 24N-28N BETWEEN 92W-98W WITH THE WESTERN-MOST SURFACE TROUGH. THE TROUGHING ACROSS THE FLORIDA PENINSULA AND SE GULF WILL CONTINUE TO DRIFT SLOWLY WEST-NORTHWESTWARD DURING THE NEXT COUPLE OF DAYS EVENTUALLY DISSIPATING ALONG THE LOUISIANA AND TEXAS GULF COAST IN THE NW GULF EARLY SATURDAY. THEREAFTER...SURFACE RIDGING ANCHORED IN THE SW NORTH ATLC WILL EXTEND WESTWARD AND ONCE AGAIN RE-ESTABLISH SE TO S WINDS ACROSS THE BASIN OVER THE WEEKEND. CARIBBEAN SEA... A WEAK UPPER LEVEL LOW IS CENTERED OVER THE SE CARIBBEAN NEAR 15N66W WITH CYCLONIC FLOW REACHING AS FAR NORTH AS 20N BETWEEN 61W-72W. UPPER LEVEL DIFFLUENCE IS ASSOCIATED WITH THE TROUGHING ON ITS NORTHERN PERIPHERY...AND WITH THE PRESENCE OF A TROPICAL WAVE...ANALYZED FROM NORTH OF PUERTO RICO NEAR 20N66W TO CURACAO NEAR 12N69W...INCREASED MOISTURE AND CLOUDINESS ALONG WITH SCATTERED SHOWERS AND TSTMS ARE NOTED ON SATELLITE IMAGERY FROM 15N-22N BETWEEN 61W-72W. THIS TROPICAL WAVE IS FORECAST TO CONTINUE WESTWARD AND INCREASE PRECIPITATION CHANCES FOR JAMAICA AND HISPANIOLA OVER THE WEEKEND. ANOTHER TROPICAL WAVE IS ANALYZED ACROSS THE SW CARIBBEAN ALONG 79W AND CONTINUES MOVING BENEATH NORTHERLY FLOW ALOFT AT THIS TIME. ENERGY ASSOCIATED WITH THE WAVE IS EXPECTED TO CROSS CENTRAL AMERICA OVER THE WEEKEND AND EMERGE INTO THE OPEN WATERS OF THE EASTERN PACIFIC. LOW-LEVEL MOISTURE CONVERGENCE REMAINS MAXIMIZED ACROSS THE SW CARIBBEAN S OF 13N WITH SCATTERED SHOWERS AND TSTMS OCCURRING BETWEEN 76W-84W. THIS CONVECTION IS ALSO LIKELY ENHANCED DUE TO CLOSE PROXIMITY OF THE MONSOON TROUGH ALONG 09N/10N ACROSS WESTERN PANAMA AND COSTA RICA. FINALLY...WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING OVER THE NW CARIBBEAN N OF 16N BETWEEN 81W-88W. THE CONVECTION IS OCCURRING WITHIN AN AREA OF MAXIMUM MIDDLE TO UPPER LEVEL DIFFLUENCE SOUTH OF AN UPPER LEVEL LOW CENTERED OVER THE NORTH-CENTRAL GULF OF MEXICO. HISPANIOLA... MOISTURE CONTINUES TO INCREASE ACROSS THE ISLAND THIS AFTERNOON AS A TROPICAL WAVE CURRENTLY ANALYZED ACROSS PUERTO RICO CONTINUES MOVING WESTWARD. LOW-LEVEL MOISTURE CONVERGENCE ABOUT THE WAVE AXIS AND UPPER LEVEL DIFFLUENCE MAXIMIZED ON THE NORTHERN PERIPHERY OF AN UPPER LEVEL LOW CENTERED OVER THE SE CARIBBEAN IS GENERATING SCATTERED SHOWERS AND TSTMS FROM 16N-22N BETWEEN 62W-72W. THE STRONGEST OF THIS ACTIVITY CURRENTLY IS ACROSS AND IMMEDIATELY NORTH OF PUERTO RICO. AS THIS AREA OF PRECIPITATION AND CONVECTION MOVES WESTWARD OVER THE NEXT 24 TO 36 HOURS...HEAVY RAINFALL AND A HIGH POTENTIAL FOR LOCALIZED FLOODING IS POSSIBLE. ATLANTIC OCEAN... AN UPPER LEVEL LOW IS CENTERED OVER THE NORTH-CENTRAL GULF OF MEXICO NEAR 28N89W THAT SUPPORTS A SURFACE TROUGH ANALYZED FROM OFF THE EASTERN COAST OF THE FLORIDA PENINSULA NEAR 29N79W TO27N82W AND INTO THE SE GULF OF MEXICO. LOW-LEVEL MOISTURE CONVERGENCE ALONG WITH MIDDLE TO UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE TROUGHING AND UPPER LEVEL LOW IS GENERATING SCATTERED SHOWERS AND TSTMS FROM 23N-30N BETWEEN 75W-82W... INCLUDING THE BAHAMAS AND MUCH OF THE FLORIDA PENINSULA. FARTHER EAST...A COMPLEX AREA OF UPPER LEVEL TROUGHING EXTENDS FROM 27N55W TO 26N71W THAT IS GENERATING ISOLATED SHOWERS AND TSTMS FROM 23N-27N BETWEEN 67W-75W. OTHERWISE...THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A PAIR OF 1025 MB HIGHS CENTERED NEAR 27N49W AND 28N57W. ANOTHER HIGH IS CENTERED BETWEEN THE AZORES AND MADEIRA ISLANDS NEAR 34N20W AS A 1025 MB HIGH. SATELLITE IMAGERY INDICATES THE SAHARAN AIR LAYER CONTINUES TO IMPACT MUCH OF THE EASTERN AND CENTRAL ATLC GENERALLY N OF 12N E OF 60W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN