000 AXNT20 KNHC 171750 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 10N26W TO 19N22W MOVING W AT 15-20 KT. THE WAVE COINCIDES WITH A HIGHLY AMPLIFIED GLOBAL MODEL INDICATED 700 MB TROUGH AXIS ALONG 25W AND MATCHING TOTAL PRECIPITABLE WATER IMAGERY SHOWS A MAXIMUM FROM 07N-19N BETWEEN 16W-25W...PRIMARILY TO THE EAST OF THE WAVE AXIS. WIDELY SCATTERED MODERATE CONVECTION IS FROM 07N-14N BETWEEN 18W-28W. TROPICAL WAVE EXTENDS FROM 12N60W TO 22N58W MOVING W AT 20-25 KT. THE WAVE...WHICH OVER THE PAST SEVERAL DAYS HAS CONTINUED TO BE INFLUENCED BY AN EXTENSIVE SAHARAN AIR LAYER...IS BEGINNING TO EMERGE FROM THAT INFLUENCE AND EXHIBIT A BIT MORE CONVECTIVE ACTIVITY AS IT APPROACHES THE LESSER ANTILLES AND EASTERN CARIBBEAN SEA THIS AFTERNOON INTO THURSDAY. SCATTERED MODERATE CONVECTION IS FROM 15N-19N BETWEEN 54W-60W...WITH WIDELY SCATTERED SHOWERS COVERING A LARGER AREA FROM 12N-20N BETWEEN 53W-65W. TROPICAL WAVE EXTENDS FROM 12N75W TO 19N72W MOVING W AT 20 KT. THE WAVE CONTINUES TO PROGRESS SWIFTLY ACROSS THE CARIBBEAN SEA BENEATH ANTICYCLONIC FLOW ALOFT...WHICH IS LIMITING ANY SIGNIFICANT DEEP CONVECTION AT THIS TIME...HOWEVER THE WAVE COINCIDES WITH A WEAK 700 MB TROUGH AND THE ENERGY ASSOCIATED WITH THE WAVE ON THE SOUTHERN EXTENT IS EXPECTED TO CROSS CENTRAL AMERICA AND EMERGE INTO THE EASTERN PACIFIC REGION BY EARLY FRIDAY. A FEW ISOLATED SHOWERS AND TSTMS ARE OCCURRING ACROSS EASTERN HISPANIOLA IN AN AREA OF LOW-LEVEL MOISTURE CONVERGENCE. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 20N17W TO 19N21W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 10N27W TO 02N46W. ASIDE FROM CONVECTION ASSOCIATED WITH THE TROPICAL WAVE ALONG 25W...WIDELY SCATTERED MODERATE CONVECTION IS FROM 05N-09N BETWEEN 27W-39W...AND FROM 02N-10N BETWEEN 39W- 50W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES A UPPER LEVEL LOW IS CENTERED OVER THE EASTERN GULF NEAR 27N84W THAT CONTINUES TO CREATE LIFT AND ADVECT MOISTURE OVER PORTIONS OF THE SW NORTH ATLC...THE FLORIDA PENINSULA...FLORIDA STRAITS...AND SE GULF THIS AFTERNOON. MUCH OF THE PRECIPITATION AND CONVECTION IS FOCUSED ALONG A SURFACE TROUGH ALONG THE EASTERN FLORIDA PENINSULA WITH SCATTERED SHOWERS AND TSTMS OCCURRING FROM 23N-27N BETWEEN 79W-87W. FARTHER WEST...NORTHERLY FLOW ALOFT DOMINATES W OF 90W WITH AN OVERALL WEAK SURFACE PRESSURE GRADIENT AND GENERALLY E-SE WINDS IN THE RANGE OF 10 TO 20 KT. MOSAIC DOPPLER RADAR IMAGERY AND LIGHTNING DATA INDICATE SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING OVER THE NW GULF N OF 25N W OF 90W...AND S OF 25N W OF 94W. THE CURRENT TROUGHING ACROSS THE FLORIDA PENINSULA WILL CONTINUE TO SLOWLY DRIFT WESTWARD DURING THE NEXT COUPLE OF DAYS EVENTUALLY SWINGING NORTHWESTWARD AND INLANDN ACROSS THE LOUISIANA AND TEXAS GULF COAST LATE FRIDAY. THEREAFTER...SURFACE RIDGING ANCHORED IN THE SW NORTH ATLC WILL EXTEND WESTWARD AND ONCE AGAIN RE-ESTABLISH E-SE WINDS ACROSS THE BASIN OVER THE WEEKEND. CARIBBEAN SEA... A WEAK UPPER LEVEL RIDGE AXIS EXTENDS FROM THE SOUTH-CENTRAL CARIBBEAN NEAR 12N69W NE INTO THE CENTRAL ATLC NEAR 19N54W. MARGINAL UPPER LEVEL DIFFLUENCE IS ASSOCIATED WITH THIS RIDGE...AND WITH THE PRESENCE OF A TROPICAL WAVE APPROACHING THE LESSER ANTILLES AND EASTERN CARIBBEAN...INCREASED MOISTURE AND PRECIPITATION IS EXPECTED OVER THE NEXT 24 TO 36 HOURS ACROSS THE ISLAND CHAIN. SCATTERED SHOWERS AND TSTMS ARE CURRENTLY EAST OF THE BASIN FROM 15N-19N BETWEEN 55W-61W...WITH ISOLATED SHOWERS ELSEWHERE FROM 13N-19N E OF 64W. THIS TROPICAL WAVE IS FORECAST TO CONTINUE WESTWARD AND INCREASE PRECIPITATION CHANCES FOR PUERTO RICO AND HISPANIOLA OVER THE WEEKEND. ANOTHER TROPICAL WAVE IS CURRENTLY ALONG 74W AND CONTINUES MOVING BENEATH STABLE ANTICYCLONIC 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 WEST OF THE TROPICAL WAVE ACROSS THE SW CARIBBEAN EXTENDING ALONG THE COAST OF NICARAGUA TO WESTERN PANAMA. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 120 NM EITHER SIDE OF A LINE FROM 13N84W TO 09N77W. THIS CONVECTION IS ALSO LIKELY ENHANCED DUE TO CLOSE PROXIMITY OF THE MONSOON TROUGH ALONG 08N/09N BETWEEN NORTHERN COLOMBIA AND SOUTHERN COSTA RICA. FINALLY...WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING OVER THE NW CARIBBEAN N OF 18N BETWEEN 79W-87W. THE CONVECTION IS OCCURRING WITHIN AN AREA OF MAXIMUM MIDDLE TO UPPER LEVEL DIFFLUENCE SOUTH OF AN UPPER LEVEL LOW CENTERED OVER THE EASTERN GULF OF MEXICO. HISPANIOLA... CURRENTLY A FEW ISOLATED SHOWERS AND TSTMS ARE OCCURRING ACROSS THE DOMINICAN REPUBLIC AS A TROPICAL WAVE IN THE VICINITY OF THE ISLAND CONTINUES TO MOVE WESTWARD. AFTERNOON AND EARLY EVENING SHOWERS AND TSTMS ARE EXPECTED DUE TO PEAK DAYTIME HEATING AND INSTABILITY AND WILL LIKELY DIMINISH BY LATE EVENING. SYNOPICALLY OVER THE NEXT 24 TO 48 HOURS...THE NEXT TROPICAL WAVE...CURRENTLY EAST OF THE LESSER ANTILLES...WILL BEGIN TO IMPACT HISPANIOLA INCREASING MOISTURE AND CLOUDINESS BY EARLY THURSDAY INTO FRIDAY WITH SCATTERED SHOWERS AND TSTMS POSSIBLE. ATLANTIC OCEAN... AN UPPER LEVEL LOW IS CENTERED OVER THE EASTERN GULF OF MEXICO NEAR 27N84W THAT SUPPORTS A SURFACE TROUGH ANALYZED ALONG THE EASTERN COAST OF THE FLORIDA PENINSULA. LOW-LEVEL MOISTURE CONVERGENCE ALONG WITH MIDDLE TO UPPER LEVEL DIFFLUENCE IS GENERATING SCATTERED SHOWERS AND TSTMS ACROSS A LARGE PORTION OF THE SW NORTH ATLC FROM 22N-28N BETWEEN 75W-82W...INCLUDING THE BAHAMAS AND MUCH OF THE SOUTHERN FLORIDA PENINSULA. FARTHER EAST...ANOTHER WEAKER UPPER LEVEL LOW IS CENTERED NEAR 28N70W THAT SUPPORTS A SURFACE TROUGH FROM 26N70W TO 30N68W. SCATTERER SHOWERS AND ISOLATED TSTMS ARE OCCURRING FROM 26N-30N BETWEEN 67W-69W. OTHERWISE...THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1025 MB HIGH CENTERED NEAR 27N46W. THE SAHARAN AIR LAYER CONTINUES TO IMPACT MUCH OF THE EASTERN ATLC WITH SUSPENDED DUST NOTED ON VISIBLE SATELLITE IMAGERY GENERALLY N OF 10N E OF 53W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN