000 AXNT20 KNHC 201733 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT FRI SEP 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 10N17W TO 17N18W MOVING W AT 10-15 KT. THE WAVE REMAINS EMBEDDED WITHIN THE MONSOON TROUGH AND COINCIDES WITH A SURFACE TO 700 MB TROUGH AND 700 MB RELATIVE VORTICITY MAXIMUM IN THE VICINITY OF 14N18W ALONG THE WAVE AXIS. WIDELY SCATTERED MODERATE CONVECTION IS FROM 05N-12N BETWEEN 14W- 22W...AND FROM 15N-18N BETWEEN 14W-20W. TROPICAL WAVE EXTENDS FROM 14N34W TO 24N34W MOVING W AT 10-15 KT. TOTAL PRECIPITABLE WATER IMAGERY INDICATES MOST OF THE WAVE HAS BEEN UNDERCUT BY A RELATIVELY DRIER AIRMASS WHICH CONTINUES TO LIMIT CONVECTION AT THIS TIME. ISOLATED MODERATE CONVECTION IS FROM 21N-24N BETWEEN 29W-35W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N16W TO 11N22W TO A 1012 MB LOW NEAR 11N30W TO 08N35W TO 07N43W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N43W TO 05N53W. SCATTERED MODERATE CONVECTION IS FROM 04N-16N BETWEEN 25W-33W...AND FROM 05N-09N BETWEEN 33W-41W. ...DISCUSSION... GULF OF MEXICO... NORTHERLY UPPER LEVEL FLOW DOMINATES OVER THE GULF BASIN THIS AFTERNOON BETWEEN AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER MEXICO NEAR 23N100W AND AN UPPER LEVEL TROUGH AXIS EXTENDING FROM OVER THE SW NORTH ATLC NEAR 28N77W TO OVER THE NORTHERN YUCATAN PENINSULA NEAR 21N87W. WATER VAPOR IMAGERY INDICATES THE AIRMASS USHERED IN ON THE NORTHERLY FLOW REMAINS RELATIVELY DRY AND STABLE WITH MOSTLY CLEAR SKIES AND FAIR CONDITIONS NOTED E OF 91W. THE ONLY EXCEPTION TO THE FAIR SKIES ARE A FEW ISOLATED SHOWERS AND TSTMS OCCURRING WITHIN 90 NM EITHER SIDE OF A LINE FROM 29N85W TO 25N83W. OTHERWISE...SURFACE RIDGING EXTENDS SOUTHWARD FROM THE CAROLINAS ACROSS THE FLORIDA PENINSULA TO THE NORTHWEST CARIBBEAN SEA. FINALLY...ACROSS THE WESTERN GULF...A 1002 MB LOW IS CENTERED NEAR 22N97W THAT CONTINUES TO STRUGGLE IN SUSTAINING ANY ORGANIZED CONVECTION AT THIS TIME. SCATTERED MODERATE CONVECTION IS PRIMARILY OCCURRING WITHIN 150 NM OF CENTER WITHIN THE SOUTHERN QUADRANT. THE LACK OF ORGANIZATION IS DUE TO NORTHWESTERLY SHEAR AND A DRIER AIRMASS LOCATED OVER PORTIONS OF THE EASTERN AND CENTRAL GULF OF MEXICO. THE GREATEST IMPACT FROM THIS LOW WILL CONTINUE TO BE LOCALLY HEAVY RAINFALL AT TIMES OVER PORTIONS OF EASTERN AND SOUTHERN MEXICO THROUGH THE WEEKEND. SOUTHEAST WINDS IN THE RANGE OF 15 TO 25 KT ARE FORECAST TO CONTINUE THROUGH EARLY SATURDAY AS THE LOW DRIFTS NORTHWARD TOWARDS THE TEXAS GULF COAST. THEREAFTER FOR THE REMAINDER OF THE WEEKEND... GLOBAL MODELS SUGGEST THE LOW WILL BE POSITIONED ACROSS THE NW GULF WATERS AT THE TAIL END OF A WEAK FRONTAL BOUNDARY DRAPED ALONG THE GULF COASTAL PLAINS. CARIBBEAN SEA... AN UPPER LEVEL RIDGE AXIS EXTENDS ACROSS THE WESTERN CARIBBEAN FROM OVER HISPANIOLA NEAR 18N71W WESTWARD TO OVER CENTRAL AMERICA NEAR 14N87W THAT IS PROVIDING AN OVERALL UPPER LEVEL DIFFLUENT ENVIRONMENT W OF 70W. THIS UPPER LEVEL REGIME ALONG WITH THE MONSOON TROUGH AXIS ANALYZED ALONG THE SPINE OF CENTRAL AMERICA FROM NORTHERN COLOMBIA TO GUATEMALA IS GENERATING WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS W OF 75W. THE REMAINDER OF THE CENTRAL AND EASTERN CARIBBEAN IS UNDER THE INFLUENCE OF A RELATIVELY DRIER AIRMASS NOTED ON WATER VAPOR IMAGERY...WHICH IS KEEPING SKIES MOSTLY CLEAR THIS AFTERNOON. A FEW ISOLATED SHOWERS ARE NOTED HOWEVER SOUTH OF PUERTO RICO NEAR 17N66W AND ACROSS THE SOUTHERN WINDWARD ISLANDS S OF 13N E OF 63W. LOOKING AHEAD...A SURFACE TROUGH IS ANALYZED EAST OF THE LESSER ANTILLES ALONG 55W AND IS EXPECTED TO BEGIN IMPACTING THE ISLANDS BY EARLY SUNDAY INTO MONDAY WITH INCREASED CLOUDINESS AND PRECIPITATION. HISPANIOLA... CURRENTLY SKIES REMAIN FAIR THIS AFTERNOON...HOWEVER WITH AN UPPER LEVEL DIFFLUENT ENVIRONMENT NOTED ON WATER VAPOR IMAGERY ACROSS THE ISLAND STRETCHING WESTWARD OVER THE WESTERN CARIBBEAN SEA...SCATTERED SHOWER AND TSTM ACTIVITY IS FORECAST TO INITIATE LATE THIS AFTERNOON AND CONTINUE THROUGH THE EVENING HOURS. THIS OVERALL SYNOPTIC PATTERN IS EXPECTED TO CHANGE LITTLE OVER THE NEXT FEW DAYS WITH AFTERNOON AND EARLY EVENING CONVECTION ANTICIPATED ACROSS THE ISLAND. ATLANTIC OCEAN... A MIDDLE TO UPPER LEVEL LOW IS CENTERED OVER THE WESTERN NORTH ATLC NEAR 36N70W THAT EXTENDS A TROUGH AXIS SOUTHWESTWARD TO 31N73W TO 24N82W. THIS TROUGHING SUPPORTS A STATIONARY FRONT THAT ENTERS THE DISCUSSION AREA NEAR 32N46W EXTENDING W-SW INTO A 1010 MB LOW CENTERED NEAR 27N64W. A SURFACE TROUGH THEN EXTENDS W-SW FROM THE LOW TO THE SE BAHAMAS NEAR 23N74W TO THE COAST OF CENTRAL CUBA NEAR 22N78W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 180 NM EITHER SIDE OF A LINE FROM 30N59W TO 22N68W WITH WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS OCCURRING ELSEWHERE WITHIN 120 NM EITHER SIDE OF THE FRONT E OF 57W...AND FROM 20N-25N BETWEEN 69W-81W. TO THE SOUTHEAST...AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 14N57W AND IS PROVIDING A FAVORABLE UPPER LEVEL DIFFLUENT ENVIRONMENT FOR A 1014 MB LOW CENTERED NEAR 14N55W. SCATTERED SHOWERS AND WIDELY SCATTERED TSTMS ARE OCCURRING IN CLOSE PROXIMITY TO THE LOW CENTER FROM 12N-16N BETWEEN 52W-57W. FINALLY...THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1026 MB HIGH CENTERED EAST OF THE AZORES NEAR 40N21W. 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