000 AXNT20 KNHC 071807 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SAT SEP 07 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. ...SPECIAL FEATURES... A TROPICAL WAVE ASSOCIATED WITH A 1008 MB LOW PRESSURE CENTER IS OVER SENEGAL AFRICA AND IS EXPECTED TO COME OFF THE WEST AFRICAN COAST LATER THIS AFTERNOON. TOTAL PRECIPITABLE WATER IMAGERY SHOW A ZONE OF MAXIMUM MOISTURE RIGHT OFF THE COAST WHICH ALONG WITH LOW DEEP LAYER ENVIRONMENTAL WIND SHEAR MAY ASSIST IN THE ORGANIZATION OF THIS SYSTEM. SPIRAL RAINBANDS ARE FROM 07N-18N E OF 26W. THIS SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ...TROPICAL WAVES... A TROPICAL WAVE ASSOCIATED WITH A 1009 MB LOW PRESSURE CENTER IS IN THE CENTRAL TROPICAL ATLC. THE WAVE AXIS IS ALONG 20N34W TO THE LOW CENTER NEAR 13N34W TO 11N34W WHERE A BLOCKING PATTERN IN THE MIDDLE TO UPPER LEVELS MAINTAINS THIS SYSTEM NEARLY STATIONARY. TOTAL PRECIPITABLE WATER IMAGERY INDICATE THAT MOISTURE WITHIN THE WAVE ENVIRONMENT HAS BEEN AUGMENTING IN THE PAST SEVERAL HOURS. HOWEVER...SAHARAN DRY AIR MOSTLY TO THE W OF THE AXIS IS LIMITING CONVECTIVE ACTIVITY. SCATTERED MODERATE CONVECTION IS FROM 14N-19N BETWEEN 28W-33W AND WITHIN 120 NM W OF THE AXIS FROM 16N-18N. A TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN EXTENDING AN AXIS FROM 19N79W TO 08N80W WHICH MOVES W NEAR 5 KT. THE WAVE CONTINUES EMBEDDED WITHIN AN AREA OF HIGH MOISTURE THAT COVERS THIS REGION OF THE CARIBBEAN AS DEPICTED ON TOTAL PRECIPITABLE WATER IMAGERY. CLUSTERS OF MODERATE CONVECTION WITH EMBEDDED TSTMS ASSOCIATED WITH THE WAVE AND THE MONSOON TROUGH ARE S OF 12N W OF 81W AS WELL AS S OF 13N E OF 79W. SCATTERED MODERATE CONVECTION AND TSTMS IN THE NORTHERN REGION OF THE WAVE ARE FROM 15N-20N BETWEEN 78W-84W. A WEAK TROPICAL WAVE IN THE FAR W CARIBBEAN WILL BE ENTERING THE YUCATAN PENINSULA AND GUATEMALA LATER THIS AFTERNOON. CURRENTLY...ITS AXIS IS ALONG 20N87W TO 11N88W AND HAS BEEN MOVING NEAR 5 KT. AN ELONGATED UPPER LEVEL TROUGH SUPPORTS IT AND IS ENHANCING SCATTERED MODERATE CONVECTION FROM 19N-21N BETWEEN 84W-87W. THIS WAVE IS EXPECTED TO DISSIPATE IN LESS THAN 24 HOURS. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS ACROSS AFRICA INTO THE E TROPICAL ATLC NEAR 13N16W AND CONTINUES ALONG 13N26W THROUGH THE LOW/TROPICAL WAVE NEAR 13N34W TO 08N43W. THE ITCZ BEGINS NEAR 08N34W AND CONTINUES ALONG 08N50W TO 11N57W. BESIDES THE CONVECTION ASSOCIATED WITH THE TRPCL WAVE ALREADY DISCUSSED...SPIRAL RAINBANDS ASSOCIATED WITH A 1008 MB LOW PRESSURE OVER SENEGAL ARE FROM 07N-16N E OF 27W. ...DISCUSSION... GULF OF MEXICO... A SURFACE TROUGH IS ALONG THE WESTERN GULF FROM 27N97W TO 18N94W. THIS TROUGH IS LOCATED IN AN AREA OF UPPER-LEVEL DIFFLUENCE WHICH IS SUPPORTING NUMEROUS MODERATE CONVECTION AND TSTMS S OF 29N W OF 89W. A BROAD UPPER-LEVEL TROUGH COVERS THE NORTH-CENTRAL AND EASTERN GULF E OF 90W AND SUPPORTS TWO SURFACE TROUGHS. THE FIRST TROUGH EXTENDS FROM 27N87W TO 28N95W AND IS GENERATING SHOWERS AND TSTMS N OF 27N W OF 88W. THE SECOND TROUGH MOVES FROM THE WESTERN BAHAMAS TO THE STRAITS OF FLORIDA AND IS GENERATING SHOWERS AND TSTMS OVER SOUTHERN FLORIDA AS WELL AS THE SE GULF S OF 26N E OF 86W. WEAK SURFACE RIDGING WILL PERSIST ACROSS THE N GULF THROUGH SUN NIGHT BEFORE IT IS REPLACED BY STRONGER HIGH PRESSURE FROM THE W ATLC. CARIBBEAN SEA... A TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN EXTENDING AN AXIS FROM 19N79W TO 08N80W. THE WAVE CONTINUES EMBEDDED WITHIN AN AREA OF HIGH MOISTURE THAT COVERS THIS REGION OF THE CARIBBEAN AS DEPICTED ON TOTAL PRECIPITABLE WATER IMAGERY. CLUSTERS OF MODERATE CONVECTION WITH EMBEDDED TSTMS ASSOCIATED WITH THE WAVE AND THE MONSOON TROUGH ARE S OF 12N W OF 81W AS WELL AS S OF 13N E OF 79W. SCATTERED MODERATE CONVECTION AND TSTMS IN THE NORTHERN REGION OF THE WAVE ARE FROM 15N-20N BETWEEN 78W-84W. A WEAK TROPICAL WAVE IS IN THE FAR W CARIBBEAN WITH AXIS EXTENDING ALONG 20N87W TO 11N88W. AN ELONGATED UPPER LEVEL TROUGH SUPPORTS IT AND IS ENHANCING SCATTERED MODERATE CONVECTION FROM 19N-21N BETWEEN 84W-87W. MIDDLE-LEVEL DIFFLUENCE CONTINUES TO SUPPORT THE CONVECTION ASSOCIATED WITH THE REMNANTS OF GABRIELLE. SCATTERED SHOWERS AND TSTMS ARE ACROSS HISPANIOLA...THE MONA PASSAGE AS WELL AS THE EASTERN CARIBBEAN N OF 13N BETWEEN 64W- 75W. THE REMNANT LOW OF GABRIELLE WILL CONTINUE TO MOVE AWAY FROM THE CARIBBEAN THROUGH SUN. FRESH SE WINDS WILL DEVELOP ACROSS MUCH OF THE E CARIBBEAN THROUGH SUN. THE W CARIBBEAN TROPICAL WAVE WILL MOVE OVER THE YUCATAN LATER THIS AFTERNOON. THE CENTRAL CARIBBEAN TROPICAL WAVE WILL MOVE INLAND OVER CENTRAL AMERICA TONIGHT. HISPANIOLA... SCATTERED SHOWERS AND THUNDERSTORMS REMAIN ACROSS THE ISLAND BEING SUPPORTED BY MIDDLE-LEVEL DIFFLUENCE. THIS CONVECTION ASSOCIATED WITH THE REMNANTS OF GABRIELLE COULD CONTINUE THROUGH SUN WHEN THE LOW WILL DISSIPATE AS THE SURFACE TROUGH DRIFTS W. ATLANTIC OCEAN... A BROAD UPPER-LEVEL TROUGH COVERS THE W ATLC N OF 26N WHICH SUPPORTS A SURFACE TROUGH THAT EXTENDS FROM THE WESTERN BAHAMAS TO THE STRAITS OF FLORIDA. THIS TROUGH IS GENERATING SHOWERS AND TSTMS FROM 24N-28N W OF 77W. THE UPPER-LEVEL TROUGH ALSO SUPPORTS A 1009 MB LOW PRESSURE CENTER NEAR 22N69W WHICH IS ASSOCIATED WITH THE REMNANTS OF GABRIELLE. A SURFACE TROUGH EXTENDS N-NE FROM THE LOW ALONG 22N69W TO 28N67W TO 32N64W. THIS SYSTEM IS GENERATING SCATTERED MODERATE SHOWERS/ISOLATED THUNDERSTORMS FROM 18N-25N BETWEEN 64W-69W AS WELL AS N OF 20N BETWEEN 54W-65W. ANOTHER SURFACE TROUGH EXTENDS FROM 33N42W TO 26N43W BUT HAS NO CONVECTION ASSOCIATED WITH IT. BESIDES THE TRPCL WAVES ALREADY DISCUSSED...THE REMAINDER OF THE ATLC IS DOMINATED BY A SURFACE RIDGE ANCHORED BY A SET OF HIGH PRESSURE CENTERS N OF THE DISCUSSION AREA. THE REMNANT LOW OF GABRIELLE WILL MOVE SLOWLY NW TO N. THE SURFACE TROUGH IS EXPECTED TO DRIFT W THROUGH TONIGHT WHILE THE LOW IS EXPECTED TO DISSIPATE TUE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ NR