000 AXNT20 KNHC 201148 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURES... DROPWINDSONDE DATA FROM THE NASA GLOBAL HAWK SAMPLED 1002 MB FOR THE LOW PRESSURE CENTER IN THE GULF LOCATED NEAR 21N96W AT 20/0900 UTC. THIS AREA OF LOW PRESSURE IS WITHIN A ZONE OF VERY MOIST AIR AS DEPICTED IN TOTAL PRECIPITABLE WATER IMAGERY. HOWEVER...STRONG NORTHWESTERLY WIND SHEAR IN THE VICINITY OF THE LOW IS HINDERING IN PART CONVECTIVE ACTIVITY. MIDDLE-LEVEL DIFFLUENCE W-SW OF THE LOW CENTER IS SUPPORTING SCATTERED MODERATE CONVECTION S OF 21N W OF 95W. UPPER-LEVEL DIFFLUENCE SE OF THE LOW SUPPORTS SCATTERED MODERATE/ISOLATED STRONG CONVECTION S OF 20N BETWEEN 91W-94W AS WELL AS INLAND SOUTHERN MEXICO AND GUATEMALA. ENVIRONMENTAL CONDITIONS ARE ONLY MARGINALLY CONDUCIVE AND SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS BECOMING LESS LIKELY THUS GIVING IT A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. THIS DISTURBANCE WILL CONTINUE TO PRODUCE LOCALLY HEAVY RAINS OVER PORTIONS OF EASTERN AND SOUTHERN MEXICO DURING THE NEXT FEW DAYS. ...TROPICAL WAVES... THE AXIS OF A TROPICAL WAVE EXTENDS ALONG 22N33W TO 10N33W AND IS MOVING W NEAR 10-15 KNOTS. TOTAL PRECIPITABLE WATER IMAGERY SHOW MOST OF THE WAVE ENVIRONMENT HAS BEEN UNDERCUT BY VERY DRY AIR WHICH IS LIMITING CONVECTION. SCATTERED MODERATE CONVECTION IS IN THE NORTHERN SECTOR OF THE WAVE AXIS FROM 21N-23N BETWEEN 31W-34W AND SE OF THE AXIS FROM 12N-15N BETWEEN 28W-31W. THESE AREAS OF CONVECTION COINCIDE WITH SMALL SECTORS OF MODERATE TO VERY MOIST AIR IN TOTAL PRECIPITABLE WATER IMAGERY. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH PASSES THROUGH COASTAL WEST AFRICA NEAR 11N16W TO 10N30W 07N39W. THE ITCZ CONTINUES FROM 07N39W TO 11N53W. SCATTERED MODERATE CONVECTION IS FROM 06N-12N E OF 21W...FROM 06N-11N BETWEEN 26W-40W AS WELL AS FROM 08N-10N BETWEEN 43W-49W. ...DISCUSSION... GULF OF MEXICO... A VERY MOIST ENVIRONMENT AT THE LOWER LEVELS DOMINATE THE WESTERN GULF WATERS AS DEPICTED IN IMAGERY OF TOTAL PRECIPITABLE WATER. HOWEVER...STRONG NORTHWESTERLY WIND SHEAR ACROSS GREAT PORTIONS OF THE BASIN INHIBITS IN PART CONVECTIVE ACTIVITY THIS MORNING. A 1002 MB LOW CENTER IS IN THE BAY OF CAMPECHE NEAR 21N96W. MIDDLE-LEVEL DIFFLUENCE W-SW OF THE LOW CENTER IS SUPPORTING SCATTERED MODERATE CONVECTION S OF 21N W OF 95W. UPPER-LEVEL DIFFLUENCE SE OF THE LOW SUPPORTS SCATTERED MODERATE/ISOLATED STRONG CONVECTION S OF 20N BETWEEN 91W-94W AS WELL AS INLAND SOUTHERN MEXICO AND GUATEMALA. SEE THE SPECIAL FEATURES SECTION FOR MORE INFORMATION ABOUT THIS DISTURBANCE. SCATTERED SHOWERS ARE NW OF THE BASIN N OF 28N BETWEEN 92W-96W. AN UPPER-LEVEL TROUGH EXTENDS ACROSS THE FLORIDA PENINSULA AND THE STRAITS SUPPORTING ISOLATED SHOWERS OVER THE EASTERN GULF E OF 85W. THE DISTURBANCE IN THE SW GULF HAS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. THIS SYSTEM WILL CONTINUE TO PRODUCE LOCALLY HEAVY RAINS OVER PORTIONS OF EASTERN AND SOUTHERN MEXICO DURING THE NEXT FEW DAYS. A COLD FRONT IS EXPECTED TO ENTER THE NORTHERN GULF WATERS BY SATURDAY AFTERNOON. CARIBBEAN SEA... TOTAL PRECIPITABLE WATER IMAGERY SHOW A REDUCTION IN MOISTURE ACROSS GREAT PORTIONS OF THE BASIN THIS MORNING. MIDDLE TO UPPER LEVEL DIFFLUENT FLOW IN THE NW CARIBBEAN BASIN ENHANCES SCATTERED SHOWERS N OF 16N W OF 74W. ISOLATED SHOWERS ARE ELSEWHERE IN THE BASIN EXCEPT E OF 70W WHERE FAIR WEATHER DOMINATES. A SURFACE TROUGH IS EXPECTED TO ENTER THE EASTERN CARIBBEAN SEA EARLY SUNDAY AFTERNOON GENERATING SHOWERS POSSIBLY AFFECTING THE LESSER ANTILLES. HISPANIOLA... UPPER-LEVEL DIFFLUENCE FROM A TROUGH OVER THE N WESTERN ATLC AND A RIDGE COVERING WESTERN-CENTRAL CARIBBEAN SEA SUPPORTS CLOUDINESS AND ISOLATED SHOWERS OVER THE WINDWARD PASSAGE...HAITI AND WESTERN-CENTRAL DOMINICAN REPUBLIC. BESIDES THE TYPICAL AFTERNOON/EARLY EVENING SHOWERS ACTIVITY DUE TO SURFACE HEATING...CONVECTIVE ACTIVITY DUE TO THE UPPER-LEVEL FEATURES MENTIONED ABOVE IS EXPECTED TO CONTINUE UNTIL SATURDAY NIGHT. ATLANTIC OCEAN... AN UPPER-LEVEL TROUGH IN THE N WESTERN ATLC SUPPORTS A FRONTAL SYSTEM THAT ENTERS THE DISCUSSION AREA AS A COLD FRONT FROM 30N50W TO 29N55W WHERE IT TRANSITIONS TO A STATIONARY FRONT TO 28N61W. IN ADDITION...THE UPPER-LEVEL TROUGH SUPPORTS A SURFACE TROUGH ASSOCIATED WITH A 1011 MB LOW PRESSURE CENTER NEAR 26N68W. SCATTERED MODERATE CONVECTION AND TSTMS ASSOCIATED WITH THE FRONT AND THE LOW ARE FROM 21N-33N BETWEEN 59W-69W. DIFFLUENT FLOW ALOFT FROM THE UPPER-LEVEL TROUGH AND A RIDGE COVERING THE WESTERN-CENTRAL CARIBBEAN SUPPORTS SCATTERED SHOWERS IN THE BAHAMAS AND EASTERN CUBA. A SURFACE TROUGH EMBEDDED WITHIN A VERY MOIST ENVIRONMENT EXTENDS ALONG 18N52W TO 11N53W. SCATTERED MODERATE CONVECTION AND ISOLATED TSTMS IS FROM 12N-18N BETWEEN 48W-55W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ NR