000 AXNT20 KNHC 090545 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT FRI AUG 09 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0522 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS WEST OF THE CAPE VERDE ISLANDS WITH AXIS EXTENDING FROM 22N31W TO 10N31W MOVING W NEAR 10 KT. METEOSAT SATELLITE IMAGERY SHOW SAHARAN DRY AIR SPREADING OVER THE WAVE ENVIRONMENT WHICH IS HINDERING CONVECTION. A TROPICAL WAVE IS OVER THE WESTERN CARIBBEAN WITH AXIS EXTENDING FROM 23N79W TO 09N79W MOVING W NEAR 5 KT. THE WAVE IS EMBEDDED IN A LIGHT TO MODERATE MOIST ENVIRONMENT AS DEPICTED ON TOTAL PRECIPITABLE WATER IMAGERY. AN UPPER LEVEL LOW CENTERED NEAR 23N79W WHICH EXTENDS A TROUGH ACROSS THE WESTERN CARIBBEAN SUPPORTS LOW VALUES OF DEEP LAYER ENVIRONMENTAL WIND SHEAR...THUS ENHANCING SCATTERED MODERATE CONVECTION AND TSTMS OVER CUBA AND ADJACENT WATERS N OF 17N W OF 77W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM THE WEST AFRICAN COAST NEAR 14N17W TO 09N30W 07N40W. THE INTERTROPICAL CONVERGENCE ZONE AXIS STARTS NEAR 07N40W AND CONTINUES ALONG 07N47W TO 08N55W...THEN RESUMES W OF A SURFACE TROUGH NEAR 08N58W TO 07N61W. A CLUSTER OF MODERATE CONVECTION IS FROM 06N-12N E OF 18W. SCATTERED MODERATE CONVECTION IS FROM 05N-09N BETWEEN 23W-35W. ...DISCUSSION... GULF OF MEXICO... AS OF 0300 UTC...SURFACE TROUGHINESS AND ABUNDANT MOISTURE DOMINATES ACROSS THE BASIN ASSOCIATED WITH A SURFACE TROUGH WITH AXIS EXTENDING FROM 28N88W TO 17N90W. STRONG NORTHEASTERLY FLOW AROUND AN UPPER LEVEL RIDGE CENTERED OVER THE SE CONUS AND EXTENDING INTO THE GULF IS LIMITING CONVECTIVE ACTIVITY ASSOCIATED WITH THE TROUGH TO ISOLATED RAINSHOWERS WITHIN 30 NM EITHER SIDE OF ITS AXIS. OTHERWISE...FAIR WEATHER IS W OF 94W AND E OF 88W FAVORED BY DRY AIR SUBSIDENCE AND HIGH VALUES OF DEEP LAYER ENVIRONMENTAL WIND SHEAR...RESPECTIVELY. THE SURFACE TROUGH WILL CONTINUE TO DRIFT W-NW AND ENTER SOUTHERN TEXAS AND NE MEXICO SATURDAY MORNING. RAINSHOWERS ARE LIKELY OVER THE WESTERN GULF DURING THIS PERIOD. CARIBBEAN SEA... A TROPICAL WAVE IS OVER THE WESTERN CARIBBEAN WITH AXIS EXTENDING FROM 23N79W TO 09N79W. AN UPPER LEVEL LOW CENTERED NEAR 23N79W WHICH EXTENDS A TROUGH ACROSS THE WESTERN CARIBBEAN SUPPORTS LOW VALUES OF DEEP LAYER ENVIRONMENTAL WIND SHEAR...THUS ENHANCING SCATTERED MODERATE CONVECTION AND TSTMS OVER CUBA AND ADJACENT WATERS N OF 17N W OF 77W. SCATTERED MODERATE CONVECTION IS ACROSS THE WINDWARD PASSAGE AND HAITI BEING SUPPORTED BY UPPER LEVEL DIFFLUENCE FROM THE UPPER LOW CENTERED N OF CUBA AND A RIDGE WITH A CENTER OVER SOUTHERN- CENTRAL CARIBBEAN. SIMILAR CONVECTION IS IN THE SOUTHERN BASIN S OF 11N...HOWEVER ASSOCIATED WITH THE MONSOON TROUGH AXIS WHICH MOVES ACROSS COSTA RICA AND PANAMA TO A LOW CENTER OVER NORTHERN COLOMBIA. A SURFACE TROUGH AXIS EXTENDS FROM 16N68W TO 11N68W WITH NO CONVECTION ASSOCIATED WITH IT. THE WAVE WILL CONTINUE TO MOVE WESTWARD AND IS EXPECTED TO BE ALONG HONDURAS AND NICARAGUA BY SATURDAY MORNING. THE TRAILING SURFACE TROUGH IS EXPECTED TO DISSIPATE FRIDAY AFTERNOON...HOWEVER ANOTHER SURFACE TROUGH IS EXPECTED TO MOVE ACROSS THE LESSER ANTILLES FRIDAY MORNING INCREASING THE CHANCES OF PRECIPITATION FOR THIS PART OF THE BASIN. HISPANIOLA... SCATTERED MODERATE CONVECTION IS ACROSS THE WINDWARD PASSAGE AND HAITI BEING SUPPORTED BY UPPER LEVEL DIFFLUENCE FROM AN UPPER LOW CENTERED N OF CUBA AND A RIDGE WITH A CENTER OVER SOUTHERN- CENTRAL CARIBBEAN. RAINSHOWERS ARE EXPECTED TO CONTINUE TO AFFECT AT LEAST HAITI THROUGH FRIDAY MORNING...HOWEVER MORE CONVECTION WILL BUILD IN THE AFTERNOON/EARLY EVENING HOURS ASSOCIATED WITH DAYTIME HEATING. WEATHER CONDITIONS ARE EXPECTED TO IMPROVE EARLY ON SATURDAY DUE TO THE WESTWARD TRANSIT OF A DRY AIRMASS. ATLANTIC OCEAN... AN UPPER LEVEL LOW CENTERED NEAR 23N79W WHICH EXTENDS A TROUGH ACROSS THE WESTERN CARIBBEAN SUPPORTS LOW VALUES OF DEEP LAYER ENVIRONMENTAL WIND SHEAR...THUS ENHANCING SCATTERED MODERATE CONVECTION AND TSTMS OVER CUBA...THE STRAITS OF FLORIDA AND THE BAHAMAS S OF 26N W OF 74W. SIMILAR CONVECTION IS FROM 29N-30N BETWEEN 60W-63W ASSOCIATED WITH A SURFACE TROUGH N OF 30N. MIDDLE LEVEL TROUGHINESS IS SUPPORTING ISOLATED SHOWERS ACROSS THE VIRGIN AND LEEWARD ISLANDS. ANOTHER SURFACE TROUGH EXTENDS FROM 14N56W TO 09N56W WITH SCATTERED RAINSHOWERS WITHIN 30 NM E OF ITS AXIS FROM 10N-11N. OTHERWISE...BESIDES THE TROPICAL WAVE ALREADY DISCUSSED...SURFACE RIDGING AND FAIR WEATHER SUPPORTED BY LOWER-MIDDLE LEVELS DRY AIR DOMINATE THE REMAINDER BASIN. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ RAMOS