000 AXNT20 KNHC 121048 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT SAT SEP 12 2015 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. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 09N27W TO 17N24W MOVING W AT 10-15 KT. THE WAVE COINCIDES WITH LOW AMPLITUDE 700 MB TROUGHING S OF 14N BETWEEN 21W-30W. WITH THE SAHARAN AIR LAYER AND DUST LARGELY INFLUENCING THE NORTHERN PORTION OF THE WAVE AND MUCH OF THE EASTERN TROPICAL ATLC...ISOLATED MODERATE CONVECTION REMAINS CONFINED TO THE MONSOON TROUGH REGION IN THE VICINITY OF THE WAVE AXIS FROM 07N-11N BETWEEN 22W-29W. TROPICAL WAVE EXTENDS FROM 09N46W TO 16N45W MOVING W AT 15-20 KT. THE WAVE COINCIDES WITH A BROAD 700 MB TROUGHING BETWEEN 42W- 49W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 08N-14N BETWEEN 42W-49W. TROPICAL WAVE EXTENDS FROM 13N65W TO 20N65W MOVING W AT 15 KT. THE WAVE COINCIDES WITH A 700 MB TROUGHING BETWEEN 62W-69W AND A 850 MB RELATIVE VORTICITY MAXIMUM NEAR 17N66W. SCATTERED MODERATE CONVECTION IS FROM 14N-19N BETWEEN 63W-69W. TROPICAL WAVE EXTENDS FROM 06N80W TO 15N80W MOVING W AT 15-20 KT. THE WAVE COINCIDES WITH SUBTLE 700 MB TROUGHING OVER THE WESTERN CARIBBEAN SEA. ISOLATED MODERATE CONVECTION IS FROM 11N- 13N BETWEEN 74W-79W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 18N16W TO 10N25W TO 07N34W TO 10N42W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 10N42W TO 10N46W TO 09N54W. SCATTERED MODERATE CONVECTION IS FROM 15N-18N BETWEEN 15W-21W AND FROM 05N-10N BETWEEN 30W-38W. ISOLATED MODERATE CONVECTION IS FROM 08N-14N BETWEEN 40W-58W. ...DISCUSSION... GULF OF MEXICO... BROAD MIDDLE TO UPPER LEVEL LONGWAVE TROUGHING IS NOTED ON WATER VAPOR COVERING MUCH OF THE CENTRAL AND EASTERN CONUS WITH THE BASE OF THE TROUGH DIPPING OVER THE NW AND NORTH-CENTRAL GULF WATERS THIS MORNING. PLENTIFUL MID-LEVEL ENERGY IS N OF 25N AND ALONG WITH THE UPPER LEVEL DIFFLUENCE AHEAD OF THE TROUGH AXIS...THESE FEATURES CONTINUE TO GENERATE SCATTERED SHOWERS AND TSTMS FROM 21N-28N BETWEEN 91W-100W...INCLUDING INLAND PORTIONS OF NE MEXICO FOCUSED ALONG A SURFACE TROUGH BOUNDARY EXTENDING FROM 28N90W TO 25N98W. IN ADDITION...SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING E OF 87W. WHILE THE MIDDLE TO UPPER LEVEL FEATURES ARE THE PRIMARY SUPPORT OF THE ACTIVE CONVECTION...WEAK SURFACE RIDGING EXTENDS ACROSS THE FLORIDA STRAITS TO THE SOUTH-CENTRAL GULF NEAR 23N90W PROVIDING GENTLE ANTICYCLONIC BREEZE CONDITIONS OUTSIDE OF THE ACTIVE CONVECTION. THE WEAK FRONTAL BOUNDARY SUPPORTED BY THE UPPER LEVEL TROUGHING IS EXPECTED TO SWEEP ACROSS THE NORTHERN GULF WATERS SATURDAY INTO EARLY SUNDAY AND MOVE EAST OF THE BASIN BY MONDAY. CARIBBEAN SEA... MIDDLE TO UPPER LEVEL RIDGING IS OVER MUCH OF THE WESTERN CARIBBEAN ANCHORED NEAR 16N86W PRODUCING OVERALL DRY AND STABLE CONDITIONS ALOFT...HOWEVER THE PRESENCE OF A TROPICAL WAVE ALONG 80W IS PROVIDING FOCUS FOR ISOLATED SHOWERS AND TSTMS IN THE VICINITY OF 12N77W. FARTHER EAST...AN UPPER LEVEL TROUGH INFLUENCES THE EASTERN CARIBBEAN BETWEEN 62W-74W. GIVEN THE TROPICAL WAVE ALONG 65W...THE REMNANTS OF GRACE...AND THE FAVORABLE UPPER LEVEL DIFFLUENT ENVIRONMENT EAST OF THE TROUGH AXIS...SCATTERED SHOWERS AND TSTMS ARE OCCURRING ACROSS THE EASTERN CARIBBEAN THIS MORNING. THE WAVE IS EXPECTED TO CONTINUE MOVING WESTWARD AND BRING INCREASED PROBABILITIES OF PRECIPITATION TO PUERTO RICO...THE MONA PASSAGE...AND HISPANIOLA ON SATURDAY. OTHERWISE...MODERATE TO FRESH TRADES PREVAIL AND ARE EXPECTED TO INCREASE SLIGHTLY ACROSS THE CENTRAL CARIBBEAN WITH THE APPROACHING TROPICAL WAVE ON SUNDAY. ...HISPANIOLA... CURRENTLY MOSTLY CLEAR SKIES AND FAIR CONDITIONS PREVAIL... HOWEVER THE PRESENCE OF A TROPICAL WAVE ALONG 65W WILL BRING AN INCREASE IN CLOUDINESS AND PROBABILITY OF PRECIPITATION AND STRONG CONVECTION ON SATURDAY. SOME OF THE RAINFALL WILL BE HEAVY AT TIMES AND LIKELY RESULT IN FLASH FLOODING AND MUD SLIDES IN THOSE AREAS PRONE TO THESE HAZARDS. ATLANTIC OCEAN... MOST OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF SURFACE RIDGING WITH AXIS EXTENDING FROM A 1020 MB HIGH CENTERED NEAR 29N55W W-SW TO THE CENTRAL BAHAMAS NEAR 24N77W. WITH OVERALL WEST-SOUTHWESTERLY FLOW ALOFT N OF 30N...AND A WEAKNESS IN THE SURFACE RIDGING BETWEEN 75W-83W...SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING N OF 28N BETWEEN 72W-80W. OTHERWISE...THE ONLY OTHER MAJOR FEATURE IMPACTING THE SW NORTH ATLC IS THE REMNANTS OF GRACE...ANALYZED AS A TROPICAL WAVE ALONG 65W. MOST OF THE CONVECTION REMAINS S OF 20N...AND IS EXPECTED TO CONTINUE WESTWARD ACROSS THE ADJACENT COASTAL ATLC WATERS OF PUERTO RICO AND HISPANIOLA ON SATURDAY. FARTHER EAST...AN ELONGATED UPPER LEVEL LOW IS CENTERED NEAR 28N48W AND IS SUPPORTING TWO AREAS OF CONVECTION ACROSS THE CENTRAL ATLC THIS MORNING. SCATTERED SHOWERS AND TSTMS ARE NOTED FROM 23N-29N BETWEEN 48W-56W ON THE WESTERN PERIPHERY OF THE UPPER LEVEL LOW AND ISOLATED SHOWERS AND TSTMS ARE NOTED FROM 27N-32N BETWEEN 38W-43W IN ASSOCIATION WITH A WEAK 1017 MB LOW CENTERED NEAR 28N40W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN