000 AXNT20 KNHC 201747 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE OCT 20 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM THE AFRICAN COAST NEAR 13N17W SW 09N21W...THEN W TO 09N29W TO A 1011 MB LOW NEAR 10N33W TO ANOTHER 1011 MB LOW NEAR 10N40W AND TO 10N44W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 150 NM SE OF THE TROUGH BETWEEN 17W-18W...AND WITHIN 120 NM S OF THE TROUGH BETWEEN 37W-39W. SCATTERED MODERATE CONVECTION IS WITHIN 30 NM OF THE TROUGH BETWEEN 24W-27W...AND ALSO BETWEEN 33W-34W. ...DISCUSSION... GULF OF MEXICO... THE TAIL END OF THE ATLC WEAKENING STATIONARY FRONT EXTENDS FROM S FLORIDA TO NEAR 25N85W. SCATTERED SHOWERS AND POSSIBLE ISOLATED WEAK THUNDERSTORMS MOVING QUICKLY WESTWARD ARE S OF THE FRONT. A SURFACE TROUGH IS OVER THE WESTERN GULF ALONG 92W/93W FROM 20N-25N AS OF 15 UTC. THE PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE EASTERN GULF AND BROAD LOW PRESSURE ASSOCIATED WITH THIS TROUGH WILL MAINTAIN STRONG EASTERLY WINDS ACROSS THE E CENTRAL GULF WATERS THROUGH TONIGHT. THIS GRADIENT IS FORECAST TO WEAKEN ON WED. GENTLE TO MODERATE E-SE FLOW WILL PREVAIL OVER THE NW GULF. CARIBBEAN SEA... UPPER-LEVEL RIDGING EXTENDS OVER CENTRAL AMERICA IS COVERING THE WESTERN HALF OF THE BASIN WHILE AN ELONGATED UPPER-LEVEL TROUGH EXTENDS NEWD ACROSS THE TROPICAL ATLANTIC. AT THE SURFACE...A SURFACE TROUGH IS ANALYZED FROM JUST INLAND THE NE YUCATAN PENINSULA TO ALONG THE COAST OF BELIZE AND TO INLAND THE NW PART OF HONDURAS. SCATTERED MODERATE CONVECTION IS OBSERVED JUST W OF THE TROUGH...AND FROM 14N-20N BETWEEN 82W AND THE TROUGH DUE TO UPPER DIFFLUENT FLOW ALOFT AND LOW-LEVEL CONVERGING MOISTURE WITHIN THE MODERATE TO FRESH TRADES OVER THAT PART OF THE SEA. OTHER DIFFLUENT FLOW ALOFT IS ALSO NOTED OVER MUCH OF CUBA AND HISPANIOLA SUPPORTING ISOLATED MODERATE CONVECTION ACROSS SOME SECTIONS OF CUBA....AND OTHER CONVECTION AS DESCRIBED BELOW UNDER HISPANIOLA SECTION. DRY AIR AND SUBSIDENCE PERSISTS ACROSS THE CENTRAL AND EASTER CARIBBEAN INHIBITING CONVECTION EXCEPT DIURNAL ACTIVITY OVER THE GREATER ANTILLES. GENERALLY MODERATE TRADE WINDS COVER THE CENTRAL AND EASTERN CARIBBEAN. CONVECTION WILL CONTINUE OVER THE NW CARIBBEAN OVER THE NEXT 24 TO AT LEAST 36 HOURS. ...HISPANIOLA... A DIFFLUENT PATTERN ALOFT JUST N OF THE ISLAND ALONG THE BASE OF AN ATLC MID/UPPER TROUGH CONTINUES TO PROVIDE UPPER VENTILATION FOR SCATTERED MODERATE/ISOLATED STRONG CONVECTION THAT IS JUST N AND INLAND THE N CENTRAL COAST OF THE ISLAND. ISOLATED SHOWERS AND THUNDERSTORMS ARE DEVELOPING JUST OFFSHORE THE REST OF THE ISLANDS. LATEST SURFACE OBSERVATIONS FROM MDPP ARE REPORTING CUMULONIMBUS TYPE CLOUDS WITH POSSIBLE DEVELOPING TSTMS AT ALL QUADRANTS. THESE CLOUDS AND ACTIVITY ARE EXPECTED TO FURTHER INTENSIFY THROUGHOUT THE AFTERNOON AS DAYTIME HEATING GETS UNDERWAY. CIRRUS OUTFLOW FROM THE SCATTERED MODERATE/ISOLATED STRONG CONVECTION MAY INHIBIT CONVECTION FROM DEVELOPING SOME OVER PORTIONS OF THE HAITI/DOMINICAN REPUBLIC BORDER. EXPECT AN INCREASE IN CONVECTION THROUGH THE NEXT 48 HOURS AS THE ATLC TROUGH AMPLIFIES...AND THE FAVORABLE DIFFLUENT PATTERN BECOMES MORE PRONOUNCED WHILE AT THE SAME TIME GFS PRECIPITABLE POTENTIAL GUIDANCE DEPICTS INCREASING MOISTURE VALUES FOR THE ISLAND. ATLANTIC OCEAN... A BROAD MID/UPPER-LEVEL TROUGH SLIDING EASTWARD ACROSS THE NW ATLANTIC CONTINUES TO SUPPORT TO A FRONTAL SYSTEM THAT BEGINS AS A WEAKENING STATIONARY FRONT THAT EXTENDS FROM S FLORIDA TO 25N74W TO 25N62W WHERE IT THEN TRANSITIONS INTO A COLD FRONT THAT CONTINUES NE TO 26N60W AND TO NE OF THE AREA AT 32N49W. A PRE-FRONTAL TROUGH IS SE OF THE COLD FRONT ALONG A POSITION FROM 30N51W TO 25N60W...AND CONTINUES SW TO NEAR 21N69W. ASCAT DATA FROM 1310 UTC THIS MORNING SHOWED A SHARP S TO NE WIND SHIFT ACROSS THE TROUGH. UPPER LEVEL DYNAMIC LIFT PROVIDED BY THE MID/UPPER TROUGH COMBINING WITH PLENTIFUL MOISTURE BETWEEN THE FRONT AND PRE-FRONTAL TROUGH IS RESULTING IN CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 21N-24N BETWEEN 63W-69W...AND FROM 24N-28N BETWEEN 54W-63W. OTHER SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS NEAR THE BASE OF THE MID/UPPER TROUGH FROM 20N-23N BETWEEN 71W-74W...AND BETWEEN THE CENTRAL BAHAMAS AND THE N CENTRAL COAST OF CUBA. THE COLD FRONT PORTION OF FRONTAL BOUNDARY WILL CONTINUE SE TONIGHT STALLING FROM 26N65W TO THE WINDWARD PASSAGE ON WED AND THU. A WEAK LOW WILL DEVELOP ALONG THE FRONT NEAR 23N69W ON THU NIGHT AND RACE NE DRAGGING THE FRONT E AGAIN ON FRI. THE FRONT WILL BECOME STATIONARY OVER THE FAR SE WATERS N OF PUERTO RICA ON SAT...THEN DRIFT W ON SUN. A MORE STABLE UPPER LEVEL ENVIRONMENT W OF THE MID/UPPER TROUGH IS ALLOWING FOR MAINLY SCATTERED TO NUMEROUS SHOWERS TO EXIST ALONG AND NEAR THE STATIONARY FRONTAL BOUNDARY. THESE SHOWERS ARE MOVING WESTWARD RATHER QUICKLY...AND ARE CAPABLE OF PRODUCING GUSTY WINDS. OVER THE TROPICAL ATLC PORTION...A SURFACE TROUGH IS ROUGHLY ALONG A POSITION FROM NEAR 15N53W TO 12N55W TO 09N55W. THIS FEATURE IS INTERACTING WITH AN UPPER-LEVEL TROUGH THAT EXTENDS FROM THE WINDWARD ISLANDS NE TO NEAR 20N53W. A DIFFLUENT FLOW ALOFT E OF THE UPPER TROUGH IS SUPPORTING ISOLATED CONVECTION E OF THIS SURFACE TROUGH FROM 11N-18N BETWEEN 43W-53W. HOWEVER ...THIS CONVECTION IS SHORT-LIVED AS UPPER LEVEL SW WINDS ARE SHEARING OFF THE CLOUDS TOPS OFF TO THE E. OVER THE FAR EASTERN ATLC...A DISSIPATING COLD FRONT EXTENDS FROM OVER THE FAR EASTERN ATLC...A COLD FRONT FROM OVER NW AFRICA EXTENDS SW TO 23N17W AND TO 23N22W. ISOLATED SHOWERS ARE POSSIBLE ALONG THE FRONT MAINLY BETWEEN 19W-22W. NEAR GALE FORCE WINDS ARE POSSIBLE N OF 32N E OF 15W DUE TO A STRONG PRESSURE GRADIENT BEHIND THIS COLD FRONT. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ AGUIRRE