000 AXNT20 KNHC 161800 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SAT MAY 16 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 1745 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 10N14W TO 06N19W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 06N19W TO 05N32W TO THE COAST OF S AMERICA NEAR 03N51W. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 180 NM S OF THE MONSOON AND ITCZ 15W-21W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM N OF THE MONSOON TROUGH AND ITCZ BETWEEN 17W-21W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N OF THE ITCZ BETWEEN 50W-51W...AND ALSO N OF THE ITCZ WITHIN 30 NM OF LINE FROM 35W-37W. ...DISCUSSION... GULF OF MEXICO... BOTH MODEL GUIDANCE AND WATER VAPOR IMAGERY SHOW AN UPPER TROUGH OVER FAR EASTERN TEXAS APPROACHING THE BORDER OF LOUISIANA...AND EXTENDING S TO NEAR 24N92W. AHEAD AND SE OF THIS TROUGH... MOISTURE IN THE FORM OF MID/UPPER LEVEL CLOUDS IS PRESENT. AT THE SURFACE...A RIDGE EXTENDS SW FROM THE FLORIDA BIG BEND AREA TO THE NE COAST OF MEXICO. LOW-LEVEL MOIST SE FLOW AROUND THE WESTERN PERIPHERY IS ALLOWING FOR SCATTERED TO LOCALLY BROKEN LOW CLOUDS WITH ISOLATED SHOWERS TO MOVE IN A NW DIRECTION E OF ABOUT 91W. THE RIDGE IS ALLOWING FOR GENERALLY GENTLE TO MODERATE SW WINDS TO CONTINUE OVER THE AREA. THE UPPER TROUGH IS FORECAST TO SHIFT EASTWARD TO THE EASTERN GULF BY MON...WITH ASSOCIATED UPPER DIFFLUENCE EXPECTED TO MORE NOTICEABLE THERE. WITH THIS IN MIND...EXPECT ISOLATED SHOWERS AND TSTMS OVER THAT PART OF THE GULF WITH SCATTERED SHOWERS AND TSTMS EXPECTED TO DEVELOP CLOSER THE NE GULF COAST SUN AND MON MAINLY FROM INFLUENCES RELATED TO SURFACE BOUNDARIES THERE. THE GENTLE TO MODERATE SE WINDS WILL CONTINUE THROUGH MON UNDER THE INFLUENCE OF THE RIDGE...WITH THE EXCEPTION OF THE NW COAST OF THE YUCATAN PENINSULA WHERE A TIGHT PRES GRADIENT WILL MATERIALIZE THERE AT NIGHT RESULTING IN STRONG E-SE WINDS THAT SHIFT FROM THAT WESTWARD ACROSS THE EASTERN PART IF THE SW GULF THAT THE LATE NIGHT HOURS. CARIBBEAN SEA... A WEAK AND SMALL UPPER LOW IS NOTED OVER THE FAR WESTERN TIP OF CUBA WITH A TROUGH EXTENDING S TO NE HONDURAS. UPPER-LEVEL SW FLOW E OF THE TROUGH CONTINUES TO ADVECT DEEP ATMOSPHERIC MOISTURE...THAT ORIGINATES FROM THE EASTERN PACIFIC...ACROSS JUST ABOUT THE ENTIRE BASIN. SATELLITE IMAGERY SHOWS CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION CONFINED TO THE SW CARIBBEAN S OF ABOUT 12N AND W OF 78W TO INLAND PORTIONS OF COSTA RICA AND PANAMA. DEBRIS UPPER LEVEL CLOUDS...IN THE FORM OF BROKEN CIRRUS...IS BEING ADVECTED IN THE SW FLOW ALOFT NEWD TOWARDS JAMAICA...HISPANIOLA...AND EASTWARD TO PUERTO RICO...AND THE LEEWARD ISLANDS. THE SURFACE HIGH CENTERED OVER THE W ATLANTIC THAT EXTENDS SW ACROSS THE GULF ALSO REACHES THE WESTERN CARIBBEAN. THE ASSOCIATED PRES GRADIENT BETWEEN IT AND BROAD LOW PRES OVER THE SW CARIBBEAN AND NW COLOMBIA IS ALLOWING FOR FRESH TO STRONG TRADES TO PERSIST OVER THE S CENTRAL CARIBBEAN AS SEEN IN THE ASCAT PASS FROM THIS MORNING. MODERATE TO FRESH TRADES ARE ELSEWHERE S OF 17N...AND MODERATE TRADES N OF 17N EXCEPT FOR GENTLE TO MODERATE TRADES OVER THE NW CARIBBEAN. THE FRESH TO STRONG TRADES OVER THE S CENTRAL CARIBBEAN ARE FORECAST TO CONTINUE THROUGH SUN NIGHT. CURRENT AND LATEST NWS DOPPLER RADAR IMAGERY FROM SAN JUAN PUERTO RICO INDICATES LIGHT TO MODERATE SHOWERS MOVING QUICKLY WESTWARD N OF 17N E OF 69W. SIMILAR ACTIVITY IS INFERRED ON SATELLITE IMAGERY TO BE OCCURRING ACROSS THE REMAINDER OF THE SEA...EXCEPT TO THE N OF 12N E OF 73W. ISOLATED TSTMS ARE POSSIBLE S OF 15N BETWEEN 73W AND 78W. SHOWER AND TSTM ACTIVITY IS EXPECTED TO BECOME ACTIVE IN COVERAGE OVER THE ISLANDS IN THE AFTERNOON DUE TO OROGRAPHIC LIFTING AND DAYTIME HEATING. LATEST MOISTURE GUIDANCE FROM THE GFS SHOWS AN INCREASE IN LOW-LEVEL MOISTURE ACROSS THE EASTERN PART OF THE CARIBBEAN OVER THE NEXT 24-48 HRS WITH PRECIPITABLE WATER VALUES IN THE 1.25 TO 1.75 INCH RANGE OVER THAT PORTION OF THE SEA MOST PROBABLE LEADING TO MORE CONCENTRATED PATCHES OF CONVECTION THERE. ...HISPANIOLA... LOW CLOUDS ARE BEGINNING TO DEVELOP OVER THE INTERIOR PORTIONS OF THE ISLAND...WITH THE MOST CONCENTRATION OVER THE S CENTRAL PART OF THE DOMINICAN REPUBLIC. THE UPPER LEVEL DEBRIS CLOUDINESS DESCRIBED UNDER CARIBBEAN SEA ARE MOVING ACROSS THE ISLAND...BUT VISIBLE IMAGERY INDICATES THAT THEY ARE RATHER THIN. EXPECT DAYTIME HEATING AND OROGRAPHIC LIFTING ALONG WITH SUPPORT OF A NEARBY UPPER JET FOUND TO THE E OF THE CARIBBEAN UPPER TROUGH MENTIONED ABOVE TO ENHANCE SHOWER ACTIVITY EVERY AFTERNOON AND INTO THE EVENING HOURS THROUGH THE NEXT 48 HRS. ATLANTIC OCEAN... UPPER LEVELS...A TROUGH STRETCHES FROM NEAR 32N55W SW TO 24N67W...AND WEAKENS AS IT CONTINUES SW TO THE UPPER LOW OVER THE WESTERN TIP OF CUBA. A SHARPER UPPER TROUGH EXTENDS FROM A WELL DEFINED LOW LOCATED N OF THE AREA NEAR 35N54W SSW TO NEAR 26N53W. WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG SUBSIDENCE S OF 26N BETWEEN 51W AND 68W...AND ALSO FROM 16N TO 24N BETWEEN 41W AND 51W. A THE SURFACE...A COLD FRONT ASSOCIATED WITH THE LOW N OF THE AREA AND THE SHARP UPPER TROUGH ENTERS THE AREA THROUGH 32N49W...AND CONTINUES SW TO 26N55W TO 24N59W WHERE IT BECOMES A WEAKENING COLD FRONT TO 24N63W...AND WEAKENING STATIONARY TO 24N68W. A PRE-FRONTAL TROUGH EXTEND FROM 25N57W SW TO NEAR 20N64W. ISOLATED SHOWERS AND TSTMS ARE WITHIN 30-60 NM OF THE FRONT AND TROUGH. A SWIRL OF LOW-LEVEL MOISTURE SPUN OFF THE FROM THE WESTERN PART OF THE STATIONARY IS IDENTIFIED TO BE NEAR 25N70W. THE ASCAT PASS FROM THIS MORNING SHOWED AN ENHANCED GRADIENT SUPPORTING NE 15-20 KT WITHIN ABOUT 60 NM TO ITS N. ANOTHER SIMILAR AREA OF LOW-LEVEL MOISTURE MOVING WESTWARD JUST N OF THE NW BAHAMAS FROM 26N-28N. NWS DOPPLER RADAR SHOWS SCATTERED SHOWERS AND ISOLATED TSTMS WITH THIS AREA OF LOW-LEVEL MOISTURE. TPW IMAGERY AND UPPER LEVEL PV DIAGNOSTICS SUGGEST THAT A WEAK TROUGH IS AT THE WESTERN MOST PORTION OF THE ITCZ NEAR 51W. THIS FEATURE IS HELPING TO ENHANCE ITCZ-RELATED CONVECTION AS DESCRIBED ABOVE. THE TROUGH IS FORECAST TO WEAKEN AS IT APPROACHES S AMERICA MON AND MON NIGHT. STRONG HIGH PRES RIDGING EXTENDS FROM A 1028 HIGH N OF THE AREA AT 35N71W SE TO NEAR 25N63W ALLOWING FOR MAINLY SCATTERED LOW CLOUDS AND O PREVAIL W OF THE FRONT. SCATTERED HIGH CLOUDS ARE SEEN THERE AS WELL. THE REMAINDER OF THE BASIN IS UNDER THE INFLUENCE OF RATHER STRONG HIGH PRES. BROKEN HIGH CLOUDS STREAMING NE ARE SEEN WITHIN 60 NM OF A LINE FROM 13N60W TO 16N45W TO 21N36W RELATE TO A SUBTROPICAL JET STREAM BRANCH PRESENT THERE. LITTLE CHANGE IS EXPECTED WITH THIS PATTERN OVER THE NEXT 48 HRS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ AGUIRRE