000 AXNT20 KNHC 161759 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN JUN 16 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1800 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IN THE WESTERN CARIBBEAN EXTENDS FROM 21N81W TO 17N82W TO 12N82W DRIFTING W AT 5 KT. OBSERVATIONS FROM GRAND CAYMAN AND BUOY 42057 INDICATE WINDS ARE SLIGHTLY NE...HINTING THAT THE WAVE AXIS HAS NOT YET PASSED 81W AT THE SURFACE...IN ALMOST THE SAME POSITION AS 06 UTC. IN ADDITION...THE MORNING SOUNDING FROM GRAND CAYMAN INDICATED NE TO E WINDS THROUGH H7. NUMEROUS MODERATE TO SCATTERED STRONG CONVECTION IS NOTED FROM 16N TO 18N BETWEEN 80W AND 86W...AND FROM 12N TO 15N BETWEEN 80W AND 82W. THE TROPICAL WAVE IS INTERACTING WITH AN UPPER CYCLONE CENTERED OVER BELIZE...GUATEMALA AND WESTERN HONDURAS...WHICH IS ENHANCING THE CONVECTION. THE TROPICAL WAVE IS AMPLIFYING AND SLOWLY DOWN...AND IN CONJUNCTION WITH THE UPPER CYCLONE WILL BRING CONTINUED CONVECTION TO THE NW CARIBBEAN...AND HEAVY RAINFALL OVER NORTHERN CENTRAL AMERICA AND SOUTHERN MEXICO OVER THE NEXT COUPLE OF DAYS. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS NORTH AFRICA AND CROSSES THE COAST OF SENEGAL NEAR 14N16W THEN CONTINUES TO 11N20W. THE ITCZ CONTINUES FROM 11N20W TO THE COAST OF FRENCH GUIANA NEAR 04N52W. SCATTERED MODERATE CONVECTION IS NOTED WITHIN 90 NM N OF THE AXIS W OF 38W. ...DISCUSSION... GULF OF MEXICO... A FEW THUNDERSTORMS PERSIST OFF THE SE LOUISIANA AND MISSISSIPPI COASTLINES THIS AFTERNOON...SUPPORTED BY A WEAK UPPER SHORT WAVE TROUGH DIGGING THROUGH THE NE GULF. A STATIONARY FRONT THAT EXTENDED ACROSS CENTRAL FLORIDA INTO THE NE GULF OVERNIGHT HAS SINCE DISSIPATED. THIS HAS LEFT A BROAD SURFACE RIDGE EXTENDING FROM NORTH FLORIDA TO SOUTH TEXAS. SCATTEROMETER AND BUOY DATA SHOW GENERALLY LIGHT TO MODERATE E TO SE FLOW TO THE SOUTH OF THE RIDGE AXIS...EXCEPT FOR SE WINDS 15 TO 20 KT OF THE COAST OF TAMAULIPAS IN NE MEXICO. THE SHORT WAVE TROUGH IS IN PHASE WITH AN ELONGATED UPPER CYCLONE CENTERED S OF THE AREA OVER NORTHER CENTRAL AMERICA. NORTHERLY FLOW ALOFT ON THE WESTERN SIDE OF THIS TROUGH IS KEEPING THE MAJORITY OF THE GULF CLOUD FREE. THE UPPER CYCLONE IS SUPPORTING A TROPICAL WAVE MOVING THROUGH THE NW CARIBBEAN. THE N PORTION OF A TROPICAL WAVE WILL PASS W ACROSS THE YUCATAN BASIN TONIGHT AND MON AND PASS ACROSS THE BAY OF CAMPECHE TUE THROUGH LATE THU NIGHT WITH LOW PRESSURE POSSIBLY DEVELOPING ALONG THE WAVE S OF 20N. THIS WILL INCREASE THE SE FLOW OVER THE SW GULF TUE INTO WED. CARIBBEAN SEA... A MID LEVEL CIRCULATION ASSOCIATED WITH THE TROPICAL WAVE OVER THE WESTERN CARIBBEAN APPEARS TO BE GETTING A LITTLE BETTER ORGANIZED...ALTHOUGH IT ALSO APPEARS TO MOVING OVER THE EASTERN PORTIONS OF HONDURAS AND NE NICARAGUA. JUDGING FROM SURFACE OBSERVATIONS ALONE...THERE DOES NOT YET APPEAR TO BE A WELL DEFINED SURFACE CIRCULATION...JUST AN AREA OF BROAD CYCLONIC TURNING W OF 78W. ELSEWHERE E OF 80W...A FEW SHOWERS MAY BE ACTIVE IN FRESH TRADE WIND FLOW ACROSS THE CARIBBEAN AND TROPICAL N ATLC...BUT SKIES REMAIN MOSTLY CLOUD FREE. MEANWHILE A AREA OF SAHARAN DUST TRACKING ACROSS THE ATLC WILL CONTINUE TO PUSH OVER THE LEEWARD ISLANDS THROUGH PUERTO RICO. WHILE THIS IS LOWERING VISIBILITIES SLIGHTLY...THE MAIN IMPACT COULD BE SLIGHTLY STRONGER WIND GUSTS NEAR THUNDERSTORMS. ASIDE FROM THE WEATHER IN THE NW CARIBBEAN ASSOCIATED WITH THE TROPICAL WAVE DISCUSSED ABOVE...A SIMILAR SCENARIO MAY BE GETTING ORGANIZED THAT WILL IMPACT THE TROPICAL N ATLC AND EASTERN CARIBBEAN OVER THE NEXT TWO TO THREE DAYS. AN UPPER LOW WILL CUT OFF WELL N OF THE ISLANDS AND DRIFT SOUTH. THIS WILL INTERACT WITH A WEAK A COUPLE OF PERTURBATIONS NOW EMBEDDED IN THE ITCZ AND MOVING THROUGH FRENCH GUIANA. THE UPPER CYCLONE WILL ALLOW A TROUGH TO AMPLIFY OVER THE EASTERN CARIBBEAN...DRAWING UP DEEP LAYER MOISTURE ACROSS THE TROPICAL N ATLC...LESSER ANTILLES...AND EASTERN CARIBBEAN MON THROUGH TUE. MEANWHILE THE GRADIENT WILL TIGHTEN BETWEEN THE SUBTROPICAL RIDGE WILL BUILD TO THE N OF THE AREA AND THE TROUGH OVER THE EASTERN CARIBBEAN AND DEVELOPING LOW PRES OVER THE WESTERN CARIBBEAN TO ALLOW FRESH TO STRONG TRADES ACROSS THE ENTIRE BASIN THROUGH MID WEEK. HISPANIOLA... A SHARP UPPER TROUGH EXTENDING FROM BERMUDA TO THE SOUTHERN BAHAMAS IS ENHANCING A LARGE AREA OF CONVECTION OFF THE NORTH COAST OF HISPANIOLA CURRENTLY. OUTFLOW BOUNDARIES FROM THIS CONVECTION ARE NOTED ON VISIBLE SATELLITE IMAGERY AND WILL REINFORCE AFTERNOON SEA BREEZES OVER THE NORTHERN PORTIONS OF THE ISLAND. THE APPROACHING UPPER TROUGH WILL SHIFT THE FAVORABLE UPPER DYNAMICS TO OVER THE ISLAND THROUGH THIS EVENING...RESULTING IN THE POTENTIAL FOR THUNDERSTORMS ACROSS HISPANIOLA INTO THE LATE EVENING BEFORE SHIFTING E OF THE AREA LATE TONIGHT. A LAYER OF SAHARAN DUST INFILTRATING INTO THE EASTERN CARIBBEAN MAY INTERACT WITH THESE THUNDERSTORMS TO PRODUCE STRONG GUSTS. AN UPPER LOW IS EXPECTED TO CUT OFF AT THE BASE OF THE TROUGH THROUGH MON...AND SHIFT TO THE NE OF HISPANIOLA. THIS WILL ALLOW FOR SLIGHTLY DRIER AIR ALOFT AND WITH A TREND FOR LESS FAVORABLE CONDITIONS FOR THUNDERSTORM DEVELOPMENT MON INTO TUE. ATLANTIC OCEAN... A SHARP UPPER TROUGH FROM BERMUDA TO THE SOUTHERN BAHAMAS IS SUPPORTING A LARGE AREA OF SHOWERS AND THUNDERSTORMS S OF 22N BETWEEN 70W AND 73W...ROUGHLY BETWEEN HISPANIOLA AND THE SOUTHERN BAHAMAS/TCI. IS SHOWING SIGNS OF CUTTING OFF INTO AN UPPER CYCLONE N OF PUERTO RICO THROUGH MON. THE CONVECTION WILL PERSIST AHEAD OF THE TROUGH AS IT SHIFTS TO THE SE AND E THROUGH TONIGHT. THE UPPER TROUGH IS SUPPORTING THE MOVEMENT OF A WEAK COLD FRONT ACROSS THE SW N ATLC...EXTENDING FROM 31N58W TO 26N70W. THIS FEATURE WILL CONTINUE WEAKEN AND SLOW AS IT DRIFTS E...EVENTUALLY DISSIPATING BY LATE MON/EARLY TUE. THE PRESENTATION OF THE UPPER TROUGH ON SATELLITE IMAGERY SUPPORTS MODEL OUTPUT SHOWING THE TROUGH CUTTING OFF AN UPPER LOW N OF PUERTO RICO AND THE USVI ALONG ROUGHLY 65W THROUGH MON. THIS WILL SUPPORT DEVELOPMENT OF A TROUGH OVER THE EASTERN CARIBBEAN EARLY IN THE WEEK. FRESH TO STRONG TRADE WINDS WILL PERSIST OVER THE WATERS S OF 25N BETWEEN THE TROUGH IN THE CARIBBEAN AND A REINFORCED SUBTROPICAL RIDGE N OF THE AREA. WEAK LOW AMPLITUDE PERTURBATIONS ARE NOTED DEEP IN THE TROPICS ALONG THE ITCZ W OF 45W. ONE OF THESE PRESENTS WELL ON A 1325 UTC ASCAT PASS...AND ALIGNS WELL WITH THE 12 UTC SOUNDING FROM CAYENNE FRENCH GUIANA. THIS WEAK TROUGH/TROPICAL WAVE WILL START TO AMPLIFY WITH THE UPPER LOW FORMING ALONG 65W...EVENTUALLY FORMING THE AFOREMENTIONED TROUGH OVER THE EASTERN CARIBBEAN. FARTHER EAST...BROAD 1029 MB SURFACE HIGH PRES CENTERED NEAR 35N39W DOMINATES THE CENTRAL TROPICAL ATLC...SUPPORTING A MODERATE TO FRESH TRADE WINDS S OF 20N CONVERGING INTO THE ITCZ W OF 35W. OFF THE COAST OF SENEGAL...THERE IS SOME INDICATION OF A NORTHERN VORTEX THAT SHIFTED OFF THE COAST PREVIOUSLY...BUT LITTLE CLEAR INDICATION OF AN ORGANIZED TROPICAL WAVE AT THIS TIME IN PART DUE TO FAIRLY DRY CONDITIONS AND LACK OF SENSIBLE WEATHER IN THE AREA. WILL MONITOR THIS FOR POSSIBLE TROPICAL WAVE OVER THE NEXT COUPLE OF DAYS OVER THE FAR EASTERN ATLC. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ CHRISTENSEN