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AXNT20 KNHC 302340
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT APR 30 2016

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC.


...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS INTO THE EASTERN TROPICAL ATLC NEAR 09N13W...AND CONTINUES TO 05N18W...WHERE SCATTEROMETER AND MODEL GUIDANCE SUGGEST THAT THE ITCZ AXIS BEGINS AND CONTINUES TO 03N30W TO 04N40W TO INLAND S AMERICA AT 04N52W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 180 NM S OF THE AXIS BETWEEN 20W-24W. SCATTERED MODERATE CONVECTION IS WITHIN 180 NM N OF THE AXIS BETWEEN 49W-54W.


...DISCUSSION...

GULF OF MEXICO...

THE WESTERN EXTENSION OF RATHER ATLC HIGH PRES EXTENDS WESTWARD TO OVER THE EASTERN PORTION OF THE GULF. BROAD LOW PRES IS ELSEWHERE ACROSS THE GULF WITH AN ASSOCIATED 1002 MB LOW CENTERED IN THE SW GULF JUST NE OF TAMPICO NEAR 22N97W WITH A TROUGH EXTENDING NNE TO 26N96W TO 28N94W TO SW LOUISIANA WHERE AN OUTFLOW BOUNDARY THEN EXTENDS N TO OVER SW LOUISIANA. AN UPPER TROUGH OVER EASTERN TEXAS IS SUPPORTING THE SURFACE TROUGH THAT EXTENDS FROM THE 1002 MB LOW. SCATTERED MODERATE/ ISOLATED STRONG CONVECTION IS NOTED ON BOTH NWS MOSAIC RADAR ON SATELLITE IMAGERY MOVING EASTWARD ALONG AND JUST OFFSHORE THE COASTS OF LOUISIANA...SPREADING EASTWARD TO THE FAR WESTERN FLORIDA PANHANDLE. THIS ACTIVITY IS BEING FURTHER SUPPORTED BY AN UPPER SHORTWAVE TROUGH SWINGING EASTWARD ACROSS EASTERN LOUISIANA AND WESTERN MISSISSIPPI. SIMILAR CONVECTION IS OVER THE WESTERN BAY OF CAMPECHE WITHIN 30 NM OF A LINE FROM THE VERACRUZ AREA E TO NEAR 20N94W. THIS ACTIVITY IS BEING AIDED BY AN UPPER LEVEL DISTURBANCE RIDING EASTWARD ACROSS THE CREST OF UPPER LEVEL RIDGING LOCATED OVER THE WESTERN PART OF THE GULF S OF 25N. THE AFOREMENTIONED CONVECTION FROM SE LOUISIANA TO THE WESTERN FLORIDA PANHANDLE WILL CONTINUE TO SHIFT EASTWARD INTO EARLY SUN. THE CONVECTION IN THE SW GULF WILL ALSO CONTINUE TO TRANSLATE EASTWARD THROUGH SUN. THE PRES GRADIENT BETWEEN THE HIGH PRES OVER THE EASTERN GULF AND LOWER PRES OVER THE WESTERN GULF IS ENOUGH TO SUPPORT MODERATE SE WINDS OVER THE EASTERN GULF...AND FRESH TO LOCALLY STRONG SE WINDS OVER THE MAJORITY OF THE CENTRAL AND WESTERN GULF. A WEAK COLD FRONT IS FORECAST MOVE ACROSS THE NW GULF LATE ON MON.

CARIBBEAN SEA...

A BROAD UPPER TROUGH OVER THE SW N ATLC CONTINUES TO INTERACT WITH A MOIST AND UNSTABLE AIRMASS PRESENT OVER THE BASIN SETTING OFF CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION N OF 15N BETWEEN 62W-71W...INCLUDING MOST OF PUERTO RICO AND THE VIRGIN ISLANDS. THIS UNSETTLED WEATHER PATTERN IS FORECAST TO REMAIN IN PLACE THROUGH THE NEXT 24-48 HOURS AS THE TROUGH SLOWLY MOVES EASTWARD...AND WHILE AT THE SAME UPPER SHORTWAVE ENERGY PASS OVER THE EASTERN CARIBBEAN SEA. SCATTERED MODERATE CONVECTION OVER MUCH OF COSTA RICA AND PANAMA DEVELOPED WITH DAYTIME HEATING...AND WITH THE ADDED INGREDIENT OF THE WELL PRONOUNCED SEABREEZE FRONT NOTED IN THE 18 UTC SURFACE ANALYSIS. THIS ACTIVITY IS EXPECTED TO DIMINISH TONIGHT...THEN REDEVELOP ON SUN. ISOLATED SHOWERS AND TSTMS ARE SEEN N OF 15N W OF 71W. BOTH BUOY AND EARLIER SCATTEROMETER DATA SHOW MODERATE TRADE WIND FLOW THROUGHOUT...EXCEPT FOR MODERATE TO FRESH TRADES N OF HONDURAS TO 18N. THESE WINDS ARE FORECAST TO CONTINUE INTO MON.

HISPANIOLA...

AN UPPER LOW EMBEDDED WITHIN THE UPPER TROUGH DESCRIBED ABOVE UNDER CARIBBEAN SECTION IS CENTERED ROUGHLY ABOUT 150 NM NE OF HISPANIOLA. THE TAIL END OF THE UPPER TROUGH EXTENDS SW ACROSS HISPANIOLA TO NEAR 15N72W. THIS FEATURE IS ADDING PLENTY OF FUEL TO AN ALREADY VERY MOIST AND UNSTABLE AIR MASS IN PLACE OVER AND NEAR THE ISLAND. UPPER DIVERGENCE TO THE SE OF THE UPPER LOW IS SIGNIFICANTLY AIDING THE SCATTERED MODERATE CONVECTIVE ACTIVITY THAT EARLIER TODAY FIRED UP OVER MUCH OF THE DOMINICAN REPUBLIC AS OBSERVED ON SATELLITE IMAGERY...AND AS BEING REPORTED BY THE LATEST SURFACE BASED WEATHER REPORTING SITES THROUGHOUT THE ISLAND. THIS ACTIVITY IS BEING ACCOMPANIED BY FREQUENT LIGHTNING AT TIMES. AS MENTIONED ABOVE UNDER CARIBBEAN SEA...THE UPPER TROUGH IS ONLY EXPECTED TO SLOWLY MOVE EASTWARD THROUGH MON. THERE IS A GOOD POSSIBILITY THAT THIS CONVECTIVE ACTIVITY WILL BE ACTIVE AGAIN ON SUN...BUT PERHAPS A LITTLE LESS ACTIVE ON MON AS THE TROUGH AXIS PULLS JUTS TO THE E OF THE ISLAND.

ATLANTIC OCEAN...

AN UPPER TROUGH ENTERS THE AREA THROUGH 32N56W...AND CONTINUES SW TO 26N63W...TO AN UPPER LOW AT 22N69W...AND SW TO ACROSS HISPANIOLA AND TO THE N CENTRAL CARIBBEAN SEA. AT THE SURFACE... THIS FEATURE IS SEEN AS A TROUGH FROM 32N56W SW TO A WEAK 1015 MB LOW AT 26N60W...AND SW FROM THERE TO NEAR 22N65W. VERY DEEP MOISTURE...IN THE FORM OF OVERCAST MULTILAYER CLOUDS...ARE NOTED TO THE SE OF THE TROUGH AND LOW W OF ABOUT 52W. SCATTERED MODERATE CONVECTION IS OCCURRING FROM 17N-23N BETWEEN 60W-64W. ASSOCIATED HIGH LEVEL DEBRIS BROKEN TO OVERCAST CIRRUS CLOUDS ARE STREAMING EASTWARD FROM THIS ACTIVITY TO NEAR 50W...THEN THINS OUT TO MOSTLY BROKEN CLOUDS TO NEAR 39W. A WEAK BACKDOOR COLD FRONT IS ALONG 30N BETWEEN 70W-78W. NO CONVECTION IS OCCURRING WITH THIS FRONT. THE UPPER TROUGH AND LOW WILL SLOWLY MOVE EASTWARD OVER THE NEXT 48 HOURS. THE WEAK 1015 MB LOW AT 26N60W IS FORECAST TO MOVE NE TO NEAR 27N58W BY SUN AFTERNOON...THEN GRADUALLY DISSIPATE ALONG THE TROUGH ON MON. A SURFACE TROUGH...THAT DURING THE PAST FEW DAYS HAS BEEN STEADILY MOVING WESTWARD...WAS ANALYZED AT 18 UTC FROM JUST NW OF HAITI NNE TO NEAR 27N71W. THIS TROUGH IS ON THE BACK SIDE OF THE UPPER LEVEL LOW AND UPPER TROUGH...WHICH PUTS IT UNDER A REGION OF MODERATE SUBSIDENCE AND DRY SINKING AIR. SO ONLY ISOLATED SHOWERS AND WEAK ISOLATED TSTMS ARE NOTED WITHIN 90 NM OF THE TROUGH. THE TROUGH IS FORECAST TO WASH OUT ON SUN. THE COLD FRONT IS FORECAST TO CLIP FAR NORTHERN WATERS BETWEEN 60W-70W EARLY ON SUN...AND DISSIPATE BY LATE SUN.

OVER THE FAR EASTERN PART OF THE AREA A 1013 MB LOW IS CENTERED AT 26N37W WITH A TROUGH EXTENDING SSW FROM THE LOW TO NEAR 21N40W. THIS LOW REMAINS EMBEDDED UNDERNEATH A BROAD UPPER LOW WHICH IS SUPPORTING WIDELY SCATTERED SHOWERS AND TSTMS FROM 24N TO 28N BETWEEN 26W-33W. THE LOW IS FORECAST TO MOVE SW TO NEAR 25N40W BY SUN AFTERNOON...AND REMAIN NEARLY STATIONARY THROUGH EARLY MON BEFORE OPENING UP TO A TROUGH LATER ON MON AS THE UPPER BROAD LOW PULLS OFF FAR TO THE EASTERN ATLC NEAR THE COAST OF AFRICA. WEAK SURFACE RIDGING WILL REMAIN IN PLACE OVER THE EASTERN ATLC THROUGH MON.

FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE

$$ AGUIRRE

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