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AXNT20 KNHC 031738
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU SEP 03 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.


...SPECIAL FEATURES...

TROPICAL STORM FRED CENTERED NEAR 21.5N 34.1W AT 03/1500 UTC OR 660 NM WNW OF THE CAPE VERDE ISLANDS MOVING WNW AT 8 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. SEE LATEST NHC FORECAST /ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. SCATTERED MODERATE TO STRONG CONVECTION IS BETWEEN 30 NM AND 105 NM IN THE N QUADRANT OF FRED. FRED IS FORECAST TO WEAKEN TO A TROPICAL DEPRESSION THIS EVENING...THEN TO A POST- TROPICAL REMNANT LOW BY EARLY FRIDAY.


...TROPICAL WAVES...

TROPICAL WAVE OVER WESTERN AFRICA EXTENDS FROM 08N13W TO 17N13W MOVING W AROUND 10 KT. THE WAVE COINCIDES WITH 700 MB TROUGHING BETWEEN 11W-16W AND IS LARGELY LOW-AMPLITUDE. 850 MB VORTICITY MAXIMUM IS LOCATED NEAR THE WAVE FROM 07N-12W. ISOLATED TO SCATTERED MODERATE CONVECTION IS FROM 06N-14N BETWEEN 13W-18W.

TROPICAL WAVE EXTENDS FROM 11N25W TO 21N26W WITH 1012 MB LOW PRES ALONG THE WAVE NEAR 13N25W MOVING W AT 10-15 KT. THE WAVE COINCIDES WITH 700 MB TROUGHING BETWEEN 22W-27W AND 850 MB VORTICITY MAXIMUM FROM 17N-21W. SSMI TPW INDICATES THE WAVE IS EMBEDDED WITHIN A SURGE OF DEEP MOISTURE. SCATTERED MODERATE CONVECTION IS FROM 10N-13N BETWEEN 25N-29W.

TROPICAL WAVE EXTENDS FROM 08N45W TO 17N47W MOVING W AT 5-10 KT. THE WAVE COINCIDES WITH 700 MB TROUGHING BETWEEN 44W-50W AND 850 MB VORTICITY MAXIMUM FROM 09N-13W. SSMI TPW INDICATES THE WAVE IS EMBEDDED WITHIN A SURGE OF MOISTURE WHICH IS BEING SOMEWHAT HINDERED BY SURROUNDING SAHARAN DRY AIR AND DUST. THESE CONDITIONS ARE PREVENTING SIGNIFICANT CONVECTION FROM ACCOMPANYING THE WAVE.

TROPICAL WAVE EXTENDS FROM 18N81W TO 09N82W APPROACHING CENTRAL AMERICA MOVING W AT 15-20 KT. THE WAVE COINCIDES WITH BROAD 700 MB TROUGHING BETWEEN 78W-82W AND 850 MB VORTICITY MAXIMUM FROM 09N-13W. SSMI TPW INDICATES THE WAVE IS EMBEDDED WITHIN A SURGE OF MOISTURE. SCATTERED TO NUMEROUS MODERATE CONVECTION IS FROM 09N-16N BETWEEN 78W-85W.


...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM THE AFRICAN COAST NEAR 17N16W TO 13N25W TO 08N45W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 08N45W TO THE COAST OF SOUTH AMERICA NEAR 06N57W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 09N-13N BETWEEN 32W-42W.


...DISCUSSION...

GULF OF MEXICO... A MIDDLE TO UPPER LEVEL TROUGH IS LOCATED IN THE WESTERN GULF ALONG 23N96W. ANOTHER MIDDLE TO UPPER LEVEL TROUGH IS MOVING ACROSS THE SOUTHEASTERN UNITED STATES FROM WESTERN NORTH CAROLINA TO JUST S OF LOUISIANA NEAR 28N94W. THESE TO UPPER FEATURES ARE SUPPORTING A SURFACE TROUGH WHICH EXTENDS ACROSS ROUGHLY THE SAME AREA WITH SCATTERED TSTMS OCCURRING ACROSS THE GULF WATERS W OF A LINE FROM 30N84W TO 27N87W TO 26N93W TO 20N97W. AN UPPER LEVEL ANTICYCLONE IS LOCATED NEAR 27N92W WITH A RIDGE AXIS EXTENDING TO THE E ACROSS THE GULF OVER 26N. SURFACE HIGH PRES OF 1016 MB IS IN THE NE GULF NEAR 27N85W WITH FAIRLY BENIGN AND TRANQUIL CONDITIONS ELSEWHERE ACROSS THE GULF OUTSIDE OF THE AREA OF CONVECTION. THE SURFACE HIGH IS FORECAST TO MEANDER IN THE NE GULF THROUGH THE NEXT 48 HOURS. LIGHT TO MODERATE ANTICYCLONIC FLOW AND 1-3 FT SEAS WILL PREVAIL ACROSS THE BASIN...EXCEPT NW OF THE YUCATAN PENINSULA WHERE WINDS WILL INCREASE TO FRESH BUILDING SEAS TO 3-5 FT DURING THE EVENING AND OVERNIGHT HOURS AS DIURNAL TROUGHING DEVELOPS OVER THE PENINSULA PUSHING W INTO THE SW GULF BY THE MORNING HOURS EACH DAY.

CARIBBEAN SEA... AN UPPER LEVEL LOW CENTERED OVER THE WESTERN CARIBBEAN AND GULF OF HONDURAS NEAR 17N86W INFLUENCES MUCH OF THE BASIN W OF 74W. THIS LOW IS HELPING TO ENHANCE CONVECTION IN THE WESTERN CARIBBEAN NEAR A TROPICAL WAVE AS IS DESCRIBED IN THE TROPICAL WAVE SECTION ABOVE. OTHERWISE...ANOTHER UPPER LEVEL LOW IS IN THE NE CARIBBEAN JUST S OF PUERTO RICO NEAR 17N67W. MAINLY DRY AND STABLE CONDITIONS EXIST ACROSS THE REMAINDER OF THE BASIN AWAY FROM THE TROPICAL WAVE. EXPECT GENTLE TO MODERATE TRADES IN THE NW CARIBBEAN AND MODERATE TRADES ELSEWHERE ACROSS THE BASIN DURING THE NEXT 48 HOURS...EXCEPT IN THE S CENTRAL CARIBBEAN NW OF THE COAST OF COLOMBIA AND N OF NW VENEZUELA WHERE WINDS WILL PULSE TO FRESH TO STRONG EACH NIGHT AS THE PRES GRADIENT DIURNALLY TIGHTENS. SEAS WILL BE 1-3 FT IN THE FAR NW CARIBBEAN
...6-9 FT NEAR THE COAST OF COLOMBIA...AND 3-6 FT ELSEWHERE.


...HISPANIOLA... CURRENTLY...MAINLY MOSTLY CLEAR SKIES ARE NOTED ON VISIBLE SATELLITE IMAGERY LARGELY DUE TO RELATIVELY DRY CONDITIONS ALOFT AND OVERALL STABILITY PROVIDED BY THE SUBTROPICAL RIDGE ANCHORED ACROSS THE SW NORTH ATLC REGION. A FEW ISOLATED TSTMS HAVE RECENTLY DEVELOPED OVER SW HAITI WITH A WEAK MIDDLE TO UPPER LEVEL TROUGH NEARBY COMBINED WITH DAYTIME HEATING AND OROGRAPHIC LIFTING. THIS UPPER TROUGH WILL GRADUALLY BECOME N/S ORIENTATED TONIGHT GIVING THE ISLAND N FLOW ALOFT FRI AND SAT. MOISTURE WILL INCREASE AGAIN SAT MORNING INCREASING THE CHANCE OF AFTERNOON SHOWERS/TSTMS SAT.

ATLANTIC OCEAN... AN UPPER LEVEL RIDGE EXTENDS FROM THE FLORIDA PENINSULA NEAR 27N81W TO 25N64W. SURFACE HIGH PRES AT 1016 MB IS NEAR 25N66W. MEANWHILE THE REMNANT LOW CIRCULATION OF ERIKA HAS MOVED OFF OF THE GEORGIA COAST AT 1013 MB NEAR 31.5N81W WITH TROUGHING EXTENDING FROM THE LOW TO THE E-SE THROUGH 30N73W TO 29N68W. SCATTERED TSTMS ARE OCCURRING N OF 29N W OF 70W WITH ADDITIONAL ACTIVITY FROM N OF 26N BETWEEN 57W AND 70W. THIS LOW IS FORECAST TO MOVE E-SE AT AROUND 10 KT THROUGH THE NEXT 48 HOURS. CURRENTLY...SCATTEROMETER DATA INDICATES MAINLY LIGHT AND VARIABLE WINDS ACROSS THE SW N ATLC OFFSHORE WATERS WHICH WILL PREVAIL THROUGH THE NEXT 48 HOURS...EXCEPT JUST AHEAD OF THE TROUGHING WHERE WINDS WILL INCREASE TO MODERATE LEVELS. SEAS WILL BE PRIMARILY 2-4 FT OUTSIDE OF THE BAHAMAS...LOCALLY UP TO 5 FT WHERE THE STRONGEST WINDS NEAR THE TROUGHING WILL OCCUR.

SURFACE LOW PRES AT 1012 MB IS LOCATED TO THE E NEAR 27.5N52W WITH A TROUGH REACHING FROM 31N44W THROUGH THE LOW TO 23N58W. ISOLATED TO SCATTERED TSTMS ARE OCCURRING N OF 26N WITHIN 90-120 NM EITHER SIDE OF THE TROUGH. THE LOW AND TROUGH ARE FORECAST TO MEANDER DURING THE NEXT 48 HOURS WHILE GRADUALLY WEAKENING AND BECOMING DIFFUSE. FINALLY...AS MENTIONED ABOVE...THE MAIN FOCUS FOR THE EASTERN ATLC IS TROPICAL STORM FRED AS IT TRACKS WNW ACROSS THE OPEN TROPICAL EASTERN ATLC WATERS THIS AFTERNOON.

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

$$ LEWITSKY

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