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Atlantic Tropical Weather Discussion (Text)



000
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 
WWW.HURRICANES.GOV/MARINE

$$
LEWITSKY

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Page last modified: Thursday, 03-Sep-2015 17:38:48 UTC