Tropical Weather Discussion
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000
AXNT20 KNHC 041757
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI SEP 04 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 DEPRESSION FRED CENTERED NEAR 22.3N 38.3W AT 04/1500
UTC OR ABOUT 1110 NM SW OF THE AZORES...MOVING WNW AT 8 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED
WIND SPEED IS 30 KT WITH GUSTS TO 35 KT. ISOLATED MODERATE
CONVECTION IS WITHIN 200 NM OF THE CENTER IN THE EASTERN SEMI-
CIRCLE OF THE SYSTEM. PLEASE SEE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.

A TROPICAL WAVE IS BETWEEN THE AFRICAN COAST AND THE CAPE VERDE
ISLANDS WITH AN AXIS EXTENDING FROM 18N20W...THROUGH A 1010 MB
LOW NEAR 11N20W TO 08N20W. SCATTERED MODERATE CONVECTION IS FROM
07N TO 13N BETWEEN 17W AND 25W. THIS SYSTEM SHOWS SIGNS OF
ORGANIZATION AND HAS A MEDIUM CHANCE OF DEVELOPING INTO A
TROPICAL CYCLONE OVER THE NEXT 48 HOURS AS IT MOVES W AT 15 TO
20 KT.

...TROPICAL WAVES...

A TROPICAL WAVE BETWEEN THE AFRICAN COAST AND CAPE VERDE ISLANDS
INCLUDES THE SPECIAL FEATURE LOW. PLEASE REFER TO THE SPECIAL
FEATURES SECTION ABOVE FOR MORE DETAILS.

A TROPICAL WAVE OVER THE EASTERN ATLC HAS AN AXIS THAT EXTENDS
FROM 18N28W...THROUGH A 1012 MB LOW NEAR 12N28W...TO
11N28W...MOVING W AT AROUND 15 KT OVER THE PAST 24 HOURS. SSMI
TPW SHOWS THE WAVE EMBEDDED IN HIGH MOISTURE S OF 14N. AN
INVERTED 700 MB TROUGH IS INDICATED IN MODEL FIELDS BETWEEN 26W
AND 33W. SCATTERED MODERATE CONVECTION IS FROM 10N TO 14N
BETWEEN 27W AND 31W.

A TROPICAL WAVE IS OVER THE CENTRAL ATLC WITH AN AXIS EXTENDING
FROM 16N52W TO 09N55W...MOVING W AT 15 TO 20 KT OVER THE PAST 24
HOURS. MODERATE MOISTURE IS NOTED S OF 10N WITH DRY AIR N OF 10N
IN THE ENVIRONMENT OF THIS WAVE. NO DEEP CONVECTION IS OCCURRING
AT THIS TIME.

A TROPICAL WAVE IS OVER THE EASTERN CARIBBEAN WITH AN AXIS
EXTENDING FROM 19N63W TO 11N64W...MOVING W AT AROUND 15 KT. THIS
WAVE IS DEPICTED BY 700 MB MODEL FIELDS WITH A TROUGH NOTED
BETWEEN 60W AND 65W. ONLY SHALLOW MOISTURE IS NOTED WITH THIS
TROPICAL WAVE. NO DEEP CONVECTION IS OCCURRING AT THIS TIME.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM OVER AFRICA INTO THE E
TROPICAL ATLC NEAR 13N17W...THROUGH THE 1010 MB LOW/TROPICAL
WAVE NEAR 11N20W...THROUGH THE 1012 MB LOW/TROPICAL WAVE NEAR
12N28W...TO 11N37W...WHERE THE ITCZ BEGINS AND CONTINUES TO
10N53W. OTHER THAN CONVECTION ASSOCIATED WITH THE TWO
LOWS...ISOLATED MODERATE CONVECTION IS FROM 07N TO 14N BETWEEN
31W AND 48W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER RIDGE CENTERED OVER MEXICO HAS AN AXIS THAT EXTENDS
EASTWARD OVER THE MAJORITY OF THE GULF BASIN. AN UPPER TROUGH
JUST E OF THE SE US ATLC COAST HAS AN AXIS THAT EXTENDS OVER THE
NE GULF. THIS UPPER TROUGH SUPPORTS A SURFACE TROUGH THAT
EXTENDS ACROSS N FL TO THE NE GULF COAST NEAR CEDAR
KEY...SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS FROM 28N TO
29N E OF 85W. UPPER LEVEL DIFFLUENCE BETWEEN THE RIDGE AXIS AND
UPPER TROUGH SUPPORTS ISOLATED MODERATE CONVECTION FROM 25N TO
30N BETWEEN 85W AND 89W. ELSEWHERE...A DIURNAL SURFACE TROUGH
OVER THE SW GULF SUPPORTS ISOLATED THUNDERSTORMS FROM 18N TO 23N
BETWEEN 93W AND 97W. A SURFACE HIGH CENTER OF 1016 MB NEAR
27N87W SUPPORTS E TO SE WINDS OF 10 TO 15 KT OVER THE S AND W
GULF. N TO NW WINDS OF 5 TO 10 KT ARE E OF 85W. GENTLE VARIABLE
WINDS ARE NEAR THE HIGH CENTER. OVER THE NEXT 24 HOURS THE
SURFACE TROUGH OVER FL WILL EXPAND W OVER THE NORTHERN GULF WITH
CONVECTION.

CARIBBEAN SEA...
A PAIR OF UPPER LOWS ARE OVER THE CARIBBEAN WITH CENTERS LOCATED
NEAR 16N88W AND PUERTO RICO. UPPER LEVEL RIDGING RESIDES BETWEEN
THESE TWO LOWS OVER THE S CENTRAL CARIBBEAN. THE WESTERNMOST
UPPER LOW SUPPORTS ISOLATED THUNDERSTORMS FROM 15N TO 19N W OF
84W. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE UPPER RIDGE
SUPPORTS SCATTERED MODERATE CONVECTION S OF 13N W OF 78W. DRY
AIR AND STRONG SHEAR OVER THE EASTERN CARIBBEAN IS INHIBITING
CONVECTION ASSOCIATED WITH THE EASTERNMOST UPPER LOW. A TROPICAL
WAVE IS OVER THE E CARIBBEAN. PLEASE REFER TO THE TROPICAL WAVES
SECTION FOR MORE DETAILS. OVER THE NEXT 24 HOURS CONVECTION WILL
CONTINUE NEAR THE UPPER LOW OVER THE NW CARIBBEAN AND OVER THE
SW CARIBBEAN.

...HISPANIOLA...
SHALLOW MOISTURE AND DAYTIME HEATING WILL SUPPORT ISOLATED
SHOWERS AND THUNDERSTORMS OVER THE ISLAND THIS AFTERNOON AND
EVENING. FAIR WEATHER IS EXPECTED TONIGHT. A SIMILAR PATTERN IS
FORECAST ONCE AGAIN FOR SATURDAY AND SATURDAY NIGHT.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH JUST E OF THE SE US COAST SUPPORTS A 1012
MB SURFACE LOW NEAR 30N77W WITH A SURFACE TROUGH EXTENDING FROM
31N76W THROUGH THE SURFACE LOW TO N FL NEAR 29N83W. SCATTERED
MODERATE AND ISOLATED STRONG CONVECTION ARE FROM 27N TO 31N
BETWEEN 72W AND 77W...AND WITHIN 140 NM S OF THE SURFACE TROUGH
AXIS W OF 77W...INCLUDING THE N BAHAMAS. ANOTHER UPPER TROUGH
ALONG 65W SUPPORTS A SURFACE TROUGH FROM 31N64W TO 27N67W. THESE
TWO FEATURES SUPPORT SCATTERED MODERATE CONVECTION FROM 27N TO
31N BETWEEN 55W AND 65W. FARTHER EAST...A WEAK 1016 MB LOW IS
CENTERED NEAR 31N49W WITH A SURFACE TROUGH EXTENDING SW FROM THE
SURFACE LOW TO 26N53W. A SHORTWAVE TROUGH IS ALONG
48W...COMBINING WITH THESE SURFACE FEATURES TO SUPPORT CLUSTERS
OF MODERATE CONVECTION FROM 28N TO 31N BETWEEN 43W AND 48W.
TROPICAL DEPRESSION FRED AND A SPECIAL FEATURE LOW WITH
ASSOCIATED TROPICAL WAVE ARE OVER THE CENTRAL AND EASTERN
ATLC...RESPECTIVELY. PLEASE REFER TO THE SPECIAL FEATURES
SECTION FOR MORE DETAILS. TWO OTHER TROPICAL WAVES ARE OVER THE
TROPICAL ATLC. PLEASE REFER TO THE TROPICAL WAVES SECTION FOR
MORE DETAILS. OVER THE NEXT 24 HOURS EXPECT CONVECTION TO BE
LIKELY N OF 25N W OF 55W WITH THE TWO WESTERN ATLC SURFACE
TROUGHS AND THE W ATLC SURFACE LOW.

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

$$
LATTO



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