[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 091803
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN AUG 09 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
1745 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS RIGHT OFF THE WEST AFRICAN COAST WITH AXIS NEAR
17W...MOVING W AT APPROXIMATELY 5 KT. CIRA LAYER PRECIPITABLE
WATER IMAGERY FROM THE SURFACE TO 850 MB SHOW MODERATE TO HIGH
MOISTURE ASSOCIATED WITH THIS WAVE THAT ALONG WITH AN UPPER
LEVEL DIFFLUENT WIND ENVIRONMENT SUPPORT A CLUSTER OF MODERATE
TO ISOLATED STRONG CONVECTION FROM 13N TO 17N BETWEEN 15W AND
19W AND ISOLATED MODERATE CONVECTION ELSEWHERE FROM 07N TO 20N E
OF 23W.

A TROPICAL WAVE IS IN THE CENTRAL ATLC WITH AXIS NEAR
37W...MOVING W AT APPROXIMATELY 10 KT. CIRA LAYER PRECIPITABLE
WATER IMAGERY FROM THE SURFACE TO 850 MB SHOW MOSTLY A DRY WAVE
ENVIRONMENT BEING CONFIRMED BY THE PRESENCE OF SAHARAN DRY AIR
AND DUST IN METEOSAT ENHANCED IMAGERY. THESE CONDITIONS SUPPORT
LACK OF CONVECTION AT THIS TIME.

A TROPICAL WAVE IS NEARLY 500 NM E OF THE LESSER ANTILLES. ITS
AXIS IS ALONG 52W AND IS MOVING AT APPROXIMATELY 5 KT. CIRA
LAYER PRECIPITABLE WATER IMAGERY FROM THE SURFACE TO 850 MB SHOW
A DRY WAVE ENVIRONMENT N OF 13 N AND MODERATE MOISTURE ENHANCING
ISOLATED SHOWERS FROM 07N TO 12N BETWEEN 50W AND 55W. LACK OF
CONVECTION N OF 13N IS DUE TO THE PRESENCE OF SAHARAN DRY AIR
AND DUST AS DEPICTED BY METEOSAT ENHANCED IMAGERY.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH PASSES THROUGH COASTAL SECTIONS OF GUINEA
NEAR 09N14W TO 07N30W TO 06N42W. THE ITCZ CONTINUES FROM 06N42W
TO 05N50W TO GUYANA NEAR 05N59W. FOR INFORMATION ABOUT
CONVECTION SEE THE TROPICAL WAVES SECTION.

...DISCUSSION...

...THE GULF OF MEXICO...

A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM NEW ENGLAND S OVER
THE W ATLC W OF 70W TO A BASE NEAR 29N IN THE SW N ATLC. THIS
TROUGH ALOFT SUPPORTS A FRONTAL SYSTEM ANALYZED IN THE GULF AS A
STATIONARY FRONT FROM 29N83W TO A 1013 MB LOW NEAR 29N85W TO
SOUTHERN ALABAMA NEAR 31N87W. A SURFACE TROUGH EXTENDS FROM THE
LOW SW TO 26N89W NW TO 27N92W. CIRA LAYER PRECIPITABLE WATER
IMAGERY FROM THE SURFACE TO 850 MB SHOW MODERATE MOISTURE OVER
THE NE GULF THAT ALONG WITH A DIVERGENT ENVIRONMENT IN THE
MIDDLE LEVELS SUPPORT SCATTERED MODERATE CONVECTION AND ISOLATED
TSTMS FROM 25N TO 29N BETWEEN 84W AND 89W. GOES-R CONVECTIVE
INITIATION PRODUCT INDICATES THE CONTINUATION OF ISOLATED TSTMS
DURING THE NEXT TWO HOURS. SW OF THE SURFACE TROUGH TAIL...A
1016 MB HIGH IS NEAR 25N91W...WHICH IS FORECAST TO MOVE TO THE
NW BASIN OVER THE NEXT 48 HOURS. CLEAR SKIES DOMINATE ELSEWHERE
OVER THE GULF...BEING SUPPORTED BY DRY AIR SUBSIDENCE AND STRONG
WIND SHEAR. WINDS ACROSS THE BASIN ARE VARIABLE RANGING FROM 5
TO 10 KT.

...THE CARIBBEAN SEA...

EXCEPT FOR THE SW CARIBBEAN AND CUBA SOUTHERN ADJACENT WATERS...
CIRA LAYER PRECIPITABLE WATER IMAGERY FROM THE SURFACE TO 850 MB
SHOW A DRY ENVIRONMENT ACROSS THE CARIBBEAN WATERS...THUS
RESULTING IN STABILITY AND FAIR WEATHER. OVER THE SW BASIN...A
1010 MB LOW IS OFF THE NW COAST OF COLOMBIA ENHANCING SCATTERED
MODERATE CONVECTION S OF 12N. A BROAD UPPER LEVEL TROUGH
EXTENDING FROM THE SW N ATLC SW TO A BASE S OF HISPANIOLA
SUPPORTS ISOLATED SHOWERS AND TSTMS ALONG SOUTHERN CUBA AND
COASTAL WATERS AS WELL AS ACROSS CENTRAL AND WESTERN HISPANIOLA.
NE TO E WINDS OF 20 TO 25 KT ARE FROM 12N TO 15N BETWEEN 69W AND
76W WITH SEAS TO 8 FT. TRADES OF 15 KT ARE ACROSS THE REMAINDER
BASIN. THE NEXT TROPICAL WAVE IS FORECAST TO ENTER THE E
CARIBBEAN MONDAY MORNING.

...HISPANIOLA...

PATCHES OF MODERATE MOISTURE CONTINUE OVER THE ISLAND AS
INDICATED BY CIRA LAYER PRECIPITABLE WATER IMAGERY FROM THE
SURFACE TO 850 MB. THIS SHALLOW MOISTURE ALONG WITH FORCING
GENERATED BY AN UPPER TROUGH WITH EMBEDDED LOW JUST S OF THE
ISLAND SUPPORT ISOLATED SHOWERS AND TSTMS MAINLY OVER CENTRAL
AND WESTERN PORTIONS OF HISPANIOLA. SHOWERS ARE EXPECTED TO
CONTINUE THROUGH TONIGHT.

THE ATLANTIC OCEAN...

A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM NEW ENGLAND S OVER
THE W ATLC W OF 70W TO A BASE NEAR 29N IN THE SW N ATLC. THIS
TROUGH ALOFT SUPPORTS A FRONTAL SYSTEM ANALYZED AS A COLD FRONT
FROM 30N73W SW TO 28N80W WHERE IT TRANSITIONS TO A STATIONARY
FRONT OVER THE NE GULF OF MEXICO. AHEAD OF THE FRONT...A SURFACE
TROUGH IS FROM 31N70W TO 28N75W TO THE FLORIDA STRAITS NEAR
24N81W. SCATTERED TO ISOLATED SHOWERS AND TSTMS ARE WITHIN 60 NM
EITHER SIDE OF THE TROUGH AXIS. FARTHER EAST...AN UPPER LOW
CONTINUE TO SUPPORT SCATTERED SHOWERS AND TSTMS FROM 20N TO 30N
BETWEEN 62W AND 74W. SURFACE RIDGING DOMINATES ELSEWHERE ACROSS
THE ATLC ALONG WITH FAIR WEATHER. FOR INFORMATION ABOUT TROPICAL
WAVES SEE SECTION AT THE TOP OF THE DISCUSSION.

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

$$
NR
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