[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 071807
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT SEP 07 2013

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...
A TROPICAL WAVE ASSOCIATED WITH A 1008 MB LOW PRESSURE CENTER IS
OVER SENEGAL AFRICA AND IS EXPECTED TO COME OFF THE WEST AFRICAN
COAST LATER THIS AFTERNOON. TOTAL PRECIPITABLE WATER IMAGERY
SHOW A ZONE OF MAXIMUM MOISTURE RIGHT OFF THE COAST WHICH ALONG
WITH LOW DEEP LAYER ENVIRONMENTAL WIND SHEAR MAY ASSIST IN THE
ORGANIZATION OF THIS SYSTEM. SPIRAL RAINBANDS ARE FROM 07N-18N E
OF 26W. THIS SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

...TROPICAL WAVES...
A TROPICAL WAVE ASSOCIATED WITH A 1009 MB LOW PRESSURE CENTER IS
IN THE CENTRAL TROPICAL ATLC. THE WAVE AXIS IS ALONG 20N34W TO
THE LOW CENTER NEAR 13N34W TO 11N34W WHERE A BLOCKING PATTERN IN
THE MIDDLE TO UPPER LEVELS MAINTAINS THIS SYSTEM NEARLY
STATIONARY. TOTAL PRECIPITABLE WATER IMAGERY INDICATE THAT
MOISTURE WITHIN THE WAVE ENVIRONMENT HAS BEEN AUGMENTING IN THE
PAST SEVERAL HOURS. HOWEVER...SAHARAN DRY AIR MOSTLY TO THE W OF
THE AXIS IS LIMITING CONVECTIVE ACTIVITY. SCATTERED MODERATE
CONVECTION IS FROM 14N-19N BETWEEN 28W-33W AND WITHIN 120 NM W
OF THE AXIS FROM 16N-18N.

A TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN EXTENDING AN AXIS
FROM 19N79W TO 08N80W WHICH MOVES W NEAR 5 KT. THE WAVE
CONTINUES EMBEDDED WITHIN AN AREA OF HIGH MOISTURE THAT COVERS
THIS REGION OF THE CARIBBEAN AS DEPICTED ON TOTAL PRECIPITABLE
WATER IMAGERY. CLUSTERS OF MODERATE CONVECTION WITH EMBEDDED
TSTMS ASSOCIATED WITH THE WAVE AND THE MONSOON TROUGH ARE S OF
12N W OF 81W AS WELL AS S OF 13N E OF 79W. SCATTERED MODERATE
CONVECTION AND TSTMS IN THE NORTHERN REGION OF THE WAVE ARE FROM
15N-20N BETWEEN 78W-84W.

A WEAK TROPICAL WAVE IN THE FAR W CARIBBEAN WILL BE ENTERING THE
YUCATAN PENINSULA AND GUATEMALA LATER THIS AFTERNOON.
CURRENTLY...ITS AXIS IS ALONG 20N87W TO 11N88W AND HAS BEEN
MOVING NEAR 5 KT. AN ELONGATED UPPER LEVEL TROUGH SUPPORTS IT
AND IS ENHANCING SCATTERED MODERATE CONVECTION FROM 19N-21N
BETWEEN 84W-87W. THIS WAVE IS EXPECTED TO DISSIPATE IN LESS THAN
24 HOURS.

...THE ITCZ/THE MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS ACROSS AFRICA INTO THE E
TROPICAL ATLC NEAR 13N16W AND CONTINUES ALONG 13N26W THROUGH THE
LOW/TROPICAL WAVE NEAR 13N34W TO 08N43W. THE ITCZ BEGINS NEAR
08N34W AND CONTINUES ALONG 08N50W TO 11N57W. BESIDES THE
CONVECTION ASSOCIATED WITH THE TRPCL WAVE ALREADY
DISCUSSED...SPIRAL RAINBANDS ASSOCIATED WITH A 1008 MB LOW
PRESSURE OVER SENEGAL ARE FROM 07N-16N E OF 27W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE TROUGH IS ALONG THE WESTERN GULF FROM 27N97W TO
18N94W. THIS TROUGH IS LOCATED IN AN AREA OF UPPER-LEVEL
DIFFLUENCE WHICH IS SUPPORTING NUMEROUS MODERATE CONVECTION AND
TSTMS S OF 29N W OF 89W. A BROAD UPPER-LEVEL TROUGH COVERS THE
NORTH-CENTRAL AND EASTERN GULF E OF 90W AND SUPPORTS TWO SURFACE
TROUGHS. THE FIRST TROUGH EXTENDS FROM 27N87W TO 28N95W AND IS
GENERATING SHOWERS AND TSTMS N OF 27N W OF 88W. THE SECOND
TROUGH MOVES FROM THE WESTERN BAHAMAS TO THE STRAITS OF FLORIDA
AND IS GENERATING SHOWERS AND TSTMS OVER SOUTHERN FLORIDA AS
WELL AS THE SE GULF S OF 26N E OF 86W. WEAK SURFACE RIDGING WILL
PERSIST ACROSS THE N GULF THROUGH SUN NIGHT BEFORE IT IS
REPLACED BY STRONGER HIGH PRESSURE FROM THE W ATLC.

CARIBBEAN SEA...
A TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN EXTENDING AN AXIS
FROM 19N79W TO 08N80W. THE WAVE CONTINUES EMBEDDED WITHIN AN
AREA OF HIGH MOISTURE THAT COVERS THIS REGION OF THE CARIBBEAN
AS DEPICTED ON TOTAL PRECIPITABLE WATER IMAGERY. CLUSTERS OF
MODERATE CONVECTION WITH EMBEDDED TSTMS ASSOCIATED WITH THE WAVE
AND THE MONSOON TROUGH ARE S OF 12N W OF 81W AS WELL AS S OF 13N
E OF 79W. SCATTERED MODERATE CONVECTION AND TSTMS IN THE
NORTHERN REGION OF THE WAVE ARE FROM 15N-20N BETWEEN 78W-84W. A
WEAK TROPICAL WAVE IS IN THE FAR W CARIBBEAN WITH AXIS EXTENDING
ALONG 20N87W TO 11N88W. AN ELONGATED UPPER LEVEL TROUGH SUPPORTS
IT AND IS ENHANCING SCATTERED MODERATE CONVECTION FROM 19N-21N
BETWEEN 84W-87W. MIDDLE-LEVEL DIFFLUENCE CONTINUES TO SUPPORT
THE CONVECTION ASSOCIATED WITH THE REMNANTS OF GABRIELLE.
SCATTERED SHOWERS AND TSTMS ARE ACROSS HISPANIOLA...THE MONA
PASSAGE AS WELL AS THE EASTERN CARIBBEAN N OF 13N BETWEEN 64W-
75W. THE REMNANT LOW OF GABRIELLE WILL CONTINUE TO MOVE AWAY
FROM THE CARIBBEAN THROUGH SUN. FRESH SE WINDS WILL DEVELOP
ACROSS MUCH OF THE E CARIBBEAN THROUGH SUN. THE W CARIBBEAN
TROPICAL WAVE WILL MOVE OVER THE YUCATAN LATER THIS AFTERNOON.
THE CENTRAL CARIBBEAN TROPICAL WAVE WILL MOVE INLAND OVER
CENTRAL AMERICA TONIGHT.

HISPANIOLA...
SCATTERED SHOWERS AND THUNDERSTORMS REMAIN ACROSS THE ISLAND
BEING SUPPORTED BY MIDDLE-LEVEL DIFFLUENCE. THIS CONVECTION
ASSOCIATED WITH THE REMNANTS OF GABRIELLE COULD CONTINUE THROUGH
SUN WHEN THE LOW WILL DISSIPATE AS THE SURFACE TROUGH DRIFTS W.

ATLANTIC OCEAN...
A BROAD UPPER-LEVEL TROUGH COVERS THE W ATLC N OF 26N WHICH
SUPPORTS A SURFACE TROUGH THAT EXTENDS FROM THE WESTERN BAHAMAS
TO THE STRAITS OF FLORIDA. THIS TROUGH IS GENERATING SHOWERS AND
TSTMS FROM 24N-28N W OF 77W. THE UPPER-LEVEL TROUGH ALSO
SUPPORTS A 1009 MB LOW PRESSURE CENTER NEAR 22N69W WHICH IS
ASSOCIATED WITH THE REMNANTS OF GABRIELLE. A SURFACE TROUGH
EXTENDS N-NE FROM THE LOW ALONG 22N69W TO 28N67W TO 32N64W. THIS
SYSTEM IS GENERATING SCATTERED MODERATE SHOWERS/ISOLATED
THUNDERSTORMS FROM 18N-25N BETWEEN 64W-69W AS WELL AS N OF 20N
BETWEEN 54W-65W. ANOTHER SURFACE TROUGH EXTENDS FROM 33N42W TO
26N43W BUT HAS NO CONVECTION ASSOCIATED WITH IT. BESIDES THE
TRPCL WAVES ALREADY DISCUSSED...THE REMAINDER OF THE ATLC IS
DOMINATED BY A SURFACE RIDGE ANCHORED BY A SET OF HIGH PRESSURE
CENTERS N OF THE DISCUSSION AREA. THE REMNANT LOW OF GABRIELLE
WILL MOVE SLOWLY NW TO N. THE SURFACE TROUGH IS EXPECTED TO
DRIFT W THROUGH TONIGHT WHILE THE LOW IS EXPECTED TO DISSIPATE
TUE.

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

$$
NR

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