[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 262351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU SEP 26 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE AXIS EXTENDS FROM 19N46W TO 10N47W AND MOVES
WEST NEAR 15-20 KT. TOTAL PRECIPITABLE WATER AND WATER VAPOR
IMAGERY SHOW THE WAVE IS EMBEDDED IN A VERY MOIST ENVIRONMENT.
SCATTERED MODERATE CONVECTION AND TSTMS ARE FROM 09N-22N BETWEEN
36W-51W. THE CONVECTION OF THIS WAVE HAS INCREASED OVER THE PAST
SEVERAL HOURS AS THE WAVE MOVES BENEATH UPPER-LEVEL DIFFLUENT
FLOW FROM A LOW CENTERED NEAR 19N52W.

A TROPICAL WAVE AXIS EXTENDS FROM 18N56W TO 10N54W AND MOVES
WEST NEAR 10-15 KT. SIMILAR TO THE PRIOR WAVE...LATEST ASCAT AND
OSCAT PASSES SHOW THE WAVE SIGNAL AT THE SURFACE. TOTAL
PRECIPITABLE WATER IMAGERY SHOW A MODERATE MOIST ENVIRONMENT IN
THE SOUTHERN SECTOR OF THE WAVE WHERE ISOLATED SHOWERS AND TSTMS
ARE OBSERVED FROM 08N-13N BETWEEN 51W-56W. THIS AREA OF SHOWERS
COINCIDES WITH A REGION OF DIFFLUENT FLOW SW OF THE UPPER-LEVEL
LOW CENTERED NEAR 19N52W. THE REMAINDER WAVE ENVIRONMENT IS
VOIDED OF CONVECTION DUE TO DRY AIR SUBSIDENCE.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM THE WEST AFRICAN COAST NEAR
12N17W TO 09N22W 05N28W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
EXTENDS FROM 05N28W TO 04N36W 07N42W. A CLUSTER OF MODERATE TO
ISOLATED STRONG CONVECTION WITH TSTMS IS OVER SENEGAL AND GUINEA-
BISSAU EXTENDING WITHIN 160 NM OFFSHORE FROM 10N-16N. ISOLATED
SHOWERS ARE FROM 06N-10N BETWEEN 24W-30W.

...DISCUSSION...

GULF OF MEXICO...
EXCEPT FOR THE SW GULF...TOTAL PRECIPITABLE WATER AND WATER
VAPOR IMAGERY SHOW VERY DRY AIR ACROSS THE BASIN WHICH IS
SUPPORTING FAIR WEATHER. IN THE UPPER-LEVEL...A BROAD TROUGH
AXIS EXTENDS SW FROM A LOW CENTERED NEAR 45N55W TO THE EASTERN
GULF E OF 90W TO SUPPORT A COLD FRONT MOVING ACROSS CENTRAL-
SOUTHERN FLORIDA TO 26N82W TO 25N90W. ISOLATED SHOWERS ARE
POSSIBLE WITHIN 70 NM SOUTH OF THE FRONTAL BOUNDARY. A VERY
MOIST ENVIRONMENT IS OVER THE SW GULF...HOWEVER THERE ARE NO
MIDDLE TO UPPER LEVEL SYNOPTIC FEATURES SUPPORTING CONVECTIVE
ACTIVITY.

THE COLD FRONT IS EXPECTED TO DRIFT SE TONIGHT AND DISSIPATE
OVER THE SW NORTH ATLC BY EARLY FRIDAY. ON FRIDAY AFTERNOON...A
RIDGE AXIS WILL START TO MOVE ACROSS THE BASIN BUILDING RETURN
FLOW IN THE RANGE OF 10-15 KT THROUGH SATURDAY NIGHT.

CARIBBEAN SEA...
TOTAL PRECIPITABLE WATER IMAGERY SHOW A SECTOR OF MODERATE
MOISTURE IN THE WESTERN CARIBBEAN BETWEEN 74W-85W. THIS MOISTURE
ALONG WITH MIDDLE TO UPPER LEVEL DIFFLUENCE IS SUPPORTING
SHOWERS AND TSTMS ACROSS EASTERN CUBA AND HAITI. SCATTERED
SHOWERS ARE ALSO OBSERVED IN JAMAICA AND THE MONA PASSAGE. IN
THE SOUTHERN CARIBBEAN...A VERY MOIST ENVIRONMENT...UPPER LEVEL
DIFFLUENT FLOW AND THE MONSOON TROUGH SUPPORT SCATTERED MODERATE
CONVECTION S OF 14N BETWEEN 72W-83W. THIS CONVECTION EXTENDS
INLAND NICARAGUA...COSTA RICA...PANAMA AND NORTHERN COLOMBIA.

A LOW PRESSURE CENTER IS EXPECTED TO DEVELOP OVER THE SOUTHERN
BASIN AT OR IN CLOSE PROXIMITY TO THE MONSOON TROUGH AXIS BY
FRIDAY AFTERNOON. A TROPICAL WAVE IS EXPECTED TO MOVE ACROSS THE
EASTERN CARIBBEAN EARLY EVENING FRIDAY BUT NO MAJOR CONVECTIVE
ACTIVITY IS EXPECTED.

HISPANIOLA...
A SECTOR OF MODERATE MOISTURE IN THE WESTERN CARIBBEAN BETWEEN
74W-85W ALONG WITH MIDDLE TO UPPER LEVEL DIFFLUENCE IS
SUPPORTING SHOWERS AND TSTMS OVER HAITI AND WESTERN DOMINICAN
REPUBLIC. IN THE DAYS AHEAD...THE SOUTHERN EXTENT OF A WEAK
TROPICAL WAVE CURRENTLY ALONG 63W IS FORECAST TO CLIP ACROSS THE
ISLAND SATURDAY PROVIDING A POSSIBLE SLIGHT INCREASE IN
CONVECTION DURING THE AFTERNOON AND EVENING HOURS.

ATLANTIC OCEAN...
IN THE UPPER-LEVEL...A BROAD TROUGH AXIS EXTENDS SW FROM A LOW
CENTERED NEAR 45N55W TO THE FLORIDA PENINSULA TO SUPPORT A
FRONTAL SYSTEM THAT CONNECTS THROUGH A 1007 MB LOW NEAR 30N76W.
A COLD FRONT EXTENDS SW FROM THE LOW TO VERO BEACH FLORIDA TO
THE EASTERN GULF NEAR 25N90W. A STATIONARY FRONT DEPARTS FROM
THE LOW E-NE ALONG 30N74W TO 29N70W TO A 1004 MB LOW NEAR
31N67W. SCATTERED SHOWERS AND TSTMS ASSOCIATED WITH THIS FRONTAL
SYSTEM ARE N OF 24N WEST OF 57W...INCLUDING THE BAHAMAS.
OTHERWISE... THE REMAINDER OF THE CENTRAL AND EASTERN ATLC
REMAINS UNDER THE INFLUENCE OF A FAIRLY BROAD SURFACE RIDGE
ANCHORED BY A 1019 MB HIGH CENTERED NEAR 24N38W WHICH IS
EXPECTED TO REMAIN NEARLY STATIONARY.

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

$$
NR


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