[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202350
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU SEP 20 2012

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.

...SPECIAL FEATURES...

TROPICAL STORM NADINE IS CENTERED NEAR X36.0 28.1W AT 21/0000
UTC OR ABOUT ABOUT 148 NM S OF PICO IN THE AZORES MOVING ESE AT
7 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 981 MB. MAXIMUM
SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SEE LATEST
NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS
MIATCPAT4/ WTNT34 AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. SCATTERED
MODERATE CONVECTION IS FROM 37N-39N BETWEEN 25W-30W. SCATTERED
SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS COVER THE REMAINDER
OF THE AREA FROM 35N-40N BETWEEN 22W-32W.

A LARGE DEEP LAYERED LOW IS IN THE W/CENTRAL ATLC NEAR 32N55W
SUPPORTING A 1006 MB SURFACE LOW NEAR 31N54W WITH A SURFACE
TROUGH EXTENDING ALONG 29N53W TO 24N59W AND A SECOND 1010 MB LOW
NEAR 32N53W. CONDITIONS APPEAR FAVORABLE FOR GRADUAL DEVELOPMENT
OF THE 1006 MB LOW AS IT MOVES W TO WNW NEAR 9 KT OVER THE NEXT
DAY OR SO. CONDITIONS APPEAR FAVORABLE FOR GRADUAL DEVELOPMENT
DURING THE NEXT DAY OR SO BEFORE UPPER-LEVEL WINDS BECOME LESS
CONDUCIVE ON SATURDAY. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING
A SUBTROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES WNW
NEAR 9 KT. CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
ARE N OF 26N BETWEEN 45W-59W AND FROM 21N-26N BETWEEN 48W-54W.

...TROPICAL WAVES...

TROPICAL WAVE W OF THE CAPE VERDE ISLANDS EXTENDS FROM 20N33W
ALONG 15N34W TO 11N35W MOVING W 20-25 KT. WAVE IS EMBEDDED
WITHIN A SURGE OF DEEP MOISTURE WITH A SWATH OF DRY AIR UNDER
CUTTING THE MOISTURE ALONG 13N AS DEPICTED ON TOTAL PRECIPITABLE
WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
WITHIN 30 NM OF LINE FROM 13N38W TO 16N37W.

TROPICAL WAVE E OF THE LESSER ANTILLES EXTENDS FROM 20N52W TO
13N57W MOVING W NEAR 15 KT. WAVE IS EMBEDDED WITHIN AN ISOLATED
SURGE OF DEEP MOISTURE AS DEPICTED ON TOTAL PRECIPITABLE WATER
IMAGERY. ISOLATED SHOWERS/THUNDERSTORMS ARE WITHIN 120 NM EITHER
SIDE OF THE WAVE AXIS.

TROPICAL WAVE IN THE CARIBBEAN EXTENDS 22N78W TO 14N81W MOVING W
10-15 KT. WAVE IS EMBEDDED WITHIN A BROAD AREA OF DEEP MOISTURE
THAT COVERS THE ENTIRE CARIBBEAN AS DEPICTED ON TOTAL
PRECIPITABLE WATER IMAGERY. SCATTERED SHOWERS/THUNDERSTORMS ARE
WITHIN 240 NM W OF THE WAVE AXIS.


...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA INTO THE E TROPICAL
ATLC NEAR 14N16W CONTINUING ALONG 9N23W TO 7N37W WHERE THE ITCZ
CONTINUES ALONG 6N45W INTO SOUTH AMERICA NEAR 4N53W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60/75 NM OF LINE
FROM 9N16W TO 12N19W. CLUSTERS OF SCATTERED MODERATE CONVECTION
ARE FROM 5N-8N BETWEEN 17W-44W.

...DISCUSSION...

GULF OF MEXICO...
BROAD UPPER TROUGH REMAINS OVER THE E CONUS INTO THE GULF N OF
20N SUPPORTING A STATIONARY FRONT THAT AT 20/2100 UTC EXTENDS
FROM THE W ATLC ACROSS FLORIDA INTO THE GULF NEAR FORT MYERS
ALONG 26N86W TO 26N91W THEN S INTO THE BAY OF CAMPECHE TO NEAR
19N93W. CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE
WITHIN 120/150 NM N OF THE FRONT E OF 91W AND S OF THE FRONT TO
OVER FLORIDA...CUBA...AND THE YUCATAN PENINSULA. AN UPPER RIDGE
COVERS THE FAR S GULF WITH THE RIDGE AXIS OVER S MEXICO
ENHANCING ISOLATED SHOWERS/THUNDERSTORMS WITHIN 60 NM ALONG THE
COAST OF S MEXICO IN THE BAY OF CAMPECHE. THIS IS LEAVING W GULF
UNDER MOSTLY FAIR WEATHER THIS EVENING. THE STATIONARY FRONT
WILL WEAKEN THROUGH FRI THEN DISSIPATE SAT. HIGH PRESSURE WILL
BUILD S FRI THROUGH MON.

CARIBBEAN SEA...
THE UPPER TROUGH OVER THE GULF OF MEXICO COMBINED WITH AN UPPER
RIDGE THAT IS ANCHORED IN THE E PACIFIC REGION EXTENDING AN AXIS
ACROSS S MEXICO INTO THE CARIBBEAN ACROSS S BELIZE TO 17N83W TO
PROVIDE DIFFLUENCE ALOFT TO GENERATE SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS N OF 20N TO OVER CUBA W OF 81W. AN UPPER RIDGE IS
ANCHORED NEAR THE BAHAMA ISLANDS COVERS THE CENTRAL CARIBBEAN
BETWEEN 70W-79W. DIFFLUENCE ALOFT IS GENERATING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS N OF 17N TO OVER CUBA BETWEEN
75W-80W INCLUDING JAMAICA. THESE UPPER RIDGES ARE INDUCING AN
INVERTED UPPER TROUGH S OF 17N TO OVER PANAMA AND COSTA RICA
BETWEEN 79W-83W. AN UPPER LOW IS E OF THE LESSER ANTILLES NEAR
15N59W COVERING THE E CARIBBEAN E OF 70W GENERATING ISOLATED
SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS N OF 15N E OF 67W
ACROSS THE LEEWARD ISLANDS. THE MONSOON TROUGH EXTENDS ACROSS
THE SW CARIBBEAN S OF 10N FROM COLOMBIA INTO THE E PACIFIC
REGION OVER PANAMA/COSTA RICA GENERATING CLUSTERS OF SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS S OF 12N BETWEEN 75W-81W. HIGH
PRESSURE WILL BUILD OFF OF THE SE COAST OF THE U.S. THROUGH MON.
TROPICAL WAVE WILL REACH THE YUCATAN PENINSULA SAT. THE SECOND
TROPICAL WAVE E OF THE LESSER ANTILLES WILL MOVE WNW INTO THE
CARIBBEAN FRI THROUGH SAT AND INTO THE N CENTRAL CARIBBEAN SAT
NIGHT.

ATLANTIC OCEAN...
THE UPPER TROUGH THAT COVERS THE E CONUS AND GULF OF MEXICO
EXTENDS OVER THE NW ATLC SUPPORTING A STATIONARY FRONT THAT AT
20/2100 UTC ENTERS THE DISCUSSION AREA NEAR 32N72W EXTENDING
ALONG 28N77W TO OVER THE FLORIDA PENINSULA NEAR MELBOURNE TO
FORT MYERS BEFORE ENTERING THE GULF OF MEXICO. SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS ARE N OF THE FRONT W OF 78W...
OVER THE FLORIDA PENINSULA...AND S OF 27N W OF 76W TO OVER CUBA
AND THROUGH THE STRAITS OF FLORIDA. AN UPPER RIDGE IS ANCHORED
NEAR THE BAHAMA ISLANDS NEAR 24N73W EXTENDING S OVER THE
CARIBBEAN AND N TO BEYOND 32N68W PROVIDING DIFFLUENCE ALOFT TO
GENERATE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 30 NM
OF LINE FROM 25N73W TO BEYOND 32N70W. A DEEP LAYERED LOW IS TO
THE E...SEE SPECIAL FEATURES ABOVE. AN UPPER LOW E OF THE LESSER
ANTILLES IS ENHANCING THE ACTIVITY ASSOCIATED WITH THE TROPICAL
WAVE E OF THE LESSER ANTILLES...SEE ABOVE. A 1018 MB HIGH IS SW
OF T.S. NADINE NEAR 25N39W. THE STATIONARY FRONT WILL GRADUALLY
DISSIPATE THROUGH FRI. HIGH PRESSURE WILL BUILD S FRI THROUGH
MON.

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

$$
PAW





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