[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171156
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON OCT 17 2011

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1145 UTC.

...SPECIAL FEATURES...
A BROAD AREA OF LOW PRESSURE COVERS THE NW CARIBBEAN...SE GULF
OF MEXICO AND THE YUCATAN PENINSULA WITH A 1003 MB SURFACE LOW
CENTERED ALONG THE NE COAST OF THE YUCATAN PENINSULA NEAR 22N87W
AT 17/0900 UTC. SCATTERED/NUMEROUS STRONG CONVECTION IS FROM
21N-24W BETWEEN 83W-87W INCLUDING A PORTION OF W CUBA. SCATTERED
TO HEAVY RAINS COVER THE REMAINDER OF THE AREA S OF LINE FROM
TAMPA FLORIDA ALONG 25N88W TO OVER THE SW GULF AND S MEXICO NEAR
20N96W. THIS SYSTEM CONTINUES TO PRODUCE STRONG GUSTY WINDS OVER
THE SOUTHEASTERN GULF OF MEXICO. UPPER-LEVEL WINDS ARE EXPECTED
TO BE MARGINALLY CONDUCIVE FOR DEVELOPMENT DURING THE NEXT DAY
OR SO BEFORE BECOMING UNFAVORABLE AFTER THAT. ALTHOUGH THIS
LARGE DISTURBANCE IS INTERACTING WITH THE YUCATAN PENINSULA...
SOME GRADUAL DEVELOPMENT IS STILL POSSIBLE AS THE LOW MOVES
TOWARD THE N AT 4-9 KT. THIS SYSTEM HAS A HIGH CHANCE OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. REGARDLESS
OF DEVELOPMENT...LOCALLY HEAVY RAINFALL AND GUSTY WINDS ARE
EXPECTED OVER THE YUCATAN PENINSULA...WESTERN CUBA...THE FLORIDA
KEYS...AND SOUTH FLORIDA DURING THE NEXT COUPLE OF DAYS. AN AIR
FORCE RESERVE RECONNAISSANCE AIRCRAFT IS SCHEDULED TO
INVESTIGATE THE LOW THIS AFTERNOON.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED OFF THE COAST OF W AFRICA FROM 17N20W
TO 9N22W MOVING W AT 10-15 KT. WAVE IS WELL DEFINED IN THE
UPPER LEVEL SATELLITE WINDS AND IS EMBEDDED WITHIN A SLIGHT
MOISTURE SURGE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER
IMAGERY. CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION ARE
FROM 8N-14N BETWEEN 20W-25W.

TROPICAL WAVE IS ANALYZED IN THE CENTRAL TROPICAL ATLC FROM
15N39W TO 7N43W MOVING W 10-15 KT. WAVE IS WELL DEFINED IN THE
UPPER LEVEL SATELLITE WINDS AND IS EMBEDDED WITHIN A BROAD AREA
OF MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER IMAGERY.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
FROM 7N-14N BETWEEN 36W AND THE WAVE AXIS.

TROPICAL WAVE IS ANALYZED OVER THE LESSER ANTILLES FROM 17N62W
TO 10N63W MOVING 10-15 KT. WAVE IS WELL DEFINED IN THE UPPER
LEVEL SATELLITE WINDS AND THE LOW LEVEL CLOUD PATTERN ON
SATELLITE IMAGERY. WAVE IS ALSO EMBEDDED WITHIN A SLIGHT
MOISTURE SURGE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER
IMAGERY BUT DUE TO STRONG SUBSIDENCE AND DRY STABLE...THERE IS
NO ASSOCIATED DEEP CONVECTION. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE W OF THE WAVE S OF 13N TO THE COAST OF
VENEZUELA BETWEEN 65W-68W.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA TO THE COAST NEAR
17N16W THEN RESUMES NEAR 11N24W 10N33W TO 8N41W. THE ITCZ IS
DISRUPTED BY THE PRESENCE OF THE TROPICAL WAVES. CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 10N-16N
BETWEEN 25W-36W. SMALL CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION DOT THE AREA FROM 4N-7N E OF 16W TO THE COAST
OF AFRICA AND FROM 4N-7N BETWEEN 24W-28W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER TROUGH OVER THE NW ATLC CONTINUES TO SUPPORT A QUASI-
STATIONARY FRONT THAT EXTENDS THROUGH THE W ATLC THEN DISSIPATES
ACROSS FLORIDA INTO THE GULF NEAR LAKE OKEECHOBEE TO 26N85W
FURTHER ENHANCING THE ACTIVITY ASSOCIATED WITH THE SPECIAL
FEATURES ABOVE. SURFACE RIDGE IS BEHIND THE FRONT ANCHORED BY A
1018 MB HIGH OVER SW GEORGIA AND A 1019 MB HIGH IN THE W ATLC
NEAR 31N73W. AN UPPER RIDGE IS ANCHORED IN THE YUCATAN CHANNEL
COVERING THE SE GULF AND PRODUCING A SHEAR AXIS ACROSS THE GULF
THAT EXTENDS FROM FLORIDA NEAR APALACHEE BAY TO NEAR TAMPICO
MEXICO. NW OF THIS SHEAR AXIS ARE STRONG SUBSIDENCE AND DRY
STABLE AIR ALOFT WITH CLEAR SKIES. TO THE SE...MOIST TROPICAL
AIR IS BEING ADVECTED OVER THE GULF AND THE FLORIDA PENINSULA
ENHANCING THE ACTIVITY ASSOCIATED WITH THE SPECIAL FEATURES
ABOVE. THE STATIONARY FRONT WILL GRADUALLY DISSIPATE THROUGH
LATE TONIGHT. THE LOW IN SPECIAL FEATURES ABOVE IS FORECAST TO
BEGIN TO TRACK NE TONIGHT TO NEAR 28N83W BY LATE TUE NIGHT...
POSSIBLY AS A TROPICAL CYCLONE...BEFORE MOVING ACROSS N CENTRAL
FLORIDA. A TROUGH WILL TRAIL SW FROM THE LOW IN ADVANCE OF A
STRONG COLD FRONT THAT WILL ENTER THE NW WATERS EARLY TUE. THIS
FRONT WILL MOVE QUICKLY SE ACROSS THE AREA TO SE OF THE GULF WED
EVENING. HIGH PRESSURE WILL RE-BUILD OVER THE GULF IN THE WAKE
OF THE FRONT THROUGH FRI.

CARIBBEAN SEA...
AN UPPER RIDGE IS ANCHORED OVER THE YUCATAN CHANNEL NEAR 22N85W
AND COVERS THE MOST OF THE CARIBBEAN WITH A RIDGE AXIS EXTENDING
NE TO OVER THE W ATLC. THIS UPPER RIDGE IS PROVIDING A DIFFLUENT
ENVIRONMENT TO ENHANCE THE ACTIVITY ASSOCIATED WITH THE SPECIAL
FEATURES ABOVE. EASTERLY SURFACE FLOW COMBINED WITH THE EASTERLY
FLOW ALOFT OVER THE SW CARIBBEAN IS GENERATING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS S OF 11N BETWEEN COLOMBIA AND
COSTA RICA WITH SCATTERED SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS FROM 11N-13N W OF 73W TO INLAND OVER CENTRAL
AMERICA. THE LOW IN THE SPECIAL FEATURES WILL MOVE SLOWLY
NORTHWARD THROUGH TUE MORNING. THE TROPICAL WAVE OVER THE E
CARIBBEAN WILL MOVE ACROSS THE E CARIBBEAN THROUGH TUE WHILE
WEAKENING. A COLD FRONT WILL PUSH INTO THE NW CARIBBEAN WED
REACHING FROM CENTRAL CUBA TO E HONDURAS BY LATE THU WHERE IT
WILL STALL.

ATLANTIC OCEAN...
A BROAD UPPER TROUGH COVERS THE NW ATLC N OF THE DISCUSSION AREA
AND SUPPORTING A QUASI-STATIONARY FRONT THAT ENTERS THE REGION
NEAR 32N62W EXTENDING ALONG 27N74W THEN W ACROSS THE N BAHAMA
ISLANDS AND FLORIDA NEAR LAKE OKEECHOBEE DISSIPATING INTO THE
GULF OF MEXICO. AN UPPER RIDGE AXIS EXTENDS FROM THE YUCATAN
CHANNEL NEAR 22N85W THROUGH THE STRAITS OF FLORIDA AND THE
BAHAMAS ALONG 26N70W TO BEYOND 32N55W PROVIDING A DIFFLUENT
ENVIRONMENT TO ENHANCE SCATTERED SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS N OF THE UPPER RIDGE AXIS TO 30N. A NARROWING
UPPER TROUGH COVERS THE CENTRAL ATLC EXTENDING FROM AN UPPER LOW
32N33W THROUGH A SECOND WEAKENING UPPER LOW NEAR 20N52W
NARROWING FURTHER INTO THE W TROPICAL ATLC AND E CARIBBEAN
ACROSS THE WINDWARD ISLANDS TO THE COAST OF VENEZUELA NEAR
10N68W. A WEAK SURFACE RIDGE COVERS THE E AND CENTRAL ATLC
BETWEEN 23N-30N E OF 60W. THE WEAK STATIONARY FRONT WILL
GRADUALLY DISSIPATE THROUGH TUE MORNING AS A SURFACE RIDGE
BUILDS ALONG 31N. THIS RIDGE WILL THEN SHIFT NE AND WEAKEN TUE
IN RESPONSE TO A COLD FRONT THAT MOVES OFF THE NE FLORIDA COAST
EARLY WED. THE LOW IN THE SPECIAL FEATURES WILL TRACK NE AS A
POSSIBLE TROPICAL CYCLONE THEN ACROSS NE FLORIDA...AND POSSIBLY
OVER THE FAR NW WATERS TUE NIGHT. THE FRONT WILL REACH FROM
31N74W TO CENTRAL CUBA BY EARLY THU THEN WEAKEN AND BECOME
STATIONARY FROM NEAR 31N70W TO CENTRAL CUBA FRI.

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

$$
PAW




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