[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 161745
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN OCT 16 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...
A BROAD AREA OF LOW PRESSURE CONTINUES TO COVER THE NW
CARIBBEAN...SE GULF OF MEXICO...AND SRN MEXICO CONCENTRATED
AROUND A 1004 MB SURFACE LOW LOCATED ALONG THE MONSOON TROUGH
OVER BELIZE NEAR 19N88W. THIS AREA OF LOW PRESSURE LIES
UNDERNEATH AN AREA OF DIFFLUENCE ALOFT AROUND THE WRN SIDE OF AN
UPPER RIDGE CENTERED OVER THE SE BAHAMAS. THIS PATTERN IS
SUPPORTING NUMEROUS MODERATE/STRONG CONVECTION FROM 16N-19N
BETWEEN 82W-84W...AND FROM 19N-23N BETWEEN 78W-89W INCLUDING WRN
CUBA...BELIZE...AND THE NE YUCATAN PENINSULA. FURTHER
DEVELOPMENT OF THIS SYSTEM IS POSSIBLE AS THE LOW DRIFTS NW.
REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY RAINFALL IS POSSIBLE
OVER THE YUCATAN PENINSULA...NW CARIBBEAN...AND SE GULF. IN
ADDITION...GUSTY WINDS UP TO GALE FORCE ARE ALREADY OCCURRING S
OF 25N BETWEEN 85W-90W.

...TROPICAL WAVES...

TROPICAL WAVE IN THE CENTRAL TRPCL ATLC EXTENDS FROM 15N38W
THROUGH A 1009 MB LOW NEAR 11N39W TO 7N40W MOVING W 15-20 KT.
SATELLITE IMAGERY INDICATES LOW LEVEL CYCLONIC FLOW AROUND THE
WAVE AXIS CONFIRMED BY AN ASCAT SCATTEROMETER PASS FROM AROUND
1144 UTC. THE WAVE ALSO LIES ON THE WRN SIDE OF A MAXIMUM IN
DEEP LAYER MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY.
A CLUSTER OF NUMEROUS STRONG CONVECTION IS FROM 9N-12N BETWEEN
35W-38W...WITH SCATTERED MODERATE/STRONG CONVECTION ELSEWHERE
FROM 6N-14N BETWEEN 32W-40W.

TROPICAL WAVE IN THE WRN TRPCL ATLC IS ALONG 17N57W TO 10N60W
MOVING W NEAR 15 KT. LOW LEVEL CYCLONIC FLOW IS EVIDENT IN BOTH
SATELLITE IMAGERY AS WELL AS FROM A WINDSAT SCATTEROMETER PASS
FROM 0956 UTC. THE WAVE IS ALSO EMBEDDED WITHIN A SURGE OF DEEP
LAYER MOISTURE INDICATED BY TOTAL PRECIPITABLE WATER IMAGERY.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION 12N-14N BETWEEN
55W-60W.

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

THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL
ATLC ALONG 16N16W 9N20W 8N27W. THE ITCZ CONTINUES FROM 8N27W TO
9N36W...AND PICKS UP ON THE OTHER SIDE OF A TROPICAL WAVE ALONG
6N42W TO 7N54W. ISOLATED MODERATE/STRONG CONVECTION IS WITHIN
220 NM N OF THE AXIS...AND 300 NM S OF THE AXIS BETWEEN THE
AFRICAN COAST AND 29W. NUMEROUS MODERATE/STRONG CONVECTION IS
WITHIN 90 NM EITHER SIDE OF THE AXIS BETWEEN 41W-45W. ISOLATED
MODERATE CONVECTION IS N OF THE AXIS FROM 9N-13N BETWEEN 50W-56W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD LONGWAVE UPPER TROUGH IS MOVING OVER THE NW ATLC
SUPPORTING A STATIONARY FRONT THAT EXTENDS ACROSS S FLORIDA
ALONG 26N TO 86W. MOIST SWLY FLOW ALOFT IS DRAWING MOISTURE
ACROSS THE SE GULF SUPPORTING OVERCAST SKIES AND SCATTERED
SHOWERS S OF 27N E OF 90W. MOST OF THE MOISTURE IN THIS AREA IS
ASSOCIATED WITH AN AREA OF LOW PRESSURE TO THE S OVER THE NW
CARIBBEAN AND YUCATAN PENINSULA WHICH IS SUPPORTING NUMEROUS
SHOWERS S OF 24N. A FEW SCATTERED SHOWERS ARE ALSO POPPING UP
OVER THE SW GULF IN THE BAY OF CAMPECHE. GALE FORCE WINDS ARE
NOTED S OF 25S BETWEEN 85W-90W. SEE SPECIAL FEATURES FOR MORE
DETAILS ON THIS DISTURBANCE. HIGH SURFACE PRESSURE IS BUILDING
INTO THE NRN GULF AROUND A 1018 MB HIGH OVER SRN TEXAS AND A
1022 MB HIGH OVER GEORGIA. WATER VAPOR IMAGERY INDICATES DRY AIR
AND SUBSIDENCE ACROSS THE NRN AND NW GULF PROVIDING MOSTLY FAIR
WEATHER. EXPECT MOIST CONDITIONS TO REMAIN ACROSS THE SE GULF
OVER THE NEXT SEVERAL DAYS AS THE LOW PRESSURE SYSTEM IN THE NW
CARIBBEAN DRIFTS NW.

CARIBBEAN SEA...
SIGNIFICANT MOISTURE LIES ACROSS THE NW CARIBBEAN ASSOCIATED
WITH BROAD LOW PRESSURE CENTERED AROUND A 1004 MB LOW NEAR
19N88W. THIS LOW IS ALONG THE MONSOON TROUGH THAT EXTENDS ACROSS
SRN MEXICO TO THE SRN YUCATAN AND INTO THE NW CARIBBEAN ALONG
20N TO 80W. THIS SYSTEM IS CURRENTLY PRODUCING SIGNIFICANT
RAINFALL OVER WRN CUBA AND THE NRN YUCATAN. THE HIGH MOISTURE
VALUES EXTEND SWD INTO THE SW CARIBBEAN WHERE SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS ARE S OF 14N BETWEEN 77W-84W.
ALOFT...AN UPPER LEVEL RIDGE COVERS THE MAJORITY OF THE BASIN.
WHILE THE WRN CARIBBEAN IS WET...THE UPPER RIDGE IS ADVECTING
DRY AIR INTO THE ERN AND CENTRAL CARIBBEAN FROM THE CENTRAL ATLC
PROVIDING MOSTLY FAIR CONDITIONS. A TROPICAL WAVE E OF THE
LESSER ANTILLES WILL BEGIN TO BRING SHOWERS TO THE ISLANDS SOON
AS THE WAVE CONTINUES TO MOVE WWD. EXPECT VERY MOIST CONDITIONS
TO REMAIN OVER THE NW CARIBBEAN ESPECIALLY THE YUCATAN PENINSULA
AND WRN CUBA.

ATLANTIC OCEAN...
A BROAD UPPER TROUGH OVER THE NW ATLC SUPPORTS A STATIONARY
FRONT THAT EXTENDS ALONG 32N64W 27N72W ACROSS THE NW BAHAMAS TO
FLORIDA NEAR 26N80W. SCATTERED SHOWERS ARE WITHIN 60 NM OF THE
FRONT. AN UPPER LEVEL RIDGE IS CENTERED NEAR 22N73W DRAWING
MOISTURE FROM THE NW CARIBBEAN DISTURBANCE TOWARDS THE NE
SUPPORTING UPPER LEVEL CLOUDS. THE UPPER RIDGE SUPPORTS A
SURFACE RIDGE ANCHORED BY A 1031 MB HIGH NEAR 44N29W WHICH
DOMINATES MUCH OF THE CENTRAL AND ERN ATLC. A SECOND UPPER RIDGE
COVERS THE TROPICAL ATLC CENTERED NEAR 12N26W. EXPECT THE
STATIONARY FRONT TO GRADUALLY DISSIPATE WHILE SURFACE RIDGING
BUILDS INTO THE WRN ATLC. A WEAK SURFACE LOW N OF THE DISCUSSION
AREA IN THE CENTRAL ATLC WILL ALSO DIP SOUTH INTO THE AREA.

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

$$
WALTON







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