[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211753
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN OCT 21 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

TROPICAL WAVE EXTENDS FROM 14N47W TO 22N51W MOVING W-NW AT 5-10
KT. A 1012 MB LOW IS CENTERED ALONG THE WAVE AXIS NEAR 19N50W AS
NOTED ON METEOSAT-9 VISIBLE SATELLITE IMAGERY WITH ISOLATED
MODERATE CONVECTION OCCURRING FROM 19N-25N BETWEEN 48W-54W. THIS
CONVECTION IS LIKELY ENHANCED BY A MIDDLE TO UPPER LEVEL LOW
CENTERED NEAR 20N49W. THIS SYSTEM HAS A MEDIUM CHANCE OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

TROPICAL WAVE EXTENDS FROM 11N74W TO 20N76W MOVING W AT 5 KT. A
1008 MB LOW IS ANALYZED ALONG THE WAVE AXIS NEAR 15N76W WITH
BROAD LOW-LEVEL CYCLONIC FLOW LOCATED ACROSS MUCH OF THE WESTERN
CARIBBEAN. TOTAL PRECIPITABLE WATER IMAGERY ALSO INDICATES
MAXIMUM VALUES OF DEEP LAYER MOISTURE ACROSS THE CENTRAL
CARIBBEAN BETWEEN 70W-80W. UNORGANIZED SCATTERED MODERATE AND
ISOLATED STRONG CONVECTION ACCOMPANIES THE WAVE OVER A LARGE
AREA FROM 12N-18N BETWEEN 70W-77W. A WEAK UPPER LEVEL
ANTICYCLONIC CIRCULATION IS CENTERED OVER THE TROPICAL WAVE NEAR
16N73W WITH ENVIRONMENTAL CONDITIONS CONTINUING TO BECOME MORE
FAVORABLE FOR DEVELOPMENT DURING THE NEXT DAY OR TWO AS THE
DISTURBANCE MOVES SLOWLY WESTWARD. THIS SYSTEM HAS A HIGH CHANCE
OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

...TROPICAL WAVES...

SEE SPECIAL FEATURES SECTION ABOVE FOR MORE DETAILS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 08N13W TO
11N20W TO 11N33W TO 09N40W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 09N40W TO 05N50W. SCATTERED MODERATE
CONVECTION IS FROM 02N-07N BETWEEN 09W-15W...FROM 04N-13N
BETWEEN 18W-29W...AND FROM 08N-11N BETWEEN 35W-45W.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYERED LOW IS CENTERED OVER EASTERN CANADA AND PROVIDES
MIDDLE TO UPPER LEVEL TROUGHING ALONG THE EASTERN U.S. SEABOARD.
THE TROUGH AXIS DIPS SOUTHWARD INTO THE SE GULF WITH A BASE OVER
THE YUCATAN CHANNEL AND WATER VAPOR IMAGERY INDICATING VERY DRY
AND STABLE NW FLOW ALOFT BETWEEN THE TROUGHING AND AN UPPER
LEVEL RIDGE OVER MEXICO AND THE CENTRAL PLAINS. WHILE A
LINGERING DISSIPATING STATIONARY FRONT IS ANALYZED FROM THE
STRAITS OF FLORIDA TO NORTH OF THE YUCATAN PENINSULA NEAR
22N90W...THE ENTIRE GULF IS UNDER THE INFLUENCE OF A SURFACE
RIDGE ANCHORED BY A 1022 MB HIGH CENTERED OVER NORTHERN ALABAMA
NEAR 34N86W. THE RIDGE AXIS EXTENDS FROM THE HIGH S-SW TO THE SW
GULF NEAR 20N96W AND IS EXPECTED TO MAINTAIN CLEAR SKIES AND
FAIR WEATHER CONDITIONS THROUGH LATE MONDAY.

CARIBBEAN SEA...
WITH AN UPPER LEVEL TROUGH OVER THE EASTERN U.S SEABOARD DIPPING
SOUTHWARD OVER PORTIONS OF THE SW NORTH ATLC AND THE SE GULF OF
MEXICO...THE WESTERN CARIBBEAN FINDS ITSELF SOUTH OF THE BASE OF
THIS TROUGH AND BENEATH A BROAD AREA OF OVERALL DIFFLUENCE AND
RELATIVELY UNSETTLED WEATHER. THE MAIN FEATURE IMPACTING THE
CENTRAL AND WESTERN CARIBBEAN IS THE TROPICAL WAVE AND
ASSOCIATED AREA OF LOW PRESSURE ALONG 76W AND IN THE VICINITY OF
15N76W. SCATTERED SHOWERS AND WIDELY SCATTERED STRONG TSTMS ARE
OCCURRING FROM 12N-18N BETWEEN 70W-80W. TO THE WEST OF THIS
TROPICAL WAVE...THE UPPER LEVEL DIFFLUENCE ALONG WITH PERSISTENT
NORTHEASTERLY WINDS ARE PROVIDING FOR LOW-LEVEL MOISTURE
CONVERGENCE ALONG A SURFACE TROUGH ANALYZED ALONG 13N83W TO
16N84W TO 19N88W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE
OCCURRING FROM 13N-21N BETWEEN 80W-88W...INCLUDING PORTIONS OF
THE GULF OF HONDURAS. THE DEVELOPMENT OF ORGANIZED DEEP
CONVECTION AND THE FORMATION OF A CONSOLIDATED LOW LEVEL
CIRCULATION CENTER WILL BE SLOW TO OCCUR OVER THE NEXT FEW DAYS
AS MANY OF THE GLOBAL MODELS SUGGEST A RATHER BROAD AREA OF LOW
PRESSURE ACROSS THE CENTRAL AND WESTERN CARIBBEAN PERSISTING
INTO MID-WEEK. IN THE MEANTIME...HEAVY RAINS FROM THIS SYSTEM
ARE LIKELY TO CONTINUE OVER JAMAICA...HISPANIOLA...AND EASTERN
CUBA OVER THE NEXT SEVERAL DAYS AND COULD PRODUCE LIFE-
THREATENING FLASH FLOODS AND MUD SLIDES...ESPECIALLY IN AREAS OF
HIGH TERRAIN.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL TROUGH IS OVER THE EASTERN U.S SEABOARD
THAT SUPPORTS A COLD FRONT EXTENDING INTO THE DISCUSSION AREA
NEAR 32N70W SW ACROSS THE NW BAHAMAS TO 25N80W IN THE FLORIDA
STRAITS WHERE IT BECOMES STATIONARY INTO THE SE GULF OF MEXICO W
OF 80W. WATER VAPOR IMAGERY INDICATES SOUTHWESTERLY FLOW ALOFT
NEAR AND EAST OF THE TROUGH AXIS IS PROVIDING FOR SUFFICIENT
DIFFLUENCE TO FURTHER SUPPORT ISOLATED SHOWERS AND TSTMS
OCCURRING WITHIN 360 NM EAST OF THE FRONT. FARTHER EAST...MOST
OF THE REMAINDER OF THE CENTRAL AND EASTERN ATLC...OUTSIDE OF
THE TROPICAL WAVE MENTIONED ABOVE IN THE SPECIAL FEATURES
SECTION...IS INFLUENCED BY A SURFACE RIDGE THAT IS STRETCHED
THIN IN AN EAST-WEST ORIENTATION AND ANCHORED BY A 1017 MB HIGH
CENTERED NEAR 30N14W AND A 1023 MB HIGH CENTERED NORTH OF THE
AREA NEAR 41N50W. BETWEEN THESE TWO HIGH CENTERS...A COLD FRONT
IS LOCATED ALONG 31N/32N BETWEEN 28W-45W AND IS EXPECTED TO
CONTINUE A GRADUAL SOUTHWARD DRIFT WHILE DISSIPATING AS AN UPPER
LEVEL SHORTWAVE TROUGH CURRENTLY NEAR 30N30W PROGRESSES E-SE
OVER THE NE ATLC DISCUSSION WATERS DURING THE NEXT 24 TO 36
HOURS.

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

$$
HUFFMAN



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