[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 221749
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON OCT 22 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 DEPRESSION EIGHTEEN IS CENTERED NEAR 13.5N 78.5W AT
22/1800 UTC OR ABOUT 280 NM SSW OF KINGSTON JAMAICA REMAINING
STATIONARY. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB.
MAXIMUM SUSTAINED MAXIMUM WIND SPEED IS 25 KT WITH GUSTS TO 35
KT. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM
09N-18N BETWEEN 75W-80W...AND FROM 11N-17N BETWEEN 65W-74W. SEE
LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS
MIATCPAT3/WTNT33 KNHC AND THE FULL FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS.

A 1009 MB LOW IS CENTERED NEAR 21N52W MOVING N-NW AT 5-10 KT.
THE SURFACE LOW IS NEARLY COLLOCATED WITH A MIDDLE TO UPPER
LEVEL LOW CENTERED NEAR 22N50W THAT CONTINUES TO PRODUCE
SCATTERED MODERATE CONVECTION FROM 19N-23N BETWEEN 49W-53W AND
ISOLATED MODERATE CONVECTION FROM 23N-26N BETWEEN 49W-54W. A
SURFACE TROUGH EXTENDS FROM THE LOW TO 26N50W. THIS SYSTEM HAS A
HIGH CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48
HOURS.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 08N23W TO 14N22W MOVING W AT 10 KT.
THE WAVE REMAINS LARGELY EMBEDDED WITHIN THE MONSOON TROUGH AND
EXHIBITS A FAIRLY LOW-AMPLITUDE. TOTAL PRECIPITABLE WATER VALUES
ARE HIGHER IN THE VICINITY OF THE WAVE WITH ISOLATED MODERATE
CONVECTION FROM 08N-12N BETWEEN 20W-23W MOSTLY TO THE WEST OF
THE WAVE AXIS WHERE LOW-LEVEL CONVERGENCE IS MAXIMIZED.

TROPICAL WAVE EXTENDS FROM 10N37W TO 16N36W MOVING W AT 5 TO 10
KT. THE WAVE REMAINS EMBEDDED WITHIN THE MONSOON TROUGH AND
CONTINUES TO BE A VERY WEAK AREA OF ENERGY WITH LOW-AMPLITUDE.
SCATTERED MODERATE CONVECTION IS OCCURRING FROM 10N-12N BETWEEN
36W-39W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 07N12W TO
08N16W TO 10N26W TO 09N40W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 09N40W TO 09N49W TO 06N54W. SCATTERED MODERATE
CONVECTION IS FROM 02N-08N BETWEEN 09W-17W. ISOLATED MODERATE
CONVECTION IS FROM 07N-11N BETWEEN 29W-35W.

...DISCUSSION...

GULF OF MEXICO...
A MIDDLE TO UPPER LEVEL RIDGE IS OVER THE GULF WITH AXIS
EXTENDING FROM CENTRAL MEXICO NEAR 20N100W TO BEYOND CENTRAL
ALABAMA NEAR 33N87W. WEST-NORTHWESTERLY WINDS ALOFT DOMINATE
OVER THE GULF AS WATER VAPOR IMAGERY INDICATES A VERY DRY AND
STABLE AIRMASS PROVIDING CLEAR SKIES AND FAIR WEATHER THIS
AFTERNOON. A SURFACE RIDGE FURTHER SUPPORTS THE FAIR WEATHER
ANCHORED BY A 1026 MB HIGH CENTERED OVER THE MID-ATLC STATES.
THE RIDGE IS FORECAST TO REMAIN ACROSS THE GULF THROUGH THE WEEK
WITH MOSTLY EAST-SOUTHEASTERLY WINDS EXPECTED OVER THE NEXT 24
TO 36 HOURS.

CARIBBEAN SEA...
A VERY BROAD AREA OF LOWER SURFACE PRESSURES ARE ACROSS THE
CARIBBEAN THIS AFTERNOON WITH MOST OF THE FOCUS ON TROPICAL
DEPRESSION EIGHTEEN CENTERED IN THE WESTERN PORTION OF THE
BASIN. SCATTERED TO NUMEROUS SHOWERS AND SCATTERED STRONG TSTMS
ARE OCCURRING FROM 09N-18N BETWEEN 75W-80W NEAR THE SYSTEM
CENTER...AND FROM 11N-17N BETWEEN 65W-74W WELL TO THE EAST OF
THE SYSTEM CENTER. WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL
TROUGH AXIS EXTENDS FROM 25N80W TO 17N86W AND THIS TROUGH IS
EXPECTED TO DEVELOP AND HELP GUIDE T.D. EIGHTEEN ON A NORTH-
NORTHEASTERLY TRACK BEYOND TUESDAY. AS T.D. EIGHTEEN BEGINS ITS
NORTHWARD TRACK...THE PRIMARY IMPACTS WILL REMAIN AN OVERALL
LARGE WIND FIELD AND THE INCREASED PROBABILITY OF HEAVY RAINFALL
OVER JAMAICA...EASTERN CUBA...AND HISPANIOLA. THIS WILL RESULT
IN THE POSSIBILITY OF LIFE-THREATENING FLASH FLOODS AND
MUDSLIDES...ESPECIALLY IN AREAS OF HIGHER TERRAIN.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL TROUGH IS NOTED ACROSS THE WESTERN ATLC
N OF 30N BETWEEN 55W-70W THAT SUPPORTS A COLD FRONT ANALYZED
INTO THE DISCUSSION AREA NEAR 32N61W. THE COLD FRONT EXTENDS SW
TO 27N68W AND BECOMES A DISSIPATING STATIONARY FRONT TO THE
CENTRAL BAHAMAS NEAR 24N76W TO WESTERN CUBA NEAR 23N81W.
SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING WITHIN 120 NM
EITHER SIDE OF A LINE FROM 32N59W TO 26N63W TO 26N70W AND FROM
20N-27N BETWEEN 70W-76W. THE COLD FRONT IS FORECAST TO CONTINUE
DRIFTING E-NE OVER THE NEXT 24 TO 36 HOURS WHILE THE STATIONARY
PORTION DISSIPATES FULLY AND IS REPLACED BY A SURFACE RIDGE
ANCHORED BY A 1026 MB HIGH CURRENTLY CENTERED OVER THE MID-ATLC
STATES. THE HIGH PRESSURE AREA IS FORECAST TO REMAIN NEARLY
STATIONARY THROUGH WEDNESDAY UNTIL TROPICAL DEPRESSION EIGHTEEN
BEGINS TO TRACK ITSELF INTO SOUTHERN PORTIONS OF THE SW NORTH
ATLC WATERS. THEREAFTER...A STRONG PRESSURE GRADIENT WILL EXIST
OVER MUCH OF THE SW NORTH ATLC WITH STRONG E-NE WINDS FORECAST.
ELSEWHERE OVER THE CENTRAL ATLC...THE SPECIAL FEATURES LOW
CENTERED NEAR 21N51W CONTINUES TO IMPACT A RELATIVELY SMALL AREA
COVERING THE AREA FROM 19N-26N BETWEEN 46W-55W WHILE A 1020 MB
HIGH IS CENTERED NORTH OF THIS LOW NEAR 34N45W. FINALLY OVER
NORTHEASTERN PORTIONS OF THE ATLC DISCUSSION AREA...A DEEP
LAYERED MIDDLE TO UPPER LEVEL LOW IS CENTERED NEAR 43N27W AND
SUPPORTS A DISSIPATING COLD FRONT ANALYZED FROM 32N23W TO
28N36W. ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE
OF THE FRONT.

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

$$
HUFFMAN




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