[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 212355
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

A TROPICAL WAVE CONTINUES TO MOVE THROUGH THE WESTERN CARIBBEAN
EXTENDING FROM EASTERN CUBA NEAR 20N78W TO NORTH OF COLOMBIA AT
13N75W. A 1006 MB LOW IS ALONG THE WAVE AXIS NEAR 15N77W. TOTAL
PRECIPITABLE WATER IMAGERY INDICATES A LARGE AREA OF MAXIMUM
MOISTURE VALUES COVER MUCH OF THE SW AND CENTRAL CARIBBEAN. THE
SYSTEM REMAINS DISORGANIZED AT THIS TIME WITH SCATTERED
MODERATE/ISOLATED STRONG CONVECTION RANGING FROM 12N-18N BETWEEN
67W-75W...FROM 11N-18N BETWEEN 75W-80W...AND FROM 20N-22N
BETWEEN 74W-79W. ENVIRONMENT CONDITIONS REMAIN CONDUCIVE FOR
FURTHER DEVELOPMENT OF THE SYSTEM.

A TROPICAL WAVE EXTENDS FROM 24N52W TO 15N47W MOVING W-NW AT
5-10 KT. A 1011 MB LOW IS ANALYZED ALONG THE WAVE AXIS NEAR
20N51W THAT CAN BE SEEN CLEARLY IN SATELLITE IMAGERY. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS NEAR THE LOW CENTER FROM
20N-22N BETWEEN 49W-53W...AND TO THE EAST FROM 21N-24N BETWEEN
44W-49W. THE WAVE IS INTERACTING WITH AN UPPER LEVEL LOW...WHICH
IS HELPING ENHANCE THE CONVECTION TO THE EAST. SOME
STRENGTHENING IS POSSIBLE OVER THE NEXT COUPLE OF DAYS BEFORE
THE UPPER LEVEL CONDITIONS BECOME HARSHER.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 16N34W TO 11N36W MOVING WEST AT 10-15 KT.
BROAD CYCLONIC FLOW IS AROUND THE WAVE AXIS EVIDENT IN SATELLITE
IMAGERY. SCATTERED MODERATE CONVECTION IS MAINLY EMBEDDED WITHIN
THE MONSOON TROUGH AXIS FROM 7N-10N BETWEEN 36W-41W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF
GUINEA-BISSAU AT 11N16W CONTINUING ALONG 12N30W 9N40W. THE ITCZ
BEGINS AT 9N40W AND GOES TO 6N50W. SCATTERED STRONG CONVECTION
IS FROM 8N-13N BETWEEN 20W-24W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 2N-4N BETWEEN 14W-18W. SIMILAR
ACTIVITY IS FROM 10N-13N BETWEEN 43W-44W.

...DISCUSSION...

GULF OF MEXICO...
SURFACE RIDGING DOMINATES THE GULF OF MEXICO TONIGHT IN THE WAKE
OF A COLD FRONT THAT MOVED OUT OF THE BASIN YESTERDAY. LIGHT
ANTI-CYCLONIC FLOW IS AROUND THE RIDGE EXCEPT FOR SOME STRONGER
WINDS UP TO 15 KT ACROSS THE SE GULF AND ALONG THE TEXAS COAST.
CLEAR SKIES ARE PRESENT OVER THE MAJORITY OF THE AREA WITH A FEW
LOW-LEVEL CLOUDS AND POSSIBLE SHOWERS ACROSS THE FLORIDA STRAITS
AND OVER THE FAR WESTERN GULF. ALOFT...AN UPPER LEVEL RIDGE IS
MOVING ACROSS THE GULF FROM THE WEST AND CURRENTLY EXTENDS FROM
SOUTHERN MEXICO TO THE GREAT LAKES REGION. AN UPPER LEVEL TROUGH
CONTINUES TO MOVE OUT TO THE EAST. DRY AIR AND SUBSIDENCE ALSO
COVER THE AREA HELPING SUPPORT THE FAIR CONDITIONS. SURFACE
RIDGING IS EXPECTED TO REMAIN ACROSS THE GULF FOR THE NEXT
SEVERAL DAYS. WINDS WILL INCREASE OVER THE SE GULF AND FLORIDA
STRAITS AS THE PRESSURE GRADIENT INCREASES DUE TO A LOW PRESSURE
SYSTEM IN THE CARIBBEAN.

CARIBBEAN SEA...
ABUNDANT MOISTURE COVERS A GOOD PORTION OF THE CARIBBEAN
ASSOCIATED WITH A BROAD AREA OF LOW PRESSURE AROUND A TROPICAL
WAVE. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS. SCATTRED
SHOWERS/THUNDERSTORMS ALSO DOT MUCH OF CENTRAL AMERICA AS
MOISTURE FROM THE E PACIFIC WRAPS AROUND AN UPPER LEVEL RIDGE
COVERING THE MAJORITY OF THE BASIN. THE MOISTURE IS HELPING
SUPPORT ISOLATED SHOWERS IN BOTH THE NW CARIBBEAN AS WELL AS
ACROSS THE CENTRAL AND EASTERN CARIBBEAN. THE LOW PRESSURE
SYSTEM IS EXPECTED TO REMAIN SOMEWHAT STATIONARY AS IT
CONSOLIDATES BEFORE GAINING A MORE NORTH-NORTHEAST MOTION.
REGARDLESS OF DEVELOPMENT INTO TROPICAL CYCLONE...HEAVY
SHOWERS/THUNDERSTORMS WILL CONTINUE ACROSS MUCH OF THE CENTRAL
AND WESTERN CARIBBEAN...AND COULD POSE THE RISK OF FLOODING
ACROSS THE NORTHERN CARIBBEAN ISLANDS.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH COVERING THE WESTERN ATLC SUPPORTS A COLD
FRONT THAT ENTERS THE DISCUSSION AREA NEAR 32N67W TO THE CENTRAL
BAHAMAS AT 25N75W WHERE IT BECOMES STATIONARY AND BEGINS TO
DISSIPATE ACROSS WESTERN CUBA TO THE YUCATAN PENINSULA AT
22N88W. SCATTERED SHOWERS/THUNDERSTORMS ARE SE OF THE FRONT
ACROSS THE BAHAMAS AND EASTERN CUBA. ISOLATED SHOWERS ARE WITHIN
250 NM EAST OF THE REMAINDER OF THE FRONT. AN UPPER LEVEL RIDGE
COVERS THE REMAINDER OF THE W ATLC EXTENDING FROM THE EASTERN
CARIBBEAN TO NEAR 32N60W. A TROPICAL WAVE WITH AN ASSOCIATED
SURFACE LOW IS SUPPORTING AN AREA OF SHOWERS/THUNDERSTORMS IN
THE CENTRAL ATLC. SEE SPECIAL FEATURES FOR MORE DETAILS. THE
SURFACE LOW IS INTERACTING WITH AN UPPER LEVEL LOW CENTERED NEAR
21N49W. THE REMAINDER OF THE EASTERN ATLC IS COVERED BY AN UPPER
LEVEL RIDGE CENTERED OVER THE TROPICAL ATLC NEAR 11N35W. MOSTLY
FAIR WEATHER IS PRESENT EXCEPT FOR A FEW SHOWERS NEAR A SURFACE
TROUGH ALONG 23N33W TO 20N35W. AN UPPER LEVEL TROUGH TO THE
NORTH OF THE AREA ALSO SUPPORTS A COLD FRONT THAT SKIMS THE
NORTHERN BORDER OF THE DISCUSSION AREA ALONG 32N25W 30N34W
31N42W. ISOLATED SHOWERS ARE WITHIN 30 NM EITHER SIDE OF THE
AXIS.

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

$$
WALTON





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