[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 191759
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI OCT 19 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.

...TROPICAL WAVES...

TROPICAL WAVE WAS ADDED TO THE 1200 UTC ANALYSIS ALONG 11N29W TO
7N32W MOVING WEST AT 10-15 KT. THE WAVE IS LOW-AMPLITUDE AND
COINCIDES WITH A SURGE IN DEEP LAYER MOISTURE WITH MAXIMUM
VALUES NEAR THE AXIS. IT IS STILL EMBEDDED WITHIN THE CYCLONIC
FLOW PRESENT AROUND THE MONSOON TROUGH. CURRENTLY SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 9N-11N BETWEEN
27W-30W...AND FROM 3N-9N BETWEEN 31W-38W.

TROPICAL WAVE IS ALONG 19N50W TO 13N52W MOVING W-NW NEAR 15-20
KT. CYCLONIC SURFACE FLOW IS AROUND THE WAVE AS INDICATED BY AN
ASCAT SCATTEROMETER PASS FROM EARLIER TODAY. THE WAVE ALSO LIES
BENEATH A NARROW UPPER LEVEL TROUGH...WHICH IS PROVIDING A LARGE
AREA OF DIFFLUENCE ALOFT IN THE VICINITY OF THE WAVE...WHICH IS
HELPING ENHANCE CONVECTION. SCATTERED MODERATE/STRONG CONVECTION
IS WELL TO THE EAST OF THE WAVE FROM 14N-20N BETWEEN 44W-49W.
SCATTERED MODERATE CONVECTION IS FROM 16N-21N BETWEEN 49W-52W.
SIMILAR ACTIVITY IS FROM 21N-24N BETWEEN 42W-49W. IT IS LIKELY
THAT THE ACTIVITY IS CAUSED MORE BY THE UPPER LEVEL TROUGH THAN
THE WAVE.

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

THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF
GUINEA AT 10N14W CONTINUING ALONG 9N21W 6N29W 6N35W. THE ITCZ
BEGINS AT 6N35W CONTINUING ALONG 5N44W 6N54W. SCATTERED
MODERATE/STRONG CONVECTION IS FROM 10N-12N BETWEEN 18W-25W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 4N-6N
BETWEEN 17W-24W. OTHER CONVECTION NEAR THE MONSOON TROUGH IS
ASSOCIATED WITH A TROPICAL WAVE.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH COVERING THE EASTERN CONUS CONTINUES TO
SUPPORT A FRONTAL BOUNDARY IN THE GULF OF MEXICO. AS OF 1500
UTC...A COLD FRONT EXTENDS FROM NE FLORIDA NEAR 30N81W TO THE
CENTRAL GULF NEAR 27N90W WHERE IT BECOMES STATIONARY TO MEXICO
ALONG 26N96W 24N99W. ISOLATED SHOWERS ARE WITHIN 45 NM EITHER
SIDE OF THE AXIS NEAR THE COLD PORTION...AND WITHIN 100 NM OF
THE STATIONARY PORTION. A FEW ISOLATED...BUT HEAVY SHOWERS ARE
ALSO OVER PORTIONS OF SOUTH FLORIDA. DRY AIR ALOFT BETWEEN THE
UPPER TROUGH AND AN UPPER LEVEL RIDGE CENTERED OVER MEXICO IS
HELPING MAINTAIN FAIR CONDITIONS ACROSS THE REMAINDER OF THE
BASIN. THE EASTERN PORTION OF THE FRONT IS EXPECTED TO CONTINUE
TO SINK SE AND WILL EXIT THE GULF LATE TOMORROW. WINDY
CONDITIONS ARE BEHIND THE FRONT AND WILL CONTINUE TO SPREAD
ACROSS FLORIDA AS THE FRONT PASSES. SURFACE RIDGING WILL BUILD
IN BEHIND THE FRONT.

CARIBBEAN SEA...
MOSTLY DRY AIR ALOFT COVERS THE NW CARIBBEAN AROUND AN UPPER
LEVEL RIDGE EXTENDING FROM MEXICO ACROSS THE YUCATAN AND INTO
THE AREA PROVIDING FAIR CONDITIONS EXCEPT FOR A FEW LOW-TOPPED
ISOLATED SHOWERS. A WEAK SURFACE TROUGH IS ANALYZED ALONG 19N81W
TO 13N80W. A FEW ISOLATED SHOWERS ARE NEAR THE AXIS. BROAD
CYCLONIC FLOW IS ALSO ACROSS THE SW CARIBBEAN ASSOCIATED WITH
THE MONSOON TROUGH THAT HAS REMAINED FARTHER N THAN ITS USUAL
LOCATION. IT EXTENDS FROM CENTRAL NICARAGUA TO NORTHERN COLOMBIA
ALONG 13N. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN
90 NM OF THE COSTA RICAN AND NICARAGUAN COASTS. SIMILAR ACTIVITY
IS ALSO NORTH OF PANAMA FROM 9N-12N BETWEEN 76W-79W. THE EASTERN
CARIBBEAN IS ALSO COVERED IN SCATTERED TO ISOLATED
SHOWERS/THUNDERSTORMS MAINLY SOUTH OF 17N EAST OF 75W. A SURFACE
TROUGH IS HELPING ENHANCE THIS ACTIVITY ALONG 15N67W TO 12N67W.
ALOFT...AN UPPER LEVEL RIDGE IS CENTERED NEAR 16N71W WRAPPING
MOISTURE AROUND IT. EXPECT THE AREA OF MOISTURE IN THE EASTERN
CARIBBEAN TO MOVE WESTWARD OVER THE NEXT SEVERAL DAYS.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH OVER THE EASTERN CONUS IS PROVIDING A
LARGE AREA OF DIFFLUENCE ALOFT ACROSS THE WEST ATLC. IT SUPPORTS
A COLD FRONT THAT IS JUST EMERGING INTO THE AREA ALONG 32N79W TO
30N81W. SCATTERED SHOWERS/THUNDERSTORMS ARE WELL TO THE EAST...N
OF 28N BETWEEN 72W-77W...AND FROM 24N-27N BETWEEN 77W-80W ACROSS
THE WESTERN BAHAMAS. A FEW MORE ISOLATED SHOWERS/THUNDERSTORMS
ARE ACROSS THE EASTERN BAHAMAS AND N OF 28N BETWEEN 68W-73W. AN
UPPER LEVEL RIDGE COVERS THE REMAINDER OF THE WEST ATLC
EXTENDING FROM THE EASTERN CARIBBEAN ALONG 66W. A WEAK SURFACE
TROUGH IS IN THE CENTRAL ATLC...EXTENSION OF A FRONTAL BOUNDARY
NORTH OF THE AREA...ALONG 31N56W 27N59W 25N63W. SCATTERED
SHOWERS ARE WITHIN 120 NM E OF THE AXIS N OF 27N...WITH ISOLATED
SHOWERS WITHIN 90 NM EITHER SIDE OF THE AXIS ELSEWHERE. A NARROW
UPPER LEVEL TROUGH IS ALONG 51W SUPPORTING A WIDE AREA OF
SHOWERS EAST OF A TROPICAL WAVE ALONG 51W. THE ACTIVITY IS
LIKELY MORE ASSOCIATED WITH THE UPPER TROUGH THAN THE WAVE.
SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS ARE FROM 13N-24N
BETWEEN 45W-51W. THE REMAINDER OF THE E ATLC IS DOMINATED BY A
BROAD SURFACE RIDGE ANCHORED BY A 1024 MB HIGH NEAR 32N35W
PROVIDING FAIR CONDITIONS ACROSS THE E ATLC. ALOFT...AN UPPER
LEVEL RIDGE IS ALONG 35W...WHILE AN UPPER LEVEL TROUGH COVERS
THE FAR EASTERN ATLC WITH AXIS OVER NW AFRICA ALONG 8W.

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

$$
WALTON





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