[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 131113 CCA
TWDAT

TROPICAL WEATHER DISCUSSION...COR
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON OCT 13 2008

...CORRECTED TIME TO 805 AM...

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1015 UTC.

...SPECIAL FEATURES...
THE CENTER OF TROPICAL STORM NANA AT 13/0300 UTC IS NEAR
16.6N 39.3W...MOVING WEST-NORTHWEST OR 285 DEGREES 6 KT.
THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. THE
MAXIMUM SUSTAINED WIND SPEEDS ARE 35 KT WITH GUSTS TO 45 KT.
PLEASE READ THE LATEST NHC PUBLIC ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPAT4/WTNT34 KNHC AND THE FULL FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS.
TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 100 NM AWAY
FROM THE CENTER. SCATTERED STRONG SHOWERS AND THUNDERSTORMS ARE
FROM 14N TO 17N BETWEEN 35W AND 38W. NANA IS EXPECTED TO WEAKEN
DURING THE NEXT DAY OR SO...AND FORECAST TO BECOME A TROPICAL
DEPRESSION LATER TODAY/EARLY TOMORROW.

A 1008 MB CARIBBEAN SEA LOW PRESSURE CENTER IS NEAR 16N69W.
IT IS POSSIBLE THAT THIS LOW CENTER MAY BECOME A TROPICAL
CYCLONE DURING THE NEXT 24 HOURS OR SO. NUMEROUS STRONG
SHOWERS AND THUNDERSTORMS ARE FROM 11N TO 16N BETWEEN 63W
AND 69W. THIS SYSTEM IS EXPECTED TO RESULT IN HEAVY RAINS
IN PUERTO RICO AND PARTS OF THE LEEWARD ISLANDS DURING THE
NEXT FEW DAYS. THESE RAINS MAY CAUSE FLASH FLOODS IN SOME AREAS.

...TROPICAL WAVES...
AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 20N49W 10N48W MOVING
WEST 10 TO 15 KT. IT IS NOT READILY APPARENT THAT ANY CONVECTIVE
PRECIPITATION IS ACCOMPANYING THIS WAVE.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 58W/59W SOUTH OF 20N
MOVING WEST 10 KT TO 15 KT. ISOLATED TO WIDELY SCATTERED
MODERATE SHOWERS ARE FROM 17N TO 21N BETWEEN 55W AND 60W.
A MIDDLE TO UPPER LEVEL IS NEAR 21N61W.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 72W/73W SOUTH OF 20N
MOVING WEST 10 TO 15 KT. THE WAVE EXTENDS FROM HAITI TO THE
COLOMBIA/VENEZUELA BORDER. UPPER LEVEL SOUTHWESTERLY WIND FLOW
IS MOVING ON TOP OF THE AREA OF THIS WAVE. IT IS NOT EASY TO
KNOW IF ANY OF THE CELLS OF SHOWERS AND POSSIBLE THUNDERSTORMS
TO THE NORTH OF 6N IN COLOMBIA AND EXTREME NORTHWESTERN
VENEZUELA BETWEEN 70W AND 77W IS RELATED TO THIS WAVE.

...THE ITCZ...
12N16W 5N30W 9N43W 10N47W 10N57W. STRONG SHOWERS AND
THUNDERSTORMS ARE FROM 10N TO 12N BETWEEN 49W AND 52W.
SCATTERED MODERATE SHOWERS TO ISOLATED STRONG THUNDERSTORMS
ARE SOUTH OF 10N BETWEEN 29W AND 38W. ISOLATED MODERATE
SHOWERS TO POSSIBLE THUNDERSTORMS ELSEWHERE FROM 3N TO 10N
BETWEEN 10W AND 25W. A 1010 MB LOW PRESSURE CENTER IS NEAR
13N42W. SCATTERED STRONG THUNDERSTORMS ARE FROM 12N TO 13N
BETWEEN 41W AND 42W. SCATTERED MODERATE SHOWERS TO ISOLATED
STRONG THUNDERSTORMS ARE WITHIN 15 NM ON EITHER SIDE OF 13N40W
10N43W...AND FROM 7N TO 10N BETWEEN 43W AND 50W.

...DISCUSSION...

THE GULF OF MEXICO...
MIDDLE TO UPPER LEVEL NORTHERLY FLOW AND DRY AIR IN SUBSIDENCE
ON THE WESTERN SIDE OF A TROUGH. THE TROUGH RUNS FROM
NORTHEASTERN FLORIDA TO A CYCLONIC CIRCULATION CENTER ALONG THE
NORTHWESTERN CORNER OF THE YUCATAN PENINSULA...TO A SECOND
CYCLONIC CIRCULATION CENTER NEAR 18N93W JUST TO THE EAST OF THE
ISTHMUS OF TEHUANTEPEC. ISOLATED MODERATE SHOWERS AND POSSIBLE
THUNDERSTORMS ARE ON THE EASTERN SIDE OF THE TROUGH SOUTH OF 29N.

THE CARIBBEAN SEA...
A SPECIAL FEATURE 1008 MB LOW PRESSURE CENTER IS NEAR 16N69W.
MIDDLE TO UPPER LEVEL SOUTHWESTERLY WIND FLOW COVERS THE AREA
WEST OF A LINE FROM SOUTHEASTERN CUBA TO THE HONDURAS COAST.
THIS FLOW IS DUE TO THE CYCLONIC FLOW WITH THE NORTHEASTERN
FLORIDA-TO-NORTHWESTERN YUCATAN PENINSULA MIDDLE TO UPPER LEVEL
TROUGH. NUMEROUS STRONG SHOWERS AND THUNDERSTORMS ARE FROM 11N
TO 15N BETWEEN 80W AND THE EAST COAST OF CENTRAL AMERICA.
NUMEROUS STRONG SHOWERS AND THUNDERSTORMS ALSO ARE FROM 17N TO
18N BETWEEN 80W AND 84W. ALL THIS IS JUST TO THE EAST OF THE
MIDDLE TO UPPER LEVEL TROUGH. OTHER ISOLATED MODERATE SHOWERS
ARE ELSEWHERE TO THE WEST OF THE CUBA-TO-HONDURAS LINE. BROAD
UPPER LEVEL ANTICYCLONIC WIND FLOW COVERS THE AREA TO THE EAST
OF THE CUBA-TO-HONDURAS LINE.

THE ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL TROUGH PASSES THROUGH 33N13W TO 29N19W
32N25W. MIDDLE TO UPPER LEVEL ANTICYCLONIC FLOW...THAT IS NORTH
OF 22N17W 22N30W BEYOND 32N38W...IS MOVING ON TOP OF THIS
TROUGH. THE 13/0600 UTC MIDDLE TO UPPER LEVEL TROUGH THROUGH
33N40W TO 24N42W HAS BECOME WEAKER. BROAD CYCLONIC FLOW REMAINS
ALONG 40W FROM 20N TO 32N. A DISSIPATING STATIONARY FRONT PASSES
THROUGH 32N42W TO 28N50W. ISOLATED MODERATE SHOWERS TO POSSIBLE
THUNDERSTORMS ARE NORTH OF 27N BETWEEN 40W AND 50W. ONE MIDDLE
TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR 23N56W.
A SECOND MIDDLE TO UPPER LEVEL CYCLONIC CENTER IS NEAR 24N63W.
BROAD UPPER LEVEL ANTICYCLONIC FLOW IS MOVING ON TOP OF THE AREA
OF THESE TWO CYCLONIC CENTERS. WIDELY SCATTERED MODERATE SHOWERS
TO POSSIBLE THUNDERSTORMS ARE FROM 23N TO 26N BETWEEN 56W AND
63W. SHOWERS AND THUNDERSTORMS ARE FROM 27N TO 28N BETWEEN 74W
AND 79W...ASSOCIATED WITH A COMPARATIVELY FAST-MOVING LOW TO
MIDDLE LEVEL CYCLONIC CIRCULATION CENTER. ISOLATED MODERATE
SHOWERS
AND LOCALLY STRONG THUNDERSTORMS ARE FROM 20N TO 25N BETWEEN 70W
AND SOUTH FLORIDA.

$$
MT






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