[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 190001
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN OCT 18 2009

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2315 UTC.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 16N21W 10N23W 6N24W
MOVING WESTWARD 10 TO 15 KT. ISOLATED MODERATE SHOWERS TO
POSSIBLE THUNDERSTORMS IN A FEW CLUSTERS FROM 10N TO 16N
BETWEEN 20W AND 24W.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 14N33W 9N35W 4N36W
MOVING WESTWARD 10 TO 15 KT. NEARBY ITCZ PRECIPITATION.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 56W/57W TO THE SOUTH
OF 13N MOVING WEST 10 TO 15 KT. SHOWERS IN THE ITCZ ARE NEAR
THIS WAVE.

A WESTERN CARIBBEAN SEA TROPICAL WAVE IS ALONG 80W/81W TO
THE SOUTH OF 17N MOVING WESTWARD 10 TO 15 KT. A 1008 MB LOW
PRESSURE CENTER IS ALONG THE WAVE NEAR 11N. THE FORECAST IS
FOR THE LOW PRESSURE CENTER TO REMAIN NEARLY STATIONARY FOR
THE NEXT 24 HOURS. NUMEROUS STRONG SHOWERS AND THUNDERSTORMS
ARE FROM 13N TO 16N BETWEEN 81W AND 82W. NUMEROUS STRONG SHOWERS
AND THUNDERSTORMS ALSO HAVE DEVELOPED IN NORTHERN COLOMBIA FROM
10N TO THE COAST BETWEEN THE BORDER WITH VENEZUELA ALONG 72W/73W
AND 76W...AND IN EASTERN PANAMA NEAR 9N78W. A MIDDLE TO UPPER
LEVEL CYCLONIC CIRCULATION CENTER IS NEAR 12N79W. AFTERNOON
HEATING PROBABLY HAS ADDED ENERGY TO THE PRECIPITATION
DEVELOPMENT...WITH UPPER LEVEL ANTICYCLONIC OUTFLOW. SOME UPPER
LEVEL DIFFLUENT FLOW IS PRESENT IN THE SOUTHWESTERN CORNER OF
THE CARIBBEAN SEA ALSO.

...THE ITCZ...

FROM 13N23W TO 9N34W TO 6N40W 7N50W 8N57W...INTO NORTHERN GUYANA
AND EASTERN VENEZUELA NEAR 7N61W. BROKEN TO OVERCAST MULTILAYERED
CLOUDS AND ISOLATED MODERATE CONVECTIVE PRECIPITATION IN GENERAL
FROM 7N TO 16N BETWEEN 19W AND 40W. ISOLATED MODERATE SHOWERS AND
POSSIBLE THUNDERSTORMS FROM GUYANA NEAR 6N TO 10N BETWEEN 56W
AND 62W.

...DISCUSSION...

THE GULF OF MEXICO...
THE EASTERN U.S.A. DEEP LAYER TROUGH PASSES THROUGH SOUTHERN
SOUTH CAROLINA INTO THE SOUTH CENTRAL GULF OF MEXICO. DRY AIR
IN SUBSIDENCE COVERS EVERYTHING TO THE NORTH OF THE LINE FROM
THE FLORIDA KEYS TO 22N90W TO 18N85W. UPPER LEVEL MOISTURE
REMAINS TO THE SOUTH OF THE SAME LINE. THE COLD FRONT HAS
MOVED OUT OF THE AREA COMPLETELY. SURFACE HIGH PRESSURE
CONTINUES TO BUILD ACROSS THE AREA BEHIND THE COLD FRONT.

THE CARIBBEAN SEA...
THE UPPER LEVEL TROUGH THAT WAS SUPPORTING THE COLD FRONT WHILE
THE COLD FRONT WAS MOVING THROUGH THE GULF OF MEXICO STILL DOES
NOT REACH THE CARIBBEAN SEA YET. A SEPARATE AREA OF NARROW UPPER
LEVEL CYCLONIC FLOW FROM A TROUGH COVERS PART OF THE AREA FROM
WESTERN CUBA TOWARD THE GULF OF HONDURAS AND BEYOND EL SALVADOR
AND GUATEMALA INTO THE EASTERN PACIFIC OCEAN. UPPER LEVEL
ANTICYCLONIC FLOW COVERS THE CARIBBEAN SEA BETWEEN 70W AND THE
NARROW TROUGH. A SEPARATE AREA OF UPPER LEVEL ANTICYCLONIC FLOW
IS TO THE NORTH OF 16N TO THE EAST OF 65W. A SEPARATE AREA OF
UPPER LEVEL CYCLONIC FLOW COVERS THE SOUTHEASTERN CORNER TO THE
SOUTH OF 16N TO THE EAST OF 65W. ALL THE WEATHER TO THE EAST
OF 65W IS RELATED TO LARGE-SCALE FEATURES ORIGINATING IN THE
ATLANTIC OCEAN. DRY AIR IN SUBSIDENCE IS TO THE EAST OF THE LINE
FROM THE EASTERN DOMINICAN REPUBLIC TO NORTHEASTERN VENEZUELA.
THE COLD FRONT HAS MOVED THROUGH THE GULF OF MEXICO COMPLETELY
AND IT NOW PASSES THROUGH 21N78W TO 20N82W TO 19N85W TO NORTH
CENTRAL COASTAL HONDURAS. ISOLATED MODERATE SHOWERS ARE WITHIN
30 NM TO 60 NM ON EITHER SIDE OF 16N88W 19N84W 20N80W. STRONG
SHOWERS AND THUNDERSTORMS GO FROM CUBA TO THE BAHAMAS ISLANDS
FROM 21N TO 22N BETWEEN 75W AND 77W.

THE ATLANTIC OCEAN...
A DEEP LAYER TROUGH SUPPORTS THE COLD FRONT THAT PASSES THROUGH
31N70W TO THE BAHAMAS NEAR 24N76W...ACROSS CUBA NEAR 21N78W AND
BEYOND INTO THE CARIBBEAN SEA. MIDDLE LEVEL TO UPPER LEVEL
MOISTURE AND POSSIBLE SHOWERS ARE WITHIN 180 NM ON EITHER SIDE
OF THE LINE THAT PASSES THROUGH 32N70W TO 27N73W TO THE CUBA
COAST NEAR 22N77W. AN ATLANTIC OCEAN DEEP LAYER TROUGH PASSES
THROUGH 29N27W TO 28N32W TO A CYCLONIC CENTER THAT IS NEAR
27N37W TO 21N47W TO A SECOND CYCLONIC CENTER THAT IS NEAR
17N48W TO 10N54W. PART OF THE CYCLONIC FLOW THAT IS AROUND THIS
TROUGH EASILY REACHES THE SOUTHEASTERN CORNER OF THE CARIBBEAN
SEA. THE FLOW STOPS BEING CYCLONIC NEAR 16N60W. DRY AIR IN
SUBSIDENCE COVERS MUCH OF THE AREA TO THE NORTH OF 10N BETWEEN
40W AND 60W...AND FROM THE NORTHEASTERN CARIBBEAN SEA ISLANDS
TO 32N BETWEEN 60W AND 70W.

$$
MT



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