[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 201752
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU SEP 20 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...

THE CENTER OF TROPICAL STORM NADINE AT 20/1800 UTC IS NEAR
36.2N 28.6W. NADINE IS ABOUT 135 NM/265 KM TO THE SOUTH
OF PICO IN THE AZORES. NADINE IS MOVING EAST-SOUTHEASTWARD
9 KNOTS. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 981 MB.
THE MAXIMUM SUSTAINED WIND SPEEDS ARE 45 KNOTS WITH GUSTS
TO 55 KNOTS. FLORES IN THE AZORES RECENTLY REPORTED A WIND
GUST TO 46 MPH...74 KM/HOUR. TROPICAL STORM FORCE WINDS EXTEND
OUTWARD UP TO 240 NM/445 KM FROM THE CENTER. SWELLS GENERATED
BY NADINE WILL AFFECT THE AZORES DURING THE NEXT FEW DAYS.
IT IS LIKELY THAT THESE SWELLS MAY CAUSE LIFE-THREATENING
SURF AND RIP CURRENT CONDITIONS. PLEASE CONSULT BULLETINS FROM
YOUR LOCAL WEATHER OFFICE. PLEASE READ THE FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC
ADVISORY...MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS. SCATTERED
MODERATE CONVECTIVE PRECIPITATION IS FROM 35N TO 40N BETWEEN
26W AND 32W.

A 1010 MB LOW PRESSURE CENTER IS NEAR 31N56W. A 1008 MB LOW
PRESSURE CENTER IS NEAR 32N52W. A SURFACE TROUGH EXTENDS FROM
THE 32N52W LOW CENTER TO 26N53W AND 22N55W. THE 24-HOUR
FORECAST IS FOR THE TWO LOW CENTERS TO MERGE AT A SPOT THAT
IS ABOUT 160 NM TO THE NORTHWEST OF THE 1010 MB LOW CENTER.
CONVECTIVE PRECIPITATION...SCATTERED MODERATE TO ISOLATED STRONG
FROM 14N TO 19N BETWEEN 51W AND 57W AND WITHIN 60 TO 90 NM ON
EITHER SIDE OF 18N58W 25N51W 30N45W AND ELSEWHERE TO THE NORTH
OF 27N BETWEEN 50W AND 60W. THE SHOWER AND THUNDERSTORM ACTIVITY
HAS BECOME A LITTLE BETTER ORGANIZED IN ASSOCIATION WITH THIS
NON-TROPICAL GALE THAT IS LOCATED ABOUT 650 MILES TO THE EAST
OF BERMUDA. ATMOSPHERIC CONDITIONS APPEAR TO BE FAVORABLE FOR
GRADUAL DEVELOPMENT OF THIS LOW AS IT MOVES WESTWARD TO
WEST-NORTHWESTWARD ABOUT 10 MPH DURING THE NEXT DAY OR SO.
CONDITIONS ARE EXPECTED TO BECOME LESS FAVORABLE AFTER THAT
MOMENT. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A SUBTROPICAL
OR TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 29W/30W TO THE SOUTH
OF 18N...MOVING WESTWARD 15 TO 20 KNOTS DURING THE LAST 24 HOURS.
WIDELY SCATTERED MODERATE TO ISOLATED STRONG CONVECTIVE
PRECIPITATION IS FROM 15N TO 16N BETWEEN 30W AND 36W.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 57W TO THE SOUTH OF
19N...MOVING WESTWARD 15 TO 20 KNOTS DURING THE LAST 24 HOURS.
THIS WAVE IS MOVING THROUGH THE AREA OF A MIDDLE LEVEL TO UPPER
LEVEL CYCLONIC CIRCULATION CENTER THAT IS NEAR 14N58W. A DEEP
LAYER TROUGH ALSO CONNECTS THE 32N53W CYCLONIC CIRCULATION CENTER
EVENTUALLY TO THE 14N58W CYCLONIC CENTER. IT IS NOT EASY TO FIND
CONVECTIVE PRECIPITATION THAT JUST IS RELATED ONLY TO THIS
TROPICAL WAVE.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 75W/76W FROM 14N IN THE
CARIBBEAN SEA TO 23N IN THE CENTRAL BAHAMAS. A MIDDLE LEVEL
TO UPPER LEVEL INVERTED TROUGH IS ALONG 17N81W...TO THE EAST
CENTRAL COAST OF NICARAGUA...BEYOND COSTA RICA. BROAD UPPER
LEVEL CYCLONIC WIND FLOW COVERS WESTERN CUBA AND PARTS OF THE
NORTHWESTERN CORNER OF THE CARIBBEAN SEA TO THE NORTH OF 18N
BETWEEN 78W AND 83W. CONVECTIVE PRECIPITATION...SCATTERED
STRONG FROM 14N TO 17N BETWEEN 79W AND 82W...SCATTERED MODERATE
TO ISOLATED STRONG IN THE AREA OF THE SOUTHERN BELIZE AND THE
GULF OF HONDURAS AND ITS BORDER AREA WITH EAST CENTRAL
GUATEMALA...ISOLATED MODERATE IS ELSEWHERE TO THE NORTH
OF 18N TO THE WEST OF THE WINDWARD PASSAGE AND TO THE
SOUTH OF 14N TO THE WEST OF 80W.

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

THE MONSOON TROUGH PASSES THROUGH COASTAL GUINEA-BISSAU NEAR
12N16W TO 9N20W 7N30W AND 5N38W. THE ITCZ IS NOT PRESENT
AT THIS MOMENT DUE TO THE PREVAILING WIND FLOW. CONVECTIVE
PRECIPITATION...SCATTERED STRONG IN THE COASTAL PLAINS/COASTAL
WATERS OF AFRICA FROM 10N TO 15N...ISOLATED MODERATE TO LOCALLY
STRONG WITHIN 150 NM ON EITHER SIDE OF 9N13W 7N20W 6N30W 5N40W
7N50W.

...DISCUSSION...

THE GULF OF MEXICO...

A DEEP LAYER TROUGH IS MOVING THROUGH THE CENTRAL U.S.A. AND
THE WESTERN HALF OF THE GULF OF MEXICO. THIS TROUGH SUPPORTS
A STATIONARY FRONT THAT PASSES THROUGH THE ATLANTIC OCEAN NEAR
32N76W TO FLORIDA NEAR 28N82W...INTO THE CENTRAL AND
SOUTHWESTERN SECTIONS OF THE GULF OF MEXICO. BROKEN TO OVERCAST
MULTILAYERED CLOUDS AND WIDELY SCATTERED TO SCATTERED MODERATE
AND ISOLATED STRONG CONVECTIVE PRECIPITATION ARE TO THE EAST AND
SOUTHEAST OF THE LINE THAT PASSES THROUGH THE FLORIDA PANHANDLE
NEAR 30N86W 28N93W 25N96W 24N98W.

A SURFACE RIDGE PASSES THROUGH SOUTHEASTERN TEXAS TO A 1019 MB
INLAND MEXICO HIGH PRESSURE CENTER THAT IS NEAR 22N99W...
TO THE ISTHMUS OF TEHUANTEPEC OF SOUTHERN MEXICO.

THE CARIBBEAN SEA...

A MIDDLE LEVEL TO UPPER LEVEL ATLANTIC OCEAN CYCLONIC
CIRCULATION CENTER IS NEAR 14N58W...ABOUT 95 NM TO THE EAST-
NORTHEAST OF BARBADOS. CYCLONIC WIND FLOW COVERS THE CARIBBEAN
SEA TO THE SOUTH OF 16N TO THE EAST OF 64W. SCATTERED MODERATE
TO STRONG CONVECTIVE PRECIPITATION COVERS PARTS OF THE
NORTHEASTERN CORNER OF THE AREA FROM 17N TO 20N BETWEEN
60W AND 65W.

A TROPICAL WAVE IS ALONG 75W/76W FROM 14N IN THE CARIBBEAN SEA
TO 23N IN THE CENTRAL BAHAMAS. A MIDDLE LEVEL TO UPPER LEVEL
INVERTED TROUGH IS ALONG 17N81W...TO THE EAST CENTRAL COAST OF
NICARAGUA...BEYOND COSTA RICA. BROAD UPPER LEVEL CYCLONIC WIND
FLOW COVERS WESTERN CUBA AND PARTS OF THE NORTHWESTERN CORNER
OF THE CARIBBEAN SEA TO THE NORTH OF 18N BETWEEN 78W AND 83W.
CONVECTIVE PRECIPITATION...SCATTERED STRONG FROM 14N TO 17N
BETWEEN 79W AND 82W...SCATTERED MODERATE TO ISOLATED STRONG
IN THE AREA OF THE SOUTHERN BELIZE AND THE GULF OF HONDURAS
AND ITS BORDER AREA WITH EAST CENTRAL GUATEMALA...ISOLATED
MODERATE IS ELSEWHERE TO THE NORTH OF 18N TO THE WEST OF THE
WINDWARD PASSAGE AND TO THE SOUTH OF 14N TO THE WEST OF 80W.

THE MONSOON TROUGH IS ALONG 9N73W IN COLOMBIA...TO 8N80W IN
PANAMA...BEYOND WESTERN COSTA RICA. NO SIGNIFICANT DEEP
CONVECTIVE PRECIPITATION ACCOMPANIES JUST THE MONSOON TROUGH
IN THE CARIBBEAN SEA.

THE ATLANTIC OCEAN...

A DEEP LAYER TROUGH IS IN THE CENTRAL ATLANTIC OCEAN...
EXTENDING FROM A 32N53W CYCLONIC CIRCULATION CENTER...
TO 24N56W...EVENTUALLY TO THE 14N58W CYCLONIC CIRCULATION
CENTER THAT IS ABOUT 95 NM TO THE EAST-NORTHEAST OF BARBADOS.
A 1010 MB LOW PRESSURE CENTER IS NEAR 31N56W. A 1008 MB LOW
PRESSURE CENTER IS NEAR 32N52W. A SURFACE TROUGH EXTENDS FROM
THE 32N52W LOW CENTER TO 26N53W AND 22N55W. CONVECTIVE
PRECIPITATION... SCATTERED MODERATE TO ISOLATED STRONG FROM
14N TO 19N BETWEEN 51W AND 57W AND WITHIN 60 TO 90 NM ON EITHER
SIDE OF 18N58W 25N51W 30N45W AND ELSEWHERE TO THE NORTH OF 27N
BETWEEN 50W AND 60W.

LARGE SCALE UPPER LEVEL ANTICYCLONIC WIND FLOW IS WITHIN
300 NM ON EITHER SIDE OF A RIDGE THAT IS ALONG 21N76W
27N72W BEYOND 32N71W.

BROAD SURFACE ANTICYCLONIC WIND FLOW COVERS THE AREA THAT
IS TO THE NORTH OF 24N BETWEEN 63W AND 74W. SURFACE ANTICYCLONIC
WIND FLOW COVERS THE AREA FROM 20N TO 30N BETWEEN THE CANARY
ISLANDS AND 48W. THIS ANTICYCLONIC WIND FLOW MOVES AROUND
A 1020 MB HIGH PRESSURE CENTER THAT IS NEAR 25N37W.

PLEASE READ THE HIGH SEAS FORECASTS...MIAHSFAT2...FOR DETAILS
ABOUT TROPICAL STORM NADINE. A 1009 MB LOW PRESSURE CENTER IS
FORECAST TO BE NEAR 32.5N57W AT 48 HOURS INTO THE FORECAST
PERIOD. A TROPICAL WAVE IS FORECAST TO BE ALONG 36W/37W TO THE
SOUTH OF 20N ALSO IN 48 HOURS. EXPECT 20 TO 25 KNOT WINDS AND 8
FOOT SEA HEIGHTS TO THE NORTH OF 29N BETWEEN 53W AND 55W...AND
FROM 13N TO 18N TO THE EAST OF 41W.

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

$$
MT




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