[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 140017
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON 13 SEP 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLC 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 2345 UTC.

...SPECIAL FEATURE...
HURRICANE IVAN...A CATEGORY FIVE HURRICANE ON THE SAFFIR-
SIMPSON SCALE...IS CENTERED NEAR 21.3N 84.9W OR ABOUT 30 MILES/
45 KM SOUTH OF THE WESTERN TIP OF CUBA AT 13/2100 UTC. HURRICANE
IVAN IS MOVING NORTH-NORTHWEST 8 KT. MAXIMUM SUSTAINED WIND
SPEED 140 KT GUSTS 170 KT. ESTIMATED MINIMUM CENTRAL PRESSURE
912 MB. SEE LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 KNHC OR MIATCMAT4/
WTNT24 KNHC FOR MORE DETAILS. NUMEROUS STRONG SHOWERS AND
THUNDERSTORMS FROM 19N TO 23N BETWEEN 82W AND 86W. SCATTERED
MODERATE TO ISOLATED STRONG SHOWERS AND THUNDERSTORMS ALSO
STRETCH FROM THE SOUTHERN YUCATAN PENINSULA AND NORTHERN BELIZE
TO THE FLORIDA KEYS. OVERCAST HIGH CLOUDS EXTEND AS FAR NORTH AS
30N80W...CURVING ANTICYCLONICALLY TOWARD 20N67W AND THROUGH THE
MONA PASSAGE/WESTERN PUERTO RICO. THE NORTHWESTERN AND WESTERN
CARIBBEAN SEA IS COVERED NORTHWEST OF THE LINE FROM THE WINDWARD
PASSAGE TO 15N76W TO 10N82W. A CLEAR AND DISTINCT EYE IS SEEN ON
THE INFRARED IMAGERY AT THIS TIME. A MIDDLE TO UPPER LEVEL
TROUGH IS TO THE NORTHWEST OF HURRICANE IVAN...THROUGH 32N86W
TO 28N90W TO 27N91W...FROM CENTRAL ALABAMA TO THE NORTH CENTRAL
GULF OF MEXICO. WEAK UPPER LEVEL ANTICYCLONIC FLOW EXISTS IN THE
REST OF THE GULF OF MEXICO...SOUTHWEST OF THE TROUGH AND WAY
WEST OF HURRICANE IVAN.

NEW TROPICAL DEPRESSION ELEVEN HAS FORMED NEAR 16.0N 60.4W...OR
ABOUT 75 NM DUE EAST OF THE ISLAND OF DOMINICA...AT 13/2100 UTC
MOVING WEST-NORTHWEST 10 KT. MAXIMUM SUSTAINED WIND SPEED 25 KT
GUSTS 35 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 1010 MB. SEE THE
LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS. NUMEROUS STRONG SHOWERS AND THUNDERSTORMS OVER
THE EASTERN CARIBBEAN ISLANDS FROM 15N TO 17N BETWEEN 60W AND
62W...PRETTY MUCH FROM DOMINICA TO ANTIGUA. SCATTERED MODERATE
TO ISOLATED STRONG SHOWERS AND THUNDERSTORMS ALSO FROM 14N TO 17N
BETWEEN 54W AND 58W. BROKEN TO OVERCAST MULTILAYERED CLOUDS FROM
12N TO 22N BETWEEN 52W AND 65W. TROPICAL STORM CONDITIONS COULD
ALSO AFFECT THE REMAINDER OF THE NORTHERN LESSER ANTILLES TO THE
NORTH OF GUADELOUPE. THE DEPRESSION COULD BECOME A TROPICAL
STORM ON TUESDAY. LOCALLY HIGHER WINDS...POSSIBLY TO TROPICAL
STORM STRENGTH...CAN BE EXPECTED OVER HIGHER TERRAIN.

...TROPICAL WAVES...
WELL-DEFINED TROPICAL WAVE OVER THE EASTERN ATLANTIC OCEAN ALONG
39W/40W SOUTH OF 26N MOVING WEST 15 KT. WIDELY SCATTERED
MODERATE TO ISOLATED STRONG SHOWERS AND THUNDERSTORMS FROM 10N
TO 20N BETWEEN 33W AND 42W. STRONG SHOWERS AND THUNDERSTORMS
FROM 23N TO 25N BETWEEN 36W AND 39W.

TROPICAL WAVE IN THE CENTRAL CARIBBEAN SEA ALONG 73W/74W SOUTH
OF 22N MOVING WEST 10-15 KT. THE WAVE HAS VIRTUALLY NO SATELLITE
SIGNATURE AND THE PERTURBATION IN NEARBY SOUNDINGS HAS BECOME
QUITE WEAK. THE CURRENT POSITION IS BASED PRIMARILY UPON
EXTRAPOLATED MOTION. CLUSTERS OF SHOWERS AND THUNDERSTORMS IN
NORTHERN COLOMBIA...NORTH OF 7N...MAY BE MORE RELATED TO THE
ITCZ THAN TO THIS WAVE.

...ITCZ...
ITCZ 13N16W NEAR SOUTHERN SENEGAL...8N23W 10N39W 7N53W 11N63W...
AND IN THE SOUTHWESTERN CARIBBEAN SEA FROM 11N74W TO 10N86W.
SCATTERED MODERATE TO ISOLATED STRONG SHOWERS AND THUNDERSTORMS
FROM 7N IN THE EASTERN PACIFIC OCEAN TO 10N BETWEEN 82W AND 85W.
WIDELY SCATTERED MODERATE TO ISOLATED STRONG SHOWERS AND
THUNDERSTORMS FROM 4N TO 11N BETWEEN AFRICA AND 31W. ISOLATED
MODERATE SHOWERS AND THUNDERSTORMS FROM 7N TO 9N BETWEEN 47W
AND 50W.

...DISCUSSION...

GULF OF MEXICO...
HURRICANE IVAN IS MOVING TOWARD THE YUCATAN CHANNEL AND THE
WESTERN TIP OF CUBA AT THIS TIME. NUMEROUS STRONG SHOWERS AND
THUNDERSTORMS FROM 19N TO 23N BETWEEN 82W AND 86W. SCATTERED
MODERATE TO ISOLATED STRONG SHOWERS AND THUNDERSTORMS ALSO
STRETCH FROM THE SOUTHERN YUCATAN PENINSULA AND NORTHERN BELIZE
TO THE FLORIDA KEYS. OVERCAST HIGH CLOUDS EXTEND AS FAR NORTH AS
30N80W...CURVING ANTICYCLONICALLY TOWARD 20N67W AND THROUGH THE
MONA PASSAGE/WESTERN PUERTO RICO. THE NORTHWESTERN AND WESTERN
CARIBBEAN SEA IS COVERED NORTHWEST OF THE LINE FROM THE WINDWARD
PASSAGE TO 15N76W TO 10N82W. ISOLATED MODERATE
SHOWERS/THUNDERSTORMS ELSEWHERE WEST OF 90W. A CLEAR AND
DISTINCT EYE IS SEEN ON THE INFRARED IMAGERY AT THIS TIME.
A MIDDLE TO UPPER LEVEL TROUGH IS TO THE NORTHWEST OF HURRICANE
IVAN...THROUGH 32N86W TO 28N90W TO 27N91W...FROM CENTRAL ALABAMA
TO THE NORTH CENTRAL GULF OF MEXICO. WEAK UPPER LEVEL
ANTICYCLONIC FLOW EXISTS IN THE REST OF THE GULF OF MEXICO...
SOUTHWEST OF THE TROUGH AND WAY WEST OF HURRICANE IVAN.

THE CARIBBEAN SEA...
THE MAIN FEATURE OVER THE CARIBBEAN IS HURRICANE IVAN WHICH IS
NEARING THE WESTERN TIP OF CUBA. IVAN HAS BEGUN TO MOVE MORE
NORTHWARD DURING THE LAST 24 HOURS OWING TO THE WEAKENING OF
A PERSISTENT MIDDLE LEVEL RIDGE ACROSS FLORIDA. OUTER RAINBANDS
STRETCH FROM THE FLORIDA KEYS TO NORTHERN BELIZE AND THE
SOUTHERN YUCATAN PENINSULA. WESTERN CUBA IS IN THE DIRECT PATH
OF PRECIPITATION IMMEDIATELY TO THE EAST OF HURRICANE IVAN.
STRONG MIDDLE TO UPPER LEVEL RIDGE...INDUCED BY OUTFLOW FROM
IVAN...COVERS THE EASTERN TWO-THIRDS OF THE CARIBBEAN SEA WITH
ASSOCIATED SUBSIDENCE PRODUCING RATHER TRANQUIL/DRY WEATHER.
TROPICAL DEPRESSION ELEVEN JUST DEVELOPED AT 13/2100 UTC...AND
IS SET TO BRING STRONG SHOWERS AND THUNDERSTORMS TO THE AREA
FROM AT LEAST DOMINICA TO ANTIGUA...AT LEAST AT THIS TIME. IT IS
POSSIBLE THAT THE AREAS OF HEAVY RAIN AND THUNDERSTORMS MAY REACH
MARTINIQUE AND OTHER POINTS NORTH AND WEST OF ANTIGUA.

THE SUBTROPICAL ATLANTIC...
A TROUGH-RIDGE-TROUGH PATTERN PREVAILS ACROSS THE W HALF OF THE
SUBTROPICAL ATLC. THE PATTERN IS COMPRISED OF A MID-UPPER LEVEL
LOW JUST NE OF BERMUDA WITH A TRAILING TROUGH EXTENDING SWD
ALONG 64W/65W TO 20N. ASSOCIATED SUBSIDENCE AND DRY AIR COVERS
THE AREA W OF 65W LIMITING SIGNIFICANT CLOUDS/CONVECTION SAVE
SOME UPPER LEVEL HIGH CLOUDINESS FROM IVAN OVER THE BAHAMAS.
TROUGH FROM MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER
ABOUT 250 NM NORTHEAST OF BERMUDA REACHES 24N64W AND 20N66W.
ISOLATED MODERATE TO LOCALLY STRONG SHOWERS AND THUNDERSTORMS
WITHIN ABOUT 120 NM ON EITHER SIDE OF 22N63W 27N60W BEYOND
32N57W. A MID-UPPER LEVEL RIDGE EXISTS OVER THE CENTRAL ATLC
ALONG 55W WITH THE MID-OCEANIC TROUGH LIMITED TO THE E ATLC
ALONG 31N36W TO 17N45W. STRONG SHOWERS AND THUNDERSTORMS FROM
23N TO 25N BETWEEN 36W AND 39W ARE NEAR THE 39W/40W TROPICAL
WAVE...AND TO THE EAST OF A MIDDLE TO UPPER LEVEL CENTRAL
ATLANTIC OCEAN TROUGH THROUGH 32N42W TO 24N43W TO 15N47W.
THE TROUGH FROM 15N TO 30N BETWEEN 40W AND 52W IS EMBEDDED IN
MIDDLE TO UPPER LEVEL DRY AIR. A WELL DEFINED MIDDLE TO UPPER
LEVEL RIDGE EXTENDS WESTWARD FROM AFRICA ALONG 17N/18N TO 35W.
THIS RIDGE HAS BEEN SLOWLY BUILDING WESTWARD IN THE WAKE OF THE
RETROGRADING MID-OCEANIC TROUGH. SURFACE SUBTROPICAL RIDGE
REMAINS DISRUPTED BY THE WESTERN ATLANTIC UPPER LEVEL CYCLONIC
CENTER AND THE REMNANTS OF A LOW LEVEL TROUGH NEAR THE BAHAMAS.
THIS IS PRODUCING A RATHER WEAK PRESSURE GRADIENT ACROSS THE
WESTERN ATLANTIC WATERS.

TROPICAL ATLANTIC...
A WELL DEFINED MIDDLE TO UPPER LEVEL RIDGE AXIS EXTENDS WESTWARD
FROM AFRICA ALONG 17N/18N TO 35W. THE RIDGE HAS BEEN SLOWLY
BUILDING WESTWARD ALLOWING DEEP LAYERED ELY FLOW TO RETURN TO
THE E ATLC. THIS IS GENERALLY A FAVORABLE REGIME FROM TROPICAL
WAVE DEVELOPMENT. MID-OCEANIC TROUGH DIPS INTO THE TROPICAL ATLC
WATERS BETWEEN 50W-60W. THIS PATTERN IS PRODUCING ENHANCED ITCZ
CONVECTION FROM 35-45W AND SUPPRESSING ITCZ ACTIVITY BETWEEN
45W-55W.

$$
MT


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