[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 241058
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN SEP 24 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND THE 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...
HURRICANE HELENE IS CENTERED NEAR 39.9N 39.9W OR ABOUT 612 NM
WEST-NORTHWEST OF THE AZORES AT 24/0900 UTC MOVING EAST-
NORTHEAST AT 20 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 973
MB. MAXIMUM SUSTAINED WIND SPEED IS 75 KT WITH GUSTS TO 90 KT.
SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. HELENE RETAINS TROPICAL
CHARACTERISTICS BUT STILL IS IS EXPECTED TO BECOME EXTRATROPICAL
OVER THE NEXT 12 TO 24 HOURS. SCATTERED MODERATE CONVECTION IS
WITHIN 300 NM OF THE CENTER IN THE NW QUADRANT. DENSE OVERCAST
CLOUDS WITH SHOWERS/THUNDERSTORMS IS N OF 37N FROM 37W-45W.

...TROPICAL WAVES...
A 1009 MB LOW IS CENTERED NEAR 19N43W NEAR STATIONARY. LOW LEVEL
CENTER IS SW OF THE ASSOCIATED DEEP CONVECTION. SCATTERED
MODERATE/STRONG CONVECTION IS WITHIN 75/90 NM OF LINE
18N40W-23N43W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG
CONVECTION ARE WITHIN 75 NM OF 38W FROM 17N-23N.

TROPICAL WAVE IS ALONG 45W/46W S OF 17N MOVING W 10 KT. WEAK
WAVE EMBEDDED WITHIN DRY AIR AND HAS NO ASSOCIATED
SHOWERS/CONVECTION.

TROPICAL WAVE IS OVER THE LESSER ANTILLES ALONG 62W S OF 20N
MOVING W 10 KT. BROADENING INVERTED-V SIGNATURE CURVATURE FROM
56W-65W WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM
13N-19N BETWEEN 56W-63W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N13W 7N21W 7N31W 10N40W BECOMING
DISTORTED BY THE TROPICAL LOW/WAVE THEN ALONG 11N48W 13N63W
10N68W ACROSS N PORTION OF SOUTH AMERICA AND S OF PANAMA INTO
THE E PACIFIC REGION. APART FROM THE CONVECTION ASSOCIATED WITH
THE TROPICAL LOW/WAVE...SCATTERED MODERATE/STRONG CONVECTION IS
FROM 8N-11N BETWEEN 21W-26W. CLUSTERS OF SCATTERED MODERATE/
ISOLATED STRONG CONVECTION ARE FROM 4N-8N BETWEEN 20W-29W AND
WITHIN 120 NM ALONG THE COAST OF AFRICA S OF 8N W OF 8W.

...DISCUSSION...
GULF OF MEXICO...
BROAD UPPER TROUGH EXTENDS FROM AN UPPER LOW MOVING ACROSS THE
GREAT LAKES TO TEXAS WITH THE ASSOCIATED STRONG COLD FRONT STILL
INLAND OVER THE TEXAS COAST. A SQUALL LINE EXTENDS INTO THE GULF
ACROSS CENTRAL LOUISIANA TO INLAND OVER S TEXAS NEAR CORPUS
CHRISTI. AN UPPER HIGH IS CENTERED OVER NE MEXICO NEAR 23N99W
WITH A BROAD RIDGE COVERING THE W GULF W OF 91W. ANOTHER UPPER
HIGH IS ANCHORED IN THE W ATLC EXTENDING A RIDGE OVER THE E GULF
E OF 85W. THE UPPER LOW IS SQUEEZED BETWEEN THESE RIDGES AND
CENTERED IN THE SE GULF N OF THE YUCATAN PENINSULA NEAR 23N88W
GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM
80W-87W.

CARIBBEAN SEA...
THE UPPER LOW CENTERED IN THE SE GULF COVERS A SMALL PORTION OF
NW CARIBBEAN N OF 20N W OF 85W. BROAD UPPER RIDGE OVER THE W
ATLC DIPS S OVER CUBA INTO THE CARIBBEAN N OF 17N FROM 74W-85W.
THIS COMBINATION IS GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS N OF 16N W OF 73W. REMAINDER OF THE CARIBBEAN IS
UNDER NE UPPER FLOW WITH MOSTLY DRY AIR. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS INLAND AND WITHIN 30/60
NM ALONG THE COAST OF PANAMA DUE TO THE CLOSE PROXIMITY OF THE
ITCZ AXIS. THE REMAINDER OF THE CARIBBEAN REMAINS CLEAR THIS
MORNING.

ATLANTIC OCEAN...
BROAD UPPER RIDGE COVERS THE W ATLC ANCHORED BY AN UPPER HIGH
NEAR 29N75W AND COVERS THE AREA W OF 62W INTO THE N CARIBBEAN.
WEAK UPPER TROUGH EXTENDS FROM 25N45W SW TO JUST E OF THE
LEEWARD ISLANDS NEAR 18N59W AND IS ENHANCING THE SHOWER ACTIVITY
ASSOCIATED WITH THE TROPICAL WAVE OVER THE LESSER ANTILLES.
UPPER LEVEL TROUGH IS PUSHING SE OVER THE CANARY ISLANDS AND
WESTERN SAHARA IN AFRICA. BROAD UPPER HIGH ANCHORED NW OF THE
CAPE VERDE ISLANDS NEAR 18N28W COVERS THE REMAINDER OF THE E
ATLC. AT THE SURFACE...A COLD FRONT HAS PUSHED S INTO THE AREA
IN THE CENTRAL ATLC IN THE WAKE OF HURRICANE HELENE THROUGH
32N42W SW TO 28N51W THUS SPLITTING THE SUBTROPICAL RIDGE THAT
CROSSES THE ATLC. W ATLC SURFACE RIDGE EXTENDS FROM A 1022 MB
HIGH WELL N OF THE REGION THROUGH 32N70W ACROSS NE FLORIDA TO
NEAR 29N85W. THE E ATLC RIDGE COVERS THE REGION N OF 20N FROM
20W-37W ANCHORED BY A 1018 MB HIGH NEAR 32N29W.

$$
WALLACE





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