[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 210428
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT THU SEP 21 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0315 UTC.

...SPECIAL FEATURES...
HURRICANE HELENE IS CENTERED NEAR 27.1N 57.0W OR ABOUT 513 MILES
SOUTHEAST OF BERMUDA AT 21/0300 UTC MOVING NORTH AT 8 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 961 MB. MAXIMUM SUSTAINED
WIND SPEED IS 85 KT WITH GUSTS TO 105 KT. SEE THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC
FOR MORE DETAILS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
COVERS THE AREA FROM 26N-29N BETWEEN 55W-58W. DENSE OVERCAST
CLOUDS COVERS A MUCH LARGER AREA FROM 24N-32N BETWEEN 53W-61W.

...TROPICAL WAVES...
TROPICAL WAVE IS W OF THE CAPE VERDE ISLANDS ALONG 31W S OF 19N
MOVING W 15-20 KT. BROAD MID LEVEL INVERTED-V CURVATURE WITH
SCATTERED MODERATE/STRONG CONVECTION W OF THE WAVE AXIS WITHIN
90/120 NM OF LINE 18N31W-11N35W.

TROPICAL WAVE IS ALONG 47W S OF 18N MOVING W 15 KT. WEAK LOWER
AMPLITUDE INVERTED-V SIGNATURE WITH CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION MOSTLY E OF THE WAVE AXIS
FROM 12N-16N BETWEEN 41W-48W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N14W 12N22W 11N30W 12N41W 8N51W
ACROSS N PORTION OF SOUTH AMERICA AND PANAMA INTO THE E PACIFIC
REGION NEAR 9N83W. SCATTERED MODERATE/STRONG CONVECTION IS
MOVING OFF THE COAST OF AFRICA FROM 9N-14N E OF 18W. SCATTERED
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
FROM 5N-16N BETWEEN 19W-35W.

...DISCUSSION...
GULF OF MEXICO...
BROAD UPPER RIDGE ANCHORED ALONG THE W COAST OF MEXICO COVERS
ALL OF MEXICO WITH A RIDGE AXIS EXTENDING NE OVER THE
MISSISSIPPI VALLEY AND A SECOND RIDGE AXIS EXTENDING E OVER THE
GULF ALONG 24N TO 85W. DEEP LAYER TROUGH OVER THE FAR E US AND
THE W ATLC EXTENDS S OVER THE E GULF N OF 24N E OF 85W WITH THE
ASSOCIATED COLD FRONT ENTERING THE GULF OVER S FLORIDA NEAR
26N81W TO 26N86W WHERE IT BECOMES STATIONARY FRONT ACROSS THE
REMAINDER OF THE GULF. ISOLATED SHOWERS ARE FROM 24N-27N E OF
88W TO THE FLORIDA COAST AND OVER THE FLORIDA KEYS. DIFFLUENCE
OVER THE BAY OF CAMPECHE IS GENERATING SCATTERED SHOWERS/
THUNDERSTORMS S OF 20N E OF 96W TO INLAND OVER S MEXICO.

CARIBBEAN SEA...
BROAD UPPER RIDGE THAT COVERS THE W GULF OF MEXICO ALSO COVERS
THE NW CARIBBEAN W OF 85W. AN UPPER LOW IS IN THE W CARIBBEAN
NEAR 17N82W WITH A TROUGH EXTENDING TO OVER CENTRAL CUBA NEAR
22N79W AND SW TO THE TIP OF HONDURAS/NICARAGUA. THIS IS
GENERATING SCATTERED SHOWERS/THUNDERSTORMS OFF THE COAST OF
NICARAGUA FROM 12N-16N BETWEEN 78W-83W. UPPER HIGH COVERS THE
REMAINDER OF THE CARIBBEAN ANCHORED JUST S OF HAITI NEAR 17N74W
THUS LEAVING THE CARIBBEAN E OF 77W DRY TONIGHT.

ATLANTIC OCEAN...
BROAD UPPER TROUGH OVER THE FAR E US AND THE GULF OF MEXICO
COVERS THE W ATLC N OF 26N W OF 75W WITH THE ASSOCIATED COLD
FRONT ENTERING THE AREA NEAR 32N71W SW ACROSS FLORIDA INTO THE
GULF OF MEXICO NEAR 26N81W. ISOLATED SHOWERS ARE WITHIN 90 NM OF
LINE FROM THE FLORIDA E COAST NEAR 26N80W TO BEYOND 32N69W. AN
UPPER RIDGE IS ANCHORED CLOSE TO THE BAHAMAS NEAR 24N75W
EXTENDING A RIDGE AXIS NE TO BEYOND 32N68W. NARROWING UPPER
TROUGH IS WEDGE BETWEEN THE ABOVE RIDGE AND THE UPPER HIGH
ASSOCIATED WITH HURRICANE HELENE WHICH HAS BROADEN OVER THE PAST
24 HOURS TO ENCOMPASS A LARGE AREA FROM 21N-40N BETWEEN 48W-63W.
NARROWING CUT-OFF UPPER LOW E OF HELENE IS BEING COMPRESSED BY
THE UPPER HIGH OFF THE COAST OF AFRICA AND IS CENTERED NEAR
22N38W EXTENDING A TROUGH AXIS NE/SW FROM 27N34W-18N43W. UPPER
HIGH ANCHORED NE THE CAPE VERDE ISLANDS NEAR 18N23W COVERS THE
REMAINDER OF THE E ATLC. AT THE SURFACE...A 1022 MB HIGH IS
LOCATED NEAR 29N38W WITH A RIDGE EXTENDING S TO 20N FROM AFRICA
TO 50W WITH THIS AREA VERY DRY TONIGHT.

$$
WALLACE



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