[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171036 AAA
TWDAT

TROPICAL WEATHER DISCUSSION...UPDATE ON HURRICANE DEAN
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI AUG 17 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
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...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

HURRICANE DEAN IS CENTERED NEAR 14.3N 60.9W AT 17/0900 UTC OR IN
THE ST. LUCIA CHANNEL BETWEEN ST.LUCIA AND MARTINIQUE MOVING W
AT 21 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 976 MB. MAXIMUM
SUSTAINED WIND SPEED IS 85 KT WITH GUSTS TO 105 KT...MAKING DEAN
A CATEGORY TWO HURRICANE. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC OR THE INTERMEDIATE
PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 FOR
MORE DETAILS. DEAN CONTINUES TO MOVE RATHER QUICKLY ALONG THE
SOUTHERN PERIPHERY OF A DEEP LAYERED RIDGE. DEAN IS EXPECTED TO
CONTINUE TO SLOWLY STRENGTHEN AS IT CONTINUES THROUGH THE LESSER
ANTILLES AND ACROSS THE CENTRAL CARIBBEAN. HEAVY SHOWERS AND
EMBEDDED THUNDERSTORMS COVER THE LESSER ANTILLES FROM GRENADA TO
THE VIRGIN ISLANDS. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 12N-18N BETWEEN 58W-64W WITH CLUSTERS OF
SIMILAR CONVECTION COVERING A BROADER AREA FROM 11N-19N BETWEEN
54W-67W.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 28W S OF 20N MOVING W 15-20 KT. A 1007 MB
LOW HAS DEVELOPED ALONG THE WAVE NEAR 14N. OTHERWISE A BROAD
LOW/MID LEVEL ROTATION IS OBSERVED WITH NO ASSOCIATED DEE
CONVECTION. ISOLATED THUNDERSTORMS ARE FROM 11N-12N BETWEEN
27W-32W.

TROPICAL WAVE IS ALONG 40W/41W S OF 20N MOVING W 15-20 KT. BROAD
LOW/MID LEVEL SLIGHTLY TILTED CURVATURE REMAINS MOSTLY TO THE W
OF THE WAVE AXIS. SCATTERED SHOWERS/THUNDERSTORMS ARE FROM
10N-13N BETWEEN 39W-45W.

TROPICAL WAVE OVER THE CENTRAL CARIBBEAN IS ALONG 74W S OF
20N MOVING W NEAR 20 KT. WEAK BUT WELL DEFINED LOW LEVEL
INVERTED-V CURVATURE IS IN THE CENTRAL CARIBBEAN. NO ASSOCIATED
DEEP CONVECTION WITH SOME SCATTERED SHOWERS N OF 15N TO OVER
JAMAICA FROM 74W-78W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 15N16W 15N25W 12N31W 10N44W 12N55W
BECOMING DISTORTED DUE TO HURRICANE DEAN. SEE SPECIAL FEATURES
ABOVE. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
120 NM OF A LINE FROM 11N17W TO 7N31W AND WITHIN 90 NM OF LINE
FROM 6N36W TO 5N40W. CLUSTERS OF SIMILAR CONVECTION ARE FROM
9N-13N E OF 17W TO THE COAST OF AFRICA AND WITHIN 120 NM OF LINE
FROM 6N43W TO 11N55W.

DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL RIDGE FROM THE UPPER HIGH NEAR T.D. ERIN MOVING
ACROSS S/CENTRAL TEXAS EXTENDS S OVER E MEXICO COVERING THE W
GULF AND INDUCING A WEAK INVERTED TROUGH ACROSS THE CENTRAL
GULF. THE DENSE CLOUD COVER OF 6 HOURS AGO IS BEGINNING TO CLEAR
WITH THINNING MID/HIGH CLOUDS REMAINING OVER THE AREA. SOME
SCATTERED SHOWERS/THUNDERSTORMS ARE WITHIN 90/120 NM ALONG THE
COAST OF TEXAS AND MEXICO INTO THE BAY OF CAMPECHE. LARGE UPPER
LOW IN THE W ATLC EXTENDS ACROSS FLORIDA GENERATING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS WITHIN 75 NM OFF THE W COAST OF
FLORIDA FROM 24N-29N BETWEEN THE FLORIDA COAST AND 86W. THE
SURFACE RIDGE FROM THE ATLC EXTENDS ACROSS FLORIDA AND OVER THE
E GULF GIVING THE REMAINDER OF THE GULF MOSTLY CLEAR SKIES THIS
MORNING.

CARIBBEAN SEA...
THE LARGE UPPER LOW EXTENDS S ACROSS CUBA AND HAITI INTO THE NW
CARIBBEAN N OF 13N W OF 73W TO OVER THE YUCATAN PENINSULA
GENERATING SCATTERED CLUSTERS OF SHOWERS/ISOLATED THUNDERSTORMS
N OF 17N TO OVER CUBA BETWEEN 75W-82W AND WITHIN 120 NM ALONG
THE COAST OF N NICARAGUA N OF 13N AND HONDURAS E OF 87W. THE
MAIN CONCERN THIS MORNING IS HURRICANE DEAN AS IT MOVES THROUGH
THE LESSER ANTILLES BETWEEN ST. LUCIA AND MARTINIQUE...SEE
SPECIAL FEATURES ABOVE. THE ITCZ ENTERS THE E PACIFIC REGION
OVER PANAMA AND COSTA RICA PRODUCING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS TO THE SW CARIBBEAN S OF 11N FROM W COAST OF
COLOMBIA TO THE COAST OF COSTA RICA. THE REMAINDER OF THE AREA
REMAINS RATHER CLEAR THIS MORNING BUT CONDITIONS WILL CONTINUE
TO DETERIORATE AS HURRICANE DEAN CROSSES THE AREA DURING NEXT
FEW DAYS.

ATLANTIC OCEAN...
LARGE UPPER LOW IS CENTERED IN THE W ATLC OVER THE N BAHAMA
ISLANDS NEAR 27N77W COVERING THE AREA W OF 71W ACROSS FLORIDA
AND INTO THE NW CARIBBEAN. ALTHOUGH THE W ATLC IS COVERED WITH
MOSTLY DRY NEAR STABLE AIR IT IS ABLE TO PRODUCE SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS FROM CUBA TO OVER THE BAHAMA
ISLANDS SW OF A LINE FROM 23N72W TO 27N77W. AN UPPER HIGH IS TO
THE E NEAR 24N62W AND AN UPPER LOW IS NEAR 27N49W BUT BOTH ARE
RATHER BENIGN UPPER FEATURES. BROAD UPPER RIDGE EXTENDS E/W FROM
OFF AFRICA TO NEAR 40W WITH THE AXIS ALONG 20W/21W. DRY STABLE
AIR DOMINATES THE ATLC WITH THE EXCEPTION OF HURRICANE DEAN. A
BROAD SURFACE RIDGE ALSO DOMINATES THE ATLC INTO THE E GULF OF
MEXICO ANCHORED BY A PAIR OF 1030 MB HIGHS...ONE JUST W OF THE
AZORES AND THE SECOND JUST NE OF THE AZORES GIVING THE ATLC FAIR
WEATHER AND MODERATE TRADE WINDS E OF 50W.

$$
WALLACE





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