[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202355
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON AUG 20 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2245 UTC.

...SPECIAL FEATURE...
HURRICANE DEAN IS CENTERED NEAR 18.2N 85.1W...OR 180 NM E OF
CHETUMAL MEXICO AT 21/0000 UTC MOVING W AT 17 KT. MAXIMUM
SUSTAINED WIND SPEED IS 135 KT WITH GUSTS TO 165 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 915 MB. PLEASE SEE THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
AND THE LATEST PUBLIC ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR
MORE DETAILS. THIS IS NOW A POWERFUL CATEGORY 5 HURRICANE AND IS
EXPECTED TO MAKE LANDFALL OVER THE YUCATAN PENINSULA TUESDAY
MORNING. DEAN HAS A SMALL WELL-DEFINED EYE WITH SCATTERED STRONG
CONVECTION SURROUNDING THE EYE WITHIN 90 NM IN THE NW SEMICIRCLE
AND WITHIN 120 NM IN THE SE SEMICIRCLE. SCATTERED/NUMEROUS
THUNDERSTORMS COVER CUBA W OF 77W...ALL OF BELIZE...AND OVER THE
YUCATAN PENINSULA E OF 89W. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS DOT THE AREA N OF 13N W OF 76W.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 60W/61W S OF 29N MOVING W 15-20 KT. VERY
LARGE AMPLITUDE WAVE WITH UPPER LEVEL WINDS EXPECTED TO
GRADUALLY BECOME MORE FAVORABLE FOR DEVELOPMENT DURING THE NEXT
COUPLE OF DAYS. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE
FROM 19N-26N BETWEEN 50W-62W AND S OF 15N TO INLAND OVER SOUTH
AMERICA BETWEEN 55W-63W INCLUDING THE WINDWARD ISLANDS.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 13N15W 8N40W 13N57W. SCATTERED
STRONG CONVECTION IS FROM 9N-12N BETWEEN 37W-42W. SCATTERED
THUNDERSTORMS DOT THE AREA FROM 3N-10N BETWEEN 28W-54W.
CONVECTION W OF 55W IS ASSOCIATED WITH THE TROPICAL WAVE.

DISCUSSION...

GULF OF MEXICO...
AN UPPER LOW IS OVER THE W GULF CENTERED NEAR 27N95W COVERING
THE W GULF N OF 20N W OF 90W GENERATING SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS FROM 24N-28N W OF 90W TO INLAND OVER S
TEXAS AND NE MEXICO. BROAD UPPER HIGH IN THE W ATLC EXTENDS OVER
THE E GULF WHILE THE FAR SE GULF IS UNDER THE INFLUENCE OF
HURRICANE DEAN. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE
MOVING OFF CUBA AND THROUGH THE YUCATAN CHANNEL AS HURRICANE
DEAN CONTINUES TOWARD THE YUCATAN PENINSULA. THERE ARE SOME LOW
LEVEL ISOLATED SHOWERS AND POSSIBLE THUNDERSTORMS STREAMING N
OVER THE N GULF COAST W OF PANAMA CITY FLORIDA AND OVER S
FLORIDA S OF LAKE OKEECHOBEE WHILE THE REMAINDER OF THE GULF
REMAINS CLEAR THIS EVENING. HOWEVER...CONDITIONS OVER THE S GULF
WILL BEGIN TO DETERIORATE OVERNIGHT AND CONTINUE OVER THE NEXT
COUPLE OF DAYS AS DEAN MOVES ACROSS THE YUCATAN PENINSULA INTO
THE BAY OF CAMPECHE AND OVER MEXICO ON WEDNESDAY.

CARIBBEAN SEA...
THE MAIN FOCUS THIS EVENING REMAINS ON THE POWERFUL HURRICANE
DEAN. DEAN WILL CONTINUE TO HAVE SIGNIFICANT IMPACTS ON THE W
CARIBBEAN OVER THE NEXT DAY OR SO. BROAD UPPER HIGH IS OVER DEAN
GIVING UPPER LEVEL OUTFLOW COVERING ALL OF THE W CARIBBEAN INTO
THE SE GULF OF MEXICO TO OVER CENTRAL AMERICA. SEE SPECIAL
FEATURE ABOVE FOR ASSOCIATED CONVECTION. AN ELONGATED UPPER LOW
IS CENTERED JUST S OF PUERTO RICO NEAR 17N66W EXTENDING E/W FROM
OVER THE LEEWARD ISLANDS TO OVER HAITI GENERATING CLUSTERS OF
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF 17N FROM THE
VIRGIN ISLANDS TO HAITI. BROKEN/OVERCAST HIGH CLOUDS ARE
STREAMING AWAY FROM HURRICANE DEAN ACROSS THE SE CARIBBEAN.
ANOTHER CONCERN THIS EVENING IS THE TROPICAL WAVE JUST MOVING
ACROSS THE LESSER ANTILLES...SEE TROPICAL WAVES ABOVE.

ATLANTIC OCEAN...
BROAD UPPER HIGH IS OVER THE W ATLC CENTERED NEAR 30N76W
COVERING THE AREA W OF 70W AND EXTENDING INTO THE E GULF OF
MEXICO. DRY...SOMEWHAT STABLE AIR COVERS THE W ATLC W OF 68W
WITH SOME LOW LEVEL ISOLATED SHOWERS/THUNDERSTORMS BROUGHT IN BY
MODERATE EASTERLY SURFACE FLOW. AN UPPER TROUGH EXTENDS FROM THE
UPPER LOW JUST S OF PUERTO RICO TO NEAR 27N62W. THE TROPICAL
WAVE IS BENEATH THIS UPPER TROUGH ENHANCING SHOWERS/
THUNDERSTORMS ASSOCIATED WITH THE TROPICAL WAVE. A SECOND UPPER
HIGH TO THE E NEAR 25N53W COVERING THE AREA FROM 46W-56W.  A
BENIGN UPPER LOW IS NEAR 31N32W WHILE TYPICAL UPPER RIDGING
EXTENDS E FROM AFRICA OUT TO 25W. LARGE SURFACE RIDGE COVERS THE
ATLC EXTENDING FROM A SURFACE HIGH N OF THE AZORES SW THROUGH
32N45W TO A 1023 MB HIGH NEAR 33N73W ACROSS THE SE US AND NE
GULF OF MEXICO. ALL OF THIS IS PRODUCING ABUNDANT STABLE
CONDITIONS AND MODERATE TRADE WINDS ACROSS THE ATLC WITH THE
EXCEPTION OF THE AREA ASSOCIATED WITH THE TROPICAL WAVE.

$$
WALLACE


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