[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 201803
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1715 UTC.

...SPECIAL FEATURE...
EXTREMELY DANGEROUS CATEGORY FOUR HURRICANE DEAN WAS NEAR 18.0N
83.2W...OR 285 NM/530 KM EAST OF BELIZE CITY AT 20/1800 UTC.
DEAN IS MOVING WEST 18 KT. ON THIS TRACK DEAN IS EXPECTED TO
MAKE LANDFALL ON THE YUCATAN PENINSULA VERY EARLY TUESDAY
MORNING. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 130 KT WITH GUSTS
TO 160 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 924 MB. ALL
RESIDENTS IN THE WESTERN CARIBBEAN SEA...AND THE SOUTHERN GULF
OF MEXICO SHOULD MONITOR THE PROGRESS OF THIS POWERFUL
HURRICANE. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE LATEST PUBLIC
ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR THE MOST RECENT WATCH
AND WARNING INFORMATION. FOR STORM INFORMATION SPECIFIC TO YOUR
AREA...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR FORECASTS AND BULLETINS ISSUED BY YOUR LOCAL WEATHER
OFFICE. MODERATE TO STRONG CONVECTION IS FROM 16N-19N BETWEEN
81W-85W. SCATTERED MODERATE/ISOLATED STRONG IS ELSEWHERE FROM
12N-21N BETWEEN 80W-88W MOSTLY IN SPIRAL BANDS. LONG PERIOD
SWELL ENERGY IN THE 17 SEC RANGE IS SHOWING UP AT BUOY 42056
THAT IS OUTRUNNING THE STORM. SEAS WILL RAMP UP SIGNIFICANTLY AT
THIS BUOY OVER THE NEXT SEVERAL HOURS. THE NAH WW3 SHOWS SEAS
OVER 50 FT WITH DEAN UNTIL IT MAKES LANDFALL VERY EARLY
TUE...MAINLY IN THE FAVORABLE CAPTURED FETCH REGION N OF THE
CENTER.

...TROPICAL WAVES...

A LARGE AMPLITUDE ATLANTIC OCEAN TROPICAL WAVE IS ALONG 59W
SOUTH OF 28N MOVING WEST 15-20 KT. A QUIKSCAT PASS AT 20/0930
UTC SHOWED THE WAVE AXIS WELL. UPPER-LEVEL WINDS ARE EXPECTED TO
GRADUALLY BECOME MORE FAVORABLE FOR DEVELOPMENT DURING THE
NEXT COUPLE OF DAYS. SCATTERED SHOWERS AND ISOLATED TSTMS
ASSOCIATED WITH THIS SYSTEM ARE FROM 18N-27N BETWEEN
53W-63W...AND ALSO FURTHER S JUST E/SE OF THE WINDWARD ISLANDS S
OF 15N TO THE SOUTH AMERICAN COAST BETWEEN 55W-62W.

A TROPICAL WAVE IS MOVING OUT OF THE GULF OF MEXICO ALONG 96W S
OF 19N MOVING W NEAR 10-15 KT. THIS WAVE HAS LOST MUCH OF ITS
IDENTITY UPON ITS INTERACTION WITH LAND. THE SHOWERS/TSTMS
FURTHER N IN THE WRN GULF SEEM MOSTLY ASSOCIATED WITH THE UPPER
LOW IN THE VICINITY. FURTHER INFORMATION ON THIS WAVE CAN BE
FOUND IN THE PACIFIC DISCUSSION UNDER AWIPS/WMO HEADER
MIATWDEP/AXPZ20 KNHC.

...THE ITCZ...
AXIS IS CENTERED ALONG 13N16W 8N30W 13N47W 19N55W. SCATTERED
MODERATE TO STRONG CONVECTION IS NEAR THE COAST OF AFRICA FROM
11N-14N E OF 18W. ISOLATED CLUSTERS OF MODERATE CONVECTION ARE
WITHIN 250 NM EITHER SIDE OF THE AXIS BETWEEN 29W-42W. AS PER
METSAT-9 HOVMOLLER DIAGRAMS...SOME OF THIS MAY BE ASSOCIATED
WITH A LOW AMPLITUDE TROPICAL WAVE IN THE VICINITY. HOWEVER...AT
THIS POINT ADDING A WAVE TO THE MAP IS HARD TO JUSTIFY WITH THE
STRONG RIDGING BUILDING BEHIND THE LARGE AMPLITUDE WAVE ALONG
59W.

DISCUSSION...

THE GULF OF MEXICO...
A MID TO UPPER LOW IS OVER THE WRN GULF NEAR 24N94W. OVER THE
LAST FEW HOURS...LIGHTNING DATA HAS BEEN DEPICTING ISOLATED TO
SCATTERED TSTMS FROM 23N-28N BETWEEN 91W-97W IN ASSOCIATION WITH
THIS FEATURE. MID TO UPPER SLY FLOW DOMINATES THE ERN GULF ON
THE WRN PERIPHERY OF RIDGING. DEEP LAYER RIDGING IS EXPECTED TO
BUILD W OVER THE NEXT FEW DAYS AS THE MID TO UPPER LOW MOVES
INLAND OVER S TX/NE MEXICO...KEEPING DEAN ON A W OR WNW TRACK.
DEAN IS EXPECTED TO MOVE INTO THE ERN BAY OF CAMPECHE TUE
EVENING AFTER CROSSING THE YUCATAN PENINSULA. IN ADDITION TO THE
HIGH WINDS/SEAS NEAR DEAN...THE STORM IS EXPECTED TO SEND A
SIGNIFICANT SE SWELL THROUGH THE NW GULF WED AND THU. SEE
STATEMENTS FROM LOCAL WEATHER SERVICE OFFICES AND HIGH SEAS
FORECASTS FOR MORE DETAILS. ELSEWHERE AT THE SFC...A RIDGE FROM
THE ATLC IS OVER THE NRN GULF. THE INTERACTION BETWEEN THIS
RIDGE AND DEAN TO ITS S IS PRODUCING FRESH TO STRONG ELY WINDS
IN THE SE GULF AND STRAITS OF FLORIDA.

THE CARIBBEAN SEA...
ALL THE ATTENTION REMAINS FOCUSED ON POWERFUL CATEGORY FOUR
HURRICANE DEAN. DEAN WILL CONTINUE TO HAVE SIGNIFICANT IMPACTS
ON THE WESTERN CARIBBEAN OVER THE NEXT DAY OR SO. IN ADDITION
TO THE CONVECTION OUTLINED WITH DEAN ABOVE...LOW LEVEL
CONFLUENCE FURTHER E IS SPARKING SCATTERED SHOWERS/ISOLATED
TSTMS MAINLY NEAR THE COAST AND S OF JAMAICA FROM 13N-18N
BETWEEN 74W-77W. THE ERN CARIBBEAN IS MOSTLY QUIET ALTHOUGH THE
TROPICAL WAVE ALONG 59W WILL BRING SHOWERS/TSTMS TO THE AREA
LATER TODAY AND TUE. DEEP LAYER RIDGING IS N/NE OF DEAN WHILE AN
ELONGATED UPPER LOW/TROUGH IS OVER THE NE PORTION.

THE ATLANTIC OCEAN...
DEEP LAYER RIDGING IS OVER THE WRN ATLC AREA WITH A 1022 MB SFC
HIGH OFFSHORE THE CAROLINAS NEAR 32N71W. THIS ALONG WITH
ABUNDANT DRY MID TO UPPER AIR IS PRODUCING WIDESPREAD FAIR
WEATHER W OF 65W. E/SE WINDS GET A BIT STRONGER BETWEEN CUBA AND
THE BAHAMAS WITH THE GRADIENT FROM DEAN AFFECTING THE AREA.
DIFFLUENCE ALOFT BETWEEN UPPER TROUGHING N OF THE LEEWARD
ISLANDS...AND AN UPPER HIGH NEAR 25N47W IS ALSO SUPPORTING THE
SHOWERS/TSTMS MENTIONED WITH THE TROPICAL WAVE ALONG 59W. A
BENIGN UPPER LOW IS NEAR 31N32W WHILE TYPICAL UPPER RIDGING
EXTENDS E FROM AFRICA OUT TO 25W. LARGE SCALE SFC RIDGING IS
ALSO OVER THE REMAINDER OF THE E AND CENTRAL ATLC AREA ANCHORED
BY A 1034 MB HIGH N OF THE AZORES NEAR 44N27W. ALL OF THIS IS
PRODUCING ABUNDANT STABLE CONDITIONS AND MODERATE TRADES N OF
15N AND E OF 45W. WINDS REMAIN A LITTLE STRONGER FROM 18N-28N
BETWEEN 45W-62W WHERE THE BROAD WAVE ALONG 59W INTERACTS WITH
THE HIGH.

$$
WILLIS


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