[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 172348
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON AUG 17 2009

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND 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 2315 UTC.

...SPECIAL FEATURES...
AS OF 2100 UTC...THE CIRCULATION OF TROPICAL DEPRESSION ANA HAS
DISSIPATED INDICATED BY REPORTS FROM AN AIR FORCE RESERVE UNIT
RECONNAISSANCE AIRCRAFT. THE  REMNANTS OF ANA ARE NEAR 17.5N
68.0W...OR ABOUT 140 MILES...225 KM...WEST-SOUTHWEST OF SAN JUAN
PUERTO RICO AND ABOUT 145 MILES...230 KM...EAST-SOUTHEAST OF
SANTO DOMINGO IN THE DOMINICAN REPUBLIC. MAXIMUM SUSTAINED WINDS
ARE NEAR 30 KT WITH GUSTS UP TO 40 KT. THE REMNANTS OF ANA WILL
CONTINUE TO MOVE TOWARD THE WEST-NORTHWEST NEAR 21 KT AS A
TROPICAL WAVE...AND THIS GENERAL MOTION IS EXPECTED TO CONTINUE
OVER THE NEXT DAY OR TWO...TAKING THE SYSTEM OVER HISPANIOLA
LATER TONIGHT. HEAVY RAINFALL AND GUSTY WINDS MAY THREATEN
HISPANIOLA AND CUBA OVER THE NEXT COUPLE OF DAYS. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS CURRENTLY NW OF THE
SYSTEM FROM 17N-24N BETWEEN 68W-75W...AFFECTING MUCH OF
HISPANIOLA...ERN CUBA...AND THE SE BAHAMAS.

THE CENTER OF HURRICANE BILL AT 17/2100 UTC IS NEAR 14.6N
46.7W...OR ABOUT 975 MILES...1570 KM...EAST OF THE LESSER
ANTILLES. THE ESTIMATED CENTRAL PRESSURE IS 969 MB. MAXIMUM
SUSTAINED WIND SPEEDS REMAIN AT 80 KT WITH GUSTS UP TO 100 KT.
HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 30 MILES...45
KM...FROM THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND
OUTWARD UP TO 145 MILES...230 KM. INTENSIFICATION IS
EXPECTED...AND BILL COULD BECOME A MAJOR HURRICANE BY WED.
PLEASE READ THE LATEST FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
TCMAT3/ WTNT23 KNHC FOR MORE DETAILS. NUMEROUS
MODERATE/SCATTERED STRONG CONVECTION IS CURRENTLY FROM 11N-19N
BETWEEN 42W-50W.

...TROPICAL WAVES...
A TROPICAL WAVE EXTENDS FROM 17N33W TO 9N27W MOVING W NEAR 20
KT. THE AXIS IS BEING STRETCHED SE TO NW DUE TO INTERACTION
WITH THE CIRCULATION OF HURRICANE BILL. THE WAVE LIES JUST AHEAD
OF A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE
WATER IMAGERY. ISOLATED MODERATE CONVECTION IS EMBEDDED WITHIN
THE ITCZ FROM 7N-9N BETWEEN 29W-32W.

A TROPICAL WAVE IS ALONG 95W S OF 22N MOVING W NEAR 15
KT...STRETCHING FROM THE SOUTHWESTERN GULF OF MEXICO...ACROSS
THE ISTHMUS OF TEHUANTEPEC INTO THE EASTERN PACIFIC OCEAN. THE
WAVE IS EMBEDDED IN A LARGE AREA OF DEEP LAYER MOISTURE OBSERVED
IN TOTAL PRECIPITABLE WATER IMAGERY. AN UPPER LEVEL LOW IS
LOCATED TO THE W OF THE WAVE AXIS NEAR 20N99W ENHANCING SHOWERS
AND THUNDERSTORMS ACROSS THE SW GULF OF MEXICO...YUCATAN
PENINSULA...SW MEXICO AND INTO THE E PACIFIC. IT IS DIFFICULT TO
SAY WHICH AREA OF SHOWERS IS DIRECTLY ASSOCIATED WITH THE WAVE.
HOWEVER...SCATTERED MODERATE CONVECTION IS WITHIN 100 NM EITHER
SIDE OF THE WAVE AXIS S OF 20N.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 14N16W 10N25W 11N36W 13N42W
9N50W 10N63W. NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS
ALONG THE AFRICAN COAST FROM 9N-12N BETWEEN 13W-16W. SCATTERED
MODERATE CONVECTION IS FROM 7N-9N BETWEEN 33W-38W.

...DISCUSSION...

THE GULF OF MEXICO...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE MAJORITY OF THE
GULF OF MEXICO. ACTIVITY ACROSS THE N GULF N OF 27N BETWEEN
82W-93W IS ENHANCED BY THE REMNANTS OF T.D. CLAUDETTE CURRENTLY
NEAR 33.4N 88.6W OVER THE ALABAMA/MISSISSIPPI STATE BORDER. A
TROPICAL WAVE ALONG 95W IS SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS IN THE SW GULF S OF 19N BETWEEN 92W-96W.
THIS ACTIVITY IS ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN
UPPER LEVEL LOW OVER S MEXICO NEAR 20N99W AND AN UPPER LEVEL
RIDGE ACROSS THE MAJORITY OF THE CENTRAL AND E GULF CENTERED
NEAR 29N88W. THIS UPPER LEVEL DIFFLUENCE IS ALSO SUPPORTING
SHOWERS/THUNDERSTORMS ACROSS THE YUCATAN PENINSULA. UPPER LEVEL
DIFFLUENCE BETWEEN THE UPPER RIDGE OVER THE GULF AND ANOTHER
UPPER LEVEL LOW OVER CUBA NEAR 20N77W IS SUPPORTING
SHOWERS/THUNDERSTORMS ALONG THE ERN GULF S OF 27N E OF 84W
INCLUDING THE W COAST OF FLORIDA. EXPECT SHOWERS/THUNDERSTORMS
TO CONTINUE ACROSS THE MAJORITY OF THE GULF DUE TO THE REMNANTS
OF CLAUDETTE...AND THE APPROACH OF THE REMNANTS OF T.D. ANA.

THE CARIBBEAN SEA...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE NW CARIBBEAN N OF
19N BETWEEN 77W-84W AFFECTING THE MAJORITY OF CUBA. THIS
ACTIVITY IS ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER
LEVEL RIDGE OVER THE CENTRAL AND ERN GULF OF MEXICO AND AN UPPER
LEVEL LOW NEAR 20N77W. NUMEROUS SHOWERS/THUNDERSTORMS ARE ACROSS
CENTRAL AMERICA INCLUDING COSTA RICA AND PANAMA DUE TO THE
PROXIMITY OF THE E PACIFIC ITCZ. NUMEROUS SHOWERS/THUNDERSTORMS
ARE ALSO ACROSS THE MAJORITY OF COLUMBIA AND VENEZUELA DUE TO
BROAD LOW PRESSURE ACROSS THE AREA AND AN UPPER LEVEL DIFFLUENT
ZONE ALOFT. THE REMAINDER OF THE CARIBBEAN IS UNDER DRY AIR AND
SUBSIDENCE ALOFT PROVIDING GENERALLY FAIR WEATHER EXCEPT FOR
PUERTO RICO AND HISPANIOLA WHICH ARE STILL BEING AFFECTED BY THE
REMNANTS OF T.D. ANA...SEE ABOVE. A DRY SAHARAN AIR LAYER IS E
OF 64W SUPPORTING THE FAIR WEATHER ACROSS THE FAR E CARIBBEAN
AND LESSER ANTILLES.

THE ATLANTIC OCEAN...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS MUCH OF THE WRN ATLC.
A SURFACE TROUGH EXTENDS ACROSS THE NW BAHAMAS FROM 24N78W TO
31N71W SUPPORTING SHOWERS/THUNDERSTORMS WITHIN 200 NM NW OF THE
TROUGH AXIS. THIS ACTIVITY IS ENHANCED BY UPPER LEVEL DIFFLUENCE
BETWEEN AN UPPER LEVEL RIDGE OVER THE ERN GULF OF MEXICO AND AN
UPPER LOW OVER CUBA NEAR 20N77W. A SECOND SURFACE TROUGH IS
ACROSS THE SE BAHAMAS FROM 20N74W TO 24N70W AHEAD OF THE
REMNANTS OF T.D. ANA. SURFACE CONVERGENCE NEAR THE TROUGH AND
REMNANTS OF T.D. ANA ARE SUPPORTING SHOWERS/THUNDERSTORMS FROM
19N-26N BETWEEN 69W-75W. ELSEWHERE ACROSS THE ATLC...A BROAD
SURFACE RIDGE DOMINATES ANCHORED BY A PAIR OF 1024 MB SURFACE
HIGHS CENTERED NEAR 32N65W AND 32N33W. IN THE UPPER LEVELS...AN
UPPER LEVEL TROUGH IS N OF 24N BETWEEN 43W-65W. AN UPPER LEVEL
RIDGE CENTERED NEAR 26N39W DOMINATES THE ERN ATLC SUPPORTING DRY
AIR AND SUBSIDENCE N OF 26N E OF 40W.

$$
WALTON



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