[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 282338
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU MAY 28 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 FEATURE...
TROPICAL DEPRESSION ONE IS CENTERED NEAR 37.7N 69.4W AT 28/2100
UTC OR ABOUT 265 NM SOUTH-SOUTHEAST OF PROVIDENCE RHODE ISLAND
AND ABOUT 490 NM SOUTHWEST OF HALIFAX NOVA SCOTIA MOVING NE AT
14 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM
SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. SCATTERED
MODERATE CONVECTION IS WITHIN 90 NM OF THE CENTER IN THE E
SEMICIRCLE. PLEASE SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. THE
DEPRESSION COULD BECOME A TROPICAL STORM TONIGHT OR FRIDAY...BUT
THEN IS EXPECTED TO WEAKEN OR DISSIPATE OVER COLDER WATERS BY
SATURDAY.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 42W S OF 7N MOVING W NEAR 15 KT. TOTAL
PRECIPITABLE WATER PRODUCT FROM CIMSS INDICATES THAT THIS WAVE
COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE. ALSO...CIMSS
WAVETRAK PRODUCT INDICATES A MAXIMUM IN LOW LEVEL CYCLONIC
CIRCULATION AROUND THE WAVE. SCATTERED MODERATE CONVECTION IS
WITHIN 60 NM EITHER SIDE OF THE WAVE AXIS FROM 1N-4N.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 9N13W 4N22W 1N31W CROSSING THE
EQUATOR NEAR 47W EXTENDING INTO NE BRAZIL NEAR 1S49W. NUMEROUS
MODERATE AND STRONG CONVECTION IS MOVING OFF THE W COAST OF
AFRICA FROM 4N-10N...AFFECTING LOCATIONS WITHIN 90 NM OF THE
COASTLINE. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
4N-7N BETWEEN 12W-15W. SCATTERED MODERATE CONVECTION IS FROM
1N-6N BETWEEN 21W-27W. SIMILAR CONVECTION IS S OF 5N BETWEEN
33W-40W AND S OF 3N BETWEEN 44W-46W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH IS ACROSS THE N GULF...WITH AN ASSOCIATED
COLD FRONT EXTENDING FROM S MISSISSIPPI NEAR 30N89W TO 28N91W TO
26N93W WITH A DISSIPATING STATIONARY FRONT CONTINUING
SOUTHWESTWARD TO 24N96W TO 22N97W. ALSO...A SURFACE TROUGH
EXTENDS FROM 28N90W TO 26N91W TO 24N93W. LOW LEVEL CONVERGENCE
NEAR THE SURFACE FRONTS AND TROUGH...AS WELL AS ATMOSPHERIC
INSTABILITY ASSOCIATED WITH THE UPPER LEVEL TROUGH...ARE
RESULTING IN SCATTERED SHOWERS AND THUNDERSTORMS FROM 22N-28N
BETWEEN 86W-90W...AS WELL AS NUMEROUS SHOWERS AND THUNDERSTORMS
S OF 23N W OF 93W. ALL OF THIS CONVECTIVE ACTIVITY IS ALSO BEING
ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH
ACROSS THE N GULF AND AN UPPER LEVEL RIDGE ACROSS THE SW GULF.
ADDITIONALLY...ATMOSPHERIC INSTABILITY ASSOCIATED WITH THE UPPER
LEVEL TROUGH IS SUPPORTING SCATTERED SHOWERS FROM 26N-29N E OF
84W...AS WELL AS ADJACENT INLAND LOCATIONS ALONG THE GULF COAST.
ACROSS THE NW GULF TO THE W OF THE FRONTS...GENERALLY FAIR
WEATHER IS OCCURRING WHERE STABLE ATMOSPHERIC CONDITIONS ARE
PRESENT.

CARIBBEAN SEA...
DEEP LAYER DRY AIR AND SUBSIDENCE IN NORTHWESTERLY FLOW
ALOFT...ALONG WITH MID-LEVEL DRY SAHARAN AIR...ARE RESULTING IN
GENERALLY FAIR WEATHER CONDITIONS ACROSS MUCH OF THE CARIBBEAN.
HOWEVER...ATMOSPHERIC INSTABILITY OVER HIGHER TERRAIN IS
RESULTING IN SCATTERED SHOWERS AND THUNDERSTORMS AFFECTING
CUBA...NICARAGUA...HONDURAS...COSTA RICA...AND PANAMA...AND
NEARBY COASTAL WATERS. SURFACE HIGH PRESSURE ACROSS THE CENTRAL
ATLANTIC IS MAINTAINING FRESH TO STRONG TRADE WINDS ACROSS THE
CENTRAL CARIBBEAN. THE STRONGEST OF THESE WINDS IS FOUND NEAR
THE COAST OF COLOMBIA...WHERE E WINDS OF 25 TO 30 KT ARE
OCCURRING. THE TRADE WINDS ARE ADVECTING POCKETS OF LOW LEVEL
MOISTURE AND ISOLATED SHOWERS WESTWARD ACROSS THE CARIBBEAN. THE
GREATEST CONCENTRATION OF THESE SHOWERS IS FROM 15N-17N BETWEEN
72W-76W.

ATLANTIC OCEAN...
UPPER LEVEL DIVERGENCE AND DEEP LAYER MOISTURE W OF AN UPPER
LEVEL HIGH CENTERED NEAR 25N60W IS RESULTING IN SCATTERED
SHOWERS AND THUNDERSTORMS N OF 23N BETWEEN 68W-74W...FROM
19N-21N BETWEEN 62W-65W...AND N OF 29N BETWEEN 55W-61W. THE
SHOWER AND THUNDERSTORM ACTIVITY N OF 23N BETWEEN 68W-74W IS
ALSO BEING SUPPORTED BY LOW LEVEL CONVERGENCE NEAR A SURFACE
TROUGH EXTENDING FROM 31N65W TO 32N65W TO N OF THE DISCUSSION
AREA. ALSO...UPPER LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER
LEVEL RIDGE WITH AN AXIS EXTENDING FROM 30N79W TO 27N81W IS
SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS S OF 29N BETWEEN
75W-80W INCLUDING THE NW BAHAMAS...CUBA...AND ADJACENT INLAND
LOCATIONS OF FLORIDA.  FARTHER TO THE E...AN UPPER LEVEL TROUGH
N OF THE DISCUSSION AREA IS ASSOCIATED WITH A COLD FRONT
EXTENDING FROM NE OF THE DISCUSSION AREA TO 32N34W TO 30N39W TO
29N42W CONTINUING WESTWARD AS A STATIONARY FRONT TO 30N49W.
ALSO...A SURFACE TROUGH EXTENDS FROM 27N48W TO 22N51W. LOW LEVEL
CONVERGENCE IS SUPPORTING SCATTERED SHOWERS WITHIN 60 NM EITHER
SIDE OF THE COLD AND STATIONARY FRONTS AND SURFACE TROUGH.
BEHIND THE FRONTS...A 1027 MB SURFACE HIGH IS LOCATED NEAR
35N46W AND IS FORECAST TO MOVE SOUTHWARD AND BE LOCATED NEAR
32N47W AS A 1024 MB SURFACE HIGH AT 29/1800 UTC. SUBSIDENCE
ASSOCIATED WITH THIS SURFACE HIGH IS RESULTING IN GENERALLY FAIR
WEATHER CONDITIONS TO THE N OF THE COLD AND STATIONARY FRONTS.
ACROSS THE E ATLC...A SURFACE RIDGE IS PRESENT WHERE MAINLY
ZONAL FLOW ALOFT IS OCCURRING AND FAIR WEATHER CONDITIONS
PERSIST. THE SURFACE RIDGE IS ASSOCIATED WITH A 1022 MB HIGH
NEAR 27N39W. THIS HIGH IS FORECAST TO DISSIPATE DURING THE NEXT
DAY. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE IS PRESENT
S OF 14N E OF 53W WITH AN UPPER LEVEL HIGH NEAR 10N18W. UPPER
LEVEL DIVERGENCE ASSOCIATED WITH THE UPPER LEVEL HIGH AND RIDGE
IS ENHANCING THE CONVECTION ASSOCIATED WITH THE ITCZ AND THE
TROPICAL WAVE ALONG 42W S OF 7N...AS WELL AS NUMEROUS SHOWERS
AND THUNDERSTORMS FROM 1N-4N BETWEEN 7W-13W.

$$
COHEN




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