[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 291106
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON JUN 29 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1115 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 17N44W TO 10N46W TO 3N47W MOVING W
10-15 KT AND IS AFFECTING PORTIONS OF THE CENTRAL TROPICAL ATLC.
THIS WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED
ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. SATELLITE
IMAGERY INDICATES THAT THE WAVE COINCIDES WITH AN INVERTED-V
PATTERN IN THE COVERAGE OF LOW LEVEL CLOUDS. SATELLITE-DERIVED
WINDS ALSO INDICATE CYCLONIC CURVATURE IN THE LOW LEVEL FLOW
NEAR THIS WAVE. STABLE ATMOSPHERIC CONDITIONS BENEATH AN UPPER
LEVEL RIDGE AND DEEP LAYER DRY AIR ARE INHIBITING DEEP
CONVECTION NEAR THIS WAVE. HOWEVER...SCATTERED SHOWERS ARE
OCCURRING FROM 10N-12N BETWEEN 41W-45W.

A TROPICAL WAVE IS ALONG 82W S OF 20N MOVING W NEAR 15 KT AND IS
AFFECTING PORTIONS OF THE W CARIBBEAN. THIS WAVE IS NOT
PARTICULARLY WELL-DEFINED. HOWEVER...THE CIMSS WAVETRAK PRODUCT
INDICATES THAT THE WAVE COINCIDES WITH WEAK LOW LEVEL CYCLONIC
CIRCULATION. SCATTERED MODERATE CONVECTION IS FROM 10N-15N
BETWEEN 82W-85W INCLUDING PORTIONS OF NICARAGUA AND COSTA RICA.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 9N13W 6N24W 4N36W 4N44W 5N53W.
SCATTERED MODERATE CONVECTION IS FROM 4N-8N BETWEEN 19W-27W.
SCATTERED MODERATE CONVECTION IS ALSO FROM 3N-5N BETWEEN
49W-51W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE TROUGH OVER THE S GULF EXTENDS FROM 24N87W TO THE
COAST OF MEXICO NEAR 19N91W TO 17N92W. LOW LEVEL CONVERGENCE IS
SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WITHIN
90 NM EITHER SIDE OF THIS SURFACE TROUGH INCLUDING PORTIONS OF
THE YUCATAN PENINSULA. THIS ACTIVITY IS ALSO BEING SUPPORTED BY
UPPER LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER LEVEL RIDGE OVER
THE YUCATAN PENINSULA AND W CARIBBEAN SEA. THIS UPPER LEVEL
DIVERGENCE IS ALSO SUPPORTING SCATTERED SHOWERS AND
THUNDERSTORMS OVER THE BAY OF CAMPECHE S OF 21N W OF 93W
INCLUDING ADJACENT AREAS OF E MEXICO. ACROSS THE NW GULF...
SUBSIDENCE RESULTING FROM UPPER LEVEL CONFLUENCE IS SUPPORTING A
1011 MB SURFACE HIGH NEAR 27N90W. THIS SUBSIDENCE...ALONG WITH
DEEP LAYER DRY AIR...ARE RESULTING IN GENERALLY FAIR WEATHER
ACROSS THE NW GULF. ACROSS THE E GULF...UPPER LEVEL MOISTURE AND
HIGH LEVEL CLOUDS ARE STREAMING SOUTHWARD E OF 85W.

CARIBBEAN SEA...
A TROPICAL WAVE IS ASSOCIATED WITH CONVECTION ACROSS THE W
CARIBBEAN SEA AND IS DISCUSSED IN THE TROPICAL WAVES SECTION
ABOVE. THIS CONVECTION IS BEING SUPPORTED BY UPPER LEVEL
DIFFLUENCE IN NORTHERLY FLOW ALOFT...AS WELL AS THE PRESENCE OF
DEEP LAYER MOISTURE. ALSO...ATMOSPHERIC INSTABILITY ASSOCIATED
WITH AN UPPER LEVEL LOW E OF CUBA NEAR 20N74W IS SUPPORTING
SCATTERED SHOWERS N OF 16N BETWEEN 71W-78W INCLUDING PORTIONS OF
HISPANIOLA. ACROSS THE E CARIBBEAN...SUBSIDENCE IN CONFLUENT
WESTERLY FLOW ALOFT AND DEEP LAYER DRY AIR...INCLUDING
LOW/MID-LEVEL DRY SAHARAN AIR...ARE RESULTING IN GENERALLY FAIR
WEATHER. ADDITIONALLY...FRESH TO STRONG TRADE WINDS ARE FORECAST
TO OCCUR ACROSS THE CENTRAL CARIBBEAN THROUGH THIS WEEK...WITH E
TO SE WINDS OF 20 TO 25 KT CURRENTLY OCCURRING ACROSS PORTIONS
OF THE CENTRAL AND E CARIBBEAN.

ATLANTIC OCEAN...
ACROSS THE SW NORTH ATLC...DIFFLUENCE IN NORTHWESTERLY FLOW
ALOFT IS INTERACTING WITH DEEP LAYER MOISTURE TO SUPPORT
SCATTERED SHOWERS AND THUNDERSTORMS N OF 26N BETWEEN 59W-77W.
THIS ACTIVITY IS ALSO BEING SUPPORTED BY LOW LEVEL CONVERGENCE
ASSOCIATED WITH SURFACE FRONTS ALONG 31N/32N BETWEEN 65W-77W.
ALSO...ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL
LOW E OF CUBA NEAR 20N74W IS SUPPORTING SCATTERED SHOWERS AND
THUNDERSTORMS FROM 22N-25N BETWEEN 74W-77W INCLUDING PORTIONS OF
THE BAHAMAS. FARTHER TO THE E...GENERALLY FAIR WEATHER IS
PRESENT ACROSS MUCH OF THE CENTRAL AND E ATLC...WHERE SUBSIDENCE
IS OCCURRING NEAR A BROAD SURFACE RIDGE. THIS SURFACE RIDGE IS
ASSOCIATED WITH A 1020 MB SURFACE HIGH NEAR 28N44W AND A 1019 MB
SURFACE HIGH NEAR 21N35W. HOWEVER...A SURFACE TROUGH EXTENDS
FROM 24N33W TO 28N21W TO 31N16W AND A DISSIPATING STATIONARY
FRONT EXTENDS FROM 31N16W TO 32N13W TO NE OF THE DISCUSSION
AREA. LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS
WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH AND DISSIPATING
STATIONARY FRONT. ALSO...ATMOSPHERIC INSTABILITY ASSOCIATED WITH
AN UPPER LEVEL LOW NEAR 28N50W IS SUPPORTING SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS FROM 26N-29N BETWEEN 46W-51W. ACROSS
THE TROPICAL ATLC...MOIST EASTERLY FLOW ALOFT IS PRESENT...WITH
UPPER LEVEL DIFFLUENCE SUPPORTING CONVECTION ASSOCIATED WITH THE
ITCZ AND THE TROPICAL WAVE THAT EXTENDS FROM 17N44W TO 10N46W TO
3N47W.

ADDITIONALLY...A NEW TROPICAL WAVE HAS LIKELY MOVED OFF THE W
AFRICAN COAST AND IS APPROXIMATELY ALONG 20W S OF 17N. THE FIRST
VISIBLE SATELLITE IMAGES OF THE DAY IN THIS AREA SHOW THIS
WELL-DEFINED FEATURE MOVING W NEAR 15 KT AND COINCIDING WITH A
RATHER HIGHLY-AMPLIFIED INVERTED-V PATTERN IN THE COVERAGE OF
LOW LEVEL CLOUDS. ALSO...CYCLONIC MOTION OF LOW LEVEL CLOUDS IS
EVIDENT NEAR THIS FEATURE. TIME-HEIGHT ANALYSES FROM DAKAR
SENEGAL INDICATE AN ABRUPT SHIFT OF ANOMALOUS FLOW BELOW THE 750
MB LEVEL FROM NORTHEASTERLY TO SOUTHEASTERLY AROUND 28/1200
UTC...INDICATING THAT WAVE PASSAGE LIKELY OCCURRED AT DAKAR
AROUND THAT TIME. THIS FEATURE COINCIDES WITH A DISTINCT MAXIMUM
IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER
PRODUCT FROM CIMSS. THUS...A TROPICAL WAVE WILL LIKELY BE ADDED
TO THE 29/1200 UTC SURFACE ANALYSIS OVER THE TROPICAL E ATLC.

$$
COHEN




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