[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 281047
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN JUN 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1045 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 14N40W TO 8N43W TO 1N43W MOVING W
NEAR 10 KT AND IS AFFECTING PORTIONS OF THE TROPICAL ATLC. THIS
WAVE IS ANALYZED NEAR THE LEADING EDGE OF AN ELONGATED 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. COMPUTER MODEL
GUIDANCE SUGGESTS THAT AN AREA OF STRONGER LOW LEVEL CYCLONIC
CIRCULATION IS EMBEDDED FARTHER EASTWARD INTO THE ELONGATED DEEP
LAYER MOISTURE MAXIMUM...APPROXIMATELY ALONG 36W/37W S OF 11N.
THIS AREA WILL CONTINUE TO BE MONITORED FOR THE PRESENCE OF A
TROPICAL WAVE.

A TROPICAL WAVE IS ALONG 72W/73W S OF 20N MOVING W NEAR 10 KT
AND IS AFFECTING PORTIONS OF THE CENTRAL CARIBBEAN. THIS WAVE IS
NOT PARTICULARLY WELL-DEFINED. HOWEVER...COMPUTER MODEL GUIDANCE
SUGGESTS THAT THE WAVE COINCIDES WITH WEAK LOW LEVEL CYCLONIC
CIRCULATION. ALSO...THE SOUNDING FROM CURACAO AT 27/1200 UTC
INDICATES ANOMALOUS SOUTHEASTERLY FLOW IN THE LOW LEVELS...
SUGGESTING THE WAVE AXIS WAS WEST OF CURACAO AT THAT TIME. THE
PRESENCE OF DRY LOW/MID-LEVEL SAHARAN AIR OVER PORTIONS OF THE
CENTRAL AND E CARIBBEAN IS INHIBITING DEEP CONVECTION NEAR THIS
WAVE. HOWEVER...SCATTERED SHOWERS ARE OCCURRING FROM 16N-19N
BETWEEN 73W-75W.

A HIGHLY-AMPLIFIED TROPICAL WAVE EXTENDS FROM THE S CENTRAL GULF
OF MEXICO NEAR 24N88W TO 14N90W INTO THE E PACIFIC REGION NEAR
2N90W MOVING W NEAR 10 KT. SURFACE OBSERVATIONS AND COMPUTER
MODEL GUIDANCE INDICATE CYCLONIC CURVATURE IN THE LOW LEVEL FLOW
NEAR THE WAVE. LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED
MODERATE CONVECTION FROM 20N-24N BETWEEN 82W-88W INCLUDING
PORTIONS OF THE YUCATAN PENINSULA AND W CUBA. THIS CONVECTION IS
ALSO BEING SUPPORTED BY UPPER LEVEL DIVERGENCE ASSOCIATED WITH
AN UPPER LEVEL RIDGE OVER THE W CARIBBEAN. WHILE NO DEVELOPMENT
OF THIS SYSTEM IS EXPECTED AS IT MOVES ACROSS THE YUCATAN
PENINSULA...SOME SLOW DEVELOPMENT IS POSSIBLE AFTER IT MOVES
INTO THE S GULF OF MEXICO LATER TODAY OR TONIGHT. THERE IS A LOW
CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS. MEANWHILE...LOCALLY
HEAVY RAINS AND GUSTY WINDS WILL CONTINUE TO AFFECT PORTIONS OF
THE YUCATAN PENINSULA AND W CUBA THROUGH TONIGHT.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 9N13W 9N23W 9N34W 7N46W 5N53W.
SCATTERED MODERATE CONVECTION IS FROM 5N-7N BETWEEN 10W-16W.
SCATTERED MODERATE CONVECTION IS ALSO FROM 8N-11N BETWEEN
16W-23W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL LOW IS CENTERED OVER THE W GULF NEAR 22N98W.
ATMOSPHERIC INSTABILITY ASSOCIATED WITH THIS UPPER LEVEL LOW IS
SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF 20N
W OF 94W. ELSEWHERE ACROSS THE N AND W GULF...SUBSIDENCE IN
CONFLUENT EASTERLY FLOW ALOFT BETWEEN AN UPPER LEVEL HIGH OVER
CENTRAL TEXAS AND THE AFOREMENTIONED UPPER LEVEL LOW OVER THE W
GULF...AS WELL AS DEEP LAYER DRY AIR...ARE RESULTING IN
GENERALLY FAIR WEATHER. CONVECTION ASSOCIATED WITH A TROPICAL
WAVE OVER THE S CENTRAL GULF IS DISCUSSED IN THE TROPICAL
WAVES SECTION ABOVE.

CARIBBEAN SEA...
CONVECTION ASSOCIATED WITH A TROPICAL WAVE OVER THE S CENTRAL
GULF OF MEXICO IS ALSO AFFECTING THE NW CARIBBEAN AND IS
DISCUSSED IN THE TROPICAL WAVES SECTION ABOVE. ACROSS THE SW
CARIBBEAN...UPPER LEVEL DIFFLUENCE IN NE FLOW ALOFT IS
INTERACTING WITH UPPER LEVEL MOISTURE TO RESULT IN SCATTERED
SHOWERS AND THUNDERSTORMS S OF 11N W OF 76W. ACROSS THE CENTRAL
AND E CARIBBEAN...SUBSIDENCE IN NORTHERLY AND NORTHWESTERLY FLOW
ALOFT AND DEEP LAYER DRY AIR...INCLUDING LOW/MID-LEVEL DRY
SAHARAN AIR...ARE RESULTING IN GENERALLY FAIR WEATHER.
HOWEVER...UPPER LEVEL MOISTURE AND HIGH LEVEL CLOUDS ARE
STREAMING SOUTHWARD ACROSS THE N CENTRAL CARIBBEAN.

ATLANTIC OCEAN...
ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL TROUGH
DIGGING SOUTHWARD INTO THE SW NORTH ATLC IS SUPPORTING NUMEROUS
SHOWERS AND THUNDERSTORMS N OF 28N BETWEEN 70W-79W...WITH
SCATTERED SHOWERS AND THUNDERSTORMS N OF 27N BETWEEN 62W-70W.
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
1022 MB SURFACE HIGH NEAR 30N43W AND A 1020 MB SURFACE HIGH NEAR
21N35W. HOWEVER...AN UPPER LEVEL TROUGH N OF 17N E OF 25W IS
SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 25N34W TO 27N26W
TO 31N20W AND A COLD FRONT THAT EXTENDS FROM 31N20W TO 32N17W TO
NE OF THE DISCUSSION AREA. LOW LEVEL CONVERGENCE IS SUPPORTING
SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH
AND COLD FRONT. ALSO...ATMOSPHERIC INSTABILITY ASSOCIATED WITH
AN UPPER LEVEL LOW NEAR 25N53W IS SUPPORTING SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS FROM 24N-27N BETWEEN 51W-57W. 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 14N40W TO 8N43W TO
1N43W.

$$
COHEN




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