[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181038
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU JUN 18 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
1000 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 42W S OF 8N MOVING W NEAR 15 KT. THIS WAVE
COINCIDES WITH A RELATIVELY LOW AMPLITUDE MAXIMUM IN DEEP LAYER
MOISTURE BASED ON TOTAL PRECIPITABLE WATER IMAGERY. ISOLATED
MODERATE CONVECTION IS FROM 6N-8N BETWEEN 40W-42W.

A TROPICAL WAVE IS IN THE S BAY OF CAMPECHE ALONG 92W S OF 20N INTO
THE E PACIFIC MOVING W 10-15 KT. THIS WAVE ALSO COINCIDES WITH A
MAXIMUM IN DEEP LAYER MOISTURE BASED ON TOTAL PRECIPITABLE WATER
IMAGERY. THIS WAVE IS SUPPORTING SCATTERED MODERATE CONVECTION FROM
18N-20N BETWEEN 92W-96W. STRONGER CONVECTION ASSOCIATED WITH THE
WAVE IS S OVER THE E PACIFIC...SEE TWDEP FOR MORE INFORMATION.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 8N12W 7N20W 6N30W 4N40W AND INTO NE
BRAZIL NEAR THE EQUATOR ALONG 51W. SCATTERED MODERATE CONVECTION IS
FROM 5N-9N BETWEEN 12W-18W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 5N-11N BETWEEN 18W-25W. SCATTERED MODERATE
CONVECTION IS FROM 5N-7N 35W-39W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE TROUGH EXTENDS UP THE FLORIDA PENINSULA FROM 28N81W TO
31N83W. SHOWERS PREVIOUSLY ASSOCIATED WITH THIS TROUGH HAVE NOW
DISSIPATED. A TROPICAL WAVE OVER THE S BAY OF CAMPECHE...SEE
ABOVE... ALONG WITH UPPER LEVEL DIFFLUENCE AROUND AN UPPER LEVEL
HIGH NEAR 19N94W ARE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS
OVER THE BAY OF CAMPECHE S OF 20N BETWEEN 92W-96W. ELSEWHERE...A
1016 MB HIGH NEAR 28N87W DOMINATES THE REMAINDER OF THE GULF OF
MEXICO BRINGING FAIR WEATHER ACROSS THE AREA. AN UPPER LEVEL RIDGE
EXTENDS FROM ANOTHER UPPER LEVEL HIGH OVER THE NW GULF OF MEXICO
NEAR 27N95W TO N OVER THE CENTRAL UNITED STATES. THIS UPPER
LEVEL RIDGING IS PROVIDING DRY AIR AND SUBSIDENCE SUPPORTING THE
SURFACE HIGH. ANTICYCLONIC FLOW AROUND THE SURFACE HIGH IS AFFECTING
MUCH OF THE GULF...WITH SE WINDS OF 15-20 KT OCCURRING ACROSS
PORTIONS OF THE NW GULF W OF 95W. EXPECT A SERIES OF WEAK COLD
FRONTS TO MOVE THROUGH THE NE WATERS THROUGH THE WEEKEND.

CARIBBEAN SEA...
UPPER LEVEL DIFFLUENCE AROUND THE UPPER LEVEL HIGH OVER THE S BAY OF
CAMPECHE IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS OVER BELIZE
AND THE ADJACENT COASTAL WATERS FROM 16N-18N BETWEEN 87W-89W. AN
UPPER LEVEL TROUGH IS PRESENT OVER THE CENTRAL CARIBBEAN WITH AN
AXIS EXTENDING FROM AN UPPER LEVEL LOW N OF HISPANIOLA TO 16N74W TO
9N75W OVER NW COLUMBIA. UPPER LEVEL NORTH-NORTHWESTERLY FLOW BETWEEN
THE UPPER LEVEL HIGH OVER THE S BAY OF CAMPECHE AND THIS UPPER LEVEL
TROUGH IS DRAWING DRY AIR AND SUBSIDENCE TO THE CENTRAL GULF
RESULTING IN GENERALLY FAIR WEATHER.
HOWEVER...UPPER LEVEL DIFFLUENCE AT THE BASE OF THE UPPER LEVEL
TROUGH IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS IN THE S
CARIBBEAN OFF THE COAST OF PANAMA AND COSTA RICA S OF 11N BETWEEN
78W-83W. UPPER LEVEL DIFFLUENCE E OF THE TROUGH AXIS IS ALSO
SUPPORTING ISOLATED SHOWERS ACROSS THE E CARIBBEAN S OF 16N E OF
66W.

ATLANTIC OCEAN...
A SHORTWAVE UPPER LEVEL TROUGH OVER THE W ATLC IS ASSOCIATED WITH...
A STATIONARY FRONT EXTENDING FROM A WARM FRONT N OF THE DISCUSSION
AREA FROM 32N80W TO A 1013 MB SURFACE LOW NEAR 32N76W CONTINUING TO
31N66W...A COLD FRONT EXTENDING FROM 31N66W TO 32N61W TO NE OF THE
DISCUSSION AREA...AND A SURFACE TROUGH EXTENDING FROM 28N77W TO
31N75W. LOW LEVEL CONVERGENCE ASSOCIATED WITH THE SURFACE TROUGH IS
SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS WITHIN 60 NM OF THE
TROUGH AXIS. AN UPPER LEVEL TROUGH EXTENDS FROM AN UPPER LEVEL LOW
NEAR 23N68W ACROSS HISPANIOLA AND INTO THE CENTRAL CARIBBEAN. UPPER
LEVEL DIFFLUENCE BETWEEN THIS TROUGH AND THE SHORTWAVE TROUGH
FARTHER W IS SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS N OF CENTRAL
CUBA FROM 22N-23N BETWEEN 76W-78W. SIMILARLY...UPPER LEVEL
DIFFLUENCE E OF THIS SECOND UPPER LEVEL TROUGH IS SUPPORTING
ISOLATED SHOWERS/THUNDERSTORMS N OF THE DOMINICAN REPUBLIC FROM
19N-20N BETWEEN 67W-70W. ACROSS THE MAJORITY OF THE CENTRAL AND E
ATLC A BROAD SURFACE RIDGE DOMINATES ANCHORED BY A 1026 MB SURFACE
HIGH N OF THE DISCUSSION AREA NEAR 39N31W. THIS SURFACE RIDGE IS
PROVIDING FAIR WEATHER ACROSS THE REMAINDER OF THE GULF AND IS
SUPPORTED BY BROAD UPPER LEVEL RIDGING OVER THE MAJORITY OF THE
TROPICAL ATLC. HOWEVER...A DEEP LAYER LOW OVER THE E ATLC IS
ASSOCIATED WITH A 1014 MB SURFACE LOW N OF THE CANARY ISLANDS NEAR
30N19W. LOW LEVEL CONVERGENCE NEAR THIS SURFACE LOW IS SUPPORTING
ISOLATED SHOWERS N OF 30N BETWEEN 16W-20W.

$$
WALTON



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