[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 172308
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED JUN 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
2245 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 39W/40W S OF 8N MOVING W AROUND 15 KT. THIS
WAVE COINCIDES WITH A RELATIVELY LOW AMPLITUDE MAXIMUM IN DEEP LAYER
MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS.
VISIBLE SATELLITE IMAGERY DEPICTS CYCLONIC CIRCULATION IN THE MOTION
OF LOW LEVEL CLOUDS NEAR THIS WAVE...WHICH IS CONFIRMED BY THE CIMSS
WAVETRAK PRODUCT. SCATTERED MODERATE CONVECTION IS FROM 3N-7N
BETWEEN 34W-38W.

A TROPICAL WAVE IS ALONG 89W/90W S OF 20N MOVING W 10-15 KT. THIS
WAVE ALSO COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON
THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. COMPUTER MODEL
GUIDANCE INDICATES LOW LEVEL CYCLONIC CIRCULATION IN THE VICINITY OF
THIS WAVE. THIS WAVE IS SUPPORTING SCATTERED MODERATE TO STRONG
CONVECTION FROM 14N-21N BETWEEN 88W-91W INCLUDING PORTIONS OF THE
YUCATAN PENINSULA AND CENTRAL AMERICA. THIS CONVECTION IS BEING
SUPPORTED BY ATMOSPHERIC INSTABILITY DRIVEN BY DAYTIME HEATING OVER
LAND AREAS.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N14W 7N23W 5N33W 2N42W CROSSING
THE EQUATOR NEAR 47W AND EXTENDING TO NE BRAZIL NEAR 1S49W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-10N BETWEEN
14W-28W. SCATTERED MODERATE CONVECTION IS S OF 2N BETWEEN 44W-47W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE TROUGH OVER FLORIDA EXTENDS FROM 31N84W TO 26N81W. LOW
LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS
WITHIN 60 NM EITHER SIDE OF THIS TROUGH INCLUDING PORTIONS OF THE W
FLORIDA PENINSULA. A SECOND SURFACE TROUGH IS AFFECTING PORTIONS OF
THE S GULF. THIS SECOND SURFACE TROUGH EXTENDS FROM THE BAY OF
CAMPECHE NEAR 20N94W TO OVER MEXICO NEAR 17N94W AND EXTENDS
SOUTHWARD INTO THE EAST PACIFIC REGION. LOW LEVEL CONVERGENCE NEAR
THIS SECOND SURFACE TROUGH IS SUPPORTING SCATTERED SHOWERS AND
THUNDERSTORMS FROM 16N-20N BETWEEN 91W-96W INCLUDING PORTIONS OF S
MEXICO. THIS ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIVERGENCE
AROUND AN UPPER LEVEL RIDGE OVER THE SW GULF OF MEXICO. THE SECOND
SURFACE TROUGH IS FORECAST TO MOVE W OF THE GULF OF MEXICO BY
MIDNIGHT TONIGHT. ALSO...THE TROPICAL WAVE ALONG 89W/90W S OF 20N IS
FORECAST TO MOVE THROUGH THE BAY OF CAMPECHE TONIGHT AND THURSDAY.
ACROSS THE N AND CENTRAL GULF...DEEP LAYER DRY AIR AND SUBSIDENCE IN
NORTHWESTERLY FLOW ALOFT ARE PRESENT. THIS SUBSIDENCE IS SUPPORTING
A 1019 MB SURFACE HIGH OVER THE N GULF NEAR 28N87W. ANTICYCLONIC
FLOW AROUND THE SURFACE HIGH IS AFFECTING MUCH OF THE GULF...WITH SE
WINDS OF 15 TO 20 KT OCCURRING ACROSS PORTIONS OF THE W GULF IN
RESPONSE TO A BROAD SURFACE TROUGH OVER MEXICO AND THE SOUTHERN
PLAINS OF THE UNITED STATES.

CARIBBEAN SEA...
A SHARP UPPER LEVEL TROUGH IS PRESENT OVER THE CENTRAL CARIBBEAN
WITH AN AXIS EXTENDING FROM 18N72W TO 12N73W. TO THE W OF THIS
TROUGH AXIS...SUBSIDENCE AND DEEP LAYER DRY AIR IN
NORTH-NORTHWESTERLY FLOW ALOFT ARE RESULTING IN GENERALLY FAIR
WEATHER ACROSS MUCH OF THE W CARIBBEAN. HOWEVER...ATMOSPHERIC
INSTABILITY IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS
CUBA...JAMAICA...AND THE NEARBY COASTAL WATERS. ACROSS THE E
CARIBBEAN...UPPER LEVEL MOISTURE AND HIGH LEVEL CLOUDS ARE STREAMING
NORTHEASTWARD TO THE E OF THE TROUGH AXIS. THIS MOISTURE IS
INTERACTING WITH ATMOSPHERIC INSTABILITY TO RESULT IN SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS OVER THE NE CARIBBEAN N OF 16N E
OF 73W INCLUDING PORTIONS OF HISPANIOLA...PUERTO RICO...AND THE
NEARBY COASTAL WATERS. MODERATE TO FRESH EASTERLY TRADES ARE
AFFECTING THE CARIBBEAN SEA...WITH NE TO E WINDS OF 20 TO 25 KT
ACROSS PORTIONS OF THE SW AND E CARIBBEAN SEA.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH OVER THE SW NORTH ATLC IS ASSOCIATED WITH A
STATIONARY FRONT EXTENDING FROM N OF THE DISCUSSION AREA TO 32N81W
TO 31N80W TO A 1012 MB SURFACE LOW NEAR 32N76W...A WARM FRONT
EXTENDING FROM THE SURFACE LOW TO 31N69W...A COLD FRONT EXTENDING
FROM 31N69W TO 32N65W TO NE OF THE DISCUSSION AREA...AND A SURFACE
TROUGH EXTENDING FROM 31N76W TO 27N78W. LOW LEVEL CONVERGENCE NEAR
THESE FEATURES IS INTERACTING WITH MOISTURE IN DIFFLUENT WESTERLY
FLOW ALOFT TO RESULT IN SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
N OF 23N W OF 76W INCLUDING PORTIONS OF THE NW BAHAMAS. ACROSS MUCH
OF THE CENTRAL AND E ATLC...GENERALLY FAIR WEATHER IS PRESENT WHERE
SUBSIDENCE IS OCCURRING NEAR A BROAD SURFACE RIDGE. THIS SURFACE
RIDGE IS ASSOCIATED WITH A 1026 MB SURFACE HIGH N OF THE DISCUSSION
AREA NEAR 35N34W. HOWEVER...A DEEP LAYER LOW OVER THE E ATLC IS
ASSOCIATED WITH A 1012 MB SURFACE LOW N OF THE CANARY ISLANDS NEAR
30N18W. LOW LEVEL CONVERGENCE NEAR THIS SURFACE LOW IS SUPPORTING
SCATTERED SHOWERS N OF 28N BETWEEN 14W-19W. ACROSS THE TROPICAL
ATLC...A BROAD UPPER LEVEL RIDGE IS S OF 15N E OF 55W WITH AN UPPER
LEVEL HIGH NEAR 11N42W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THE
UPPER LEVEL HIGH AND UPPER LEVEL RIDGE IS SUPPORTING THE CONVECTION
ASSOCIATED WITH THE ITCZ AND WITH THE TROPICAL WAVE ALONG 39W/40W S
OF 8N.

$$
COHEN


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