[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 061046
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE OCT 06 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.

...SPECIAL FEATURES...

AN ACTIVE TROPICAL WAVE EXTENDS FROM 20N47W TO 10N54W MOVING WNW
NEAR 13 KT. SATELLITE IMAGERY INDICATES A 1010 MB SURFACE LOW
CIRCULATION ALONG THE WAVE AXIS NEAR 16N50W. THE WAVE COINCIDES
WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL
PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/STRONG CONVECTION
IS FROM 13N-18N BETWEEN 48W-51W. ISOLATED MODERATE CONVECTION IS
TO THE NE DUE TO UPPER LEVEL SHEAR FROM 19N-21N BETWEEN 43W-51W.
THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HRS.

...TROPICAL WAVES...

TROPICAL WAVE IS ADDED ALONG 38W S OF 10N MOVING W NEAR 15 KT.
THIS WAVE IS VERY LOW AMPLITUDE AND MOSTLY EMBEDDED WITHIN THE
ITCZ. SATELLITE IMAGERY AND SATELLITE DERIVED WINDS INDICATE
LOW-LEVEL CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS. THE
WAVE ALSO COINCIDES WITH A LOW-AMPLITUDE DEEP LAYER MOISTURE
MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-10N BETWEEN
36W-42W.

TROPICAL WAVE IS ALONG 61W S OF 14N MOVING W NEAR 10 KT. THE
WAVE REMAINS LOW AMPLITUDE. ISOLATED MODERATE/STRONG CONVECTION
IS FROM 4N-7N BETWEEN 61W-64W. ISOLATED MODERATE CONVECTION IS
ELSEWHERE ALONG THE WAVE AXIS.

TROPICAL WAVE IS ALONG 87W S OF 19N MOVING W NEAR 15 KT. THE
WAVE LIES WITHIN A BROAD AREA OF DEEP LAYER MOISTURE OBSERVED IN
TOTAL PRECIPITABLE WATER IMAGERY. MOST ASSOCIATED CONVECTION IS
CONFINED THE TO THE E PACIFIC BASIN. HOWEVER...ISOLATED SHOWERS
ARE WITHIN 150 NM W OF THE WAVE AXIS FROM 15N-19N.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N16W 7N25W 9N36W 7N44W 13N49W
12N60W. SCATTERED MODERATE/STRONG CONVECTION IS FROM 6N-8N
BETWEEN 13W-16W...AND FROM 11N-13N BETWEEN 15W-17W. SIMILAR
CONVECTION IS WITHIN 75 NM N OF THE AXIS BETWEEN 32W-36W...AND
WITHIN 100 NM OF THE AXIS BETWEEN 54W-59W.

...DISCUSSION...

THE GULF OF MEXICO...
A STATIONARY FRONT EXTENDS JUST N OF THE GULF OF MEXICO ALONG
31N82W TO 30N92W. THE UPPER LEVEL TROUGH SUPPORTING THE FRONT
HAS SHIFTED TO THE E DRAWING MOST OF THE ASSOCIATED
SHOWERS/THUNDERSTORMS TO THE E AS WELL. RADAR IMAGERY INDICATES
A FEW ISOLATED SHOWERS REMAIN N OF 26N E OF 88W. THE REMAINDER
OF THE GULF IS RELATIVELY CALM AND CLEAR AS A SURFACE RIDGE
BUILDS E-W ALONG 27N. A WEAK 1015 MB SURFACE HIGH IS CENTERED
NEAR 27N86W. AN UPPER LEVEL RIDGE COVERS THE BASIN CENTERED OVER
MEXICO NEAR 23N104W WITH AXIS TO THE STRAITS OF FLORIDA NEAR
24N80W CONTINUING INTO THE W ATLC. DRY AIR AND SUBSIDENCE ALOFT
ARE SUPPORTING THE FAIR WEATHER ACROSS THE WRN PORTION OF THE
BASIN W OF 90W. ANTI-CYCLONIC SURFACE FLOW IS AROUND THE SURFACE
RIDGE WITH WINDS REACHING UP TO 15 KT. EXPECT THE SURFACE RIDGE
TO PERSIST FOR THE NEXT FEW DAYS.

THE CARIBBEAN SEA...
AN UPPER LEVEL RIDGE EXTENDING FROM THE GULF OF MEXICO COVERS
THE NW CARIBBEAN BRINGING FAIR WEATHER TO MOST OF THE NW PORTION
OF THE BASIN...EXCEPT FOR A FEW ISOLATED SHOWERS NEAR THE
TROPICAL WAVE ALONG 87W. SEE ABOVE. AN UPPER LEVEL TROUGH COVERS
THE REMAINDER OF THE BASIN EXTENDING FROM THE ATLC ACROSS THE
MONA PASSAGE TO THE SW CORNER OF THE BASIN NEAR COSTA RICA AT
10N83W. DIFFLUENT FLOW AROUND THE BASE OF THE TROUGH IS
SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 12N-15N BETWEEN
82W-85W OVER NICARAGUA...AND FROM 9N-11N BETWEEN 76W-80W NEAR
THE COAST OF COLOMBIA. MOIST SWLY FLOW ALOFT AROUND THE UPPER
TROUGH IS SUPPORTING CLOUDINESS AND ISOLATED SHOWERS ACROSS MUCH
OF THE CENTRAL CARIBBEAN. A SURFACE TROUGH EXTENDS FROM 17N69W
TO 20N67W ACROSS ERN HISPANIOLA. SURFACE CONVERGENCE NEAR THE
TROUGH IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM
16N-18N BETWEEN 68W-72W. A FEW ISOLATED SHOWERS ARE ALSO ACROSS
THE FAR SE CARIBBEAN S OF 14N E OF 64W IN ASSOCIATION WITH A
TROPICAL WAVE ALONG 61W. FRESH TRADEWINDS ARE OVER MUCH OF THE
BASIN WITH STRONGER WINDS IN THE SW AND ERN CARIBBEAN. EXPECT
THE SURFACE TROUGH ACROSS ERN HISPANIOLA TO DISSIPATE LATER
TODAY...AND THE TROPICAL WAVE ALONG 61W TO CONTINUE ACROSS THE E
CARIBBEAN.

THE ATLANTIC OCEAN...
A PRE-FRONTAL SURFACE TROUGH AHEAD OF THE STATIONARY FRONT N OF
THE GULF OF MEXICO EXTENDS FROM 28N80W TO 31N77W. SCATTERED
SHOWERS/THUNDERSTORMS ARE WITHIN 150 NM SE OF THE TROUGH AXIS.
THIS ACTIVITY IS ENHANCED BY DIFFLUENT FLOW ALOFT BETWEEN AN
UPPER LEVEL RIDGE EXTENDING FROM THE GULF OF MEXICO ACROSS THE
STRAITS OF FLORIDA TO NEAR 28N56W...AN UPPER LEVEL TROUGH N OF
30N BETWEEN 55W-75W...AND A SECOND UPPER LEVEL TROUGH TO THE E
WITH AXIS ALONG 30N45W TO THE MONA PASSAGE NEAR 18N69W. THE
DIFFLUENT FLOW ALOFT IS ALSO SUPPORTING ISOLATED
SHOWERS/THUNDERSTORMS WITHIN 100 NM SE OF A LINE FROM 32N65W TO
28N74W. SOME OF THE SHOWER ACTIVITY MAY BE ATTRIBUTED TO A
SURFACE TROUGH EXTENDING FROM THE N INTO THE DISCUSSION AREA
NEAR 32N61W TO 29N65W...AND A SECOND SURFACE TROUGH ENTERING THE
AREA NEAR 32N55W CONTINUING TO 28N62W. A SERIES OF SURFACE HIGHS
DOMINATE THE REMAINDER OF THE ATLC. A 1018 MB HIGH IS NEAR
26N66W. A 1019 MB HIGH IS NEAR 31N47W. A FINAL 1019 MB HIGH IS
NEAR 24N33W. A WEAK SURFACE TROUGH DIGS BETWEEN THE TWO 1019 MB
HIGHS EXTENDING FROM 32N25W TO 27N47W. A FEW ISOLATED SHOWERS
ARE ALONG THE TROUGH AXIS BETWEEN 39W-44W. IN THE UPPER
LEVELS...AN UPPER LEVEL RIDGE COVERS THE BASIN S OF 25N W OF 55W
CENTERED NEAR 14N30W. UPPER DIFFLUENT FLOW ALONG THE W SIDE OF
THE RIDGE IS ENHANCING CONVECTION NEAR THE TROPICAL WAVES ALONG
38W AND THE ACTIVE WAVE NEAR 50W...SEE ABOVE.

$$
WALTON




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