[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211123
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED OCT 21 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
1015 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 29W FROM 7N-17N AND DRIFTING WESTWARD
OVER THE PAST 24 HOURS. THE WAVE AXIS COINCIDES WITH A DEEP
LAYER MOISTURE MAXIMUM AS OBSERVED IN TOTAL PRECIPITABLE WATER
IMAGERY AS WELL AS A MAXIMUM IN 850 MB RELATIVE VORTICITY ON THE
CIMSS GLOBAL MODEL GUIDANCE. THE LOW-LEVEL CLOUD FIELD EXHIBITS
CYCLONIC TURNING IN THE VICINITY OF THE WAVE AXIS WITH ISOLATED
SHOWERS AND MODERATE CONVECTION FROM 12N-18N BETWEEN 23W-30W
WHICH INCLUDES THE CAPE VERDE ISLANDS.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N14W 7N28W 7N31W 9N38W 10N44W
9N61W. A 1009 MB SURFACE LOW IS LOCATED N OF THE AXIS ACROSS THE
CENTRAL TROPICAL ATLC CENTERED NEAR 13N40W. SCATTERED MODERATE
CONVECTION IS FROM 11N-15N BETWEEN 35W-40W IN ASSOCIATION WITH
THE LOW. ELSEWHERE...CLUSTERS OF ISOLATED MODERATE TO STRONG
CONVECTION COVER THE AREA FROM 2N-7N BETWEEN 18W-34W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD SURFACE RIDGE DOMINATES ACROSS FLORIDA AND THE GULF...
ANCHORED OVER THE CAROLINAS BY A 1025 MB HIGH. ALOFT...THE GULF
IS INFLUENCED BY W-NW ANTICYCLONIC FLOW AROUND AN UPPER LEVEL
RIDGE THAT IS ANCHORED BY AN UPPER HIGH CENTERED OVER SRN MEXICO
NEAR 17N98W. STRONG SUBSIDENCE AND DRY STABLE AIR IS NOTED ON
WATER VAPOR IMAGERY PRIMARILY E OF 87W...WHILE UPPER LEVEL
CONVECTIVE DEBRIS CLOUDINESS FROM TROPICAL STORM RICK IN THE
EASTERN PACIFIC ADVECTS EASTWARD AND SPILLS OVER THE TOP OF THE
UPPER LEVEL RIDGE N OF 25N W OF 92W. AT THE SURFACE HOWEVER...E
TO SE SURFACE FLOW UP TO 20 KT IS FORECAST TO CONTINUE THROUGH
WEDNESDAY...TURNING MORE SOUTHERLY OVER THE WESTERN GULF BY
THURSDAY AHEAD OF THE NEXT COLD FRONT EXPECTED TO ENTER THE NW
GULF WATERS LATE THURSDAY.

CARIBBEAN SEA...
A DEEP LAYERED TROUGH IS OVER THE W ATLC AND FLORIDA PENINSULA
THAT DIPS S OVER THE NW CARIBBEAN AND WESTERN CUBA. A 1008 MB
LOW IS CENTERED INLAND OVER COSTA RICA NEAR 10N84W AND EXTENDS
SURFACE TROUGHING N-NW TO A 1010 MB LOW IN THE GULF OF HONDURAS
NEAR 18N87W. AN UPPER LEVEL RIDGE IS LOCATED TO THE E EXTENDING
FROM NORTHERN COLOMBIA NEAR 11N75W TO ACROSS EASTERN HISPANIOLA
AND INTO THE W ATLC. THIS IS PROVIDING A DIFFLUENT ENVIRONMENT
ALOFT ACROSS THE SW CARIBBEAN THAT IS ENHANCING A BROAD AREA OF
SCATTERED SHOWERS AND ISOLATED TSTMS FOCUSED MAINLY E OF THE
SURFACE TROUGH OVER COSTA RICA...NICARAGUA AND EASTERN HONDURAS.
THIS ACTIVITY COVERS THE WESTERN CARIBBEAN W OF A LINE FROM
COLOMBIA NEAR 10N76W TO JAMAICA AND NORTHEASTWARD TO THE
WINDWARD PASSAGE NEAR 20N73W. A BROAD UPPER LEVEL TROUGH COVERS
THE EASTERN CARIBBEAN EXTENDING FROM AN UPPER LOW IN THE CENTRAL
ATLC PROVIDING STRONG SUBSIDENCE AND DRY STABLE AIR E OF 70W.

ATLANTIC OCEAN...
A BROAD DEEP LAYERED UPPER LEVEL TROUGH COVERS MUCH OF THE SW
NORTH ATLC...FLORIDA PENINSULA AND STRAITS OF FLORIDA WITH THE
ASSOCIATED COLD FRONT ENTERING THE REGION NEAR 32N56W SW TO
28N60W WHERE IT BECOMES STATIONARY ALONG 25N65W TO NORTH OF
HISPANIOLA NEAR 20N71W. SCATTERED SHOWERS ARE OCCURRING WITHIN
300 NM BEHIND THE FRONT WITH LOW-LEVEL CONVERGENCE E OF THE
FRONT GENERATING ISOLATED SHOWERS WITHIN 90 NM E OF THE FRONT.
AN UPPER RIDGE EXTENDS FROM THE WESTERN CARIBBEAN THROUGH
EASTERN HISPANIOLA ALONG 24N62W TO 32N52W PROVIDING DIFFLUENCE
ALOFT NW OF THE UPPER RIDGE AXIS THAT IS ENHANCING THE ACTIVITY
ASSOCIATED WITH THE FRONTAL BOUNDARY. FARTHER EAST...A BROAD
UPPER LEVEL LOW IS CENTERED IN THE CENTRAL ATLC NEAR 24N49W WITH
UPPER LEVEL TROUGHING EXTENDING SW TO THE LESSER ANTILLES AND
EASTERN CARIBBEAN. THIS SUPPORTS A SURFACE TROUGH THAT EXTENDS
FROM 19N58W TO 29N52W WITH A 1009 MB SURFACE LOW CENTERED ALONG
THE SURFACE TROUGH NEAR 24N53W. POSSIBLE ISOLATED SHOWERS ARE
WITHIN 120 NM EITHER SIDE OF THE SURFACE TROUGH. UPPER LEVEL
DIFFLUENCE E OF THE UPPER LEVEL LOW HOWEVER IS GENERATING A MUCH
MORE ACTIVE AREA OF SCATTERED SHOWERS AND ISOLATED TSTMS
COVERING THE AREA FROM 23N-30N BETWEEN 37W-49W. ACROSS THE
REMAINDER OF THE ATLC...A BROAD UPPER RIDGE IS LOCATED OVER THE
TROPICAL ATLC ANCHORED NEAR 8N41W THAT EXTENDS A RIDGE AXIS N TO
25N25W. ALSO A WEAKENING COLD FRONT SKIRTS THE NE PORTION OF THE
DISCUSSION AREA ALONG 30N E OF 23W THAT IS BRINGING POSSIBLE
ISOLATED SHOWERS TO THE CANARY ISLANDS AND THE COAST OF WESTERN
MOROCCO.

$$
HUFFMAN





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