[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 221156
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU OCT 22 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 33W S OF 18N MOVING W NEAR 10 KT. THE
WAVE COINCIDES WITH A MAXIMUM IN TOTAL PRECIPITABLE WATER AS
WELL AS AN AREA OF MAXIMUM 850 MB RELATIVE VORTICITY IN GLOBAL
MODEL FIELDS ALONG THE WAVE AXIS. CYCLONIC CURVATURE OF THE LOW
LEVEL CLOUD FIELD IS NOTED ON SATELLITE IMAGERY WITH SCATTERED
MODERATE/ISOLATED STRONG CONVECTION FROM 14N-18N BETWEEN
26W-32W. THE CONVECTION IS CONTINUING TO BE MARGINALLY ENHANCED
BY AN UPPER LEVEL RIDGE OVER THE TROPICAL EASTERN ATLC WHILE AT
THE SAME TIME BEING SHEARED TO THE EAST BY STRONG UPPER LEVEL
WESTERLY FLOW.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 9N31W 8N35W 9N50W 9N61W.
CLUSTERS OF SCATTERED SHOWERS AND ISOLATED MODERATE CONVECTION
ARE FROM 3N-9N BETWEEN 18W-34W.

...DISCUSSION...

GULF OF MEXICO...
THE EASTERN GULF IS CONTROLLED BY A SURFACE RIDGE ANCHORED IN
THE W ATLC LOCATED 150 NM EAST OF THE NORTH CAROLINA COAST.
S-SE RETURN FLOW ASSOCIATED WITH THE SURFACE RIDGE AND THE
RESULTING INCREASED PRESSURE GRADIENT CONTINUES TO IMPACT THE
GULF WITH WINDS UP TO 25 KT ACROSS MUCH OF THE GULF. LOW-LEVEL
3-+C ONVERGENCE AHEAD OF THE NEXT COLD FRONT CURRENTLY
POSITIONED ACROSS CENTRAL TEXAS IS GENERATING ISOLATED SHOWERS
OVER THE NORTHERN GULF WATERS N OF 25N W OF 87W. MOSAIC DOPPLER
RADAR OVER THE NW GULF INDICATES A LINE OF SCATTERED SHOWERS AND
TSTMS FROM HOUSTON TEXAS SOUTHWARD TO 25N96W. SIMILAR ISOLATED
SHOWER ACTIVITY IS MOVING WESTWARD OVER THE SE GULF AND PORTIONS
OF THE FLORIDA PENINSULA THIS MORNING. AN AMPLIFIED UPPER LEVEL
RIDGE EXTENDS FROM SOUTHERN MEXICO OVER THE BAY OF CAMPECHE TO
THE SE CONUS. THIS UPPER RIDGE IS ENHANCING MUCH OF THE CURRENT
SHOWER AND TSTM ACTIVITY OBSERVED ALONG THE TEXAS AND LOUISIANA
GULF COASTS AS WELL AS INTERIOR EASTERN TEXAS. AS THE SURFACE
RIDGE SLIDES EASTWARD...THE COLD FRONT IS FORECAST TO ENTER THE
NW GULF WATERS THIS AFTERNOON.

CARIBBEAN SEA...
A 1009 MB LOW IS IN THE SW CARIBBEAN OFF THE COAST OF NICARAGUA
NEAR 12N83W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING
OVER THE SW CARIBBEAN AND PORTIONS OF CENTRAL AMERICA FROM
10N-17N BETWEEN 77W-85W. THIS AREA IS UNDER THE INFLUENCE OF THE
BASE OF A SHARP UPPER LEVEL TROUGH THAT DIPS SOUTHWARD FROM CUBA
TO EASTERN HONDURAS. UPPER LEVEL DIFFLUENCE E OF THE TROUGH AXIS
IS ENHANCING THE CONVECTION ASSOCIATED WITH THE SURFACE LOW. THE
UPPER LEVEL TROUGH ALSO SUPPORTS A SURFACE TROUGH THAT LIES
LARGELY IN THE SW NORTH ATLC OVER THE SE BAHAMAS AND EXTENDS SW
THROUGH THE WINDWARD PASSAGE TO 19N74W. SCATTERED SHOWERS ARE
OCCURRING FROM 17N-21N BETWEEN 73W-79W...INCLUDING JAMAICA.
FARTHER EAST...AN UPPER LEVEL RIDGE IS ANCHORED OVER NW
VENEZUELA WITH RIDGE AXIS ALONG 69W WHILE UPPER LEVEL TROUGHING
COVERS THE FAR EASTERN CARIBBEAN E OF 63W PROVIDING A DRY STABLE
ENVIRONMENT AND GIVING GENERALLY CLEAR SKIES E OF 66W THIS
MORNING. A FEW ISOLATED LOW-LEVEL SHOWERS HOWEVER ARE PRIMARILY
N OF 17N BETWEEN 66W-70W INCLUDING EASTERN PUERTO RICO AND THE
MONA PASSAGE.

ATLANTIC OCEAN...
A BROAD UPPER LEVEL TROUGH COVERS THE WESTERN AND CENTRAL ATLC N
OF 30N WITH A NARROW AMPLIFIED TROUGH AXIS EXTENDING S OVER THE
SW NORTH ATLC THROUGH 32N70W 27N76W ACROSS CENTRAL CUBA AND INTO
THE NW CARIBBEAN SEA. THIS AMPLIFIED UPPER LEVEL TROUGH IS
PROVIDING STRONG SUBSIDENCE AND MOSTLY DRY STABLE AIR W OF 76W
WITH ONLY A FEW ISOLATED SHOWERS MOVING WESTWARD OVER THE NW
BAHAMAS AND FLORIDA PENINSULA. THE SHARP UPPER LEVEL TROUGH IS
SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 24N72W TO THE
WINDWARD PASSAGE NEAR 20N74W. LOW-LEVEL CONVERGENCE NEAR THE
SURFACE TROUGH COUPLED WITH UPPER LEVEL DIFFLUENCE IS GENERATING
SCATTERED SHOWERS AND ISOLATED TSTMS FROM 18N-28N BETWEEN
64W-76W. ACROSS THE CENTRAL ATLC...THE BROAD UPPER LEVEL TROUGH
IS SUPPORTING A SURFACE TROUGH ANALYZED FROM 31N49W TO 26N55W.
WEST OF THE SURFACE TROUGH...A SURFACE RIDGE ANCHORED BY A 1022
MB HIGH OFF THE COAST OF NORTH CAROLINA CONTINUES TO PROVIDE NE
TO ELY FLOW W OF 55W. EAST OF THE MAIN FRONTAL BOUNDARY IN THE
CENTRAL ATLC...A SURFACE TROUGH EXTENDS FROM 31N41W TO 25N48W.
LOW-LEVEL CONVERGENCE LOCATED TO THE EAST OF THE SURFACE TROUGH
ALONG WITH A MID-LEVEL SHORTWAVE TROUGH WITH AXIS ALONG 42W N OF
20N IS SUPPORTING SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN
120 NM OF A LINE FROM 21N44W TO BEYOND 32N37W. A WEAK SURFACE
RIDGE DOMINATES THE REMAINDER OF THE EASTERN ATLC ANCHORED BY A
1017 MB HIGH CENTERED NEAR 29N25W. IN THE TROPICAL ATLC...A 1009
MB LOW IS N OF THE ITCZ NEAR 14N42W WITH SCATTERED SHOWERS AND
ISOLATED TSTMS E OF THE LOW FROM 11N-16N BETWEEN 35W-41W. THIS
ACTIVITY OVER THE PAST 6 HOURS HAS CONTINUED TO BE INFLUENCED BY
STRONG UPPER LEVEL WESTERLY SHEAR ACROSS A ZONE FROM 12N-18N E
OF 45W.

$$
HUFFMAN



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