[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 122307
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST WED NOV 12 2008

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.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 8N10W 7N22W 7N36W 9N49W 7N60W.
ISOLATED MODERATE CONVECTION IS FROM 6N-8N BETWEEN 10W-13W.
SIMILAR CONVECTION IS FROM 6N-10N BETWEEN 18W-29W. SCATTERED
MODERATE CONVECTION IS WITHIN 180 NM EITHER SIDE OF THE ITCZ
AXIS BETWEEN 31W-40W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 7N-9N BETWEEN 41W-46W...WHICH IS BEING
ENHANCED BY UPPER LEVEL DIFFLUENCE.

...DISCUSSION...

GULF OF MEXICO...
A DEEP TROUGH OVER THE PLAINS OF THE CONUS CONTINUES PROGRESSING
EASTWARD. STRONG AND MOIST SOUTHWESTERLY FLOW ALOFT AHEAD OF THE
TROUGH AXIS IS OVER THE NW GULF. ALSO...STRONG UPPER LEVEL
DIVERGENCE IS AFFECTING THE NW GULF TO THE SOUTH-SOUTHWEST OF A
MID/UPPER-LEVEL WIND SPEED MAXIMUM PRESENT OVER LOUISIANA AND SE
TEXAS. AS A RESULT...A LINE OF THUNDERSTORMS IS MOVING
SOUTHEASTWARD ACROSS THE NW GULF...WITH THE LINE OF
THUNDERSTORMS EXTENDING FROM 30N93W TO 27N95W TO 25N97W...WITH
SCATTERED SHOWERS TRAILING AROUND 60 NM TO THE NW OF THE LINE OF
THUNDERSTORMS. THE SHOWER AND THUNDERSTORM ACTIVITY IS BEING
ENHANCED BY LOW LEVEL CONVERGENCE IN THE VICINITY OF A SURFACE
COLD FRONT EXTENDING FROM SW LOUISIANA NEAR 30N94W TO E OF THE
SE TEXAS COAST NEAR 28N96W TO NE MEXICO NEAR 26N100W...AND A
SURFACE TROUGH INTERSECTING THE COLD FRONT NEAR 28N96W AND
EXTENDING SOUTHWARD TO 26N97W TO 24N97W. FARTHER TO THE
SE...SOUTHWESTERLY UPPER LEVEL FLOW CONTINUES TO INCREASE WITH
THE APPROACH OF THE DEEP LAYER TROUGH. HOWEVER...DEEP LAYER DRY
AIR IS LIMITING DEEP CONVECTION OVER THE S AND E GULF...WITH A
SURFACE RIDGE PRESENT ACROSS THE NE GULF.

CARIBBEAN SEA...
AN UPPER RIDGE AXIS EXTENDS FROM AN UPPER HIGH CENTERED OVER N
HONDURAS NEAR 16N87W TO 19N86W TO W OF CUBA NEAR 22N85W...WITH
THE AXIS OF A SHARP UPPER LEVEL TROUGH EXTENDING FROM NE OF
PUERTO RICO NEAR 18N65W TO 15N66W TO N VENEZUELA NEAR 10N65W.
NORTHWESTERLY FLOW ALOFT IS PRESENT ACROSS MUCH OF THE CARIBBEAN
BETWEEN THE UPPER RIDGE AND SHARP UPPER LEVEL TROUGH. A 1012 MB
SURFACE LOW IS SW OF CUBA NEAR 21N81W...WITH SATELLITE IMAGERY
DEPICTING WELL-DEFINED...LOW-LEVEL CYCLONIC CIRCULATION IN THE
VICINITY OF THIS SURFACE LOW. HOWEVER...DEEP LAYER DRY AIR IS
INHIBITING DEEP CONVECTION ACROSS MUCH THE CARIBBEAN. ISOLATED
MODERATE CONVECTION IS OCCURRING OVER PORTIONS OF SE NICARAGUA...
N COLOMBIA...AND N VENEZUELA...AS WELL AS THE ADJACENT CARIBBEAN
SEA. THIS CONVECTION IS BEING ENHANCED BY GREATER INSTABILITY
OVER HIGHER TERRAIN.

ATLANTIC OCEAN...
AN UPPER RIDGE AXIS IS OVER THE W ATLC EXTENDING FROM W OF CUBA
NEAR 22N85W TO 29N73W TO 32N68W TO NE OF THE DISCUSSION AREA.
DEEP LAYER DRY AIR IS INHIBITING DEEP CONVECTION ACROSS MUCH OF
THE W ATLC. HOWEVER...A SURFACE TROUGH EXTENDS FROM THE CENTRAL
FLORIDA PENINSULA NEAR 28N81W TO 30N80W TO 30N78W. LOW LEVEL
CONVERGENCE NEAR THE SURFACE TROUGH IS SUPPORTING ISOLATED
SHOWERS WITHIN 60 NM EITHER SIDE OF THIS FEATURE. FARTHER TO THE
E...THE AXIS OF A SHARP UPPER TROUGH EXTENDS FROM NE OF PUERTO
RICO NEAR 18N65W TO 25N64W TO 32N59W TO NE OF THE DISCUSSION
AREA...WITH AN UPPER RIDGE AXIS EXTENDING FROM 18N51W TO 25N50W
TO 30N50W. BETWEEN THE UPPER TROUGH AND THE UPPER RIDGE...A
SURFACE TROUGH EXTENDS FROM 20N58W TO 23N57W TO 25N55W. LOW
LEVEL CONVERGENCE NEAR THIS SURFACE TROUGH IS SUPPORTING
SCATTERED MODERATE CONVECTION WITHIN 120 NM EITHER SIDE OF THIS
FEATURE...WHICH IS BEING SUPPORTED BY ATMOSPHERIC LIFT IN MOIST
AND DIFFLUENT SOUTHWESTERLY FLOW ALOFT. FARTHER TO THE E...AN
UPPER TROUGH IS N OF 24N BETWEEN 24W-39W. THIS UPPER TROUGH IS
SUPPORTING A 1016 MB SURFACE LOW NEAR 28N38W...WITH ISOLATED
SHOWERS WITHIN 150 NM OF THE SURFACE LOW. A BROAD UPPER RIDGE IS
FROM 6N-16N BETWEEN THE W COAST OF AFRICA AND 36W. UPPER LEVEL
DIFFLUENCE ASSOCIATED WITH THIS RIDGE IS ENHANCING THE
CONVECTION NEAR THE ITCZ FROM 7N-9N BETWEEN 41W-46W.
ADDITIONALLY...THE AXIS OF A SHARP UPPER LEVEL TROUGH EXTENDS
FROM THE W COAST OF AFRICA NEAR 5N6W TO 3N6W TO 1N6W TO S OF THE
DISCUSSION AREA. ATMOSPHERIC INSTABILITY ASSOCIATED WITH THIS
UPPER TROUGH IS ENHANCING THE CONVECTION NEAR THE ITCZ FROM
6N-8N BETWEEN 10W-13W.

$$
COHEN

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