[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 162345
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED SEP 16 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
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 22W S OF 22N MOVING W NEAR 15 KT. UPPER
AIR TIME SECTION ANALYSES FROM DAKAR SENEGAL INDICATE THAT A
SHALLOW LAYERED WAVE PASSED AROUND 15/0000 UTC. ALSO...HOVMOLLER
DIAGRAM ANALYSIS OF METEOSAT-9 IMAGERY OVER THE PAST FEW DAYS
SHOWS THE WAVE EMERGING OFF THE W AFRICA COAST. THE WAVE ALIGNS
ITSELF ON THE LEADING EDGE OF A MAXIMUM IN DEEP LAYER MOISTURE
AS NOTED ON THE TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 11N-17N BETWEEN
19W-24W.

TROPICAL WAVE IS ALONG 79W S OF 14N MOVING W NEAR 12 KT. THIS
WAVE REMAINS LOW AMPLITUDE AND COINCIDES WITH A BROAD AREA OF
DEEP LAYER MOISTURE ACROSS THE SW CARIBBEAN AS OBSERVED IN TOTAL
PRECIPITABLE WATER IMAGERY. WIDELY SCATTERED MODERATE CONVECTION
IS FROM 8N-13N BETWEEN 74W-81W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 11N21W 10N24W 7N35W
12N60W 11N66W. WIDELY SCATTERED MODERATE CONVECTION IS FROM
6N-12N BETWEEN 24W-35W. SCATTERED MODERATE CONVECTION IS WITHIN
120 NM OF THE AXIS BETWEEN 46W-62W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 2100 UTC...A SURFACE TROUGH EXTENDS FROM ERN LOUISIANA
NEAR 29N91W TO 25N94W. THE BOUNDARY IS SUPPORTED BY AN UPPER
LEVEL LOW OVER NW LOUISIANA AND UPPER LEVEL TROUGHING THAT DIPS
SWD OVER MUCH OF TEXAS...LOUISIANA AND THE NW GULF. WHILE THE
SURFACE TROUGH DENOTES A WIND SHIFT AT THE SURFACE...MOIST SWLY
WINDS ALOFT SWEEP ACROSS MUCH OF THE GULF FROM E/CENTRAL MEXICO
NE TO NRN FLORIDA AND THE SE CONUS. MOISTURE IS BEING DRAWN NEWD
FROM SRN MEXICO AND COUPLED WITH THE UPPER LEVEL DIFFLUENCE IS
GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS OVER THE SW GULF
S OF 24N BETWEEN 90W-95W...INCLUDING THE BAY OF CAMPECHE ALONG
WITH A LARGE AREA OF SIMILAR CONVECTION N OF 24N E OF 90W OVER
THE NE GULF. A 1014 MB SURFACE HIGH IS CENTERED OVER THE SE GULF
NEAR 24N84W AND IS SUPPORTED ALOFT BY AN UPPER LEVEL
ANTICYCLONIC CIRCULATION CENTERED OVER WRN CUBA NEAR 22N84W. DRY
AIR IS NOTED ON WATER VAPOR IMAGERY S OF 24N E OF 90W AND IT
KEEPING GENERALLY FAIR SKIES OVER THE SE GULF AND STRAITS OF
FLORIDA.

CARIBBEAN SEA...
THE NW CARIBBEAN AND YUCATAN PENINSULA REMAINS FAIRLY CALM UNDER
THE INFLUENCE OF DRY AIR AND SUBSIDENCE ALOFT ASSOCIATED WITH AN
UPPER LEVEL HIGH OVER WRN CUBA NEAR 22N84W. HOWEVER...A FEW
SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING DUE TO
DAYTIME HEATING AND INSTABILITY OVER MUCH OF CUBA AND THE
CARIBBEAN WATERS N OF 17N BETWEEN 76W-84W. FARTHER S...A
TROPICAL WAVE ALONG 79W IS SUPPORTING ISOLATED SHOWERS IN THE SW
CARIBBEAN 8N-13N BETWEEN 74W-81W...SEE ABOVE. THIS ACTIVITY IS
BEING ENHANCED BY SURFACE CONVERGENCE NEAR THE ITCZ AXIS ACROSS
PANAMA ALONG 9N. AN UPPER LEVEL LOW NEAR 15N70W IS SUPPORTING A
LARGE AREA OF DISTURBED WEATHER ACROSS THE ERN CARIBBEAN. MOIST
SWLY FLOW ALOFT COUPLED WITH UPPER LEVEL DIFFLUENCE IS
GENERATING SCATTERED SHOWERS AND TSTMS E OF A LINE FROM CENTRAL
HISPANIOLA TO THE N/CENTRAL COAST OF VENEZUELA NEAR 10N66W.
SCATTERED SHOWERS EXTEND FROM OVER PUERTO RICO...THE US/UK
VIRGIN ISLANDS AND MOST OF THE LESSER ANTILLES.

ATLANTIC OCEAN...
A SURFACE TROUGH EXTENDS FROM A 1011 MB SURFACE LOW NEAR 33N71W
TO THE NW BAHAMAS NEAR 26N75W. SCATTERED SHOWERS AND TSTMS ARE
WITHIN 200 NM E OF THE SURFACE TROUGH BOUNDARY. THIS ACTIVITY IS
BEING ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN A BROAD UPPER
LEVEL TROUGH OVER THE W ATLC AND AN UPPER LEVEL RIDGE THAT
EXTENDS FROM WRN CUBA TO BERMUDA. THE UPPER LEVEL LOW OVER THE
ERN CARIBBEAN NEAR 15N70W IS SPREADING A FEW ISOLATED SHOWERS
OVER THE FAR SW NORTH ATLC AND PORTIONS OF THE TROPICAL N ATLC S
OF 21N BETWEEN 62W-70W. ACROSS THE CENTRAL ATLC...A SURFACE
TROUGH IS ANALYZED FROM 18N53W TO 25N55W. SCATTERED SHOWERS AND
ISOLATED TSTMS ARE WITHIN 200 NM EITHER SIDE OF THE SURFACE
TROUGH AND ARE BEING ENHANCED BY THE NRN PERIPHERY OF AN UPPER
LEVEL LOW CENTERED NEAR 19N52W. A 1011 MB SURFACE LOW IS
CENTERED NEAR 15N32W AND CONTINUES TO SURROUND ITSELF WITH
DISORGANIZED SHOWERS FROM 13N-18N BETWEEN 30W-36W. FARTHER TO
THE N...AN UPPER LEVEL TROUGH IS DIGGING SWD ACROSS THE NE ATLC
WITH AN UPPER LEVEL LOW CENTERED NEAR 28N28W. A SURFACE TROUGH
IS ANALYZED FROM 25N29W TO 30N28W WITH ASSOCIATED SCATTERED
SHOWERS AND POSSIBLE ISOLATED TSTMS FROM 27N-30N BETWEEN
26W-30W. ACROSS THE ERN TROPICAL ATLC...AN UPPER LEVEL RIDGE
DOMINATES S OF 20N E OF 43W AND CONTINUES TO ENHANCE THE
CONVECTION ALONG THE ITCZ.

$$
HUFFMAN



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