[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 262344
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT SEP 26 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.

...SPECIAL FEATURES...

TROPICAL DEPRESSION EIGHT IS CENTERED NEAR 18.9N 35.7W AT
26/2100 UTC OR ABOUT 690 NM WNW OF THE CAPE VERDE ISLANDS MOVING
NW AT 11 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB.
MAXIMUM SUSTAINED WIND SPEED IS 25 KT WITH GUSTS TO 35 KT.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 17N-21N
BETWEEN 32W-35W. SEE THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 23W S OF 17N MOVING W NEAR 15 KT. CIMSS
WAVETRAK MODEL GUIDANCE INDICATES A MAXIMUM IN RELATIVE
VORTICITY IN THE VICINITY OF THE WAVE AXIS AND BROAD CYCLONIC
CURVATURE IS OBSERVED IN THE LOW-LEVEL CLOUD FIELD S OF THE CAPE
VERDE ISLANDS BETWEEN 20W AND 30W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 6N-10N BETWEEN 23W-28W.

TROPICAL WAVE IS ALONG 69W S OF 18N MOVING W NEAR 18 KT. THE
WAVE REMAINS MOVING BENEATH WESTERLY FLOW ALOFT NEAR THE BASE OF
AN UPPER LEVEL TROUGH ACROSS THE N/CENTRAL CARIBBEAN. WATER
VAPOR IMAGERY INDICATES RATHER MODERATELY STABLE AIR ALOFT THUS
VERY LITTLE IN THE WAY OF DEEP CONVECTION OR EVEN SCATTERED
SHOWER ACTIVITY ARE ASSOCIATED WITH THE WAVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 8N25W 10N44W 8N60W. SCATTERED
MODERATE CONVECTION IS ALONG THE W AFRICA COAST FROM 14N-18N
BETWEEN 15W-19W. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN
150 NM EITHER SIDE OF THE AXIS BETWEEN 47W-60W.

...DISCUSSION...

GULF OF MEXICO...
A STATIONARY FRONT REMAINS DRAPED OVER THE NW GULF COAST AND ERN
MEXICO COAST ENTERING FROM LOUISIANA NEAR 30N93W AND CONTINUING
ALONG 27N97W SWD TO 19N95W. THIS FRONTAL BOUNDARY IS SUPPORTED
BY AN UPPER LEVEL TROUGH MOVING ACROSS THE CENTRAL CONUS. MOST
OF THE ENERGY WITH THIS UPPER TROUGH REMAINS NORTH OF THE
GULF...HOWEVER LOW-LEVEL CONVERGENCE ALONG THE STATIONARY FRONT
IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 60 NM
EITHER SIDE OF THE FRONT N OF 26N AND WITHIN 120 NM EITHER SIDE
OF THE FRONT S OF 26N ACROSS THE WRN GULF AND WRN BAY OF
CAMPECHE AS WELL AS PORTIONS OF INTERIOR ERN MEXICO. BROAD UPPER
RIDGING IS IN PLACE ACROSS THE GULF ANCHORED OVER THE NE GULF
NEAR 27N84W EXTENDING A RIDGE AXIS WSW TO NEAR 24N97W OVER THE
WRN GULF WATERS. THIS UPPER RIDGE IS FURTHER SUPPORTING THE
CONVECTION IN THE WRN GULF DUE TO UPPER LEVEL DIFFLUENCE...BUT
IS ALSO GENERATING ISOLATED SHOWERS ACROSS THE NRN GULF N OF
28N. THE REMAINDER OF THE GULF IS INFLUENCED BY MODERATE TO
STRONG SUBSIDENCE ALOFT AND GENERALLY FAIR CONDITIONS S OF 28N E
OF 94W.

CARIBBEAN SEA...
AN ANTICYCLONIC CIRCULATION IS CENTERED IN THE ERN GULF OF
MEXICO AND EXTENDS UPPER LEVEL RIDGING OVER THE NW CARIBBEAN N
OF 16N. MOSTLY DRY AIR AND STRONG SUBSIDENCE COVERS THE NW
CARIBBEAN...HOWEVER A FEW ISOLATED SHOWERS DUE TO UPPER LEVEL
DIFFLUENCE ARE OBSERVED ON SATELLITE IMAGERY N OF 19N BETWEEN
ERN CUBA AND THE ERN YUCATAN PENINSULA. THE REMAINDER OF THE
CARIBBEAN IS BENEATH A BROAD UPPER LEVEL TROUGH THAT EXTENDS
FROM THE SW NORTH ATLC OVER HISPANIOLA AND PUERTO RICO TO ERN
HONDURAS GIVING THE CENTRAL AND ERN CARIBBEAN W TO SW UPPER
LEVEL WINDS. A FEW ISOLATED SHOWERS ARE MOVING WWD ACROSS THE
ERN CARIBBEAN AND LESSER ANTILLES ON MODERATE TO FRESH TRADE
WINDS...HOWEVER MOSTLY FAIR SKIES PREVAIL THIS EVENING. UPPER
LEVEL DIFFLUENCE IS LOCATED OVER PORTIONS OF CENTRAL AMERICA S
OF 16N AND THE SW CARIBBEAN THAT IS PRODUCING SCATTERED SHOWERS
AND ISOLATED TSTMS SW OF A LINE FROM 15N83W TO 11N75W.

ATLANTIC OCEAN...
THE BROAD UPPER LEVEL RIDGE ANCHORED IN THE NE GULF OF MEXICO
COVERS THE W ATLC W OF 68W AND COMBINED WITH A SHARP UPPER LEVEL
TROUGH IN THE W/CENTRAL ATLC THAT EXTENDS THROUGH 32N58W 25N62W
AND INTO THE CARIBBEAN BETWEEN HISPANIOLA AND PUERTO RICO ARE
PRODUCING STRONG NLY UPPER LEVEL WINDS OVER THE W ATLC. THE
UPPER TROUGH IS SUPPORTING A COLD FRONT THAT EXTENDS FROM N OF
THE DISCUSSION AREA TO 32N55W TO 30N63W. A SURFACE TROUGH
EXTENDS SW FROM THE TAIL END OF THE COLD FRONT ALONG 30N61W TO
24N70W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE WITHIN 120 NM
EITHER SIDE OF THE COLD FRONT AND COVER AN AREA MAINLY E OF THE
SURFACE TROUGH FROM 24N-31N BETWEEN 55W-65W. FARTHER TO THE
E...UPPER LEVEL DIFFLUENCE E OF THE UPPER TROUGH OVER THE
CENTRAL ATLC IS GENERATING AN AREA OF SCATTERED SHOWERS AND
TSTMS FROM 25N TO BEYOND 32N BETWEEN 45W-51W. THE ERN ATLC IS
DOMINATED BY A SURFACE RIDGE N OF 25N E OF 45W. SAHARAN DUST IS
STILL OBSERVED ON SATELLITE IMAGERY COVERING THE FAR E TROPICAL
ATLC FROM 15N-26N ACROSS THE CAPE VERDE ISLANDS TO 30W.

$$
HUFFMAN





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