[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 280554
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI AUG 28 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

TROPICAL STORM DANNY IS CENTERED NEAR 28.9N 74.2W AT 28/0600 UTC
OR ABOUT 385 NM S OF CAPE HATTERAS NORTH CAROLINA MOVING NW AT
9 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB. MAXIMUM
SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SCATTERED TO
NUMEROUS MODERATE TO STRONG CONVECTION IS FROM 26N-29N BETWEEN
68W-72W. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT5/WTNT35 KNHC AND THE FULL FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC FOR MORE
DETAILS.

A TROPICAL WAVE IS ALONG 29W S OF 19N MOVING W NEAR 20 KT. THIS
WAVE COINCIDES WITH A BROAD AREA OF LOW-LEVEL CYCLONIC CURVATURE
FOCUSED AROUND A 1010 MB SURFACE LOW CENTERED ALONG THE WAVE
AXIS NEAR 11N. THE CIMSS WAVETRAK GUIDANCE DEPICTS A MAXIMUM
AREA OF 850 MB VORTICITY IN THE VICINITY OF THE WAVE AXIS AS
WELL. SATELLITE IMAGERY SHOWS AN AREA OF SCATTERED MODERATE/
ISOLATED STRONG CONVECTION LOCATED WELL W OF THE WAVE AXIS FROM
8N-12N BETWEEN 32W-37W. THIS CONVECTION IS BEING ENHANCED BY
UPPER LEVEL DIFFLUENCE ON THE SRN PERIPHERY OF AN ERN TROPICAL
ATLC UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED NEAR 17N35W.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 50W S OF 20N MOVING W NEAR 15 KT. WHILE
LOCATED BENEATH A WEAK UPPER LEVEL INVERTED TROUGH...ONLY A FEW
SCATTERED SHOWERS ARE NOTED IN THE VICINITY OF THE WAVE AXIS  N
OF THE ITCZ AXIS FROM 10N-15N BETWEEN 50W-56W.

TROPICAL WAVE IS ALONG 81W S OF 18N MOVING W NEAR 13 KT. THIS
WAVE REMAINS WITHIN AN AREA OF MAXIMUM DEEP LAYER MOISTURE AS
OBSERVED ON THE TOTAL PRECIPITABLE WATER IMAGERY...HOWEVER
DRY...SUBSIDENT NELY FLOW ALOFT DUE TO AN UPPER LOW CENTERED
NEAR 15N79W IS INHIBITING ANY SIGNIFICANT DEEP CONVECTION OR
SHOWER ACTIVITY.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 15N17W 12N27W 10N31W 12N48W
11N51W 10N61W. OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE
TROPICAL WAVES...SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS ALONG THE W AFRICA COAST FROM 10N-18N BETWEEN 13W-20W.
ELSEWHERE...WIDELY SCATTERED MODERATE CONVECTION AND SCATTERED
SHOWERS COVER THE AREA FROM 7N-12N BETWEEN 19W-27W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0300 UTC...A SURFACE TROUGH IS ANALYZED ACROSS THE ERN AND
S/CENTRAL GULF EXTENDING FROM 27N84W TO OVER THE WRN YUCATAN
PENINSULA NEAR 19N90W. AN AREA OF SCATTERED SHOWERS AND ISOLATED
TSTMS ARE ACROSS THE FAR ERN GULF AND FLORIDA PENINSULA N OF 25N
E OF 86W. THIS SURFACE TROUGH IS SUPPORTED BY AN UPPER LEVEL LOW
CENTERED OVER THE WRN FLORIDA PANHANDLE. AN UPPER LEVEL RIDGE
COVERS THE REMAINDER OF THE GULF ANCHORED BY AN UPPER LEVEL
ANTICYCLONE CENTERED OVER THE NRN YUCATAN PENINSULA. BETWEEN
THESE TWO UPPER LEVEL FEATURES...A ZONAL BAND OF MID/UPPER LEVEL
MOISTURE IS BEING TRANSPORTED EWD FROM E/CENTRAL MEXICO TO THE
NE GULF AND FLORIDA PENINSULA. AT THE SURFACE...A WEAK RIDGE OF
HIGH PRESSURE IS FORECAST TO REMAIN ACROSS THE NRN GULF WATERS
AHEAD OF THE NEXT FRONTAL BOUNDARY THAT IS EXPECTED TO MOVE INTO
THE NW GULF SUN.

CARIBBEAN SEA...
AN UPPER-LEVEL ANTICYCLONE IS CENTERED OVER THE YUCATAN
PENINSULA AND AN UPPER LEVEL LOW IS CENTERED NEAR 15N79W.
BETWEEN THESE TWO FEATURES...STRONG NELY UPPER LEVEL FLOW AND
DRY STABLE AIR IS FEEDING SW FROM WRN CUBA TO NICARAGUA AND
HONDURAS. THIS SUBSIDENT ATMOSPHERE IS INHIBITING ANY SIGNFICANT
CONVECTION OR SHOWER ACTIVITY. HOWEVER...SCATTERED SHOWERS ARE
OCCURRING ACROSS THE FAR SW CARIBBEAN AND PANAMA S OF 12N IN THE
VICINITY OF THE ITCZ AXIS THAT EXTENDS ALONG 9N ACROSS COSTA
RICA AND WRN PANAMA. THE ERN CARIBBEAN IS UNDER THE INFLUENCE OF
AN UPPER LEVEL RIDGE THAT EXTENDS FROM A CENTRAL ATLC
ANTICYCLONE CENTERED NEAR 25N63W. WATER VAPOR IMAGERY SHOWS
STRONG SUBSIDENCE AND AN IMPLIED DRY AIR MASS E OF 72W. AS A
RESULT...ONLY A FEW ISOLATED SHALLOW TRADE WIND SHOWERS ARE
NOTED OVER THE ERN CARIBBEAN WATERS AND LESSER ANTILLES.

ATLANTIC OCEAN...
ALL ATTENTION REMAINS FOCUSED ON TROPICAL STORM DANNY MOVING NNW
OVER PORTIONS OF THE SW NORTH ATLC. MOST OF THE DEEP CONVECTION
IS OCCURRING TO THE EAST OF THE CENTER COVERING THE AREA WITH
SCATTERED SHOWERS AND TSTMS FROM 25N-32N BETWEEN 66W-74W. THE
REMAINDER OF THE SW NORTH ATLC REMAINS FAIRLY TRANQUIL AS AN
UPPER LEVEL RIDGE IS CENTERED N OF THE NW BAHAMAS NEAR 29N78W.
FARTHER TO THE E...AN UPPER LEVEL LOW IS SPINNING OVER THE
CENTRAL ATLC NEAR 28N47W GENERATING WIDELY SCATTERED SHOWERS
FROM 24N-31N BETWEEN 42W-50W. THE REMAINDER OF THE CENTRAL AND
ERN ATLC ARE DOMINATED AT THE SURFACE BY A RIDGE OF HIGH
PRESSURE ASSOCIATED WITH THE AZORES-BERMUDA HIGH. ONE CENTER IS
LOCATED NE OF T.S. DANNY AS A 1022 MB HIGH NEAR 33N63W AND THE
OTHER A 1032 MB HIGH CENTERED NE OF THE AZORES NEAR 43N24W.

$$
HUFFMAN





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