[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 281152
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

TROPICAL STORM DANNY IS CENTERED NEAR 30.1N 75.2W AT 28/1200 UTC
OR ABOUT 310 NM S OF CAPE HATTERAS NORTH CAROLINA MOVING NNW AT
8 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB. MAXIMUM
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. SCATTERED TO
NUMEROUS MODERATE TO STRONG CONVECTION IS FROM 27N-31N BETWEEN
69W-74W. 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.

TROPICAL WAVE IS ALONG 32W 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 10N. 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 W OF THE WAVE AXIS FROM
6N-12N BETWEEN 34W-40W. THIS CONVECTION IS BEING ENHANCED BY
UPPER LEVEL DIFFLUENCE ON THE SRN PERIPHERY OF AN ERN TROPICAL
ATLC UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED NEAR 19N33W.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 52W S OF 19N MOVING W NEAR 15 KT. WHILE
LOCATED BENEATH A WEAK UPPER LEVEL INVERTED TROUGH AND MODERATE
TO STRONG SUBSIDENCE ALOFT...ONLY A FEW SCATTERED SHOWERS ARE
NOTED IN THE VICINITY OF THE WAVE AXIS N OF THE ITCZ AXIS FROM
10N-15N BETWEEN 50W-57W.

TROPICAL WAVE IS ALONG 82W S OF 16N MOVING W NEAR 13 KT. THIS
WAVE REMAINS WITHIN AN AREA OF MAXIMUM DEEP LAYER MOISTURE
ACROSS THE WRN CARIBBEAN AS OBSERVED ON THE TOTAL PRECIPITABLE
WATER IMAGERY...HOWEVER DRY...SUBSIDENT NELY FLOW ALOFT DUE TO
AN UPPER LOW CENTERED NEAR 16N79W IS INHIBITING ANY SIGNIFICANT
DEEP CONVECTION OR SHOWER ACTIVITY.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 14N17W 11N30W 9N34W 9N50W
10N53W 10N63W. OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE
TROPICAL WAVES...CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG
CONVECTION ARE FROM 10N-17N BETWEEN 16W-24W. ELSEWHERE...WIDELY
SCATTERED MODERATE CONVECTION AND SCATTERED SHOWERS ARE WITHIN
90 NM EITHER SIDE OF THE AXIS BETWEEN 39W-46W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0900 UTC...A SURFACE TROUGH IS ANALYZED ACROSS THE NE AND
S/CENTRAL GULF EXTENDING FROM 29N85W ALONG 25N87W TO OVER THE
ERN BAY OF CAMPECHE NEAR 20N92W. MOST OF THE EARLIER CONVECTION
NEAR THE SURFACE TROUGH HAS DISSIPATED WITH ONLY WIDELY
SCATTERED SHOWERS REMAINING NEAR TAMPA BAY FLORIDA AND AREAS
OFFSHORE TO THE SW COVERING AN AREA FROM 25N-28N BETWEEN
82W-84W. THIS SURFACE TROUGH IS SUPPORTED BY AN UPPER LEVEL
SHORTWAVE LOW CENTERED OVER SE ALABAMA. A WEAK 1011 MB SURFACE
LOW IS CENTERED NEAR THE NRN EXTENT OF THE SURFACE TROUGH NEAR
APALACHICOLA BAY WITH SCATTERED SHOWERS AND ISOLATED TSTMS N OF
29N BETWEEN 83W-86W. AN UPPER LEVEL RIDGE COVERS THE REMAINDER
OF THE GULF ANCHORED BY AN UPPER LEVEL ANTICYCLONE CENTERED OVER
THE NW YUCATAN PENINSULA AND ERN BAY OF CAMPECHE. BETWEEN THESE
TWO UPPER LEVEL FEATURES...A ZONAL BAND OF MID/UPPER LEVEL
MOISTURE IS BEING TRANSPORTED EWD FROM E/CENTRAL MEXICO TO THE
SE GULF AND FLORIDA PENINSULA. AT THE SURFACE...A WEAK RIDGE OF
HIGH PRESSURE ACROSS THE N/CENTRAL GULF IS FORECAST TO REMAIN
ACROSS THE NRN GULF WATERS THROUGH LATE SATURDAY INTO EARLY SUN
AHEAD OF THE NEXT FRONTAL BOUNDARY THAT IS EXPECTED TO MOVE INTO
THE NW GULF LATE SUN.

CARIBBEAN SEA...
AN UPPER-LEVEL ANTICYCLONE IS CENTERED OVER THE YUCATAN
PENINSULA AND AN UPPER LEVEL LOW IS CENTERED NEAR 16N79W IN THE
WRN CARIBBEAN. 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 SIGNIFICANT CONVECTION OR SHOWER ACTIVITY W OF 80W.
HOWEVER...SCATTERED SHOWERS ARE OCCURRING ACROSS THE FAR SW
CARIBBEAN AND PANAMA S OF 11N IN THE VICINITY OF THE BASE OF THE
UPPER LOW AND PROXIMITY TO THE ITCZ AXIS THAT EXTENDS ALONG 9N
ACROSS NRN COLOMBIA...PANAMA AND COSTA RICA. THE ERN CARIBBEAN
IS UNDER THE INFLUENCE OF AN UPPER LEVEL RIDGE THAT EXTENDS FROM
A CENTRAL ATLC ANTICYCLONE CENTERED NEAR 23N63W. 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 MOVING WWD OVER THE ERN CARIBBEAN WATERS AND
LESSER ANTILLES.

ATLANTIC OCEAN...
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 27N-31N BETWEEN 69W-74W. THE
REMAINDER OF THE SW NORTH ATLC REMAINS FAIRLY TRANQUIL AS AN
UPPER LEVEL RIDGE AND ASSOCIATED 1015 MB SURFACE HIGH IS
CENTERED NEAR ORLANDO FLORIDA. FARTHER TO THE E...AN UPPER LEVEL
LOW IS SPINNING OVER THE CENTRAL ATLC NEAR 29N46W GENERATING
WIDELY SCATTERED SHOWERS FROM 25N-32N BETWEEN 42W-49W. 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 ENE OF T.S. DANNY AS
A 1021 MB HIGH NEAR 32N61W AND THE OTHER A 1031 MB HIGH CENTERED
NE OF THE AZORES NEAR 42N22W.

$$
HUFFMAN





This weather bulletin was brought to you by:
www.nashvilleweather.net