[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 190001
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON AUG 18 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
2345 UTC.

...SPECIAL FEATURES...
T.S. FAY HEADED NORTHWARD TOWARD THE SOUTHWEST FLORIDA COAST. AT
19/0000 UTC...THE CENTER OF TROPICAL STORM FAY IS CENTERED NEAR
25.0N 81.9W OR ABOUT 90 NM...170 KM...SOUTH OF NAPLES FLORIDA
MOVING TOWARD THE NORTH NEAR 8 KT. THIS GENERAL MOTION IS
EXPECTED TO CONTINUE TONIGHT AND TUESDAY. ON THE FORECAST
TRACK...THE CENTER OF FAY WILL CROSS THE SOUTHWESTERN COAST OF
FLORIDA ON TUESDAY. ESTIMATED MINIMUM CENTRAL PRESSURE IS 998
MB. MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH HIGHER GUSTS.
STRENGTHENING IS EXPECTED TONIGHT AND TUESDAY...AND FAY IS
FORECAST TO BE AT OR NEAR HURRICANE STRENGTH AS IT APPROACHES
THE SOUTHWESTERN COAST OF FLORIDA. PLEASE SEE THE LATEST NHC THE
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
AND PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/ WTNT31
KNHC FOR MORE DETAILS. SATELLITE...RADAR...AND AIRCRAFT DATA
INDICATE THAT FAY HAS BECOME BETTER ORGANIZED THIS EVENING. THE
CONVECTIVE BANDING HAS INCREASED AROUND THE CENTER...AND THE
RADIUS OF MAXIMUM WINDS HAS CONTRACTED TO ABOUT 30 N MI. IN
ADDITION...THE CENTRAL PRESSURE HAS FALLEN TO 998 MB. FAY IS
EXPECTED TO PRODUCE ADDITIONAL RAINFALL ACCUMULATIONS OF 3 TO 5
INCHES OVER THE CENTRAL PORTION OF CUBA...WITH STORM TOTAL
AMOUNTS OF 20 INCHES BEING POSSIBLE.  THESE RAINS COULD CAUSE
LIFE THREATENING FLASH-FLOODS AND MUDSLIDES.  RAINFALL
ACCUMULATIONS OF 4 TO 8 INCHES...WITH MAXIMUM STORM TOTAL
AMOUNTS OF 10 INCHES...ARE POSSIBLE FOR THE FLORIDA KEYS AND THE
CENTRAL AND SOUTHERN FLORIDA PENINSULA.  RAINFALL ACCUMULATIONS
OF 3 TO 5 INCHES ARE POSSIBLE IN THE NORTHWESTERN BAHAMAS.

...TROPICAL WAVES...
A TROPICAL WAVE IS IN THE E TROPICAL ATLC ALONG 35W S OF 17N. A
1010 MB LOW IS ANALYZED ALONG THE WAVE AXIS NEAR 13N. SCATTERED
SHOWERS AND TSTMS ARE WITHIN 90 NM N SEMICIRCLE OF THE LOW
CENTER. SOME BANDING FEATURE IS NOTED ON SATELLITE IMAGERY. THIS
SYSTEM HAS CONTINUED TO BECOME BETTER ORGANIZED THIS EVENING AND
ADDITIONAL DEVELOPMENT INTO A POSSIBLE TROPICAL CYCLONE  CAN BE
EXPECTED DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD OR
WEST-NORTHWESTWARD AT ABOUT 15 MPH. ANOTHER AREA OF CLOUDINESS
WITH MODERATE CONVECTION IS WITHIN 530 NM SE OF THE ABOVE
MENTIONED SFC LOW. THE CLOUD PATTERN IS ALSO EXHIBITING CYCLONIC
CIRCULATION AS OBSERVED ON RECENT SATELLITE IMAGERY. WILL WAIT
FOR MORE SHIP...SCATTEROMETER AND SATELLITE DATA BEFORE PLACING
ANOTHER SFC LOW OUT THERE. CLUSTERS OF SCATTERED MODERATE
CONVECTION ARE FROM 11N-14.5N BETWEEN 31W-38W RELATED TO THE
TROPICAL WAVE/LOW.

A TROPICAL WAVE HAS ENTERED THE EASTERN CARIBBEAN. ITS AXIS
REMAINS TILTED FROM 21N59W TO 11N63W. A WEAK INVERTED-V
SIGNATURE IS NOTED ON SAT IMAGERY WITH A SMALL AREA OF SHOWERS
MOVING WWD AHEAD OF THE WAVE AXIS. THIS SHOWER ACTIVITY IS
APPROACHING THE ABC ISLANDS. WAVE REMAINS DISTORTED DUE TO AN
UPPER LOW TO THE N OF THE WAVE LINE. SCATTERED SHALLOW SHOWERS
ARE MOVING THROUGH THE LEEWARD ISLANDS.

...THE ITCZ...
THE ITCZ IS CENTERED ALONG 14N16W 10N25W 12N33W 10N45W 8N60W.
OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVE...SCATTERED MODERATE CONVECTION IS WITHIN FROM 8N-10N EAST
OF 18W TO THE AFRICAN COAST. SIMILAR CONVECTION IS FROM 6N-10N
BETWEEN 25W-31W...AND FROM 7N-11N BETWEEN 56W-58W.

...DISCUSSION...

GULF OF MEXICO...
ALL THE ATTENTION REMAINS FOCUSED ON TROPICAL STORM FAY THAT
MADE LANDFALL OVER KEY WEST FLORIDA AT 3 PM EDT. AT THAT TIME...
THE WINDS WENT CALM INDICATING THE PRESENCE OF THE STORM CENTER.
SEE SPECIAL FEATURES ABOVE. A BROAD UPPER TROUGH OVER THE ERN
U.S. DIGS INTO THE NE PORTION OF THE GULF AND EXTENDS TO AN
UPPER-LEVEL LOW THAT CONTINUES TO SPIN BETWEEN WESTERN CUBA AND
THE YUCATAN PENINSULA. THE REMAINDER OF THE GULF REGION IS UNDER
THE INFLUENCE OF A RIDGE ANCHORED ON AN UPPER-LEVEL HIGH NOW
LOCATED OVER THE SOUTHERN BAJA PENINSULA. T.S. FAY IS ENTERING
THE AREA BETWEEN THE UPPER-LEVEL TROUGH PREVIOUSLY MENTIONED AND
A SUBTROPICAL RIDGE OVER THE W ATLC THAT COVERS THE STATE OF
FLORIDA AND THE E GULF. DOPPLER RADAR SHOWS THE SPIRAL BANDS
ASSOCIATED WITH THE CYCLONIC CIRCULATION OF FAY OVER SOUTH
FLORIDA AND THE KEYS. THE OUTER BAND IS REACHING THE AREA OF
LAKE OKEECHOBEE. MAXIMUM RAINFALL AMOUNTS SO FAR HAVE BEEN FROM
1 TO 3 INCHES ACROSS PARTS OF MIAMI-DADE COUNTY, ESPECIALLY
WHERE THE SPIRAL BANDS HAVE PERSISTED FOR A FEW HOURS. SCATTERED
SHOWERS AND TSTMS ARE ALSO ACROSS THE N GULF STATE ASSOCIATED
WITH A FRONTAL BOUNDARY THAT REMAINS NEARLY STATIONARY OVER THAT
REGION. A WEAK 1014 MB HIGH IS LOCATED NEAR 27N89W AT 2100 UTC.
CONDITIONS OVER THE FAR ERN GULF...INCLUDING THE FLORIDA
PENINSULA WILL CONTINUE TO DETERIORATE AS T.S. FAY MOVES TOWARD
THE NORTH TONIGHT AND TUE. ACCORDING TO THE OFFICIAL FORECAST
TRACK...A SECOND LANDFALL IS EXPECTED ALONG THE WEST COAST OF
FLORIDA TOMORROW.

CARIBBEAN SEA...
T.S. FAY CONTINUES TO MOVE AWAY FROM THE CARIBBEAN SEA BUT A
FEEDER BAND PERSISTS OVER CENTRAL CUBA WHERE RAINFALL AMOUNTS
GREATER THAN 6 INCHES HAVE BEEN REPORTED...PARTICULARLY OVER THE
MOUNTAINOUS TERRAIN OF THE MUNICIPALITY OF PLACETA CUBA. SEE
SPECIAL FEATURES ABOVE FOR MORE DETAILS ON T.S. FAY. A BROAD
UPPER HIGH IS CENTERED NE OF THE BAHAMA ISLANDS AND EXTENDS A
RIDGE THROUGH ERN CUBA AND JAMAICA INTO THE CENTRAL CARIBBEAN .
THIS DIFFLUENT PATTERN ALOFT IS SUPPORTING THE CONVECTION
ASSOCIATED WITH T.S. FAY ACROSS CENTRAL CUBA AND THE N CENTRAL
CARIBBEAN SEA. AN UPPER LOW IN THE W/CENTRAL ATLC EXTENDS WEAK
UPPER TROUGHING OVER THE NE CARIBBEAN WITH AXIS CROSSING THE
VIRGIN ISLANDS. MOST OF THE BASIN IS DOMINATED BY MODERATE TO
STRONG SUBSIDENCE AND DRY STABLE AIR DUE TO THE INFLUENCE OF THE
ABOVE MENTIONED RIDGE. THE ITCZ AXIS EXTENDS FROM COLOMBIA INTO
THE ERN PACIFIC REGION NEAR THE PANAMA/COSTA RICA BORDER
GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS OVER THE FAR SW
CARIBBEAN S OF 10N BETWEEN COLOMBIA AND COSTA RICA. SCATTERED
SHOWERS AND ISOLATED TSTMS ARE ALSO SEEN OVER PARTS OF HONDURAS
AND NICARAGUA. UPPER DIFFLUENCE IS SUPPORTING THIS ACTIVITY. A
SFC TROUGH IS ANALYZED FROM WESTERN CUBA TO THE GULF OF
HONDURAS. AN EARLIER QSCAT PASS SHOWED SLY WINDS OF 20-25 KT
WITHIN 200 NM E OF THE TROUGH AXIS AND N OF 19N. THESE WINDS ARE
PART OF THE FAY'S CIRCULATION AND ARE EXPECTED TO DIMINISH LATE
TONIGHT THROUGH TUE. A TROPICAL WAVE IS OVER THE E CARIBBEAN.
SEA ABOVE.

ATLANTIC OCEAN...
THE FRONTAL BOUNDARY OVER THE SE U.S. EXTENDS FROM THE W ATLC N
OF THE REGION...AND ALONG WITH T.S. FAY IS GENERATING SCATTERED
SHOWERS AND THUNDERSTORMS OVER THE W ATLC W OF 72W AND ACROSS
THE NW BAHAMAS. AN UPPER HIGH CENTERED NEAR 26N71W IS PROVIDING
AMPLE UPPER DIFFLUENCE TO SUSTAIN THIS CONVECTIVE ACTIVITY. A
LARGE UPPER LOW IS LOCATED IN THE W/CENTRAL ATLC NEAR 24N62W
EXTENDING UPPER TROUGHING OVER THE NE CARIBBEAN. A SURFACE
TROUGH IS TO THE E OF THE UPPER LOW EXTENDING FROM 31N56W TO
24N58W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
WITHIN 150 NM EAST OF THE SURFACE TROUGH. AN UPPER HIGH IS TO
THE E NEAR 31N48W. ANOTHER UPPER-LEVEL LOW IS CENTERED NEAR
25N40W WITH A WEAKER SECOND ONE JUST S OF THE MADEIRA ISLANDS.
MODERATE SUBSIDENCE AND SOMEWHAT DRY STABLE AIR COVERS THE ATLC
BETWEEN 40W-60W AND N OF THE ITCZ TO 24N GIVING THE AREA MOSTLY
FAIR WEATHER CONDITIONS. AT THE SURFACE...A RIDGE ANCHORED BY A
SERIES OF HIGHS N OF THE REGION COVERS MOST OF THE FORECAST
AREA...BUT MAINLY E OF 50W.

$$
GR


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