[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 011237 AAA
TWDAT

TROPICAL WEATHER DISCUSSION...AMD
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN OCT 01 2006

UPDATE TO THE POSITION OF HURRICANE ISAAC

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...
AND METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...SPECIAL FEATURE...
HURRICANE ISAAC IS CENTERED NEAR 33.6N 60.2W AT 01/1200 UTC
MOVING NORTH-NORTHWEST AT 8 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 985 MB. MAXIMUM SUSTAINED WIND SPEED IS 75 KT WITH
GUSTS TO 90 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. ISAAC
STRENGTHENS SLIGHTLY AND THE RAGGED EYE CONTINUED TO BE PRESENT
OVERNIGHT. A BAND OF MODERATE/STRONG CONVECTION IS SURROUNDING
THE EYE. THE HURRICANE WILL BEGIN TO INTERACT WITH A LARGE
MID-LATITUDE TROUGH MOVING OFF THE EAST COAST OF THE UNITED
STATES AND WILL BECOME EXTRATROPICAL IN ABOUT 36 HOURS.
A TROPICAL STORM WATCH REMAINS IN EFFECT FOR THE AVALON
PENINSULA OF NEWFOUNDLAND...WHICH INCLUDES THE CITIES
OF CAPE RACE AND ST. JOHNS.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 38W S OF 21N MOVING W 10-15 KT. THE WAVE
HAS A WEAK INVERTED-V SIGNATURE AND IS EMBEDDED WITHIN DRY
AIR...THUS ONLY ISOLATED SHOWERS ARE NOTED.

TROPICAL WAVE IS ALONG 64W S OF 18N MOVING W 10-15 KT. WAVE IS
MOVING ACROSS THE EASTERN CARIBBEAN ENHANCING THE DEVELOPMENT OF
MODERATE TO STRONG CONVECTION OVER EASTERN VENEZUELA. THE WAVE
WILL PASS MAINLY SOUTH OF THE VIRGIN ISLANDS AND PUERTO RICO
TODAY. THE SAN JUAN DOPPLER RADAR IS SHOWING SCATTERED TO
NUMEROUS SHOWERS WITH EMBEDDED TSTMS MOVING ACROSS THE U.S.
VIRGIN ISLANDS AND THE EASTERN HALF OF PUERTO RICO.

TROPICAL WAVE IS ALONG 75W MOVING W AT AROUND 15 KT. THE WAVE IS
INTERACTING WITH A SURFACE TROUGH OVER THE BAHAMAS GENERATING
CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION BETWEEN
JAMAICA AND CUBA AND FROM 20N-25N BETWEEN 72W-75W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N14W 6N25W 7N36W 11N45W 9N60W.
SCATTERED MODERATE CONVECTION ARE FROM 2N-10N EAST OF 34W.
ISOLATED SHOWERS ARE ELSEWHERE.

...DISCUSSION...
GULF OF MEXICO...
DEEP LAYERED TROUGH LIES ALONG THE EASTERN U.S. AND THE E GULF
WITH THE BASE OF THE TROUGH REACHING WESTERN CUBA. BROAD UPPER
HIGH ANCHORED OVER CENTRAL AMERICA EXTENDS A RIDGE ACROSS THE
WESTERN HALF OF THE GULF INTO TEXAS. DRY AIR RESULTING IN
MODERATE TO STRONG SUBSIDENCE DOMINATES THE GULF EAST OF 90W AND
THE STATE OF FLORIDA WHILE ABUNDANT UPPER LEVEL MOISTURE IS
SPREADING EWD ACROSS MEXICO AND THE WEST GULF. AS OF 0900
UTC...A 1018 MB HIGH IS OVER THE FLORIDA PANHANDLE WITH A RIDGE
COVERING THE GULF. THIS IS GIVING THE MAJORITY OF THE AREA FAIR
CONDITIONS THIS MORNING. HIGH PRESSURE WILL BUILD OVER THE
SOUTHEAST U.S. MONDAY AND TUESDAY WITH INCREASING EASTERLY WINDS
ACROSS THE GULF.

CARIBBEAN SEA...
BROAD UPPER RIDGE ANCHORED OVER CENTRAL AMERICA AND IN THE E
PACIFIC REGION COVERS THE W CARIBBEAN W OF 73W WITH AN EXTENSION
OF THE RIDGE EXTENDING ACROSS E CUBA AND THE BAHAMAS INTO THE W
ATLC. A SURFACE TROUGH THAT EXTENDS ALONG 73/74W IS PRODUCING
HEAVY SHOWERS/SCATTERED THUNDERSTORMS OVER THE CENTRAL-SOUTHERN
BAHAMAS. AN UPPER LOW IN THE CARIBBEAN IS S OF THE MONA PASSAGE
NEAR 16N68W COVERING THE REMAINDER OF THE CARIBBEAN. AN UPPER
TROUGH EXTENDS FROM THE LOW TO THE ABC ISLANDS INTO VENEZUELA.
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE OVER THE E
CARIBBEAN E OF 70W ASSOCIATED WITH THE TROPICAL WAVE AND THE
UPPER LOW/TROUGH OVER THE AREA. MODERATE TRADE WINDS ARE BLOWING
ACROSS THE BASIN.

ATLANTIC OCEAN...
DEEP LAYERED TROUGH OVER THE E US EXTENDS INTO THE W ATLC W OF
73W. THE ASSOCIATED FRONTAL SYSTEM ENTERS THE AREA NEAR 32N68W
THEN CONTINUES SW TO THE NORTHERN BAHAMAS. A SURFACE PRE-FRONTAL
TROUGH EXTENDS FROM 26N72W TO 21N75W...GENERATING SCATTERED
MODERATE/ISOLATED STRONG CONVECTION FROM 20N-25N BETWEEN
72W-75W. ANOTHER SURFACE TROUGH RUNS FROM 27N64W TO 21N67W. A
DIFFLUENT PATTERN ALOFT IS ENHANCING THE SHOWER ACTIVITY
ASSOCIATED WITH THIS TROUGH. A CUT-OFF UPPER LOW IS IN THE
CENTRAL ATLC NEAR 20N48W DRIFTING WESTWARD.  BROAD UPPER RIDGE
COVERS THE E ATLC E OF 30W AND WESTERN AFRICA. A COLD FRONT IS
APPROACHING THE E-CENTRAL ATLC FROM THE NORTH. WIDELY SCATTERED
MODERATE CONVECTION IS AHEAD OF THE FRONT FROM 27N-31N BETWEEN
25W-35W.

$$
GR









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