[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 010003
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE SEP 30 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
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM LAURA IS CENTERED NEAR 42.3N 48.6W AT 30/2100 UTC
OR ABOUT 325 NM SE OF CAPE RACE NEWFOUNDLAND MOVING N AT 12 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 996 MB. MAXIMUM SUSTAINED
WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. PLEASE SEE THE LATEST
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32
KNHC FOR MORE DETAILS. TROPICAL STORM FORCE WINDS EXTEND OUTWARD
UP TO 200 NM FROM THE CENTER OF LAURA. LAURA IS EXPECTED TO
ACCELERATE AND TURN TOWARD THE NNE TONIGHT. LAURA WILL BEGIN TO
LOSE TROPICAL CHARACTERISTICS TONIGHT AND IS EXPECTED TO BECOME
EXTRATROPICAL ON WEDNESDAY. ADDITIONALLY...LAURA IS EXPECTED TO
GRADUALLY WEAKEN DURING THE NEXT COUPLE OF DAYS. ISOLATED
MODERATE CONVECTION IS FROM 42N-44N BETWEEN 45W-50W.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 33W/34W S OF 19N MOVING W NEAR 15 KT.
SATELLITE IMAGERY DEPICTS INVERTED-V CLOUD PATTERN ALONG WAVE
AXIS. ISOLATED MODERATE CONVECTION IS WITHIN 120 NM OF WAVE AXIS
N OF 12N...AND SCATTERED MODERATE CONVECTION IS WITHIN 180 NM OF
WAVE AXIS S OF 10N. SAHARAN DUST CONTINUES MOVING TO THE W IN
THE WAKE OF THE WAVE N OF 15N.

TROPICAL WAVE IS ALONG 45W/46W FROM 12N-22N MOVING W 5-10 KT.
SATELLITE IMAGERY DEPICTS INVERTED-V CLOUD PATTERN ALONG WAVE
AXIS...WITH SURFACE WINDS VEERING UPON WAVE PASSAGE. ISOLATED
MODERATE CONVECTION IS FROM 13N-19N BETWEEN 43W-45W.

TROPICAL WAVE IS ALONG 61W S OF 16N MOVING W 10-15 KT. SCATTERED
SHOWERS ARE OCCURRING WITHIN 150 NM OF WAVE AXIS S OF 15N.
SURFACE WIND OBSERVATIONS ACROSS THE LESSER ANTILLES DEPICT WEAK
COUNTERCLOCKWISE CURVATURE IN SURFACE FLOW NEAR WAVE AXIS.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 11N13W 10N20W 11N31W 9N40W
9N59W. SCATTERED MODERATE CONVECTION IS MOVING TO THE W OVER
W AFRICA FROM 7N-13N BETWEEN 10W-17W...AFFECTING GAMBIA AND
GUINEA-BISSAU. SCATTERED MODERATE CONVECTION IS FROM 7N-14N
BETWEEN 20W-24W. ISOLATED MODERATE CONVECTION IS FROM 5N-9N
BETWEEN 41W-49W.

...DISCUSSION...

GULF OF MEXICO...
DEEP UPPER TROUGH OVER THE E CONUS EXTENDS SOUTHWARD ACROSS MUCH
OF THE GULF. STRONG AND MOIST SW FLOW ALOFT E OF THE TROF AXIS
IS PROVIDING UPPER SUPPORT FOR NUMEROUS SHOWERS AND
THUNDERSTORMS OVER THE FAR SE AND S GULF...FROM S FLORIDA TO THE
YUCATAN PENINSULA AND ALSO OVER CUBA. THIS ACTIVITY IS FURTHER
BEING ENHANCED BY LOW LEVEL CONVERGENCE ASSOCIATED WITH SEVERAL
SURFACE FEATURES INCLUDING A SURFACE LOW JUST OFF THE W COAST OF
FL NEAR 26N83W...ANOTHER SURFACE LOW JUST N OF THE YUCATAN
PENINSULA NEAR 22N89W...A SURFACE TROUGH THAT CONNECTS THESE TWO
LOWS...AND A SURFACE TROUGH THAT TRAILS S FROM THE LOW NEAR THE
YUCATAN PENINSULA TO NEAR 17N90W. DEEP DRY AIR IN THE BASE OF
THE UPPER TROUGH AND SUBSIDENCE W OF THE UPPER TROUGH AXIS ARE
LIMITING CONVECTIVE ACTIVITY IN THE CENTRAL AND W GULF.

CARIBBEAN SEA...
AN UPPER RIDGE EXTENDS INTO THE CENTRAL CARIBBEAN ANCHORED BY AN
UPPER HIGH OVER THE SW ATLANTIC NEAR 22N66W. STABLE CONDITIONS
AND DRY AIR BENEATH THIS RIDGE ARE RESULTING IN FAIR WEATHER
ACROSS MUCH OF THE CENTRAL AND E CARIBBEAN...WITH ISOLATED
SHOWERS FROM 16N-18N BETWEEN 69W-72W APPROACHING S HISPANIOLA.
THE UPPER TROUGH OVER THE GULF IS BEGINNING TO BRING MORE UPPER
SW FLOW TO THE W CARIBBEAN. THIS FLOW IS DIFFLUENT OVER THE W
CARIBBEAN...WHERE ISOLATED MODERATE CONVECTION IS OCCURRING FROM
16N-22N BETWEEN 81W-87W...WITH SCATTERED MODERATE CONVECTION
OVER THE ADJACENT LAND AREAS INCLUDING HONDURAS...BELIZE...AND
THE YUCATAN PENINSULA. UPPER SUPPORT FROM THE UPPER TROUGH IS
ALSO ENHANCING SHOWERS AND THUNDERSTORMS OVER MUCH OF CUBA.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION HAS DEVELOPED OVER
N COLOMBIA AND N VENEZUELA NEAR THE ITCZ...AND THIS CONVECTION
IS PROPAGATING TO THE N NEAR THE ADJACENT CARIBBEAN WATERS.

ATLANTIC OCEAN...
TROPICAL STORM LAURA IS LOCATED N OF THE REGION...SEE SPECIAL
FEATURES SECTION ABOVE. THE DEEP UPPER TROUGH OVER THE E CONUS
IS BRINGING STRONG AND MOIST SW FLOW ALOFT TO THE W ATLANTIC.
THIS IS PROVIDING THE UPPER SUPPORT FOR SHOWERS AND ISOLATED
THUNDERSTORMS OVER THE SW ATLANTIC FROM 25N-32N W OF 72W...
INCLUDING S FLORIDA AND THE BAHAMAS. THIS ACTIVITY IS FURTHER
BEING ENHANCED BY A SURFACE TROUGH THAT EXTENDS FROM 32N73W TO
S FLORIDA NEAR 28N80W. E OF THESE FEATURES...A LARGE UPPER HIGH
COVERS THE CENTRAL ATLANTIC AND IS CENTERED NEAR 23N65W. DRY
AIR...SUBSIDENCE...AND STABLE CONDITIONS IN THE VICINITY OF THIS
HIGH ARE RESULTING IN FAIR WEATHER OVER MUCH OF THE CENTRAL
ATLANTIC. HOWEVER...THE CORRESPONDING SURFACE HIGH HAS WEAKENED
WITH THE APPROACH OF THE UPPER AND SURFACE TROUGH FURTHER TO THE
W. MOISTURE AND CLOUDINESS ARE STREAMING AROUND THE UPPER HIGH N
OF 28N BETWEEN 60W-67W. A SURFACE TROUGH EXTENDS FROM 32N58W TO
29N60W AND IS NE OF THE UPPER HIGH...FURTHER ENHANCING SOME OF
THE CLOUDINESS. A BROAD UPPER TROUGH WITH LIMITED MOISTURE IS N
OF 23N BETWEEN 33W-54W...WHICH SHARPENS FROM 13N-23N BETWEEN
47W-54W. THE TROPICAL ATLANTIC IS DOMINATED BY AN E/W UPPER
RIDGE ALONG 16N EXTENDING FROM AN UPPER HIGH NEAR THE CAPE VERDE
ISLANDS TO NEAR 48W. A SURFACE RIDGE EXTENDS SOUTHWARD OVER THE
E ATLC FROM A 1031 MB SURFACE HIGH NEAR 44N25W.

$$
COHEN

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