[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 301044
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0945 UTC.

...SPECIAL FEATURES...

SUBTROPICAL STORM LAURA IS CENTERED NEAR 40.3N 49.0W AT 30/0900
UTC OR ABOUT 420 NM SSE OF CAPE RACE NEWFOUNDLAND MOVING N AT 11
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. LAURA IS EXPECTED TO
TURN TOWARD THE NNE WITH AN INCREASE IN FORWARD SPEED DURING THE
NEXT COUPLE OF DAYS WITH LITTLE CHANGE IN STRENGTH. LAURA IS
EMBEDDED WITHIN AN UPPER LOW/TROUGH AND OVER THE NEXT DAY OR SO
THE UPPER LOW IS EXPECTED TO WEAKEN AS LAURA MOVES INTO THE
WESTERLIES...AND LAURA STILL COULD BECOME A TROPICAL CYCLONE.
HOWEVER LAURA WILL BE MOVING OVER STEADILY DECREASING SEA SURFACE
TEMPERATURES DURING THE NEXT 36-48 HR. IN THE REGION...CLUSTERS
OF SCATTERED MODERATE CONVECTION ARE WITHIN 90/120 NM OF LINE
FROM 21N43W 26N37W TO BEYOND 32N30W ENHANCED BY THE UPPER LEVEL
FEATURES.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 30W/31W S OF 16N MOVING W 10-15 KT. WAVE
IS WELL DEFINED INVERTED-V CURVATURE OBSERVED IN THE LOW LEVEL
CLOUDS EMBEDDED WITHIN DEEP LAYERED MOISTURE AS INDICATED BY
MIMIC TPW ANIMATION. SMALL CLUSTERS OF SCATTERED MODERATE/STRONG
CONVECTION ARE FROM 11N-17N BETWEEN THE WAVE AXIS AND 35W.

TROPICAL WAVE IS ALONG 44W/45W FROM 10N-20N MOVING W 5-10 KT.
WELL DEFINED BROAD SWIRL IN THE LOW LEVEL CLOUDS IS ALONG THE
WAVE AXIS NEAR 15N. DEEP LAYER MOISTURE IS ALSO BROADLY
DISTRIBUTED AROUND WAVE AS INDICATED BY MIMIC TPW ANIMATION.
CLUSTERS OF SCATTERED MODERATE CONVECTION ARE WITHIN 90 NM OF
THE WAVE FROM 17N-20N.

TROPICAL WAVE IS ALONG 58W/59W S OF 16N MOVING W 10-15 KT. WAVE
POSITION IS BASED ON PERSISTENCE AS THE AREA IS UNDER DENSE HIGH
CLOUDS. NO ASSOCIATED SHOWERS/CONVECTION.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 11N12W 9N17W 11N30W 7N42W 7N60W.
SCATTERED MODERATE/STRONG CONVECTION IS MOVING OFF W AFRICA
WITHIN 120 NM ALONG THE COAST FROM 9N-15N. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM OF THE ITCZ
FROM 38W-41W. CLUSTERS OF SIMILAR CONVECTION ARE FROM 1N-4N E OF
3W ACROSS THE PRIME MERIDIAN.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER TROUGH DOMINATES THE CENTRAL US AND MOST OF THE GULF W
OF 84W WITH A COMPLICATED SYSTEM OVER THE E GULF CONSISTING OF A
SURFACE TROUGH EXTENDING FROM THE W ATLC ACROSS S FLORIDA NEAR
26N81W TO A 1011 MB LOW N OF THE YUCATAN NEAR 24N87W THEN S OVER
THE NW YUCATAN PENINSULA INTO THE E BAY OF CAMPECHE TO 19N93W.
ANOTHER SURFACE LOW IS DEVELOPING OVER THE YUCATAN AND WILL BE
MOVING N ALONG THE SURFACE TROUGH. BROAD UPPER RIDGE ANCHORED IN
THE W ATLC COVERS THE REMAINDER OF THE GULF DRAWING MOIST UPPER
FLOW N OVER THE AREA PROVIDING UPPER LEVEL SUPPORT SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS W OF A LINE FROM N FLORIDA NEAR
30N84W TO THE YUCATAN NEAR 21N87W AND WITHIN 75 NM ALONG THE W
COAST OF THE YUCATAN E OF 94W. THE GULF W OF 90W IS UNDER STRONG
SUBSIDENCE AND DRY UPPER AIR BUT ENOUGH LOW LEVEL MOISTURE
REMAINS TO CREATE LOW LEVEL CLOUDS WITH POSSIBLE ISOLATED
SHOWERS AND REMARKABLE CLEAR SKIES WITHIN 75 NM ALONG THE COAST
FROM PANAMA CITY FLORIDA TO LA PESCA MEXICO.

CARIBBEAN SEA...
WEAK UPPER LOW IS IN THE NW CARIBBEAN OVER THE CAYMAN ISLANDS
EMBEDDED WITHIN THE STRONGER UPPER RIDGE ANCHORED IN THE W ATLC
THAT COVERS THE REMAINDER OF THE CARIBBEAN. THE UPPER RIDGE IS
BRINGING STRONG SUBSIDENCE AND DRY STABLE AIR TO THE E CARIBBEAN
E OF 76W LEAVING THE W CARIBBEAN UNDER DEEP LAYERED MOISTURE AND
MOSTLY FAIR WEATHER WITH ONLY ISOLATED SHOWERS USHERED IN ON
MODERATE TRADE WINDS OVER THE E CARIBBEAN. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION COVER THE W CARIBBEAN W OF A
LINE FROM COLOMBIA NEAR 11N73W 16N76W TO CUBA NEAR 20N76W.

ATLANTIC OCEAN...
SUBTROPICAL STORM LAURA IS LOCATED N OF THE REGION...SEE SPECIAL
FEATURES ABOVE. BROAD UPPER RIDGE COVERS THE W ATLC ANCHORED
OVER THE BAHAMAS NEAR 24N76W AND A RIDGE AXIS EXTENDING ENE TO
31N53W DRAWING UPPER LEVEL MOISTURE FROM THE CARIBBEAN ACROSS
THE SE GULF OF MEXICO AND FLORIDA INTO THE W ATLC GENERATING
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS W OF LINE FROM CUBA
NEAR 22N79W ACROSS THE BAHAMAS TO 32N70W. THE SURFACE TROUGH IN
THE GULF OF MEXICO EXTENDS ACROSS S FLORIDA FROM NEAR PALM BEACH
INTO THE W ATLC TO 30N77W. BENEATH THE UPPER RIDGE IS A 1017 MB
SURFACE HIGH NEAR 26N60W. THE UPPER TROUGH ASSOCIATED WITH
SUBTROPICAL STORM LAURA EXTENDS INTO THE CENTRAL ATLC N OF 20N
FROM 35W-50W AND IS ENHANCING THE CONVECTION ASSOCIATED WITH
LAURA. AN UPPER TROUGH COVERS THE NE ATLC N OF 25N E OF 21W. THE
TROPICS IS DOMINATED BY THE TYPICAL E/W UPPER RIDGE ANCHORED
JUST W OF THE CAPE VERDE ISLANDS EXTENDING W TO NEAR 50W.

$$
WALLACE





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