[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 091817
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED MAY 09 2007

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...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...

SUBTROPICAL STORM ANDREA IS CENTERED NEAR 30.8N 79.3W AT 09/1500
UTC OR 140 NM SE OF SAVANNAH GEORGIA MOVING W AT 3 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB.  MAXIMUM
SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT.  SEE THE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/
WTNT21 KNHC FOR MORE DETAILS.  AN AIR FORCE RECONNAISSANCE PLANE
HAS INVESTIGATED ANDREA OFF THE SOUTHEAST U.S. COAST.  THE
INITIAL LEG OF THE MISSION WAS FLOWN AT 300 MB FROM WEST TO EAST
OVER THE CIRCULATION CENTER...AND SEVERAL DROPSONDES WERE
RELEASED.  THE TEMPERATURE PROFILES REVEALED A RATHER FLAT
THERMAL CROSS-SECTION...NOT INDICATING A DISCERNIBLE WARM OR
COLD CORE AT ANY VERTICAL LEVEL.  THE WIND PROFILES...
HOWEVER...SHOWED WINDS INCREASING WITH HEIGHT IN THE WESTERN
HALF OF THE CIRCULATION AND DECREASING WITH HEIGHT IN THE
EASTERN HALF.  GOES IMAGERY INDICATES THAT...COMPARED TO
YESTERDAY...THE THUNDERSTORM ACTIVITY HAS CONSOLIDATED CLOSER TO
THE CENTER...BUT PRIMARILY IN THE EASTERN SEMICIRCLE.  THERE IS
ALSO A SLIGHT HINT OF UPPER-LEVEL OUTFLOW WHICH WAS COMPLETELY
ABSENT YESTERDAY.  SUBSEQUENTLY HOWEVER...CONVECTION HAS
DECREASED IN THE PAST HOUR.  ISOLATED MODERATE CONVECTION IS
WITHIN 120 NM OF THE CENTER.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N12W 6N20W 1N40W EQ50W.  WIDELY
SCATTERED MODERATE CONVECTION IS FROM 1N-7N BETWEEN 18W-28W.
SCATTERED MODERATE CONVECTION IS FROM 3S-3N BETWEEN 28W-40W.
WIDELY SCATTERED MODERATE CONVECTION IS ALONG THE COAST OF SOUTH
AMERICA FROM 3S-3N BETWEEN 40W-50W.

...DISCUSSION...

GULF OF MEXICO...
ANDREA IS ADVECTING DRY 10-15 KT NLY SURFACE WINDS OVER THE ERN
GULF OF MEXICO.  SMOKE PLUMES ORIGINATING FROM FIRES IN FLORIDA
AND S GEORGIA CONTINUE TO AFFECT THE E/SE GULF OF MEXICO AND
FLORIDA.  VISIBILITIES ARE 3-5 NM AT TIMES IN SOUTH FLORIDA AND
THE KEYS...S OF 27N.  SEAS ARE MOSTLY IN THE 2-4 FT RANGE.
FURTHER W...A 1017 MB HIGH IS CENTERED S OF LOUISIANA NEAR
28N92W PRODUCING FAIR WEATHER AND ANTICYCLONIC 5-10 KT WINDS.
IN THE UPPER LEVELS...A TROUGH IS OVER THE E GULF E OF 88W WITH
STRONG SUBSIDENCE...WHILE A RIDGE IS OVER THE W GULF W OF 88W
WITH SIGNIFICANT UPPER LEVEL MOISTURE.  RIDGE AXIS IS ALONG
95W.  EXPECT THE CENTER OF ANDREA TO COME CLOSER TO THE FLORIDA
COAST AND THUS PRODUCE SOME CONVECTION OVER THE NE PART OF THE
STATE LATER TONIGHT.  ALSO EXPECT SELY RETURN FLOW TO PRODUCE
SCATTERED SHOWERS ALONG THE COAST OF NE MEXICO AND S TEXAS.

CARIBBEAN SEA...
WEAK PRES PATTERN IN THE WRN CARIB CONTINUES TO PRODUCE LIGHT NE
WINDS GENERALLY IN THE 5-10 KT RANGE. THE TRADES INCREASE TO 15
KT IN THE E CARIB AS RIDGING FROM THE AZORES HIGH HAS TIGHTENED
THE GRADIENT.  SCATTERED MODERATE CONVECTION IS OVER HISPANIOLA
FROM 15N-20N BETWEEN 68W-75W.  WIDELY SCATTERED MODERATE
CONVECTION IS ALSO ALONG THE COAST OF PANAMA FROM 9N-11N BETWEEN
79W-82W.  IN THE UPPER LEVELS...A TROUGH IS OVER THE W CARIBBEAN
W OF 72W WITH STRONG SUBSIDENCE.  A RIDGE IS OVER THE E
CARIBBEAN E OF 72W WITH SIGNIFICANT UPPER LEVEL MOISTURE.
EXPECT LITTLE CHANGE OVER THE NEXT 24 HOURS.

ATLANTIC...
SEE THE SPECIAL SECTION ABOVE ABOUT ANDREA.  FURTHER E...
NUMEROUS TSTMS ARE OVER THE DISCUSSION AREA N OF 20N BETWEEN
65W-70W MOSTLY DUE TO UPPER DIFFLUENCE BETWEEN THE VERTICALLY
STACKED ANDREA OFF THE SOUTHEAST U.S. AND UPPER LEVEL RIDGING
EXTENDING N ALONG 60W.  A SURFACE TROUGH IS OVER THE CENTRAL
ATLANTIC ALONG 32N41W 26N50W.  SCATTERED SHOWERS ARE WITHIN 30
NM OF THE TROUGH AXIS.  A 1026 MB HIGH IS JUST W OF PORTUGAL
NEAR 40N14W PRODUCING WIDESPREAD FAIR WEATHER AND MODERATE
TRADES ACROSS THE CENTRAL AND ERN ATLANTIC.  SAHARAN DUST HAS
SPREAD TO 40W...ALTHOUGH IS THICKEST E OF 30W.  THIS DUST IS
ERODING THE TYPICAL STRATOCUMULUS DECK ASSOCIATED WITH THE
SUBTROPICAL RIDGE.

$$
FORMOSA




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