[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 101740
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU MAY 10 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...

ANDREA HAS BEEN DOWNGRADED TO A SUBTROPICAL DEPRESSION. AT
10/1500 UTC...THE CENTER OF NEWLY DOWNGRADED ANDREA WAS LOCATED
NEAR 29.9N 79.9W OR ABOUT 100 MILES ESE OF JACKSONVILLE FLORIDA
AND 80 MILES NE OF DAYTONA BEACH FLORIDA. ANDREA IS GENERALLY
DRIFTING SOUTHWARD AND THIS SLOW MOTION IS EXPECTED OVER THE
NEXT 24 HOURS. ESTIMATED MINIMUM CENTRAL PRESSURE REPORTED BY
THE AIR FORCE PLANE IS 1003 MB. MAXIMUM SUSTAINED WINDS ARE NOW
30 KT WITH GUSTS TO 40 KT. CONTINUED GRADUAL WEAKENING IS
EXPECTED DURING THE NEXT 24 HOURS. SEE THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/ WTNT21 KNHC
FOR MORE DETAILS. MOSAIC DOPPLER RADAR FROM THE SE AND IR
IMAGERY CLEARLY SHOWS THE ANDREA IS STRUGGLING TODAY MAINTAINING
LITTLE CONVECTION WHICH IS MOSTLY CONFINED TO THE NE QUADRANT.
NWLY SHEAR AND DRY AIR EVIDENT ON WATER VAPOR IMAGERY ALONG WITH
RELATIVELY COOL SST'S ARE LIKELY THE CULPRITS FAVORING WEAKENING
OF THE SUBTROPICAL SYSTEM. A GENERAL SLOW SWD MOTION AND SPIN
DOWN TO A REMNANT LOW IS FORECAST OVER THE NEXT 24-48 HOURS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N11W 4N25W 3N34W 2N45W EQ50W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 180 NM N
AND 120 NM S OF THE AXIS BETWEEN 18W-28W. SCATTERED SHOWERS AND
TSTMS LIE ELSEWHERE WITHIN 120 NM OF AXIS.

...DISCUSSION...

GULF OF MEXICO...
DEEP LAYER N TO NW FLOW ON THE W SIDE OF ANDREA IS ENHANCING
SUBSIDENCE ABOVE THE ERN HALF OF THE GULF PROVIDING WIDESPREAD
CLEAR SKIES AND FAIR WEATHER. MOST OF THE SMOKE PLUMES
ORIGINATING FROM FIRES IN FLORIDA AND S GEORGIA APPEAR TO HAVE
THINNED OUT ACCORDING TO THE LATEST VIS IMAGERY.
HOWEVER...THERE IS STILL PROBABLY SOME AREAS OF REDUCED
VISIBILITY ESPECIALLY IN THE NE GULF. A WEAK 1017 MB SFC HIGH
PRES IS CENTERED ABOUT 180 NM S OF THE LOUISIANA COAST NEAR
27N92W. THE ASSOCIATED WEAK PRES PATTERN IS PRODUCING LIGHT
ANTICYCLONIC FLOW AROUND THIS FEATURE AIDING IN THE TRANQUIL
CONDITIONS. SEAS ARE ALSO OF LITTLE CONCERN WITH MOST
BUOYS/SHIPS NOW IN THE 1-3 FT RANGE. FAIRLY LIGHT WINDS AND
MOSTLY FAIR WEATHER IS EXPECTED TO CONTINUE THROUGH FRI AS WEAK
HIGH PRES REMAINS STATIONARY IN THE MID-GULF...THOUGH SCATTERED
SHOWERS/TSTMS ARE POSSIBLE IN THE NW PORTION AS THE UPPER LOW
CURRENTLY OVER N TEXAS APPROACHES THE REGION.

CARIBBEAN SEA...
LOW PRES TO THE N OF THE AREA ASSOCIATED WITH ANDREA ALONG WITH
A WEAK SFC TROUGH ALONG 79W N OF 15N IS ALLOWING WINDS TO BE
VERY LIGHT ACROSS THE W CARIB...GENERALLY NE 10 KT OR LESS.
TRADES INCREASE TO MORE TYPICAL VALUES...15-20 KT...AND VEER ELY
TO THE E OF THE TROUGH AS SFC RIDGING HAS BUILT INTO THE REGION
FROM THE NE. OVERALL...LITTLE CHANGE IS EXPECTED IN THIS SFC
FLOW PATTERN OVER THE NEXT DAY OR TWO. IN THE MID AND UPPER
LEVELS...THE PATTERN IS WNW TO ZONAL W OF 75W AND THEN BECOMES
SWLY E OF THERE IN RESPONSE TO A PRONOUNCED RIDGE OVER THE
CENTRAL ATLC. THE SWLY FLOW IS TRANSPORTING DEBRIS BROKEN HIGH
LEVEL CLOUDS FROM THE ITCZ ACROSS THE GREATER ANTILLES...ROUGHLY
BETWEEN 65W-77W. THERE COULD BE A FEW POCKETS OF DEEP MOISTURE
EMBEDDED IN THIS HIGH LEVEL MOISTURE PLUME BUT IT APPEARS VERY
ISOLATED IN NATURE. LITTLE CHANGE IN MOISTURE IS ANTICIPATED
THRU FRI AS THE UPPER PATTERN HOLDS.

ATLANTIC...
A LARGE UPPER TROUGH...IN WHICH SUBTROPICAL DEPRESSION ANDREA IS
EMBEDDED WITHIN...COVERS MUCH OF THE W ATLC. UPPER CONFLUENCE TO
THE S OF THE SYSTEM IS ENHANCING SUBSIDENCE W OF 73W. A NARROW
STRONG RIDGE LIES TO THE E OF THIS TROUGH WITH THE AXIS RUNNING
FAIRLY N-S ALONG 57W. UPPER DIFFLUENCE BETWEEN THESE FEATURES
AND LOW-LEVEL CONVERGENCE NEAR A DEVELOPING SFC TROUGH IS
GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS BETWEEN
60W-70W...MOST ORGANIZED N OF 23N. AT THE SFC...WINDS ARE
GENERALLY OUT OF THE E TO SE BETWEEN ANDREA AND A 1028 MB HIGH
NEAR 37N50W. SHIPS/BUOYS AND THIS MORNING'S QSCAT PASS INDICATE
THAT THE WINDS ARE FAIRLY LIGHT...10-15 KT ACROSS MOST OF THE
AREA...WITH THE EXCEPTION BEING CLOSER TO ANDREA'S CENTER. REFER
TO THE SPECIAL FEATURE SECTION FOR MORE DETAILS ON ANDREA.

FARTHER E...A VERTICALLY STACKED LOW PRES SYSTEM AND ITS
ASSOCIATED BROAD UPPER TROUGHING IS THE GENERAL MID/UPPER
PATTERN THEME. THE SFC LOW IS ANALYZED VERY WEAK...1020 MB DUE
TO ITS HIGH PRES ENVIRONMENT...NEAR 32N41W WITH A TROUGH HANGING
SW TO 29N53W. LOW-MID LEVEL CLOUDS AND ISOLATED SHOWERS ARE
POSSIBLE WITHIN 60 NM OF THE TROUGH AXIS. A MORE ORGANIZED SWATH
OF MOISTURE LIES A COUPLE HUNDRED NM TO THE S...NAMELY FROM
21N-26N BETWEEN 35W-42W. THIS ACTIVITY IS ASSOCIATED WITH UPPER
DIFFLUENCE TO THE E OF THE UPPER LOW CENTER WHICH IS LOCATED
NEAR 26N43W. ELSEWHERE...A 1026 MB SFC HIGH CENTERED NEAR 36N14W
IS IN CONTROL GENERATING A LARGE AREA OF MODERATE TRADES.
ANOTHER VERY NOTICEABLE FEATURE IN THE E ATLC IS THE DENSE
SAHARAN DUST WITH THE LEADING EDGE REACHING ABOUT 30W ACCORDING
TO THE UW-CIMSS SAL ANALYSIS AND THE HAZY LOOK ON VIS IMAGERY.
THIS VERY DRY AIR HAS ERODED ALL OF THE CLOUD COVER IN THE LOW
TO MID LAYER OF THE ATMOSPHERE.

$$
CANGIALOSI





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