[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 090605
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0545 UTC.

...SPECIAL FEATURE...

A LARGE 1000 MB NON-TROPICAL LOW PRESSURE SYSTEM...CENTERED NEAR
31N78.5W...OR ABOUT 150 NM EAST OF JACKSONVILLE FLORIDA AND
ABOUT 140 NM SOUTH-SOUTHEAST OF CHARLESTON SOUTH CAROLINA...HAS
BEEN MOVING SLOWLY WESTWARD AT 5 TO 10 MPH. THIS SYSTEM IS
PRODUCING GALE FORCE CONDITIONS WITH SHIP AND BUOY OBSERVATIONS
AND A RECENT QUIKSCAT PASS SHOWING MAX WINDS IN THE 35-45 KT
RANGE. THESE WINDS ARE PRODUCING HIGH SEAS AND HEAVY SURF ALONG
THE SOUTHEAST U.S. COAST AND THE BAHAMAS. MODERATE NW SWELL IS
ALSO PROPAGATING WELL AWAY FROM THE STORM...WITH THE NEW 41043
BUOY NORTH OF PUERTO RICO SHOWING STEADILY INCREASING LONGER
PERIOD SWELL OVER THE LAST SEVERAL HOURS. WAVES WILL SLOWLY
SUBSIDE FROM W TO E OVER THE NEXT COUPLE OF DAYS. THE SYSTEM HAS
CHANGED LITTLE SINCE THIS EVENING...AND NO SIGNIFICANT
STRENGTHENING IS EXPECTED.  THE LOW IS BEING MONITORED FOR SIGNS
OF TROPICAL OR SUBTROPICAL CYCLONE DEVELOPMENT...AND AN AIR
FORCE RESERVE RECONNAISSANCE AIRCRAFT IS SCHEDULE TO INVESTIGATE
THE SYSTEM TOMORROW MORNING. PLEASE REFER TO THE HIGH SEAS
FORECASTS AND STATEMENTS FROM LOCAL WEATHER SERVICE OFFICES FOR
MORE DETAILS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 9N13W 6N20W 3N30W 2N40W 2N50W.
NUMEROUS MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 90NM
EITHER SIDE OF THE AXIS BETWEEN 21W-36W. SIMILAR
CONVECTION...POSSIBLY ASSOCIATED WITH A LOW AMPLITUDE TROPICAL
WAVE...IS S OF 4N BETWEEN 36W-43W.

...DISCUSSION...

GULF OF MEXICO...
THE SPECIAL FEATURE DISCUSSED ABOVE IS PRODUCING ABUNDANT
SUBSIDENCE AND ADVECTING DRIER AND COOLER AIR ACROSS THE CENTRAL
AND ERN GULF. SMOKE PLUMES ORIGINATING FROM FIRES IN FLORIDA AND
S GEORGIA CONTINUE TO AFFECT THE E/SE GULF AND FLORIDA. THIS HAS
BEEN PRODUCING VISIBILITIES OF 3-5 SM AT TIMES IN SOUTH FLORIDA
AND THE KEYS. SFC WINDS ARE 5-15 KT FROM THE N TO NW IN THE ERN
GULF AROUND THE SPECIAL FEATURE. THESE WINDS VEER MORE E TO SE
THE WRN GULF AROUND A HIGH PRES CENTER FORMING JUST OFF THE
LOUISIANA COAST. SEAS ARE MOSTLY IN THE 2-4 FT RANGE...EXCEPT IN
THE 5-7 FT RANGE S OF 28N W OF 90W DUE TO A MORE FAVORABLE FETCH
S OF HIGH PRES. WINDS AND SEAS EXPECTED TO GRADUALLY RELAX
FURTHER THROUGH THE SECOND HALF OF THE WORKWEEK AS WEAK HIGH
PRES MEANDERS OVER THE NW GULF. AN UPPER HIGH IN THE EPAC S OF
MEXICO IS TRANSPORTING UPPER MOISTURE INTO THE WRN GULF.

CARIBBEAN SEA...
WEAK PRES PATTERN IN THE WRN CARIB CONTINUES TO PRODUCE LIGHT NE
WINDS GENERALLY IN THE 5-15 KT RANGE. THE TRADES INCREASE TO
15-20 KT IN THE E CARIB AS RIDGING FROM THE AZORES HIGH HAS
TIGTHENED THE GRADIENT. SIMILAR CONDITIONS EXPECTED AT THE SFC
OVER THE NEXT COUPLE OF DAYS. IN THE UPPER LEVELS...A
TROUGH/RIDGE PATTERN REMAINS IN PLACE. STRONG SWLY UPPER FLOW
BETWEEN THESE FEATURES IS TRANSPORTING A SWATH OF DEBRIS MID TO
HIGH LEVEL CLOUDS AND EMBEDDED SHOWERS FROM CONVECTIVE BLOW-UPS
ALONG THE ITCZ...WHICH RUNS ACROSS PANAMA AND COLOMBIA...THROUGH
THE LEEWARD ISLANDS. DIFFLUENCE ALOFT/WEAK LOW LEVEL CONFLUENCE
IS HELPING TO SUPPORT THE SCATTERED TSTMS NOTED JUST S OF
HISPANIOLA.

WESTERN ATLANTIC...
THE LARGE LOW PRES SYSTEM CONTINUES TO BE THE HIGHLIGHT. THE
ASSOCIATED FRONTAL BOUNDARIES CONTINUE TO DISSIPATE...THOUGH
NUMEROUS TSTMS ARE NOTED NEAR THE OLD BOUNDARY N OF 27N BETWEEN
67W-73W. SIMILAR ACTIVITY IS OVER THE SE BAHAMAS/N OF HISPANIOLA
 FROM 20N-25N BETWEEN 68W-76W. THIS CONVECTION IS ALSO BEING
SUPPORTED BY DISTINCT UPPER DIFFLUENCE BETWEEN THE VERTICALLY
STACKED LOW OFF THE SOUTHEAST U.S. AND RIDGING EXTENDING N ALONG
61W.

CENTRAL AND EASTERN ATLANTIC...
A 1029 MB HIGH JUST W OF PORTUGAL IS IN CONTROL OF THE PATTERN
PROVIDING WIDESPREAD FAIR WEATHER AND MODERATE TRADES ACROSS
THIS PORTION OF THE ATLC. SAHARAN DUST APPEARS TO HAVE SPREAD TO
ABOUT 40W...ALTHOUGH THICKEST E OF 30W. THIS DUST IS ERODING THE
TYPICAL STRATOCUMULUS DECK ASSOCIATED WITH THE SUBTROPICAL
RIDGE. SCATTERED SHOWERS ARE POSSIBLE N OF 26N BETWEEN 40W-52W
ASSOCIATED WITH A PREFRONTAL TROUGH. AN UPPER LOW NEAR MADEIRA
ISLAND IS ONLY GENERATING SCATTERED PATCHES OF CIRRUS.

$$
WILLIS




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