[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181044
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN MAR 18 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0900 UTC.

...ITCZ...

ITCZ AXIS IS ALONG 7N12W 4N22W 6N30W 5N38W 1N50W. CONVECTION HAS
DECREASED CONSIDERABLY DURING THE PAST 24 HRS. SMALL AREA OF
SCATTERED MODERATE CONVECTION NOTED WITHIN 20 NM EITHER SIDE OF
A LINE FROM 3N21W TO 5N25W. OTHER MODERATE NEAR 3N14W AND 2N16W.

...DISCUSSION...

GULF OF MEXICO...
A WELL DEFINED UPPER LEVEL TROUGH HAS SHIFTED E OF THE AREA.
UPPER WINDS OVER THE GULF AREA ARE NWLY AT 40 TO 60 KT. MID
LEVEL HEIGHTS ARE RISING OVER THE NW PORTION AS RIDGING DEVELOPS
ALONG 100W. A 1024 MB POLAR HIGH LOCATED JUST S OF THE COAST OF
LOUISIANA IS MOVING SLOWLY NE. NLY WINDS TO 20 KT CONTINUE E OF
90W THIS MORNING WHILE N OF 25N W OF 90W WINDS HAVE SHIFTED TO
SE 10 TO 15 KT. S OF 25N W OF 90W WINDS ARE MOSTLY NE 10 TO 15
KT. LATEST WATER VAPOR IMAGERY SHOWS VERY DRY AIR IN THE  MID
AND UPPER LEVELS OVER THE SRN HALF OF THE GULF RESULTING IN
CLEAR SKIES. THE CENTER OF THE POLAR HIGH NE TO THE CAROLINA
COAST IN 24 HR. INCREASING E AND SE WINDS WILL DEVELOP OVER THE
GULF WITH AN INCREASE IN MOISTURE DURING THE NEXT 24 TO 36 HR.

CARIBBEAN...
A COLD FRONT EXTENDS FROM THE WINDWARD PASSAGE SW TO ERN
NICARAGUA. THE FRONT WILL CONTINUE TO MOVE E AND BECOME DIFFUSE.
WINDS OVER THE NW CARIBBEAN ARE NELY 15 TO 20 KT WITH SCATTERED
TO BROKEN CLOUDS AND ISOLATED SHOWERS. CONSIDERABLE CLOUDINESS
IS NOTED AHEAD OF THE FRONT WITH SCATTERED SHOWERS. EARLIER
CONVECTION OVER HAITI AND DOMINICAN REPUBLIC HAS DIMINISHED AND
MOVED NE OVER ATLC WATERS. ELY TRADES DOMINATE THE ERN CARIBBEAN
WITH SCATTERED CLOUDS AND ISOLATED WEAK SHOWERS. IN THE UPPER
ATMOSPHERE A BROAD ANTICYCLONE COVERS THE ERN HALF OF THE
CARIBBEAN WHILE OVER THE WRN HALF THE FLOW ALOFT IS MOSTLY SWLY.
HIGH LEVEL CLOUDINESS FROM EARLIER CONVECTION OVER COLOMBIA AND
WRN VENEZUELA WAS BEING ADVECTED N AND NE OVER THE ERN PORTION.

SW ATLANTIC...

STRONG UPPER TROUGH WITH AXIS ALONG 75W ROTATING RAPIDLY EWD.
BROAD SWATH OF VERY DRY UPPER LEVELS OVER CUBA AND THE BAHAMAS
SHIFTING NE BEHIND A JETSTREAM THAT CURVES CYCLONICALLY FROM ERN
CUBA TO 30N64W. QUIKSCAT SHOW JETSTREAM WINDS 70 TO 90 KT.
STRONG DIFFLUENT PATTERN ALOFT E OF TROUGH AXIS AIDING ISOLATED
CONVECTION E OF THE JET AXIS TO 60W N OF 22N. A COLD FRONT OVER
THE EXTREME SE BAHAMAS THIS MORNING CONTINUES E 15 KT.
MULTILAYERED CLOUDINESS 200 NM WIDE IS ASSOCIATED WITH THE FRONT
WITH EMBEDDED SHOWERS AND TSTMS. MOST OF THE ENERGY WITH THIS
FEATURE IS SHIFTING N OF 30N AHEAD OF THE FRONT AND MOST FRONTAL
CONVECTION HAS BEEN ON THE DECLINE THE PAST FEW HRS. OVER THE
ATLC S OF 20N W OF 40W LATEST SATELLITE PICTURES SHOW SCATTERED
TO BROKEN LOW AND MID CLOUDS MOVING W 20 KT WITH ISOLATED LIGHT
SHOWERS.

ERN ATLANTIC...

A CLOSED UPPER LOW THAT WAS JUST N OF THE CANARY ISLANDS HAS
FLATTENED OUT AND BECOME STATIONARY. SCATTERED CONVECTION NEAR
THE CENTER HAS DECREASED INDICATING THE SYSTEM HAS WEAKENED THE
PAST 24 HR. WATER VAPOR IMAGERY SHOWS A DRY SLOT ROTATING AROUND
THE SW SIDE OF THE ELONGATED LOW CENTER WITH A 40 KT JET
SEGMENT. WATER VAPOR IMAGERY ALSO SHOWS A NARROW BAND OF CIRRUS
ASSOCIATED WITH A JET STREAM ALONG 16N50W EWD OVER THE CAPE
VERDE ISLANDS. QUIKSCAT DATA SHOWS WIND VELOCITIES 60 TO 80 KT
WITH THIS JET. ON THE SURFACE STRONG HIGH PRESSURE CENTERED WELL
N OF THE REGION ALONG 30W EXTENDS S TO 10N E OF 50W. THE RIDGE
IS RESPONSIBLE FOR A MODERATE TO FRESH NE FLOW OF COOL AIR. THE
AIR PICKS UP MOISTURE FROM THE ATLC AND PRODUCES SCATTERED TO
BROKEN LOW AND MID CLOUDINESS THROUGHOUT THIS REGION.

$$
RRG






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