[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 232357
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN SEP 23 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURE...
SUBTROPICAL STORM JERRY AT 23/2100 UTC IS CENTERED NEAR 36.8N
46.3W OR ABOUT 1060 NM W OF THE AZORES MOVING N AT 5 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB.  MAXIMUM
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT.  SEE LATEST
NHC FORECAST ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21
FOR MORE DETAILS.  THE SUBTROPICAL STORM IS A VERY BROAD CYCLONE
THAT MAY ACQUIRE TROPICAL CHARACTERISTICS WITHIN THE NEXT 12
HOURS.  ASSOCIATED CONVECTION IS ALSO BROAD AND NOT VERY WELL
ORGANIZED WITH IR IMAGERY SUGGESTING SCATTERED MODERATE WITHIN
240 NM SW AND 180 NM NE QUADRANTS.  A LARGER AREA OF CONVECTION
IS LOCATED TO THE SE OF THE SYSTEM IN AN UPPER DIFFLUENT ZONE.
THERE IS A NARROW WINDOW FOR JERRY TO TRANSITION TO A TROPICAL
STORM BEFORE BEING ABSORBED BY A LARGE EXTRATROPICAL LOW COMING
FROM THE CANADIAN MARITIMES.

A WELL DEFINED TROPICAL WAVE IS LOCATED ALONG 56W OR ABOUT 300
NM E OF THE WINDWARD ISLANDS.  THIS WAVE IS FAIRLY ACTIVE
GENERATING CLUSTERS OF WIDELY SCATTERED MODERATE CONVECTION IS
FROM 7N-14N BETWEEN 53W-58W.  THIS SYSTEM IS SHOWING SIGNS OF
ORGANIZING AND IT COULD DEVELOP INTO A TROPICAL DEPRESSION OVER
THE NEXT DAY OR SO AS IT APPROACHES THE WINDWARD ISLANDS.
REGARDLESS OF DEVELOPMENT...ASSOCIATED SHOWERS AND TSTMS WILL
BEGIN TO SPREAD ACROSS THOSE ISLANDS LATER TONIGHT AND TOMORROW.

A FAIRLY LARGE ACTIVE LOW PRESSURE SYSTEM IS LOCATED ABOUT 550
NM SW OF THE CAPE VERDE ISLANDS NEAR 7N29W.  ESTIMATED CENTRAL
PRESSURE IS 1007 MB.  THERE IS A FAIR AMOUNT OF CONVECTION NEAR
THE CENTER AND MORE TO THE N OF THE CENTER.  THE SYSTEM IS
GRADUALLY BECOMING BETTER ORGANIZED AND CONDITIONS ARE FAVORABLE
FOR IT TO BECOME A TROPICAL DEPRESSION DURING THE NEXT DAY OR
TWO.  WIDELY SCATTERED MODERATE CONVECTION IS FROM 4N-10N
BETWEEN 27W-33W.  SCATTERED MODERATE CONVECTION IS FROM 11N-14N
BETWEEN 27W-32W.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 36W S OF 18N MOVING W 10-15 KT. THIS WAVE
HAS MAINTAINED GOOD WWD CONTINUITY IN BOTH SATELLITE HOVMOLLER
DIAGRAMS AND THE MIMIC TPW ANIMATION SINCE EMERGING OFF THE
COAST OF AFRICA A FEW DAYS AGO.  HOWEVER...THE LARGE AND ACTIVE
LOW PRESSURE SYSTEM E OF THE WAVE...ERN MOST SPECIAL FEATURE
DISCUSSED ABOVE...IS BEGINNING TO OVERTAKE THIS WAVE AS
INDICATED BY A RECENT QSCAT PASS WHICH SHOWS IT EMBEDDED WITHIN
THE CIRCULATION OF THE LARGER LOW.

TROPICAL WAVE IS IN THE W CARIBBEAN ALONG 82W/83W S OF 19N
MOVING W 10-15 KT.  THE WAVE IS NOT EASILY SEEN IN ANY OF THE
AVAILABLE DATA...THEREFORE THE WAVE POSITION IS BASED ON FORWARD
EXTRAPOLATION.  THIS WEAK SYSTEM LIES UNDERNEATH AN UPPER
DIFFLUENT ZONE WHICH IS FUELING ISOLATED MODERATE CONVECTION IN
THE REGION BETWEEN 70W-80W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N15W 6N30W 6N40W 10N50W 11N60W.
BESIDES THE ACTIVITY ASSOCIATED WITH THE SPECIAL FEATURES...
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS INLAND OVER
W AFRICA FROM 6N-15N BETWEEN 9W-16W.

DISCUSSION...

GULF OF MEXICO...
A SURFACE TROUGH EXTENDS N FROM THE YUCATAN PENINSULA TO THE
CENTRAL GULF OF MEXICO ALONG 20N90W 27N92W.  E OF THE TROUGH
AXIS SURFACE WINDS ARE 10-20 KT FROM THE S.  A GOOD AMOUNT OF
TROPICAL MOISTURE IS ADVECTING N FROM THE NW CARIBBEAN TO THE E
GULF OF MEXICO AND FLORIDA.  ISOLATED MODERATE CONVECTION IS
FROM 20N-32N E OF 92W.  W OF THE TROUGH AXIS SURFACE WINDS ARE
5-10 KT FROM THE N WITH MOSTLY FAIR WEATHER.  THIS SURFACE
TROUGH HAS NOT BECOME ANY BETTER ORGANIZED THAN YESTERDAY...
HOWEVER IT MERITS WATCHING FOR FUTURE TROPICAL DEVELOPMENT.  IN
THE UPPER LEVELS...A LARGE UPPER LEVEL LOW IS CENTERED OVER S
TEXAS NEAR 26N97W.  STRONG SUBSIDENCE IS OVER THE W GULF AND
TEXAS W OF 92W.  AN UPPER LEVEL HIGH IS CENTERED N OF THE
YUCATAN CHANNEL NEAR 23N87W.  SIGNIFICANT UPPER LEVEL MOISTURE
IS E OF 92W.  EXPECT CONTINUED CONVECTION OVER THE GULF E OF 95W
DURING THE NEXT 24 HOURS.

CARIBBEAN SEA...
A TROPICAL WAVE IS ALONG 82W/83W.  SEE ABOVE.  SCATTERED
MODERATE TO ISOLATED STRONG CONVECTION IS INLAND OVER THE
YUCATAN PENINSULA FROM 18N-21N BETWEEN 87W-91W.  SCATTERED
MODERATE TO ISOLATED STRONG CONVECTION IS FURTHER E OVER CUBA
FROM 20N-22N BETWEEN 77W-84W.  SIMILAR CONVECTION IS INLAND OVER
HONDURAS FROM 12N-15N BETWEEN 86W-90W.  SURFACE TRADES ARE
RELATIVELY LIGHT OVER THE CARIBBEAN SEA.  IN THE UPPER LEVELS...
AN UPPER LEVEL LOW IS OVER THE W CARIBBEAN NEAR 13N75W.  UPPER
LEVEL RIDGING WITH SWLY FLOW IS OVER THE E CARIBBEAN E OF 70W.
EXPECT CONTINUED CONVECTION OVER THE W CARIBBEAN AND CENTRAL
AMERICA W OF 80W DURING THE NEXT 24 HOURS.

ATLANTIC OCEAN...
A 1019 MB HIGH IS NE OF BERMUDA NEAR 35N58W.  A LONG SURFACE
TROUGH IS OVER THE CENTRAL ATLANTIC THAT EXTENDS SW TO THE
LEEWARD ISLANDS ALONG 32N43W 27N50W 24N58W 16N62W.  WIDELY
SCATTERED MODERATE CONVECTION IS FROM 30N-33N BETWEEN
38W-43W...AND FROM 22N-25N BETWEEN 54W-60W.  A 1025 MB HIGH IS E
OF THE AZORES NEAR 38N21W.  A SURFACE RIDGE EXTENDS SW TO THE E
ATLANTIC NEAR 25N40W.  IN THE TROPICS...A 1011 MB LOW DEPICTED
AS A SMALL SWIRL OF LOW CLOUDS IS LOCATED BETWEEN TROPICAL WAVES
NEAR 14N46W.  THE LOW IS NEARLY STATIONARY WITH NO SIGNIFICANT
CONVECTION.  IN THE UPPER LEVELS... A RIDGE IS OVER THE W
ATLANTIC W OF 70W.  A TROUGH IS N OF 20N BETWEEN 50W-70W.  AN
UPPER LEVEL RIDGE IS N OF 20N BETWEEN 30W-50W.  AN UPPER LEVEL
TROUGH IS OVER THE E ATLANTIC AND W AFRICA N OF 15N BETWEEN
15W-30W.  AN EMBEDDED UPPER LEVEL LOW IS CENTERED NW OF THE
CANARY ISLANDS NEAR 32N20W.  IN THE TROPICS A LARGE UPPER LEVEL
HIGH IS CENTERED E OF THE WINDWARD ISLANDS NEAR 14N53W.
ANTICYCLONIC FLOW IS FROM EQ-20N BETWEEN 35W-70W.

$$
FORMOSA





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