[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 262354
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE SEP 26 2006

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...SPECIAL FEATURE...
A 1011 MB SURFACE LOW PRESSURE CENTER IS NEAR 23N50W...OR ABOUT
740 NM EAST-NORTHEAST OF THE NORTHERN LEEWARD ISLANDS. THE
CLOUDINESS AND SHOWERS ASSOCIATED WITH THIS LOW HAVE CHANGED
LITTLE IN ORGANIZATION THIS AFTERNOON. THIS SYSTEM STILL HAS
SOME POTENTIAL FOR TROPICAL CYCLONE FORMATION DURING THE NEXT
DAY OR TWO AS IT MOVES NORTHWESTWARD. NUMEROUS MODERATE/ISOLATED
STRONG CONVECTION REMAINS MOSTLY E AND NE OF THE CENTER FROM
23N-26N BETWEEN 46W-50W.

...TROPICAL WAVES...
A NEW TROPICAL WAVE HAS EMERGED OFF THE COAST OF AFRICA ALONG
18W S OF 15N MOVING W NEAR 10 KT. THIS WAVE IS ACCOMPANIED BY A
1011MB SURFACE LOW NEAR 11N...AS VERIFIED BY THE AVAILABLE
SURFACE/SHIP OBSERVATIONS NEARBY AND LOW CLOUD MOTIONS.
CONVECTION ASSOCIATED WITH THE WAVE HAS BEEN ON THE DECREASE
OVER THE LAST FEW HOURS...WITH SCATTERED SHOWERS/TSTMS NOW NOTED
WITHIN 100NM OF THE WAVE AXIS.

TROPICAL WAVE IS ALONG 36W SOUTH OF 16N MOVING WEST NEAR 15 KT.
THIS POSITION IS BASED ON CONTINUITY AND HOVMOLLER DIAGRAMS AS
CYCLONIC TURNING IS VAGUE...WITH AN ELONGATED E/W TROUGH AROUND
10N ASSOCIATED WITH THE ITCZ IN THE VICINITY. THE MOST
SIGNIFICANT CONVECTION REMAINS W OF THE WAVE POSITION FROM
10N-13N BETWEEN 30W-36W...BUT AGAIN THIS MAY BE MORE ASSOCIATED
WITH THE ITCZ. THE 26/2000 UTC QUIKSCAT PASS DOES SHOW SOME
SUBTLE CYCLONIC TURNING NEAR THE WAVE AXIS BUT SUGGESTS A VERY
LOW AMPLITUDE FEATURE.

TROPICAL WAVE IS ALONG 52W/53W SOUTH OF 16N DRIFTING WEST. THIS
WAVE HAS BEEN MOVING IN TANDEM WITH THE SURFACE LOW MENTIONED IN
THE SPECIAL FEATURE SECTION. ISOLATED SHOWERS ARE RELATED TO THE
WAVE. THERE IS A CLUSTER OF MODERATE CONVECTION NW OF THE WAVE
FROM 16N-19N BETWEEN 53W-56W...IN A REGION OF LOW LEVEL
CONFLUENCE.

A TROPICAL WAVE EXTENDS FROM THE SE BAHAMAS ACROSS WRN HAITI TO
NRN COLOMBIA...ALONG 73W/74W MOVING W 10 TO 15 KT. THE NORTHERN
PORTION OF THE WAVE MAY BE ENHANCING THE SCATTERED SHOWERS OVER
THE SOUTHERN BAHAMAS...HISPANIOLA...CUBA AND THE ADJACENT WATERS
AS IT INTERACTS WITH AN UPPER TROUGH OVER THIS AREA.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N20W 10N32W 8N39W 9N50W 10N55W
9N61W. OUTSIDE FROM THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVES...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
BEGINNING TO EMERGE OFF THE COAST OF SIERRA LEONE FROM 6N-11N
EAST OF 14W. SCATTERED MODERATE CONVECTION IS FROM 8N-12N
BETWEEN 23W-27W...FROM 10N-13N BETWEEN 30W-36W...AND FROM 7N-11N
BETWEEN 40W-49W.

...DISCUSSION...
THE GULF OF MEXICO...
A COLD FRONT CONTINUES TO EXTEND FROM CENTRAL FLORIDA TO THE
CENTRAL GULF NEAR 25N90W...AND THEN BECOMES STATIONARY FROM THIS
POINT THROUGH THE BAY OF CAMPECHE. SHOWER AND TSTM ACTIVITY
ASSOCIATED WITH THIS FRONT ARE OVERALL MINIMAL/ISOLATED AT BEST
OVER THE GULF THIS EVENING. A MID TO UPPER LEVEL HIGH IS JUST S
OF MAZATLAN MEXICO THIS EVENING THAT HAS RIDGING AFFECTING MUCH
OF THE GULF WITH THE AXIS ALONG 25N/26N. DEEP LAYER CYCLONIC
FLOW SEEN IN THE FAR NE GULF AROUND THE TROUGHING AFFECTING THE
ERN UNITED STATES. AFTERNOON CONVECTION OVER THE YUCATAN
PENINSULA AND WRN CUBA IS STREAMING TO THE WEST INTO THE
ADJACENT GULF WATERS AROUND THE UPPER HIGH AFFECTING THE AREA.
ELSEWHERE AT THE SURFACE BESIDES THE FRONT...A 1021MB HIGH IS
BUILDING OVER THE NW GULF FROM NW LOUISIANA. LOOK FOR THE FRONT
AND HIGH FROM TX/LA TO CONTINUE MOVING SLOWLY SE OVER THE NEXT
24 HRS.

THE CARIBBEAN SEA...
THE MOST ACTIVE WEATHER IN THE CARIBBEAN THIS EVENING IS IN THE
WRN PORTION AROUND 80W. NUMEROUS MODERATE/ISOLATED STRONG
CONVECTION IS FROM 11N-19N BETWEEN 78W-83W...WITH THE STRONGEST
CONVECTION GENERALLY BETWEEN NICARAGUA AND JAMAICA. THIS SEEMS
MOSTLY ASSOCIATED WITH UPPER DIFFLUENCE BETWEEN A WELL DEFINED
UPPER HIGH OVER THE CENTRAL CARIBBEAN NEAR 14N74W AND UPPER
TROUGHING OVER THE FAR NW CARIBBEAN. THESE SHOWERS AND
THUNDERSTORMS ARE DISORGANIZED...AND SURFACE PRESSURES IN THE
REGION NOT FALLING. FURTHER DEVELOPMENT IS NOT EXPECTED. TRADES
CONTINUE IN THE 15 TO 20 KT RANGE ON THE SW PORTION OF THE ATLC
HIGH AND ITS INTERACTION WITH LOWER PRESSURE NEAR COLOMBIA.
SIMILAR TRADES EXPECTED THE NEXT COUPLE OF DAYS.

THE ATLANTIC OCEAN...
A COLD FRONT EXTENDS NE FROM CENTRAL FLORIDA INTO THE ATLANTIC
WITH ISOLATED SHOWERS/TSTMS WITHIN 150NM OF THE FRONT. THE MOST
SIGNIFICANT AREA OF SHOWERS WITH EMBEDDED TSTMS IS MOVING OFF
CENTRAL FLORIDA FROM 27N-29N BETWEEN 78W-81W. AN UPPER RIDGE
COVERS THE SW NORTH ATLC OUT TO 70W FROM ITS ORIGIN S OF
MAZATLAN MEXICO. AN UPPER LOW IS NEAR 27N67W THAT HAS TROUGHING
EXTENDING THROUGH THE SE BAHAMAS. UPPER DIFFLUENCE BETWEEN THIS
FEATURES AND THE LARGE SCALE TROUGHING OVER ERN UNITED STATES IS
HELPING TO SUPPORT THE CLUSTER OF SCATTERED MODERATE CONVECTION
FROM 27N-32N BETWEEN 69W-73W. LOW CLOUD MOTIONS ALSO REVEALED
THERE IS A 1019MB SURFACE HIGH IN THIS REGION NEAR 26N69W. THE
FLOW AROUND THIS IS COLLIDING WITH THE FLOW AROUND A CENTRAL
ATLC 1023MB HIGH NEAR 31N44W TO PRODUCE A SURFACE TROUGH ALONG
25N63W 33N63W. ISOLATED SHOWERS/TSTMS ARE SEEN WITHIN 40NM OF
THIS TROUGH THAT IS A LEFTOVER PIECE OF AN OLD FRONTAL BOUNDARY.
ANOTHER UPPER LOW IS NEAR 25N57W THAT IS PRODUCING SWLY SHEAR
OVER THE SPECIAL FEATURE AS IT INTERACTS WITH BROAD UPPER
RIDGING EXTENDING W FROM AFRICA TO NEAR 50W. THERE ARE A FEW
EMBEDDED UPPER HIGH CENTERS IN THIS REGION SEEN ON WV IMAGERY.
N OF THIS REGION IN THE ERN ATLC LIES THE TAIL END OF A SURFACE
COLD FRONT ALONG 32N22W 27N28W. MID TO UPPER CYCLONIC FLOW IS
DOMINATING THE ERN ATLC FROM 20N TO 32N BETWEEN THE COAST OF
AFRICA AND 35W ASSOCIATED WITH A WELL DEFINED UPPER LOW NEAR
31N23W.

$$
WILLIS




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