[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202337
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT OCT 20 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.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 50W/51W S OF 18N MOVING W 10-15 KT. THIS
WAVE CONTINUES TO SHOW UP WELL IN SATELLITE IMAGERY WITH CLEAR
LOW TO MID LEVEL CYCLONIC TURNING AROUND THE AXIS. MOST OF THE
ASSOCIATED...DISORGANIZED CONVECTION IS DISPLACED TO THE E OF
THE AXIS DUE TO STRONG UPPER LEVEL SW WINDS OVER THE AREA.
SCATTERED MODERATE CONVECTION IS WITHIN 180 NM E OF THE AXIS
MAINLY FROM 7N-13N.

WEAK TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 78W S OF
15N MOVING W 10-15 KT. THERE ARE SCATTERED TSTMS OVER THE SW
CARIBBEAN OFFSHORE PANAMA...S OF 14N BETWEEN 76W-82W.
HOWEVER...IT IS UNCLEAR IF THIS ACTIVITY IS ACTUALLY FROM THE
WAVE OR FROM DIVERGENCE ALOFT NEAR THE BASE OF AN UPPER TROUGH.
A 48 HOUR LOOP OF THE UW-CIMSS TPW PRODUCT SHOWS THAT THE
HIGHEST AREA OF MOISTURE CONTENT IN THE VICINITY IS ACTUALLY NOW
IN THE NW CARIBBEAN...WHICH WAS BETWEEN HISPANIOLA AND VENEZUELA
A COUPLE DAYS AGO. THE FEATURE NOW IN THE NW CARIBBEAN IS BEING
ANALYZED AS A TROUGH JUST E OF THE YUCATAN PENINSULA. GIVEN THAT
THE FLOW AROUND THE TROUGH IS DOMINATING THE AREA...THE WEAK
WAVE AT 78W MAY BE DROPPED FROM THE NEXT MAP.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N12W 6N30W 10N48W 11N61W.
BESIDES FOR THE ACTIVITY ASSOCIATED WITH THE TROPICAL SCATTERED
ISOLATED TSTMS ARE WITHIN 90 NM EITHER SIDE OF AXIS BETWEEN
22W-35W. THE ITCZ MAY ALSO BE ENHANCING THE SCATTERED
MODERATE/ISOLATED STRONG CONVECTION OVER THE TROPICAL ATLANTIC
TO THE COAST OF SOUTH AMERICA...FROM 7N-12N BETWEEN 55W-62W.

DISCUSSION...

GULF OF MEXICO...
AS OF 20/2100 UTC...A STATIONARY FRONT EXTENDS FROM SW FLORIDA
NEAR 26N82W WSW THROUGH THE MIDDLE AND WESTERN GULF ALONG 24N88W
25N87W. AN UPPER HIGH IS NEAR THE ERN BAY OF CAMPECHE WHILE A
SHORTWAVE UPPER TROUGH IS OVER THE ERN GULF GENERALLY ALONG 87W.
THE COMBINATION OF THE SFC FRONT AND THE UPPER TROUGH IS
SUPPORTING SCATTERED SHOWERS AND TSTMS AROUND THE FLORIDA KEYS
AND JUST OFFSHORE SW FLORIDA...OVER THE SE GULF WATERS S OF 27N
E OF 87W. A SECONDARY WEAK SFC TROUGH IS OVER THE BAY OF
CAMPECHE ALONG 23N97W 19N92W. THIS ALONG WITH THE UPPER HIGH ARE
SUPPORTING SCATTERED SHOWERS/ISOLATED TSTMS OFF THE COAST OF
MEXICO S OF 23N W OF 93W. VERY DRY AIR AND MOSTLY CLEAR SKIES
ARE OVER THE NRN GULF AND GULF COAST STATES...GENERALLY N OF 25N
EXCEPT N OF 27N OVER THE ERN GULF. A WEAK SFC HIGH OVER ALABAMA
IS ALSO SUPPORTING THE NICE WEATHER OVER THE NRN GULF. THIS HIGH
IS EXPECTED TO MOVE E FAIRLY QUICKLY OVER THE NEXT COUPLE OF
DAYS IN ADVANCE OF THE NEXT STRONGER COLD FRONT EXPECTED TO MOVE
OFF THE TEXAS COAST DURING MONDAY. MODEL GUIDANCE SUGGESTS THE
STATIONARY FRONT AND ASSOCIATED MOISTURE/SHOWERS CURRENTLY JUST
OFF SW FLORIDA WILL SLIDE NW/N AS A WARM FRONT THROUGH EARLY
WEEK...REACHING THE CENTRAL GULF COAST BY TOMORROW EVENING.

CARIBBEAN SEA...
SCATTERED SHOWERS AND ISOLATED TSTMS ARE OVER MUCH OF THE NW
CARIBBEAN BETWEEN HONDURAS AND WRN CUBA...ASSOCIATED WITH A SFC
TROUGH ANALYZED ALONG 23N84W 16N87W. UPPER DIFFLUENCE IS ALSO
SUPPORTING THIS ACTIVITY...AROUND THE SW PERIPHERY OF AN UPPER
HIGH NE OF THE BAHAMAS. THE SHOWER ACTIVITY OVER THE NW
CARIBBEAN IS EXPECTED TO MOVE NW INTO THE GULF DURING SUNDAY. AN
UPPER LOW IS JUST SW OF PUERTO RICO...THAT HAS TROUGHING
EXTENDING SW TOWARDS PANAMA. LIFT AHEAD OF THIS FEATURE IS
SUPPORTING DISORGANIZED SHOWERS AND TSTMS OVER THE FAR ERN
CARIBBEAN...LESSER ANTILLES...AND TROPICAL NORTH ATLANTIC S OF
18N BETWEEN 56W-64W. MODEL GUIDANCE SUGGESTS THE UPPER TROUGHING
WILL SLIDE WWD OVER THE NEXT COUPLE OF DAYS...AND THUS THE
SHOWER ACTIVITY EXPECTED TO MOVE SLOWLY W THROUGH MON AFFECTING
THE ERN CARIBBEAN. TRADES ARE MODERATE OVER THE CENTRAL AND ERN
CARIBBEAN...AND BEND MORE SE IN THE WRN PORTION AHEAD OF THE
TROUGH NEAR THE GULF OF HONDURAS.

ATLANTIC OCEAN...
A COLD FRONT IS OVER THE WRN ATLC...ENTERING THE AREA NEAR
32N76W AND CONTINUING SW TO NEAR PALM BEACH. SCATTERED SHOWERS
AND TSTMS ARE ALONG AND WITHIN 120 NM OF THE FRONT. THE FRONT IS
EXPECTED TO MOVE E AND WEAKEN TO A POSITION BETWEEN NEAR BERMUDA
AND THE NW BAHAMAS THROUGH SUN EVENING...AS HIGH PRES BUILDS
INTO THE WRN ATLC BEHIND THE FRONT. THE UPPER PATTERN OVER THE
WRN ATLC IS DOMINATED BY A LARGE ANTICYCLONE CENTERED NEAR
27N75W.

AN ELONGATED UPPER TROUGH EXTENDS SW ACROSS MUCH OF THE CENTRAL
ATLC ALONG 32N45W 23N60W TO NEAR NE PUERTO RICO. THIS IS
SUPPORTING A SFC TROUGH ALONG 32N34W 26N42W 25N55W...WHICH
EXTENDS SW FROM A 1015 MB LOW NEAR 34N34W. SCATTERED SHOWERS ARE
GENERALLY WITHIN 120 NM EITHER SIDE OF THE SFC TROUGH...WITH
LIGHTNING DATA ALSO DEPICTING A FEW TSTMS NEAR THE WRN PORTION
OF THE TROUGH AXIS FROM 24N-27N BETWEEN 50W-55W. LOW LEVEL
CONFLUENCE IS ALSO SUPPORTING THE SFC TROUGH...BETWEEN RIDGING
AROUND A 1028 MB HIGH N OF THE AREA NEAR 39N48W AND ANOTHER WEAK
1018 MB HIGH NEAR 26N31W. NWP GUIDANCE SUGGESTS WEAK TROUGHING
AND SCATTERED SHOWER ACTIVITY WILL PERSIST OVER THIS PORTION OF
THE ATLC THROUGH SUN.

THE REMAINDER OF THE E ATLC JUST OFF THE AFRICAN COAST REMAINS
TRANQUIL...UNDER THE INFLUENCE OF WEAK SFC RIDGING AND STABLE
AIR. THIS IS EXPECTED TO PERSIST OVER THE NEXT COUPLE OF DAYS.

$$
WILLIS




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