000
AXPZ20 KNHC 312158
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI OCT 31 2008

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN
FROM THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 08N82W TO 06N100W TO 09N119W TO 
10N136W TO 09N140W. SCATTERED MODERATE CONVECTION CAN BE FOUND 
WITHIN 60 NM OF THE ITCZ AXIS FROM 111W TO 116W...WITHIN 90 NM 
OF THE AXIS FROM 91W TO 94W...AND WITHIN 210 NM S OF THE AXIS E 
OF 90W.

...DISCUSSION...

A CLOSED SURFACE CIRCULATION HAS DEVELOPED ALONG THE TROUGH 
ALONG 97W AND SCATTERED MODERATE CONVECTION CAN BE FOUND WITHIN 
180 NM W SEMICIRCLE OF THE LOW PRES CENTER NEAR 07N97W.  THIS 
SYSTEM WAS LIKELY SPURRED BY THE ATMOSPHERIC VORTICITY FROM THE 
LOW TO MID LEVEL JET THROUGH THE GULF OF PAPAGAYO AND IT NOW 
BEING ENHANCED BY ADDED VORTICITY SUPPLIED BY THE JET THROUGH 
THE GULF OF TEHUANTEPEC.  

THE STRONG PRESSURE GRADIENT THAT HAS BEEN PRESENT OVER CENTRAL 
AMERICA FOR SEVERAL DAYS IS FINALLY SHOWING SOME SIGNS OF 
RELAXATION...BUT WINDS IN THE GULF OF TEHAUNTEPEC ARE STILL 
EXPECTED TO REMAIN GALE FORCE FOR THE NEXT TWO DAYS.  SLACKENING 
WILL BE MORE EVIDENT TO THE SOUTH IN THE GULF OF PAPAGAYO WHERE 
WINDS AND SEAS MAY FALL BELOW 20 KT AND 8 FT RESPECTIVELY BY MON.

A BROAD MID TO UPPER LEVEL TROUGH HAS BEEN OVER THE N EASTERN 
PACIFIC FOR THE LAST SEVERAL DAYS BRINGING NW SWELL TO TO MUCH 
OF THE REGION W OF 120W.  A REINFORCING SHOT TO THIS BROAD 
TROUGH...IN THE FORM OF A COLD FRONT AT THE SURFACE...IS 
CURRENTLY APPROACHING NW WATERS AND WILL HELP TO CARRY THE BROAD 
TROUGH EASTWARD.  MEANWHILE...THE UPPER LEVEL ANTICYCLONE S OF 
THE BAJA PENINSULA NEAR 15N110W IS FORECAST TO PASS WESTWARD TO 
THE SOUTH OF THE TROUGH...LIMITING THE ENCROACHMENT OF THE 
TROUGH TO THE SOUTH.  EXPECT THE SURFACE COLD FRONT TO DISSIPATE 
SUN...BUT LEAVE ELEVATED SEAS OVER N WATERS.  THE EASTERN 
PROGRESS OF THE COLD FRONT OVER N WATERS WILL PUSH THE HIGH 
PRESSURE CURRENTLY CENTERED NEAR 27N119W EASTWARD AS 
WELL...INCREASING THE PRESSURE GRADIENT IN THE VICINITY OF THE 
BAJA AND THE GULF OF CALIFORNIA WHERE WINDS ARE EXPECTED TO BE 
IN THE 20 TO 25 KT RANGE OVER THE WEEKEND.

BROAD UPPER LEVEL DIFFLUENCE ON THE SOUTHWESTERN SIDE OF THE 
ANTICYCLONE S OF THE BAJA PENINSULA IS HELPING THE CAUSE FOR 
CONVECTION NEAR A SURFACE TROUGH ALONG 120W.  SCATTERED MODERATE 
CONVECTION CAN BE FOUND WITHIN 180 NM OF THE TROUGH AXIS FROM 
10N TO 15N.

$$
SCHAUER CLARK