000
AXPZ20 KNHC 300921
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT OCT 30 2010

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 0900 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE WAS ANALYZED FROM 08N82W TO 
10N104W TO 08N116W TO 12N124W THEN RESUMES NEAR 12N129W TO 
10N140W. SCATTERED MODERATE CONVECTION WAS NOTED WITHIN 120 NM N 
OF THE AXIS BETWEEN 93W AND 96W AND ALSO WITHIN 60 NM OF THE 
AXIS BETWEEN 105W AND 108W. SIMILAR CONVECTION WAS NOTED WITHIN 
270 NM N OF THE AXIS BETWEEN 110W AND 115W.

...DISCUSSION...

A HIGHLY AMPLIFIED UPPER LEVEL TROUGH EXTENDS FROM A CYCLONE 
CENTERED NEAR THE MOUTH OF SAN FRANCISCO BAY N OF THE DISCUSSION 
AREA TO 32N124W TO 24N130W TO 18N136W THEN FLATTENS AS IT 
REACHES TO NEAR 16N140W. THIS TROUGH IS SUPPORTING A COLD FRONT 
AT THE SURFACE WHICH EXTENDS FROM 32N120W TO 26N125W TO 23N136W. 
PLENTIFUL TROPICAL MOISTURE IS BEING ADVECTED OUT AHEAD OF THE 
UPPER TROUGH WITH SCATTERED SHOWERS OCCURRING WITHIN 90 NM OUT 
AHEAD OF THE COLD FRONT. THE FRONT WILL DISSIPATE DURING THE 
NEXT 24 HOURS AS IT SHIFTS E TO SE. LONG PERIOD NW SWELLS UP TO 
15 FT ARE OCCURRING NW OF THE FRONT AND THIS SWELL WILL 
PROPAGATE S TO 10N DURING THE NEXT 24 TO 48 HOURS WHILE DECAYING 
TO 8 TO 10 FT. A SHIP WITH CALL SIGN ZCDA9 POSITIONED NEAR 
27N136W RECENTLY REPORTED 13 FT SEAS.

A BROAD UPPER LEVEL ANTICYCLONE IS CENTERED OVER THE NW GULF OF 
MEXICO WITH UPPER RIDGING IN PLACE S OF THE ANTICYCLONE OVER THE 
E PORTION OF THE DISCUSSION AREA. CONVECTIVE ACTIVITY IS BEING 
ENHANCED ALONG THE ITCZ E OF 118W WHILE VERY DRY AIR IS 
PREVALENT UNDER THE ANTICYCLONES INFLUENCE N OF 18N AND E OF THE
BAJA CALIFORNIA PENINSULA.

ELSEWHERE AT THE SURFACE...A WEAK SURFACE TROUGH IS EMBEDDED IN 
THE ITCZ FROM 11N126W TO 19N123W WITH 20 KT WINDS OCCURRING 
WITHIN 120 NM OF THE TROUGH AXIS N OF 14N AS CAPTURED BY A 0520 
UTC ASCAT PASS. THIS TROUGH IS EXPECTED TO DISSIPATE WITHIN THE
NEXT 12 HOURS.

EXPECT A BRIEF EPISODE OF S TO SW 20 KT WINDS IN THE FAR 
NORTHERN GULF OF CALIFORNIA THIS MORNING WITH WINDS DIMINISHING 
BY AFTERNOON. A TIGHT PRES GRADIENT WILL BECOME ESTABLISHED OVER 
THE REGION BETWEEN A BUILDING RIDGE OF HIGH PRES W OF THE BAJA 
CALIFORNIA PENINSULA AND A STRENGTHENING THERMAL TROUGH OVER NW 
MEXICO AND SOUTHERN U.S. CALIFORNIA. AS A RESULT NW WINDS OF 20 
KT WILL OCCUR IN THE GULF OF CALIFORNIA FROM 36 TO 48 HOURS AND 
LIKELY BEYOND. NW TO N WINDS WILL ALSO BE FUNNELED N OF 25N 
WITHIN 120 NM W OF THE BAJA CALIFORNIA PENINSULA BY 42 TO 48 
HOURS.

GAP WINDS...
GALE FORCE NORTHERLY WINDS CONTINUE TO SURGE FROM THE GULF OF 
MEXICO THROUGH THE CHIVELAS PASS AND INTO AND DOWNWIND OF THE 
GULF OF TEHUANTEPEC. AN EARLIER LAND BASED OBSERVATION FROM 
SALINA CRUZ MEXICO REPORTED 40 KT SUSTAINED WINDS. GIVEN THE 
FETCH OF THESE WINDS EXPECT RESULTANT SEAS OF 10 TO 15 FT. WINDS 
WILL DIMINISH TO LESS THAN GALE FORCE BY 24 HOURS AS THE PRES 
GRADIENT WEAKENS SIGNIFICANTLY.

MODEL GUIDANCE IS IN GOOD AGREEMENT REGARDING INCREASING 
EASTERLY DRAINAGE WINDS IN THE GULF OF PAPAGAYO TO 20 KT 
COMMENCING IN THE NEXT FEW HOURS WITH ANOTHER SURGE EXPECTED IN 
24 HOURS WITH WINDS DIMINISHING BY 36 HOURS.

$$
LEWITSKY