000
AXPZ20 KNHC 010922
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT DEC 01 2012

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

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

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

MONSOON TROUGH EXTENDS FROM 07N78W TO 08N94W TO 07N110W WHERE IT 
TRANSITIONS TO THE ITCZ TO 07N123W TO 07N140W. SCATTERED 
MODERATE CONVECTION IS NOTED WITHIN 60 NM N OF THE TROUGH 
BETWEEN 91W AND 98W...AND BETWEEN 108W AND 11OW. NO SIGNIFICANT 
CONVECTION ELSEWHERE.

...DISCUSSION...

ALOFT...MOSTLY ZONAL FLOW DOMINATES THE FORECAST AREA N OF 21N.  
A SHORTWAVE TROUGH EXTENDS FROM 21N121W TO 10N132W TO NEAR 
03N140W. BROKEN HIGH CLOUDS STREAMING NE TOWARDS SRN BAJA 
CALIFORNIA ARE OBSERVED AHEAD OF THIS TROUGH. BROAD MID/UPPER 
RIDGING PERSISTS ACROSS THE E WATERS WITH A MEAN RIDGE AXIS 
STRETCHING FROM NORTHERN SOUTH AMERICA TO NEAR 14N110W. UPPER 
DIFFLUENCE ASSOCIATED WITH THIS RIDGE IS HELPING TO INDUCE 
SCATTERED MODERATE CONVECTION ALONG THE MONSOON TROUGH. A SECOND 
SHORT-WAVE TROUGH WILL DEVELOP ACROSS THE NW WATERS LATER TODAY. 

AT THE SURFACE...A LARGE EXTRATROPICAL CYCLONE IN THE GULF OF 
ALASKA CONTINUES TO GENERATE LARGE NW SWELLS INTO THE DISCUSSION 
AREA THAT RESULTING IN 14-16 FT SEAS IN THE NW CORNER OF THE 
FORECAST REGION. AN ALTIMETER PASS CORROBORATED THE PRESENCE OF 
THESE SEA HEIGHTS. THIS SWELL EVENT IS NOW PROPAGATING E AND SE 
ACROSS THE REGIONAL WATERS AND COVERS THE AREA N OF 20N W OF 
112W AND S OF 20N W OF A LINE FROM 20N112W TO 10N122W TO 
00N134W. THESE SWELLS WILL SLOWLY SUBSIDE OVER THE NEXT 48 HRS. 
BY SUNDAY NIGHT...SWELL FROM THIS EVENT OF AT LEAST 8 FT 
SIGNIFICANT WAVE HEIGHT WILL COVER MOST OF THE REGION WEST OF 
110W. SW TO W WINDS ASSOCIATED WITH THE LARGE CIRCULATION OF 
THIS EXTRATROPICAL CYCLONE CONTINUE TO AFFECT THE FAR THE NW 
WATERS BUT HAVE DIMINISHED TO 15-20 KT. 

A 1021 MB HIGH PRES IS CENTERED NEAR 26N124W WITH A RIDGE 
EXTENDING MAINLY WWD TO 24N146W. PRES GRADIENT BETWEEN THIS A 
HIGH AND A TROUGH LOCATED ACROSS WESTERN MEXICO SUPPORTS NW 
WINDS IN THE 20 TO 25 KT RANGE N OF 24N E OF 118W. FIVE SHIP 
OBSERVATIONS CONFIRMED THE PRESENCE OF THESE WIND SPEEDS. A WEAK 
TROUGH IS ALONG 24N132W 18N137W WITH ONLY POSSIBLE ISOLATED 
SHOWERS ASSOCIATED WITH IT. THE HIGH PRES WILL DRIFT WWD OVER 
THE NEXT COUPLE OF DAYS.

GAP WINDS...
N TO NE WINDS OF 20 TO 30 KT WILL CONTINUE TO FUNNEL THROUGH THE 
CHIVELA PASS INTO THE GULF OF TEHUANTEPEC WITH SEAS OF 8-9 FT. 
WINDS ARE GREATEST DURING THE OVERNIGHT AND EARLY MORNING HOURS 
WITH THE AID OF THE NOCTURNAL DRAINAGE FLOW. THESE WINDS WILL 
SLOWLY DIMINISH TO 20 TO 25 KT IN 48 HRS. LOOKING AHEAD...MARINE 
GUIDANCE SUGGESTS THE POSSIBILITY OF A NEW GULF OF TEHUANTEPEC 
GAP WIND EVENT OCCURRING WED AND THU...BUT LIKELY REMAINING 
BELOW GALE FORCE.

THE OTHER GAP WIND AREAS OF THE GULF OF PAPAGAYO AND THE GULF OF 
CALIFORNIA SHOULD REMAIN WITH WINDS OF 20 KT OR LESS AND SEAS 
LESS THAN 8 FT THROUGH TUESDAY. 

$$
GR