000
AXPZ20 KNHC 271532
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI OCT 26 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1445 UTC.

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

MONSOON TROUGH EXTENDS FROM 09N84W TO 12N92W TO LOW PRES NEAR 
09N97W 1007 MB TO LOW PRES NEAR 11N108W 1007 MB TO LOW PRES NEAR 
11N122W 1007 MB TO 07N140W. SCATTERED MODERATE TO ISOLATED 
STRONG CONVECTION WITHIN 60 NM EITHER SIDE OF AXIS BETWEEN 105W 
AND 110W. SCATTERED MODERATE CONVECTION WITHIN 90 NM N OF AXIS 
BETWEEN 120W AND 125W.

...DISCUSSION...

AN UPPER TROUGH EXTENDS FROM SOUTHERN CALIFORNIA TO 20N135W TO 
12N140W...REINFORCED IN PART BY A SHORT WAVE TROUGH DIGGING SE 
ALONG THE CALIFORNIA COAST TOWARD NORTHERN BAJA. THE TROUGH 
AMPLIFIES N OF 20N AS AN MID TO UPPER RIDGE WITH AN AXIS FROM 
THE WA/OR COAST TO ROUGHLY 25N140W SHIFTS E...AHEAD OF A DEEP 
LAYER TROUGH N OF 25N MOVING E THROUGH 145W. A 1025 MB SURFACE 
HIGH PRES CENTERED NEAR 35N135W ASSOCIATED WITH THE UPPER RIDGE 
WILL FLATTEN AND SHIFT SE TO 30N130W SUN AHEAD OF THE ADVANCING 
DEEP LAYER TROUGH. AN ASCAT PASS FROM 06 UTC SHOWED A PERSISTENT 
AREA OF 20 TO 25 KT N WINDS BETWEEN THE SURFACE HIGH PRES AND 
THE BAJA COAST. THESE WINDS WILL DIMINISH AS THE HIGH PRES 
SHIFTS SE. 

AN AREA OF FRESH TO STRONG TRADES S OF THE HIGH PRES 
HAS DIMINISHED OVER THE PAST 12 HOURS...LEAVING SEAS TO 8 FT IN 
NE SWELL. A ROUND OF NW SWELL WILL PUSH INTO THE AREA N OF 10N W 
OF 135W THROUGH 48 HOURS AND MIX WITH THE DECAYING NE SWELL. 

SCATTERED MODERATE CONVECTION ALONG THE MONSOON TROUGH W OF 130W 
HAS LARGELY DIMINISHED AS THE TRADE WIND FLOW SUBSIDED...BUT 
CONTINUES TO FLARE FARTHER EAST ASSOCIATED WITH A 1007 MB LOW 
PRES NEAR 11N122W...AND NEAR ANOTHER 1007 MB LOW PRES AREA ALONG 
THE MONSOON TROUGH NEAR 11N108W. OPERATIONAL AND GLOBAL MODELS 
SHOW MODEST DEVELOPMENT OF BOTH LOW PRES AREAS AS THEY DRIFT TO 
THE W...ALTHOUGH WINDS IN EXCESS OF 20 KT IS NOT ANTICIPATED 
THROUGH 48 HOURS. SEAS TO 8 FT CAN BE EXPECTED NEAR EACH LOW 
PRES AREA.

A TIGHT PRES GRADIENT TO THE SOUTH OF A HIGH PRES SYSTEM OVER 
THE GREAT BASIN OF UNITED STATES CONTINUES TO BRING FRESH TO 
STRONG NW WINDS ACROSS THE NORTHERN AND CENTRAL SECTIONS OF THE 
GULF OF CALIFORNIA THROUGH THIS AFTERNOON BEFORE DIMINISHING TO 
20 KT OR LESS THIS EVENING. THE 0420 UTC ASCAT PASS PROVIDED 
OBSERVATIONS OF 20-25 KT NW WINDS ACROSS THE GULF OF CALIFORNIA 
N OF 26N. 

CLIMATOLOGICALLY OCTOBER MARKS THE BEGINNING OF THE TEHUANTEPEC 
WIND EVENTS. PRESENTLY...A COLD FRONT IS MOVING THROUGH THE GULF 
OF MEXICO ACCOMPANIED BY A COOLER AND DRIER AIRMASS. THIS DENSER 
AIR HAS ALREADY SPILLED THROUGH THE CHIVELA PASS INTO THE GULF 
OF TEHUANTEPEC AND IS FORECAST TO REACH 25-30 KT BY EARLY THIS 
MORNING. THIS EVENT IS EXPECTED TO PERSIST THROUGH THE WEEKEND 
WITH WINDS DIMINISHING TO 20-25 KT SUN NIGHT. WAVEWATCH GUIDANCE 
BUILDS SEAS 8-11 FT IN THE GULF.

$$
CHRISTENSEN