000
AXPZ20 KNHC 261541
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 
1530 UTC.

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

MONSOON TROUGH EXTENDS FROM 11N86W TO LOW PRES NEAR 10N95W 1007 
MB TO 12N105W TO 10N110W TO 11N120W. THE ITCZ EXTENDS FROM 
10N110W TO 08N140W. SCATTERED MODERATE CONVECTION WITHIN 60 NM 
EITHER SIDE OF MONSOON TROUGH AXIS BETWEEN 86W AND 92W. 
SCATTERED MODERATE WITHIN 90 NM N OF AXIS BETWEEN 115W AND 122W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 75 NM 
EITHER SIDE OF ITCZ AXIS BETWEEN 125W AND 135W...AND WITHIN 90 
NM S OF ITCZ AXIS W OF 135W.

...DISCUSSION...
A DEEP LAYER RIDGE N OF 20N ALONG 140W IS SHIFTING EAST AHEAD OF 
A VIGOROUS SHORT WAVE TROUGH N OF HAWAII NEAR 35N155W PIVOTING 
EASTWARD AT THE BASE OF CLOSED UPPER LOW NEAR 44N163W. A 1028 MB 
SURFACE HIGH ASSOCIATED WITH THE UPPER RIDGE IS CENTERED NEAR 
33N135W. SCATTEROMETER DATA INDICATE A BROAD SWATH OF 20 TO 25 
KT TRADE WINDS AROUND THE PERIPHERY OF THE HIGH PRES MAINLY N OF 
10N W OF 115W TO INCLUDE OFF THE NORTHERN BAJA COAST. THE 
CONVERGENCE OF THE FRESH TO STRONG TRADES IS DRIVING CONVECTIVE 
GROWTH NEAR THE ITCZ W OF 125W...ALSO ASSISTED IN PART BY 
DIVERGENCE ALOFT ON THE SE SIDE OF AN UPPER TROUGH EXTENDING 
FROM 27N130W TO 15N140W.

FURTHER EAST ALONG...A TRIO OF WEAK CIRCULATIONS APPEAR ALONG 
THE MONSOON TROUGH AXIS...A WEAK FORMATION NEAR 
11N120W...ANOTHER WEAK CIRCULATION NEAR 11N107W...AND A BETTER 
FORMED LOW PRES NEAR 10N95W WITH AN ESTIMATED SLP OF 1007 MB. 
THE SURFACE LOW FORMED AT THE BASE OF A SHARP UPPER TROUGH 
EXTENDING FROM THE NW CARIBBEAN ACROSS GUATEMALA AND EL SALVADOR 
TO 10N95W WHERE IT INTERACTED WITH MODERATE SW FLOW. PULSES OF 
NORTHERLY FLOW ORIGINATING FROM THE GULF OF TEHUANTEPEC TO THE 
NORTH HAVE BEEN PROVIDING ADDED VORTICITY BUT ALSO INJECT 
SOMEWHAT DRIER AIR...AND LIMITING CONVECTION NEAR THE LOW. 
OPERATIONAL AND ENSEMBLE MODELS ARE IN GOOD AGREEMENT SHOWING 
THE EASTERNMOST LOW PRES AREA WEAKENING SLIGHTLY AS IT DRIFTS 
W...BUT DEEPEN THE OTHER TWO SYSTEMS A BIT THROUGH 48 HOURS.

A COLD FRONT WILL MOVE THROUGH THE GULF OF MEXICO THROUGH 
SAT...ACCOMPANIED BY A COOLER AND DRIER AIRMASS TAKING OVER THE 
WESTERN GULF. THIS DENSER AIR WILL SPILL THROUGH THE TEHUANTEPEC 
GAP STARTING TONIGHT...REACHING NEAR GALE FORCE BY EARLY SAT. 
THIS EVENT MAY PERSIST THROUGH EARLY NEXT WEEK GIVEN THE 
CHARACTER OF THE HIGH PRES BUILDING OVER THE GULF OF MEXICO. 
STRONGEST GAP WINDS WILL LIKELY BE IN THE EARLY MORNING WHEN 
DIURNAL EFFECTS ARE AT A MAXIMUM.

1033 MB SURFACE HIGH PRES OVER THE GREAT BASIN IN CONJUNCTION 
WITH TROUGHING OVER NW MEXICO WILL ALLOW STRONG NW WINDS ACROSS 
THE GULF OF CALIFORNIA TODAY THROUGH MUCH OF SAT...DIMINISHING 
INTO SUN AS THE HIGH PRES SHIFTS E.

$$
CHRISTENSEN