000
AXPZ20 KNHC 281543
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI OCT 28 2011

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 
1415 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH IS FROM 08N84W TO 08N100W TO 12N120W. THE 
INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 12N120W TO 
13N130W TO 10N140W. SCATTERED MODERATE TO ISOLATED STRONG FROM 
10N TO 16N BETWEEN 120W AND 125W...AND FROM 15N TO 17N BETWEEN 
129W AND 132W.

...DISCUSSION...

A CUT-OFF LOW IS OVER THE NW PORTION OF THE AREA NEAR 28N135W. 
AN UPPER LEVEL TROUGH EXTENDS FROM THIS LOW TO A BASE OVER THE 
DEEP TROPICAL PACIFIC AT 10N130W. AN UPPER LEVEL ANTICYCLONE IS 
OVER THE E PACIFIC NEAR 19N117W WITH AN UPPER RIDGE EXTENDING NW 
TO BEYOND 32N123W AND ANOTHER RIDGE EXTENDING NE FROM THE 
ANTICYCLONE TO OVER SOUTHERN BAJA CALIFORNIA. UPPER LEVEL 
DIFFLUENCE E OF THE UPPER TROUGH AXIS IS ENHANCING CONVECTION 
BETWEEN 120W AND 125W AS DESCRIBED ABOVE. MODERATE TO STRONG 
SUBSIDENCE IS EVIDENT ON WATER VAPOR SATELLITE IMAGERY N OF 15N 
E OF 113W. AN UPPER LEVEL CYCLONE IS SPINNING NEAR 11N107W WITH 
VERY DRY AIR TO THE SE OF THIS FEATURE COVERING THE REMAINDER OF 
THE AREA PARTICULARLY S OF 06N BETWEEN 85W AND 110W.

SURFACE RIDGING EXTENDS FROM 1022 MB HIGH PRES N OF THE AREA 
NEAR 35N132W TO 18N113W. FRESH NW TO N WINDS ARE BLOWING ACROSS 
THE GULF OF CALIFORNIA. THE EXPERIMENTAL 1416 UTC ASCAT 25 KM 
COASTAL WINDS PROVIDED OBSERVATIONS OF THESE WINDS...WHICH ARE 
FORECAST TO DIMINISH BELOW 20 KT IN ABOUT 24 HOURS AS HIGH PRES 
OVER THE GREAT BASIN WEAKENS AND THE PRES GRADIENT RELAXES OVER 
THE REGION.

A TIGHT PRES GRADIENT BETWEEN THE RIDGE AND LOWER PRES 
ASSOCIATED WITH THE ITCZ CONTINUES TO PRODUCE FRESH TRADES FROM 
15N TO 21N W OF 130W...AND FROM 13N TO 17N BETWEEN 125W AND 130W 
NE TO E WINDS 20 KT AS INDICATED BY THE MOST RECENT 
SCATTEROMETER PASSES. THESE WINDS WILL PERSIST OVER ROUGHLY THE 
SAME AREA THROUGH 48 HOURS. MEANWHILE FRESH SW FLOW S OF THE 
MONSOON TROUGH WILL CONTINUE OVER THE FAR SE PORTION OF THE AREA 
S OF PANAMA THROUGH 48 HOURS WITH SEAS BUILDING TO 9 FT.

GAP WINDS...A STRONG COLD FRONT WILL MOVE THROUGH THE SW GULF OF 
MEXICO LATER TODAY RESULTING IN A SURGE OF STRONG NORTHERLY 
WINDS WHICH WILL FUNNEL THROUGH THE CHIVELA PASS INTO THE GULF 
OF TEHUANTEPEC COMMENCING THIS EVENING. THESE WINDS WILL RAPIDLY 
INCREASE TO GALE FORCE TONIGHT CONTINUING THROUGH SUN MORNING. 
EXPECT THE STRONGEST WINDS...IN THE 30 TO 40 KT RANGE...SAT 
AFTERNOON AND EVENING WITH BUILDING SEAS TO AROUND 14 FT. 
LOOKING AHEAD...GALE CONDITIONS ARE EXPECTED TO DIMINISH BRIEFLY 
LATE SUN...WITH A RECURRENCE MON AS A TIGHT PRES GRADIENT 
DEVELOPS OVER THE AREA BETWEEN STRENGTHENING HIGH PRES OVER 
INTERIOR MEXICO AND LOWER PRES ASSOCIATED WITH THE MONSOON 
TROUGH.

$$
GR