000
AXPZ20 KNHC 291537
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT OCT 29 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 AXIS IS ANALYZED FROM 09N85W TO 08N100W TO 
10N124W. THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ANALYZED 
FROM 10N124W TO 09N140W. SCATTERED MODERATE TO ISOLATED STRONG  
CONVECTION IS NOTED N OF 06N E OF 82W INCLUDING THE GULF OF 
PANAMA. SCATTERED MODERATE CONVECTION FROM 07N TO 09N BETWEEN 
82W AND 87W.

...DISCUSSION...

A WEAK MID TO UPPER LEVEL TROUGH OVER THE NW PORTION OF THE AREA 
IS WEAKENING AHEAD OF A STRONG CUT-OFF LOW LOCATED W OF AREA AND 
NE OF THE HAWAIIAN ISLANDS. UPPER DIVERGENCE AHEAD OF THE TROUGH 
IS SUPPORTING ISOLATED MODERATE CONVECTION FROM 12N TO 14N 
BETWEEN 120W AND 128W. AN ANTICYCLONIC CIRCULATION IS CENTERED 
NEAR 20N114W EXTENDING A RIDGE EWD OVER CENTRAL MEXICO. TO THE 
SE OF THIS ANTICYCLONE...THERE IS AN UPPER LEVEL LOW LOCATED 
NEAR 11N109W. MODERATE TO STRONG SUBSIDENCE AND IMPLIED DRY AIR 
MASS COVERS THE REMAINDER OF THE REGION PARTICULARLY S OF 06N 
BETWEEN 90W AND 110W. 

SURFACE RIDGING EXTENDS FROM 1025 MB HIGH PRES N OF THE AREA 
NEAR 35N132W TO 18N113W. A TIGHT PRES GRADIENT BETWEEN THE RIDGE 
AND LOWER PRES ASSOCIATED WITH THE ITCZ CONTINUES TO PRODUCE 
FRESH TRADES FROM 12N TO 20N W OF 125W AS INDICATED BY THE MOST 
RECENT SCATTEROMETER PASSES. THESE WINDS WILL PERSIST OVER 
ROUGHLY THE SAME AREA THROUGH 48 HOURS.

FRESH NW TO N WINDS ARE STILL BLOWING ACROSS THE GULF OF 
CALIFORNIA THIS MORNING BUT ARE FORECAST TO DIMINISH BELOW 20 KT 
LATER TODAY AS PRES GRADIENT RELAXES OVER THE REGION.

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 
AS THE LOW PRES OVER THE SW CARIBBEAN DEVELOPS. EXPECT ALSO 
BUILDING SEAS OF AROUND 9 FT. A WEAK 1011 MB LOW PRES IS 
EMBEDDED IN THE MONSOON TROUGH NEAR 10N117W. AN EARLIER ASCAT 
PASS SHOWED VERY WELL THE CYCLONIC CIRCULATION WITH WINDS BELOW 
20 KT. FIRST-LIGHT VISIBLE IMAGERY REVEALS A SWIRL OF LOW CLOUDS 
IN ASSOCIATION WITH THIS LOW WHICH IS FORECAST TO MOVE WWD WITH 
LITTLE CHANGE DURING THE NEXT 24 HOUR.  

GULF OF TEHUANTEPEC...AN EARLIER HIGH RESOLUTION ASCAT PASS 
SHOWED 25 TO 30 KT WINDS ENTERING THE GULF OF TEHUANTEPEC IN 
ASSOCIATION WITH A SURGE OF COOL AIR OVER THE SW PORTION OF THE 
GULF OF MEXICO. THE DRAINAGE FLOW WILL ALLOW WINDS TO INCREASE 
TO GALE FORCE THROUGH TONIGHT...WITH WINDS IN EXCESS OF 20 KT 
EXTENDING AS FAR AS 360 NM SW OF THE GULF. SEAS WILL BUILD TO AS 
HIGH AS 14 FT BY LATE TONIGHT. WINDS WINDS DIMINISH BELOW GALE 
FORCE THROUGH SUN AS THE AIRMASS OVER THE SW GULF MODIFIES. 8 TO 
10 FT NE SWELL ASSOCIATED WITH THE GAP WIND EVENT WILL EXTEND AS 
FAR AS 500 NM S TO SW OF THE TEHUANTEPEC AREA BY LATE SUN. 
ACCORDING TO THE GFS AND NAM COMPUTER MODELS...GAP WINDS MAY 
INCREASE AGAIN TO GALE FORCE LATE MON AS LOW PRES DEVELOPS OVER 
THE SW CARIBBEAN AND HIGH PRES BUILDS OVER THE NE GULF OF MEXICO.

$$
GR