000
AXPZ20 KNHC 290912
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI JUL 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0730 UTC.

...ITCZ/MONSOON TROUGH...
MONSOON TROUGH AXIS EXTENDS FROM 09N84W TO 1009 MB LOW PRES NEAR 
09N94W TO 1009 MB LOW PRES NEAR 12N115W TO 11N120W. ITCZ AXIS 
EXTENDS FROM TO 11N120W TO 09N140W. SCATTERED MODERATE 
CONVECTION LIES WITHIN 60 NM N AND 180 NM S OF THE MONSOON 
TROUGH E OF 88W. SCATTERED MODERATE CONVECTION LIES WITHIN 150 
NM N SEMICIRCLE OF THE LOW NEAR 12N115W.

...DISCUSSION...
A CUT OFF LOW ALOFT IS NEAR 25N132W. THE LOW WILL BE PICKED UP 
BY AN AMPLIFYING NORTHERN STREAM TROUGH LATER TODAY...SHIFTING 
THE MEAN TROUGH SLIGHTLY WESTWARD. AN ANTICYCLONE LIES TO THE NW 
OF THE LOW NEAR 30N145W. THIS ANTICYCLONE WILL MOVE LITTLE AND 
WILL WEAKEN AS THE NORTHERN STREAM TROUGH APPROACHES. THE 
SUBTROPICAL HIGH AT THE SURFACE ASSOCIATED WITH THIS ANTICYCLONE 
IS DISPLACED WELL TO THE N NEAR 42N147W. THE SUBTROPICAL SURFACE 
RIDGE HAS BEEN COMPROMISED BY THE DEEP LAYER TROUGHING OVER THE 
N CENTRAL PORTION OF THE FORECAST AREA. THE NE TRADE WINDS HAVE 
BEEN REDUCED TO A GENTLE TO MODERATE BREEZE OVER NW WATERS AS A 
RESULT. NE SWELL FROM A GALE AREA OFF THE U.S. PACIFIC NW COAST 
ASSOCIATED WITH THE DEEP LAYER TROUGHING WILL MOVE INTO NW 
WATERS AND RAISE SIGNIFICANT WAVE HEIGHTS TO 9 FT LATER TODAY. 

A SECOND ANTICYCLONE ALOFT IS NEAR 16N120W. A RIDGE AXIS EXTENDS 
E FROM THE ANTICYCLONE TO 18N108W. A WEAK LOW ALOFT NEAR 21N111W 
ACTS TO SEVER THE RIDGE THAT RESUMES NEAR 17N104W AND EXTENDS TO 
AN ANTICYCLONE OVER THE LOWER MISSISSIPPI RIVER VALLEY NEAR 
31N92W. CURRENTLY...SCATTERED MODERATE CONVECTION IS WITHIN 120 
NM OF THE MEXICAN COAST BETWEEN 94W AND 103W. THIS CONVECTION IS 
BEING ENHANCED BY THE DIFFLUENCE ALOFT ASSOCIATED WITH THE RIDGE 
AXIS. AS THE DEEP LAYER TROUGH TO THE NW SHIFTS WESTWARD...THE 
LOW AND ANTICYCLONE ALOFT OFF BAJA CALIFORNIA WILL SHIFT NW AND 
THE RIDGE WILL STRENGTHEN S OF THIS WEAKENING UPPER LOW. THE 
SURFACE RIDGE WILL BUILD OFF THE COAST OF BAJA CALIFORNIA IN 
TURN. THIS WILL ALLOW FOR FRESH NW WINDS OFF THE CENTRAL BAJA 
CALIFORNIA COAST LATER TODAY THAT WILL SHIFT TO THE NORTHERN 
COAST BY EARLY SUN.

THE 0448 UTC ASCAT PASS SHOWED THE LARGEST AREA OF FRESH WINDS 
LIES S OF 06N BETWEEN 96W AND 112W. THIS FRESH SW MONSOON FLOW 
IS EXPECTED TO SHIFT SLIGHTLY NORTHEASTWARD TODAY AS A NEW 
BATCH OF SW SWELL MAKES ITS WAY THROUGH SOUTHEASTERN WATERS. 
THIS SWELL WILL DAMPEN TO LESS THAN 8 FT WELL BEFORE IT REACHES 
THE CENTRAL AMERICAN AND MEXICAN COAST LATE SAT. THE FORECAST 
GUIDANCE CONTINUES TO SHOW A GREAT DEAL OF UNCERTAINTY IN THE 
EXTENT OF FRESH WINDS S OF THE MONSOON TROUGH...WITH SOME OF THE 
MODELS TRYING TO DEVELOP DISTINCT AREAS OF LOW PRES ALONG THE 
MONSOON TROUGH. THE LATEST HIGH SEAS FORECAST WAS BASED ON A 
BLENDED SOLUTION THAT DOES NOT LATCH ONTO A LOW PRES SYSTEM. 
CONFIDENCE IS SOMEWHAT LOW IN THE FORECAST BECAUSE OF THE LACK 
OF AGREEMENT IN THE GUIDANCE.
  
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SCHAUER