000
AXPZ20 KNHC 280242
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT SEP 28 2013

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0230 UTC.

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

THE MONSOON TROUGH FROM 08N78W TO 10N90W TO 07N99W...THEN 
RESUMES FROM LOW PRES NEAR 18N106.5W TO 09N130W. THE ITCZ 
EXTENDS FROM 09N130W TO 11N140W. SCATTERED MODERATE CONVECTION 
IS N OF A LINE FROM 04N78W TO 07N79W TO 05N84W....FROM 05N TO 
07N BETWEEN 95W AND 100W...AND ALSO FROM 10N TO 13N BETWEEN 115W 
AND 119W.

...DISCUSSION...     
                                    
WATER VAPOR SATELLITE IMAGERY INDICATES A MIDDLE TO UPPER LEVEL 
TROUGH PROGRESSING EASTWARD OVER THE WESTERN CONUS WITH A  
TROUGH AXIS EXTENDING FROM THE CALIFORNIA/ARIZONA BORDERN NEAR 
32N114W TO A BROAD BASE NEAR 28N125W. THIS IS PROVIDING THE 
DISCUSSION AREA N OF 20N WITH PRIMARILY WEST-SOUTHWESTERLY   
FLOW ALOFT IN A FAIRLY DRY AND STABLE AIRMASS. THE TROUGH IS 
SUPPORTING A SURFACE COLD FRONT SLICING THROUGH NEW 
MEXICO...CONTINUING SW THROUGH FAR NW MEXICO TO ACROSS THE 
NORTHERN GULF OF CALIFORNIA WATERS NEAR 28.5N114W. FRESH TO 
STRONG NORTHERLY WINDS ARE OCCURRING BEHIND THE FRONT IN THE 
GULF OF CALIFORNIA N OF 29.5N...AS CONFIRMED BY AN AFTERNOON 
ASCAT SCATTEROMETER PASS. THESE CONDITIONS ARE FORECAST TO 
REMAIN THROUGH THE OVERNIGHT HOURS...THEN WILL DIMINISH/SUBSIDE 
BY EARLY SAT MORNING AS THE REMNANTS OF THE SOUTHERN PORTION OF 
THE FRONT WASH OUT.

ELSEWHERE ACROSS THE WATERS N OF 20N...NW SWELL WITH WAVE 
PERIODS OF 11-14 SECONDS AND SEAS OF 8-10 FT ARE N OF 21N 
BETWEEN 117W AND 132W...AND 5-7 FT ACROSS THE REMAINDER OF THE 
WATERS N OF 20N. THESE SWELLS WILL SUBSIDE TO LESS THAN 8 FT BY 
EARLY SAT AFTERNOON.

THE OTHER MAIN FEATURE NOTED ON WATER VAPOR IMAGERY IS A BROAD 
ANTICYCLONIC CIRCULATION CENTERED NEAR 19N112W. W OF 112W...A 
DIFFLUENT MIDDLE TO UPPER LEVEL ENVIRONMENT WITHIN THE 
SOUTHWESTERN QUADRANT OF THE UPPER LEVEL ANTICYCLONE IS 
SUSTAINING CONVECTION ALONG THE MONSOON TROUGH BETWEEN 113W   
AND 130W. AN AREA OF REMNANT 8-9 FT SEAS COMBINED FROM EARLIER 
MODERATE TO FRESH WINDS NEAR A SINCE DISSIPATED AREA OF  LOW 
PRES NEAR 13N115W...ALONG WITH THE LONG PERIOD NW SWELL 
MENTIONED ABOVE...COVERS THE WATERS FROM 07N TO 12N BETWEEN 110W 
AND 120W. THESE SEAS ARE FORECAST TO SUBSIDE TO LESS THAN 8 FT 
BY SUN AFTERNOON. 

E OF 112W...PRIMARILY NORTHEAST-EAST FLOW DOMINATES THE WATERS 
ALOFT...ORIGINATING OVER CENTRAL AMERICA AND BECOMING DIFFLUENT 
W OF 90W. THE UPPER LEVEL DIFFLUENT PATTERN IS PROVIDING A 
FAVORABLE ENVIRONMENT FOR CONVECTION ALONG THE MONSOON TROUGH AS 
IS DESCRIBED IN THE SECTION ABOVE.

$$
LEWITSKY