000
AXPZ20 KNHC 272123
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI SEP 27 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

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

THE MONSOON TROUGH EXTENDS FROM 09N79W TO 10N90W TO 07N100W   
THEN RESUMES FROM LOW PRES NEAR 18N106W TO 10N126W TO 12N140W. 
NO ITCZ IS PRESENT E OF 140W. SCATTERED MODERATE AND ISOLATED 
STRONG CONVECTION IS N OF A LINE FROM 07N84W TO 03N78W. 
SCATTERED MODERATE CONVECTION IS WITHIN 150-210 NM SE OF THE 
MONSOON TROUGH BETWEEN 92W AND 99W...WITHIN 90 NM SE OF THE 
MONSOON TROUGH BETWEEN 114W AND 117W...AND ALSO FROM 10N TO 14N 
BETWEEN 121W AND 125W.

...DISCUSSION...     
                                    
WATER VAPOR SATELLITE IMAGERY INDICATES A MIDDLE TO UPPER LEVEL 
TROUGH PROGRESSING EASTWARD OVER THE WESTERN CONUS WITH A  
TROUGH AXIS EXTENDING FROM SOUTHERN CALIFORNIA NEAR 32N116W SW 
TO A BROAD BASE NEAR 29N124W. 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 AS A 
STATIONARY FRONT INTO FAR NW MEXICO FROM 32N108W TO 29N115W 
WHERE IT ENDS IN THE NORTHERN GULF OF CALIFORNIA. FRESH TO 
STRONG NORTHERLY WINDS ARE OCCURRING BEHIND THE FRONT IN THE 
GULF OF CALIFORNIA N OF 29.5N...AS CONFIRMED BY A RECENT ASCAT 
SCATTEROMETER PASS...WITH SEAS TO 8 FT ALSO POSSIBLE BEHIND THE 
FRONT. 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 12-14 SECONDS AND SEAS OF 8-11 FT ARE WITHIN AN AREA 
BOUNDED BY A LINE FROM 30N135W TO 20N139W TO 23N115W TO 30N117W. 
THESE SWELLS WILL SUBSIDE TO LESS THAN 8 FT BY EARLY SAT MORNING.

THE OTHER MAIN FEATURE NOTED ON WATER VAPOR IMAGERY IS A BROAD 
ANTICYCLONIC CIRCULATION CENTERED NEAR 18N112W. 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 112W AND 
128W. WEAK LOW PRES WAS AT THE SURFACE UNDERNEATH THIS 
ANTICYCLONE NEAR 13N115W...ALTHOUGH IT HAS BECOME ILL-DEFINED 
DURING THE PAST SEVERAL HOURS. REMNANT 8-9 FT SEAS COMBINED FROM 
EARLIER MODERATE TO FRESH WINDS NEAR THE LOW...ALONG WITH THE 
LONG PERIOD NW SWELL MENTIONED ABOVE...COVERS AN AREA BOUNDED BY 
A LINE FROM 10N124W TO 06N120W TO 09N111W TO 13N114W TO 10N124W. 
THESE SEAS ARE FORECAST TO SUBSIDE TO LESS THAN 8 FT BY SUN 
AFTERNOON. 

E OF 112W...NORTHEASTERLY FLOW ALOFT ORIGINATES OVER THE WESTERN 
CARIBBEAN SEA...TRAVERSING OVER CENTRAL AMERICA AND INTO THE 
EAST PACIFIC BECOMING DIFFLUENT W OF 90W. THE UPPER LEVEL 
DIFFLUENT PATTERN IS PROVIDING A FAVORABLE ENVIRONMENT FOR 
SCATTERED MODERATE CONVECTION IN THE VICINITY OF A BROAD 
MONSOONAL GYRE CENTERED NEAR 08N94W...AS IS DESCRIBED IN THE 
CONVECTION SECTION ABOVE.

$$
LEWITSKY