000
AXPZ20 KNHC 101548
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE SEP 10 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...TROPICAL WAVES... 

A TROPICAL WAVE IS ANALYZED N OF 11N ALONG 95W. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION IS OBSERVED FROM 09-14N 
BETWEEN 90-98W. EXPECT THAT THIS TROPICAL WAVE WILL BE 
DIFFICULT TO LOCATE IN ABOUT 24 HOURS AS IT CONTINUES W INTO AN 
AREA OF INCREASING SOUTHWESTERLY MONSOONAL FLOW. 

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

THE MONSOON TROUGH AXIS EXTENDS W ALONG 11N ACROSS THE SW 
CARIBBEAN FROM THE NW COAST OF COLOMBIA TO ACROSS SOUTHERN 
NICARAGUA TO THE PACIFIC COAST NEAR 12N87W...THEN TURNS NW TO A 
TROPICAL WAVE AT 12N95W WHERE IT LOSES IDENTITY. SCATTEROMETER 
DATA INDICATES THE MONSOON TROUGH THEN RESUMES AT 13N105W AND 
WIGGLES WSW TO BEYOND 10N140W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION IS OBSERVED S OF THE MONSOON TROUGH AXIS FROM 
02-08N BETWEEN 78-83W AND WITHIN 90 NM OF 12.5N88W. ISOLATED 
MODERATE TO STRONG CONVECTION IS NOTED WITHIN 90 NM EITHER SIDE 
OF A LINE FROM 08N83W TO 06N90W...WITHIN 150 NM OF 08N102W...AND 
WITHIN 90 NM EITHER SIDE OF A LINE FROM 11N116W TO 13N125W TO 
11N130W.

...DISCUSSION...

AN UPPER TROUGH HAS MOVED OVER THE FAR NW PORTION FROM 32N137W
TO 28N142W INTO ANOTHER UPPER CYCLONE AT 26N144W. AN ASSOCIATED 
WEAK COLD FRONT WILL DIP INTO THE NW CORNER ON THU...AND 
PROGRESS SE ON FRI STALLING FROM 32N133W TO 27N140W ON SAT. 
EXPECTING ONLY A 10 KT WIND SHIFT ALONG THE FRONTAL BOUNDARY.

A SECOND UPPER CYCLONE IS OVER THE BORDER OF CALIFORNIA AND 
ARIZONA AT 34N114.5W...TRAILING AN UPPER TROUGH S ACROSS THE 
BAJA CALIFORNIA PENINSULA TO 27N115W...THEN TURNING SW THROUGH 
24N120W TO 21N130W...AND INTO AN UPPER CYCLONE AT 19N132W...WITH 
THE TROUGH CONTINUING S TO BASE AT 14N131W. AN UPPER ANTICYCLONE 
IS NOTED AT 26N136W WITH A RIDGE EXTENDING N TO A SHARP CREST AT 
32N131W. A SECOND UPPER ANTICYCLONE AT 16N140W WITH ITS ENVELOPE 
OF ANTICYCLONIC FLOW ONLY WITHIN 180 NM OF ITS CENTER. AN UPPER 
ANTICYCLONE IS OBSERVED OVER CENTRAL OLD MEXICO AT 22N102W WITH 
AN UPPER RIDGE EXTENDING W TO A SHARP CREST AT 21N129W. A RIDGE 
ALSO EXTENDS ESE FROM THIS ANTICYCLONE ACROSS CENTRAL AMERICA TO 
A GENTLE CREST OVER THE SW CARIBBEAN AT 12N79W. 

UPPER MOISTURE IS ROTATING CYCLONICALLY AROUND THE SOUTHERN 
SEMICIRCLE OF THE CALIFORNIA CYCLONE...BUT ONLY WITHIN 60 NM OF 
ITS CENTER. OTHERWISE THESE UPPER FEATURES COMBINE TO DRY OUT 
THE UPPER LEVELS W OF A LINE FROM 32N110W TO 18N111W TO 10N140W. 
WEAK UPPER DIFFLUENCE S OF THE CENTRAL AMERICAN RIDGE IS 
SUPPORTING THE CONVECTION PREVIOUSLY DESCRIBED...WITH THE DENSE 
DEBRIS MOISTURE ADVECTED NEARLY DUE W ACROSS THE TROPICS TO THE N 
OF A LINE FROM 01N80W TO 10N110W.  
 
ELSEWHERE AT THE LOW LEVELS A SURFACE RIDGE EXTENDS FROM 30N140W 
TO 17N125W. A BROAD TROUGH EXTENDS FROM THE GULF OF CALIFORNIA 
SE TO NEAR 15N100W. ISOLATED MODERATE TO STRONG CONVECTION IS 
OBSERVED N OF 17N BETWEEN 101-108W. THERE IS A CONSENSUS IN THE 
GUIDANCE FOR A SURFACE LOW TO DEVELOP ALONG THE SOUTHERN EXTENT 
OF THIS TROUGH...NEAR 17N105W...AND MEANDER FOR SEVERAL DAYS. 
SOUTHWESTERLY MONSOONAL FLOW AT 15-20 KT IS OBSERVED MOSTLY BY 
SCATTEROMETER DATA ACROSS THE TROPICS SE OF A LINE FROM 17N100W 
TO 12N130W WITH SEAS 5-8 FT PRIMARILY DUE TO S TO SW CROSS 
EQUATORIAL SWELL. THE SW FLOW IS EXPECTED TO INCREASE TO 20-25 
KT WITHIN 150 NM SE OF LINE FROM 13N96W TO 12N110W LATE WED 
NIGHT WITH COMBINED SEAS INCREASING TO 9-11 FT. 

$$
NELSON