000
AXPZ20 KNHC 202201
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE AUG 20 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.
                                    
...SPECIAL FEATURES...

1007 MB LOW PRES IS EMBEDDED IN THE MONSOON TROUGH AND IS 
CENTERED NEAR 14N110W. SCATTERED MODERATE CONVECTION IS WITHIN 
120 NM IN THE W SEMICIRCLE OF THE LOW. THE MAJORITY OF THE MODEL 
GUIDANCE TAKES THE LOW IN A NORTHWARD MOTION DURING THE NEXT 24 
TO 48 HOURS. AT THE VERY LEAST...ASSOCIATED WINDS ARE FORECAST 
TO INCREASE TO 20 TO 25 KT WITH RESULTANT SEAS OF 8 TO 10 FT 
TONIGHT...GRADUALLY INCREASING TO 30 KT AND 12 FT THROUGH THU. 
THIS LOW HAS THE POTENTIAL TO BECOME A TROPICAL CYCLONE DURING 
THE NEXT 48 HOURS.

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

THE MONSOON TROUGH IS ALONG 08N78W TO 10N97W TO LOW PRES NEAR 
14N110W TO LOW PRES NEAR 17N123W TO 11N140W. NO ITCZ AXIS IS 
PRESENT. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS 
WITHIN 180 NM S OF THE MONSOON TROUGH BETWEEN 101W AND 106W... 
WITHIN 180 NM S OF THE MONSOON TROUGH BETWEEN 109W AND 121W... 
AND ALSO BETWEEN 123W AND 129W.

...DISCUSSION...

A LARGE AND BROAD UPPER LEVEL ANTICYCLONIC CIRCULATION IS OVER 
THE NW PORTION OF THE DISCUSSION WATERS CENTERED OVER 21N138W. 
VERY DRY AND STABLE AIR IS NOTED ACROSS THE MAJORITY OF THE 
WATERS N OF 12N W OF 125W. 

THIS DRY AIR CONTINUES EASTWARD ACROSS THE WATERS N OF 20N 
BETWEEN 120W AND 125W UNDER AN UPPER TROUGH WHICH EXTENDS FROM 
32N123W TO 22N124W TO 14N130W. THIS TROUGH IS CONTRIBUTING TO 
THE NORTHWARD ADVECTION OF CONVECTIVE DEBRIS FROM ALONG THE 
MONSOON TROUGH. 

THE UPPER TROUGH IS ALSO BRINGING STRONG SW SHEAR OVER THE 
WESTERN SURFACE LOW WHICH IS EMBEDDED IN THE MONSOON TROUGH NEAR 
17N123W. WINDS ON THE S SIDE OF THE LOW ARE FORECAST TO INCREASE 
TO 20 TO 25 KT WITH SEAS BUILDING TO 8 TO 10 FT BY WED 
AFTERNOON...HOLDING STEADY INTO THU.

1025 MB SURFACE HIGH PRES IS CENTERED NEAR 42N135W WITH A RIDGE 
AXIS EXTENDING SOUTHWARD THROUGH 33N140W THEN SE TO NEAR 
23N119W. A WEAK 1014 SURFACE LOW IS NEAR 32N125W. THIS LOW IS 
FORECAST TO MOVE NORTH AWAY FROM THE AREA THROUGH TONIGHT. A 
MAINLY LOOSE PRES GRADIENT EXTENDS ACROSS THE MAJORITY OF THE 
WATERS WITH LIGHT TO MODERATE WINDS AT THE SURFACE...EXCEPT FOR 
MODERATE TO FRESH SW FLOW S OF THE MONSOON TROUGH.
 
$$
LEWITSKY