000
AXPZ20 KNHC 211555
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED AUG 21 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 1205 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.
                                    
...SPECIAL FEATURES...

A SURFACE LOW PRES IS EMBEDDED ALONG THE MONSOON TROUGH AT 
15N110.5W AND IS DRIFTING NW WITH AN ESTIMATED SURFACE PRESSURE 
OF 1007 MB. CURRENTLY SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS DISORGANIZED OVER THE W SEMICIRCLE WITHIN 60 NM 
EITHER SIDE OF A LINE FROM 17.5N109W TO 14N113W. CURRENTLY THE 
DEBRIS MOISTURE ASSOCIATED WITH THE SURFACE LOW IS ADVECTED SW 
TO ALONG 05N BETWEEN 110-122W.

AN UPPER LEVEL ANTICYCLONE IS NOTED WELL TO THE N NEAR 22N115W 
WITH UPPER RIDGES EXTENDING SE TO 15N106W AND SW TO 16N126W. 
THERE IS SOME EVIDENCE OF AN UPPER ANTICYCLONE DEVELOPING ALONG 
THE  UPPER RIDGE NEAR 16N112W.

THESE ATMOSPHERIC...AS WELL AS OCEANOGRAPHIC...CONDITIONS FAVOR 
TROPICAL DEVELOPMENT WITH THE LOW MOVING NW TO NEAR 17N110.5W 
EARLY THU...NEAR 20N112W EARLY FRI...NEAR 23N115W EARLY SAT. AS 
THIS SURFACE LOW MOVES NW OVER THE NEXT FEW DAYS THE MONSOON 
TROUGH WILL ALSO EFFECTIVELY LIFT N WITH THE SOUTHERLY FLOW 
INCREASING TO 20-30 KT WITHIN 300-420 NM SE OF THE TROUGH AXIS. 
 
..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS W ALONG 10N FROM THE NW COAST OF 
COLOMBIA AT 76W ACROSS COSTA RICA TO OVER THE PACIFIC AT  
10N94W...THEN TURNS NW THROUGH THE EMBEDDED LOW PRES PREVIOUSLY 
DESCRIBED AT 15N110.5W...THEN CONTINUES W TO A SECOND...BUT ILL-
DEFINED...EMBEDDED SURFACE LOW PRES AT 16N122W...THEN TURNS SW 
TO BEYOND 10N140W. ISOLATED MODERATE AND STRONG CONVECTION IS 
NOTED S OF THE MONSOON TROUGH WITHIN 150 NM EITHER SIDE OF A 
LINE FROM 05N77W TO 09N86W...AND ALSO IN A CLUSTER WITHIN 45 NM 
OF 07N93W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS 
OBSERVED ALONG THE MONSOON TROUGH WITHIN 300 NM EITHER SIDE OF A 
LINE FROM 07N106W TO TO THE MEXICAN COAST AT 17N101W. SIMILAR 
CONVECTION IS NOTED WITHIN 60 NM EITHER SIDE OF OF LINES FROM 
11N115W TO 17N126W...AND FROM 11N129W TO 09N140W. 

THE ILL-DEFINED EMBEDDED SURFACE LOW AT 16N122W IS UNDER THE 
SHARP CREST OF AN UPPER RIDGE...WITH DRY UPPER AIR NOW 
ENTRAINING AROUND THE SOUTHERN PERIPHERY OF THE LOWER LEVEL 
CYCLONE...THUS THIS LOW HAS BEEN DROPPED FROM THE HIGH SEAS TEXT 
FORECAST AND IS FORECAST TO DISSIPATE WITHIN 24 HOUR ON THE 
SURFACE ANALYSIS.   

...DISCUSSION...

AN UPPER CYCLONE IS CENTERED N OF THE AREA AT 36N125W WITH AN 
UPPER TROUGH EXTENDING SW INTO THE DISCUSSION AREA FROM 32N121W 
TO 16N128W EFFECTIVELY SEPARATING THE UPPER FLOW ACROSS THE 
DISCUSSION AREA. A LARGE UPPER ANTICYCLONE IS AT 21N139W WITH 
ITS ENVELOPE OF ANTICYCLONIC FLOW DOMINATING THE UPPER LEVELS 
FROM 11-32N BETWEEN 130-150W. THESE TWO UPPER FEATURES COMBINE 
TO DRY OUT THE UPPER LEVELS W OF A LINE FROM SW CALIFORNIA TO 
14N128W. 

AN UPPER CYCLONE OVER THE NW CARIBBEAN HAS AN UPPER TROUGH 
EXTENDING SW ACROSS CENTRAL AMERICA AT 14N90W TO BASE OVER THE 
TROPICAL PACIFIC AT 01N98W. AN UPPER ANTICYCLONE IS OVER THE 
CARIBBEAN NEAR JAMAICA AND RIDGE SW TO A CREST AT 10N85W AND IS 
ENHANCING THE CONVECTION PREVIOUSLY DESCRIBED OVER THE PACIFIC S 
OF THE MONSOON TROUGH. MORE INTENSE CONVECTION IS ENHANCED OVER 
THE CARIBBEAN S OF 11N BETWEEN COLOMBIA AND COSTA RICA AND 
OVER/ALONG THE E COAST OF NICARAGUA.

$$
NELSON