000
AXPZ20 KNHC 092117
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL 
2205 UTC FRI AUG 09 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...   

A LOW PRESSURE CENTER 1009 MB AT 11N116W MOVING W AT 12 KT 
APPROACHES REGION OF MODERATE EASTERLY VERTICAL SHEAR WHILE 
CONTINUING OVER WARM SEA SURFACE TEMPERATURE AND INTO A MOIST 
ATMOSPHERE.  ENVIRONMENT IS MODERATELY CONDUCIVE FOR 
DEVELOPMENT.  NHC HAS GIVEN IT A MEDIUM CHANCE TO DEVELOP INTO 
TROPICAL CYCLONE OVER THE NEXT 48 HOURS AND A HIGH CHANCE WITHIN 
THE NEXT FIVE DAYS. 
                       
TROPICAL STORM HENRIETTE HAS MOVED W OF THE FORECAST AREA AND 
CONTINUES TO WEAKEN.  SEAS OVER FORECAST AREA EXPECTED TO 
DIMINISH AND FALL BELOW THRESHOLD CRITERIA WITHIN THE NEXT 06 
HOURS. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...        
MONSOON TROUGH EXTENDS FROM 09N84W TO 14N107W TO 1009 MB LOW 
PRES AT 11N116W TO 12N125W TO LOW PRES 1009 MB AT 10N132W.  
SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 180 NM OF 
AXIS W OF 114W.  SCATTERED MODERATE FROM 08N TO 13N BETWEEN 100W 
TO 110W.  

...DISCUSSION... 
ANOTHER WEAK LOW PRESSURE CENTER IS AT 10N132W 
AND REMAINS UNDER MODERATE NORTHEASTERLY SHEAR BUT OVER STILL 
WARM SEA SURFACE TEMPERATURES AND ABUNDANT TROPICAL MOISTURE.  
SOUTHEAST OF THE LOW...THERE HAS BEEN AN ONGOING LOW-LEVEL SW 
SURGE INTO THE MONSOON TROUGH.  THIS HAS ENHANCED THE DEEP 
CONVECTION AS MENTIONED ABOVE...BUT HAS NOT YET INDUCED 
CYCLOGENESIS.  NHC HAS GIVEN IT A LOW CHANCE TO DEVELOP INTO A 
TROPICAL CYCLONE DURING THE NEXT 48 HOURS AND A MEDIUM CHANCE 
DURING THE NEXT FIVE DAYS. IT WILL LIKELY CROSS W OF 140W IN 
ABOUT 48 HOURS. 

...ELSEWHERE AT THE LOWER LEVELS... 
A RELATIVELY WEAK STATIONARY 
HIGH PRESSURE OF 1022 MB W OF AREA IS LOCATED NEAR 30N149W WITH 
A RIDGE EXTENDING SE TO 20N108W.  AS THE PRESSURE GRADIENT 
BETWEEN THE HIGH AND THE MONSOON TROUGH IS WEAK...THE TRADEWINDS 
ARE BELOW OUR 25 KT THRESHOLD FOR THE HIGH SEAS.

...UPPER LEVELS... 
SUBTROPICAL RIDGING DOMINATES THE BASIN ALONG 
19N140W TO 26N110W WITH E TO NE FLOW PREVAILING ON THE 
EQUATORWARD SIDE.  A LARGE UPPER LOW NEAR 10N104W IS 
RETROGRADING WESTWARD SOUTH OF THE SUBTROPICAL RIDGE.  A WEAK 
MID-LATITUDE TROUGH EXTENDS FROM 28N122W NORTH-NORTHWESTWARD TO 
A CLOSED LOW OVER N CALIFORNIA...BUT IS PRODUCING NO SIGNIFICANT 
WEATHER IN OUR AREA OF RESPONSIBILITY.
 
$$ 
CHRIS LANDSEA