000
AXPZ20 KNHC 120930
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1005 UTC SUN MAY 12 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

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

A MONSOON TROUGH EXTENDS FROM 09N80W TO 08N100W THEN TRANSITIONS 
TO THE ITCZ TO 10N107W TO 07N140W. SCATTERED MODERATE TO STRONG 
CONVECTION IS FROM 09N TO 12N BETWEEN 89W AND 90W AND SCATTERED 
MODERATE CONVECTION IS WITHIN 60 NM EITHER SIDE OF THE ITCZ AXIS 
BETWEEN 110W AND 130W.

...DISCUSSION... 

A 1024 MB HIGH PRESSURE CENTER IS LOCATED NEAR 30N130W WITH A 
RIDGE EXTENDING SW TO BEYOND 22N140W AND SE TO NEAR 15N108W. THE 
PRESSURE GRADIENT BETWEEN THE AREA OF HIGH PRESSURE AND LOWER 
PRESSURE IN THE VICINITY OF THE ITCZ IS MAINTAINING MODERATE TO 
FRESH TRADES WITHIN 600 NM N OF THE ITCZ AXIS W OF 115W BASED ON 
SCATTEROMETER DATA. CONVERGENCE INTO THE ITCZ IS TRIGGERING 4-6 
HOUR PERIODS OF VERY ACTIVE CONVECTION ALONG THE BOUNDARY. 

A WEAK COLD FRONT IS DRIFTING SLOWLY WEST IN THE FAR NW PART OF 
THE FORECAST AREA WILL STALL AND BECOME A DIFFUSE TROUGH LATER 
TODAY AS THE SUPPORTING UPPER LOW OVER THE N CENTRAL PAC LIFTS 
OUT TO THE NE. HIGH PRES BEHIND THE FRONTAL TROUGH WILL BUILD 
EASTWARD AND MAINTAIN AN AREA OF MODERATE TO FRESH TRADES AND 
SEAS TO 7-8 FT JUST NORTH OF THE CONVERGENCE ZONE CONVECTION. 

A WEAK LOW EMBEDDED WITHIN THE MONSOON TROUGH NEAR THE W COAST 
OF COSTA RICA IS EXPECTED TO DRIFT WESTWARD ACROSS THE TROPICAL 
E PACIFIC THROUGH MID-WEEK. IN ADDITION TO ENHANCED CONVECTION 
IN THE MONSOON TROUGH...THE MAIN EFFECT WILL BE GREATER EARLY 
MORNING DRAINAGE FLOW THROUGH THE GULF OF PAPAGAYO SUN MORNING 
AND MON MORNING TO 20 KT...EVEN BRIEFLY REACHING 25 KT. ONCE THE 
TROUGH AND LOW PRESSURE SHIFTS FAR ENOUGH TO THE WEST...IT WILL 
INDUCE GAP WINDS TO 30 KT THROUGH THE GULF OF TEHUANTEPEC. 
  
$$
MUNDELL