000
AXPZ20 KNHC 280242
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
0405 UTC SUN APR 28 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0200 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...           
THE MONSOON TROUGH EXTENDS FROM COLOMBIA NEAR 08N72W TO 05N79W 
TO 08N91W...WHERE IT TRANSITIONS TO THE INTERTROPICAL 
CONVERGENCE ZONE...CONTINUING ON 07N103W TO 05N118W...WHERE IT 
BREAK IN THE VICINITY OF A SURFACE TROUGH ALONG 121W...THEN 
RESUMES NEAR 05N125W TO 08N130W TO BEYOND 08N140W. SCATTERED 
MODERATE TO STRONG CONVECTION NOTED WITHIN 150 NM S OF MONSOON 
TROUGH BETWEEN 79W AND 90W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION NOTED WITHIN 90 NM N AND 150 NM S OF ITCZ BETWEEN 
108W AND 133W. 
     
...DISCUSSION...                                             

A STRONG BLOCKING PATTERN PREVAILS ACROSS THE NORTHEAST PACIFIC 
THIS EVENING. UPPER LEVEL SOUTHWESTERLY FLOW DOMINATES MOST OF 
THE DISCUSSION AREA N OF 10N W OF 120W...BETWEEN AN ANTICYCLONIC 
CIRCULATION CENTERED NEAR 12N103W AND A PAIR OF UPPER LEVEL LOWS 
AND ASSOCIATED TROUGHING EXTENDING FROM 34N131W TO 28N140W TO A 
BASE NEAR 19N150W. THE UPPER ANTICYCLONE ANCHORS A RIDGE S OF 
22N THAT SPANS BETWEEN 85W AND 122W. WATER VAPOR IMAGERY 
INDICATES MODERATE TO STRONG DRY AIR AND SUBSIDENCE WITHIN THE 
UPPER LEVEL TROUGH MEANDERING ACROSS N AND NW PORTIONS OF THE 
AREA. THE MOST SIGNIFICANT CONVECTION REMAINS FOCUSED NEAR AND TO 
THE E OF A SURFACE TROUGH ANALYZED ALONG 121W FROM 07N TO 
14N....WHILE MID LEVEL CYCLONIC TURNING IS NOTED IN SATELLITE 
IMAGERY OCCURRING TO THE E OF THE SURFACE TROUGH CENTERED NEAR 
10N113W. RECENT GFS ANALYSIS INDICATE THAT THE MID LEVEL 
PERTURBATION SEEN IN SATELLITE IMAGERY ALONG 113W HAS BEEN IN 
FAVORABLE ATMOSPHERIC CONDITIONS FOR BAROTROPIC GROWTH DURING 
THE PAST 24 HOURS... LEADING TO THE IMPROVED CYCLONIC 
CIRCULATION. ADDITIONALLY... THIS FEATURE IS ALMOST DIRECTLY 
UNDERNEATH THE UPPER LEVEL ANTICYCLONE ALLOWING FOR OPTIMUM 
CONVECTIVE OUTFLOW. GLOBAL MODELS FORECAST THIS MID LEVEL 
PERTURBATION TO CONTINUE TO SHIFT W AND WEAKEN DURING THE NEXT 
24-36 HOURS...WITH ASSOCIATED CONVECTION SLOWLY WANING AS WELL.

AT THE SURFACE...A 1032 MB HIGH IS CENTERED WELL NW OF THE AREA 
NEAR 40N140W AND EXTENDS A RIDGE SE TO NEAR 16N107W...AND S 
ACROSS SW PORTIONS OF THE AREA. AFTERNOON ASCAT PASSES SHOWED 
FRESH NE TRADES 20-25 KT OCCURRING FROM JUST W OF THE SURFACE 
TROUGH TO 150W...AND GENERALLY BETWEEN 10N AND 16N. SEAS IN THIS 
ZONE ARE RUNNING 7 TO 9 FT IN MERGING NE WIND SWELL AND SOUTHERN 
HEMI SW SWELL. THE WAVE MENTIONED ABOVE AND SURFACE TROUGH WILL 
BOTH MOVE W AND WEAKEN DURING THE NEXT COUPLE OF DAYS...WITH THE 
ZONE OF FRESH TRADES GRADUALLY DIMINISHING.
 
FOR THE REMAINDER OF THE EASTERN PACIFIC BASIN E OF 110W... 
RELATIVELY TRANQUIL CONDITIONS ARE NOTED IN OBSERVATIONAL 
DATA...RECENT SCATTEROMETER PASSES...AND LATEST GLOBAL MODEL 
DATA. OF NOTE...SW SWELL FROM A SOUTHERN HEMISPHERE LOW PRESSURE 
SYSTEM WILL CONTINUE SPREADING NORTHEASTWARD AND REACH THE 
MEXICAN AND CENTRAL AMERICAN COAST BY EARLY MONDAY WITH WAVE 
PERIODS IN THE RANGE OF 15 TO 17 SECONDS.

$$
STRIPLING