000
AXPZ20 KNHC 291546
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE MAY 29 2012

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1445 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS SW FROM COSTA RICA AT 10N85W TO 
07N94W...THEN TURNS NW TO 12N107W...GENTLY TURNING SW TO A 
SURFACE LOW PRES EMBEDDED WITH THE MONSOON TROUGH GYRE NEAR 
09N113W...WITH THE TROUGH AXIS THEN CONTINUING SW TO 07N120W 
WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ WHICH 
CONTINUES WESTWARD ALONG 07N TO BEYOND 140W. 

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED OVER 
THE NW QUADRANT OF THE EMBEDDED SURFACE LOW...WITHIN ABOUT 30 NM 
OF 11.5N113.5W. LARGE CLUSTERS STRONG CONVECTION ARE OBSERVED S 
OF THE MONSOON TROUGH AXIS...FROM 03N TO 09N TO THE E OF 102W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION SURROUNDS THE 
MONSOON TROUGH AND ITCZ OVER THE WATERS FROM 04N TO 10N BETWEEN 
113W AND 128W.

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED ALONG 
THE CENTRAL AMERICAN COAST WITHIN ABOUT 15 NM OF 11.5N86.5W AND 
15N99.5W.

...DISCUSSION...

AN UPPER TROUGH AXIS EXTENDS SW FROM NW CORNER OF THE CONUS AT 
50N124W TO A BASE JUST E OF THE HAWAIIAN ISLANDS. UPPER MOISTURE 
IS NOTED NW OF THE TROUGH AXIS AND IS NOW SPILLING S INTO THE 
FAR NW PORTION OF THE DISCUSSION AREA. ONLY THE SLIGHTEST HINT 
OF UPPER MOISTURE IS INDICATED E OF THE TROUGH AXIS...WITHIN 90 
NM EITHER SIDE OF A LINE FROM 17N140W TO 28N116W. OTHERWISE THE 
UPPER LEVELS APPEAR VERY DRY N OF 25N BETWEEN 100W AND 140W... 
AND S OF 25N BETWEEN 127W AND 140W. AN UPPER LEVEL ANTICYCLONE 
IS CENTERED AT 17N108W WITH A RIDGE EXTENDING SW TO 07N126W AND 
A SECOND RIDGE EXTENDING NE TO A COLLAPSING CREST OVER CENTRAL 
OLD MEXICO AT 26N101W. THE ASSOCIATED UPPER DIFFLUENCE IS 
ENHANCING CONVECTION NEAR THE SURFACE LOW NEAR 09N113W AND ALSO 
ALONG THE MONSOON TROUGH AND ITCZ BETWEEN 113W AND 128W AS 
PREVIOUSLY DESCRIBED. THE RESULTANT DEBRIS MOISTURE IS TRAPPED 
WITHIN THE UPPER ANTICYCLONIC FLOW...EXCEPT FOR A SMALL AREA 
EVAPORATING OVER WESTERN OLD MEXICO AT 21N103W. AN UPPER CYCLONE 
IS FORECAST TO CUT OFF NEAR 23N142W OVER THE NEXT COUPLE OF DAYS 
AND MOVE W EFFECTIVELY RETROGRADING THE UPPER TROUGH AND UPPER 
ANTICYCLONE PATTERN WESTWARD...ALLOWING THE UPPER DIFFLUENCE 
ASSOCIATED WITH THE ANTICYCLONE TO SHIFT W IN PHASE WITH THE 
SURFACE LOW AND THE MONSOON TROUGH AND ITCZ...THUS CONVECTION 
MAY PERSIST. AT THE LOW LEVELS A BROAD RIDGE HAS AN AXIS 
EXTENDING FROM 32N140W TO 15N105W BUT IS FORECAST TO SHIFT W. 
NORTHERLY FLOW AT 15 TO 20 KT NE OF THE RIDGE TO BAJA CALIFORNIA 
PENINSULA WILL CONTINUE TO SPREAD S FOR THE NEXT FEW DAYS. NE 
TRADES ARE ENHANCED TO 15 TO 20 KT SW OF THE RIDGE OVER THE AREA 
FROM 07N TO 20N W OF 130W BUT THIS AREA OF ENHANCED TRADES 
SHOULD SHRINK OVER THE NEXT FEW DAYS.    
 
AN UPPER TROUGH EXTENDS SW ALONG THE EASTERN SEABOARD OF THE 
CONUS...DISSECTING THE GULF OF MEXICO FROM NE TO SW AND THROUGH 
AN EMBEDDED UPPER CYCLONE OVER THE MEXICO/GUATEMALA BORDER... 
WITH THE TROUGH CONTINUING S TO BASE OVER THE DEEP TROPICAL 
PACIFIC AT 07N98W. AN UPPER ANTICYLONE IS OVER COLOMBIA WITH ITS 
ENVELOPE OF ANTICYCLONIC FLOW DOMINATING THE TROPICS BETWEEN 90W 
AND 60W PROVIDING UPPER SUPPORT FOR CONVECTION OVER AND S OF 
CENTRAL AMERICA. THE DEBRIS MOISTURE IS ADVECTED NE ACROSS THE W 
CARIBBEAN AND SPILLING E OVER THE BAHAMAS...THEN SE OVER THE NE 
CARIBBEAN. DRY UPPER AIR IS ADVECTED S ACROSS THE GULF OF MEXICO 
AND MEXICO WITHIN 500 NM W OF THE EASTERN TROUGH AXIS.
LITTLE CHANGE EXPECTED IN THIS PATTERN OVER THE NEXT FEW DAYS.

$$
NELSON