000
AXPZ20 KNHC 190954
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU MAY 19 2011

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0945 UTC.
 
...ITCZ...
THE MONSOON TROUGH EXTENDS FROM 10N84W TO THE ITCZ AXIS NEAR  
05N115W...WITH THE ITCZ CONTINUING W TO BEYOND 04N140W. ISOLATED 
MODERATE TO STRONG CONVECTION IS OBSERVED FROM 05N TO 11N 
BETWEEN 84W AND 110W...AND ALSO WITHIN 30 NM OF COAST OF CENTRAL 
AMERICA FROM 87W TO 98W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS WITHIN 150 NM EITHER SIDE OF A LINE FROM 05N126W 
TO 03N140W.

...DISCUSSION...
AN UPPER LEVEL TROUGH EXTENDS SW FROM THE EXTREME SOUTHERN 
CALIFORNIA TO 27N119W TO 25N138W...AND THEN INTO UPPER CYCLONE 
AT 20N140W...WITH THE TROUGH THEN EXTENDING SE TO 08N142W. A 
NARROW BAND OF DRY UPPER AIR EXTENDS W FROM EXTREME SE TEXAS 
ACROSS OLD MEXICO AND THE BAJA CALIFORNIA PENINSULA ALONG 25N TO 
25N130W WHERE IT TURNS SW AROUND THE W SEMICIRCLE OF THE CYCLONE 
EVENTUALLY RETURNING INTO THE AREA NEAR 18N137W. A BAND OF UPPER 
MOISTURE HAS ROTATED AROUND THE E SEMICIRCLE OF THE CYCLONE... 
OVER THE AREA FROM 15N TO 23N BETWEEN 128W AND 138W. IMMEDIATELY 
TO N OF THE NARROW BAND OF DRY UPPER AIR IS UPPER MOISTURE 
SHIFTING S INTO THE DISCUSSION AREA W OF 128W AND SHIFTING SE 
OVER THE AREA E OF 128W TO AS FAR E AS TEXAS.

AN UPPER ANTICYCLONE IS ESTIMATED NEAR 10N109W WITH AN UPPER 
RIDGE EXTENDING SW TO A SHARP CREST AT 07N134W...AND AN UPPER 
RIDGE EXTENDS E TO ANOTHER FAIRLY SHARP CREST OVER PANAMA AT 
09N80W. AN UPPER RIDGE ALSO EXTENDS N NOW BECOMING FLAT ALONG 
22N BETWEEN 120W AND 105W. THE ASSOCIATED UPPER DIFFLUENCE HAS 
ENHANCED ITCZ CONVECTION BETWEEN 122W AND 142W WITH THE DEBRIS 
MOISTURE ADVECTED NE TO NEAR 18N125W. UPPER DIFFLUENCE HAS 
SUPPORTED CONVECTION OVER THE TROPICS BETWEEN 82W AND 109W WITH 
THE DEBRIS MOSITURE SPREADING S ACROSS THE EQUATOR BETWEEN 85W 
AND 105W. THE UPPER LEVELS APPEAR DRY OVER THE DISCUSSION AREA 
FROM 12N TO 26N BETWEEN E OF 120W ACROSS CENTRAL OLD MEXICO AND 
THE WESTERN GULF OF MEXICO. 

THE UPPER CYCLONE IS EXPECTED TO MEANDER NEAR 22N140W THROUGH 
SAT WHILE THE UPPER RIDGE CONTINUES STATIONARY BUT AMPLIFIES N 
OVER THE THE BAJA CALIFORNIA PENINSULA DISRUPTING THE UPPER 
ZONAL FLOW.
 
AT THE LOW LEVELS A COLD FRONT IS LOSING IDENTITY FROM THE 
NORTHERN GULF OF CALIFORNIA TO NEAR 26N125W. A BROAD SURFACE 
RIDGE EXTENDS FROM 27N140W TO NEAR 17N113W. THE LOW NORTHERLY 
FLOW CONTINUES TO PULSE AT 15 TO 20 KT WITHIN ABOUT 240 NM W OF 
THE BAJA CALIFORNIA PENINSULA AND NE TRADES TO THE S OF THE 
RIDGE CONTINUE TO PULSE AT 15 TO 20 KT OVER THE AREA FROM 08N TO 
15 W OF 130W. CROSS EQUATORIAL SOUTHERLY SWELLS CONTINUE TO MIX 
WITH NORTHERLY SWELLS OVER THE WATERS W OF 105W. SOUTHERLY 
SWELLS CONTINUE OVER THE ENTIRE AREA E OF 105W INTERRUPTED ONLY 
BY THE EFFECTS GALAPAGOS ISLANDS.  

A LOW LEVEL TROUGH IS EXPECTED TO DEVELOP WITHIN THE ITCZ FROM 
11N103W TO 07N107W ON FRI...AND DRIFT W FOR A COUPLE OF DAYS 
BEFORE DISSIPATING.

$$
NELSON