000
AXPZ20 KNHC 291549
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI APR 29 2011

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ANALYZED FROM 06N77W 
TO 03N97W TO 07N117W TO 04N140W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION NOTED WITHIN 150 NM OF AXIS BETWEEN 87W AND 
91W. SCATTERED MODERATE TO STRONG CONVECTION NOTED WITHIN 300 NM 
N AND 150 NM S OF AXIS BETWEEN 100W AND 109W. SCATTERED TO 
LOCALLY NUMEROUS MODERATE TO STRONG CONVECTION NOTED ALONG AXIS 
IN VICINITY OF A SURFACE TROUGH ALONG 116/117W...OCCURRING FROM 
05N TO 11N BETWEEN 115W AND 124W.

...DISCUSSION...
W OF 110W...A SMALL BUT VERY WELL DEFINED UPPER LEVEL CYCLONE 
CENTERED NEAR 27N138W CONTINUED LIFTING QUICKLY N-NE THIS 
MORNING...AND WAS BEGINNING TO REACH THE W FLANKS OF A BROAD 
FLAT UPPER RIDGE ACROSS MUCH OF THE REMAINDER OF THE AREA TO THE 
E. ASIDE FROM AREAS OF MID AND HIGH LEVEL CLOUDINESS IN THE 
CENTER AND TO THE SE OF THIS LOW...IT IS HAVING LITTLE IMPACT AT 
THE SURFACE AS IT MOVES NE AND WEAKENS TODAY. THE MAIN INFLUENCE 
ACROSS NW PORTIONS REMAINS THE DEEP LAYER RIDGE ALONG 140W TO 
THE N OF THE UPPER CYCLONE...SUPPORTING A 1035 MB HIGH PRES 
CENTER NEAR 43N137W. THIS SURFACE HIGH WILL STRENGTHEN SLIGHTLY 
AND SHIFT SLOWLY NE THROUGH SAT AS THE UPPER LEVEL PATTERN 
BECOMES AMPLIFIED. SHIP OBSERVATIONS ON EITHER SIDE OF AN E-W 
ORIENTED COLD FRONT ALONG ROUGHLY 30N SHOW THE FRONT WEAKENING 
AS IT SAGS S. FRESH TO STRONG NORTHERLY WINDS PERSIST S OF THE 
HIGH PRES N OF 20N. SEAS OF 8 TO 9 FT IN NE SWELL WILL INCREASE 
TO 12 FT IN N SWELL OFF OF THE NORTHERN BAJA COAST BY TONIGHT. 
FURTHER S...A NEGATIVE TILT UPPER TROUGH EXTENDS FROM 21N129W TO 
06N122W. MODERATE TRADE WIND CONVERGENCE IS MAINTAINING A LARGE 
CLUSTER OF MODERATE TO STRONG CONVECTION NEAR THE ITCZ BETWEEN 
100W AND 122W...WHICH HAS PERSISTED ACROSS THIS REGION FOR THE 
PAST FEW WEEKS...HELPING TO MAINTAIN DIFFLUENT FLOW ALOFT.
E OF THESE UPPER FEATURES PREVAILS A BROAD FLAT RIDGE GENERALLY 
N OF 13N THE EXTENDS N TO 30N AND E ACROSS MEXICO. 

AT LOW LEVELS E OF 110W...LIGHT AND VARIABLE WINDS CONTINUE AT 
THE SURFACE...WITH WEAK MONSOONAL FLOW E OF 90W. THE MAIN ISSUE 
WILL BE STRONG NLY WIND FLOW THROUGH THE GULF OF TEHUANTEPEC 
THIS MORNING AS A COLD FRONT STALLS ACROSS THE SW GULF OF 
MEXICO. THESE WINDS WILL BE RELATIVELY SHORT-LIVED...TYPICAL OF 
SPRING TIME EVENTS...AND WILL DIMINISH TO LESS THAN 20 KT 
TONIGHT. FURTHER S...FRESH GAP WINDS HAVE ALSO BECOME ACTIVE 
THROUGH THE  GULF OF PAPAGAYO DUE TO SLIGHTLY ENHANCED TRADE 
WINDS OVER THE CARIBBEAN AND WILL COMBINE WITH DRAINAGE EFFECTS 
TO RENDER GAP FLOW TO 20 KT TODAY THROUGH THE WEEKEND. 

GULF OF CALIFORNIA...NW WINDS WILL INCREASE OVER THE NORTHERN 
PORTION OF THE GULF BETWEEN LOW PRES OVER NW MEXICO AND HIGH 
PRES OVER THE NE PACIFIC BY SAT MORNING AND THEN SPREAD S TO 25N 
THROUGH SUN...BUILDING SEAS IN EXCESS OF 6 FT. 

$$
STRIPLING