000
AXPZ20 KNHC 111515
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1605 UTC SAT MAY 11 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

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

THE MONSOON TROUGH EXTENDS FROM LOW PRES 1010 MB NEAR 09N84W TO 
11N99W...THEN TRANSITIONS TO AN ITCZ WHICH EXTENDS WEST TO 
09N120W TO 06N140W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION IS WITHIN 60 NM OF THE ITCZ AXIS BETWEEN 105W AND 
135W.

...DISCUSSION...

W OF 110W...A DEEP LAYER RIDGE ALONG ROUGHLY 130W WITH AN 
ASSOCIATED HIGH PRES AREA CENTERED NEAR 30N130W WILL WEAKEN 
SLIGHTLY TODAY AHEAD OF A WEAK FRONTAL BOUNDARY APPROACHING FROM 
THE WEST. AN ASCAT PASS FROM 05 UTC INDICATED MOSTLY 15 TO 20 KT 
TRADE WINDS S OF THE RIDGE FROM 10N TO 20N. A JASON ALTIMETER 
PASS FROM 04 UTC HOWEVER INDICATED AN AREA OF 20 TO 25 KT WINDS 
AND SEAS IN EXCESS OF 8 FT. TRADE WIND CONVERGENCE IS SUPPORTING 
CLUSTERS OF CONVECTION ALONG THE ITCZ BETWEEN 110W AND 130W. THE 
FRONT IS IN THE PROCESS OF STALLING AND BECOMING DIFFUSE. THE 
SUPPORTING UPPER LOW OVER THE N CENTRAL PACIFIC WILL LIFT NE 
THROUGH SUN. HIGH PRES BEHIND THE DYING FRONT WILL BUILD E ON 
SUN AND MERGE WITH THE HIGH PRES NEAR 130W. GLOBAL MODELS 
INDICATE THIS PATTERN WILL MAINTAIN GENTLE TO FRESH TRADES 
ACROSS THE TROPICAL E PACIFIC THROUGH EARLY NEXT WEEK.

GULF OF CALIFORNIA...A SHARP MID/UPPER TROUGH FROM THE CENTRAL 
PLAINS THROUGH CENTRAL BAJA IS EXPECTED TO CUT OFF THROUGH SUN. 
CONSENSUS AMONG THE GFS...ECMWF...AND TO A LESSER EXTENT THE 
UKMET...CALLS FOR A WEAK SURFACE LOW OR TROUGH TO FORM OVER THE 
CENTRAL GULF OF CALIFORNIA SUN AND DRIFT W TO THE CENTRAL BAJA 
COAST MON BEFORE DISSIPATING TUE. 

E OF 110W...SURFACE OBSERVATIONS AT DAVID IN WESTERN PANAMA 
(MPDA) AND LIBERIA IN NW COSTA RICA (MRLB) INDICATE PRES AROUND 
1010 MB. THIS BOLSTERS THEORIES THAT THERE IS A SURFACE LOW PRES 
AREA CENTERED ALONG THE MONSOON TROUGH OVER THE PACIFIC COAST OF 
COSTA RICA. THIS LOW HAS BEEN WELL ADVERTISED BY OPERATIONAL AND 
ENSEMBLE MODELS OVER THE PAST SEVERAL DAYS...AND IS EXPECTED TO 
DRIFT WESTWARD INTO THE TROPICAL NE PACIFIC THROUGH MID WEEK. 
THE MAIN IMPACT MAY BE WINDS TO 20 KT OVER THE NORTHERN GULF 
LATE SUN. ASIDE FROM INCREASED CONVECTION ALONG THE MONSOON 
TROUGH...THE MAIN IMPACT WILL BE INCREASED EARLY MORNING 
DRAINAGE FLOW THROUGH THE GULF OF PAPAGAYO SUN MORNING AND MON 
MORNING AT LEAST TO 20 KT. BY EARLY MON...THE LOW PRES MOVES W 
TO 95W. THE COMBINATION OF LOWER PRES S OF THE GULF OF 
TEHUANTEPEC AND HIGH PRES BUILDS OVER THE GULF OF MEXICO WILL 
CREATE ENOUGH OF A PRES GRADIENT THROUGH TEHUANTEPEC TO SUPPORT 
25 TO 30 KT GAP FLOW BY EARLY MON. THE GFS SHOWS A STRONGER PUSH 
MON NIGHT/EARLY TUE FOR THE SAME REASONS. LOOKING AHEAD TO MID 
WEEK...GLOBAL MODELS INDICATE THE LOW PRES AS FAR W AS 100W 
WITH MORE MODEST EARLY MORNING GAP FLOW WED MORNING.
  
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CHRISTENSEN