000
AXPZ20 KNHC 281555
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1605 UTC TUE APR 28 2015

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 
1545 UTC. 

...SPECIAL FEATURES...

GULF OF TEHUANTEPEC GALE WARNING...MODEL GUIDANCE IS IN GOOD 
AGREEMENT SHOWING WEAK LOW PRES DEVELOPMENT SE OF TEHUANTEPEC 
AND HIGH PRES BUILDING OVER EASTERN MEXICO WED NIGHT. THIS WILL 
RESULT IN THE TIGHTENING OF THE PRES GRADIENT ACROSS THE ISTHMUS 
TO SUPPORT MINIMAL GALE CONDITIONS IN THE GULF OF TEHUANTEPEC 
THROUGH THU MORNING. SEAS DURING THIS PERIOD WILL BUILD UP TO 13 
FT. GFS MODEL GUIDANCE SHOWS POSSIBILITY OF ANOTHER BRIEF SHOT 
OF GALE FORCE WINDS N OF 15N THU NIGHT.

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

LOW PRES CENTERED NEAR 11N112W WITH SCATTERED MODERATE 
CONVECTION FROM 08N TO 15N BETWEEN 110W AND 116W. THE MONSOON 
TROUGH EXTENDS FROM THE LOW PRESSURE CENTER TO 08N120W TO 
06N127W. THE ITCZ EXTENDS FROM 06N127W TO 07N135W TO 06N140W. 
ISOLATED MODERATE TO STRONG CONVECTION FROM 02N TO 08N E OF 97W. 
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 08N TO 
15N BETWEEN 97W AND 113W AND FROM 03N TO 10N BETWEEN 116W AND 
127W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N OF ITCZ W 
OF 130W.

...DISCUSSION...    

WATER VAPOR IMAGERY SHOWS A MID-UPPER LEVEL TROUGH EXTENDING W 
FROM TEXAS-OKLAHOMA BORDER ACROSS NW MEXICO AND THE CENTRAL BAJA 
PENINSULA TO 26N126W THEN S-SW TO 13N127W. DRY STABLE AIR ALOFT 
IS W OF THE TROUGH AND A SWATH OF TROPICAL MOISTURE IS BEING 
ADVECTED SE OF THE TROUGH FROM ACTIVE CONVECTION OCCURRING E OF 
A LOW PRESSURE CENTER BETWEEN 99W-112W. THE SUBTROPICAL HIGH 
CONTINUES TO WEAKEN AN ADVANCING COLD FRONT THAT EXTENDS FROM 
34N131W TO 28N140W. NW SWELL BEHIND THE COLD FRONT WILL REACH 
THE NW PORTION OF THE AREA WITHIN 6 HOURS THEN QUICKLY SUBSIDE 
WED AS THE DISSIPATING COLD FRONT WEAKENS TONIGHT. ANOTHER SURGE 
OF N-NW SWELL ASSOCIATED WITH STRONG N WINDS ALONG THE 
CALIFORNIA COAST WILL SWEEP S OF 30N INTO NE PORTION OF THE AREA 
WED NIGHT THROUGH THU MORNING.

LOOKING AHEAD...VERY LARGE AREA OF CROSS-EQUATORIAL LONG PERIOD 
SW SWELL WILL BEGIN TO AFFECT S AND SE PORTIONS THU NIGHT AND 
FRI WITH SEAS 9-10 FT AND 19-20 SEC PERIOD. THIS SWELL WILL 
REACH THE WEST COAST OF CENTRAL AMERICA THIS WEEKEND...WITH 
LARGE SURF LIKELY FROM PANAMA TO CENTRAL MEXICO.

$$
RAMOS/NELSON