000
AXPZ20 KNHC 280933
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1005 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 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 SE MEXICO...TIGHTENING THE PRES 
GRADIENT ACROSS THE ISTHMUS TO SUPPORT MINIMAL GALE CONDITIONS 
IN THE GULF OF TEHUANTEPEC WED NIGHT. SEAS WILL BUILD TO 12-13 
FT BY LATE WED NIGHT. GFS MODEL GUIDANCE SHOWS POSSIBILITY OF 
ANOTHER BRIEF SHOT OF GALE FORCE WINDS N OF 15N THU NIGHT.

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

MONSOON TROUGH FROM 11N99W TO 11N112W TO 09N117W. 1011 MB LOW 
PRES CENTERED NEAR 08N118W WITH MINIMAL CONVECTION. ITCZ FROM 
08N121W TO 08N134W TO 06N140W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION FROM 06N TO 13N BETWEEN 98W AND 113W...AND 
WITHIN 30 NM OF AXIS BETWEEN 121W AND 126W.

...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 NEAR 
THE MONSOON TROUGH BETWEEN 98W-113W.

AN ADVANCING COLD FRONT THAT EXTENDS FROM 40N129W TO 30N140W TO 
25N150W IS WEAKENING THE SUBTROPICAL HIGH...CAUSING TRADE WINDS 
S OF THE SUBTROPICAL RIDGE TO DIMINISH. SCATTEROMETER DATA SHOWS 
A MARKED DECREASE IN E-NE WINDS W OF 120W DURING THE PAST 24 
HOURS. NW SWELL BEHIND THE COLD FRONT WILL REACH THE NW PORTION 
OF THE AREA WITHIN 6 HOURS THEN QUICKLY BECOME DIFFUSE THROUGH 
WED AS THE DYING FRONT RAPIDLY 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.

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 10-12 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.

$$
MUNDELL