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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

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