000
AXPZ20 KNHC 200909
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU DEC 20 2012

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM 10N84W TO 07N90W WHERE LOW LEVEL 
WINDS SUGGEST A TRANSITION TO ITCZ WHICH EXTENDS WESTWARD TO 
BEYOND 07N140W. THERE NO SIGNIFICANT CONVECTION.

...DISCUSSION...
THE COLD FRONT THAT SHIFTED ACROSS THE N PART OF THE FORECAST 
AREA THE PAST COUPLE OF DAYS HAS DISSIPATED. HIGH PRESSURE 1028 
MB IS CENTERED JUST N OF THE FORECAST AREA NEAR 31N126W. THIS 
FEATURE HAS WEAKENED OVER THE PAST 24 HOURS WHICH HAS LOOSENED 
THE PRESSURE GRADIENT OVER THE AREA...AND TRADES HAVE DIMINISHED 
TO 20 KT OR LESS. THE REGIONAL WATERS ARE DOMINATED BY LONG 
PERIOD NW SWELL AND NE WIND WAVES. THE NW SWELL WILL CONTINUE TO 
SPREAD S AND E WHILE CONTINUING TO SUBSIDE...WITH SEAS OF 8 TO 
10 FT COVERING MUCH OF THE AREA FROM 08N TO 20N W OF 115W BY 
EARLY SAT. 

THE HIGH PRESSURE CENTER MENTIONED ABOVE WILL CONTINUE TO WEAKEN 
WHILE MOVING INTO THE FORECAST AREA OVER THE NEXT 24 HOURS. THIS 
WILL ENABLE A COLD FRONT TO MOVE INTO THE NW PART OF THE 
FORECAST AREA BY EARLY FRI. THOUGH WINDS ASSOCIATED WITH THIS 
FRONTAL BOUNDARY WILL BE BELOW ADVISORY CRITERIA...THE FRONT 
WILL USHER IN A FRESH SET OF NW SWELLS INTO THE AREA. SEAS WILL 
REACH NEAR 15 FT OVER THE FAR NW PART OF THE FORECAST REGION BY 
EARLY FRI EVENING...AND WILL PEAK NEAR 19 FT BY FRI AFTERNOON 
BEFORE STARTING TO SLOWLY SUBSIDE.  
 
GAP WINDS...
ATTENTION REMAINS FOCUSED ON THE NEXT GULF OF TEHUANTEPEC WIND 
EVENT...FORECAST TO BE THE FIRST STORM FORCE WIND EVENT OF THE 
2012-2013 COLD SEASON. THIS GAP WIND EVENT WILL BE ASSOCIATED 
WITH A STRONG COLD FRONT FORECAST TO MOVE RAPIDLY ACROSS THE 
GULF OF MEXICO ON TODAY. WINDS BEHIND THIS FRONT WILL FUNNEL 
THROUGH THE CHIVELA PASS INTO THE GULF OF TEHUANTEPEC. STRONG 
NORTHERLY WINDS WILL START TO FUNNEL INTO THE GULF OF 
TEHUANTEPEC BY THIS EVENING AND WILL RAPIDLY INCREASE TO STORM 
FORCE BY EARLY FRI. SEAS ARE EXPECTED TO BUILD IN EXCESS OF 
15-20 FT IN ASSOCIATION WITH THESE STORM FORCE WINDS BY FRI 
MORNING. 

WINDS ACROSS THE GULF OF PAPAGAYO ARE PULSING TO 20 KT DURING 
THE OVERNIGHT AND EARLY MORNING HOURS WITH THE ASSISTANCE OF THE 
NOCTURNAL DRAINAGE FLOW. AS THE TRADE WIND FLOW INCREASES ACROSS 
THE SW CARIBBEAN BY FRI...EXPECT NE TO E WINDS OF 20-30 KT AND 
SEAS BUILDING TO NEAR 12 FT IN AND DOWNSTREAM OF THE GULF OF 
PAPAGAYO BY SAT AFTERNOON.

$$
AL