000
AXPZ20 KNHC 190917
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED DEC 19 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 09N84W TO 06N96W WHERE LOW LEVEL 
WINDS INDICATE A TRANSITION TO ITCZ WHICH EXTENDS WESTWARD TO 
BEYOND 07N140W. SCATTERED MODERATE CONVECTION WAS NOTED WITHIN 
90 NM N OF AXIS BETWEEN 120W AND 130W.

...DISCUSSION...
HIGH PRESSURE 1034 MB IS CENTERED NW OF THE AREA NEAR 33N147W 
WITH SURFACE RIDGE EXTENDING EASTWARD TO NEAR 34N123W. LOW 
PRESSURE 1000 MB IS CENTERED OVER NORTHERN ARIZONA WITH 
ASSOCIATED COLD FRONT EXTENDING SW ACROSS NORTHERN BAJA 
PENINSULA TO 21N130W WHERE IT BEGINS TO DISSIPATE EXTENDING TO 
22N140W. THE PRESSURE GRADIENT BETWEEN THESE FEATURES IS 
SUPPORTING FRESH TO STRONG N TO NE WINDS N OF THE FRONT. NW 
SWELLS CONTINUE TO SPREAD S AND E ACROSS THE FORECAST 
AREA...WITH COMBINED SEAS NEAR 13 FT OVER THE NORTHERN PART OF 
THE FORECAST AREA. THE PRESSURE GRADIENT BETWEEN THE RIDGE AND 
LOWER PRESSURE IN THE VICINITY OF THE ITCZ IS MAINTAINING A 
SMALL AREA OF FRESH TO STRONG TRADEWINDS FROM 11N TO 18N W OF 
135W. 

THE HIGH PRESSURE CENTER WILL SHIFT EASTWARD TO A POSITION JUST 
N OF THE FORECAST AREA WHILE TO THE COLD FRONT WILL DISSIPATE 
OVER THE NEXT 24 HOURS. THE PRESSURE GRADIENT WILL RELAX AND 
WINDS WILL DIMINISH BELOW 25 KT BY EARLY THU. WITH THE HIGH 
PRESSURE CENTER WEAKENING...THE PRESSURE GRADIENT WILL ALSO 
RELAX ENOUGH TO DIMINISH TRADEWINDS BELOW 25 KT BY THU NIGHT. 
THE NW SWELL WILL CONTINUE TO SPREAD S AND E WHILE CONTINUING TO 
SUBSIDE...WITH SEAS 8 TO 11 FT COVERING MUCH OF THE FORECAST 
AREA N OF 15N AND W OF 115W BY THU NIGHT. 

A SECOND COLD FRONT WILL ENTER THE NW PART OF THE FORECAST AREA 
THU NIGHT. THOUGH WINDS BEHIND THE FRONT WILL REMAIN BELOW 
ADVISORY CRITERIA...THIS 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 AREA BY EARLY FRI...AND WILL PEAK NEAR 18 FT BY FRI 
NIGHT BEFORE STARTING TO SLOWLY SUBSIDE.  
 
GAP WINDS...
A COLD FRONT WILL SHIFT RAPIDLY ACROSS THE GULF OF MEXICO ON 
THU. WINDS BEHIND THIS FRONT WILL FUNNEL THROUGH THE CHIVELA 
PASS INTO THE GULF OF TEHUANTEPEC WHICH WILL LEAD TO A STRONG 
GAP WIND EVENT. STRONG NORTHERLY WINDS WILL START TO FUNNEL INTO 
THE GULF OF TEHUANTEPEC BY THU EVENING AND WILL RAPIDLY INCREASE 
TO STORM FORCE BY EARLY FRI. 

$$
AL