000
AXPZ20 KNHC 180913
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE DEC 18 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 ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

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

THE MONSOON TROUGH AXIS EXTENDS FROM 10N85W TO 07N95W WHERE LOW 
LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ EXTENDING TO BEYOND 
06N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS NOTED 
WITHIN 120 NM N AND 30 NM S OF ITCZ AXIS W OF 135W.

...DISCUSSION...
HIGH PRESSURE 1040 MB IS CENTERED NW OF THE AREA NEAR 37N153W. 
LOW PRESSURE 1010 MB IS CENTERED INLAND OVER CENTRAL CALIFORNIA 
WITH ASSOCIATED COLD FRONT EXTENDING SW ACROSS THE NW PORTION OF 
THE FORECAST AREA FROM 30N131W TO 25N140W. THE PRESSURE GRADIENT 
BETWEEN THESE FEATURES IS PRODUCING A LARGE AREA OF FRESH TO 
STRONG WINDS TO THE N OF THE COLD FRONT AS DEPICTED BY THE 
LATEST SCATTEROMETER PASSES. THIS SWATH OF WINDS HAS HELPED 
DEVELOP AND USHER IN A NEW SET OF NW SWELLS INTO THE AREA...WITH 
COMBINED SEAS TO 11 FT CURRENTLY OVER THE NW PART OF THE 
FORECAST AREA. 

THE COLD FRONT WILL CONTINUE TO PUSH S AND E OVER THE N PART OF 
THE FORECAST AREA THROUGH THE NEXT COUPLE OF DAYS. THOUGH THE 
SURFACE HIGH PRESSURE WILL WEAKEN OVER THE NEXT 24 HOURS...IT 
WILL SHIFT TO THE SE BRINGING IT CLOSER TO THE FORECAST AREA. 
THIS WILL MAINTAIN THE PRESSURE GRADIENT N OF THE FRONT WITH THE 
FRESH TO STRONG WINDS COVERING MUCH OF THE FORECAST AREA N OF 
20N AND W OF 115W BY EARLY WED. THE SET OF NW SWELLS WILL 
CONTINUE TO SPREAD S AND E OVER THE NEXT 24 HOURS...AND WILL 
PEAK NEAR 14 FT BY LATE TUE/EARLY WED. THE PROXIMITY OF THE HIGH 
PRESSURE CENTER WILL ALSO INCREASE THE PRESSURE GRADIENT WITH 
LOWER PRESSURE IN THE VICINITY OF THE ITCZ. THIS WILL WILL 
STRENGTHEN TRADEWIND FLOW FROM 10N TO 20N W OF 130W BY EARLY 
WED. 

THE AREA OF HIGH PRESSURE WILL FURTHER WEAKEN ON WED...WHICH 
WILL HELP TO DECREASE THE TRADEWINDS AS WELL AS THE WINDS OVER 
THE NORTHERN PART OF THE FORECAST AREA BY LATE WED/EARLY THU. 
THE NW SWELLS WILL CONTINUE TO SPREAD S AND E THROUGH THIS 
TIME...THOUGH SUBSIDING TO 11 FT BY EARLY THU.

GAP WINDS...
LOOKING FORWARD...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. NORTHERLY WINDS WILL START TO 
FUNNEL INTO THE GULF OF TEHUANTEPEC BY THU EVENING...WITH STRONG 
GALE...AND POSSIBLY STORM CONDITIONS...BY FRI MORNING.

$$
AL