000
AXPZ20 KNHC 210931
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL 
1005 UTC SAT DEC 21 2013

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... 

MONSOON TROUGH AXIS EXTENDS FROM 09N84W TO 08N92W...WHERE IT 
TRANSITIONS TO THE ITCZ TO 06N104W TO 09N115W TO 08N124W TO 
10N132W TO 08N140W. SCATTERED MODERATE CONVECTION IS NOTED FROM 
08N TO 10N W OF 135W...AND WITHIN 90 NM S OF THE ITCZ BETWEEN 
118W AND 119.5W. 

...DISCUSSION... 

A STRONG HIGH PRES OF 1033 MB LOCATED NW OF AREA AT 39N140W 
EXTENDS A RIDGE SE ACROSS THE FORECAST WATERS TO NEAR THE 
REVILLAGIGEDO ISLANDS. N TO NE WINDS OF 20-25 KT ARE NOTED PER 
SCATTEROMETER DATA AND A FEW SHIP OBSERVATIONS IN ASSOCIATION 
WITH THIS SYSTEM N OF 24N W OF 125W. SEAS WITHIN THIS AREA ARE 
10-12 FT IN NW SWELL. FARTHER E...AN ALTIMETER PASS SHOWED SEAS 
OF 12 TO 15 KT ACROSS WATERS N OF 25N BETWEEN 118W AND 125W IN 
LONG PERIOD NW SWELLS. WINDS AND SEAS WILL GRADUALLY DIMINISH 
ACROSS THE NORTHERN FORECAST WATERS DURING THE NEXT COUPLE OF 
DAYS. EXPECT WINDS OF 20 KT OR LESS AND SEAS TO 9 FT IN NW SWELL 
N OF 20N W OF 120W BY 48 HOURS. 

THE 1033 MB HIGH IS FORECAST TO MOVE ENE OVER THE NEXT 24-48 
HOURS WHILE SLIGHTLY WEAKENING. THE PRES GRADIENT BETWEEN THE 
HIGH AND LOWER PRES ALONG THE ITCZ CONTINUES TO RESULT IN FRESH 
TO STRONG TRADE WINDS BETWEEN THE RIDGE AND ITCZ...ROUGHLY FROM 
10NN TO 24N W OF 130W AS WAS INDICATED BY A COUPLE OF SHIP 
OBSERVATIONS IN THAT AREA...AND BY THE LATEST ASCAT PASSES. THE 
PRES GRADIENT WILL GRADUALLY RELAX THROUGH TONIGHT AS THE 
AFOREMENTIONED HIGH PRES SLIGHTLY WEAKENS.

VERY LONG PERIOD NW SWELLS...WITH WAVE PERIODS BETWEEN 19-22 SEC 
MOVING ACROSS THE FAR NW PORTION WILL CONTINUE TO PROPAGATE 
THROUGH THESE WATERS TODAY...AND REACH THE REMAINDER OF THE 
WESTERN PART OF THE AREA BY TONIGHT. THESE SWELLS WILL GRADUALLY 
BUILD AS THEY PROPAGATE SEWD ACROSS THE AREA. 

GULF OF TEHUANTEPEC...THE NEXT GAP WIND EVENT IS FORECAST TO 
BEGIN MON MORNING WITH WINDS RAPIDLY INCREASING TO GALE FORCE 
DURING THE AFTERNOON. MARINE GUIDANCE INDICATES THAT WINDS WILL 
FURTHER INCREASE TO 40 KT MON EVENING AND TO 45 KT MON NIGHT 
WITH BUILDING SEAS TO 18-19 FT. THE GALE FORCE GAP WIND EVENT IS 
FORECAST BY THE COMPUTER MODELS TO PERSIST THROUGH TUE NIGHT. 
FRESH WINDS AND SEAS TO 8 FT DOWNSTREAM OF THE GULF WILL REACH 
AS FAR AS 105W BY TUE NIGHT. THIS GAP WIND EVENT WILL BE 
ASSOCIATED WITH A STRONG COLD SURGE BEHIND A COLD FRONT FORECAST 
TO MOVE ACROSS THE WESTERN GULF OF MEXICO LATE SUN INTO MON. 
WHEN COLD AIR OUTBREAKS OCCUR OVER THE GULF OF MEXICO...THE 
SIERRA MADRE MOUNTAINS BLOCK THE LARGE SCALE FLOW OF COLD AIR 
SOUTHWARD RESULTING IN THE DEVELOPMENT OF A STRONG NORTH-SOUTH 
PRES GRADIENT ACROSS THE ISTHMUS OF THE TEHUANTEPEC. NORTHERLY 
FLOW IS THEN FUNNELED THROUGH THE CHIVELA PASS INTO THE GULF OF 
TEHUANTEPEC. THIS GAP FLOW OFTEN RESULTS IN A NARROW JET OF WIND 
THAT CAN REACH GALE...STORM AND OCCASIONALLY HURRICANE FORCE.

PULSING OF NOCTURNAL WINDS ARE EXPECTED ACROSS THE GULF OF 
PAPAGAYO...REACHING 20-25 KT FROM 0600 TO 1200 UTC WITH SEAS OF 
7-8 THROUGH AND DOWNWIND OF THE GULF. THE MOST RECENT ASCAT PASS 
PROVIDED OBSERVATIONS OF THESE WIND SPEEDS. 

GULF OF CALIFORNIA...HIGH PRES WILL BUILD BACK INTO THE REGION 
THIS WEEKEND FROM THE NW...AND INCREASE THE PRES GRADIENT TO 
SUPPORT NW WINDS OF 15-20 KT ACROSS MOST OF GULF OF CALIFORNIA 
ON SUN EVENING. THESE WINDS WILL INCREASE FURTHER LATE SUN NIGHT 
INTO MON. MARINE GUIDANCE SHOWS NW WINDS OF 20-25 KT ACROSS THE 
ENTIRE GULF BY MON MORNING WITH SEAS BUILDING TO NEAR 7 FT LATER 
ON THIS DAY.
 
$$
GR