000
AXPZ20 KNHC 162154
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED DEC 16 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2145 UTC.               
 
...SPECIAL FEATURE...

A GALE WARNING IS IN EFFECT FOR THE GULF OF TEHUANTEPEC. A
STRONG COLD FRONT CURRENTLY EXTENDING FROM SW LOUISIANA TO
TAMPICO MEXICO IS FORECAST TO REACH THE CENTRAL BAY OF CAMPECHE
THU EVENING. NORTHERLY WINDS BEHIND THE FRONT WILL BEGIN TO
SPILL THROUGH THE ISTHMUS OF TEHUANTEPEC THU EVENING AND QUICKLY
REACH GALE FORCE AFTER MIDNIGHT THU NIGHT. A 1030 MB HIGH PRES
CENTER WILL MOVE INTO SOUTH-CENTRAL TEXAS BEHIND THE COLD FRONT
ON FRI PRODUCING A VERY STRONG PRES GRADIENT ACROSS THE ISTHMUS
OF TEHUANTEPEC AND FORCING A VERY STRONG AND BROAD GULF OF
TEHUANTEPEC GAP WIND EVENT FRI THROUGH THE UPCOMING
WEEKEND...WITH WINDS EXPECTED TO REACH STORM FORCE...50-55 KT...
LATE FRI AFTERNOON AND FRI NIGHT...BEFORE WINDS DIMINISH
SLIGHTLY TO THE 40-45 KT RANGE LATE FRI NIGHT THROUGH SAT NIGHT.
SEAS DOWNSTREAM OF TEHUANTEPEC WILL BUILD GREATER THAN 20 FT BY
FRI EVENING. A STORM WARNING WILL LIKELY BE ISSUED WITH THE NEXT
FORECAST PACKAGE.

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

SURFACE TROUGH EXTENDS FROM 08N82W TO 07N90W TO 07N102W. THE
ITCZ AXIS CONTINUES FROM 07N102W TO 08N120W TO 09N128W TO BEYOND
04N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS NOTED
WITHIN 90 NM N OF ITCZ W OF 138W. SCATTERED MODERATE ISOLATED
STRONG CONVECTION WAS NOTED WITHIN 240 NM OF THE ITCZ BETWEEN
125W AND 130W. 
 
...DISCUSSION...

A 1032 MB HIGH PRES LOCATED N OF AREA NEAR 35N134W EXTENDS A
RIDGE ACROSS THE N WATERS TO NEAR 20N110W. THE PRESSURE GRADIENT
BETWEEN THE HIGH AND LOWER PRESSURES IN THE VICINITY OF THE ITCZ
MAINTAINS A BROAD AREA OF 20-25 KT TRADE WINDS IN AN AREA
GENERALLY W OF 122W AND N OF THE ITCZ. LARGE NW SWELL CONTINUES
TO MOVE THROUGH THE FORECAST REGION AND IS MIXING WITH NE WIND
WINDS IN THIS TRADE WIND ZONE TO PRODUCE SEAS OF GENERALLY 10 TO
13 FT PER A RECENT 1630 UTC ALTIMETER PASS. THE LONG PERIOD NW
SWELL IS ALSO PRODUCING SEAS TO 8 TO 11 FT ACROSS THE REMAINDER
OF THE FORECAST WATERS N OF 05N AND W OF 110W. THIS AREA OF
FRESH TO STRONG WINDS WILL GRADUALLY SHRINK AND SHIFT SW OVER
THE NEXT FEW DAYS AS THE HIGH PRES MOVES SE AND GRADUALLY
WEAKENS. A COLD FRONT WILL IS FORECAST TO MOVE INTO THE AREA
EARLY FRI AND EXTEND FROM 30N132W TO 26N140W BY FRI EVENING
...AND FROM 30N126W TO 25N140W EARLY SAT. STRONG HIGH PRES IS
EXPECTED IN THE WAKE OF THE FRONT.  

THE PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE GREAT BASIN
AND A DEVELOPING SURFACE TROUGH ALONG THE COAST OF MEXICO HAS
RESULTED IN NW TO N WINDS OF 20 TO LOCALLY 25 KT IN THE GULF OF
CALIFORNIA PER 1654 AND 1748 UTC ASCAT PASSES. THESE WINDS WILL
INCREASE FURTHER TO 20 TO 25 KT THIS EVENING...AND CONTINUE
THROUGH FRI AS THESE WINDS SPREAD THE ENTIRE LENGTH OF THE GULF.
ASSOCIATED SEAS WILL BUILD TO 8-9 FT LATE THU.  
 
ANOTHER SET OF LONG PERIOD...20 TO 22 SECOND...NW SWELL IS
CURRENTLY MOVING INTO THE FORECAST AREA N OF 20N TO THE FAR NW
PORTION OF BAJA CALIFORNIA. THIS SWELL EVENT WILL SPREAD SE
COVERING THE WATERS N OF 20N W OF CENTRAL BAJA CALIFORNIA
TONIGHT...AND FROM CABO CORRIENTES TO NEAR 04N125W BY LATE
THU...REACHING FROM ACAPULCO MEXICO TO THE EQUATOR EARLY FRI.
THIS VERY LONG PERIOD SWELL MOVING THROUGH THE FORECAST WATERS
WILL GENERATE VERY LARGE AND POWERFUL SURF ACROSS THE
REEFS...SHOALS AND COASTAL ZONES OF MEXICO AND CENTRAL AMERICA
DURING THE NEXT 48 HOURS. MARINE INTERESTS FROM BAJA CALIFORNIA
AND NEARBY ISLANDS SOUTHWARD SHOULD REMAIN ALERT FOR THESE
HAZARDOUS MARINE CONDITIONS AND ONGOING DANGEROUS SURF
CONDITIONS.   
 
$$
COBB