000
AXPZ20 KNHC 171541
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU DEC 17 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1500 UTC.               
 
...SPECIAL FEATURE...

A STORM WARNING REMAINS IN EFFECT FOR THE GULF OF TEHUANTEPEC. A
COLD FRONT CURRENTLY MOVING ACROSS THE GULF OF MEXICO IS
EXPECTED TO REACH THE CENTRAL BAY OF CAMPECHE EARLY THIS
EVENING...AND ALLOW NORTHERLY WINDS BEHIND THE FRONT TO BEGIN TO
SPILL THROUGH THE ISTHMUS OF TEHUANTEPEC AND ACROSS THE GULF OF
TEHUANTEPEC. WINDS ACROSS THESE PACIFIC WATERS ARE FORECAST TO
REACH GALE FORCE LATE TONIGHT INTO EARLY MORNING FRI...AND
CONTINUE TO GRADUALLY INCREASE AND EXPAND IN AREAL EXTENT ON
FRI. A 1031 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. WINDS ACROSS TEHUANTEPEC ARE EXPECTED TO
REACH STORM FORCE...50-55 KT...BY EARLY FRI EVENING AND LIKELY
CONTINUE TO EARLY SAT MORNING WITH THE ASSISTANCE OF THE
NOCTURNAL DRAINAGE FLOW. THEN...GALE FORCE WINDS ARE FORECAST TO
PERSIST THROUGH SUN. SEAS DOWNSTREAM OF THE GULF OF TEHUANTEPEC
WILL BUILD TO 21-22 FT BY FRI EVENING. GLOBAL MODELS ALSO
SUGGEST THAT THE WIDTH OF THE GALE FORCE WINDS WILL BE UNUSUALLY
BROAD FRI EVENING THROUGH EARLY SAT...AND MAY EXTEND EASTWARD
ACROSS THE TEHUANTEPEC AREA TO NEAR 93.5W ACROSS THE OFFSHORE
WATERS...AND TO PUERTO ARISTA ALONG THE COAST OF MEXICO. 
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...            

A SURFACE TROUGH EXTENDS FROM 06N85W TO 05N93W TO 08N101W TO
07N105W. THE ITCZ AXIS EXTENDS FROM 07N105W TO 04N115W TO
05N126W TO BEYOND 06N140W. SCATTERED MODERATE CONVECTION IS
NOTED WITHIN 90 NM S OF AXIS BETWEEN 116W AND 120W. SIMILAR
CONVECTION IS FROM 08N TO 10N BETWEEN 118W AND 122W. 
 
...DISCUSSION...

A 1028 MB HIGH PRES LOCATED N OF AREA NEAR 33N131W IS SHIFTING
SLOWLY SOUTHEASTWARD AND EXTENDS A RIDGE ACROSS THE N WATERS TO
NEAR 20N111W. 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 120W AND N OF THE
ITCZ TO 27N. LARGE NW SWELL CONTINUES TO MOVE THROUGH THE
FORECAST REGION AND IS MIXING WITH NE WIND WAVES IN THIS TRADE
WIND ZONE TO PRODUCE SEAS OF GENERALLY 10 TO 13 FT PER RECENT
ALTIMETER DATA. THE LONG PERIOD NW SWELL IS ALSO PRODUCING SEAS
TO 8 TO 11 FT ACROSS THE MOST OF THE FORECAST WATERS W OF 110W.
THIS AREA OF FRESH TO STRONG TRADE WINDS WILL GRADUALLY SHRINK
AND SHIFT SW OVER THE NEXT FEW DAYS AS THE HIGH PRES MOVES SE
AND GRADUALLY WEAKENS. A COLD FRONT IS FORECAST TO REACH 30N140W
EARLY FRI MORNING AND EXTEND FROM FROM 30N132W TO 27N140W BY FRI
EVENING...AND FROM FROM 30N126W TO 25N140W EARLY SAT. BUILDING
HIGH PRES IS EXPECTED IN THE WAKE OF THE FRONT...WITH ANOTHER
MODEST PULSE OF NW SWELL BEGINNING TO MOVE THROUGH THE AREA.
FRESH TO STRONG NORTHERLY WINDS AND BUILDING SEAS TO 12-13 FT
WILL FOLLOW THE FRONT BY SAT MORNING. 

THE PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE GREAT BASIN
AND A DEVELOPING SURFACE TROUGH ALONG THE COAST OF MEXICO HAS
RESULTED IN NW WINDS OF 20 TO 25 KT SPREADING THROUGH THE FULL
LENGTH OF THE GULF OF CALIFORNIA PER RECENT RAPIDSCAT DATA...
WITH NE WINDS 15-20 KT BLOWING ACROSS THE BAJA PENINSULA AND
ACCELERATING THROUGH THE LARGER GAPS TO PRODUCE AREAS OF 20 KT
NE WINDS WITH HIGHER GUSTS ACROSS THE PACIFIC COASTAL WATERS S
OF PUNTA EUGENIA. SEAS INSIDE THE GULF ARE EXPECTED TO BUILD TO
7-9 FT WITH THESE WIND SPEEDS. WINDS AND SEAS WILL BEGIN TO
DIMINISH FRI AFTERNOON AND FALL BELOW 20 KT AND SEAS LESS THAN 8
FT LATE FRI. 
  
LONG PERIOD NW SWELL AT 20 TO 22 SECONDS CONTINUES TO SPREAD SE
ACROSS THE FORECAST WATERS MAINLY N OF 20N AND JUST OFF THE BAJA
CALIFORNIA PENINSULA. THIS SWELL EVENT WILL COVER THE WATERS
FROM CABO CORRIENTES TO NEAR 04N125W BY THIS EVENING...AND REACH
FROM NEAR 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.   
 
$$
STRIPLING