000
AXPZ20 KNHC 311552
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU JAN 31 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 03N78W TO 05N92W. THE ITCZ CONTINUES 
FROM 05N92W TO 07N118W TO 05N140W. SCATTERED MODERATE CONVECTION 
IS NOTED WITHIN 180 NM N OF ITCZ BETWEEN 116W AND 121W.

...DISCUSSION...
A 1033 MB HIGH PRESSURE CENTERED N OF THE AREA NEAR 40N132W 
EXTENDS A RIDGE OVER THE FORECAST WATERS TO NEAR 16N110W. THE 
PRESSURE GRADIENT BETWEEN THIS AREA OF HIGH PRESSURE AND LOWER 
PRESSURE IN THE VICINITY OF THE ITCZ IS MAINTAINING FRESH TO 
STRONG TRADES OVER MUCH OF THE W CENTRAL PORTION OF THE FORECAST 
AREA 05N TO 22N W OF 130W AND FROM 08N TO 15N BETWEEN 115W AND 
130W. THESE WINDS ARE RAISING SEAS UP TO 12 FT. THE HIGH 
PRESSURE AND ATTENDANT RIDGE IS FORECAST TO WEAKEN DURING THE 
NEXT 24-48 HOURS WHILE SHIFTING FURTHER N OF THE AREA. AS A 
RESULT...THE AREAL COVERAGE OF THE TRADE WINDS WILL DECREASE 
SIGNIFICANTLY...WITH WINDS DIMINISHING TO 20 KT OR LESS BY FRI 
EVENING.

THE PRESSURE GRADIENT BETWEEN THE RIDGE AND TROUGHING OVER 
WESTERN MEXICO IS RESULTING IN FRESH TO STRONG WINDS IN THE GULF 
OF CALIFORNIA S OF 30N. SEAS OF 8 FT ARE SPILLING OUT OF THE 
MOUTH OF THE GULF TO AROUND 20N BETWEEN 105W AND 110W. WINDS 
AREA FORECAST TO BE 20 KT OR LESS IN ABOUT 24 HOURS AS THE HIGH 
PRES WEAKENS. 

A COLD FRONT WILL REACH 30N140W FRI EVENING. NLY WINDS OF 20-25 
KT AND A NEW SWELL EVENT WILL FOLLOW THE FRONT...FORECAST TO 
REACH A POSITION FROM 30N135W TO 25N140W BY SAT MORNING. THE 
FRONT WILL DISSIPATE OVER THE FORECAST WATERS LATER ON SAT. THE 
LONG PERIOD NW SWELL WITH SIGNIFICANT WAVE HEIGHTS AS HIGH AS 16 
FT WILL AFFECT THE NW WATERS BY SAT MORNING SPREADING SE OVER 
THE REMAINDER OF THE WEEKEND. 

SOME OF THE GLOBAL MODELS SUGGEST THE DEVELOPMENT OF A LOW PRES 
SYSTEM NEAR 20N-21N AND 130W-132W BY SUN. IF THIS SYSTEM 
MATERIALIZES...IT COULD BRING A SIGNIFICANT INCREASE IN WINDS 
AND SEAS ACROSS THE N WATERS. WILL SEE FUTURE MODEL GUIDANCE FOR 
UPDATED FORECAST INFORMATION.    

GAP WINDS...
GULF OF TEHUANTEPEC...A STRONG COLD FRONT HAS REACHED THE SE 
GULF OF MEXICO AND THE YUCATAN PENINSULA AT 1200 UTC. THE DENSER 
AIR MASS BEHIND THIS FRONT HAS STARTED TO FUNNEL THROUGH THE 
CHIVELA PASS INTO THE GULF OF TEHUANTEPEC. THE SURGE IS 
ACCOMPANIED BY A TYPICAL SIGNATURE ARC CLOUD THAT IS EVIDENT IN 
VISIBLE SATELLITE IMAGERY THIS MORNING. THIS CLOUD IS ALREADY 
REACHING AS FAR SOUTH AS 11N. A GALE WARNING REMAINS IN EFFECT 
FOR THE GULF OF TEHUANTEPEC. THE GALE EVENT WAS CONFIRMED BY 
THE LATEST 0549 UTC OSCAT PASS DEPICTING 40 KT WINDS. IN 
ADDITION...SALINA CRUZ IN THE STATE OF OAXACA IS REPORTING 
SUSTAINED WINDS OF 35 KT. STRONG HIGH PRESSURE BUILDING BEHIND 
THE FRONT OVER EASTERN MEXICO AND THE WESTERN GULF OF MEXICO 
WILL HELP TO MAINTAIN GALE FORCE CONDITIONS IN THE GULF OF 
TEHUANTEPEC THROUGH EARLY SAT. 

GULF OF PAPAGAYO...FRESH TO STRONG WINDS OVER THE GULF OF 
PAPAGAYO WILL FURTHER INCREASE TO 30 KT BY EARLY FRI MORNING. 
THIS WILL BUILD SEAS TO 10 FT JUST DOWNWIND OF THE GULF.

GULF OF PANAMA...FRESH TO STRONG WINDS WILL SPREAD ACROSS THE 
ISTHMUS OF PANAMA FROM THE SW CARIBBEAN SEA TO THE GULF OF 
PANAMA BY LATE TONIGHT THROUGH FRI. THIS WILL RESULT IN SEAS 
BUILDING TO 8-9 FT DOWNWIND OF THE GULF.

$$
GR