000
AXPZ20 KNHC 282209
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT JAN 28 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2115 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 09N74W TO 01N79W TO 07N85W TO 
04N97W...WHERE IT TRANSITIONS TO ITCZ AXIS...CONTINUING ON TO  
05N107W TO 07N119W TO 04N132W TO BEYOND 04N140W. SCATTERED 
MODERATE WITHIN 150 NM S OF AXIS FROM 98W TO 106W.

...DISCUSSION...
THE UPPER LEVEL PATTERN ACROSS THE AREA HAS BECOME COMPLEX TODAY 
AS A PATTERN SHIFT IS UNDERWAY. A STAGNANT TROUGH-RIDGE-TROUGH 
PATTERN HAS PREVAILED THROUGHOUT THE PAST WEEK. HOWEVER...THE 
WEAK WESTERN-MOST TROUGH ALONG ABOUT 140W OF THE PAST MANY DAYS 
HAS OPENED UP AND IS BEING PULLED NW...WITH PORTIONS EXPECTED TO 
BECOME ENTRAINED INTO A SHARP AND ENERGETIC MIDDLE TO UPPER 
LEVEL LONG WAVE TROUGH APPROACHING 140W THIS AFTERNOON. THE 
DOWNSTREAM RIDGE...CENTERED ON AN ANTICYCLONE NEAR 32N126W... 
CONTINUES TO SHIFT E AS THE LONG WAVE TROUGH APPROACHES FROM THE 
W...AND BROAD TROUGHING ACROSS THE EASTERN TWO-THIRDS OF N 
AMERICA  EXTENDS A SINKING TROUGH SW ACROSS NEW MEXICO TO FAR NW 
MEXICO NEAR 29N111W...WHERE SATELLITE IMAGERY SUGGESTS A MIDDLE 
LEVEL CYCLONE. UPPER LEVEL RIDGING ACROSS THE TROPICS TO THE S 
OF THIS AREA THE PAST 48 HOURS HAS BECOME ELONGATED SE TO NW 
FROM NEAR 10N103W TO 26N129W. THE LONG WAVE TROUGH APPROACHING 
FROM THE W IS THE INSTIGATOR IN THIS UPCOMING PATTERN CHANGE... 
WITH N PORTIONS OF THE TROUGH EXPECTED TO MOVE E INTO N AMERICA 
BY SUN NIGHT AND ACT TO FLATTEN THE CURRENT RIDGE TO IT 
E...WHILE THE SOUTHERN PORTION OF THE LONG WAVE TROUGH LINGERS 
JUST W OF THE AREA AND EVOLVES INTO A CUT OFF LOW SOUTHEAST OF 
THE BIG ISLAND OF HAWAII. 

AT LOWER LEVELS...A SURFACE HIGH PRES RIDGE COVERS THE AREA N OF 
20N W OF 120W. A SHRINKING AREA TO FRESH TRADES HAS BEEN 
OBSERVED DURING THE PAST 36 HOURS...WITH RECENT SCATTEROMETER 
PASSES SUGGESTING NE TRADES AT 20 KT FROM 07N TO 12N W OF 
131W...WHILE N TO NE WINDS AT 20 KT ARE OBSERVED N OF 28N 
BETWEEN 123W AND 131W. COMBINED SEAS ACROSS THESE AREAS ARE 
RUNNING 8 TO 9 FT IN MIXED SWELL. OTHERWISE MODERATE TO LARGE 
NWLY SWELLS ARE ACROSS MUCH OF THE AREA N OF 23N W OF 114W.
AS THE LONG WAVE TROUGH SWEEPS ACROSS N PORTIONS OF THE AREA 
DURING THE NEXT 48 HOURS...THE CURRENT SURFACE RIDGE WILL WEAKEN 
AND REORGANIZE TO THE SW...SHIFTING THE AREA OF FRESH TRADES 
THAT IS TYPICALLY FOUND N OF THE ITCZ INTO THE CENTRAL PACIFIC 
AND JUST W OF THE LOCAL AREA.

THE PRES GRADIENT OVER SOUTHERN MEXICO HAS RELAXED AND WINDS 
HAVE DECREASED TO BELOW 20 KT THROUGH THE GULF OF TEHUANTEPEC 
LATE THIS AFTERNOON. HOWEVER ANOTHER REINFORCING COLD FRONT IS 
EXPECTED TO MOVE THROUGH THE GULF OF MEXICO TONIGHT AND SUNDAY 
WITH STRONG HIGH PRES BUILDING BEHIND THE FRONT. THIS WILL ONCE 
AGAIN TIGHTEN THE PRES GRADIENT ACROSS SOUTHERN MEXICO RESULTING 
IN GALE FORCE WINDS THROUGH THE GULF OF TEHUANTEPEC BEGINNING 
LATE TONIGHT THROUGH EARLY SUN.

ELY GAP WINDS TO 20 KT CONTINUE TO BLOW THROUGH THE GULF OF 
PAPAGAYO AND ARE EXPECTED TO PERSIST THROUGH THE WEEKEND.

$$
STRIPLING