000
AXPZ20 KNHC 291531
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT JAN 29 2011

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ALONG 02N78W TO 
04N100W TO 07N110W TO 04N140W. NO SIGNIFICANT CONVECTION.

...DISCUSSION...

ALOFT...A MID/UPPER CUT-OFF UPPER LEVEL LOW IS NEAR 12N138W 
MOVING NEWD. A DEEP LAYER TROUGH EXTENDS FROM THIS LOW TO THE N 
OVER THE NW PORTION OF THE FORECAST AREA. MID/UPPER LEVEL 
RIDGING IS PRESENT TO THE E OF THIS TROUGH TO ABOUT 120W. 
ANOTHER UPPER LEVEL LOW IS OVER THE SW CONUS WITH A TROUGH 
EXTENDING SW TO NEAR 27N115W. A JET STREAM BRANCH WITH CORE JET 
SPEEDS OF 70-90 KT ROUNDS THE BASE OF THIS TROUGHS. WINDS 
INCREASE TO 90-110 KT OVER NORTHERN MEXICO. A RIDGE DOMINATES 
THE EASTERN PORTION OF THE FORECAST REGION. MODERATE UPPER LEVEL 
SUBSIDENCE IS NOTED E OF 100W. 

AT THE SURFACE...A 1026 MB SURFACE HIGH IS ANALYZED NW OF THE 
AREA AT 31N141W WITH A RIDGE EXTENDING SE OVER THE N WATERS TO 
NEAR 20N110W. THE HIGH IS FORECAST TO MOVE EWD OVER THE NEXT 24 
HOURS. NE TO E TRADES OF 20 TO 25 KT ARE NOTED ON THE SOUTHERN 
PERIPHERY OF THE RIDGE COVERING ROUGHLY THE AREA FROM 14N TO 20N 
W OF 125W. AS THE HIGH BEGINS TO SHIFT EWD...THE GRADIENT WILL 
THEN RELAX SOME...AND THE TRADE WINDS WILL BE BELOW 20 KT IN 
ABOUT 48 HOURS. 

REGIONAL SEAS ARE BEING DOMINATED BY NW SWELL RAISING SEAS UP TO 
9 FT OVER THE NW PORTION OF THE AREA. ANOTHER BATCH OF NW SWELL 
WILL REACH THE FAR NW CORNER LATER TODAY. THESE SWELLS WILL 
PROPAGATE SE BUILDING SEA HEIGHTS UP TO 12 FT N OF 26N BETWEEN 
120W AND 130W BY MON.    

GAP WINDS...
THE 1226 UTC EXPERIMENTAL ASCAT 25 KM COASTAL WINDS SHOWED NLY 
WINDS OF 20 TO 25 KT THROUGH THE GULF OF TEHUANTEPEC. RECENT 
SURFACE OBSERVATIONS FROM IXTEPEC MEXICO SHOW SUSTAINED WINDS OF 
20 TO 25 KT WITH HIGHER GUSTS. SO DECIDED TO INCREASE WINDS TO 
25 KT THROUGH THE GULF OF TEHUANTEPEC FOR THIS FORECAST PACKAGE. 
BOTH THE GFS AND NAM REGIONAL MODEL SUGGEST WINDS BELOW 20 KT IN 
ABOUT 12 HOURS...AND THE FORECAST SHOWS THIS TREND. SEAS ARE 
ALSO EXPECTED TO SUBSIDE TO LESS THAN 8 FT BY THIS EVENING. 
HOWEVER...AN AREA OF SIGNIFICANT WAVE HEIGHTS AS HIGH AS 8 FT IN 
MIXED NE WIND WAVES AND SW SWELL WILL PERSIST FROM 09N TO 12N 
BETWEEN 96W AND 106W THROUGH EARLY SUN MORNING.

NE WINDS OF 20 TO 25 KT...AND SEAS IN THE 8 TO 10 FT RANGE ARE 
NOTED THROUGH THE GULF PAPAGAYO PER A FEW SHIP OBSERVATIONS. 
THESE WINDS ARE EXPECTED TO PERSIST WHILE EXPANDING W TO NEAR 
91W IN 24 HOURS...THEN DECREASE TO 20 KT AND RETREAT TO 88W IN 
48 HOURS.

$$
GR