000
AXPZ20 KNHC 210333
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED JAN 21 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0100 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG THE AXIS FROM 
03N77W TO 04N93W TO 07N117W TO 03N132W TO 05N140W. SCATTERED 
MODERATE CONVECTION CAN BE FOUND WITHIN 120 NM N OF THIS AXIS 
BETWEEN 102W AND 106W.

...DISCUSSION...

A MODERATE COLD FRONT OVER THE GULF OF MEXICO IS BRINGING STRONG 
NORTH-NORTHWESTERLY FLOW SOUTHWARD TO ISTHMUS OF TEHUANTEPEC.  
THE 1618 UTC ASCAT PASS SHOWED WINDS TO 30 KT IN THE GULF OF 
TEHUANTEPEC WHILE THE MORE RECENT 0002 UTC QUIKSCAT PASS SHOWED 
WINDS BUILDING TO JUST BELOW GALE FORCE.  WINDS ARE EXPECTED 
INCREASE TO GALE FORCE HERE OVERNIGHT...BUT THIS EVENT IS 
EXPECTED TO BE SHORT LIVED...ENDING ON THU MORNING.  THE 
INCREASED PRESSURE GRADIENT BETWEEN THE SOUTHWARD MOVING HIGH 
PRESSURE OVER EASTERN MEXICO AND THE WESTERN GULF BEHIND THE 
COLD FRONT AND LOW PRESSURE OVER NORTHERN COLOMBIA WILL EXPAND 
THE AREA WITH WINDS IN THE 20 TO 25 KT RANGE IN THE GULF OF 
PAPAGAYO AND DOWNSTREAM OVER THE NEXT FEW DAYS.  THE QUIKSCAT 
PASS AT 0002 UTC ONLY SHOWED WINDS IN THIS RANGE IN THE SMALL 
AREA FROM 10.5N TO 11.5N E OF 87W.

THE DEEP LAYERED RIDGE OVER THE ROCKIES AND SIERRA MADRE 
OCCIDENTAL IS EXPECTED TO BREAKDOWN BY THU...TURNING THE MID TO 
UPPER LEVEL PATTERN MORE ZONAL OVER THE NORTHEASTERN PORTION OF 
THE FORECAST AREA.  LOOK FOR THE NEGATIVELY TILTED TROUGH FROM 
30N125W TO 08N117W TO BECOME POSITIVELY TILTED OVER THE NEXT FEW 
DAYS...WITH THE PORTION OVER NORTHERN WATERS ADVANCING TOWARD 
THE MEXICAN COAST WHILE THE SOUTHERN PORTION STAYS STATIONARY... 
BLOCKED BY THE REMAINING RIDGING TO ITS EAST.  THE DISSIPATING 
COLD FRONT CURRENTLY FOUND FROM 30N128W TO 23N131W TO 17N140W 
WILL DEGENERATE TO A TROUGH BY MORNING AS IT EDGES EASTWARD.  TO 
THE SOUTH...THE AREA OF STRONG UPPER LEVEL DIFFLUENCE AND 
ASSOCIATED CONVECTION WILL REMAIN MAINLY IN THE REGION BETWEEN 
100W AND 120W FOR THE NEXT DAY OR TWO.  CURRENTLY...SCATTERED 
MODERATE CONVECTION LIES WITHIN 90 NM OF 09N108W IN ADDITION TO 
THE AFOREMENTIONED CONVECTION FOUND JUST NORTH OF THE ITCZ.

THE LONGWAVE TROUGH EXPECTED TO BRING WAVES IN EXCESS OF 20 FEET 
TO THE NORTH AND WEST FACING SHORES OF HAWAII WED WILL MOVE INTO 
NW WATERS EARLY THU.  NW SWELL ASSOCIATED WITH THIS SYSTEM WILL 
FIRST MOVE INTO NW WATERS OVERNIGHT WED NIGHT WITH PERIODS IN 
THE 16 TO 18 SECOND RANGE.  SEAS OVER FORECAST WATERS ARE 
EXPECTED TO BUILD TO 16 FT BEHIND THE FRONT BY THU AFTERNOON.  
ALOFT...THIS TROUGH IS EXPECTED TO CUT OFF FROM THE NORTHERN 
STREAM ON THU NIGHT...LEAVING A DEEP LAYERED LOW OVER NW WATERS 
ON FRI.

$$
SCHAUER CLARK