000
AXPZ20 KNHC 202146
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE JAN 20 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG THE AXIS FROM 
03N78W TO 04N95W TO 07N115W TO 03N130W TO 05N140W. SCATTERED 
MODERATE CONVECTION CAN BE FOUND WITHIN 150 NM N OF THIS AXIS 
FROM 101W TO 112W. 

...DISCUSSION...
A NEGATIVELY TILTED DEEP LAYER TROUGH EXTENDS FROM 30N123W TO 
10N117W WITH VERY DRY AIR MASS W OF AXIS.  A STATIONARY DEEP 
LAYERED RIDGE TO ITS EAST OVER MEXICO AND THE DESERT SW U.S. 
WILL BLOCK ANY FURTHER EASTWARD ADVANCEMENT OF THIS TROUGH.  THE 
RIDGE COVERS REMAINDER OF BASIN E OF THE TROUGH AXIS.  UPPER 
LEVEL DIFFLUENCE ON THE SE EDGE OF THE TROUGH/SW SIDE OF THE 
RIDGE IS SUPPORTING SCATTERED MODERATE CONVECTION WITHIN 45 NM 
OF 11N108N AND SCATTERED MODERATE CONVECTION WITHIN 150 NM N OF 
THE ITCZ AXIS FROM 101W TO 112W WHERE LOW LEVEL MOISTURE HAS 
CONVERGED. 

SURFACE TROUGH FROM 17N129W TO 29N125W WILL BE OVERTAKEN BY THE 
COLD FRONT CURRENTLY LYING FROM 30N128W TO 28N1290W WITH A 
DISSIPATING PORTION TO 22N133W AND TO 18N140W. NW SWELL 
ASSOCIATED WITH THIS COLD FRONT WILL OVERTAKE THE AREA OF HIGH 
SEAS GENERATED BY THE TROUGH TONIGHT...AND THIS COLD FRONT WILL 
SLOWLY DISSIPATE TO A TROUGH OVER FORECAST WATERS OVER THE NEXT 
24 WATERS.  A SECOND COLD FRONT WILL ENTER NW WATERS LATE WED 
NIGHT...REINFORCING THE NW SWELL.

SURGE OF HIGH PRES OVER EASTERN MEXICO BEHIND A HEALTHY COLD 
FRONT BRINGS N WINDS/COLD AIR ACROSS ISTHMUS OF TEHUANTEPEC AND 
SHORT LIVED GALE FORCE WINDS ARE EXPECTED TONIGHT...BUT SHOULD 
DIMINISH BELOW GALE FORCE ON THU MORNING.  GULF OF PAPAGAYO NE 
WINDS 20 TO 25 KT EXPECTED TO CONTINUE UNABATED THROUGH FORECAST 
PERIOD.      

$$
SCHAUER CLARK/WALLY BARNES