000
AXPZ20 KNHC 221609
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU JAN 22 2009

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...ITCZ...
AXIS ALONG 04N77W TO 04N88W TO 03N91W TO 07N107W TO 06N127W TO 
04N140W. SCATTERED MODERATE WITH ISOLATED DEEP CONVECTION WAS 
OCCURRING WITHIN 120 NM N OF AXIS BETWEEN 118W AND 100W. 
SCATTERED MODERATE WITH ISOLATED DEEP CONVECTION WAS ALSO 
OCCURRING FROM 09.5N TO 15N BETWEEN 114W AND 108W ALONG AND EAST 
OF A WESTWARD DRIFTING SURFACE TROUGH.

...DISCUSSION...
A MID/UPPER LEVEL TROUGH IS ENTERING THE FAR NW PORTION OF THE 
DISCUSSION AREA THIS MORNING...JUST NW OF A BROAD UPPER LEVEL 
RIDGE. THE RIDGE AXIS EXTENDS FROM AN EQUATORIAL HIGH IN THE 
CENTRAL PACIFIC THROUGH 15N140W TO BEYOND 32N128W. THE TROUGH 
ALSO SUPPORTS A COLD FRONT MOVING ESE ACROSS NW PORTIONS OF THE 
AREA. EXCEPT FOR THIS FRONTAL SYSTEM...ANTICYCLONIC FLOW COVERS 
THE AREA W OF 120W. MODERATE TO STRONG SUBSIDENCE AND STABLE 
CONDITIONS PREVAIL FROM THE RIDGE AXIS E TO 120W. A SLOW MOVING 
MID TO UPPER LEVEL TROUGH WAS E OF THE RIDGE...EXTENDING FROM 
CENTRAL CALIFORNIA SSE TO THE NRN BAJA CALIFORNIA COAST...AND 
WAS BECOMING LINKED WITH A LINGERING DEEP LAYERED TROUGH THAT 
EXTENDED FROM 06N110W NWD INTO CENTRAL BAJA. AMPLE LOW TO MID 
LEVEL MOISTURE HAS REMAINED TRAPPED TO THE E OF THIS LINGERING 
TROUGH FOR DAYS...WITH A SURFACE TROUGH HAVING DEVELOPED IN THE 
PAST 24 HOURS BETWEEN 110W AND 112W...AND IS NOW CROSSING 115W.  
SYNOPTIC LIFT PROVIDED BY THE DEEP LAYERED TROUGH AND 
ANTICYCLONIC SHEAR TO ITS E ARE MAINTAINING ACTIVE CONVECTION 
IDENTIFIED ABOVE AND S OF 20N. THE SURFACE TROUGH WILL CONTINUE 
TO MOVE W OVER THE NEXT 24 HOURS WITH ACTIVE CONVECTION EXPECTED 
ALONG AND TO THE E...AND S OF 14N. FARTHER N...BROKEN MID TO 
UPPER LEVEL CLOUDS ARE LIKELY BRINGING SOME STRATIFORM PRECIP TO 
THE BAJA AND PORTIONS OF NW MEXICO...WITH SOME ISOLATED EMBEDDED 
CONVECTION POSSIBLE. 

A 1010 MB SURFACE LOW WAS CENTERED NEAR 29N122W AND WAS 
CONNECTED VIA AN OCCLUDED FRONT TO A COLD FRONT EXTENDING FROM 
31N118W SSW TO 15N123W. 20 KT WINDS WERE EXPECTED ACROSS THE WRN 
SEMICIRCLE OF THE LOW...WHILE THE FRONT WAS ALSO AIDING IN 
PROVIDING LOW LEVEL MOISTURE CONVERGENCE AND NWD ADVECTION E OF 
115W. SEVERAL PULSES OF NWLY SWELL GENERATED ACROSS THE N 
PACIFIC WILL CONTINUE TO PROPAGATE THROUGH THE AREA OVER THE 
NEXT FEW DAYS...WITH THE LEADING EDGE OF THE MOST RECENT PULSE 
HAVING MOVED THROUGH THE AREA IN THE PAST 24 HOURS...AND THE 
NEXT PULSE OCCURRING WITH AND BEHIND THE COLD FRONT NOW ENTERING 
NW PORTIONS OF THE AREA. SEAS WERE RUNNING 8 TO 10 FT IN NW 
SWELL FROM 110W TO THE NW MOST COLD FRONT...WITH SEAS BEHIND 
THAT FRONT EXPECTED TO BUILD 12 TO 18 FT IN LARGE NW SWELL 
DURING THE NEXT 24 HOURS.    

ELSEWHERE...A SUFFICIENT PRES GRADIENT PERSISTS OVER SOUTHERN 
MEXICO AND WAS MAINTAINING GALE FORCE WINDS THROUGH THE GULF OF 
TEHUANTEPEC EARLY THIS MORNING...BUT IS FORECAST TO DROP BELOW 
GALE FORCE LATER THIS MORNING...AND BELOW 20 KT BY 48 HOURS.  
SEAS WELL DOWNSTREAM OF THIS GAP WERE 10 TO 12 FT. GAP WINDS 
WERE ALSO BLOWING 20 KT...WITH ISOLATED SPOTS 20-25 KT...ACROSS 
AND DOWNWIND OF THE GULF OF PAPAGAYO AND FONSECA. THESE GAP 
WINDS WILL LIKELY PERSIST AT OR ABOVE 20 KT THROUGH 48 HOURS. 

$$