000
AXPZ20 KNHC 200343
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 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 
2045 UTC.

...ITCZ...
AXIS ALONG...04N77W TO 05N86W TO 03N95W TO 06N115W TO 04N127W TO 
06N140W. ISOLATED MODERATE CONVECTION WAS OCCURRING WITHIN 60 NM 
OF AXIS BETWEEN 85W AND 103W AND ALSO BETWEEN 106W AND 113W. 
SCATTERED MODERATE CONVECTION WAS OCCURRING WITHIN 90 NM OF AXIS 
BETWEEN 116W AND 123W. SCATTERED TO NUMEROUS MODERATE CONVECTION 
WITH ISOLATED DEEP CONVECTION WAS OCCURRING FROM 07N TO 15N 
BETWEEN 108W AND 118W. ISOLATED MODERATE CONVECTION WAS 
OCCURRING FROM 15N TO 24N BETWEEN 108W AND 114W. CONVECTION 
CONTINUED TO WEAKEN WITHIN 180 NM OF NE AND E SEMICIRCLE OF 1013 
MB LOW.

...DISCUSSION...
MID TO UPPER LEVEL LARGE AMPLITUDE TROUGH FROM 32N123W TO WEAK 
CYCLONIC VORTEX AT 21N121W TO 11N118W TO 05N118W...WITH 
ANTICYCLONIC FLOW DIVING INTO THE BACK SIDE OF TROUGH AND 
HELPING TO MAINTAIN DRY AND STABLE MID LEVEL CONDITIONS W OF 
AXIS. SLIGHT NEGATIVE TILT OF TROUGH AND ANTICYCLONIC SHEAR EAST 
OF TROUGH CONTINUES TO PRODUCE DIFFLUENT FLOW ALOFT S OF 17N AND 
E TO 108W. SLY LOW TO MID LEVEL FLOW AND ASSOCIATED CONVERGENCE 
E OF THIS TROUGH CONTINUE TO PRODUCE A ZONE OF ABUNDANT TROPICAL 
MOISTURE ADVECTING NWD TOWARD AND INTO EXTREME SRN BAJA 
CALIFORNIA AND COASTAL SECTIONS OF W CENTRAL MEXICO. NUMEROUS 
CONVECTION ACROSS THIS AREA HAS REMAINED LIMITED N OF 16N DURING 
THE PAST SEVERAL HOURS...WITH CONVECTIVE DEBRIS AND POSSIBLE 
LIGHT STRATIFORM PRECIP AFFECTING SRN BAJA. HOWEVER...CONVECTION 
HAS BECOME RENEWED IN THE PAST 6 HOURS E OF THE TROUGH AND S OF 
16N AS INCREASED LOW LEVEL CONVERGENCE HAS DEVELOPED. THE MID TO 
UPPER TROUGH WILL BEGIN TO BE NUDGED VERY SLOWLY EWD NEXT 12-24 
HORS AS A SHORT WAVE AND FRONTAL SYSTEM TO THE NW APPROACH THE 
AREA...AND THE UPSTREAM RIDGE BEGINS TO WEAKEN AND SHIFT SE. 
AFTER 48 HOURS THIS HIGH AMPLITUDE TROUGH WILL DRIFT EAST TO 
114W AS THE SHORT WAVE MOVES INTO W COAST OF U.S. 

A 1013 MB SURFACE LOW THAT SPAWNED A FEW DAYS AGO AS A COLD CORE 
REFLECTION OF THIS MID TO UPPER LEVEL TROUGH HAS REMAINED NEAR 
19N129W TONIGHT...BUT HAS BEGUN TO DRIFT NW DURING THE PAST 12 
HOURS OF SO. AS INDICATED ABOVE...CONVECTION IS WEAKENING...AND 
THE LOW IS EXPECTED TO GRADUALLY FILL..BECOME ELONGATED...AND 
MERGE WITH THE FRONTAL SYSTEM TO THE NW BY 48 HOURS. NE TO N 
WINDS OF 20 KT PERSIST THIS EVENING IN THE NW SEMICIRCLE OF THE 
LOW AND WITHIN A FEW DEGREES OF THE CENTER.   

THE COLD FRONT WAS RELOCATED TONIGHT FROM 30N133W TO 20N140W AND 
WILL MERGE WITH SURFACE TROUGH ALONG 127W AT 36 TO 48 HOURS AS 
THE FRONT PROGRESSES FORWARD AND WEAKENS. NW SWELL GENERATED 
BEHIND THIS FRONT HAS PROPAGATED THROUGH THE ENTIRE AREA DURING 
THE PAST 36 HOURS...AND AFFECTED MOST OF THE AREA W OF 110W WITH 
SEAS IN EXCESS OF 8 FT.  HIGHEST SEAS ACROSS THE AREA TONIGHT 
ARE SUGGESTED BY MODEL GUIDANCE...AND A LONE SHIP REPORT... 
SEVERAL DEGREES BEHIND THE FRONT...RUNNING AT 17 TO 18 FT IN NW 
SWELL. A 1021 MB HIGH OFF OF THE SOUTHERN CALIFORNIA COAST HAS 
RIDGE EXTENDING TO 16N112W...HELPING TO PRODUCE 20 KT NW TO N 
WINDS FROM SRN GULF OF CALIFORNIA TO 18N.

GULF OF TEHUANTEPEC WINDS REMAIN AROUND 20 KT AND WILL WEAKEN 
SLIGHTLY WITHIN 24 HRS ONLY TO RECOVER BY 48 HRS AND REACH GALE 
FORCE BEYOND FORECAST PERIOD.  GULF OF PAPAGAYO WIND IS EXPECTED 
TO HOLD WITH LITTLE CHANGE THROUGH 36 HRS THEN INCREASE 20 TO 25 
KT BY 48 HRS AS THE WIND FIELD EXPANDS.

$$
STRIPLING