000
AXPZ20 KNHC 030333
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT JAN 03 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 
0030 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...06N77W TO 
03N80W TO 05N87W TO 11N117W TO 10N127W TO 07N140W. ISOLATED 
MODERATE CONVECTION WAS ALONG THE COLUMBIAN COAST FROM 04N TO 
06N. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION WAS 
OCCURRING FROM 08N TO 15N BETWEEN 126W AND 112W. SCATTERED 
MODERATE CONVECTION WAS OCCURRING WITHIN 30 NM OF AXIS BETWEEN 
132W AND 127W. 

...DISCUSSION...

MID TO UPPER LEVEL TROUGH/SHEAR AXIS EXTENDS FROM A CYCLONIC 
CIRCULATION OVER EXTREME N MEXICO NEAR 29N106W...WEST 
SOUTHWESTWARD TO A BROAD CYCLONIC CIRCULATION NEAR 22N133W. 
MODERATE TO STRONG SUBSIDENCE WAS NOTED WITHIN 120-240 NM N OF 
THE TROUGH AXIS...AND 60 NM S OF THE TROUGH. A SHARPENING 
MID/UPPER LEVEL TROUGH WAS DIGGING SE INTO THE NW COAST OF THE 
U.S. AND IS FCST TO DIG FURTHER SSE INTO N PORTIONS OF THE AREA 
BEYOND 36 HOUR...AND DRIVE A COLD FRONT INTO THE REGION LATE SAT 
WITH FRESHENING NW TO N WINDS AROUND 20 KT BUILDING BEHIND THE 
FRONT SAT NIGHT AND SUN. AT THE SURFACE...1029 MB HIGH PRES NW 
OF THE AREA NEAR 32N147W WITH ASSOCIATED SFC RIDGE EXTENDING SE 
THROUGH 27N130W TO 20N110W. THE MODERATE PRES GRADIENT S OF THE 
RIDGE IS MAINTAINING AN AREA OF MODERATE TO FRESH TRADES FROM 
12N TO 22N...W OF 125W. TRADES MAY INCREASE SLIGHTLY TO NEAR 30 
KT W OF 135W BY SUN AS THE PRES GRADIENT TIGHTENS.     

AN UPPER LEVEL RIDGE REMAINS NEARLY STATIONARY ACROSS THE 
TROPICAL EPAC ALONG 116W TONIGHT...AND IS AIDING IN THE 
SHARPENING OF AN UPSTREAM SHORT WAVE TROUGH MOVING THROUGH THE 
BASE OF THE UPPER LOW/TROUGH NEAR 22N133W. UPPER LEVEL 
ANTICYCLONIC FLOW AND A BROAD DIFFLUENT ZONE WAS AIDING IN 
MAINTAINING DEEP CONVECTION IN THE VICINITY OF TWO LOW LEVEL 
EASTERLY WAVES...ONE JUST INCHING ALONG NEAR 127W...AND THE 
OTHER ALONG 119W. THE UPPER LEVEL TROUGH DIGGING INTO THE W 
COAST OF THE U.S. TONIGHT IS FORECAST TO REACH NORTHERN BAJA BY 
48 HOURS...AND WILL ACT TO REINFORCE THIS MID TO UPPER LEVEL 
TROUGHING EXTENDING INTO THE TROPICS BETWEEN 135W AND 130W. 
INDUCED LOW LEVEL TROUGHING BY THESE TWO EASTERLY WAVES...AMPLE 
MOISTURE...AND A PERSISTENT MID LEVEL TROUGH THERE WILL MAINTAIN 
ACTIVE CONVECTION ACROSS THIS REGION E OF 130W THROUGH 36 
HOURS...AND AS INDICATED ABOVE...MAINTAIN A TIGHT PRESSURE LOW 
LEVEL PRESSURE GRADIENT TO THE N AND NW. 

GAP WINDS...
GAP WINDS IN THE GULF OF TEHUANTEPEC HAVE FALLEN BELOW 20 KT. 
ELSEWHERE ACROSS THE REGION...N TO NE GAP WINDS OF 20 TO 25 KT 
ARE EXPECTED TO CONTINUE ACROSS AND DOWNWIND OF THE GULF OF 
PAPAGAYO THROUGH THE NEXT 48 HOURS...AND GULF OF PANAMA FOR THE 
NEXT 24 HOURS...BEFORE SUBSIDING. 

$$
STRIPLING