000
AXPZ20 KNHC 220952
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE DEC 21 2010

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 
0945 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 02N78W 
THROUGH AN EMBEDDED WEAKENING LOW PRES AT 07N93W...THEN THE AXIS 
DIPS SW TO NEAR 05N107W...THEN TURNS NW TO 10N125W...THEN SW TO 
NEAR 08N140W. AN EMBEDDED TROUGH IS ORIENTATED N TO S FROM 
08N125W TO 15N122W. THIS TROUGH IS EXPECTED TO DRIFT W AND 
GRADUALLY LOSE IDENTITY OVER THE NEXT 24 HOURS. CURRENTLY THERE 
IS NO SIGNIFICANT CONVECTION ALONG THE ITCZ.

...DISCUSSION...

A LONG WAVE TROUGH DOMINATES THE E PACIFIC WITH ITS MEAN AXIS N 
OF 22N ALONG 130W. A SHORT WAVE TROUGH IS ROTATING THROUGH 
PATTERN WITH THE ASSOCIATED SURFACE COLD FRONT EXTENDING FROM 
32N123W TO 26N140W. A FRONTAL TROUGH IS WEAKENING FROM 32N117W 
T0 21N140W. THE COLD FRONT IS EXPECTED TO OVERTAKE THE FRONTAL 
TROUGH TODAY WITH THE MERGED FRONT MOVING ACROSS THE NORTHERN 
BAJA CALIFORNIA PENINSULA TONIGHT. SURFACE WINDS HAVE INCREASED 
AGAIN TO 20 KT AHEAD OF THE FRONTAL TROUGH AND INCREASE TO 
WESTERLY AT 20 TO 25 KT W OF THE TROUGH THEN SHIFTING TO NW TO 
THE W OF THE FRONT. SEAS W OF THE FRONT HAVE BUILT TO 16 FT IN 
THE LONG PERIOD NW SWELL...BUT ARE EXPECTED TO SUBSIDE TO ABOUT 
10 FT BEFORE REACHING THE NORTHERN BAJA CALIFORNIA PENINSULA. 
THE FRONT WILL MOVE THROUGH THE NORTHERN GULF OF CALIFORNIA 
EARLY THU. SOUTHERLY SURFACE WINDS ARE EXPECTED TO INCREASE TO 
20 TO 25 KT LATER TODAY AHEAD THE FRONT OVER THE GULF WATERS N 
OF 29N...DIMINISHING TO LESS THAN 20 KT THU MORNING.  

AN UPPER ANTICYCLONE IS ESTIMATED NEAR 14N104W WITH AN UPPER 
RIDGE EXTENDING NNE THROUGH 32N98W AND ACROSS THE ENTIRE CENTRAL 
CONUS. DRY UPPER AIR ASSOCIATED WITH THE SHORT WAVE HAS HELP 
ERODE THE PERSISTENT TROPICAL MOISTURE PLUME TO ONLY 300 NM 
WIDE... WITH ITS AXIS ALONG 17N140W TO 20N127W TO BEYOND 
32N113W.  

UPPER MOISTURE FROM FORMER CONVECTION IS NOTED OVER THE AREA 
WITHIN 180 NM OF 12N117W AND IS ADVECTED NE ACROSS THE SOUTHERN 
TIP OF BAJA CALIFORNIA PENINSULA...AND OVER THE AGRICULTURAL 
AREA OF OLD MEXICO NEAR 26N106W...AND FINALLY EVAPORATES ALONG 
THE RIDGE CREST OVER CENTRAL TEXAS. 
 
CROSS EQUATORIAL SE WINDS AT 15 TO 20 KT ARE NOTED OVER THE 
TROPICAL WATERS S OF 05N W OF 115W ARE EXPECTED TO SPREAD A 
LITTLE FURTHER N TO ALONG 07N THROUGH THE NEXT 48 HOURS. 
   
GAP WINDS...LATE NIGHT DRAINAGE FLOW WILL RESULT IN NORTHERLY 15 
TO 20 KT WINDS IN THE GULF OF TEHUANTEPEC AROUND SUNRISE THIS 
MORNING...SUBSIDING THIS AFTERNOON...THEN INCREASING TO 20 TO 25 
KT THU AND FRI MORNINGS. NE WINDS ARE EXPECTED TO CONTINUE TO 
PULSE AT 15 TO 20 KT IN AND JUST DOWNSTREAM OF THE GULF OF 
PAPAGAYO THROUGH THU MORNING...THEN DIMINISH. N WINDS AT 15 TO 
20 KT IN AND DOWNSTREAM OF THE GULF OF PANAMA SHOULD DIMINISH 
THIS AFTERNOON.
     
$$
NELSON