000
AXPZ20 KNHC 210953
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.

...TROPICAL LOW...

.A PERSISTENT SURFACE LOW PRES IS MEANDERING NEAR 07N88W 
ESTIMATED AT 1009 MB. WEAK CONVECTION IS NOTED WITHIN ABOUT 210 
NM E OF CENTER. SE TO S TO SW WINDS AT 15 TO 20 KT ARE NOTED 
WITHIN ABOUT 120 NM OVER THE E SEMICIRCLE WITH SEAS TO 7 FT. 
THE LOW IS EXPECTED TO MOVE W TO NEAR 07N94W AND WEAKEN TO ABOUT 
1011 MB IN 24 HOURS AND REACH NEAR 08N96W IN 48 HOURS WITH 
LITTLE CHANGE IN WIND AND SEAS.


...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 03N78W 
THROUGH THE EMBEDDED LOW PRES AT 07N88W...THEN THE AXIS DROPS S 
TO NEAR 04N93W...THEN TURNS NW TO 14N120W THEN SW TO NEAR 
06N140W. THE LOW PRES THAT WAS EMBEDDED IN THE ITCZ NEAR 08N118W 
HAS WEAKENED TO A TROUGH ORIENTATED N TO S FROM 08N125W TO 
15N120W. THIS TROUGH IS EXPECTED TO DRIFT W AND GRADUALLY LOSE 
IDENTITY OVER THE NEXT 24 HOURS AS NE TRADES INCREASE OVER THE 
DEEP TROPICS W OF 125W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION CONTINUES TO FLARE WITHIN 120 NM OF 09.5N117W. 

...DISCUSSION...

A LONG WAVE TROUGH DOMINATES THE E PACIFIC WITH ITS MEAN AXIS N 
OF 28N ALONG 135W. A VIGOROUS SHORT WAVE IS ROTATING THROUGH 
PATTERN AND JUST COMING INTO THE NW PORTION OF THE DISCUSSION 
AREA WITH THE ASSOCIATED SURFACE FRONT ALONG 32N134W TO 29N140W. 
AN INITIAL COLD FRONT IS SLOWING AND WEAKENING FROM 32N118W T0 
20N140W. THE SECOND COLD FRONT IS EXPECTED TO OVERTAKE THE 
INITIAL FRONT LATE WED REACHING THE NORTHERN BAJA CALIFORNIA 
PENINSULA EARLY WED NIGHT. SEAS W OF THE FRONT WILL BUILD TO
ABOUT 16 FT IN 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 BY EARLY THU...WITH SOUTHERLY SURFACE WINDS 
INCREASING TO 20 TO 25 KT AHEAD THE FRONT OVER THE GULF WATERS N 
OF 29N.  

AN UPPER ANTICYCLONE IS ESTIMATED NEAR 05N106W WITH AN UPPER 
RIDGE EXTENDING NNE THROUGH 32N103W AND ACROSS THE ENTIRE 
CENTRAL CONUS. A 600 NM WIDE DENSE MOISTURE PLUME...ORIGINATING 
IN THE CENTRAL PACIFIC...IS STREAMING E INTO THE DISCUSSION AREA 
WITH ITS AXIS ALONG 19N140W TO 21N130W...THEN THE PLUME TURNS NE 
ALONG THE NW PERIPHERY OF UPPER RIDGE THROUGH 32N120W...THEN 
TURNS E ACROSS THE SOUTHERN CONUS. THE MOST DENSE MOISTURE 
APPEARS E OF 120W AT THE MOMENT...WITH THE MOISTURE PLUME W OF 
120W MUCH LESS DENSE. FURTHER W...THE VIGOROUS SHORT WAVE MOVING 
SE INTO THE AREA NEAR 27N135W IS ACCOMPANIED BY DRIER AIR AND 
MAY DISRUPT SOME OF THIS MOISTURE BELT...PERHAPS SOME RELIEF FOR 
THE CONTINUED PRECIPITATION PROBLEM OCCURRING OVER THE SW CONUS.

UPPER DIFFLUENCE OVER THE DEEP TROPICS IN THE VICINITY OF  
11N115W IS ENHANCING ITCZ CONVECTION AS PREVIOUSLY DESCRIBED... 
AND IS ALSO ENHANCING SCATTERED MODERATE CONVECTION A LITTLE 
FURTHER N WITHIN 60 NM EITHER SIDE OF A LINE FROM 15N113W TO 
15N120W. THE RESULTANT DEBRIS MOISTURE IS ADVECTED N...BUT 
APPEARS TO EVAPORATE JUST AS IT CROSSES OVER THE SOUTHERN BAJA 
CALIFORNIA PENINSULA AND THE MEXICAN COAST AT 24N106W. OTHERWISE
THE UPPER LEVELS ARE VERY DRY S OF 15N W OF 123W AND S OF 257N E 
OF 125W.

CROSS EQUATORIAL SE WINDS ARE EXPECTED TO SPREAD N ACROSS THE 
EQUATOR OVER THE PACIFIC WATERS S OF 07N W OF 130W IN 24 HOURS 
AND AND EXPECTED TO COVER THE AREA W OF 120W IN ABOUT 48 HOURS. 
   
GAP WINDS...EXPECTING SOME LATE NIGHT DRAINAGE FLOW TO RESULT IN 
NORTHERLY 15 KT WINDS IN THE GULF OF TEHUANTEPEC AROUND SUNRISE 
THIS MORNING...SUBSIDING THIS AFTERNOON...THEN INCREASING TO 15 
TO 20 KT WED MORNING AND 20 TO 25 KT ON THU AND FRI MORNINGS. 
GALE CONDITIONS ARE POSSIBLE BEGINNING SAT NIGHT. NE WINDS ARE 
EXPECTED TO CONTINUE TO PULSE AT 15 TO 20 KT IN AND JUST 
DOWNSTREAM OF THE GULF OF PAPAGAYO THROUGH WED MORNING...THEN 
DIMINISH AS THE TROPICAL LOW PRES MOVES W TO NEAR 08N96W AND 
WEAKENS.
     
$$
NELSON