000
AXPZ20 KNHC 012201
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE DEC 01 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 
2100 UTC.

...ITCZ...
THE ITCZ AXIS IS ALONG 05N77W TO 08N98W TO 07N106W TO 08N113W TO 
06N123W TO 10N140W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION WITHIN 60 NM EITHER SIDE OF AXIS BETWEEN 111W AND 
118W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION WITHIN 60 
NM EITHER SIDE OF AXIS W OF 132W.

...DISCUSSION...
AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 08N126W WITH RIDGE 
EXTENDING N TO CALIFORNIA. A SHORTWAVE TROUGH IS LOCATED IN THE 
N PORTION OF THE FORECAST AREA W OF 128W. IN RESPONSE TO THE 
SHORTWAVE...THE SURFACE HIGH NEAR 28N125W HAS WEAKENED 
SLIGHTLY...THOUGH 1740 UTC ASCAT PASS INDICATES FRESH TRADEWINDS 
FROM 13N TO 16N BETWEEN 112W AND 127W. THIS IS S OF A WEAKENED 
FRONTAL BOUNDARY/SHEAR LINE FROM 19N105W TO 16N121W.  

CONVECTION IS ACTIVE WITHIN 60 NM OF THE ITCZ AXIS BETWEEN 111W 
AND 118W AND W OF 132W. THIS ACTIVE CONVECTION IS ASSOCIATED 
WITH TWO SURFACE LOW PRESSURE AREAS...ONE NEAR 07N115W AND THE 
OTHER NEAR 08N134W. THE 1740 UTC ASCAT PASS DEPICTED THE 
CYCLONIC CIRCULATION AROUND THE LOW CENTERED NEAR 07N115W...WITH 
FRESH TO STRONG WINDS WITHIN 140 NM OF THE NORTHERN SEMICIRCLE. 

LOOKING AHEAD...UPPER RIDGE AXIS REBUILDS ALONG 135W AHEAD OF 
A STRONG UPPER LONG WAVE TROUGH DIGGING EASTWARD TO THE N OF 
HAWAII. THE LONG WAVE UPPER TROUGH COMES IN PHASE WITH A REMNANT 
OF THE UPPER TROUGH NOW EAST OF HAWAII...WHICH LIFTS TO THE NE 
THROUGH THU. GLOBAL MODELS SHOW A SURFACE TROUGH FORMING OVER 
THE WATERS W OF 130W IN CONJUNCTION WITH THE UPPER TROUGH BY THU 
NIGHT...THOUGH THERE STILL REMAINS SOME DISAGREEMENT TO THE 
STRENGTH OF THE SURFACE FEATURE...WITH THE GFS BEING MOST 
AGGRESSIVE. 

$$

AL