000
AXPZ20 KNHC 010916
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE DEC 01 2009

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 ITCZ AXIS IS ALONG 05N77W TO 08N98W TO 09N112W TO 06N125W TO 
10N135W TO 09N140W. SCATTERED MODERATE TO ISOLATED STRONG IS 
SEEN FROM 07N TO 10N W OF 132W. SIMILAR CONVECTION IS NOTED 
WITHIN 120 NM SW QUADRANT OF LOW PRES NEAR 09N113W.

...DISCUSSION...
ALOFT...A LARGE MID TO UPPER LEVEL RIDGE REMAINS THE DOMINANT 
FEATURE OVER THE DISCUSSION AREA W OF 110W. A JET-STREAM BRANCH 
WITH CORE WINDS OF 110 KT ENTERS THE REGION NEAR 25N140W THEN 
CONTINUES ALONG 30N125W TO 22N108W INTO WEST-CENTRAL MEXICO. 
THIS JET ROUNDS THE BASE OF A CUT-OFF LOW SPINNING OVER THE SW 
CONUS. AN UPPER-LEVEL TROUGH EXTENDS FROM THE LOW CENTER ACROSS 
WESTERN MEXICO TO NEAR 07N107W. THE REMAINDER OF THE REGION IS 
UNDER THE INFLUENCE OF AN UPPER-LEVEL HIGH CENTERED JUST W OF 
THE GALAPAGOS ISLANDS WHICH DOMINATES THE FORECAST AREA E OF 
100W. A LONGWAVE TROUGH AND THE ATTENDANT COLD FRONT IS 
APPROACHING THE NW PORTION OF THE AREA WITH THE LEADING EDGE OF 
THIS FEATURE NOW AT 30N140W...BUT IT WILL WEAKEN AS IT 
ENCOUNTERS THE RIDGE WITH THE MAJORITY OF ANY ASSOCIATED ENERGY 
AND MOISTURE REMAINING N OF AREA. 

AT THE SURFACE...A 1022 MB HIGH PRES LOCATED NEAR 29.5N128W 
EXTENDS A RIDGE OVER THE FORECAST WATERS N OF 13N AND W OF 110W. 
PRES GRADIENT BETWEEN THE RIDGE AND LOWER PRES ALONG THE ITCZ 
AXIS IS GENERATING A BELT OF TRADE WINDS OF 20 KT FROM 13N TO 
21N W OF 115W. THIS SYSTEM IS FORECAST TO SLIGHTLY WEAKEN DURING 
THE NEXT 48 HOURS AS ANOTHER LOW PRES SYSTEM APPROACHES THE FAR 
NW CORNER OF THE FORECAST AREA. AS A RESULT...THE TRADES WILL 
DIMINISH IN STRENGTH AND COVERAGE DURING THE SAME TIME PERIOD. A 
WEAK SURFACE TROUGH...WHICH IS THE REMNANTS OF A PREVIOUS LOW 
PRES...RUNS FROM 12N112N TO 06N114W. A WEAK 1009 MB LOW IS ALONG 
THE TROUGH AXIS NEAR 09N113W. WINDS HAVE DIMINISHED EITHER SIDE 
OF THE TROUGH BASED ON AN ASCAT PASS FROM AROUND 0500 UTC. THIS 
FEATURE IS EXPECTED TO DISSIPATE WITHIN THE NEXT 24 HOURS. 
ANOTHER SFC LOW PRES IS ANALYZED NEAR 12N134W. MODEL GUIDANCE 
SUGGESTS THAT THIS LOW WILL MOVE W OF AREA IN ABOUT 24 HOURS. 
HOWEVER...PRES GRADIENT BETWEEN THE LOW PRES AND THE RIDGE TO 
THE N WILL PRODUCE AN AREA OF E TO SE WINDS IN THE 20 TO 25 KT 
RANGE FROM 14N TO 22N W OF 130W DURING THE NEXT 24 TO 48 HOURS 
AS REFLECTED IN THIS FORECAST PACKAGE. 

REGIONAL SEAS ARE DOMINATED BY LONG PERIOD NW SWELLS. SEAS IN 
EXCESS OF 8 FT ARE NOTED MAINLY W OF 110W. ANOTHER EPISODE OF 
LARGE AND LONG PERIOD NW SWELLS WILL REACH THE NW CORNER OF THE 
AREA AT ABOUT 03/0600 UTC AND SPREAD SE LATE IN THE FORECAST 
PERIOD. 

GAP WINDS...
EASTERLY TRADE WINDS ACROSS THE SW CARIBBEAN CONTINUE TO FUNNEL 
WINDS THROUGH GULF OF PAPAGAYO AND DOWNSTREAM WATERS TO 89W 
THROUGH TUE NIGHT...THEN WILL DIMINISH TO LESS THAN 20 KT AS 
THE TRADES EASE. 

$$
GR