000
AXPZ20 KNHC 020332
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED DEC 02 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 
0300 UTC.

...ITCZ...
THE ITCZ AXIS IS ALONG 07N77W TO 06N81W TO 08N98W TO 07N107W TO 
08N114W TO 06N124W TO 10N140W. SCATTERED MODERATE TO ISOLATED 
STRONG WITHIN 60 NM EITHER SIDE OF AXIS BETWEEN 112W AND 120W. 
SCATTERED MODERATE WITHIN 120 NM EITHER SIDE OF AXIS W OF 131W.

...DISCUSSION...
AN UPPER LEVEL SHORTWAVE TROUGH CONTINUES TO MOVE ACROSS THE N 
PORTION OF THE FORECAST AREA N OF 24N...NEAR 122W. THIS FEATURE 
HAS WEAKENED THE SURFACE HIGH PRESSURE THAT HAS PREVAILED OVER 
THE FORECAST AREA...AND HAS BROUGHT A DECREASE IN THE AREAL 
COVERAGE OF TRADES GREATER THAN 20 KT. THE SURFACE HIGH PRESSURE 
WILL REMAIN WEAK OVER THE NEXT SEVERAL DAYS AS A PROGRESSIVE 
UPPER LEVEL PATTERN...WITH TWO MORE SHORTWAVE TROUGHS...EXPECTED 
TO MOVE ACROSS THE AREA THROUGH THIS WEEKEND. 

THE ONLY AREAS OF ACTIVE CONVECTION OVER THE FORECAST AREA 
REMAIN ASSOCIATED WITH TWO LOW PRESSURE CENTERS...ONE NEAR 
08N116W AND THE OTHER NEAR 08N135W. DESPITE THE SHORTWAVE TROUGH 
MOVING ACROSS THE N PORTION OF THE AREA...LIMITED MOISTURE...AS 
DEPICTED BY TPW LOOPS HAS PRECLUDED CONVECTIVE ACTIVITY. 

GAP WINDS OF 20 KT CONTINUES OVER THE GULF OF PAPAGAYO AS FRESH 
TRADEWIND FLOW IN THE SW CARIBBEAN FUNNELS THROUGH THE GAP. THE 
WINDS ARE GREATEST DURING THE OVERNIGHT AND EARLY MORNING HOURS 
WITH THE AID OF DRAINAGE FLOW. 

LOOKING AHEAD...THE SURFACE LOW PRESSURE CENTERED NEAR 08N135W 
IS FORECAST TO SHIFT WESTWARD AND INTERACT WITH AN UPPER 
LEVEL TROUGH CURRENTLY EAST OF HAWAII. THIS WILL HALT THE 
WESTWARD PROGRESS OF THE SURFACE LOW. THERE IS DISAGREEMENT TO 
THE RESULT OF THIS INTERACTION...WITH THE ECMWF LIFTING OUT THE 
UPPER TROUGH SOONER THAN THE GFS. AS A RESULT...THE GFS IS MORE 
AGGRESSIVE MAINTAINING THE SURFACE LOW IN THE W PORTION OF THE 
FORECAST AREA...WHILE THE ECMWF WEAKENS THE CLOSED CIRCULATION 
INTO AN OPEN TROUGH BY THU NIGHT.

$$

AL