000
AXPZ20 KNHC 270951
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI NOV 27 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 
0900 UTC.

...ITCZ...
AXIS ALONG 08N78W TO 05N110W TO 08N120W TO 06N136W TO 06N140W.  
SCATTERED MODERATE CONVECTION WITHIN 150 NM OF AXIS FROM 
113W-130W.

...DISCUSSION...
UPPER LEVEL LONGWAVE TROUGH EXTEND FROM SW NEW MEXICO TO 12N120W 
WITH MODERATE TO STRONG SUBSIDING AIR MASS NW OF AXIS.  SHARP 
RIDGE ALONG 132W N OF 08N SUPPLIES ITCZ WITH SUFFICIENT TROPICAL 
MOISTURE TO WARRANT SCATTERED MODERATE CONVECTION ALONG WEAK 
SURFACE TROUGH ALONG 120W...BUT STRONG NW SHEAR AND DRY AIR MASS 
WORKING AGAINST ANY DEVELOPMENT.  SECOND DEEP LAYER TROUGH 
APPROACH NW CORNER OF BASIN BUT EXPECTED TO SHIFT NE AS RIDGE 
LIKELY TO BLOCK MUCH FURTHER SE INTRUSION.  CARIBBEAN RIDGE 
EXTEND INTO E PAC E OF 95W ALSO MAINTAINING DRY SUBSIDING AIR 
MASS UNDER ITS COVERAGE.  ISOLATED CONVECTION NOTED...MAINLY 
OVER CENTRAL AMERICA.  

ELSEWHERE AT THE SURFACE...
COLD FRONT CURRENTLY FROM 32N130W TO 29N140W WEAKENS AND BECOMES 
DIFFUSE AS SUPPORTING UPPER LEVEL TROUGH SHIFT NE.  SURFACE HIGH 
PRES 1035 MB WELL NW OF BASIN MOVES SE SQUEEZING PRES GRADIENT 
AGAINST CALIFORNIA COAST AND INTENSIFYING NE TRADES AS TWO 
SURFACE TROUGHS TRAVEL ALONG ITCZ.  IN ADDITION...HIGH PRES 
SPREADING LARGE LONG PERIOD SWELLS SE INTO E PAC W OF 110W. 

MODEL GUIDANCE STILL AMBIVALENT AS FAR AS TWO SURFACE TROUGHS 
...GFS SPINS BOTH INTO SURFACE LOW PRES.  NAM AND EUROPEAN ARE 
MORE CAUTIOUS IN THEIR DEVELOPMENT AND NOGAPS ONLY DEVELOPS THE 
EASTERNMOST ONE SINCE UPPER ENVIRONMENT APPEARS MORE FAVORABLE. 

FORECAST MAINTAINS TWO TROUGHS MOVING W ALONG ITCZ...BUT 
INCREASE WINDS E OF WESTERNMOST ONE AND MIXES THE SECOND ONE 
WITH HIGH WIND AND SEAS RESULTING OF GULF OF TEHUANTEPEC EVENT.  

...GAP WINDS...
HEALTHY HIGH PRES 1027 MB BEHIND GULF OF MEXICO COLD FRONT 
FUNNELING COLD AIR ACROSS GULF OF TEHUANTEPEC WITH STORM FORCE 
WINDS CONTINUE FRI THEN DIMINISHING TO GALE FORCE SAT BEFORE 
WARNING EXPIRE SAT NIGHT.  

EASTERLY TRADES IN W CARIBBEAN CONTINUE TO CHANNEL WINDS THROUGH 
GULF OF PAPAGAYO AND DOWNSTREAM WATERS TO NEAR 90W THROUGH SAT 
MAINTAINING A FRESH TO STRONG BREEZE. 

$$
WALLY BARNES