000
AXPZ20 KNHC 092138
TWDEP 

TROPICAL WEATHER DISCUSSION     
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT DEC 09 2006

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2130 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG...5N78W 5N90W 6N100W 5N111W 6N123W 
8N131W 7N140W. SCATTERED MODERATE ISOLATED STRONG WITHIN 120 NM 
N OF AXIS BETWEEN 125W AND 128W...AND ALSO BETWEEN 131W AND 
136W. SCATTERED MODERATE WITHIN 120 NM EITHER SIDE OF AXIS W OF 
137W.

...DISCUSSION...

A VERY PROGRESSIVE AND ACTIVE PATTERN DOMINATES THE REGION WITH 
A MID TO UPPER LEVEL TROUGH MOVING ACROSS NRN MEXICO...AND A 
SECOND MORE PRONOUNCED TROUGH MOVING INTO THE NORTHWEST PORTION 
OF THE AREA EXTENDING FROM 30N132W TO 23N140W. IN BETWEEN THE 
TROUGHS A BROAD RIDGE COVERS THE AREA WITH A MEAN AXIS EXTENDING 
FROM A MID/UPPER LEVEL ANTICYCLONIC CIRCULATION NEAR 9N127W 
NORTHEASTWARD THROUGH 25N115W TO A CREST WELL NORTH OF THE 
REGION OVER ARIZONA. A SHEARED MID/UPPER LEVEL CYCLONIC 
CIRCULATION...LEFT BEHIND BY THE FIRST TROUGH EXTENDS WITHIN 60 
NM EITHER SIDE OF A LINE FROM 21N131W SOUTHWEST TO 17N141W. 
STRONG UPPER LEVEL SUBSIDENCE AND ASSOCIATED DRY AIR IN THE WAKE 
OF THE FIRST TROUGH COVERS THE AREA NORTH OF 17N AND EAST OF 
120W OVER MOST OF NRN MEXICO. CONFLUENT FLOW INTO THE BASE OF 
THE SECOND TROUGH IS ALSO RESULTING IN A NARROW BAND OF MODERATE 
TO STRONG SUBSIDENCE OVER THE NORTHWEST PART OF THE AREA NORTH 
OF 22N WEST OF 130W. LIMITED UPPER LEVEL MOISTURE IS SEEN OVER 
THE EASTERN PORTION OF THE AREA FROM 9N-14N BETWEEN 
97W-107W...HOWEVER IT HAS DECREASED IN COVERAGE OVER THE PAST 24 
HOURS AS THE SUBSIDENCE AREA DESCRIBED CONTINUES TO PRESS 
EASTWARD DRYING THE ATMOSPHERE OVER THIS AREA. DIFLUENT MID TO 
UPPER LEVEL FLOW WEST OF THE ANTICYCLONIC CIRCULATION NEAR 
9N127W IS SUPPORTING ITCZ CONVECTION WEST OF 125W.

AT THE SURFACE...A SURFACE TROUGH EXTENDS FROM 32N118W TO 
21N130W. A COLD FRONT EXTENDS FROM 32N127W TO 25N140W. NORTHWEST 
WINDS HAVE DECREASED TO 20-25 KT BEHIND THE FRONT. HOWEVER...THE 
MAIN PROBLEM AFFECTING THE REGION WITH RESPECT TO THE FRONTS ARE 
THE VERY LARGE NW-N SWELLS THAT CONTINUE TO SPREAD THROUGHOUT 
MUCH OF THE WESTERN AND CENTRAL SECTIONS OF THE DISCUSSION AREA 
OVER THE NEXT FEW DAYS AS THE COLD FRONT WEAKENS AND DISSIPATES. 
WAVEWATCH MODEL INDICATES MAXIMUM WAVE HEIGHTS TO BE LESS THAN 
THE 24 FT IT HAD PREVIOUSLY FORECASTED...HOWEVER NUMEROUS BUOY 
AND SHIP OBSERVATIONS JUST NORTH OF THE REGION INDICATE MAXIMUM 
SEAS TOPPING OUT IN THE 20 FT RANGE. EXPECT VERY LARGE 
SWELLS...POSSIBLY IN THE 17-20 FT RANGE TO SPREAD INTO THE 
NORTHWEST PORTION THROUGH THE NEXT 24 HOURS THEN SUBSIDE TO 17 
FT IN ABOUT 24 HOURS AND SLOWLY CONTINUE TO SUBSIDE THEREAFTER. 
THE COLD FRONT IS FORECAST TO QUICKLY MOVE EASTWARD AND WEAKEN 
OVER THE EASTERN PART OF THE REGION NEAR THE SOUTHERN CALIFORNIA 
AND NORTHERN BAJA COAST.

OVER THE FAR EASTERN PART OF THE REGION A MID TO UPPER LEVEL 
RIDGE EXTENDS FROM AN ANTICYCLONE OVER NRN VENEZUELA WESTWARD
ALONG 12N/13N TO 105W. THIS RIDGE IS EMBEDDED IN THE AREA OF 
MODERATE TO STRONG SUBSIDENCE DESCRIBED EARLIER IN THE 
DISCUSSION.

GAP WINDS...
SURFACE OBSERVATIONS FROM SALINA CRUZ INDICATE NLY WINDS OF 
20-30 KT OVER THE PAST SEVERAL HOURS. THESE OBSERVATIONS COUPLED 
WITH THE EARLIER QUIKSCAT PASS INDICATING 40-45 KT WINDS 
SUGGESTS THE GALE EVENT CONTINUES WITH ESTIMATED WINDS OF 30-40 
KT. WINDS SHOULD DECREASE TO LESS THAN GALE FORCE WITHIN 24 
HOURS.

NE WINDS OF 20 KT ACROSS THE GULF OF PAPAGAYO WEST TO 88W ARE 
EXPECTED TO CONTINUE THROUGH THE NEXT 48 HOURS THEN DIMINISH TO 
LESS THAN 20 KT.

$$
COBB