000
AXPZ20 KNHC 100948
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU DEC 10 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 
0800 UTC.

...ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 07N78W TO 08N98W TO 09N110W TO 
10N122W TO 07N140W. SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION CAN BE FOUND WITHIN 75 NM EITHER SIDE OF THE ITCZ 
AXIS BETWEEN 133W AND 138W. SCATTERED MODERATE CONVECTION LIES 
WITHIN 75 NM N OF AXIS THE ITCZ BETWEEN 81W AND 83W AS WELL AS S 
OF THE ITCZ AXIS BETWEEN 108W AND 113W AND WITHIN 180 NM S OF 
AXIS THE ITCZ BETWEEN 120W AND 122W.  

...DISCUSSION... 
SEAS W OF 110W ARE BEING DOMINATED BY LARGE AND LONG PERIOD NW 
SWELL...WITH WAVE PERIODS OF UP TO 20 SECONDS AND SIGNIFICANT 
WAVE HEIGHTS AS HIGH AS 18 FEET. THIS SWELL EVENT WILL CONTINUE 
TO PROPAGATE SE ACROSS MUCH OF THE FORECAST AREA OVER THE NEXT 
TWO DAYS. THIS SWELL IS MOVING OUT AHEAD OF A COLD FRONT 
EXTENDING FROM 30N129W TO 26N133W THEN STATIONARY TO 22N140. THE 
0210 UTC WINDSAT PASS SHOWED S TO SW WINDS STILL TO 20 KT N OF 
29N WITHIN 150 NM E OF FRONT. THIS FRONT IS ASSOCIATED WITH A 
BROAD UPPER TROUGH OVER THE EASTERN PACIFIC CENTERED OVER 
FORECAST WATERS ALONG 130W N OF 13N. THE FRONT WILL DISSIPATE 
LATER TODAY IT BECOMES ABSORBED WITHIN ANOTHER FRONTAL SYSTEM 
NORTH OF THE FORECAST AREA WITHIN THIS BROAD TROUGH. 

THERE IS AN UPPER LEVEL RIDGE ANCHORED ON AN ANTICYCLONE 
CENTERED ONSHORE JUST NW OF THE GULF OF TEHUANTEPEC AND 
EXTENDING SW TO NEAR 10N120W. STRONG UPPER LEVEL SUBSIDENCE AND 
IMPLIED DRY AIR MASS IS SEEN SOUTH OF THE RIDGE AXIS E OF 
107W...INCLUDING SOUTHERN MEXICO AND MOST OF CENTRAL AMERICA. 
SLY WINDS BETWEEN THIS RIDGE AND THE AFOREMENTIONED BROAD UPPER 
LEVEL TROUGH ARE TRANSPORTING ABUNDANT MID TO UPPER LEVEL 
MOISTURE FROM THE ITCZ TO THE N AND NE INTO NORTHERN MEXICO 
AROUND THE NW PORTION OF THE ANTICYCLONE. DIFFLUENCE NEAR THE 
REAR RIGHT QUADRANT OF THIS UPPER JET IS ENHANCING CONVECTION 
ALONG THE ITCZ W OF 120W. WITHIN THIS REGION LIES A 1011 MB LOW 
PRES SYSTEM EMBEDDED IN THE ITCZ NEAR 10N123W. SCATTERED 
MODERATE CONVECTION CAN BE FOUND WITHIN 90 NM OF THIS LOW. THE 
LOW IS EXPECTED TO DISSIPATE...LEAVING ONLY A TROUGH WITHIN THE 
20 KT EASTERLY TRADE WINDS BY FRI. MEANWHILE...A SURFACE TROUGH 
LIES TO ITS W FROM 10N133W TO 05N136W AND SCATTERED MODERATE 
WITH ISOLATED STRONG CONVECTION LIES WITHIN 120 NM EITHER SIDE 
OF THIS TROUGH FROM 06N AND 08N. ON SAT...THE BROAD UPPER TROUGH 
TO THE N WILL SHIFT NORTHEASTWARD AND THE SOUTHERN STREAM UPPER 
JET BUILD OVER THESE TWO SURFACE TROUGHS. THE SHEAR ALOFT SHOULD 
LESSEN THE CHANCE OF DEEP CONVECTION DEVELOPING NEAR THESE 
TROUGHS...BOTH OF WHICH ARE EXPECTED TO DISSIPATE OVER THE 
WEEKEND.

THE NEXT COLD FRONT WILL ENTER THE FAR NW PORTION OF THE 
FORECAST REGION FRI...WITH SW WINDS OF 20 TO 25 KT AHEAD OF THE 
FRONT. NW WINDS OF 20 KT AND SEAS OF UP TO 11 FT ARE EXPECTED IN 
THE WAKE OF THE FRONT. 

GAP WINDS...
WINDS ARE EXPECTED TO INCREASE TO 20 KT ONCE AGAIN BY EARLY FRI 
MORNING ACROSS THE GULF OF PAPAGAYO AS THE DRAINAGE FLOW OFF THE 
CENTRAL AMERICA LANDMASS INCREASES AND THE PRES GRADIENT BUILDS 
ACROSS THE WESTERN CARIBBEAN...ALLOWING EASTERLY TRADE WINDS 
TO BLEED ACROSS COSTA RICA AND NICARAGUA INTO THE PACIFIC. 

$$
SCHAUER