000
AXPZ20 KNHC 101516
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU DEC 10 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...06N77W TO 
07N110W TO 07N140W. SCATTERED MODERATE CONVECTION IS WITHIN 60 
NM OF THE POINT 07N121W. SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION IS WITHIN 75 NM OF THE POINT 07N139W.

...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 OVER THE NEXT TWO DAYS. A WEAK COLD FRONT 
EXTENDS FROM 32N126W TO 28N130W THEN STATIONARY TROUGH TO 
22N140. THE FRONT IS ASSOCIATED WITH A BROAD UPPER TROUGH OVER 
THE EASTERN PACIFIC CENTERED OVER FORECAST WATERS ALONG 128W N 
OF 13N. THE FRONT WILL DISSIPATE 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 
110W...INCLUDING SOUTHERN MEXICO AND CENTRAL AMERICA NORTH OF 
10N. 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 HAS BEEN ENHANCING 
CONVECTION ALONG THE ITCZ W OF 120W BUT DURING THE LAST SEVERAL 
HOURS THE CONVECTION HAS DIMINISHED. WITHIN THIS REGION LIES A 
1011 MB LOW PRES SYSTEM EMBEDDED IN THE ITCZ NEAR 09N124W. THE 
LOW IS EXPECTED TO DISSIPATE...LEAVING ONLY A TROUGH WITHIN THE 
20 KT EASTERLY TRADE WINDS BY FRI. 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.

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. 

$$
LL