000
AXPZ20 KNHC 120915
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT DEC 12 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 IS ALONG 7N78W 6N95W 7N115W 7N130W 6N140W. SCATTERED 
MODERATE CONVECTION WITHIN 70 NM S OF AXIS FROM 118W-121W AND 
WITHIN 90 NM S OF AXIS W OF 134W.

...DISCUSSION... 
BROAD UPPER LEVEL TROUGH WITH AXIS FROM NORTHERN GULF CALIFORNIA 
SW TO NEAR 20N115W...OTHERWISE NEARLY ZONAL FLOW COVERS THE AREA 
N OF 20N W OF THE TROUGH. A 95-105 KT JETSTREAM ENTERS THE AREA 
NEAR 32N122W ACROSS NORTHERN BAJA CALIFORNIA INTO NORTHERN 
MEXICO WERE IT TURNS NE INTO TEXAS. SOME HIGH LEVEL MOISTURE IS 
N OF 25N OTHERWISE STRONG SUBSIDENCE WITH DRY STABLE AIR AT THE 
MIDDLE AND UPPER LEVELS OF THE ATMOSPHERE DOMINATES THE AREA N 
OF THE ITCZ W OF 125W.

AN UPPER ANTICYCLONE OVER THE NW CARIBBEAN WITH RIDGE EXTENDING 
WWD OVER SE MEXICO AND MOST OF CENTRAL AMERICA INTO THE EPAC TO 
13N95W IS PRODUCING MODERATE TO STRONG SUBSIDENCE MAINLY E OF 
110W. THE SUBSIDENCE HAS SUPPRESSED ANY STRONG CONVECTION ALONG
THE ITCZ. AN UPPER LEVEL TROUGH IN THE DEEP TROPICS WITH AXIS 
FROM 11N104W TO A CYCLONIC CIRCULATION NEAR 2N99W.

COLD FRONT OVER THE NW PORTION OF THE DISCUSSION AREA WITH SW 
WINDS 20 KT IN A SMALL AREA AHEAD OF THE FRONT. OVERCAST LOW
TOP CLOUDS ARE W OF THE FRONT. A 1020 MB SURFACE HIGH IS 
CENTERED NEAR 26N119W. THREE TROUGH ARE ANALYZED ALONG THE
ITCZ. THE FIRST IS FROM FROM 4N-11N ALONG 105W. NO SIGNIFICANT 
WEATHER ASSOCIATED WITH THIS TROUGH. SECOND TROUGH EXTENDS FROM
11N119W TO 5N121W. SCATTERED SHOWERS W OF THE TROUGH ARE MAINLY 
ASSOCIATED WITH THE ITCZ. ANOTHER TROUGH WITH AXIS FROM 11N131W
TO 5N133W. CONVECTION NEAR THE TROUGH IS AGAIN MAINLY ASSOCIATED
WITH THE ITCZ. HOWEVER THERE REMAINS 20-25 KT NE WINDS E OF THE
TROUGH.

THE MOST SIGNIFICANT MARINE CONDITIONS ARE LARGE AND LONG PERIOD 
NW SWELL W OF AROUND 110W. CURRENTLY THE SWELLS CONTINUE TO 
PROPAGATE SE BEYOND THE EQUATOR. HOWEVER THE SEA HEIGHTS ARE 
BEGINNING TO SUBSIDE. 

WINDS HAVE INCREASED TO 20 KT ACROSS THE GULF OF PAPAGAYO AS  
THE PRES GRADIENT BUILDS ACROSS THE WESTERN CARIBBEAN...ALLOWING 
ELY TRADE WINDS TO FUNNEL ACROSS COSTA RICA AND NICARAGUA 
INTO THE EASTERN PACIFIC. WINDS ARE EXPECTED TO INCREASE TO 25 
KT TODAY.
  
$$
DGS