000
AXPZ20 KNHC 170925
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU DEC 17 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 7N77W 7N90W 6N105W 8N130W 6N140W. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION WITHIN 100 NM S OF AXIS FROM 
110W TO 114W.

...DISCUSSION...
AN UPPER LEVEL RIDGE HAS MOVED INTO THE NW PORTION OF THE 
DISCUSSION AREA...WITH AXIS FROM 32N127W THEN FLATTENING NEAR
17N140W. MODERATE TO STRONG SUBSIDENCE WITH DRY STABLE AIR AT 
THE MIDDLE AND UPPER LEVELS OF THE ATMOSPHERE COVERS THE AREA N 
OF THE ITCZ TO 25N W OF 125W. SOME HIGH LEVEL MOISTURE IS N OF 
25N WITH SCATTERED CIRRUS CLOUDS. AN UPPER LEVELSHORTWAVE TROUGH 
IS E OF THE RIDGE WITH AXIS FROM NORTHERN BAJA CALIFORNIA TO 
24N120W. BROKEN HIGH CLOUDS ARE WITHIN 220 NM E OF THE TROUGH 
AXIS.

A SHARP MID TO UPPER LEVEL TROUGH EXTENDS FROM NW MEXICO NEAR 
THE BIG BEND OF TEXAS ACROSS CENTRAL MEXICO TO 13N110W. A WEAK
JETSTREAM E OF THE TROUGH IS ADVECTING HIGH LEVEL MOISTURE OVER
EASTERN MEXICO. OTHERWISE MODERATE TO STRONG SUBSIDENCE IS N OF 
THE ITCZ E OF 110W. THE SUBSIDENCE HAS SUPPRESSED ANY 
SIGNIFICANT CONVECTION ALONG THE ITCZ.

A 1025 MB HIGH PRES IS CENTERED NEAR 30N128W. A BROAD AREA OF 
MODERATE TO STRONG TRADE WINDS ON THE SOUTHERN PERIPHERY OF THE 
HIGH PRES...MAINLY FROM 08N TO 20N W OF 120W. A COUPLE OF 
TROUGHS ARE ANALYZED ALONG THE ITCZ. THE FIRST ONE EXTENDS FROM 
10N112W TO A 1008 MB LOW PRES NEAR 7N116W TO 3N117W. A FEW 
SHOWERS ARE NEAR LOW. THE SECOND TROUGH WITH AXIS FROM 11N130W 
TO 5N133W. ISOLATED SHOWERS ALONG THE TROUGH.

HIGH PRES BUILDING ACROSS SOUTHERN MEXICO BEHIND A COLD FRONT
HAS TIGHTENED THE PRES GRADIENT AND WINDS HAVE INCREASED TO
GALE FORCE THROUGH THE GULF OF TEHUANTEPEC. THE WINDS ARE
EXPECTED TO DECREASE TO BELOW GALE FORCE BY EARLY FRI.

SEA HEIGHTS HAVE INCREASED ACROSS THE NW PORTION OF THE AREA
WITH SEAS OF UP TO 16 FT.

NE TO E WINDS OF 20 TO 25 KT ARE STILL BLOWING ACROSS THE 
GULF OF PAPAGAYO AS A TIGHT PRES GRADIENT ACROSS THE WESTERN 
CARIBBEAN IS ALLOWING ELY TRADE WINDS TO FUNNEL ACROSS COSTA 
RICA AND NICARAGUA INTO THE EASTERN PACIFIC. THESE WINDS ARE 
EXPECTED TO DECREASE DURING THE NEXT 24 HOURS. 

FOR ADDITIONAL INFORMATION PLEASE VISIT 
HTTP://WWW.HURRICANES.GOV/MARINE
  
$$
DGS