000
AXPZ20 KNHC 191604
TWDEP 

TROPICAL WEATHER DISCUSSION     
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON DEC 18 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 5N77W 5N100W 8N112W 7N140W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN 
120 NM EITHER SIDE OF AXIS E OF 82W AND WITHIN 180 NM TO THE N 
OF AXIS TO THE W OF 107W.

...DISCUSSION...

THE SUBTROPICAL PORTION OF THE DISCUSSION AREA IS DOMINATED BY A 
SHORTWAVE TROUGH OVER THE WESTERN CONUS WITH AN EMBEDDED UPPER 
CYCLONE NEAR 34N114W. AN UPPER TROUGH EXTENDS SW ALONG 32N114W 
TO A BASE NEAR 18N122W. A BAND OF DRY UPPER AIR IS INDICATED 
WITH IN THE AREA FROM 20N TO 32N BETWEEN130W AND 112W.

AN UPPER RIDGE ALONG 17N136W 24N134W IS RAPIDLY ERODING 
AS ANOTHER STRONG SHORTWAVE APPROACHES THE NW PORTION. THE 
TROUGH AXIS CURRENTLY ALONG 34N138W 29N141W THROUGH AN UPPER 
CYCLONE AT 23N142W WITH THE TROUGH CONTINUING SW TO NEAR 
16N150W. DRY UPPER AIR ACCOMPANIES THE TROUGH ROUGHLY WITHIN 120 
NM OF ITS AXIS. UPPER DEBRIS MOISTURE IS STILL TRAPPED BETWEEN 
THE TWO UPPER TROUGHS...ROUGHLY N OF 17N BETWEEN 142W AND 132W.
THE ASSOCIATED SURFACE FRONT ACCOMPANYING THE SECOND TROUGH 
WILL ADVECT A NEW SERIES OF NW SWELLS IN THE DISCUSSION AREA. 

THE TROPICS IS DOMINATED BY AN UPPER ANTICYCLONE ESTIMATED NEAR 
10N107W WITH A RIDGE EXTENDING W OVER THE ITCZ TO A CREST AT 
7N145W ENHANCING ITCZ CONVECTION BETWEEN 107W AND 142W. A RIDGE 
ALSO EXTENDS NE TO A CREST OVER THE BAY OF CAMPECHE NEAR 21N93W 
AND ENHANCES CONVECTION UNDER THE RIDGE NEAR 13N107W. THE 
RESULTANT DEBRIS MOISTURE FROM BOTH CONVECTIVE AREAS IS ADVECTED 
NE IN THE ANTICYCLONIC FLOW AROUND THE PERIPHERY OF THE RIDGE 
AND INTO THE SW FLOW ASSOCIATED WITH THE TROUGH TO THE N. THE 
MOISTURE PLUME CONTINUES NE ACROSS CENTRAL OLD MEXICO AND 
SPILLING INTO THE S CENTRAL CONUS. 
 
AN UPPER LEVEL ANTICYCLONE IS OVER SW GUATEMALA NEAR 15N93W WITH 
A RIDGE EXTENDING SW TO 10N98W...BUT RETRACTING E WITH TIME. 
THE UPPER LEVELS ARE DRY OVER THE TROPICS E OF 102W. 

LOW LEVELS...HIGH PRES IS CENTERED NEAR 32N131W 1028 MB RIDGING 
SE TO NEAR 19N112W. BRISK EASTERLY TRADES CONTINUE SW OF THE 
RIDGE WITH SEAS GENERALLY DECREASING AND NW SWELL SUBSIDE.

GAP WINDS...NLY WIND TO 20 KT PRESENTLY IN GULF OF TEHUANTEPEC 
EXPECTED TO DIMINISH LATER TODAY. ENE WINDS 20 KT WITH SURGES TO 
25 KT SEAS TO 8 FT IN THE GULF OF PAPAGAYO EXPECTED TO CONTINUE 
FOR AT LEAST ANOTHER 48 HOURS.

$$
NELSON