000
AXPZ20 KNHC 200338
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT DEC 20 2008

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 0315 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N86W 5N93W 8N110W 10N123W 8N131W 
6N1140W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM S OF THE 
AXIS BETWEEN 113W-117W. 

...DISCUSSION...

AN OMEGA BLOCKING PATTERN MAINTAINS CONTROL OF THE EASTERN 
PACIFIC DEFINED BY AN UPPER LEVEL LONGWAVE TROUGH THAT EXTENDS 
FROM THE NORTHERN GREAT PLAINS SW ACROSS SOUTHERN CALIFORNIA 
INTO THE AREA AT 32N124W...THEN CONTINUES SW TO A WELL PRONOUNCED
CUT-OFF UPPER LOW MOVING S 20 KT NEAR 24N131W. THE TROUGH EXTENDS
SE TO 15N127W TO 12N121W. A WEAK MID/UPPER LEVEL CYCLONIC 
CYCLONIC CIRCULATION CENTER IS ALONG THE TROUGH NEAR 12N125W.
JET STREAM ENERGY DIVING OVER A HIGH AMPLITUDE LARGE RIDGE W OF
THE AREA AND INTO THE BACK SIDE OF THE LONGWAVE TROUGH WILL AID 
IN THE INTENSIFICATION AND FURTHER SWD MOVEMENT OF THE UPPER LOW 
NEAR 24N132W DURING THE NEXT 48 HOURS. THE CYCLONIC CIRCULATION 
IS FORECAST TO RETROGRADE WSW DURING THE NEXT SEVERAL DAYS. A 
WEAKENING SURFACE TROUGH...REFLECTION OF THE UPPER LEVEL 
LOW...IS MOVING S 15 KT FROM 30N135W TO 24N140W.

STRONG S TO SW FLOW ALOFT GENERALLY BETWEEN 111W AND 121W 
STREAMING FROM THE ITCZ NE TOWARDS BAJA CALIFORNIA...NORTHERN 
MEXICO AND THE SW UNITED STATES CONTINUES TO SUPPORT A FAVORABLE 
UPPER LEVEL ENVIRONMENT ENHANCING CONVECTION WITHIN THIS AREA 
WHERE CIMSS TPW LOOPS SHOW AMPLE MOISTURE CONVERGING DUE TO 
STRONG AND PERSISTENT EASTERLY FLOW IN THE TROPICAL ZONE. 
CONVECTION IS LIKELY TO PERSIST DURING THE NEXT 12-18 HOURS 
UNDER FAVORABLE UPPER LEVEL DIVERGENCE AS NOTED IN THE CIMSS
GUIDANCE...WITH THE ADDITIONAL AID OF A WESTWARD MOVING SURFACE 
TROUGH (TROPICAL WAVE) ALONG 121W/122W FROM 7N-16N. THE 
ASSOCIATED UPPER LEVEL MOISTURE IS EXPECTED TO CONTINUE TO 
ADVECT NE TOWARDS BAJA CALIFORNIA AND NORTHERN MEXICO OVER THE 
NEXT FEW DAYS. LATEST GLOBAL MODEL GUIDANCE SUGGESTS THAT THIS 
TROUGH FEATURE OR EVEN A WEAK SURFACE LOW WILL MOVE WNW OVER 
THIS AREA DURING THE NEXT 48 HOURS WITH ATTENDANT MOISTURE AREA 
AND CONVECTION TRANSLATING WESTWARD WITH THE TROUGH.

THE PRES GRADIENT BETWEEN SURFACE HIGH PRES CENTERED NEAR 
32N124W AND THE SURFACE TROUGH ALONG 121W/122W CONTINUES TO 
MAINTAIN A BROAD SWATH OF 20 TO 25 KT NE WINDS FROM 14N-25N W OF 
116W WITH SEAS IN THE 8 TO 10 FT RANGE. GIVEN THE DURATION
OF THESE WINDS OVER THIS LARGE FETCH AREA SEAS HERE SHOULD
PEAK UP TO 12 FT IN THE NEXT 24 AND 48 HOURS. THE SURFACE HIGH 
IS FORECAST TO MOVE WSW TO NEAR 32N131W IN 24 HOURS...HOWEVER
IT WILL KEEP AN AREA OF NW-N 20 KT WINDS TO THE N OF 21N AND E 
OF 116W...INCLUDING THE GULF OF CALIFORNIA THROUGH AT LEAST THE 
NEXT 36 HOURS WITH SEAS TO 7 FT.

PATCHES OF SCATTERED TO BROKEN STRATOCUMULUS CLOUDS WITH ISOLATED
SHOWERS MOVING SW ARE NOTED TO THE N OF 15N AND W OF 119W.

GAP WINDS...
N-NE WINDS OF 20 KT THROUGH THE GULF OF TEHUANTEPEC AND PAPAGAYO 
ARE EXPECTED TO DIMINISH TO LESS THAN 20 KT WITHIN THE NEXT 
24-48 HOURS...WHILE N WINDS TO 20 KT IN THE GULF OF PANAMA WILL 
DIMINISH TO LESS THAN 20 KT IN ABOUT 12 HOURS. 

$$
AGUIRRE