000
AXPZ20 KNHC 212135
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN DEC 21 2008

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 04N77W 07N85W 05N100W 10N120W  
12N133W 08N140W. SCATTERED MODERATE CONVECTION IS FROM 08N TO 
14N BETWEEN 130W AND 138W... AND FROM 07N TO 09N BETWEEN 138W 
AND 140W.   

...DISCUSSION...
A REX BLOCK PATTERN IS WELL ESTABLISHED OVER MUCH OF THE 
DISCUSSION AREA WITH AN UPPER LOW SPINNING NEAR 20N137W...FLAT 
TROUGHING OVER NRN BAJA AND MUCH OF THE SW CONUS AND LARGE 
AMPLIFIED RIDGING JUST W OF THE AREA...INCLUDING OVER THE 
HAWAIIAN ISLANDS. INSTABILITY NEAR THE UPPER LOW AND LOW-LEVEL 
CONVERGENCE ALONG AN ASSOCIATED SFC TROUGH IS PRODUCING 
SCATTERED SHOWERS AND TSTMS FROM 14N-23N BETWEEN 130W-133W. MORE 
INTENSE CONVECTION LIES IN AN UPPER DIFFLUENT ZONE E OF THE 
UPPER LOW FROM 15N-20N BETWEEN 118W-125W. THIS STAGNANT PATTERN 
IS EXPECTED TO HOLD FOR A FEW MORE DAYS BEFORE SLOWLY BREAKING 
DOWN AS A SERIES OF SHORTWAVES HELP DEEPEN THE TROUGH OVER THE 
NE PORTION OF THE AREA. 

AT THE SFC...TIGHT PRES PATTERN BETWEEN A 1029 MB HIGH NEAR 
31N137W AND TROUGHING ASSOCIATED WITH THE UPPER LOW IS PRODUCING 
A SWATH OF 20-30 KT NE/E TRADES FROM 15N-27N. THESE STRONG WINDS 
COMBINED WITH RESIDUAL N SWELL IS ELEVATING SEAS ABOVE 8 FT OVER 
MUCH OF THE W PORTION OF THE ZONE. THE SFC FEATURES DISCUSSED 
WILL SHIFT W OVER THE NEXT COUPLE OF DAYS...AND CONSEQUENTLY THE 
AREA OF STRONG WINDS WILL FOLLOW. 

GAP WINDS...
SEVERAL OF THE GAPS ARE ACTIVE TODAY...THOUGH NONE ARE OF 
WARNING CRITERIA. A QSCAT PASS REVEALED NW 20-25 KT WINDS OVER 
MUCH OF THE GULF OF CALIFORNIA ENHANCED BY A BACK-DOOR TYPE COLD 
FRONT AND STRONG HIGH PRES OVER THE GREAT BASIN. WINDS WILL 
SLACKEN OVER THE NEXT 24 HOURS AS THE WEATHER FEATURES SHIFT E. 
HOWEVER...SW WINDS WILL INCREASE MON NIGHT AHEAD OF AN 
APPROACHING COLD FRONT. A MARGINAL EVENT IS OCCURRING IN THE 
GULF OF PAPAGAYO...ALSO ENHANCED BY STRONG NE TRADES IN THE W 
CARIBBEAN. THIS EVENT IS EXPECTED TO DIMINISH LATER THIS EVENING 
BUT THEN RETURN AND PERHAPS INCREASE TO 20-25 KT MON AND TUE. N 
WINDS ARE EXPECTED TO INCREASE TO 20-25 KT IN THE GULF OF 
TEHUANTEPEC TOMORROW MORNING AS A COLD FRONT SURGES S OVER THE 
BAY OF CAMPECHE. HOWEVER...CONDITIONS WILL IMPROVE MON NIGHT AND 
TUE AS THE FRONT IN THE GULF OF MEXICO LIFTS BACK N AS A WARM 
FRONT. 

$$
FORMOSA