000
AXPZ20 KNHC 221530
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON DEC 22 2008

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 06N78W 07N90W 08N105W 07N115W 
11N132W 08N140W. SCATTERED MODERATE CONVECTION IS WITHIN 150 NM 
N OF THE AXIS BETWEEN 96W-104W AND WITHIN 120 NM OF AXIS BETWEEN 
123W-134W.   

...DISCUSSION...
A REX BLOCK PATTERN REMAINS ESTABLISHED OVER MUCH OF THE 
DISCUSSION AREA...WITH A DEEP LAYERED CUT OFF LOW NEAR 
20N138.5W. AN ASSOCIATED INVERTED SURFACE TROUGH IS SITUATED 
JUST A FEW DEGREES TO THE E OF THIS DEEP LAYERED LOW...EXTENDING 
ALONG 134W FROM 10N-20N. LOW-LEVEL CONVERGENCE COMBINED WITH 
INSTABILITY AND DIFFLUENCE ALOFT IS MAINTAINING A LARGE ZONE OF 
SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 12N-24N 
BETWEEN 117W-136W. THE PRESSURE GRADIENT BETWEEN THE INVERTED 
SFC TROUGH AND A 1026 MB HIGH JUST NW OF THE AREA IS PRODUCING A 
SWATH OF 20-25 KT NE/E TRADES AND 10-13 FT COMBINED SEAS. THESE 
WINDS AND SEAS ARE EXPECTED TO SHIFT W AND GRADUALLY DIMINISH 
THROUGH THE MID-WEEK AS THE SFC TROUGH AND PARENT LOW SHIFT W. 

THE UPSTREAM TROUGH IN THE BLOCKING PATTERN IS OVER THE W COAST 
OF U.S. THIS FEATURE WILL SHIFT E WHILE A SHORT WAVE TROUGH 
DIVES INTO THE AREA OVER THE NEXT DAY OR TWO...REESTABLISHING 
THE UPPER TROUGH POSITION...PROVIDING SUPPORT FOR ANOTHER COLD 
FRONT ALONG THE N BORDER. WINDS AROUND 20-25 KT ARE EXPECTED 
NEAR THE FRONT...WITH SEAS BUILDING OVER 10 FT IN N SWELL.

GAP WINDS...
SEVERAL OF THE TYPICALLY WIND PRONE GAPS ARE ACTIVE TODAY. 
STRONG HIGH PRESSURE BUILDING E ACROSS THE CENTRAL U.S. BEHIND A 
GULF OF MEXICO COLD FRONT IS INDUCING STRONG N FLOW THROUGH THE 
TEHUANTEPEC. 1226Z QSCAT PASS SHOWED A BIT OF A SURPRISE IN 
REVEALING GALE FORCE WINDS NEAR THE N PORTION OF THE GAP. 
HOWEVER...WINDS SHOULD DIMINISH BELOW WARNING CRITERIA LATER 
TODAY OR TONIGHT AS THE FRONT STALLS OVER THE GULF...LIMITING 
THE FUNNELING EFFECT. MEANWHILE...RIDGING EXTENDING W BEHIND A 
STALLED FRONT OVER N MEXICO HAS INDUCED 20-25 KT NW TO N WIND 
FLOW THROUGH THE GULF OF CALIFORNIA...RAISING SEAS TO 6 FT OR SO 
ACROSS THE S HALF OF THE GULF. 

$$
CANGIALOSI