000
AXPZ20 KNHC 150337
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED OCT 15 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.

...TROPICAL WAVES...
AN ILL-DEFINED TROPICAL WAVE LIES ALONG 100W FROM 8N TO 16N. 
COMPUTER MODEL GUIDANCE DEPICTS WEAK LOW LEVEL CIRCULATION ALONG 
AND UPSTREAM OF THE WAVE. STABLE CONDITIONS UNDER AN UPPER RIDGE 
TO THE N OF THE RIDGE ARE INHIBITING CONVECTION NEAR WAVE N OF 
11N...THOUGH ISOLATED MODERATE CONVECTION IS OCCURRING WITHIN 
120 NM EITHER SIDE OF WAVE AXIS S OF 11N...POTENTIALLY FROM 
LOW-LEVEL CONVERGENCE WITHIN ITCZ.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 08N77W TO 10N93W TO 08N113W TO 
10N123W TO 08N140W. SCATTERED MODERATE CONVECTION WITHIN 120 NM 
EITHER SIDE OF AXIS BETWEEN 80W AND 87W. SCATTERED MODERATE 
CONVECTION WITHIN 180 NM S OF AXIS BETWEEN 92W AND 104W. 
ISOLATED MODERATE CONVECTION WITHIN 90 NM S OF AXIS BETWEEN 119W 
AND 123W. ISOLATED MODERATE CONVECTION WITHIN 90 NM EITHER SIDE 
OF AXIS BETWEEN 132W AND 140W.

...DISCUSSION...
SUBTROPICAL RIDGE EXTENDS S FROM A 1031 MB SURFACE HIGH CENTERED 
NEAR 40N137W TO NEAR 16N141W. ANTICYCLONIC SURFACE FLOW AROUND 
THIS HIGH IS BRINGING W TO NW WINDS OVER NW PORTIONS OF THE 
DISCUSSION AREA...WITH A TIGHTER PRESSURE GRADIENT CLOSER TO THE 
SURFACE HIGH SUPPORTING SURFACE WINDS AROUND 20 KT FROM 14N TO 
24N W OF 130W. THESE WINDS WILL DECREASE OVER THE NEXT DAY OR SO 
AS THE PRESSURE GRADIENT SLACKENS. HOWEVER...A WEAK COLD FRONT 
WILL APPROACH THE WESTERN CONUS COAST LATE THURSDAY...WITH 
SURFACE PRESSURE RISES BEHIND THE FRONT CAUSING AN INCREASE 
IN NORTHERLY WINDS ONCE AGAIN OVER NE PORTIONS OF THE AREA. 
ACROSS THE REMAINDER OF THE AREA AT PRESENT...8 TO 10 FT SEAS 
CONTINUE TO PREVAIL OVER AREAS SW OF A LINE FROM 30N120W TO 
00N86W ACCORDING TO A RECENT JASON PASS. HOWEVER...AS THE LARGE- 
SCALE PRESSURE GRADIENT DECREASES OVER THE REGION...WEAKER 
SURFACE WIND FORCING WILL ALLOW FOR THESE SEAS TO DROP BELOW 8 
FT OVER MOST AREAS. 

OF CONCERN IS A GAP WIND EVENT OVER THE GULF OF TEHUANTEPEC. AS 
A SURFACE RIDGE BUILDS BEHIND A LOW-LEVEL THERMAL BOUNDARY OVER 
CENTRAL MEXICO...AND A BROAD SURFACE PRESSURE TROUGH PERSISTS SW 
OF THE GULF...NW TO N SURFACE WINDS HAVE DEVELOPED OVER THE 
GULF...CONFIRMED BY DATA FROM A RECENT QUIKSCAT PASS. THESE 
WINDS ARE BEING FURTHER ENHANCED BY LOWER PRESSURE IN 
ASSOCIATION WITH TROPICAL DEPRESSION 16 IN THE W CARIBBEAN. AS 
SURFACE PRESSURES S OF THE GULF INCREASE THROUGH WEDNESDAY 
...WINDS WILL SLACKEN SOMEWHAT BUT WILL INCREASE ONCE AGAIN BY 
THURSDAY AS AN EVEN STRONGER RIDGE BUILDS S INTO CENTRAL AND S 
MEXICO. 

ALSO...STRONG NW SURFACE WINDS OF 20 TO 30 KT IN THE GULF OF 
CALIFORNIA CONTINUE IN THE WAKE OF A SURFACE FRONT THAT HAS 
PUSHED INTO NORTHERN MEXICO. AS PRESSURE RISES BEHIND THE FRONT 
DIMINISH DURING THE NEXT 12 HOURS...THESE WINDS SHOULD GRADUALLY 
DIMINISH...THOUGH SEAS OF UP TO 8 FT COULD PERSIST THROUGH 
TONIGHT.

FINALLY...A 1011 MB SURFACE LOW IS CENTERED NEAR 11N125W WITH 
ISOLATED MODERATE CONVECTION WITHIN 360 NM OF THE LOW CENTER. 
THIS LOW IS EXPECTED TO DRIFT TO THE SW OVER THE NEXT DAY...WITH 
STABLE CONDITIONS EXPECTED TO CONTINUE TO LIMIT CONVECTIVE 
DEVELOPMENT WITH THIS SYSTEM.

$$
COHEN/KIMBERLAIN