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North Pacific Marine Weather Discussion

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AGPN40 KWNM 181051 CCB
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
247 AM PDT Thu Apr 18 2019

.FORECAST DISCUSSION...Major features/winds/seas/significant 
.weather for the North Pacific N of 30N and E of 150W.

06Z surface analysis shows a warm front about to move N of the 
waters while a cold front enters the far NW waters, and high 
pressure remains W of the PZ6 waters with a ridge extending 
across the northern PZ6 waters and into the SE Oregon watrs. An 
ASCAT-A pass from 0535Z returned SE winds 20 to 25 kt in the far 
NE PZ5 waters associated with the warm front and another area of 
20 to 25 kt off the central and northern California coast, 
highest in the coastal waters near Cape Mendocino. Winds 
elsewhere across the offshore zones were observed at 5 to 15 
kts. 

A strong low well NW of the PZ5 waters is moving away from the 
waters with a cold front moving over the northern PZ5 waters 
while slowing as it stalls across the northern PZ5 waters today. 
The front will then push SE across the waters Thu night into Sat 
after a frontal wave cross the northern PZ5 waters later today 
into tonight. High pressure will build N and NE behind the front 
and inland into British Columbia while forcing a lee trough 
alkng the coast of Washington and Vancouver Island later Fri 
with NW winds picking up to 25 kt across the NE PZ5 waters. The 
coastal trough will strengthen further south along the 
California southern Oregon coasts on Saturday when model 
consensus has been calling for gradients to reach a maximum. 
Winds to 25 kts and as high as 30 kt are possible across the 
inner PZ6 zones and these conditions should persist into Monday 
with broad high pressure settling in through the end of the 
period. Further north a pair of lows will pass in close 
succession to the northwest of the PZ5 waters with the first 
passing NW near the region on Mon and the second on Tue. Each 
passing low will bring a period of winds increasing to 10 to 20 
kts across the northern PZ5 waters. High pressure will build 
west of the PZ5 waters on Wed with northerly winds of 10 to 20 
kts expected across much of the PZ5 and northern PZ6 waters.

00Z model guidance was in good agreement with no major cyclones 
expected to affect the offshore zones through the forecast 
period. There was particularly good agreement through 00Z Sat 
when the 00Z GFS is preferred. After that opted to continue 
using the most consistent ECMWF through Sun night. Some minor 
differences are noted with the pair of lows passing northwest of 
the region on Monday and Tuesday. The new 00Z ECMWF has a more 
robust shortwave moving into the Gulf of Alaska and an 
associated deeper second surface low versus its previous run 
with UKMET similar while GFS is weaker and more like the old 
ECMWF, and the 00Z Canadian becomes out of sync by Tue. The 
first low on Tue is weakening as it passes NW of the area and 
betetr handled by models. The best consensus is with using an 
even blend 00Z GFS/ECMWF solution Mon and Mon night and then 
using the old 17/12Z ECMWF in the blend after that. No solution 
shows the potential for hazardous wind and waves. 

.SEAS...
The 00Z Wavewatch and 00Z ECMWF WAM intialize within a foot or 
so of 06Z observations and sea state analysis. Through Fri with 
differences small used an even blend of the 00Z Guidance. After 
that choice of wave model or blend is reflected in the aoce 
choice of model or model blend for winds.

.EXTRATROPICAL STORM SURGE GUIDANCE...NA

.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
     None.

.PZ6 California Waters...
     None.

$$

.Forecaster Bancroft. Ocean Prediction Center.