Saturday, January 16, 2010

Coastal Winds

The new high resolution forecasts (4km grid spacing, initialed 4 AM) are in and the potential for a significant coastal wind event remains. Here are two plots of sea level pressure and surface wind speed for 4PM, 10 PM, and 4 AM, starting on Sunday afternoon. A deep low center moves up the coast and sustained winds on the coast are 45-50 kts. Gusts could easily be 15-20 kts higher.

Some of you have noted the tendency for coastal acceleration..and this does occur--in fact I just finished a paper on coastal windstorms where I talk about this effect. The interaction of onshore flow with the coastal terrain produces the speed up.


The Portland NWS has now put up a storm watch for the Oregon coastal waters. From their statement:
A STORM WATCH IS ISSUED WHEN THE RISK OF STORM FORCE WINDS OF
48 TO 63 KNOTS HAS SIGNIFICANTLY INCREASED...BUT THE SPECIFIC
TIMING AND/OR LOCATION IS STILL UNCERTAIN. IT IS INTENDED TO
PROVIDE ADDITIONAL LEAD TIME FOR MARINERS WHO MAY WISH TO
CONSIDER ALTERING THEIR PLANS.

The 10 am run is just in and the story has not been changed.
Here is the sea level pressure and precip chart for Monday
morning. One low after another rotating around. And California
is going to get hit hard with precipitation...a classic for El
Ninos.



7 comments:

Josh said...

Cliff
Are you calling for a "significant event" or a general midlatitude blow?

Joseph Ratliff said...

A high wind watch is in effect for the coastal areas of WA...

Statement as of 3:10 PM PST on January 16, 2010

... High wind watch in effect from Sunday evening through Monday
morning...

The National Weather Service in Seattle has issued a high wind
watch that is in effect from Sunday evening through Monday
morning.

* Strong south winds are expected to develop Sunday night and may
reach as high as 40 to 50 mph sustained with gusts to 65 mph
particularly for the beaches.

* The strong winds are expected to develop along the central and
north coast before midnight Sunday night and spread into the
western Strait of Juan de Fuca area overnight.

* The strong winds should shift to southwest and ease before noon
on Monday.

For the inland SW WA, Wunderground says "Windy Monday..." :)

South 20 - 35mph changing to 10-20mph in the afternoon.

Must read blogs said...

Again I have to ask what does all this mean for SW washington (ie chehalis)?

Jim said...

I checked the forecast for Southern CA because I was planning to leave for St. Barbara Monday AM. Yikes It looks like they will be facing WORSE weather than our forecasted. I'm sticking around here instead. Surfers are drooling up and down the coast. They are looking at major potential for piers and homes being damaged and maybe 20" of precip. on the west slopes. Those deforested burned out areas will be a real mess.

Fleetwood said...

I am just curious why this wind event is restricted to the coast? What is it about these storms? Thanks

Christopher said...

When you say coastal winds, do you also include the NW interior in that? Or would you add that separately if that were likely to get the same wind event?

athos said...

What happened to all the rain that we were supposed to get today?