Thursday, April 6, 2017

An Extraordinary Storm Approaches

It is probably the most powerful April storm to approach the Northwest coast during the past half century.  A very large, well-formed oceanic cyclone that will cross Vancouver Island Friday evening.  And one that will surely bring power outages to the coast and parts of the interior.

Let's start by looking at the 9 PM infrared satellite image (below).  Beautiful storm with the low center in the middle of the swirl nearly due west of the Oregon/CA border.


Another way to view the storm is using the water vapor channel that uses wavelengths in which water vapor emits radiation effectively. The dark area indicates dry air aloft descending towards the low center--the mark of a rapidly intensifying storm.  The massive cloud shield is also classic for a powerful, rapidly intensifying cyclone.


We have a few buoys offshore to see what is happening.  Buoy 46002, off the Oregon coast (see map) is experiencing huge pressure falls (see plot).  A 25 hPa drop in 6 hr!   Wow.




The latest model forecasts are in and the forecasts are impressive. And I should note that virtually all modeling systems are providing a similar solution.  Thus confidence is high.

At 2 AM Friday, a 976 hPa low center is off the southern Oregon, with an intense pressure gradient to its south and west.  Classic for marine cyclones.

 By 11 AM the low is off the Washington coast, with an extraordinarily intense pressure gradient (and thus strong winds) over the Oregon coast.

 At 8 PM Friday, the low center is making landfall on central Vancouver Island, with the intense pressure differences (and thus winds) over the Washington coast.


The wind speed forecasts will impress.  Here are the gust predictions.
At 5 AM, the central and southern Oregon coasts are getting hammered with gusts to 60-70 mph.

By 2 PM, the strong winds have reached the southern WA coast.
 And the northern coast at 8 PM.

 Winds will pick up during the late morning over the western WA interior.  Here is the forecast gusts for 2 PM.  Seattle is rocking with local gusts to 40-50 mph in exposed locations.   The coast is another world (and much windier).


The NOAA/NWS HRRR model for the same time (2 PM) shows some startling winds, with gusts to 50-60 mph in some places.  These are serious winds, folks...perhaps the strongest of the winter at some locations.

 The National Weather Service has a high wind watch out for the western WA interior for tomorrow.

There will be substantial power outages along the coast with downed trees and associated damage. Some power outages should be expected in the interior.

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10 comments:

clive boulton said...

Winds over 50 mph, gonna need my chainsaw.

LadyHawke said...

We just lost power in West Olympia, the winds are really gusting here. The low must be right off the coast near Grays Harbor which bring us wind as it rushes through the Chehalis gap.

John Marshall said...

Hopefully, this will be strong enough to bring some rain to Sequim. My yard was drying out given we missed most of the March wet stuff. This has been a very good late winter and spring for the rainshadow effect. Good in a bad way when it comes to my yard.

I was started to mess around with my shrub and tree irrigation gear, figuring out what needs repair. I sure don't want to use it this early, but we've had only 3.5" since the first of the year, and most of that was two months ago.

Nothing is in bloom or leaf yet at my elevation, so no worries on wind. Definitely a cold winter. I figure if the winter storms haven't already pruned it, it'll stand.

iamlucky13 said...

It could be a fun day to hang out at Cape Disappointment or similar locations on the coast and watch the waves pound the cliffs.

Oh...right...work. Maybe I should get back to that so I can get my work done before the power goes out, if it does.

texasjen said...

Thanks for keeping us in the loop Cliff! My warm-weather visitors (CA and TX) for this weekend are "excited" for this weather.

Wes Stanton said...

Out of curiosity, looking at image 11, the 2pm western WA wind gust map: Why are the highest Puget Sound gusts forecast precisely for Tacoma & Seattle? Did we build in the windiest spots? Does urban architecture get figured into the forecast models? Is it a function of the density of wind measurement sites?

Roger Thompson said...

Crossing the Tacoma Narrows Bridge was intense today!

PrairieGirl said...

Torrential rains hitting the hillsides are likely to cause mud slides as well. Additional tree/large limb loss. Yes, keep those chainsaws ready...
( just a thought-c
could tons of additional pressure on fault lines, due to massive rain falls and the water weight, possibly have an effect on plate shifting? )

twistjusty said...

Who's coming east from Pacific Ocean?
Ripping up roots of 50-ft trees?
Who's bending down to give us some lawn chairs?
Everyone knows it's Windy

Steven Grise said...

...and Windy has stormy eyes,
lookin' windward makes us cry.
everyone knows,
when the wind blows...
for Chrissakes...
It's windy.