The Storm Has Arrived

 The promised storm has begun.  Tens of thousands of customers have already lost power, mainly in the southern Puget Sound region at this point...and more will surely follow.

The composite weather radar image is extraordinary (see image around 7:40 PM below).  The low center was then along the central Washington coast.  We can only see this because of the Langley Hill radar near Hoquium (thanks, as always, to Senator Cantwell for helping to make that radar a reality).

A few hours earlier, the low center was also evident in visible satellite imagery (below).

As of 7 PM, winds have exceeded 70 mph on the coast and at Crystal Mountain, with and over 50 mph over the south Sound area (see below).

With low pressure along the coast and higher pressure inland, strong easterly winds from the east descended the western slopes of the Cascades, contributing to power outages from Issaquah and Black Diamond to Enumclaw and out to the Sound.

This has resulted in massive power outages in these locations (see Puget Sound Energy outage map at 7:30 PM)

In Seattle, only about 850 customers have lost power.  

The numbers increase greatly in the hours ahead.  

The latest UW/Seattle Windwatch prediction of maximum winds in Seattle suggests that winds will peak around midnight, as the low center passes to the north (see prediction below).    This early in the season, with lots of leaves on the trees and untested new growth, one can expect substantial power loss with such winds.

Showtime in 2-3 hours for central Puget Sound.  Time to make sure all my devices are charged up.

Potential for Power Outages Saturday Night/Sunday Morning

Local power companies should organize their supplies and ensure they are fully staffed starting around 6 PM tomorrow (Saturday).

If you live in western Washington, I would charge up your phones and other devices.

A significant blow is coming from a Pacific cyclone making landfall on southern Vancouver Island.

The first strong wind of the season, particularly in October, is always a problem.   There has been substantial growth over the spring/summer that has yet to be tested by strong winds.

Many trees still have leaves, which catch the wind better than the leafless situation later in the winter.

The University of Washington modeling system (WRF) predicts a 986 hPa low-pressure system west of the Washington coast at 10 AM Saturday (see below).   On this chart, the lines of isobars (lines of constant sea-level pressure) and the wind speeds (gusts, knots) are indicated by color shading.  Big pressure changes and strong winds (gusts to 60 kt) are south and west of the low center.

Classic for an ocean cyclone.

As the low moves into southwestern British Columbia, an intense pressure variation (gradient) will move into western Washington (see forecast for 11 PM Saturday night), which will produce strong winds over the region.

The strongest winds so far this autumn.

How strong?  In Seattle, the best way to find out is by going to the City of Seattle Windwatch website (below), which uses multiple weather models to visualize the strong winds over Seattle (below).

Late Saturday and early Sunday, the forecast gusts exceed 40 mph.  My rule of thumb is that early in the season, power outages start with 30 mph gusts and are certain with 40 mph gusts.

Over western Washington, the winds will come in two steps.  

Step one, around 11 PM, will have strong southerly winds (blue colors) from Everett southward (shown below).  

The second act, a few hours later, will have strong westerly (from the west) winds surging eastward in the Strait of Juan de Fuca, hitting NW Washington

Strong southerly winds will also push northward in eastern Washington (wind gusts over the entire state at 2 AM Sunday are shown below)

Puget Sound Energy, Seattle City Light, and other utilities should be ready.

I don't want to hype this event. It is not the Columbus Day storm by any means, but it will have impacts.

Finally, as the low moves past us, air temperatures will cool, and substantial snow is expected in the Cascades.    Snowfall totals through 5 PM Sunday are shown below

The good news in all this is that wildfire season is over in Washington, and our water resources are rapidly growing again. Large amounts of precipitation are being forecast for the next ten days over our region.

Serious storms....midlatitude cyclones...are now predicted