A Near "Bomb" Cyclone Approaches the West Coast

 Last weekend, I started getting emails from folks concerned about a "bomb cyclone" approaching Washington state.    Some of the amateur Facebook and YouTube sites were also starting to beat the weather drums.

The reason?  Several model runs at that time had scary forecasts, such as this one for 4 PM Thursday (tomorrow).  The kind of strong low that would easily take out power to hundreds of thousands of local customers.

When I took a look at the situation, I realized the uncertainty of these forecasts was very, very large:  the ensembles of many forecasts have a huge spread in solutions, and the forecasts changed radically run to run.

That is why I did not blog about it.  

We are close enough now to have a good idea of what will occur tomorrow... the rapid development of a strong low off the California coast. 

A low center that will dissipate almost as quickly as it developed.

Here is the pressure analysis for 4 AM this morning.  An amorphous 1002 hPa low-pressure center off of northern California.  Yawn.

Now look at the forecast for 4 AM Thursday morning:  a 986 hPa low has formed.  Impressive.

A deepening of 16 hPa in 24 h.   Not quite the bomb rate (24 hPa in 24 h), but very substantial.

The developing low was quite evident on the visible satellite image this afternoon (see below, and I marked the low-pressure center).

The water vapor satellite imager tonight (8:30 PM) was quite impressive:

By 10 AM on Friday, the low will weaken to 1001 hPa and drift nearly due south.

This storm is predicted to drive some large waves offshore (see wave forecast for 4 PM Thursday), with some getting to 25 feet, and some modest waves reaching the coast.  No big deal.

Here in Washington State, we will get little wind from the low center.  However, it will push a plume of moisture into our region (yes, an atmospheric river) that will provide more welcome rain (see forecast of the water vapor transport below).

The forecast totals through Sunday at 4 AM are impressive in the mountains:

Potential for a Major Aurora Tonight

 There has been a significant solar storm, and particles have reached the Earth's orbit.

Several individuals in the Pacific Northwest have already seen auroral displays, such as my colleagues at the National Weather Service forecast office at Sand Point (see below)

The critical Kp index is now 8.5 (see below), which is normally a guarantee of a decent aurora for our region--if there are no clouds.

In fact, the NOAA Space Weather Center's Aurora forecast brings the  aurora action into Washington State (see below).

But this is a problem....clouds.   

 As shown by the latest satellite image, a substantial band (red arrow) is moving north from Oregon.   A broken band is moving into western Washington now (purple arrow), but may clear the central Sound between 9 and 10 PM.  Eastern Washington is good right now...bet some of you are seeing it.

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