Another Northwest Bomb Cyclone with Localized Strong Winds

 Don't tell the media folks, but another midlatitude cyclone will be "bombing" off our coast today, with some local impacts.

A reminder:  A bomb cyclone is a midlatitude cyclone that intensifies rapidly (the sea level pressure drops by roughly 24 hPa in 24 hr).  A hPa (hectopascal) is a unit of pressure 

The recent moisture channel satellite image of the storm is impressive, with the darkened area a potent sign of rapid intensification.

Let me show you the latest European Center sea level pressure forecast to illustrate the rapid development.  Earlier this morning (6 AM) the low center was only 1004 hPa.

By 1 PM, the central pressure drops 23 hPa to 981 hPa.  Wow

And by 9 PM tonight it has deepened to 961 hPa....another 20 hPa!

Impressive..... this is quite a bomb cyclone!

Fortunately for us, the bomb cyclone is quite far offshore.  Note the much higher pressure inland and the late pressure difference across the Cascades....that will be important.

As the storm approaches northern Vancouver Island the gusts around its southern portions will be extreme, reaching 60-80 mph (see map below at 1 AM Tuesday).

Many of you are wondering about winds and power outages, so let me provide you with the latest.   The greatest wind threat will be:

• Along the coast
• Over Northwest Washington
• The Cascade foothills

Let me show you the gusts forecasts at a few times (in knots)

At 4 PM, the strongest winds are along the coast associated with the cyclone.  Also strong easterly winds in the Strait.  Downslope easterly winds are developing on the lower western slopes of the Cascades...with the highest gusts around 40 kt.  The strong easterly winds are driven by a large pressure difference across the Cascades.

By 7 PM, the coast wind gusts are really starting to rev up (blue colors) and the easterly winds start pushing down the Cascade slopes towards Issaquah and Kent.  Nothing like November.

At 10 PM, wind strength will increase over NW Washington (gusts of 40-60 knots) and over the Cascade crest.

Here in Seattle, the Seattle WindWatch application suggests winds gusting to about 30 mph in the city (see below).  Not enough to provide many power outages.

There may well be a few power outages over the western foothills of the Cascades and just downwind (e.g., the windy Enumclaw to south Issquauh to Kent area), but nothing like the November storm.