A Near Perfect Forecast of Yesterday's Event. The Next Windstorm Comes into View

 The next time someone makes a weatherperson joke, remember the nearly perfect forecast for yesterday's wind event over Washington.

No longer appropriate

For days, the models correctly predicted the rapid development of the cyclone offshore and the high pressure inland. The combination resulted in strong easterly winds that descended the western slopes of the Washington Cascades.

You want to see how perfect the forecasts were?   Here is the wind speed forecasts provided to Seattle City Light from the UW's WindWatch website, which uses the best of the regional weather prediction models.

This graph shows the highest observed wind over Seattle (black line) and the forecasts made starting Monday afternoon.  

You don't get much better than that.  Earlier predictions were just as good.

A lot of attention was given to the strong cyclone/low-pressure system that developed offshore.   It was an impressive low that not only rapidly developed, but deepened to 943-943 hPa, slightly beating or equalling the historical record.

The 18-h forecast by the UW weather model, the GFS, was 943 hPa at 10 PM last night.  Very nice.

Not impressed?   The 72-hour forecast was almost identical.

Something has happened that has not been sufficiently understood by society.  

Weather prediction technology has improved immensely in skill and detail.

The above results are not a fluke.... I could show you a dozen more, including the predictions of devasting extreme events, such as the Lahaina wildfires or heavy precipitation from Hurricane Helene.

There is so much talk about extreme events and global warming.  

But the truth is that deaths and injuries from extreme events are declining rapidly because weather predictions are so good.  Such deaths and injuries could be greatly reduced further if governments and other institutions would better use highly skillful weather prediction.

The Upcoming Storm

Another midlatitude cyclone will be moving up the coast on Friday.   

On Friday morning at 10 AM, a 977 hPa low will be directly east of the Columbia River outlet.   Much weaker than yesterday's storm, but much closer.

By 7 PM Friday, the low will be making landfall on Vancouver Island as a 980 hPa low.

Compared to Wednesday, this storm will produce strong winds on the coast, but weaker winds over the western WA interior.

For example, at 1 PM Friday (below_, fearsome winds on the coast, but "only" gusts to around 25 kt  (roughly 30 mph) in the interior.

Here is the latest guidance for our friends at Seattle City Light or Seattle--not so bad.

The Storm Reveals Itself. The Eastside Wind Threat

The latest satellite image shows the rapid development of the offshore storm.

The visible satellite image around 9 AM was stunning, with low-level clouds swirling around the low center (the orange arrow points to the low center).

Stunning.

Here is the blow-up of the clouds around the low center.  The circulation is obvious.

Strong, rapidly developing storms not only have rising motion that produces clouds, but intense sinking motion that produces a "slot" dry air coming in from the southeast.   

We can view the "dry slot" using satellite images that reveal water vapor content in the upper and middle troposphere.  Such an image is shown below, with blue indicating very dry air.    This is a strong storm... no doubt about it.

The latest National Weather Service surface map (and I do have some issues with the quality of their analyses) shows the storm at 7 AM, with an analyzed lowest surface pressure of  974 hPa.   The storm is rapidly deepening today, so the pressure will fall considerably more.

As I mentioned in my previous blogs, although strong coastal winds are an issue, my biggest concern is for strong winds east of Puget Sound tonight.  

The models are still going for threatening winds....with the clear threat of substantial tree damage and power outages.

The latest European Center forecast predicts winds exceeding 70 mph on the east side of Puget Sound, particularly towards the western Cascade foothills.  These are all easterly and southeasterly winds....not the usual direction of strong local winds.

The NOAA/NWS HRRR model, run at high resolution, is similar but extends strong winds over Whidbey Island and the San Juans.

The UW Model is also threatening with strong winds on the eastside, gusting to 50 kts (around 57 mph) at 10 PM. 

The maximum wind over Seattle based on dozens of predictions is predicted to hit 45-60 mph...from the east (see below). 

Bottom line:  strong winds from the east, gusting to 40-70 mph, will occur east of Puget Sound and will be stronger towards the Cascades.  Expect substantial vegetation damage and many power outages.    Driving down streets with lots of trees might not be a good idea after 6-7 PM if you living in the vulnerable areas noted above.

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Addendum:

Here is the 1 PM satellite image...the circulation has become very, very obvious.

Some satellites can measure low-level winds by measuring wave action...called scatterometers.  Here are the surface winds from a scatterometer around the storm around 12:30 PM PST.    The intense circulation around the low is obvious.