A Surprisingly Strong Springtime Storm

Hi everybody, I’m back after a brief break from blogging! I’ve been working like mad on finding out how to automatically upload some of the model charts I’ve created to the internet, and I broke new ground today and finally did it! This means that now, you’ll be able to view some of the latest model data on WeatherTogether. Granted, the collection of charts I have right now is rather miniscule, and it will likely stay that way for the forseeable future, since the scripts that make these charts are computationally expensive and there currently aren’t any supercomputers on the Portland Craigslist. But it’s a good start, and hopefully the beginning of a new chapter for WeatherTogether. You can find the models here.

An unseasonably large storm off the West Coast on April 6, 2017
An unseasonably large storm off the West Coast on April 6, 2017. This storm will bring gusty winds to the Pacific Northwest on Friday.
Image taken by NASA’s TERRA Satellite

As some of you may have heard, we have a large low pressure system heading into our area as we speak, and it should deliver very high winds and waves to the coast, with some of these strong winds making it into the Western Washington and Oregon lowlands. The beautiful shot above was taken this afternoon by TERRA, one of NASA’s polar-orbiting satellites. Let’s take a look at what this beast looks like right now.

Water vapor satellite imagery showing the storm at 9:30 pm 4/6/2017
Water vapor satellite imagery showing the storm at 9:30 pm 4/6/2017
Credit: University of Washington Atmospheric Sciences

There are a couple things that stand out about this storm in the satellite picture above. First and foremost, this is a big storm. Even though it is not predicted to be as deep as the Ides of October Storm that failed to live up to expectations, it is much wider. The Ides of October storm was extremely compact, and tiny differences in track led to huge differences in wind speed. The broader nature of this storm ensures that maximum winds will be less, but that strong winds will be spread over a much larger area, and that tiny differences in track have much less of an effect on wind speed. Confidence is very high that we will get unseasonably windy tomorrow.

This storm is currently off the Southern Oregon Coast at approximately 980 hPa. As the following frames from tonight’s UW WRF-GFS show, it should curve northward and weaken as the day goes on, with 25-35 mph sustained winds (gusts to 55) impacting the Portland area between 9 am and 1 pm and the Seattle area from 3 pm to 7 pm.

925 hPa Temperature, Sea-level-pressure, and 10-meter wind at 11:00 pm PDT, Thu 06 Apr 2017 – 6hr Fcst
Valid 05:00 am PDT, Fri 07 Apr 2017 – 12hr Fcst
Valid 11:00 am PDT, Fri 07 Apr 2017 – 18hr Fcst. Portland should be experiencing its strongest winds around this time.
Valid 05:00 pm PDT, Fri 07 Apr 2017 – 24hr Fcst. Seattle should be experiencing its strongest winds around this time.

The coast will see much higher winds, with the highest winds ahead of the strong cold front associated with this system. Though the Washington Coast will see high winds as well, the Oregon Coast will bear the brunt of this storm. It’s not often that we see whites (>50 knot sustained winds) on these maps!

10 meter wind and sea-level pressure at 02:00 pm PDT, Fri 07 Apr 2017 – 21hr Fcst

These strong winds will generate very high surf of up to 8 meters (26 feet) along the Oregon Coast. It should be a great time to go storm watching. If you do this, please exercise caution.

Significant Wave Height (height of highest 1/3 of waves) at 5 pm Friday 4/6/2017
Credit: NOAA Wavewatch

On a final and serious note, please stay away from trees during the wind. Our trees have shallow roots and our soils are still relatively saturated from all the wet weather we’ve had this spring. Winds will be strong enough to break large branches and even topple exposed or diseased trees, particularly on the coast. There have been too many tragic deaths from windstorms over the past few years due to falling trees.

Enjoy the storm, and be careful!
Charlie

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