August 16, 2020

Extreme Heat Followed by Showers and Thunderstorms

Today was a day of amazing contrasts, with record high temperatures followed by thunderstorms and light rain.
Picture courtesy of NWS Seattle

A line on showers and thunderstorms moved through tonight... welcome relief from a record-breaking day of heat.  The models had been suggesting for days that a line of showers/thunderstorms would move up the east side of the Cascades, but with only a small chance of reaching the western lowlands.

The cause?  A weak upper level disturbance that helped release the instability inherent in the warm air present over the region (see map, the arrow indicates the disturbance).


The upward motion associated with the upper level feature was apparent in the high clouds that spread over western Washington this afternoon.  And the mid-level instability was suggested in some altocumulus clouds that began to form mid-afternoon (both apparent in the SpaceNeedle cam around 2 PM shown below



By 7 PM, the cloud mass associated with convection and thunderstorms was pretty impressive (see below).


And the radar image at 8 PM clearly indicated the showers and thunderstorms.



I saw a few lighting strikes myself and the lightning network provided further evidence.


The morning forecasts did not suggest too much moving into western Washington, but the 5 PM NOAA/NWS HRRR model forecast, the highest resolution modeling system run by the NWS was reasonably good (see forecast below for 9 PM).   My research group at the UW is working on more advanced lightning forecasting technology, combining state-of-science model output with machine learning, that should be able to do better.  This research is sponsored by Seattle City Light, which is concerned about lightning for obvious reasons.


Finally, just wanted to note the extraordinary high temperatures today, with several locations getting to 100F (see below, click toe expand).   Some significant records were broken today, with many daily records surpassed.  Thankfully, tomorrow should be about 10F cooler.

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14 comments:

  1. Only five days have been hotter in Seattle's 125 years of weather records:
    http://www.seattleweatherblog.com/wp-content/uploads/2013/01/Heat81.png?fbclid=IwAR3-O_Lek8wQdXQGdTCwdhhY1Wy2-b9eq5MlIjPSyYH_0OY0sroesxcd1yQ

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    1. Yeah...I grew up in Seattle...I can remember the first truly hot summer of my life, was in 1958...I was 11 years old...my dad checked out our outdoor thermometer, that was hanging from a small tree, in the shade...102!....but the official temp in Seattle was 99...we were a few blocks North of Green Lake..many years later (maybe in the 1990s?) my parents, still living in that North Green Lake home, hosted two visitors from Fort Worth Texas...they had come up to Seattle, to get away from the hot weather in Texas!...but Seattle that day, registered 100, and I think that was the first official 100 degree reading ever in Seattle...our friends from Fort Worth could not believe that my parents did not have central air conditioning!!lol...even now, many homes here do not have that.

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    2. What's more wild to me is we had a 90 degree day in April a couple years ago.

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  2. Lightning strikes across the San Juan islands around 9:00pm. Viewed from hilltop in Bellingham.

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    1. From San Juan Island, we saw lightning over the island and from South Beach we observed lightning south over the Olympic Peninsula. There were a few rain drops in Friday Harbor following the lightning. Todd Mitchell

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  3. Here in S. Everett the action was hit and miss...a couple lightning strikes off to the East, a very light sprinkling of raindrops from seemingly ominous cloud cover...I was looking forward to a bigger change!...oh, well...and it is still kinda muggy outside here at 11pm...probably have to keep my air conditioner running tonight!

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  4. Sadly, no lightning or anything but some ominous clouds down here in Pacific. Oh well. I'm enjoying the sun and heat while I can! <3

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  5. Lighning, thunder and a rain squall near Carnation around 8 pm.

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  6. For some reason the map shows Olympia only had a high of 88 ! We hit 100 in backyard but at the Olympia airport it recorded just 99.

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  7. The venerable ECMWF failed to forecast the entire event. Even the prior ECMWF runs showed no precip for western WA or western OR. The Sun mornings HRRR also missed the tstms. Only the sun morning NAM showed extreme instability west of the Cascades with a few tstms predicted over the mountains.

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  8. Take care, Cliff. Sorry to hear about your radio role. Cheers.

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  9. It reached 98.6 degrees at my house on the Bothell-Mill Creek line.

    To my surprise there was a mild thunderstorm last evening as I was barbecuing salmon at dusk. The temperature dropped from 85 to 80 degrees in just a few minutes, and the tree frogs came out. But there was only a little rain- though perhaps the warmest rain I have ever seen around here.

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  10. "The only thing necessary for evil to triumph is for good men to do nothing." - Edmund Burke. You're a good man, Cliff.

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  11. Here is an article about the reaction to your comments about Seattle:

    https://www.getreligion.org/getreligion/2020/8/16/npr-dumps-jewish-meteorologist-who-compares-seattle-to-kristallnacht

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Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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