June 09, 2024

Lightning Returns to the Pacific Northwest

 Lots of thunderstorms, some approaching severe levels, have hit eastern Oregon and Washington during the past day.....and there are severe thunderstorm warnings out between Wenatchee and Spokane as I write this blog (see below).


The latest radar image over eastern Washington shows strong storm cells, with the red colors indicating substantial radar reflectivity.   Such high levels are either very heavy rain or hail. 


Earlier today (around 3:30 PM) similarly strong storms were moving eastward across southeast Oregon (see below)


Precipitation during the past day has been substantial over southeastern Oregon (up to 1.23 inches) and northeast Washington has also experienced some of the thunderstorm showers (see below).


This is the first major lighting event of the year for our region.    Yesterday (Saturday), there was a substantial number of lightning strikes over eastern Oregon ( see below).


The latest lightning strike map (at 7:50 PM Sunday) shows plenty of lightning, with thunderstorm cells over eastern Washington and others over southeast Oregon.


And here is the total lightning strike picture for Sunday.  Southeast Oregon and downstream are well covered by lightning, with quite a few over NE Washington.



So why so much lightning?

Today an upper-level trough moved through, as shown by the weather map at roughly 18,000 ft (500 hPa) this morning at 8 AM (the red dashed line shows the trough line).   In front (east) of the trough, there is both upward motion and the movement of warm, moist air from the south, both very favorable for generating thunderstorms.   


The atmosphere over eastern Washington and Oregon had lots of CAPE (Convective Available Potential Energy)... think of this as fuel for thunderstorms.  

To illustrate,  here is the CAPE prediction for 8 PM tonight (Sunday).  Some values getting as high at 600 (J/kg).  Decent for around here, a big yawn for those in the Midwest.


All our local thunderstorm action will be over over night as the trough moves inland and cooler marine air moves into the region.



6 comments:

  1. Hi Cliff,

    Could you expand on CAPE and how it works? I have considered the energy release in a thunderstorm to be based on the delta T of the two fronts similar to a heat engine. High temperature differential, higher energy release potential. Is this an accurate way to look at it?

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    Replies
    1. You would think so. In the SE the delta T is maybe 10 degrees where the air moves from the sea (about 80-85 degrees.) to the land (about 10 degrees warmer). Here in the NW the sea is only 55 degrees or so, but the land on a typical summer day is around 75 degrees: Delta T= 20. Sounds like more CAPE, right? But the classic marine push (like we just had) typically brings only a temperature drop and low clouds. Seems like the warming of the air mass from the bottom ought to give us enough instability to create thunderstorms, but... nothing happens...

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  2. Start with the NWS glossary, and go on from there.
    https://forecast.weather.gov/glossary.php

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  3. But, as usual, we in the West side get left out (sigh).

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  4. I know!...As a life-long (now77) person living in the Puget sound area, I only have a few memories of experiencing any sustained thunder/lightning episodes!...We seem to only get a couple of thunderclaps, maybe a few times a year. I do remember a 24 hour, hectic episode of humidity, coupled with relentless lightning strikes, sometime back in the 1990s, but cannot remember the general time frame of that freaky situation!. I remember having to drive to work, over 35 miles, and wondering if, or when, my car would be hit by lightning, as flashes were happening every 10 seconds or so! Maybe someone posting here can be more specific about that event? I think it had to do with an usually sustained "Pineapple Express" pounding Seattle.

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  5. Lightning is fascinating; I "get" that kind of positive-negative discharge energy transfer (between clouds, and [literally] to ground). What's I've never quite understood is the mechanics of THUNDER - how lightning and thunder relate. Sometimes it seems that lightning can be silent, visible 'bopping' in the clouds but without sound or a 'thunderclap.' Other times, there are long, rolling "reports" and "rumbles". It would be fascinating to know more about the mechanics of these two phenomena.

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