Heat wave hits Pacific NW this week; A look at Climate Change Impacts on Extreme Heat

If you live in Western Washington and like roasting near 100 degree temperatures, you are and will be getting your wish the next 72 hrs. As powerful upper-atmospheric ridge of high pressure is establishing itself over the West Coast of the US, the combination of clear skies and subsiding (downward moving as opposed to upward rising) air under this high pressure system – subsiding air warms as it sinks – is leading to incredible heat over the interior areas of Western WA/OR and Northern CA.

GFSNW_sfc_temp_054
Forecast surface temperatures at 5 pm PDT Thursday. Upper-90s near Seattle around 100 in Southwest WA, mid-100s in the Willamette Valley and and Medford, OR area. Eastern WA also hit hard with high heat. (Global Forecast System 11 am PDT Tuesday model run).
gfs_namer_048_500_vort_ht
Forecast upper-air map showing the atmospheric wave pattern on the 500 millibar pressure surface (approximately 18,000-18,500 ft over the US) on 11 am Thursday. I added text to show the locations of the ridge relative to its influence on the “extreme heat” (where it is producing 20-25 degree above normal temperatures) over the Pacific Northwest. (Global Forecast System computer 11 am Tuesday model run).

Extreme heat warnings have been issued for virtually ALL OF Washington State, Western Oregon, and much of Northern California.

Shown below are the average high temperatures for today (August 1st) for selected cities in Western WA/OR followed by forecast highs for today-Thurs or Fri. The forecast highs in red are highs which would break the record high for that day.

Seattle, WA-

Tues, August 1st Average High Temperature: 77

Forecast Highs (Tues-Fri): 87, 94, 98, 95

Olympia, WA (state capitol)-

Tues, August 1st Average High Temperature: 79

Forecast Highs (Tues-Fri): 92, 98, 103, 95

Portland, OR-

Tues, August 1st Average High Temperature: 82

Forecast High (Tues-Thurs): 99, 105, 105 (All-time record high is 107 from 1965/1981)

Salem, OR (state Capitol)-

Tues, August 1st Average High Temperature: 84

Forecast High (Tues-Thurs): 99, 106, 105 (All-time record high is 108 from ’27, ’41, ’81)

According to the 5 pm PDT observation, Salem has reached 100 degrees, exceeding their forecast temp and tying the daily record of 100 degrees for today.

Eugene, OR-

Tues, August 1st Average High Temperature: 84

Forecast High (Tues-Thurs): 99, 106, 103 (All-time record high is 108 from ’81)

Medford, OR- (edited at 10:40 pm CDT Tuesday to add this city)

Tues, August 1st Average High Temperature: 93

Forecast High (Tues-Thurs): 108, 114, 111 (All-time record high is 115 from ’46)

It’s very possible that for a portion of the Willamette Valley, especially the Central Willamette Valley, Wednesday could be one of the most intense heat days on record!

The worst of the heat for Western WA and Western OR is expected to end after Friday more seasonable to reasonable above normal temperatures this weekend.


One of the most significant impacts of human-induced Global Climate Change are the impact on heat waves. As the average temperature of Earth warms, many local temperature patterns are shifting toward temperatures which are “hot” to “extremely hot” relative to average temperatures in the mid-20th century (typically defined by their standard deviation from the mean temperature for the local area).

18033307_10212742805792049_5293494484345621705_n
These charts, based on data by NASA climate scientist James Hansen shows the strong deviation in in the bell curve for 2005-2015 local Northern Hemisphere temperatures relative to the same distribution of temperatures in 1951-1980. The trend has been to many more “extremely hot” temperatures and “hot” temperatures have become the new normal in the Northern Hemisphere on average. See full NY Times story HERE

This shift has had implications for impacts on everything from drought to human health such as heat-related illness and vector-borne illnesses. It will continue to do so as carbon dioxide levels continue to climb. The levels of carbon dioxide in the atmosphere reached a record in observed human history of ~410 parts per million in May of this year, the highest level in at least several million years (and humanity is pumping it into the atmosphere at a rate unseen in the past 65 million years).

At this time, global warming has reached approximately 1 degree C (nearly 2 degrees F) since the early modern Industrial Era (the 1880s). It is statistically known that heat waves, droughts and also heavy precipitation events (because of additional moisture added to a warmer atmosphere) are being impacted directly by climate change.

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Author: Meteorologist Nick Humphrey

Meteorologist and geoscientist in Lincoln, NE. Seattle, WA native. Love weather, storm chasing/photography and planetary science.

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