New study finds “nighttime heat waves” increasing in Pacific Northwest

July 24, 2013SEATTLE A new study has found that heat waves are increasing in the western portions of the Pacific Northwest, but not the kind most people envision, with scorching hot days of temperatures reaching triple digits. These heat waves occur at night. Researchers documented 15 examples of “nighttime heat waves” from 1901 through 2009 and 10 of those have occurred since 1990. Five of them took place during a four-year period from 2006-09. And since the study was accepted for publication in the Journal of Applied Meteorology and Climatology, another nighttime heat wave took place at the end of this June, the authors point out. “Most people are familiar with daytime heat waves, when the temperatures get into the 100s and stay there for a few days,” said Kathie Dello, deputy director of the Oregon Climate Service at Oregon State University and a co-author on the study. “A nighttime heat wave relates to how high the minimum temperature remains overnight. “Daytime events are usually influenced by down slope warming over the Cascade Mountains, while nighttime heat waves seem to be triggered by humidity,” said Dello, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “Elevated low-level moisture at night tends to trap the heat in.” In their study, Dello and co-authors Karin Bumbaco and Nicholas Bond from the University of Washington defined heat waves as three consecutive days of temperatures at the warmest 1 percentile over the past century. Using that standard criterion, they documented 13 examples of daytime heat waves during the time period from 1901 to 2009. Only two of those occurred in the last 20 years.
In contrast, nighttime heat waves have been clustered over the past two decades, with what appears to be accelerating frequency. A warming climate suggests the problem may worsen, studies suggest. “If you look at nighttime temperatures in Oregon and compared them to say the Midwest, people there would laugh at the concept of a Pacific Northwest heat wave,” Dello said. “However, people in the Midwest are acclimated to the heat while in the Northwest, they are not. People in other regions of the country may also be more likely to have air conditioning in their homes. On occasion, daytime and nighttime heat waves coincide, Dello said, as happened in 2009 when temperatures in the Pacific Northwest set all-time records in Washington (including 103 degrees at SeaTac), and temperatures in Oregon surpassed 105 degrees in Portland, Eugene, Corvallis and Medford. It was the second most-intense daytime heat wave in the last century, but lasted only three days by the 1 percentile definition. However, that same stretch of hot weather in 2009 results in a nighttime heat wave that extended eight days, by far the longest stretch since records were kept beginning in 1901. The latest nighttime heat wave began in late June of this year, and continued into early July, Dello said. “Like many nighttime heat waves, a large high-pressure ridge settled in over the Northwest, while at the same time, some monsoonal moisture was coming up from the Southwest,” she pointed out. “The high swept around and grabbed enough moisture to elevate the humidity and trap the warm air at night.” –Space Daily
This entry was posted in Climate unraveling, Earth Changes, Earth Watch, Extreme Weather Event, Heatwave, Potential Earthchange hotspot, Time - Event Acceleration, Unseasonable Weather Event. Bookmark the permalink.

3 Responses to New study finds “nighttime heat waves” increasing in Pacific Northwest

  1. Allison says:

    Hi. Maybe you can bring some notices from Brazil. Many cities are having cold records in the past couple days. It’s damn freezing here. Right now Sao Paulo has 7º degrees and cold will continue for one more week+.

    Like

  2. Lbisulca says:

    I don’t comment often but could all the geoengineering and solar management programs cause heat to be trapped? I believe these programs have alot to do with the changes in weather and are rarly talked about.

    Like

  3. Louie says:

    I live in southern Washington state and can confirm this. We used to always cool at night in the summer. Not near as much these days.

    Like

All comments are moderated. We reserve the right not to post any comment deemed defamatory, inappropriate, or spam.

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s