The all time record temperature for Portland, Oregon has been broken along with records up and down Oregon’s Willamette Valley with Portland’s PDX airport reaching 112ºF. Record heat is expected again tomorrow in many areas of the Pacific northwest including Seattle as a powerful heat dome, far north of where it should be, drives winds down the slopes of the Cascades towards the Pacific ocean. This is the kind of weather that might be seen in California’s San Fernando valley in September when Santa Ana winds blow through the mountain passes. Today, the Colombia river valley has been feeling the desert heat blowing from the interior desert towards the coast.



What has happened to cause this extraordinary heat? With the end of the latest cool episode of La Niña in the equatorial Pacific waters a blob of high ocean heat content has reappeared offshore of the Pacific Northwest.  This heat blob may have helped amplify a wave in the atmosphere associated  with a storm located between Hawaii and the Aleutian Islands. Normally there is a heat dome in late June over the four corners region of the southwest. The wave amplification has put the center of this heat dome over the province of Vancouver, Canada  with winds flowing east to west over Oregon and Washington, allowing a surge of tropical moisture into the southwest. It’s a very unusual, possibly unprecedented, weather pattern for late June.

Record heat dome over the Pacific northwest.
Record heat dome over the Pacific northwest 500mb map showing extreme wave pattern at 500mb

Much higher than normal sea surface temperatures have been measured by satellite thermal sensors over the waters where the extraordinary wave amplification took place that led to the heat dome forming over the Pacific Northwest.

A blob of much warmer than normal water has reappeared offshore of the Pacific northwest.
A blob of much warmer than normal water has reappeared offshore of the Pacific northwest.

Dr James Hansen has written about a heat imbalance between incoming and outgoing radiation. The difference between the incoming and outgoing amounts of energy go primarily into heating the oceans and secondarily into melting ice. A small fraction of the heat goes into warming the air. Land and ocean areas near the hot spots are places where extreme weather events are likely to happen.

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