(KXAN) — A couple of weeks ago, the Desert Southwest was under a ridge of high pressure that caused a heat wave in places like Phoenix, Las Vegas and Salt Lake City where all-time record highs were broken or nearly broken.
While some records were broken, most of these areas were able to deal with this type of heat as these cities are built with air conditioning.
This weekend, this same ridge of high pressure has strengthened again, but this time the ridge is centered over the Pacific Northwest, an area that is highly influenced by the California ocean current. This ocean current runs from north to south down the West Coast from Alaska all the way down to the Baja California. Even though it’s an ocean current, it also cools the air above and is why the West Coast has a “natural” air condition almost year round.
This natural air conditioner is why cities on the West Coast, and specifically in the Pacific Northwest, build their cities and homes without air conditioning as a high importance.
And now this region is experiencing a heat wave that even us Central Texans would find difficult to endure.
Cities like Seattle and Portland have seen highs in the triple digits since Saturday. Portland shattered their record high for June 27th. The temperature? 112°F. The record? 98°F set back in 2000.
This high of 112°F on Sunday broke the all-time hottest temperature ever recorded, which was set just the day before of 108°F. The hottest temperature ever recorded before Saturday was 102°F set back in 2006.
According to Climate Central, the city of Portland has seen an increase in temperatures over the past few decades. Since 1970, summers have warmed about 2.5°F, but since 1940 temperatures have increased over 4°F. The overall annual temperatures have warmed by about 3°F.
The persistent high pressure that has been dominating the West can be traced back to what’s called a “blocking pattern”. Typically the jet stream moves weather systems across the continent at a fairly consistent pace. Meaning, storm systems that bring rain can affect an area for about a day at a time before they move out and are replaced by a high pressure that brings fair weather, before yet another storm system moves in and brings unsettled weather.
Blocking patterns are just that, they block the progression of storm systems and cause a persistent weather pattern to form over the same areas. These blocking patterns arise when the jet stream becomes too “wavy”, which slows the east-to-west progression of storm systems. When the east-to-west progression of storms slows, it can then lead to persistent weather patterns to unfold. Whether it’s persistently hot and dry, or cool and unsettled, too much of any type of weather can spell disaster.
As the planet continues to warm, weather extremes are happening more and more, and blocking patterns could be one of the reasons why. Carbon Brief explains in detail why and how blocking patterns are a leading cause of climate change disasters around the world.