I have never watched Game of Thrones, but I’m going to go ahead and assume it’s about what’s going on out American West right now.
In the past 48 hours, the region has swung through a series of record-setting weather extremes. The U.S. West Coast is a fiery mess as toxic smoke blankets California and Oregon. But residents of the interior parts of the West from Wyoming to Colorado are waking up to record-setting cold and snow, as well as some areas still on fire from this weekend’s heat onslaught.
The source of the multifaceted misery is a huge whip in the jet stream, which we’ll get into more in a bit. But the real shock is what’s happening on the ground. In brief, the West had itself a weekend with unprecedented heat across every square inch of the region. We’re talking all-time records in California, where temperatures reached 49.4 degrees Celsius in Chino, located roughly 56 km east of Los Angeles. That’s an all-time record west of the San Bernardino Mountains. Even areas normally insulated from heat along the coast reached blistering new heights; San Luis Obispo, for example, cracked 48.9 degrees Celsius. The heat shows how even the seemingly minor boost in the global average temperature driven by the climate crisis can play out in regional extremes.
Heat provided the backdrop for fires, which exploded across California. The Creek Fire is the largest out-of-control fire in the state, raging over 54,600 hectares. The blaze spurred one of two unprecedented helicopter evacuations of people trapped by flames at Mammoth Pools Reservoirs. The image below gives you a sense of the scale of the evacuation and the reality that the Creek Fire sprung up so quickly, leaving more than 200 people stranded.
Simply extraordinary, lifesaving work by the @CalGuard airlifting more than 200 people to safety overnight from the imminent danger of the #CreekFire The National Guard stands Always Ready, Always There to support our communities and nation in times of need. pic.twitter.com/MybDKESipJ
— General Daniel Hokanson (@ChiefNGB) September 6, 2020
Flames also lapped up huge swaths of land in Washington, engulfing 80 per cent of a town in the eastern part of the state. An estimated 121,400 hectares burned in the span of a day as winds stirred up some of the most extreme fire behaviour imaginable. I mean seriously, look at the black streak in eastern Washington on this satellite loop:
Rapid growth of wildfires (black hot spots) as seen on shortwave IR. In the last frame or two it looks like a new fire has appeared west of the Cascades in Oregon, which is very concerning. pic.twitter.com/ue9p4g32h3
— Joe Zagrodnik (@joejoezz) September 8, 2020
And in Colorado, record heat helped the Cameron Peak Fire double to 24,200 hectares in a day. But things shifted gears in Colorado overnight on Monday into Tuesday. Temperatures plummeted from record highs in the 48s to lows in the teens as Arctic air plunged into the region.
Record-setting snowfall followed there and across other parts of the Mountain West and Northern Plains. Lead, North Dakota, has picked up a record 25.4 centimetres of snow already, and 45-60 centimetres of snow have fallen in Wyoming’s Wind River Mountains, according to National Weather Service data. More than a foot of snow is expected in the Colorado foothills outside Denver and Boulder alone as the storm drops into the area.
While there is cold and snow and surely people will pull out “durrr, where’s your global warming now” line, it’s important to keep things in perspective. In the past seven days alone, there have been 345 monthly heat record set, according to federal data. There have been zero cold ones.
So, what’s the cause of all this? The jet stream. The rushing river of air circles the globe, keeping colder air locked to the north and warmer air locked to the south. It kept its arse parked to the north this weekend, allowing hot conditions to bake the West. But on Sunday, it took a sharp dip over the Mountain West, which is bringing snow to the area.
The source for the dip is a disturbance thousands of miles away. Back-to-back typhoons hit South Korea, bringing misery there. But as those storms swung north into the jet stream, they essentially acted like a person cracking a giant, globe-sized whip. (Is there a Game of Thrones reference here? Does John Snow have a whip? Someone should have a whip.) That first typhoon to crack the whip of the jet stream sent a ripple that caused the jet stream to lift and bring the hot weather that blanketed the region. The second crack caused the jet stream to dip wildly over the Mountain West, bringing the snow.
The weather, maannn. It’s all connected.
Unfortunately, that connectedness also spells more trouble for California. The low pressure over the Rockies has trapped high pressure over the Great Basin of Nevada. The high pressure there is a classic set up for Santa Ana and Diablo winds racing from east to west over the state. Red flag warnings are in place as the National Weather Service calls for winds of up to 88 km/h and continued, relentless heat. That will fan the fires already burning and could spread new ones should they ignite.