(Tundra Fires Near Hudson Bay in Northern Canada on June 29, 2013. Image source: Lance-Modis)

Today, as temperatures rocketed to above 120 in the US Desert Southwest, temperatures hit 87 degrees on the shore of the frozen waters of the Canadian Archipelago. These were the south to north markers of a heatwave that spanned 3,000 miles from Death Valley, California to Cambridge Bay in extreme northern Canada.

Beneath the southern section of this vast and sprawling heat dome, US communities coped by setting up cooling centers and issuing heat warnings. But despite this agile preparedness, hospitals in the hardest hit areas were flooded with cases of heat injury.

In one instance, an outdoor concert in Las Vegas saw more than 200 persons treated for heat injuries while more than 36 were hospitalized. Sadly, an elderly man also passed away at one local hospital after suffering from heat stroke. Temperatures reached an extraordinarily hot 115 (Fahrenheit) in Sin City.

Elsewhere, across the region, Palm Springs hit 122, Death Valley hit 125, and Phoenix hit a scorching 119. Tomorrow is expected to bring another day of extreme record heat, so area cities and residents are still under the gun.

Further north, near 90 degree temperatures stretched all the way to the frozen shores of Cambridge Bay in extreme northern Canada. There, some locations on the ice choked waterway experienced 87 degree temperatures, which is nearly 40 degrees (Fahrenheit) above average for this time of year.

The extreme heat sparked numerous tundra fires across Northern Canada, some of which you can see in the NASA satellite image above. Note the smoke tails rising from two clusters of fires in the upper center portion of the image. That ice speckled area of blue to the right is the, usually frigid, Hudson Bay.

The heat also set off melt and fracturing of sea ice in Cambridge Bay, which you can see in the NASA shot below:

(June 29 Ice Melt and Fracturing, Cambridge Bay. Image source: Lance-Modis)

Warming air temperatures typical for this region (high 40s to low 50s) usually result in a more gradual melt. But hot air temperatures at up to 55 degrees (Fahrenheit) above freezing tend to have a far more rapid effect. It is also worth noting the nearly complete lack of visible snow cover in this extreme northern region.

I’ve Never Seen A Rossby Wave Like This

The cause of this 3000 mile swath of heat is an extremely high amplitude wave in the Jet Stream that stretches from the Western US all the way up to the Arctic Ocean. This large bulge has allowed a powerful ‘heat dome’ high pressure system to build up beneath it, concentrating heat over the vast area affected.

(Image source: California Regional Weather Office)

Note the up-flow of Jet Stream winds rising up the coast of California, Oregon, Washington and British Columbia then lifting all the way up to the Arctic Ocean before diving back down through central Hudson Bay and into the US Midwest, before making another hairpin turn north again over the Appalachians.

Large Jet Stream waves of this kind are termed ‘Rossby Waves’ after the climate scientist who first identified them. They show extreme north-south and south-north elongation. In the time I’ve been tracking the extreme changes to the Northern Hemisphere Jet Stream brought about by human-caused warming, I’ve never seen a Rossby Wave quite so large as this. Nor have I seen one that is the result of so many large back and forth meanders. In fact, the entire Northern Hemisphere Jet is a mess of meanders, cut off upper level lows and blocking highs.

One of these upper level lows is expected to bring abnormally heavy rain with up to 3-5 inches for some parts of the US East Coast over the next couple of days. So as heat bakes a swath from Death Valley to the Arctic Ocean, the Eastern US braces for potential flooding. Similar Jet Stream loops and swirls spawned the European floods this June, a series of deadly floods that killed hundreds in India and Tibet, and multiple anomalous Arctic heatwaves occurring throughout the past month.

Extreme Jet Streams, like the one displayed above (for late Saturday, June 29), are far more likely to spawn extreme weather events than the usual, gently wavy Jet Stream that human civilization has been used to for much of the 20th Century and, probably, for most of the 10,000 year period since the last ice age. But a combination of eroding sea ice and record or near record low Northern Hemisphere snow cover contribute to both a slowing of the Jet Stream and in greater north-south and south-north flows. The result is large wave patterns in the Jet that tend to get stuck in the same configuration for long periods. Beneath the swells in the Jet, we get hotter temperatures, dryer conditions, and the risk of everything from extreme heatwaves to droughts and fires. In the dips, we get cooler temperatures and much, much stormier conditions resulting in a range of weather from extreme winters (Europe during winter/spring 2013), to floods (Europe summer 2013, India late June 2013), to record rainfall and powerful thunderstorms (US May-June 2013).

These are vivid examples of how human-caused climate change can result in extreme weather.

Heat Wave to Last For at Least a Week

The current record heat wave affecting both the US West and a large section of Canada is expected to last at least until the end of this week. Slow moderation, though, is expected for some regions after Sunday. However, the blocking pattern that spawned this particular heat wave shows little sign of changing position. So hotter, dryer conditions are expected to remain in place for the foreseeable future for much of the US South-West.

Meanwhile, Canada and regions along the Arctic coastline are still likely to see much warmer than usual conditions as periodic warm air invasions from the south are likely to continue.

Links:

Lance-Modis

California Regional Weather Office

Punishing Heat Hits Western US