Wednesday, 20 April 2016

Hothouse Summer expected on west coast US this summer

Hothouse Summer is Coming — Lingering California Drought, Record-Shattering Heat in Washington, and Thunderstorms Pounding the Northwest Territory in April



19 April, 2016

Writing about human-forced climate change isn’t easy. And, lately, year after year, I’ve grown to dread these three words more and more — Summer is Coming.

This year, it’s worse. The gateway of Equatorial-to-Polar heat transfer was thrown wide open as one of the strongest El Ninos on record blazed through the Pacific. 
As a result, Winter temperatures in the Arctic hit levels that were likely never seen by any human that has ever lived in a settlement resembling a town or a city. And one of the paths over which this heat ran was Western North America. A region that is now experiencing a number of early warning signs that trouble is on the way.
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What was perhaps the strongest El Nino on record is now fading in the Equatorial Pacific. It was an event that many hoped would provide significant relief to a drought-stricken California. An event that many hoped would crush a hot zone of Northeastern Pacific waters dubbed ‘The Blob’ — providing a new skein of cooler and far more familiar ocean surfaces. An event that many hoped would return at least some sense of normalcy to the US West Coast by restoring snow packs, reservoirs and flattening the Jet Stream while re-establishing a typical west-to-east storm progression.
Ridiculously Warm Sea Surfaces off US West Coast
(Ridiculously warm sea surfaces remain in place off the US West Coast. There, sea surface temperatures are in the range of 1-4 degrees Celsius above typical 1961 to 1990 readings. Such warm seas will tend to aid in ridge formation through Alaska and Western North America as Spring progresses into Summer. During recent years, a synergy has tended to develop between these abnormally warm waters, the warming and melting Beaufort Sea to the North, and the development of brutish, hot high pressure systems over the region. Image source: NOAA/NCEP.)

Unfortunately, many of these hopes have failed. The California drought remains firmly entrenched. Sea surface temperatures off the US and Canadian West Coasts remain abnormally high. And record-shattering heat and extreme weather is again settling in over Western North America during Spring. Though heavy rains and snows across Washington and Oregon during Winter have replenished higher elevation snowpacks there, an overall tendency for much warmer than normal conditions remains. And far to the north, the early break-up of Beaufort Sea Ice hints that any hopes for a return to flattened Jet Stream patterns may well be in vain.
This isn’t to say that the Summer of 2016 will be an exact mirror to that of 2015. More that newly established and climate change related trends promoting extreme warmth, southwest drought, Arctic wildfires, abnormal ocean heat and thunderstorms in the far north remain in place and are likely to have a continued and often disturbing impact this year. Perhaps even more-so after a recent Winter of record Arctic heat and a long period of abnormal warmth that has prepped a wide zone for potentially very severe warming-related weather in the months to come.
And already, it seems that weird Spring and Summer weather associated with a human forced warming is starting to settle in.

Freak Thunderstorms in the Northwest Territory

On Monday, extreme heat in the range of 15-35 degrees (Fahrenheit) above average settled in over much of Western North America. A strong upper level ridge of high pressure flexed its muscles over a broad swath stretching from California to the edge of the Arctic. All across Western Canada, unseasonably warm winds blew from south to north, carrying with them heat, moisture, and instability. Where the head of this roiling warm air mass collided with colder airs swirling over the Arctic Ocean — atmospheric sparks began to fly.
Residents of the Northwest Territory town of Yellowknife were amazed as an abnormal, early thunderstorm roared through the region — sparking off staggering displays of lightning and heavy downpours over the still-thawing lands. 

The storm emerged over the western edge of Great Slave Lake. It then rumbled past communities like Fort Providence, Kakisa, and Hay River, before finally thundering east over Yellowknife.

Yellowknife Thunderstorm on April 18 of 2016

It was an abnormal display that left many onlookers, including to city mayor stunned. “Um, there’s lightning. In Yellowknife. In April.” A flabbergasted Mark Heyck tweeted yesterday evening.

April thunderstorms are a more typical feature of the Great Plains of the US during this time of year. And it wasn’t until recently that human-forced global warming began to make these powerful storms a more frequent possibility for this near-Arctic region even during Summer. How unusual thunderstorms used to be for this region is driven home by the fact that tribes indigenous to the area didn’t even have a word in their language to describe them. For the early to middle spring period, it’s a 1 in 30 year event to see a thunderstorm over Yellowknife even when taking into context a very warm 20th Century. So back then it was basically a once or twice in a lifetime happening. But that was before a record global heating driven by fossil fuel burning settled into its warmest levels since the peak of the Eemian more than 115,000 years ago. Now, it’s pretty certain that such events will continue to become more common.

Never-Before Seen April Heat in Washington

About 700 miles to the south, Seattle, Washington experienced its highest-ever April temperatures in 122 years on Monday. There, readings rocketed to an extreme 89 degrees (Fahrenheit) as a powerful blocking high pressure system trapped a hot, stagnant air mass over the region pushing thermometers well above the 90 degree mark in many locations.

Yesterday’s Seattle high temperature reading was an amazing 31 degrees (F) above average for this time of year and a full 4 degrees (F) above the previous all-time record for the month of 85 degrees set on April 30th in 1976 — or nearly two weeks later in the season. Monday was also the second day in a row of above 80 degree temperatures. If today’s readings rise to their predicted values of 84 (F) then it will be the first time ever in April that there were three unbroken days of 80 degree or above in that Pacific Northwest City.

Above 90 Degree Temperatures in Northwest Washington
(Extraordinary spate of above 90 degree temperatures breaks out in Northwestern Washington yesterday. These are never-before seen readings for a region that typically experiences much cooler weather in the upper 50s (F) during this time of year. It’s unprecedented for April. Something that is an upshot of a severe and outlandish human forced warming that is resulting in more and more freak weather events cropping up around the globe. Image source: The National Weather Service and The Capital Weather Gang.)

The weird Seattle heat was accompanied by extraordinarily high temperatures running into the 90s throughout Puget Sound and over much of Northwestern Washington. Bellingham and Olympia experienced warmest ever April temperatures as well with thermometers hitting 83 and 88 (F) respectively. And in some locales, the proverbial mercury climbed to as high as 96 degrees (F) or about 39 degrees above typical April temperatures for the region.
To say such hottest-ever temperatures are disturbing would be an understatement. Though the region received strong rains and snows throughout Winter, record heat in this range will tend to push replenished mountain snows to rapidly melt and nearby forests to flash-dry. An area celebrating this year’s influx of moisture could thus soon find itself facing fire hazard and drought as Spring progresses into Summer.
Even a Strong El Nino Can’t Shake California from the Grips of Extreme Drought
Still further to the south, persisting and possibly worsening drought for the Spring and Summer of 2016 appears to be the likely conclusion. El Nino rains primarily funneled north into Oregon and Washington this year as very warm near coastal waters conspired with record low sea ice levels in the Arctic to pull the Jet Stream and related storm track northward. And though Northern California did receive some of El Nino’s snow pack and reservoir replenishing rains and snows, Central and Southern California have been left mostly bereft. And as a result, most of the state remains in the grips of extreme or exceptional drought — the worst levels we have a measure for.

Drought Monitor
(Conditions of extreme or exceptional drought still cover most of California. With ground water greatly depleted, snow packs below average, and reservoirs below average, a likely hotter than normal Summer followed by a predicted La Nina will tend to worsen drought conditions for the State and possibly for Arizona and New Mexico as well. A Strong El Nino was the best chance for California to receive drought-alleviating moisture. And it appears that opportunity has now passed. Image source: Climate Prediction Center.)

Despite strong water conservation policies set in place by the State during 2014 and tightening through 2015, reservoir levels are near normal in the North and well below normal in Central and Southern regions. Snowpack, which California relies on for water throughout the summer, is below average in all major regions, though rather higher than during 2014 and 2015.

Taking these measures into account, it appears that California received overall below average moisture amounts during the El Nino Winter of 2016 with normal levels of moisture falling on the northern 2/3 of the state and with the southern 1/3 receiving far less than normal precipitation over the past 90 days. As strong El Ninos typically bring above average amounts of precipitation to California, 2016 levels falling below even an average marker should be serious cause for concern. 

Closer to average, but still below average rains and snows, are nowhere near enough to bust what has been the worst drought in state history. More to the point, it appears that the current drought has settled in to a semi-permanent state with no end in sight entering its fourth year.

Southwest Drying
(The continuation of the California drought and the failure of a strong El Nino to deliver even normal levels of Winter moisture to the state are a part of an ongoing, climate change induced trend of western drying that has been growing in intensity since the 1980s. NCAR earlier this year found that California was losing, on average, about 6.5 percent of its pre-1980 average precipitation per decade. Image source: NCAR and Climate Progress.)

National Weather Forecasters at NOAA now predict an increasing likelihood of La Nina coming later this year. A moderately strong cool Kelvin Wave now rippling beneath the Pacific is beginning to surface in the Equatorial waters just to the west of Central and South America. If these cooler surface waters fan out along the path of the trade winds as predicted, it will likely be yet one more bit of bad news for California. La Nina, which may be in full swing by this Fall, tends to bring drier conditions to California. With the State’s groundwater still greatly depleted, with snowpacks still well below average, with reservoirs below average and with the State likely to face a warmer than typical Summer, this should be viewed by West Coast policy makers and residents alike as ominous news.


Conditions in Context — Severe Events Related to Human-Forced Warming Abound, Much Hotter Than Normal Summer Likely on the Way

Based on observations of overall trends, it appears that this Summer has been prepped for some obnoxiously extreme conditions. Never-before-seen Arctic Winter temperatures, record low sea ice, persistent pooling of hot water at the surface in the Northeastern Pacific, persistent development of strong ridges and record early season heatwaves over Western North America, the blocking of El Nino moisture from California by a northward shift of the storm track, the appearance of odd convective weather patterns like thunderstorms in the far north during April, and due to the fact that 2016 is shaping up to be the hottest year on record by a long shot globally all contribute to an overall pattern setting Western North America up for another weird Summer of freakish weather.
Never Before Seen Heat Over Western North America
(We have never seen Winter heat like this before over Western North America. This set-up creates a dangerous preparation that results in a heightened risk of seriously severe Summer extreme weather events like heatwaves, droughts, wildfires and thunderstorms ranging well into the far north. Note a similar preparation for Western Russia and North-Central Siberia. Image source: NASA GISS.)

Much higher than normal temperatures predicted over the US West, Northwest, Central, Northern and Western Canada, and Alaska are likely to result in increased risk of wildfires, heatwaves, drought, and related severities. 

Thunderstorms ranging far into the north where the permafrost thaw zones are now expanding bring together an unprecedented combination of new fuels for fires and more intense ignition sources in the form of Arctic thunderstorms. 

Possible early melt and low albedo related accumulation of abnormal warmth in the Arctic could exaggerate these extremes even outside of the high ranges which NOAA models are now predicting. And the pole-ward progression of El Nino related heat in the shift toward La Nina should propagate strongly along the now well-established pathway of the Northeastern Pacific and the North American West.

Such new weather and climate tendencies will almost certainly continue to result in weather events that residents will find odd and freakish. To this point, if you observe an extreme heatwave, instance of wildfire, or other instance of extreme weather in your area over the West this Summer it has almost certainly been given a serious amount of added oomph by the expanding number of climate change related conditions affecting your region.
Links:
Hat Tip to Cate
Hat Tip to DT Lange
Hat Tip to Greg
Hat Tip to Colorado Bob
Hat Tip to Jean


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