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Unprecedented Climate Extremes: One Year After Record Drought, Lake Oroville is Spilling Over

We know that climate change pushes the weather toward extremes, but this is getting ridiculous. In California, in less than a span of 24 months, water levels at a key reservoir have shifted from record drought to a flood that’s now endangering the state’s water supply system. Unfortunately, it’s these kinds of extreme shifts that we’ve come to expect from human-forced climate change.

Record California Drought

During 2015, California experienced its hottest winter on record. The same winter was also California’s driest in 65 years. It was an extremely dry season that occurred during one of the most intense droughts ever to strike California (2011 through 2016). A period that included the worst dry spell ever to affect the state (2011 through 2014).

driest-period-on-record-for-california

(2011 to 2016 included the driest period on record for California producing extreme water stress for the state. Image source: The US Drought Monitor.)

A 2015-2016 El Nino brought hopes of rain. It also brought concerns that when the rains did finally arrive, they would come as deluges. This concern was driven by the fact that the warming atmosphere now holds an unprecedented amount of moisture. With much of that extra moisture bleeding off of the Pacific Ocean and with El Nino producing a tendency to both intensify the Pacific storm track and to aim rivers of moisture at California, these concerns appeared to be at least somewhat valid.

But, for the most part, the rain held off — increasing concerns that a drought that had already lasted for five years could continue. That an odd weather pattern called the Ridiculously Resilient Ridge might be a semi-permanent feature spurred by warming in the Arctic and a related movement of the Jet Stream northward.

Followed By Record California Flooding

The Jet Stream did flatten and the rains did eventually come, however. And when they did, it was at the oddest of times — when El Nino had long since faded and a weak La Nina — which typically brings drier conditions to the U.S. West Coast — was in full bloom. By January of 2017, the pattern had switched. And when it switched, it switched hard.

A massive river of moisture began to flow from the Philippines all the way to California during December of 2016. The atmospheric river linked up with a raging storm track running 6,000 miles across the Pacific from Japan to the U.S. West Coast. And this combined moisture flow and vigorous storm pattern has pummeled the U.S. West Coast for the better part of six weeks.

river-of-moisture-2017

(Throughout the winter of 2016-2017, a powerful, 6,000 mile long, river of moisture has produced a succession of strong storms running into California. This weather/climate feature is occurring in a record warm/moist atmosphere. The result has been that conditions in California have shifted from extreme drought to extreme flood. Image source: TPW Version 2.)

Some regions of California experienced their wettest January on record. Sacramento was one of these. Throughout California, records for the top ten wettest comparable periods were shattered. According to the Washington Post:

…by one important measure, there’s been more rain and snowfall in the 2016-2017 water year than any other season on record, to date. The California-Nevada River Forecast Center uses an eight-station index in the North Sierra to quantify the region’s precipitation. As of Feb. 12, these eight stations have received 68 inches — 226 percent of normal.

In the region of Lake Oroville — a reservoir that as recently as 2015 had dropped to extreme low levels — the rainfall has been particularly consistent and heavy. And it now appears likely that the winter of 2016-2017 will be the wettest on record for that region at least.

Weather Extremes Damage Critical Water Infrastructure

The Lake Oroville Dam had never seen so much water flowing into its backing reservoir since its completion in 1968. By January, Dam operators were already releasing considerable flows of water through its primary spillway to reduce pressure off the 800 foot tall structure trapping water within the reservoir. By February, more than 55,000 cubic feet of water per second was sent raging down the spillway in an effort to keep water levels below the over-topping line. Unfortunately, the spillway structures supporting the Dam have likely never seen so much continued stress from strong water outflows related to record high water levels. And as of last week, the powerful floods of water released from the Dam had damaged the primary spillway. The spillway’s concrete apron had eroded and initially produced a 300 foot wide sink hole near the top of the spillway that later expanded.

(Lake Oroville forced to use emergency spillway resulting in severe stress to key California water infrastructure. Video source: KCRA.)

Concerns about how an expanding sink hole in the reservoir’s wall could, in the worst case, breach the Dam wall and result in a catastrophic failure spurred operators to shut down and reduce water flows through the primary spillway. The abatement resulted in water levels at Lake Oroville rising to above 901 feet. This triggered an automatic over-spill into a second emergency spillway (the first time this has happened in the Dam’s history). But over-topping water also produced severe erosion — igniting more concerns of structural failure. And on the weekend of February 10th -12th, nearly 200,000 people were evacuated from the Dam’s outflow zone as a potential catastrophic structural failure could cause a 30 foot wall of water to rush through numerous downstream communities.

Over recent days, rainfall in the Oroville region abated — providing a brief window for repairs and reducing stress to the Dam. Round-the-clock emergency repairs in the form of bags of boulders used to buttress the Dam appeared to have shored up the Dam. Meanwhile, water levels within the Dam earlier this week were dropping by 4 inches per hour. Mandatory evacuation orders were lifted. And downstream residents began to trickle back in.

noaa-7-day-precipitation-forecast-lake-oroville

(More heavy rain on the way is likely to continue to produce a touch and go situation for the Lake Oroville Dam. If heavy rain continues through spring melt, the Dam could face considerable additional challenges. Image source: NOAA.)

However, the underlying weather conditions that caused so much damage to the Lake Oroville Dam have not yet changed. February and March are typically California’s wettest periods. And the massive river of moisture feeding into a powerful Pacific storm track continues unabated. Over the next 7 days, NOAA predicts that as much as twelve and a half inches of rain could fall on the Lake Oroville region.

Harmed by Drought, Harmed by Flood

So much rainfall will again likely necessitate considerable water outflows from the Dam’s damaged spillways — producing more stress to the already burdened structure. In addition, the arrival of warmer weather come March and April will add snow melt to the already considerable rainfall inflows coming into the Oroville system. To be clear, most experts still think that the overall risk of losing Oroville due to a complete failure of the Dam remain low. However, such a loss would be catastrophic to California.

more-heat-more-heavy-precipitation

(As the climate warms, it produces more record hot weather — which spurs increasing instances of drought. In addition, when precipitation does fall, it tends to come in the form of more heavy precipitation events where the rain that does fall, tends to fall more intensely over a shorter period. As a result, the human forced warming of the Earth is producing a general tendency toward more extreme instances of drought and flooding. Image source: NOAA/UCAR.)

The Lake Oroville reservoir provides drinking water to 23 million residents in California and irrigates 750,000 acres of farmland. In the outside worst case event where the Dam does fail, it would produce a water crisis for numerous residents and communities in addition to any damage caused by severe downstream flooding. But even if the Dam holds through the Spring, extreme deposition of sediment from heavy water flows running into the reservoir will also likely pose challenges to water access.

It’s a case of too much or too little. From 2011 through 2016 drought threatened Lake Oroville’s water supplies. Now it’s flooding. And unfortunately, with climate change, we can expect the weather in many regions to take on extreme characteristics or switch hard from one extreme to the other — as has been the case with California.

Links:

Climate Central

The US Drought Monitor

TPW Version 2

Stress Test isn’t Over for Lake Oroville

Record Rain is Straining California’s Whole Flood Control Network

KCRA

NOAA

Lake Oroville Critical to California’s Complex Water System

NOAA/UCAR

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New Extreme Climate to Hurl More Rain Bombs at Texas, Light off Another Record West Coast Heatwave

They call them rain bombs. A new breed of severe storm fueled by a record hot atmosphere. One capable of dumping 2-4 inches of rainfall an hour and generating voracious flash floods that can devour homes and cars in just minutes. And in southeast Texas, the rain bombs have been going off like gangbusters.

In this week’s most recent iteration of flaring, climate change induced, storms, a region north of Houston and south of Dallas saw flood after flood after flood. Now, hundreds of people have been forced to abandon inundated homes, thousands of cars have been submerged, and seven people are dead. Rainfall totals for the region over the past seven days have averaged between 7 and 10 inches. But local amounts in the most intense bombification zones have come in at 16, 19, and even as high as 30 inches in Washington County. All time record rainfall totals that might be associated with a powerful hurricane. Floods that would typically happen only once every 500 years. But in the new moisture-laden atmosphere of a record warm world, a garden variety thunderstorm now has enough atmospheric oomph to frequently set off what were once multi-century floods.

Rain bombs over Texas 3

(Rain bombs again explode over Texas in a huge complex of storms on Tuesday afternoon in this GOES enhanced satellite shot. It’s all part of the same stormy weather pattern — associated with a trough and an upper level low — that over the past five days produced another round of record flooding over Texas. And it’s expected to remain in place through the end of this week. With more severe storms firing and 4-8 inches of additional rainfall on the way for some sections of soggy Texas, it appears that still more extreme flooding is likely. Image source: NOAA.)

It’s under these new, freakish, conditions that the Brazos River is today expected to crest at 53.5 feet — its highest level ever recorded. And this crest is predicted to push a flood of 8-9 feet into neighboring communities. Extreme flooding that local officials say Texans are not at all prepared for. In total, more than 40,000 people have been urged to evacuate. But with the worst flooding still on the way, the situation is still very fluid.

In isolation, the current Texas floods would be an extreme record disaster worthy of the weather history books. But it is just one of three such severe rainfall events to strike southeastern Texas since April. And, unfortunately, more storms are on the way as a strong ridge of high pressure out west is expected to generate another deep Central US trough and related rain bomb inducing storm pattern over the next five days.

West Coast Turns up the Heat

As parts of Texas face never-before-seen flooding, the US West Coast is staring down the gullet of an extraordinary surge of heat. A gigantic blob of hot ocean water off that region of the world is feeding the growth of a powerful atmospheric wave. And once the ridge of this wave really starts to swell northward on Friday, Saturday, and Sunday, record hot temperatures are bound to explode all over the US West Coast and on up into Canada.

image

(Sea surface temperature anomalies on May 31, 2016. Extremely hot sea surface temperatures over a vast area stretching from the Equator to Alaska and all along the US West Coast enhance the development of strong ridges in the Jet Stream that have tended to spur extreme heatwaves over the past few years. Ocean temperatures over this zone now range between 1 and 6 C above normal late 20th Century values. Image source: Earth Nullschool.)

In Fresno, the mercury is expected to rocket to 108 degrees Fahrenheit by Saturday — or about 18 degrees above normal for early June. Sacramento is expected to see 106 F readings at the same time — which is around 20 degrees above average for that Central California location. Further north, temperatures are also expected to skyrocket with Portland predicted to strike near 98 F on Sunday and Spokane calling for 96 F. In fire-ravaged Fort McMurray, the mercury is expected to top out at 85 F on the same day.

This expansive bulge of heat is expected to cover pretty much all of Western North American. Rising from the Desert Southwest, it is predicted to run through Oregon and Washington, rise up through Canada, and touch even the shores of the rapidly thawing Arctic Ocean.

Conditions in the Context of Human Caused Climate Change

The broader conditions fueling both record rain and potential record high temperatures over the North American West are the same. A record hot global atmosphere is one that is burdened with more heat and moisture than ever before. One that will inevitably produce more extreme rainfall and heatwaves than we are used to.

Locally, additional features related to a fossil fuel based warming of the world further contribute to the problem. Over the Northwestern Pacific, sea surface temperatures ranging from 1-6 degrees Celsius above average (2 to 10 F) generate a tendency for heatwaves and strong high pressure formation. These systems have often taken in all of the US West even as they’ve extended on up into Canada and Alaska. Adding to the problem is sea ice loss over the Arctic Ocean — which as of today is seeing the lowest ice extent ever recorded for this time of year. This sea ice loss tends to aid in Arctic warming which weakens the Jet Stream, which in turn tends to meander — creating these exaggerated trough and ridge patterns that have been associated with so much extreme weather recently.

image

(Earth Nullschool map of Jet Stream wind pattern predicted for early June 5, 2016. A powerful ridge expected to form over the US West Coast is predicted to drive record heatwave conditions there by this weekend even as a facing trough will again spike the risk for extreme rainfall events over Southeastern Texas. This Jet Stream feature and related severe weather conditions — ranging from severe heat to floods — is now influenced by numerous effects currently emerging as human-forced climate change worsens. Image source: Earth Nullschool.)

Large, hot ridges forming in one region tend to generate deep, stormy troughs in another. And the ridge over the US West has resulted in the formation of a related trough and unsettled weather pattern over the South-Central US centering on Southeast Texas. This trough has pulled cold, unstable air into the upper levels of the atmosphere over Texas even as it fed upon an uncanny volume of moisture streaming in off the abnormally hot waters of the Gulf of Mexico and Pacific Ocean.

The results? Well, we’ve already experienced them in the form of record floods for Texas, periods of record heat for the Western US, and a never-before-seen May wildfire outbreak in Alberta, Canada. This week, the overall pattern is again expected to ramp into high gear — which is likely to produce possibly never-before seen June heat out west and more extreme flooding for Texas.

Links:

Texas Floods Force Evacuations

Texas Floods: More Rain is Coming

Death Toll Rises to Seven in Texas Floods

Hundreds of Homes Destroyed in Texas Floods

Observed Precipitation NOAA

NOAA/National Hurricane Center

Weather.com Local Forecasts

US Climate Data

Earth Nullschool

 

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