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Jet Stream Tattered By Climate Change Brings New Bout of Worst Storms On Record For North-Central US

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(Mangled Jet Stream on June 20th, 2014 together with cut-off upper air low threatens record-shattering storms and flood events across a multi-state region from the Dakotas to Minnesota to Iowa and Nebraska over the coming days. Image source: Earth Nullschool. Data source: NOAA.)

If you wanted an example of a Jet Stream mangled by human-caused climate change, you couldn’t find a better one than today’s tangle of upper level winds swirling over North America.

It’s a chaotic maelstrom of split flows, colliding storm tracks, blocking highs, and cut-off upper air lows. A barrel of snakes pattern that’s become ever-more-common since Arctic sea ice plummeted to staggering volume lows of nearly 80 percent less than 1979 levels at end summer of 2012. A loss that opened wide the gates for warm air to flood northward and confuse the hot-cold dividing line that drives this key weather governor.

Over the past week, we’ve seen what amounts to a mess of storms mostly locked in place. A Pacific Ocean flow squeezed between a blocking high off California and an upper level low south of Alaska drew a train of moisture trailing all the way across the Pacific into a hungry cut-off low that had stalled along the border between Canada and the US. Drifting slowly east to west, west to east, the low gorged on the synoptic moisture feed, dumping record rainfall after record rainfall over the Dakotas, Minnesota, Nebraska and Iowa.

100 Year Records Shattered

By the 16th of June, with just slightly more than half the month passed, Sioux Falls South Dakota had crushed its all-time record rainfall for any month by more than 2.5 inches. The previous record of 9.42 inches set in 1898 catapulting to a staggering 13.04 inches by early this week. And with the storm track writhing overhead the rains for the region just kept coming. By yesterday, the twin cities region in Minnesota had rocketed to its second wettest June on record amidst massive rainfall-driven landslides and region-wide preparations for Mississippi River flooding. At 10.33 inches measured rainfall so far, with storms still popping overhead, and with 11 days still remaining in the month, it appears the area may well be set to shatter the previous rainfall record of 11.67 inches set back in 1874.

(Record flooding along the Big Sioux River in Iowa and South Dakota as witnessed yesterday by Storm Chasers.)

All the massive rainfall has built up quite a pulse of flood water that is now moving down major river systems and threatens record flooding events throughout a multi-state region from the Dakotas to Minnesota to Iowa to Nebraska. Residents are being called to aid in sand bagging and other flood mitigation operations as rivers keep rising through numerous regions. According to a report today in the Christian Science Monitor:

“In Iowa, South Dakota, and Nebraska, officials are asking volunteers to build sandbag barriers and other fortifications in advance of the brunt of the storm – but politicians and emergency workers are conceding that their efforts, in some areas, may not be enough.

In South Dakota, workers have begun turning a major Interstate exchange bridge into a temporary levee. While officials there say that will mitigate the flood in many locales, Governor Dennis Daugaard (R) said he expects parts of North Sioux City, S.D., to be underwater by the end of the week.”

Storms Expected to Continue

Today a frontal boundary sweeping out from our upper air low is bringing rains to the Great Lakes and Central Plains region. Meanwhile, behind the front, instability and moisture flow beneath the low continue to result is a high risk for severe thunderstorms accompanied by strong winds, torrential downpours, hail and frequent lightning. Severe storm risks are most extreme for areas of southeastern Nebraska, western Iowa, northern and western Minnesota, and eastern North Dakota.

Already, satellite imagery shows strong storms and accompanying high cloud tops popping up over Nebraska with more likely to follow as afternoon and evening progresses.

Conditions in Context: How Climate Change Intensifies Droughts/Storms

Multiple news agencies are now gathering reports of record storm events throughout the affected multi-state region. Recording agencies and residents alike note a dramatic increase in both the frequency of record events and in their intensity.

Storm precipitation intensity is a measure of how much rain, snow, sleet or hail falls from a given storm over a given period. And what we have seen is an increasing number of record hourly rainfall events in which precipitation totals measure 1 to 2 inches or more within a 60 minute span. Such intense events rapidly overwhelm infrastructure, flood roads, and burst river banks, creating a dangerous situation that often results in numerous water rescues. And both local and national climate reports have marked a major increase in both precipitation and precipitation intensity over the past two decades for regions such as Iowa.

In the context of human-caused climate change, frequency of intense storm events is increased due to rising atmospheric moisture loading. Overall, for each 1 degree C increase in temperature, the hydrological cycle increases by about 7% in intensity. The current .8 C rise since 1880 has resulted in about a 6% increase in the rate of evaporation and of rainfall. So in regions where heat and dryness tend to take hold, the soils tend to dry out faster, tipping into drought conditions far more rapidly and seeing an overall intensification and lengthening of droughts. And in regions where storms do form, they tend to dump far more rainfall than they used to.

Thunderstorm

(Global warming intensifies thunderstorms by adding convective energy, increasing atmospheric moisture, and expanding the troposphere. As a result, thunderstorm cloud heights increase resulting in more intense rain and hail events. Image source: National Weather Service.)

Changes in the Jet Stream due to loss of sea ice in the Northern Hemisphere also tends to result in more persistent weather patterns. The Jet Stream tends to meander more, spinning off more cut off lows that linger over regions creating instability and rough weather for longer periods. High amplitude waves tend to also form as more warm air invades the higher Latitudes. In the ridges, powerful high pressures tend to dominate. And once these highs establish, they can be very difficult to move. Beneath these blocking highs, droughts proliferate due to the extreme length of dry periods and due to the intensified rate of evaporation. We see such an event now in the 15+ month long blocking high that has so greatly impacted California and the ongoing drought there.

Lastly, increasing convection and a thickening, hotter atmosphere tend to spike storm intensity. In areas where moisture and heat are both high, the explosive rate of evaporation tends to rapidly form storms with very high cloud tops. These cloud tops, now sometimes pushing 50,000 or 60,000 feet pack in more moisture and can generate very intense rainfall events over shorter periods than we are used to.

In these ways, climate change forms an ideal brew for perfect thunderstorms and perfect droughts. With temperatures expected to spike to +2 C or great anomalies over the coming century, we can look forward to extreme weather continuing to intensify with both record rainfalls and record droughts dominating with ever-increasing frequency.

 

 

Links:

Weather Underground: Record Rainfall in Sioux Falls South Dakota

Twin Cities: Flood Preparation Begins as Record Rainfall Sends Mississippi Rising

Global Warming to Spawn More Severe Thunderstorms

Warming Planet Could Spawn Bigger, Badder Thunderstorms

How Climate Change Wrecks the Jet Stream, Amps up the Hydrological Cycle and Spawns Severe Weather

Hat Tip to Colorado Bob

Hat Tip to TodaysGuestis

 

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Mangled Jet Stream Brings Worst Storms in Five Decades to Sichuan China; Approach of Super Typhoon Soulik to Result in Hybrid Rain Superstorm?

A persistent south-north flow of the Jet Stream has dredged moisture up from the Indian Ocean, India and Bangladesh and deposited it in a deluge that has persisted over Sichuan, China for at least the past five days. Rainfall in many areas were the worst seen since weather records began in 1954. In one example, the city of Dujiangyan experienced 37 inches of rainfall over the course of 40 hours.

The floods forced nearly 100,000 people to evacuate and have impacted at least 2 million people across the region. Over 200 people are feared dead or missing. With some towns buried under as much as 20 feet of water, thousands of homes and buildings have been destroyed or damaged with transportation brought to a stand-still in many of the effected regions. In hard-hit Dujiangyan, a local resort was buried when a hillside collapsed, burying the area to tree-top level in mud and debris and spurring the evacuation of 352 tourists. Raging floodwaters also caused a nearby bridge collapse that sent at least six vehicles into raging flood waters.

In the video below, provided by KIDgrownup, we can see the raging floodwaters washing away buildings and heavy equipment as people flee the disaster site:

Changed Jet Stream Causes Dangerous, Persistent Weather Pattern as Super Typhoon Approaches

A dwindling, but still significant, number of media sources continue to claim that we cannot attribute single events such as the most recent Sichuan Floods to climate change. Unfortunately, this claim is simply untrue. Climate is a measure of weather over a given area during a long period of time. As climate changes so does the weather. In Europe, for example, major flood events are now twice as likely as they were forty years ago. This 100% increase in floods can be directly attributed to changes in Europe’s climate and, as such, fully 50% of each new major flood is, therefore attributable to climate change. And the fact that the most extreme floods are getting more extreme can also be attributed to climate change. In this case, saying a single record flood event, like the current Sichuan flood, cannot be attributed to climate change is at least 50% untrue. Would a flood like this have occurred, eventually, if climate hadn’t changed? Probably. But it likely would have happened 50, 100, 200 years or more later. Would it have happened this year, the way it did, without climate change? Absolutely not.

At the micro level, we can also look at weather patterns and clearly point out how they are not normal and how they’ve changed as a result of human-caused climate impacts. In the example of this week’s Sichuan Floods, the Jet Stream created conditions where heavy rains, so far, have stalled over Sichuan to inundate the region.

Sichuan Floods July 8

(Sichuan Floods, July 8. Image source: Lance-Modis)

In the above image we can see a thick blot of clouds hovering over Sichuan in Central China. This dense band of clouds is the result of a cut off upper air flow of the Jet Stream forming a strong, persistent upper level disturbance. To the south, we can see a broad band of clouds and moisture being drawn into the system from the Indian ocean and over India, Bangladesh, Thailand and Vietnam. To the east, a tropical system in the Korean Sea also contributes moisture to feed this large storm.

What is most unusual about this particular weather pattern is that it doesn’t move. And we can see this when we switch to today’s Lance-Modis shot. The below image is 4 days later than the July 8 shot. But the storm over Central China has hardly budged.

Sichuan Floods July 11

(Sichuan Floods July 11. Image source: Lance-Modis)

In this shot, the cut off upper level flow in the Jet Stream remains, the dense cloud pack over Central China remains, the strong upper level low remains, and the moisture flow from the Indian Ocean and related regions remain. Ominously, the only marked difference in this shot is the looming approach of super typhoon Soulik from the China Sea. This major typhoon packs winds in excess of 140 miles per hour and could cause severe damage to Taiwan. However, it’s the ability of this system to deliver moisture into an already moisture rich upper level air flow that may result in even worse conditions for Eastern and Central China over the next few days as the storm is projected to make landfall in Eastern China, then track as far as 200 miles west of Shanghai. At this point, some weather models, including the ECMWF ensemble, show Soulik getting absorbed by the cut-off upper level low now parked over China. Were this to happen, the resulting rain event could be far more substantial than even the record floods seen over the past few days.

The Climate Change Link To Extreme Weather

So how did climate change create the conditions in which this dangerous situation emerged?

  1. The upper level Jet Stream was caused to meander due to a climate change induced loss of sea ice and summer snow cover.
  2. These changes resulted in a slower progression of weather patterns and more cut-off upper level disturbances.
  3. The added atmospheric heat content added both moisture and instability, adding fuel for storms like this one.
  4. Increased ocean temperatures made moisture and heat delivery from ocean systems and tropical cyclones more likely.

Without these conditions, the Sichuan floods were unlikely to have happened with such force, violence and to have been so persistent and long-lasting. And now, a bad situation is made worse via the ocean delivery of a super typhoon, just one of many more frequent storms to plague this region over the last 40 years. An increased frequency a recent scientific study also attributes to climate change.

Hybrid rain superstorm to form over China? Hopefully, not. But, at this point, things aren’t looking too good.

Links:

Lance-Modis

Rainstorms Flood Sichuan China

China Floods Death Toll Rises

Taiwan Evacuates 2,000 Tourists as Super Typhoon Soulik Looms

ECMWF

 

 

 

 

 

 

Blocking Patterns: Rivers of Moisture to Converge in Major Rain Event For Eastern US?

Water Vapor July 2

(Image source: GOES/NOAA)

Today, a very muscular blocking high pressure system located over the Western US flexed. After having set off record fires and heat waves it reached deep into the Arctic and drew moisture and more unstable air down from over Hudson Bay across the Rockies and over top of Arizona and New Mexico, igniting powerful thunderstorms which blanketed large areas in hail, heavy rainfall and lightning. A second moisture stream drawn into the high’s circulation from the Pacific also fed these storms.

You can see the bright, high, cold cloud tops now firing over Arizona and New Mexico.

To the east, an upper level low pressure system is just now starting to draw this concentrated moisture into two other feeding, damp air flows. The largest draws straight up from the Caribbean over Florida and then rushes up the US East Coast. The second, pulls moisture from tropical storm Dalila in the Pacific, draws it over Mexico, then pulls it over Mississippi and up the back side of the Appalachians.

The action of this powerful blocking high over the US West and associated upper level  low over the East is likely to result in very moist, rainy conditions for a large section of the country east of the Mississippi River. On the Gulf Coast, as much as 5-8 inches of rain is expected. But a wide swath shows potentials for 1-5 inches over the coming week.

This persistent wet and extremely moist flow raises the risk of flash flood conditions where major storms light off. Record rainfall over many areas has already left the ground saturated and atmospheric conditions are very unstable, setting off the potential for powerful storms.

The broad sweep of these convergent moisture flows also sets up the possibility that even more violent conditions may emerge. Large blocking highs were associated in all the major flood events that have occurred around the world so far this year. In one example, noted by commenter Colorado Bob, Pakistan suffered 120 degree heat under a blocking high during May and June. The high then swept a massive flood of moisture up over India and into the Himalayas. The result there was devastating floods that left hundreds dead in a virtual tsunami of mud and water.

The strength of the current upper level pattern, drawing moisture from the Arctic, the Pacific, a tropical weather system, and from the Caribbean sets in place the components for major instability to meet with four rivers of moisture over the Eastern US. It’s a dangerous set of circumstances that may result in current rainfall forecasts under-shooting long-term totals. This week has already seen a number of torrential downpours over broad sections of the US East Coast. But this flow taps even more moisture than what was previously in place, drawing from multiple sources across an area spanning more than 4,000 miles to link rivers of moisture with unstable air. Let’s hope these convergent flows don’t set off flood events similar to those seen in Europe and India this year.

Fair warning: the mangled Jet Stream now has the Eastern US under the gun.

(Hat tip to X-Ray Mike for his comments on strange storms in Arizona today).

 

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