New intensity scale ranks California’s ‘atmospheric river’ storm events just like hurricanes

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Image: The long white cloud band is an atmospheric river hitting California in January 2017. Credit: Jesse Allen, NASA Earth Observatory/ VIIRS/ Suomi satellite

Remember the series of reservoir filling and snowpack building winter storms California experienced mid-January? It was the result of an “atmospheric river” driving a series of Pacific storms onshore, just like the event that busted the Oroville Dam spillway in 2017, but not nearly as strong.

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The January 8-9 2017 AR event that was a major driver behind the Oroville Dam spillway crisis. Credit: The SSMI satellite sensor of Defense Meteorological Satellite Program.

Now there is a new scale to characterize strength and impacts of atmospheric river type storms, just like hurricanes. The scale is useful because atmospheric rivers often have a significant impact on California, bringing large amounts of snow, rain, and sometimes, catastrophic flooding. They are also a significant source for our water supply.

A new study, in the February 2019 Bulletin of the American Meteorological Society, and published by Scripps Institution of Oceanography at the University of California San Diego ranks the strength and impacts of these “atmospheric rivers” (AR) type storms, sometimes called a “Pineapple Express” due to some of the moisture originating as far away as Hawaii.

Just like we have with hurricane strength categories, this new scale assigns five categories to atmospheric rivers from 1 to 5 and labels the categories “weak,” “moderate,” “strong,” “extreme,” and “exceptional.” The categories consider the amount of water vapor the carried by the AR and the duration at a given location.

While the scale might be fine for helping people understand the strength of the storm when reported in the news, the real value is helping to determine if the AR will be beneficial, hazardous, or both.

The new intensity scale ranks ARs like this:

  • Cat 1 (Weak): Primarily beneficial.
  • Cat 2 (Moderate): Mostly beneficial, but also somewhat hazardous.
  • Cat 3 (Strong): Balance of beneficial and hazardous.
  • Cat 4 (Extreme): Mostly hazardous, but also beneficial.
  • Cat 5 (Exceptional): Primarily hazardous.

From the paper:

For example, in California, there was the “Great Flood of 1862″ which was an AR that continued non-stop from late December 1861 to mid-January 1862. It flooded downtown Sacramento. That storm would be categorized as a Cat5, or “Exceptional”. It is the largest flood event since California was settled.

Downtown Sacramento following the Great Flood of 1862. The city remained underwater for months, triggering a massive reconstruction project to raise the downtown area 10 to 15 feet. Photo Courtesy NWS/NOAA

An example of a Cat 4 (Extreme) AR that would be mostly hazardous, but also beneficial occurred in 2017 on January 8-9. That storm continued for 36 hours and produced up to 14 inches of rain in the Sierra Nevada and causing many rivers to reach flood stage. It was a major contributor to the Oroville dam spillway crisis.

Dozens of other AR events throughout California history can now be ranked by this new system.

In the study, researchers noted that 80 percent of levee breaches in California’s Central Valley are associated with ARs, so this new scale will be helpful to water resource managers and emergency planning personnel in determining if the next storm coming our way will be helpful, hurtful, or both.

Reference: http://blog.ametsoc.org/uncategorized/new-western-storms-scale-to-describe-intensity-potential-impacts-of-atmospheric-rivers/

 

 

 

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65 thoughts on “New intensity scale ranks California’s ‘atmospheric river’ storm events just like hurricanes

  1. But then of course they can then invent a Cat 6 apocalypse AR, and call it due to climate change is the incremental change to frighten the science illiterate. The upcoming CMIP6-equivalent of RCP8.5 probably will be chock full of Cat 5 and new Cat 6 ARs for Cali.

    What the Left is capable of in their pursuit of power through frightening the people has only the limits of the human imagination.
    Climate Change is indeed the 21st Century version of the Twilight Zone.
    Were he alive today, Rod Serling would blush with envy he didn’t think of it.

    • Of course, Joel nails down intent.

      “The AR scale categorizes events based on the maximum instantaneous integrated water vapor transport (IVT) associated with a period of AR conditions”
      i.e., (IVT ࣙ kg m-1 s-1) and the duration of those conditions at a point.

      Such a complex sounding formula based substantially upon subjective choices.
      e.g.; “at a point”,
      “duration”,
      “those conditions”.

      It is just another climate puff propaganda stunt.

      • I am not worried about the arbitrariness of rank ordering on some scale. It is not possible to rank damage potential because that is dependent on what stupid things people did when building on flood plains.

        I do not like the words “at a point”. What does that mean? At a “point in time” is if time was made up of points? And why isn’t it kg m^3? If it is “transport” then it should refer to the total volume of the flow, not the area (footprint). The precipitation danger comes from the mass concentration, not the total mass spread over an unlimited or poorly constrained volume.

        If the intention is to calculate the total water mass in the column above 1 sq m, that is one way of looking at it. It could be limited to the lowest 50,000 feet, for example.

        It is not obvious how “transport” is related to precipitable or precipitated. Like a passing truck carrying a heavy load – if it doesn’t drop any on top of you, it doesn’t matter how heavy it is.

        I am generally a fan of trying to create novel metrics that are informative so congrats to the people attempting this. Atmospheric rivers are not common but the metric may find use in unexpected ways and places. Perhaps it is a good way to describe some aspects of all thunderstorms.

        • I think “at a point” refers to a location. Picture an imaginary wall of zero thickness rising in the air and perpendicular to the flow at all locations. At any increment of length along that wall you can measure the flow rate across the boundary in kg/m-s. That represents the intensity of the atmospheric water stream at that location below it.

          With that metric, you just indicate the duration those conditions exist. It’s like saying 50mph winds will be flowing across a boundary from 5 to 6:30, 42mph winds from 6:30 to 7:00, and so forth – except here the metric isn’t speed of air at a location but the flow of water in weight.

        • In chemical engineering, for one, the concept of transport is based on area, not volume. Mass transport and heat transport are both related to area flux.

          • Here’s the other problem with any high flux of semi-tropical originated and driven northeastward by a southern branch of the jet stream, copious water vapor (and therefore an “atmospheric river”) moving over a given region being in itself conflated with an extreme precipitation event: it takes a cold air mass to encounter that warm, moist air mass if much moisture is going to get wrung out locally. To wit: I am presently sitting under just such an”atmospheric river” warm front in southern California that has yet to be approached by the cold front to our northwest, and so the total precipitation in the 12 hours since those clouds rolled in has been 0.02 inches, while countrysides hundreds of miles to our east may yet reap significant precipitation out of what has uneventfully passed over us so far, especially in the Colorado Rocky Mountains.

          • I’m speculating, but think they just want to express it in a metric that can be displayed in a two-dimensional chart where lines are used to separate intensities; lines are a single dimension so you want your metric to be “X” per unit length over that line. You’re essentially reducing the two dimensional flow across a vertical surface by projecting it onto the horizontal line or curve on the bottom.

    • So then … the NORMAL, routine, same as it ever was, weather patterns I have personally experienced in this state since 1955 … are being rebranded as … EXTREME weather events.

      Good to know … I guess. Sheesh. When will our government agencies return to accomplishing something productive for our society?

      • You are right – rebranded for political reasons. The phenomena described as ‘atmospheric river’ has been noted and talked about for years here in the NW [at least since satellite photos became common]. Same old same old – just different (and more catchy?) name.

  2. California will have another good snow pack/water year almost guaranteed, similar to 2017. California will have a good summer water level. The question is will the Sacramento watermelons flush the surplus down into the San Joaquin Delta for a bait fish in order to claim a Climate Change-driven water crisis next year?

    The question is will western Colorado/Utah get enough snow pack to help fill Lake Powell and Lake Mead?
    So far for 2019, the Upper Colorado River Basin is at 106% for the 2019 season at 12 February. But we still have long way to go.

    http://www.snowpack.water-data.com/uppercolorado/index.php
    From this graph, one can see the real divergence between what makes a dry year and the wet year always occurs in late April.

    • This past weekend I was at my cabin that is slightly, just slightly east of the continental divide. Looks like there’s plenty of snow on our side. Then again March is the big snow month.

    • The Sierra Nevadas are at ~126% of average snowpack, and all the reservoirs (except Oroville) are at or above historical averages. Any drought in CA for the coming year will be a purely politically driven event.

  3. The word “beneficial” is used in 4/5 categories.
    Sounds to me like more of these AR’s are wanted but I suspect that all they want is another fear factor or headline.
    It is weather for goodness sake.

  4. The California climate is now one of continued drought punctuated by atmospheric reiver extreme rain events.

    How is this not a changed climate? How is it not the result of a warming planet?

    elsewhere there is a post on the electricity company proposing power cuts in potential fire risk situations… so, did the expand or change their power grid in recent decades? Or have the ground conditions in which that grid could cause fires changed? (And no, you can’t only pin that on changed forest clearance)

    so too in Australia: drought interrupted by truly huge cyclone/flood events.

    Just read this account of the Queensland floods from a local rancher. something off the scale in extreme weather terms

    https://www.theguardian.com/world/2019/feb/13/we-have-death-and-devastation-at-every-turn-the-flood-massacre-of-queensland-cattle

    (It has addresses for donations: I hope whatever your view on climate, the plight of these people may touch your generosity)

    • “How is this not a changed climate?

      Yes, according to Griff’s INGSOC Green scripture, Planet Earth was a veritable Garden of Eden before mankind spoiled it with hideous carbon emissions, circa 1850.
      – Any change in climate is clearly now man’s fingerprint since 1850.
      – Never mind the Little Ice Age of 1450-1850 AD.
      – LIA as the coldest period of the last 10,000 years that ended, circa 1850, when man’s carbon sins began.
      – Never mind that human lifespans and standards of living in the industrialized world has risen dramatically, since circa 1850.
      – Never mind that statistically-speaking, Griff would likely either be dead by now or without any teeth and in ill health with syphilis and/or tuberculosis 200 years ago.

      I wonder if Griff ever wonders about where modern medicines like antibiotics come from? How much energy (mostly fossil fuels) it takes to make them? How much his everyday life he blindly takes for granted is owed to the combustion of oil? Even his beer is dependent on fossil fuel.

      Let’s see Griff give up beer and booze in the quest for his carbon emission purity.

    • griff February 13, 2019 at 12:59 am
      Good evening griff

      (And no, you can’t only pin that on changed forest clearance) Sorry griff yes you can.
      A few years back I had to return to Conn on the US east coast to deal with my mom’s estate.
      As I drove in town I kept seeing work crews cutting down trees along the road side> they had been planted in the 1950s when the houses were build. They where cutting down anything that might threaten the power lines. They chipped up all the small stuff and cut the rest into movable lengths and left it all at the edge of the property owners yard. I spoke with the folks in charge of the crews and seeing my Arizona Plates they get me a good schooling. There had been to many storms that toppled trees shattered limbs with power lines broken and homes damaged. Thousands without power it could be the winter or summer.
      I asked about the wood left in the yards he smiled and replied fire wood. If the home owner asked they would also deal with trees that put the homes at risk.
      The last few years my brother has informed me no big outages.
      As for Climate change, but of course. Back in the 1920s long island sound would freeze out to Charles island off the coast of my home town Milford Conn. I have seen old black and while photos of model “T”s driving out on the ice to the island. I have never seen such a thing in my life time.
      The winters are turning cold again there, the frost giants are returning.
      sorry for the length.

      michael

    • “The California climate is now one of continued drought punctuated by atmospheric reiver extreme rain events.

      How is this not a changed climate? How is it not the result of a warming planet?”

      Because that is the way it has always been. It is known as “Mediterranean Climate”.

      • tty, you are one of the climate “illiterates”, If you weren’t, you would know that along with the documented periods of past heavy rains, the longest known periods of drought in California history occurred between 1400 – 1650 AD… a mere 240 and 180 years. Thank goodness climate changed!

      • Folks, Griff and the climate clergy have zero right to be concerned, claim catastrophe, or any other virtue signaling until they completely remove themselves from the benefits of “fossil fuels”.

        You hear me McGruff? You have zero credibility and zero right to complain. YOU are guilty, you are a sinner! Repent! Cleanse yourself of the Christian oil! Free yourself from the bondage of Divine Gas! Repent! Pray to the non deity of inconsistency, for only moral relativism can keep you feeling the correct goodfeel™

        “Repent! Lo, I say unto you, it is harder for a snowflake to get into the Safe Zone than it is for fusion energy to become reality!”

        Book of Gaia, ch. 1, v. 1-3

      • And the ill-fated Donner Party was the result of “early, heavy snowfall near Truckee” in 1846.
        https://en.wikipedia.org/wiki/Donner_Party

        A couple of memorable events from my own lifetime:

        In the Winter of 1964, it rained heavily and almost continuously for about two weeks during Christmas Break during college. The newly constructed earth-fill Hell Hole dam on the Rubicon River breached and a wall of water roared down the middle-fork of the American River, taking out all the bridges between there and Highway 49.

        In the late-1990s, a Pineapple Express with warm rain fell in the upper sections of the Feather River. It fell on a snow pack adjacent to the river canyon, and also on what is known as Serpentine Canyon, an area with little soil or vegetation. The rain immediately ran off the steep slopes of rock in the 10-mile long, straight canyon, and that was joined by the melted snow coming down tributaries of the river. The bridge at Rich Bar was once again demolished. The campground at Beldon, which is about 30 feet above the Summer water level, was inundated. There was a telephone booth (remember what those are?) that was almost completely buried by sand and gravel. The numerous PG&E dams down river muted the effects of the flooding. A meteorologist I was working with corrected me when I opined that it was a 1,000-year flood. He said it was a maximum possible event.

        California has always been a land of extreme weather.

    • Griff, since the worst one in recorded history happened over 150 years ago, the logical conclusion is that the CO2 we are putting out is in fact helping alleviate this, not making it worse. Unfortunately both this statement and yours are unsupported because we don’t have enough data to say anything about precipitation trends in California. Ask me again in about 500 years, if we are still in the interstadial.

      • Please, Please, Please give us the link of the article you want us to read, not the link to the search reaults. We have no clue what article you want us to look at.

    • California is a direct beneficiary of El Nino. The Pineapple Express is usually very active during El Nino events. El Ninos also result in step increases to the global temperature. Most of the warming of the last 40 years was the result of strong El Ninos, beginning in 1976. The converse of ENSO is also true. La Ninas, which usually result in step decreases in the global temperatures, lead to prolonged drought conditions for the West Coast. Most of the West Coast’s worst draughts of the last 100 years occurred during periods of La Nina. Eras dominated by El Ninos (which we are not a part of) result in step increases to the global temperature. They also provide much of North America will heavy rains and heavy winter snow falls.

      It isn’t AGW but ENSO that steers long term weather trends.

    • Griff does his little drive-by and disappears until his next thread bomb. He never responds to factual refutations of his little anecdotes.

      Sophomoric at best.

  5. We should be fighting against the Greens misusing the word “Climate”

    Climate is a 30 year average, and the rest is weather. This is silly, but then who says that the Greens are bright ?
    We need wealth, lots and lots of it, so when the weather turns nasty, we have the means, i.e. money, to fix things up.

    Its called adaptation.

    MJE

  6. Lovin the snazzy new biblical end-times sounding term RIVERS IN THE SKY is trending in the news with its insidious AGW tie in. When you expect to be SMITTEN by an ATMOSPHERIC RIVER, fall to your knees and ATONE FOR YOUR SINS TO BE SPARED THE WORST OF GOD’S WRATH.

    Meanwhile… the decades-old term used by California weather presenters that describes this specific phenomenon PINEAPPLE EXPRESS is falling into disuse because frankly, it sounds way too cute and casual for these end times. Grab your coat Marge, it’s just another naturally recurring weather event. When we expected a visit from the Pineapple Express, it was just rain and you could even wave at it when it went by, like fearless people greeting a train or trying to communicate with cows.

    • Well, this is Climate Scientology, where levels are important. Two things. First, the levels need to go from 1 to 8. And AR dupicates the IPCC abbreviation for its Assessment Reports. I think we should go back to Pineapple Express levels 1-8. L. Ron Mann should not allow this sloppy terminology to define immaculate “technology.”

    • Actually, the reason it has been changed to atmospheric river is that Pineapple Express is too geographically limited. Pineapple Express limits it to the West Coast US. It has been discovered that atmospheric rivers are not limited to the West Coast US. They occur globally. Many of them don’t even affect land. Because of North American geography, the West Coast does see greater impact than elsewhere. (long fetch area interacting with mountain ranges perpendicular to the flow.) The gulf coast does occasionally get atmospheric rivers, but with the limited fetch area of the Gulf of Mexico and the Appalachians orientation parallel to the flow, the impact isn’t as great. The same goes for Europe. Mountain ranges (the Alps) parallel to the flow and the fetch in the Atlantic being much less than in the Pacific.

      • The Pineapple Express storms that hit CA continue across the country to the Rockies and beyond, providing winter snow. When I lived in SF, my son lived in Denver. If SF had a rain storm it was easy to predict snow for Denver within the week.

  7. From the article: “An example of a Cat 4 (Extreme) AR that would be mostly hazardous, but also beneficial occurred in 2017 on January 8-9. That storm continued for 36 hours and produced up to 14 inches of rain in the Sierra Nevada and causing many rivers to reach flood stage.”

    It sounds to me like this is rating the particular storm front passing over Calfifornia rather than the atmospheric river. The atmospheric river lasts a lot longer than 36 hours.

    Here’s a link to nullschool showing the atmospheric river called the Pineapple Express (marked):

    https://earth.nullschool.net/#current/wind/isobaric/700hPa/orthographic=-113.57,44.96,401/loc=-135.728,24.970

    • Right after I posted previously I realized I had completely misunderstood the point of the post. For some reason I was thinking they were ranking the power of the jet stream, instead of the power of the storms traveling along the Pinapple Express jet stream. Don’t ask me why I did that. My excuse is it is early in the morning. 🙂

      I don’t have any problem with them ranking storms in this manner just as long as they don’t try to connect it to CAGW. These storms have been happening long before humans could have any impact. Gving them a number for intensity is ok with me.

  8. My concern at this point is using the terminology of “Cat 1-5”. Since these terms are already in use for hurricanes and typhoons, this could lead to confusion for the “less informed” population who will no doubt confuse the events. I assume the Weather Channel will also start naming them.

  9. I read once that the flood of 1862 was bracketed by droughts in 1861 and 1863, but since then have been unable to verify that fact (I haven’t looked that hard, though).

  10. “For example, in California, there was the “Great Flood of 1862″ which was an AR that continued non-stop from late December 1861 to mid-January 1862. It flooded downtown Sacramento

    It flooded the entire Central Valley to a depth of 30′.

  11. So now extreme weather events that reload water supply in the Klamath Mountains, the Cascade Range, the Basin and Range, the Coast Ranges, the Sierras, the Transverse Ranges, and the Peninsular Ranges that feed the Basin, Central Valley, the Colorado Desert, the Modoc Plateau and the Mojave Desert will now be considered not beneficial and only destructive? I don’t get it. They now do NOT like weather patterns that bring a steady supply of precipitation to the area? Like the 70’s when the Arctic was still considered to have a “normal” amount of ice in it?

    But…but…I thought everyone was bemoaning the lack of snow pack due to all the jet loving, must-fill-the-car-garage, CO2 producing Californians and think that condition is the non-beneficial one.

    Goodness! There is no pleasing these spoiled brats!

  12. A very useful scale – for a historian. We won’t know the “intensity” until it is over. This contradicts the usual meaning of “intensity”.

  13. This sounds like a great idea.

    But get ready for a series of “greatest AR on record” news items. And “this is exactly the type of AR you can expect with global warming.” And “with global warming we can expect more of these events.”

  14. “Climate Change, 1861 Style

    “You might be forgiven for not knowing the details of one of the most catastrophic climate events to have ever struck the United States. It happened 150 years ago, in 1861. That’s more than 150 years ago and that’s a long time. People in America are likely to remember the initial year of the Civil War, while Europeans are perhaps more likely to remember the unification of Italy under King Vittorio Emmanuele. 1861 was the year Benito Juarez captured Mexico City. The apolitical among us might mourn the deaths that year of Elizabeth Barrett Browning or Lola Montez.

    “But December of 1861 saw a 43-day storm in California, one that turned much of Central and Southern California into inland seas.

    […..]

    “The flood decimated California’s burgeoning economy. An estimated 200,000 cattle drowned, about a quarter of all the cattle in the ranching state (the disaster shifted the California economy to farming). One in eight houses was destroyed or carried away in the flood waters. It was also estimated that as much as a quarter of California’s taxable property was destroyed, which bankrupted the state.”

    https://thelukewarmersway.wordpress.com/2016/02/16/climate-change-1861-style/

  15. What is called “Atmospheric River” here is simply the result of agglutinations of depressionary troughs at the front of multiple vigorous 1037 hPa Mobile Polar High (see Leroux) from Bering Strait that reached the meteorological equator, advecting huge amount of moist air toward California.
    This analysis is confirmed by the weather evolution from Jan. 6 to Jan. 9 2017 as seen on satellite images.
    On Jan. 10 at 12 UTC, another system of MPHs originated from Kamchatka is taking the relay.

  16. In Australia the Bureau of Meteorology is doing a similar thing – to ensure that they can report more heatwaves. We now have:
    Low Intensity Heatwaves
    Severe Heatwaves
    Extreme Intensity Heatwaves
    The bulk of heatwaves at each location are of low intensity, with most people expected to have adequate capacity to cope with this level of heat.
    A heatwave is defined as three or more days of high maximum and minimum temperatures that are unusual for that location. The same high temperature will be felt differently by residents in Perth compared to those in Hobart, who are not used to the higher range of temperatures experienced in Perth.
    Heatwaves are a normal part of summer conditions in Australia, but now we will have regular headlines reporting every week that there is another heatwave somewhere in Australia. Be afraid of this brainwashing.

    • Just see what the insurance companies will do.

      I let my house insurance lapse by 2 days, tried to renew, they said I have to go through the whole process from scratch. When they discovered my house is less than 10m from bush, they refused to insure me. I mean, I live in the bush, what do they expect?

      I went to another insurer, and after two years of at least 10% increases, they doubled my premium. When I asked why, I was told that I love in a high risk cyclone area. I replied that I’ve always been in the same area, what’s changed? Policy, apparently. Even though my house is Cat 6 rated, steel frame on a concrete base as per regs.

      Went to a local broker, halved my premiums from the previous year (1/4 of the new proposed premium).

      The insurance companies are cashing in big time.

        • Ooops, yes I think that’s Cat 5, although they may have different scales bases on potential exposure, like at the top of a hill. I must admit to not being sure.

  17. Wind here is 39 sustained, gusting to 55 mph at the airport. Hit 37 mph sustained at my house. We call that “Wednesday”. However, maybe someone can make a scale for this and then blame it all on climate change to score points. A scale makes everything so much better, you now, like naming storms does.

    No good ever comes of trying to quantify weather when weather has been weaponized by the climate change crew.

  18. It is amazing how muddled people can get about weather events. I grew up living very near the Ohio River. Few seem to remember the spectacular floods that have happened. An example occurred a few years back when it became clear a very high crest was expected. My 80 plus year old father had to remind people in some of the low areas that they needed to put in their “drain plugs” so that the river water didn’t come up the drains. Some were unaware of the use of these devices since the last high crest was more than a generation ago. Nature doesn’t cater to human memory and most of the people living today have no idea how wildly our (put in anything natural) events have varied. Two years ago my grandson and I fished in the Eel river in California at which time it was barely moving any water, maybe 20 cfp. In 1964(there have been others) the river took away towns: http://www.pottervalleywater.org/eel_river_1964_flood.html
    And, wait for it, they called it a pineapple express. There is nothing new here, including the naiveté of the public and the people who wish to manipulate them.

  19. AGW is definitely creating bigger clouds. They look fluffier and fuller than they have in the last 30 years.
    Please don’t ‘deny’ that they are bigger.

    [citatations, studies, measurements? Any proof at all besides your opinion? -mod]

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