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Then we are due for an ArkStorm or Atmospheric River. From the USGS: "...This document summarizes the next major public project for MHDP, a winter storm scena

Then we are due for an ArkStorm or Atmospheric River. From the USGS: "...This document summarizes the next major public project for MHDP, a winter storm scenario called ARkStorm (for Atmospheric River 1,000). Experts have designed a large, scientifically realistic meteorological event followed by an examination of the secondary hazards (for example, landslides and flooding), physical damages to the built environment, and social and economic consequences. The hypothetical storm depicted here would strike the U.S. West Coast and be similar to the intense California winter storms of 1861 and 1862 that left the central valley of California impassible. The storm is estimated to produce precipitation that in many places exceeds levels only experienced on average once every 500 to 1,000 years." http://pubs.usgs.gov/of/2010/1312/ http://pubs.usgs.gov/of/2010/1312/

anigbrowl 11y ago
Great find, thanks. The ARkStorm has several public policy implications: (1) An ARkStorm raises serious questions about the ability of existing federal, state, and local disaster planning to handle a disaster of this magnitude. (2) A core policy issue raised is whether to pay now to mitigate, or pay a lot more later for recovery.[...] I think we can all guess what the answer to #2 has been since :-(
nkurz 11y ago
An interesting report, but is there any reason to conclude that "we are due"? If the lack of rain is random (like flipping a fair coin), the expected time to event would still be 1000 years. Believing that "heads" is more likely after a string of "tails" is the classic Gambler's Fallacy: https://en.wikipedia.org/wiki/Gambler%27s_fallacy https://en.wikipedia.org/wiki/Gambler%27s_fallacy If on the other hand the current drought is caused by a change in climate, there is even less reason to believe that we are due for a gigantic amount of rain. If the coin is biased (bent) logic would conclude that one should bet that recent performance _is_ an indicator of future performance. While it's not impossible for alternation to be most likely, it requires some physical process that would explain it. Interestingly, weather in the Central California often does follow multi-week cycles, with hot inland weather leading to rising air at the coast, leading to fog flowing inland, leading to a cooldown[1]. But I don't know of any process that would explain this for century scale rainfall. Do you? [1] This article offers an explanation of the "fog cycle", but with the cautious wording "Until recent years, the conventional explanation for the fog’s behavior was a simple one". I wonder if there is now better knowledge: https://baynature.org/articles/cutting-through-the-fog/ https://baynature.org/articles/cutting-through-the-fog/
- 001sky 11y ago
  Just FYI, Utah (Desert) had the 2nd largest month of rain in itsrecorded history already this year. All that says is armchair weather prediction is silly.
- cbennett 11y ago
  "An interesting report, but is there any reason to conclude that "we are due"?" Yes, El Nino, which may bring torrents of rain this winter to the US west coast. The combination with epic drought will be disastrous, whether or not if fulfills the mythic criterion of an "ArkStorm' FYI: occurrence of rain or lack thereof is not like flipping a coin; this is more like a chaotic system with non-linear patterns evolving; once we see a large-scale pattern that occurs, and we identify it recurring through time such as El Nino, we can spot its tell-tale signs ahead of time and warn folks that worse may be on the way. Nevertheless, there are no guarantees, all we can do is wait and watch- But it certainly changes our Prior to know about these recurrent global-weather-scale patterns. http://www.aljazeera.com/news/2015/09/el-nino-set-strongest-150913093902800.html http://www.aljazeera.com/news/2015/09/el-nino-set-strongest-...
  - nkurz 11y ago
    occurrence of rain or lack thereof is not like flipping a coin Yes, absolutely. El Nino is a fine reason to believe that the pattern will change. At a decadal scale, there is reason to believe that recent drought is a predictor of future rain. My point though was that there was not (a priori) a reason to believe that "It's been 500 years since California has been this dry" would imply "we are due" for a 1000 year storm.

anigbrowl 11y ago

Great find, thanks. The ARkStorm has several public policy implications: (1) An ARkStorm raises serious questions about the ability of existing federal, state, and local disaster planning to handle a disaster of this magnitude. (2) A core policy issue raised is whether to pay now to mitigate, or pay a lot more later for recovery.[...] I think we can all guess what the answer to #2 has been since :-(

nkurz 11y ago

An interesting report, but is there any reason to conclude that "we are due"? If the lack of rain is random (like flipping a fair coin), the expected time to event would still be 1000 years. Believing that "heads" is more likely after a string of "tails" is the classic Gambler's Fallacy: https://en.wikipedia.org/wiki/Gambler%27s_fallacy https://en.wikipedia.org/wiki/Gambler%27s_fallacy If on the other hand the current drought is caused by a change in climate, there is even less reason to believe that we are due for a gigantic amount of rain. If the coin is biased (bent) logic would conclude that one should bet that recent performance _is_ an indicator of future performance. While it's not impossible for alternation to be most likely, it requires some physical process that would explain it. Interestingly, weather in the Central California often does follow multi-week cycles, with hot inland weather leading to rising air at the coast, leading to fog flowing inland, leading to a cooldown[1]. But I don't know of any process that would explain this for century scale rainfall. Do you? [1] This article offers an explanation of the "fog cycle", but with the cautious wording "Until recent years, the conventional explanation for the fog’s behavior was a simple one". I wonder if there is now better knowledge: https://baynature.org/articles/cutting-through-the-fog/ https://baynature.org/articles/cutting-through-the-fog/

001sky 11y ago
Just FYI, Utah (Desert) had the 2nd largest month of rain in itsrecorded history already this year. All that says is armchair weather prediction is silly.
cbennett 11y ago
"An interesting report, but is there any reason to conclude that "we are due"?" Yes, El Nino, which may bring torrents of rain this winter to the US west coast. The combination with epic drought will be disastrous, whether or not if fulfills the mythic criterion of an "ArkStorm' FYI: occurrence of rain or lack thereof is not like flipping a coin; this is more like a chaotic system with non-linear patterns evolving; once we see a large-scale pattern that occurs, and we identify it recurring through time such as El Nino, we can spot its tell-tale signs ahead of time and warn folks that worse may be on the way. Nevertheless, there are no guarantees, all we can do is wait and watch- But it certainly changes our Prior to know about these recurrent global-weather-scale patterns. http://www.aljazeera.com/news/2015/09/el-nino-set-strongest-150913093902800.html http://www.aljazeera.com/news/2015/09/el-nino-set-strongest-...
- nkurz 11y ago
  occurrence of rain or lack thereof is not like flipping a coin Yes, absolutely. El Nino is a fine reason to believe that the pattern will change. At a decadal scale, there is reason to believe that recent drought is a predictor of future rain. My point though was that there was not (a priori) a reason to believe that "It's been 500 years since California has been this dry" would imply "we are due" for a 1000 year storm.