27 January 2010

Karen Clark on Short-Term Hurricane Loss Predictions

Pielke, Roger A.



  1. Roger, what is "a concerted attack to deny access"?

  2. -1-Roddy

    This sort of thing:


    It's been down for almost a week.

  3. You must be doing something right to be attacked in this way.

  4. Thank you. Why would anyone do that? Not a terribly amusing target surely.

  5. Thanks for the sentiments. I do feel bad for my colleagues and our collected students who suffer the consequences. There is no way to know, but I suspect it has to do with my writings. One reason i moved my blogging off campus.

    Anyway, let's get back to cat models ;-)

  6. Predicting seasonal hurricane numbers with much accuracy seems like a lost cause. One can give certain estimates based on factors that, on average, increase or decrease the likelihood of storms. Total hurricane estimates are always going to be in the +/- 3 storm or so range though. The factors that go into an individual storm forming and then becoming a hurricane are too diverse and variable. We've only recently had the tools that can estimate when a tropical wave has increased chances of becoming a storm. Still, waves that look favorable often can't form a closed circulation and sometimes what seems like nothing turns into a storm in a couple of days.

    The number of factors to consider only increase when trying to predict landfall. It takes a lot to come together for a storm to be able to traverse the Atlantic without recurving or running into unfavorable conditions. Trying to predict damage and cost impacts is even more impossible. A shift of 20 miles in a storm's landfall can make billions of dollars of difference.

    I think we can make some broad estimates based on climatology. There's trends in the numbers based on various weather conditions around the world such as ENSO state, but there's high variability.

    The only thing for sure is that the more we build on the east and gulf coasts, the higher our risk will be. We've been relatively lucky over the last 50 years. Just imagine if Andrew had made landfall 20 miles further north. Miami would have seen a direct hit. Or if Katrina would have hit 20 miles further west. New Orleans would have seen a few categories higher wind damage along with the flooding. Or if Hugo had made a path closer to Charleston or Myrtle Beach. Also, when a hurricane actually threads the needle and hits NYC from the sea, the damage totals will be very high.

  7. There is apparently an amazongate now.



    The WWF has yet to provide any scientific evidence that 40% of the Amazon is threatened by climate change -- as opposed to the relentless work of loggers and expansion of farms.

  8. Hurricane numbers, like all small number events, follow Poisson statistics over the short term (lambda, the average number of storms/year, may vary over the longer term). That means the variance is the number and the standard deviation is the square root of the number. So if the average is 10 storms in a year then the 90% confidence interval is 5 to 15 storms. For an average of 5/year, the interval is 1 to 9. Over the short term then, going with the average over the last few decades will likely be as or more skillful than a pre-season prediction by other means.

  9. Mr. Pielke:

    Lets assume for a moment that forecasters have the statistical probability of hurricanes exactly correct and that the statistical damage value is exactly correct.

    The hurricane subject area aka possible damage area is a known. The hurricane subject area is currently broken up into geographic governmental entities known as states. Roughly the state of Texas along the coast eastward ending in Connecticut.

    In each of these state entities, within the subject area, we have homogeneous exposure units concentrated in a narrow geographic area. Private welfare systems aka private insurance is based on homogenous exposure units spread over a wide geographic area. In other words, violated is an axiom within private welfare systems, by concentrating exposure in a narrow geographic area.

    Insurance is a retained state right i.e. regulated state by state. Insurers pricing occurs state by state.

    However, to solve for the insurance axiom violation of homogeneous exposure units concentrated in a narrow geographic area, the state entities within the subject area need to create one larger exposure area which is basically the subject area. In other words, the coastal areas of the many and several states needs to become one large exposure area.

    Not a federal plan, rather a syndicate of the states. The states with a hurricane exposure take their coastal counties and create one insurance territory aka exposure area. We then have a much wider geographic area with homogeneous exposure units. This wider geographic area is then priced for base private insurance and re-insurance. Its an arbitrary insurance territory with the states dropping state line regulatory issues and acquiescing to the syndicate's regulatory/coverage decisions with the syndicate made up of the states.

    In summary, you have to find a way in the hurricane subject area to overcome the violation of the axiom, within private welfare systems, that homogeneous exposure units need spread over a wide geographic area.

  10. OT "Policy Question"

    What would happen if US, Russian Federation and Australia agreed to 'coal production caps'?

    In my simple mind, creating an artificially scarce good benefits the producers of those goods. Hence, "Big Coal" in the US would benefit from 'climate legislation' thru increased profitability of existing operations.