Snow and availability in the Holy Land

I’ve been in Israel for the last two weeks, having been invited to give some lectures in the Geophysics department at Tel Aviv University. A major storm moved into the country yesterday, and hasn’t left yet. Here on the coast in Tel Aviv, there have been strong winds and rain. At higher elevations, there is snow, including in Jerusalem (about 800 meters, or 2500 feet, above sea level).

Here is a current map (actually a 12-hour forecast from the GFS model, valid around the present time as I write) showing the surface pressure and precipitation, with Israel in the lower right (northern Israel is right under the strong precipitation maximum):

gfs_pres_12h_eur

And here’s a map showing the upper level flow, 500 hPa geopotential height (contours) and relative vorticity (color shading); note the strong southward dip in the geopotential contours, indicating a strong distortion of the jet:

gfs_500_12h_eur

As it has turned out, the Jerusalem snow hasn’t been as big a deal as some had feared. There has only been a little so far, and it has been followed by rain washing it away. The preparations, on the other hand, had been massive, with roads and schools closed ahead of time and every level of government preparing for the worst.

The preparations for this event, when compared with last winter’s, manifestly show the role of the availability bias, as described by Daniel Kahneman in Thinking Fast and Slow, in human decision-making about risks from rare events.

One side of the availability bias is that we often don’t take risks as seriously as we should if they are risks of things that we have never experienced. This was evident, for example, in the failure of governments in the New York City area to invest in flood-proof infrastructure prior to Sandy, with the poster child being the South Ferry subway station. The new South Ferry station was completed in 2012 and totaled by the storm — despite well-documented evidence, going back at least 20 years, that a hurricane could cause just the kind of flooding that Sandy caused, in that precise spot as well as others. (See my book Storm Surge for details.) Now that Sandy has happened, things have changed and all kinds of investments are being made in more resilient infrastructure. But since until Sandy no such storm had happened in anyone’s lifetime in NYC, it was human nature to act as though it never would happen.

This Israeli storm is showing the flip side of the availability bias. Snow in Israel is relatively rare, but it happened in a big way last year. In December 2013, Jerusalem got a couple of feet of snow. It wasn’t taken seriously enough. People got in cars to drive from other parts of the country to Jerusalem to see the snow in all its novelty, and many got trapped on the road for long periods of time. The city didn’t have enough plows ready, power outages were more widespread than expected, and significant numbers of people had to evacuate to shelters. The country was taken by surprise, with serious consequences.

Not this time. Since a couple of days before the storm, the newspapers here have been full of stories about its approach and about all the government actions to get ready, including more plows, the school and road closings. The US Embassy issued a message to US citizens in Israel warning about the storm.

The forecast was for a big storm, to be sure, but not for one as bad as last winter’s. Having been through last year’s event, though, no way were those in positions of responsibility going to be caught off guard this time. When we have been through a rare and disastrous event recently, the availability bias tends to make us think it’s the “new normal”.

I am not saying that the authorities overreacted to the forecast this time. Their actions may well have been warranted, given some uncertainty in the forecast and the vulnerabilities of the region as demonstrated last winter. But it’s clear that the reaction is erring on the side of caution this time, compared to erring the other way the last.

Still, the storm has been impressive and exciting. I’ve put a short video on my facebook page showing the waves pounding the boardwalk at the Tel Aviv port, in the northern part of the city, last night.

Thanks to Pinhas Alpert for a discussion of the role of availability bias in the preparations for the present storm, to Nili Harnik for inviting and hosting me here, and many people here for accounts of last winter’s storm.

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