Extreme event attribution

I have not been keeping up here the last few months. To start the catching up process:

During the fall and winter I was part of a committee convened by the National Academies of Science, Engineering and Medicine to perform a study on extreme event attribution. This is the science of making specific, quantitative statements about how a specific individual weather event was influenced by human-induced climate change. It was a wonderful experience working with my colleagues on the committee, most of whom I hadn’t known before, and (not having previously worked on attribution myself and thus not being an expert in it before we started) I learned a great deal. Not just about the subject matter, either – tt was my first NAS committee and very informative to see how the sausage is made. We think the report came out very well, and it seems to have been well received.

The report itself is available for free online in electronic form; hard copies cost money (and aren’t available yet). I wrote an op-ed for the Washington Post’s Capitol Weather Gang (thanks Jason Samenow!) to express some of my own perspective in a more informal way. Climate Central Chief Scientist Heidi Cullen wrote one for the NY Times, and my colleague on the committee (and former AMS President) Marshall Shepherd wrote one in Forbes. There was lots of other media coverage, easily found through your favorite search engine; here’s a piece on the Lamont web page by Stacy Morford.

On Thursday, April 7, I’ll be speaking at an event about the report with committee chair Rear Adm. Dr. David Titley and AP science reporter Seth Borenstein, moderated by Heidi Cullen, at the NAS Koshland Museum.

December 2015’s crazy weather

I’m in Oregon, where December has broken rainfall records east of the Cascades, and the Cascades themselves are deep in snow. I got to see some of it up by Mt. Hood yesterday on a Christmas Day family cross-country ski outing.

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Though that was beautiful, I’m still sad to be missing the record-breaking warmth back east. (I like warm weather; it’s not an accident that most of my research over my career to date has been about tropical meteorology.) To help myself experience it vicariously, I wrote an op-ed piece for CNN about what the probable causes are. It has even been translated into Spanish.

Mumbai and Chennai

Last week I had an op-ed piece in the Times of India. It’s about the risk to the city of Mumbai from a tropical cyclone landfall and storm surge.

Mumbai is on the Arabian Sea, where tropical cyclones are relatively rare, and the city hasn’t been struck by a serious one in a very long time – well beyond living memory. If it were, though, the results could be catastrophic, as it’s both very low-lying and heavily developed right to the shore. This is exactly the recipe for an awful disaster: high vulnerability, low awareness of the risk.

I had the opportunity to write this thanks to an invitation from the great writer Amitav Ghosh, who was the guest editor for this issue of ToI. I was thrilled to get an email this past summer from Amitav, in which he said that he had enjoyed my book Storm Surge and wanted to talk to me about climate change and the risk to Mumbai. This was related to a series of lectures he was to give (now has given) at the University of Chicago in which climate change is a central theme, and which will be turned into a book in due time.

Amitav and I subsequently met to discuss the science of climate change and tropical cyclones in my apartment in New York as he was making his way to Chicago. By this time I had begun making my way through his books. They are wonderful. Themes of history, environment, ecology, and climate are woven through them, and cyclones figure prominently as plot elements in at least a couple. I got several copies signed.

So now the op-ed has come out. (The issue also has an interview with Amitav himself, and a piece by Christian Parenti on the relationship between climate and Naxalite violence in India.) Coincidentally, my piece on hypothetical flooding of Mumbai appeared at the same time as a new burst of extreme rainfall was causing very real flooding in Chennai, on India’s opposite coast.

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Infrared satellite image from November 17, showing a disturbance that one of the earlier waves of flooding in Chennai.

The Chennai flooding had begun a couple of weeks earlier, when cyclone BOB3 (“BOB” stands for “Bay of Bengal” – this storm was never strong enough to get a proper name) came ashore. This is the storm that had formed in the Bay of Bengal while cyclone Megh was in the Arabian Sea, heading for Yemen. Some forecast models predicted that BOB3 would cross the subcontinent and reach the Arabian Sea itself. But it didn’t do that. It hung around over land as a disorganized disturbance, dumping lots of rain.

Then another major burst on December 1 – a foot of rain fell on that one day. This after 40 inches in November (from BOB3 and a couple of other storms) – three times the average in Chennai for that month, and about equal to New York City’s annual average.

While it was a tremendous amount of rain, some argue that the flooding was made much more severe by careless development of Chennai in recent years, as floodplains and drainage channels have been paved over. The story is similar in Mumbai, where destruction of mangroves and river channelization have been blamed for similarly exacerbating the flood which occurred there in 2005 (also driven by rain, not storm surge, nor related to a cyclone) – and will similarly make things worse if, someday, a cyclone causes a major storm surge there. And to New York City, for that matter, where real estate development is now hot again in some of the areas worst hit by Sandy. I don’t know that op-eds or books can make much difference in the face of such indifference to risk, but it’s worth trying.

Patricia’s ultra-fast intensification

I have a piece in CNN today about the incredibly fast jump that Hurricane Patricia made from tropical storm to what some people are saying should be called “category 7”. I point out that this case shows vividly why we need advances in the science of hurricane intensity prediction, at the same time as funding for this work was severely cut earlier this year. And, I compare Patricia to The Hulk.

Earlier, before landfall, Allison Wing and Chia-Ying Lee wrote an expert but accessible analysis of what the storm was doing and how the forecast models failed to capture it.

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Sudden excitement in the forecast

Update: Tropical Depression Eleven has already been upgraded and is now Tropical Storm Joaquin.

Some weather models shifted their predictions today from what they had been just before. Now New York City, along with much of the rest of the northeast US, is in the headlights of a weather event with some potential. We are now in the forecast cone of uncertainty of a tropical cyclone: currently it’s Tropical Depression Eleven, could intensify to become Tropical Storm Joaquin. Here is the track forecast map from the National Hurricane Center:

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There is still quite a lot of uncertainty with this system, with the GFS model predicting it to be less likely than the ECMWF does that we’ll be hit by this storm. There are faint echoes of Sandy in that model disagreement – the EC predicted landfall earlier than GFS did then too. It doesn’t look like Eleven/Joaquin stands much chance of becoming an event of that magnitude, though, at least not as a wind or surge event (though never say never, or at least not yet).

There does seem to be good potential for heavy rain. Maybe very heavy, as tropical moisture funnels up from the south into a cold front that will be hanging around our region for a few days. NOAA’s precipitation forecast for the next five days puts over five inches of rain on a very large stretch of real estate from the Mid-Atlantic up to northern Maine:

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Some model runs are producing numbers as high as double that – around ten inches – for NYC. This is perhaps unlikely, but possible.

The media is starting to pick up on this. Jason Samenow of the Capital Weather Gang has a nice summary; Weather.com has picked it up; and here is a local NYC TV take on it. From a quick scan, this coverage looks reasonable. It’s giving a sense of what the more extreme outcomes could be, while clearly stating that the uncertainties are still significant. This is as it should be. This is in the “stay tuned” category.