April 2016 Archives

Forecasting Heat Waves (Wherein my Honour is Challenged)

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Meteorologists can forecast weather remarkably well out to about a week. Climate scientists can forecast climate out to 50 or 100 years. There's a tantalizing gap between those two time scales--the monthly to yearly forecasting. Why can't we forecast something like heat waves a couple of months in advance?

The answer to this question is complicated, involving intimate ties between space and time, but in breaking news...actually we can. Yes, it turns out, we can forecast heat waves two months out. Well, at least, we can forecast the likelihood of a particular heat wave based on a specific ocean temperature pattern. It's a special case. Here's the summary:


The challenge with forecasting at this time scale is that we don't have general rules or equations to follow, like we do with short-term weather and long-term climate forecasting. We have to work on a case-by-case basis. In a way, everything is a special case. So we have to look for cues. For the specific heat wave pattern in the above article, scientists have found the right collection of cues that seem to be consistent. The GMRI lobster forecast is another good example: April water temperatures turn out to be an excellent cue for where lobsters will be in the summer. So there we have a useful forecast a few months in advance.

Meanwhile, other mid-range forecasts are still tricky, and scientists sometimes disagree. Take this recent article in the Portland Press Herald:


One scientist--the highly acclaimed Dr. Pershing of the Gulf of Maine Research Institute--says that "We're pretty much locked in now to 2012-like conditions." If you think back to 2012, that was the year we had an ocean heat wave 3 degrees above normal that lasted 18 months (continuing into 2013) and covered the northwest North Atlantic. On the other hand, further down in the article, the more obscure Dr. Record says, "It's more likely at this point that we'd have a warm summer and a heat wave than in a typical year, but it isn't guaranteed." 

When scientists disagree like this, you would think we would settle it with a math-off or a phylogeny bee. Typically, though, it's a wager over beer. In this case, Dr. Pershing has wagered a beer that July 2016 will be in the top two warmest July's since 1982. Naturally I have accepted the wager. Hopefully we'll have time to give some odds as the month approaches so that you can look on as I build toward a frenzy of excitement, triumph, and beer consumption, or whither in a spiral of humiliation and beer consumption.


2016temp.jpg
For reference, this figure shows the surface water temperature through the end of March at a mid-coast buoy. The blue line shows the average condition, and the shaded area is the historical range. It's tracking quite warm, but it's a long way to July.

 - Nick Recørd, signing off

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