Are You Reading Hurricane Forecasts Correctly?

Posted by Stephen Petrey on Friday, August 30, 2019

As Hurricane Dorian quickly approaches, it’s time to revisit the hurricane forecast maps. We often forget that these storms are highly complex systems, that can grow and contract and can move across hundreds of miles fairly quickly. Shouldn’t our weather projection maps communicate that complexity? Perhaps, that’s a tall order. As an primer, this was the forecast projection map for Hurricane Maria in 2017:

The great tragedy of these sorts of maps, is they communicate a very compressed amount of uncertainty. The paths these hurricanes can take can vary wildly around small meteorological variables. They’re simple and offer a condensed overview of the uncertainty of the storm (over time) without the baggage of demystifying a map legend and fraying model paths. While the cone projection maps condenses information, the spaghetti projection map illustrates the ensemble of projections:

Both the cone and spaghetti maps are helpful for adjacent government planning. But neither really communicate the size or intensity of the storm, and that misinterpretation can be fatal — The Time reports:

Studies show that some people misinterpret the map as indicating the hurricane getting bigger over time. Others think it shows areas under threat. Research by Hurakan, a University of Miami team I’m a part of, suggests 40 percent of people wouldn’t feel threatened if they lived just outside of the cone.

The NWS does publish wind projection maps. Again, we’re looking at Hurricane Maria, which easily illustrates the destructive wind speed that pummeled Puerto Rico along its path in 2017:

It’s instrumental to look at all the projections available to you, to collectively assemble a full picture of the storm ahead. This method of forecasting multiple models (known as ensemble forecasting) isn’t new either. It’s regularly used for tornado and severe storm predictions as well.

Further Reading:


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