Thursday, September 5, 2019

More maps

In his ongoing effort to insist that Hurricane Dorian was forecast to hit Alabama, Donald Trump tweeted a grainy image of another hurricane map. This map appears to be what’s called a spaghetti plot, perhaps with additional lines made with ballpoint pens. It’s impossible to tell.

The important point is that one has to know how to read such a map for the map to be meaningful. The Weather Channel has this to say about spaghetti plots: “spaghetti plots do not show where impacts will occur.” And:

Although most models show possible impacts, to present many models succinctly on a single chart, meteorologists generally produce spaghetti plots that usually only show the “where” and a loose representation of “when” for tropical systems.
These plots do not speak to whether a storm will bring rainfall, hurricane-force winds, surge, or other data; they just contain information about the center of a storm’s future track.
I don’t know how to read spaghetti plots, but I know that I don’t know how, and I know that there are people who do.

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