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How to read a National Hurricane Center cone forecast

Everyone looks straight at the track of the storm when lots more can be garnered

Super wide cone means lots of uncertainty
Super wide cone means lots of uncertainty

JACKSONVILLE, Fla. – There has been an ongoing inside conversation within the Weather Authority Team about the National Hurricane Center’s track forecast the past two days, at times showing a track right into the northeastern Gulf of Mexico and then possibly into Northeast Florida (Jacksonville area).

The challenge was, the two main forecast models (the European forecast model and the Global Forecast System, known as the GFS) were not saying the same thing. Instead, the GFS was suggesting a track to the west that would keep Eta from ever reaching the U.S. Gulf Coast. The GFS also strongly suggested that Eta would fade away in about five days. Meanwhile, the Euro had been suggesting a stronger Eta that would track into the Northeast Gulf of Mexico and then into southern Georgia.

It appeared the National Hurricane Center was splitting the difference, something I have found doesn’t always pay off. It does tend to pay off when both models are in similar patterns but have some timing differences. This time there are significant positions/tracks.

Anyhow, here’s how to read a “cone” forecast from the National Hurricane Center: Watch the width of the cone. The wider the cone, the more uncertainty there is in the National Hurricane Center’s forecast. The more narrow, the more confidence they have in their forecast.

Below are images illustrating this and how the two main models are now.

Note at the beginning of the track, the cone is rather narrow.
Note at the beginning of the track, the cone is rather narrow.
Note how wide the end of the forecast shows. Looks like a bulb which means the NHC has low certainty on their forecast
Note how wide the end of the forecast shows. Looks like a bulb which means the NHC has low certainty on their forecast
Plus the forecast from the ETA forecast model, notice how far to the southwest Eta is forecasted to be
Plus the forecast from the ETA forecast model, notice how far to the southwest Eta is forecasted to be
The forecast from the EURO forecast model, is closer to the official track from the National Hurricane Center, but still west of the official track.
The forecast from the EURO forecast model, is closer to the official track from the National Hurricane Center, but still west of the official track.

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