Science & Technology



National Hurricane Center gives Floridians a bigger heads up by extending tropical weather predictions to 7 days

Bill Kearney, South Florida Sun Sentinel on

Published in Science & Technology News

The National Hurricane Center is lengthening its prediction times for tropical weather formations from five days to seven days for the upcoming hurricane season, giving Floridians a bit more time to consider storm threats.

The season officially starts June 1 and runs through Oct. 30.

The NHC graphic comes in a map form, and predicts the chances of a tropical disturbance growing into a tropical cyclone over a two-day and seven-day period. Previously, the predictions were for two-day and five-day periods.

The map used different color marks to indicate if a depression has a less than 40% chance of forming, a 40-60% chance of forming and a greater than 60% chance of forming in the two-day and seven-day time frames.

A tropical depression is a cyclone with maximum sustained surface wind speeds of 38 mph or less. A tropical storm has maximum sustained surface wind speeds of 39-74 mph and a hurricane has maximum sustained surface wind speeds of more than 74 mph.

The NHC is also adding Puerto Rico and the U.S. Virgin Islands (USVI) to the areas covered by the Potential Storm Surge Flooding Map. The map previously only covered the U.S. Gulf and East Coasts. The map shows areas where storm surge could occur and how high above ground the surge could reach.


Crucial cone info

The release also included the annual update to the tropical cyclone track forecast error cone, also referred to as the “cone of concern” or “cone of death.” The width calculations of the 2023 cone will be roughly the same as in 2022.

Included is a helpful video with a crucial reminder: the image of the cone does not depict the potential area of impact, it depicts the potential path of the center of the storm, meaning the area of impact is much wider. A city could be outside the cone, but still on the “dirty” side of the storm when it comes ashore.

The NHC calculates the size of the cone based on how well they predicted storm paths in the past. The formula makes the cone wide enough to put two-thirds of historical official forecast errors over the previous five years (2018-2022) within it.

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