A Past Example of the Cone of Uncertainty

Yesterday’s blog explained how the National Hurricane Center’s (NHC) “Cone of Uncertainty” is created.  Let’s look at an example of how to make use of the cone at the longer time periods.

Hurricane Ike was one of the most memorable hurricanes from the 2008 hurricane season.  It became a Category 4 hurricane over the central Atlantic, directly impacted the Turks and Caicos Islands and the southeastern Bahamas, much of Cuba, and caused extensive damage across parts of the northwestern Gulf coast making final landfall on the north end of Galveston Island, Texas as a strong Category 2 hurricane.  The NHC’s total damage estimate for the United States from Ike is $19.3 billion, making Ike the fourth costliest hurricane on record in the U.S.

Let’s look at the Cone of Uncertainty issued at 11:00 pm EDT Wednesday, 3 September 2008.

Ike Cone from 11 pm EDT Wed 3 September 2008

Ike Cone from 11 pm EDT Wed 3 September 2008

In this example, the cone was barely touching South Florida.  Ike was a Category 4 hurricane at the time and was also forecast to be a Category 4 hurricane with the most likely center location in the central Bahamas in 5 days.

So what should the response have been at the time of that forecast if you lived in South Florida?  I say that when the cone first moves over your location at the extended time period of 5 days, you should simply start thinking about what you would do if the threat continues to increase.  In the above example, the cumulative probability of hurricane force winds for the 5-day period was the same in Palm Beach, Miami and Marathon and that probability was only 3%. 

Ike made one landfall as a Category 4 hurricane near Cabo Lucrecia, Cuba but then weakened over the island of Cuba and was a Category 1 hurricane just off the south central coast of Cuba in 5 days from the time the above forecast and graphic were issued.  The lower Florida Keys eventually reported winds to tropical storm force that caused some beach erosion and downed some tree limbs, but no major damage was reported there or elsewhere in South Florida.

Best track of Hurricane Ike 2008

Best track of Hurricane Ike 2008

Some forecasts from the NHC will be better than they were on this one example of Ike, and some will be worse.  My point is that we should not get overly stressed when the 5-day cone first comes over our location.  Remember that the original intent was for people to simply start thinking about what they would do if the threat continues to increase.  That is not hard to do as long as you already have a hurricane plan.


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