Austin (KXAN) — Tracking Hurricane Ian has been a challenge for forecasters at the National Hurricane Center. With each update since late last week, it became more and more obvious that the hurricane would hit on the Gulf side of Florida. The question was where?
There was a time during the weekend in which the projected landfall was in the eastern Florida Panhandle around Apalachicola. With each succeeding advisory from the NHC, the projected landfall kept shifting to the south and east.
When you watch the forecast track of the hurricane you see a couple of things. One is the icon with a number inside. That number is the current strength of the storm based on the Saffir-Simpson scale.
But you also see an expanding cone that gets wider further into time. This is what makes up the Cone of Uncertainty. It represents the probable track of the center of the cyclone. It is a prediction five days out from the most recent position of the storm.
In the example above, within the cone, the M stands for Major Hurricane. S signifies Tropical Storm and D shows the storm has weakened to a Tropical Depression by the time it will reach the Carolinas. Do notice how the cone expands going into the weekend.
Like predicting the forecast high and low, or rain potential, as you go out in time there is a margin of error that occurs. For example, in the 7-Day Forecast, there is a potential greater margin of error by the time you get to the seventh day, then there will be in the first few days. That’s the same with the Cone of Uncertainty.
Hurricane forecasters suggest that the margin of error could be as much as 200 miles by the fifth day. It can be less or more.
The NHC also must consider two pieces to the puzzle, including the motion of the storm, because it will turn sometimes earlier than expected. Also, a consideration is given to the storm slowing down or speeding up. The two working in tandem will move that cone one way or the other.
According to the National Hurricane Center, forecasts since 2017 have shown “the entire track of the tropical cyclone can be expected to remain within the cone roughly 60-70% of the time.”
The cone has nothing to do with a storm’s strength.
It is an important tool in predicting where a landfall will be. But, more than that, the Cone of Uncertainty gives emergency management and other officials a better snapshot when it comes to protecting its citizens.