Why Hurricane Track Forecasts are Much Better that Intensity Predictions

Tropical Storm Milton is now a hurricane heading for Florida's west coast.

As I will describe below, there is great confidence in the hurricane's future track but substantial uncertainty in its future strength.

Why the difference?  That is the topic of this blog.

Let me start by showing you the latest track forecast for this storm from a variety of forecast systems (see below).  All are taking the storm into the central portion of West Florida.

Not only are the track forecasts on the same page, but the verification of historical hurricane track predictions shows amazing skill and great improvement over time (see official National Hurricane Center forecast verification below). 

Around 1970, 72h-forecasts were typically off by 450 nautical miles.  Today the error is only about 75 nautical miles.   Very impressive.

So if you are anywhere on the central western side of Florida,  you better get prepared.  Now.

By what about the predicted intensity of this hurricane, which is now rapidly intensifying? 

There is some uncertainty in the future intensity, as shown by the predicted maximum wind speed (knots).   As shown below, some forecast systems intensify the storm into a very dangerous category 5 terror, with sustained winds over 140 kt, while others (blue line), keep Milton to a weaker, category 2.

Historically, skill improvement for intensity has been more modest than track (see below).

So why are track forecasts generally better than intensity forecasts?

To forecast the track of a hurricane, the critical issue is getting the winds around the storm correct.  Hurricanes are heavily steered by the larger scale wind currents and meteorologists have gotten very good in such predictions.

Why so good?   We have satellite data everywhere to start.   The U.S. has aircraft that fly out around the storm, dropping instrument packages, called dropsondes (see below), providing detailed, three-dimensional information around hurricanes.

With excellent computer models and extensive data, we can make skillful predictions of where storms are going.

But forecasting hurricane intensity is much, much harder.   Hurricanes are complex creatures, with intense bands of convection (thunderstorms) that play essential roles in providing heat and moisture to the developing systems (see far image of a hurricane below).

To simulate such rainbands requires very high-resolution models (very expensive) and getting essential physics correct, some of which we don't understand well.   For example, how breaking waves interact with winds to inject moisture into the storm.  

The complexity of the physics inside hurricanes makes the simulation of hurricane structure and intensity a very difficult problem.  We are making progress, but it is slow.

In any case, there is clearly a grave threat to Florida, with the landfall of Milton expected on Wednesday.  

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Announcement:  Free Public Lecture at Kane Hall on October 10:  Global Warming, the Jet Stream, and Cold Waves

All of you are invited to attend what should be an excellent public lecture by Professor Jonathan Martin on how global warming affects the jet stream and cold air outbreaks.

It will be a timely and interesting lecture accessible to non-meteorologists and given in honor of UW Professor Peter Hobbs.

The talk will be at 7 PM in Kane Hall room 210.

If you would like to go, please register online here:

Parking is available (at a modest cost) in the UW Central Garage, which is located directly under Kane Hall.  Or take the light rail (the UW stops are a 5-10-minute walk away).