Hurricane Irma continues to move west-northwest toward the Straits of Florida at a good clip, about 16mph. At this rate, the storm remains only about 60 to 72 hours from reaching the southern Florida coast, if it indeed makes landfall there. The National Hurricane Center's updated track forecast for the storm as of 11am ET is shown below.

The gallery below provides information about the last 10 track forecasts from the National Hurricane Center (they are updated every six hours), going back to the morning of Tuesday, September 5. At that time, the professional forecasters at the Miami-based hurricane center had the storm moving into the Florida Keys, between Southern Florida and Cuba, early on Sunday morning.

As we get closer to this weekend, the logical question becomes "how much can we trust these track forecasts?"

National Hurricane Center

National Hurricane Center

National Hurricane Center

National Hurricane Center

National Hurricane Center

National Hurricane Center

National Hurricane Center

National Hurricane Center

National Hurricane Center

National Hurricane Center

Consistency

The first key when judging a track forecast's accuracy is to consider the consistency of the predictions. Has the five-day forecast jumped around from, say, Pensacola, Florida to Miami, then to Charleston, South Carolina and back to Miami? In this case, the answer is decidedly no.

Between 5:00am ET on Wednesday and 11:00am ET Thursday (a total of six forecasts), the official forecast track has only moved slightly from Key Largo to Miami to West Palm Beach and back to Miami. In terms of east-west distance, that's only about a 30-mile shift in terms of a Florida "landfall." That is a highly consistent forecast, which lends confidence to the forecast.

In addition, the world's best forecast system, the European model, has been pretty consistent since Wednesday morning about a landfall in the vicinity of the Everglades, Key Largo, or Miami. The latest run of the European model (12z, Thursday, published around 2:30pm ET) brings a powerful hurricane into the Florida Keys near Marathon and pulls the center into the Florida peninsula over the Everglades and north through the state.

Error trends

The second factor to consider when judging a forecast is time to landfall. In this case, depending upon the future forward speed of Irma, we are probably about 60 to 72 hours from the storm reaching the vicinity of Florida. For this kind of time frame, the errors are less than half that of a five-day forecast.

The graphic below is part of a report produced annually by the National Hurricane Center to assess its performance and that of the computer models it uses. In it, we can see the average "official forecast" track error of a storm at Irma's present time from a Florida landfall is about 75 miles. My suspicion is that, because of the consistency in the track forecasts and computer models to date, Irma's final error will probably be lower than that.

But still, with hurricanes, location matters a lot. For example, if Irma turns north sooner and the storm's center remains even 30 or more miles offshore of Miami to the east, it would spare the city from catastrophic storm surge and some of the worst winds. Such a move would be the difference between widespread devastation and just really bad conditions.

Unfortunately, the best forecasters and global models predict the storm will probably make a final landfall over Miami or, in the European model's case, to the west of there. Obviously, this is pretty much a worst case scenario, so we can hope, for now, that the computers are wrong. As ever, hope for the best and prepare for the worst.

Curious about how the forecasters at the National Hurricane Center get the latest on what Irma and other hurricanes are doing? We visited the Mighty Hercules, one of the US Air Force's "slayers of hurricanes," last year. Learn how hurricane hunters stay in the air for 18 hours and fly through 175mph winds to deliver fresh data to meteorologists.