The overall track forecasts on Hurricane Bill from the National Hurricane Center (NHC) were, in my opinion, outstanding. Accurate and consistent computer model guidance to the hurricane center helped provide confidence in these forecasts.
However, it should be noted that the steering currents affecting Hurricane Bill were very well defined. This will not always be the case for future tropical storms and hurricanes. For decades, the NHC has verified every tropical cyclone forecast it has produced. These verifications can be found on the NHC web site under Forecast Accuracy. I can assure you that the NHC forecasters want people to understand the uncertainty involved with their forecasts.
The above graphic (courtesy of NHC’s James Franklin, Branch Chief, Hurricane Specialist Unit) shows Atlantic 5-year mean errors for both track and intensity. Note that the black line shows the official tropical cyclone track errors increase by about 60 miles (50 to 55 nautical miles on graph) per day on average based on National Hurricane Center data from the previous five years. That means, for example, that a hurricane could be forecast to make landfall at Miami Beach in 24 hours, and it could easily make landfall near Palm Beach to the north – or near Tavernier to the south.
And the 5-day average forecast error is around 300 miles. That is a lot of uncertainty and we need to be aware of this.
My next few blogs will be on track forecasting. We will get to intensity forecasting after that.