On the limits of tropical cyclone track prediction

September 28, 2020 - Recent research shows the range of skillful tropical cyclone track forecasts is expected to be extended by a day per decade in the future. The study, by scientists Feifan Zhou from the Chinese Academy of Sciences and Zoltan Toth from NOAA’s Global Systems Laboratory, was published in the Bulletin of the American Meteorological Society in September 2020.

The success story of numerical weather prediction (NWP) over the past decades is often illustrated with the dramatic decrease of errors in tropical cyclone track forecasts. In a recent essay, however, Chris Landsea and John Cangialosi (2018) note a diminishing trend in the reduction of errors in NOAA National Hurricane Center tropical cyclone forecasts as they contemplate whether “the approaching limit of predictability for tropical cyclone track prediction is near or has already been reached.”

Zhou and Toth used the same dataset as Landsea and Cangialosi to explore past trends in the reduction of tropical cyclone forecast track error and to see how such errors may be further reduced in future decades. Two of their key findings are that (1) the true forecast track error (i.e., the difference between forecast position and actual position of tropical cyclones) increases exponentially as a function of forecast days, while (2) initial and forecast errors are reduced exponentially over the years.

“Quantitatively, it takes 10 years of observing, initialization, and numerical model development work by the NWP community to reduce tropical cyclone track errors as much as the forecast error grows in one day”, said Dr. Zhou. "In other words, in 10 years' time, the forecast skill at day 6 would be the same as it is today at day 5. We estimate the one day per decade extrapolated gain in skill may hold for at least 25 years into the future. That's a long time, with lots of potential for TC track error reductions," added Dr. Toth.