Anniversaries cause pause for reflection, celebration and sometimes somber remembrance. Anniversaries also are a time to stop and assess growth or progress. We just passed the 25th anniversary of Hurricane Danny, a prolific rain producer that left over 3 feet of rain around the Mobile Bay area July 18-20, 1997. It was a low-end Category 1 hurricane that seemed to just park in place.
For our region, it was unique in that it started in the Gulf and then arrived from the southwest as a hurricane. Aside from record rainfall and extreme river flooding, Danny is remembered for the strong north wind on the north end of Mobile Bay blowing the water southward to reveal the muddy bottom. Danny also stands out as being the only named storm in 1997 to make landfall anywhere in the Atlantic basin in an overall quiet hurricane season. Danny reinforced the idea that no matter how many or how few tropical systems form, it only takes one to be a problem.
Reflect on where hurricane forecasts from the National Hurricane Center (NHC) were in 1997 compared to where they are now. In 1997, the hurricane forecast cone only extended three days out. On the third day, the average amount of error in a location forecast was around 265 miles, even though Danny’s forecast was more accurate than that. In the last five years, the average amount of location error in a three-day forecast is down to 105 miles. Since Hurricane Danny, the average three-day location forecast has become two-and-a-half times more accurate.
A five-day forecast now is more accurate than a three-day forecast was 25 years ago. Read that again. A five-day forecast now is also as accurate as a two-day forecast was 25 years ago. That is outstanding progress. It’s a tremendous achievement enabled by research, technology, modeling, stronger computers and experience. That forecast improvement is like taking the field goal record of a kicker at 30 yards and then finding another kicker who is consistently better at 50 yards, and nearly as good as a kicker at 20 yards. Remember that statistics are averages. All kickers and prognosticators will miss from time to time.
Twenty years ago, the NHC forecast cone increased from three days to five days. For the last four years, the NHC has been doing experimental seven-day forecasts, but not for public release. I haven’t seen the accuracy of the data, but I would expect a seven-day forecast cone to become standard within a decade.
This would benefit communities, countries, companies and agencies with the option of additional pre-planning. The downsides of a seven-day forecast cone would be the confusion generated when multiple cones overlap and the amount of change that might occur on the sixth and seventh days. Plus, that’s more time to worry and wonder, procrastinate and forget that in the seven days that we are tracking a storm, other storms can form from nothing.
Alan Sealls is chief meteorologist at NBC 15, and an adjunct meteorology professor at the University of South Alabama.
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