In August of 2011, Tropical Storm Irene became the worst storm to hit New York since 1972. A year later, Hurricane Sandy made Irene look like a drizzle, and Governor Andrew Cuomo referred to the danger posed by the massive storms as the "new normal." So it was hardly comforting for New York, still largely unprepared for another Sandy, when the National Oceanic and Atmospheric Administration predicted in May that there was a 70 percent chance this year's hurricane season would be more active than normal, with three to six major (category three or higher) storms.
Then ... nothing happened. With the season winding down, there have been twelve named storms, two hurricanes, and not a single major hurricane to date. On the surface, it may seem like an embarrassing miscalculation for NOAA. But one of the agency's lead scientists thinks it's just proof that you shouldn't pay attention to hurricane forecasts to begin with.
"They're interesting from a science standpoint, but from a practical standpoint, it just doesn’t matter," James Franklin, branch chief of the National Hurricane Center's Hurricane Specialist Unit, said of the seasonal forecasts. "It effects how many shifts we’re going to work here and how busy we’re going to be, but it certainly doesn’t mean anything to a coastal resident."
In this particular case, the culprit of the inaccurate forecast was an atmospheric dynamic called sinking air.
"What that does, when the air sinks, particularly in the upper levels of the atmosphere, is it dries out the upper levels of the atmosphere and makes the atmosphere very hostile to thunderstorm activity," Franklin explained to Daily Intelligencer. "And thunderstorms really can’t develop, and that is the lifeblood of tropical cyclones. Tropical cyclones need thunderstorm activity to release the heat that they gather from the ocean, and it allows pressure to fall and it allows wind to increase."
Consequently, while the number of storms predicted was on target, "They just didn’t find an environment that was conducive to go on and become strong," Franklin says. "So we had lots of weak systems that didn't last very long."
Why the air sank is a mystery, however, even to Franklin and his NOAA colleagues. "There are things about the seasonal forecasting that we don’t fully understand," Franklin acknowledges. "I don't think we actually have a good understanding of why we had all of that sinking motion in the Atlantic."
Sinking air or no sinking air, one quiet hurricane season hardly means that New York can let its guard down. "Anybody who lives in the hurricane vulnerable area — including the entire Atlantic coast — is at risk, and really shouldn't conclude anything about what happened this year or last year or the year before," Franklin says.
In fact, he'd prefer it if the average citizen stopped paying attention to hurricane-season forecasts entirely and simply prepared for the worst. Because regardless of whether they call for a strong season or a weak season, (a) that doesn't tell us anything about where the storms will go, which is pretty important, and (b) it only takes one storm to devastate a city.
"I would be delighted if, as a result of this forecast not turning out too good, that people didn’t pay quite as much attention to it next time," Franklin says.