NOAA's Hurricane Forecast Calls for More Active Season

By Michael D. Lemonick

We’re now halfway through the 2012 Atlantic hurricane season, and the National Oceanic and Atmospheric Administration (NOAA) has updated its projections for overall storm activity. By the time the season ends on November 30, NOAA reports we should see a total of 12-17 named storms (that is, storms with sustained winds of more than 39 mph), of which 5-8 will be hurricanes (74 mph-plus) and 2-3 could be major hurricanes (winds above 111 mph). 

An infrared satellite image of Ernesto, which was upgraded to a Category 1 hurricane on Tuesday.
Credit: NOAA

That’s an increase from the preseason estimates issued last May (9-15 named storms, 4-8 hurricanes, 1-3 major hurricanes), and just like a political poll, the further along you are in the season, the more reliable the forecasts are. According to a statement by Gerry Bell, lead seasonal forecaster at NOAA’s Climate Prediction Center, in a press release, the upgrade comes “because storm-conducive wind patterns and warmer-than-normal sea surface temperatures are now in place in the Atlantic.” Heat from the ocean is where hurricanes get their energy, while winds blowing in different directions or at different speeds at different altitudes, a phenomenon known as wind shear, can keep hurricanes from forming.

The increase in expected tropical storms is somewhat surprising, given that climate forecasters expect an El Niño to develop in the Pacific in August or September. The warm Pacific temperature that comes with this recurring climate pattern tend to increase wind shear in the Atlantic, among many other climate effects, so all other things being equal, you’d expect fewer storms. But, Bell said, “we don’t expect El Niño’s influence until later in the season.”

In addition to ocean heat and wind shear, forecasters point to the active first half of the 2012 season as a reason to expect plenty more storms. So far, we’ve seen six named storms (Tropical storms Alberto, Beryl, Debbie, Florence and hurricanes Chris and Ernesto). Historically, an active first half of the season tends to be followed by an active second half.

Another way to look at the forecast upgrade is that while the chance of a near-normal hurricane season (12 storms, six hurricanes, three major hurricanes) remain at 50-50, just as they were in the spring, the likelihood of an above-normal season have jumped to 35 percent, while the chance of a below-normal season has dropped to just 15 percent.

A hurricane forecast is also like a political poll in that even when it comes late in the game, it’s not foolproof. There could be fewer storms than forecasters expect, and even if we end up with several major hurricanes, the impact won’t be great if they stay far from populated areas.

And it’s also worth noting that the quietest of seasons can still be deadly. Back in 1992, there were relatively few tropical storms — but that’s also the year the Category 5 Hurricane Andrew slammed into Florida, causing more than $26 billion in damage. It was the third costliest tropical storm in U.S. history.