Forecasters routinely get blamed for simply blowing hot air. But nobody accuses the National Hurricane Center of anything of the sort. As the team in Miami merges forecasting art with a downpour of science, residents across the entire East Coast rely on their information to know how to protect their homes. And to know when to flee.
Already, the National Oceanic and Atmospheric Association’s National Hurricane Center has one correct forecast: a bevy of early storms over the Atlantic Ocean. And while much of the world hasn’t taken notice of the blustery season until now—Hurricane Irene is the first storm to reach hurricane status this season—this season already boasts nine storms, a pesky number for so early on.
Hurricane Irene has already struck Puerto Rico, could be felt Wednesday in the Bahamas and could strengthen all the way to a Category 4 storm before its predicted landfall in the southeastern U.S. by the end of the week. The Carolinas and the Washington area sit in the forecasted path, but don’t rule out a stormy impact for more states on the East Coast. Eric Blake, a hurricane specialist with the National Hurricane Center, says a combination of factors have already contributed to a rise in storms in 2011. He discusses forecasting hurricane seasons with TIME.
When is the hurricane season, and what does an average season look like?
August through October is the busiest time, and September is the peak month. But we can still see damaging landfalls in October and it is not out of the question to have a hurricane into November. An average season has about 12 storms.
How has the early season played out?
Things are going as expected. We have already had nine storms and a lot of seasons don’t have nine (the official National Hurricane Center seasonal averages are for 11 named storms, six hurricanes and two major hurricanes). We are on track for the active season we forecasted.
What factors lead to an active season forecast?
There are a variety of factors. One of the things is, how warm is the Atlantic Ocean? How warm is it compared to an average year? The other factor is the status of El Niño. El Niño has a tendency to cause large-scale sinking air over the Atlantic Ocean and increased vertical wind shear (two elements that diminish the risk of a hurricane). In neutral and La Niña, the reverse tends to be true. Those are kind of the two predictors we look at year to year.
Has the Atlantic Ocean been unseasonably warm?
Year after year over the longer term of 20 to 30 years, we have seen the Atlantic warmer than average, mostly due to sea-surface temperatures. (The National Hurricane Center reports that sea-surface temperatures in the Main Development Region are reading as the third warmest on record, and models predict a continuation of “very warm” temperatures through the hurricane season. This is all with the possibility of La Niña redeveloping.)
What changes a forecast once the season starts?
Things can happen on a shorter term. The Madden-Julian oscillation (the fluctuation of atmospheric pressure over the hurricane’s developing areas that can quickly turn a dry and non-windy region into a wet and windy one) sometimes causes the season to be active and then stop. Usually at this time of year, we are looking at the region as the Atlantic warms up and becomes increasingly less stable. Now is the time of year (when) there is not a lot of vertical wind shear and the seas are quite warm. We are set up for a peak.
Do you gauge the power of a season on quantity or intensity of storms?
Actually both. The strength and duration of the storms is the formula we use and we combine them into Accumulated Cyclone Energy. If you get 10 short-lived storms, a couple of big ones count a lot more.
Are some seasons harsher in some specific areas and therefore lighter in others?
There has been some tendency for areas to be hit in North Carolina in one season, but it is hard to know. It is dependent on the steering currents, and those can be quite changeable in some years. Really, they can change in just a few days.
Have there been any surprises about this season?
There are always things that are a little unexpected. We had a lot of storms that didn’t make hurricane status early on. It will be easier to assess the season after we have hit the middle of it.
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