When NOAA says “above normal,” what does it mean? (p. 2)

The hurricane season started June 1, and we were talking about the National Oceanic Atmospheric Administration (NOAA) outlook for 2011. The NOAA’s storm estimates are likely included in the data property insurance companies use in rate-setting – especially in states like Florida that are right smack in the middle of “hurricane alley.”

In our last post, we talked about the agency’s process and the statistical caveats included in the annual outlook. The agency’s “above normal” prediction for 2011, for example, is not an absolute, 100 percent certainty. The report actually says that the conditions are such that the NOAA estimates a 65 percent chance of an above normal Atlantic hurricane season.

Within that 65 percent are the specific estimates for named storms, hurricanes and major hurricanes. The NOAA says there is a 70 percent chance that there will be 12-18 named storms, 6-10 hurricanes and 3-6 major hurricanes this year. These are above average compared to the National Hurricane Center’s official averages of 11, 6 and 2, respectively.

In general, NOAA suggests that there is a better than average chance for multiple hurricane strikes in the Caribbean and U.S. Indeed, in above normal seasons – “hyperactive” seasons, to use the NOAA term — the chance of multiple hurricanes in the region increases sharply.

However, the NOAA report states over and over again that these forecasts do not include landfall. The agency warns that they cannot predict if a storm will make landfall – much less where a storm may hit. Hurricanes aren’t headstrong children that just strike on their own. Daily weather patterns determine if a hurricane will hit, and the NOAA admits more freely than your local weather forecaster that it isn’t possible to predict weather accurately weeks or months in advance.

So, yes, the season has started, and the predictions are in. The report includes two important points for Floridians.

First, these model forecasts have exhibited “limited predictive skill” so early in the year. It’s an estimate, not a sure thing.

Second, catastrophic storms hit in below normal seasons, too. It just takes one, so it makes sense to be prepared for it.

Source: National Weather Service, Climate Prediction Center, “NOAA 2011 Atlantic Hurricane Season Outlook,” 05/19/2011

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