6 August 2006

Long Range Hurricane Forecasts – They always make me laugh!

Posted by Dan Satterfield

The news media seems to love these long range hurricane forecasts. Dr. William Gray started forecasting the number of tropical storms and hurricanes in the Atlantic Basin over 20 years ago. NOAA in Washington has begun to make an annual prediction as well.

There is some good in these predictions. They get lots of attention, and hopefully get coastal residents thinking about what they would do if they were faced with an impending category 5, on their door step. That’s where the good ends in my opinion.

NOAA today and Dr. Gray last week revised down the number of storms expected this year. That did not surprise us in the weather office. JP, Spencer and I have all thought that it would be extremely unusual to have another record breaking year in the tropics. That said, we did, and still do expect an above average season. You will not see any forecasts like that from the WHNT weather center. Frankly, it is just not possible yet to make a prediction of how many storms will develop several months ahead of time.

A forecast of an above normal, or well above normal season, is not beyond current science, and most meteorologists I know will agree that an above normal year is still likely.

There are a bunch of factors that go into these forecasts. Some are obvious, like the sea surface temperature anomalies. If the water in the tropical Atlantic is well above normal then that would favor a more active season.

Another factor that is not so obvious, is the wind direction in the stratosphere above 75,000 feet. These winds tend to switch directions from West to East every few years. This is called the QBO or (get ready for it) the Quasi Biennial Oscillation. When the winds are strong from the East we tend to see considerably fewer tropical storms in the Atlantic and Gulf. This is likely because of the high wind shear in the Stratosphere. A Westerly QBO tends to bring an active hurricane season.

There are other factors as well, but suffice it to say- take these hurricane forecasts with a grain of salt. If you hear that we are expecting an active season- that is a forecast that will probably verify.

If you hear that we are going to have 9 hurricanes and 14 tropical storms, three of which will hit land-then do what I do-laugh.