Meteorologist William Gray may be the world’s most famous hurricane expert. More than two decades ago, as professor of atmospheric science and head of the Tropical Meteorology Project at Colorado State University, he pioneered the science of hurricane forecasting. Each December, six months before the start of hurricane season, the now 75-year-old Gray and his team issue a long-range prediction of the number of major tropical storms that will arise in the Atlantic Ocean basin, as well as the number of hurricanes (with sustained winds of 74 miles per hour or more) and intense hurricanes (with winds of at least 111 mph). This year, Gray expects more activity, with 15 named storms, including 8 hurricanes. Four of them, he says, will be intense.
How did you get involved in predicting hurricanes?
G: It was an outgrowth of my teaching. We always wanted to know when we went to Florida whether the Atlantic basin would have an active season or not, because it has the most variable season of the global basins. There are some years with very few storms and other years with a large number of them. Twenty-five years ago, there was no way to tell. We tried studying local variation in the sea surface temperatures in the western Atlantic, the surface pressures, the wind shears, and various other things, but we could not develop a scheme that worked very well. Then I discovered that the secret was to look globally. I found that if there is an El Niño in the Pacific, the Atlantic seasons tend to be rather weak; if there is not an El Niño, they tend to be stronger. Then we found that if the global stratospheric winds blow from the west, we tend to have more storms. We looked at West African rain—we hadn’t been doing that—and found that had a precursor signal to it too. The more we learned, the better the predictions got.
How can you predict hurricanes six or nine months in advance but not the weather next week?
