Discover Dialogue: Meteorologist William Gray
Eight of the last 10 years have been very active—we've never had as much activity. Yet we went from 1992 until last year with no hurricanes coming through Florida
by Kathy A. Svitil -->
Photograph by Jeff Wilson
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?
G: We don’t say where or when the storms are going to occur. We give a number for the season. It is a different prediction.
What is the point in predicting the severity of the season if you can’t say where a storm will hit, or when?
G: People want to know what the odds look like, and we can say something about that by looking at the conditions that existed before the active season in prior years and comparing those to what we see now.
A few years ago when there were quite a few light seasons in a row, you said Florida had just been lucky—and that it was going to end.
G: They’ve been extremely lucky. The last major storm to come through Florida, before hurricane Andrew hit in 1992, was hurricane Betsy in 1965, which went through the Keys. Eight of the last 10 years have been very active—in fact, we’ve never had as much activity on the records, going back to about 1870 or so, as in the past 10 years—and yet we went from 1992 until last year with no hurricanes coming through Florida. If we look back earlier, from 1931 through 1965, Florida was hit 11 times with major storms. The major storms, the category 3, 4, and 5 hurricanes, only account for about 25 percent of the number of named storms, but they cause about 80 to 85 percent of the damage.
There was a lot of devastation last year. That doesn’t seem very lucky.
G: Although last year was a terrible year for them, it could have been worse because none of the four storms that affected the Florida region went into a highly populated area.
What do you expect over the next few years?
G: Our feeling is that the United States is going to be seeing hurricane damage over the next decade or so on a scale way beyond what we have seen in the past.
Is there a reason so many storms reached land last year?
G: What made last year so unusual were the steering currents. In 9 of the previous 10 years from 1995 through 2003, we tended to have this upper-level trough—or low-pressure area—off the northeast United States, and that brought the westerly winds down into the tropics, where they curved the storms out to sea before they could hit the United States. On average, about one in 3 major Atlantic storms hits land, so by all reckoning we should have had 9 or 10 major storms hitting the United States since 1995. We only had 3 because of this trough. Last year, the thing changed. Instead of a trough off the northeastern United States, we had this high-pressure ridge, and that kept the westerly winds far north of the tropical Atlantic storms. The storms didn’t curve away; they just kept coming westward.
What will happen this year?
G: We think that this year we probably won’t curve all the storms, but we are not as confident of that as we are that this will be a pretty active year—a lot like last year.
How accurate can hurricane prediction get?
G: There are two types of prediction. The type we do is with climate, where we don’t say when and where but we say the number. I think that will get slightly better if we keep working on it. The critical prediction is in the short range, 12 to 48 hours, of the track of the storm and of its intensity. Track prediction is getting a little better because researchers have been flying planes around the outside of the storm, measuring the steering currents. The errors in three-day track prediction now are equivalent to the errors you used to see in two-day predictions. But the skill at intensity predictions is still very small. That is a tougher nut to crack because it involves the complexity of the inner core of the storm.
A few years ago, you almost called it quits because you’d lost so much funding. What made you continue?
G: I don’t have the budget that I had, so I have cut my project way back. I am in retirement. I’m still working every day, but I don’t teach and I don’t have as many graduate students and as much financial need. I’ve got a little money from Lexington Insurance out of Boston, and I have some National Science Foundation money. For years I haven’t had any NOAA, NASA, or Navy money. But I’m having more fun. Right now I’m trying to work on this human-induced global-warming thing that I think is grossly exaggerated.
You don’t believe global warming is causing climate change?
G: No. If it is, it is causing such a small part that it is negligible. I’m not disputing that there has been global warming. There was a lot of global warming in the 1930s and ’40s, and then there was a slight global cooling from the middle ’40s to the early ’70s. And there has been warming since the middle ’70s, especially in the last 10 years. But this is natural, due to ocean circulation changes and other factors. It is not human induced.
That must be a controversial position among hurricane researchers.
G: Nearly all of my colleagues who have been around 40 or 50 years are skeptical as hell about this whole global-warming thing. But no one asks us. If you don’t know anything about how the atmosphere functions, you will of course say, “Look, greenhouse gases are going up, the globe is warming, they must be related.” Well, just because there are two associations, changing with the same sign, doesn’t mean that one is causing the other.
With last year’s hurricane season so active, and this year’s looking like it will be, won’t people say it’s evidence of global warming?
G: The Atlantic has had more of these storms in the least 10 years or so, but in other ocean basins, activity is slightly down. Why would that be so if this is climate change? The Atlantic is a special basin? The number of major storms in the Atlantic also went way down from the middle 1960s to the middle ’90s, when greenhouse gases were going up.
Why is there scientific support for the idea?
G: So many people have a vested interest in this global-warming thing—all these big labs and research and stuff. The idea is to frighten the public, to get money to study it more. Now that the cold war is over, we have to generate a common enemy to support science, and what better common enemy for the globe than greenhouse gases?
Are your funding problems due in part to your views?
G: I can’t be sure, but I think that’s a lot of the reason. I have been around 50 years, so my views on this are well known. I had NOAA money for 30 some years, and then when the Clinton administration came in and Gore started directing some of the environmental stuff, I was cut off. I couldn’t get any NOAA money. They turned down 13 straight proposals from me.