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Conversation with Dr. William Gray

If you watch CNN and other TV channels in late May every year, you probably hear about a report by Dr. William Gray (Gray's Report). This report contains Dr. Gray's predictions of how many tropical storms and hurricanes we should expect in the season starting the following June 1. I had become interested in talking to Dr. Gray about his report, particularly after last year's hurricane season which included Katrina and all the destruction it created. I did not know what to expect when I traveled to Fort Collins to meet with him at his office at Colorado State University . I have been an advocate for ideas supporting the effects of Global Warming since I took a physics class in graduate school. When I had finally reached him on the phone to request an interview he asked me why I wanted to talk to him. I explained that I wanted to talk to him about his report. He asked if I was going to ask him about global warming too since that seems to be a hot topic right now. "You know I don't quite agree with everything they are saying.", he said. I knew that.

Dr. Gray moved to Colorado State University where he has dedicated his scientific life and career in understanding the science of hurricane predication. He is a kind man who talks about science with passion and I found my conversation with him most fascinating. We talked about his report, his science, his life as a scientist and of course global warming.

Shadi Farhangrazi

 

Shadi: When did you come to Colorado State University ?

Dr. Gray: I came to Fort Collins (to this department) in 1961. My major professor at the time, Dr Herbert Riehl came to Colorado and started this department in 1960 and I came here in 1961. I have taught all these years and have had some of the best graduate students who are now out in the field. Most of them are doing very well.

My main background has been to try to understand why hurricanes form, why they become as strong as they do, what their structure is, why they move in a certain way; why do some intensify and others weaken. So that has been my main effort but in teaching tropical meteorology here, I found that there are climate signals. I used to wonder if that was going to be an active year or not.

In the Atlantic for example, in 1933, there were a lot of storms. That was an active year. Other years, for example 1929, we had very few (storms). In 1914, there were no hurricanes; we only had one tropical storm. And then, there are other years, like 1916, when we had a lot of storms. The Atlantic basin, has had many storms in some years and then, in other years, there have not been many storms. We never knew why. We would always wonder: will this year be an active year or not? We really did not know. Then I found that there are some global things. If you look around the globe, you see these signals. For example, if we have warm water and an El Nino, we tend to have fewer storm seasons. Also, we have stratospheric winds going around blowing from the west for 14-15 months, then they turn around and blow from the east for 14-15 months. That is called quasi-bi-annual oscillation . I found that when they blow from the west we tend to have more storms. Also, I have found that if we have a lot of rain in the early season we have more storms. There are a lot of different things which are important.

I started this forecasting looking at all of this. This actually starts before the season starts. There are what we call the precursor signals. We look at the globe year--for example, if we look at 3-6-9 months before the season starts, we find that there are some global features of the atmosphere and the ocean that tend to be there 3-6-9 months before an active season. This is an empirical system. We look in the past. We go back about 55 years, looking at good data. We look at 10-12 active years and also 10-12 inactive years. We look at the features that are common. We find that there are many differences.

We get the information from NOAA. We have all that information along with thousands of maps and temperature differentials, plus lots of other information which we look at to do the forecasting. One of the reasons we use this empirical system is because the atmosphere is so complex. Numerical predictions work for weather forecasting. With the numerical predictions you don't care about the past. You just take the conditions as they are now and you integrate forward with time. That works well for 5-10 days but then it does not work in the long term because we have all these complex things such as energy, land and sea interactions, and a whole series of other things.

Shadi: Every June 1 st , your report (Gray's Forecast) is talked about. So, it sounds like for you to publish your forecast every May 31-June 1, you have to work the whole year towards it.

Dr. Gray: We work for months. I, however do other things too. I am involved with a number of projects and I have also taught many students over the years. I now have a colleague whose name appears on the forecast report as the first author. I have been doing this (forecast) for many years, over 23 years, and that's why they call it Gray's Report.

Shadi: How long does it actually take you to put the forecast together?

Dr. Gray: We think about it throughout the year. For example, we made a forecast in early December. We have kept our first forecasts and we keep watching everything (the patterns). We keep printing out maps, studying the new ones. As we get closer to the season, we can usually do better (at forecasting). I am amazed that we can do this. Predicting weather, days in advance is hard. Yet we are doing these forecasts months in advance. We do not do when and where. Our forecasts are different. We say there will be more storms this year and so on.

Shadi: We've had the first storm, Alberto, earlier last week, which was very mild compared to what they expected.

Dr. Gray: Yes, it was fortunate and a good storm since it brought a lot of needed rain.

Shadi: I was looking at the forecast for this year, and you are predicting 17 storms and 9 hurricanes for this year. Also, you actually do not give the intensity of the hurricanes.

Dr. Gray: We do give some, because we say how many hurricanes will there be, how many named storms, how many intense or major ones. We just give the number and the class. For example, the intense ones (storms) have maximum winds more than 110 miles/hour. Hurricanes have winds of more than 75 miles/hr. No one can say exactly (how strong a hurricane will be) and we don't say where either. No one can do that. With (predicting) landfall (in the U.S. ), we can not say where they go. We can give probabilities. The East Coast is more vulnerable to these storms than the Gulf Coast --more vulnerable over the long term average. Before, we could say nothing at all. We could only say the average season has so many storms. And we would use the average. But now we can adjust a little bit. We could say the climate signals show that we could have a more or less active than normal season.

Shadi: I want to ask you about the parameters and the factors you look at in your measurements. For example, in your forecast you mention “salinity”. How do you look at those factors and come up with what you have?

Dr. Gray: Well, we found that besides the year to year variations, there are these multi-decadal cycles . We are in a period of many more major storms. Over the last decades we have had cycles of low and high intensity, reports of major storms. The last 11 years we have had a more active period. We have these multi-decadal cycles which I believe are due to thermal-halion circulations. And it affects the major storms most. The major storms, category 3-4-5 storms on the normalized basis. But, not every storm fits it (the definition of “major” by intensity normalization).

About 80 or 85% of the damage if you normalize for coastal population, wealth per capita, You see, every one owns more now. Wealth per capita doubles about every 35-40 years. If you go back about 75 years to the time of my grandfather, they lived in smaller houses. They had one bathroom instead of two or three. They had less to lose. Now, every one is building bigger homes, (owning) bigger things. So as a result there is more to lose. If we normalize for coastal population, inflation, wealth per capita and go back 100 years, and look at the typical damage, they (hurricanes) do about the same extent of damage. Now, fortunately, we have a climate (prediction) system that works better.

Shadi: In a section of your forecast, you also ask the question if global warming is responsible for the more intense hurricane season. And your answer to that is that it (global warming) is not.

Dr. Gray: No, it is not. Because we have had this before. We can go back to the earlier data in the 19 th century and the Greenland ice core and find out that the North Atlantic got warm and cold in the previous century. This is a natural phenomenon. This goes faster, some times slower, but this goes way back before humans put greenhouse gases in the atmosphere.

Shadi: In your report, you also mention that, yes, temperatures have risen over the last few decades, but they are not responsible for the number of hurricanes.

Dr. Gray: My colleague Phil Klotzbach has just written a paper which talks about this. Even though the globe has warmed a bit, the frequency of storms globally has not changed. The Atlantic has had more (storms) but not due to global warming. For instance, there was this period in 1945 where the globe was cooling and we had 80 major hurricanes and 201 major hurricane-days .

Shadi: So, your prediction is that for the next 15-20 years we will have more active hurricane seasons.

Dr. Gray: Not every season because there will be El Nino years. But, in general, the seasons will be more active but particularly with major storms.

Shadi: Last year, we had a major year for hurricanes. Obviously we had hurricane Katrina. Were you surprised by the intensity of Katrina?

Dr. Gray: No, I was not surprised. Wilma was worse and more intense. I am actually writing something on this subject. We are not so surprised by the level of intense hurricanes. We have been talking for years about the level of hurricane damage.

Shadi: And you were not surprised by the level of destruction.

Dr. Gray: I was surprised that the levees in New Orleans were breached. If the levees had not been breached we would have had half of the problems. But I am not surprised by the level of damage in Mississippi . This was a very intense hurricane. We are bound to get those.

Shadi: Let me ask you another question, which is interesting to me as a scientist. Obviously, we have come a long way with the science of predicting hurricanes. But where are we when it comes to the science of influencing hurricanes? Is there any research being done in that area?

Dr. Gray: Yes, it is interesting. Every year, I get 5-8 letters from people with ideas of how they can alter storms and hurricanes. I have also had some ideas. But we are not there yet. Also, people do not want to influence storms because you do not know what happens when you alter nature. There are political issues (as well). Also, the scale and size of hurricanes is such that any intervention will be very difficult. There are all kinds of problems at this point. For example: people say--why can't we go to the center of the hurricane and drop a bomb to blow it up? It is not that easy. You could probably make it work, but there are all kinds of problems. People also say: we could put something on the surface of the water to prevent evaporation. Well, the amount you could cover as compared to the size of the storm is too small. People say: you could stir up the water because there is cold water underneath. But the waves will drive the cold water away.

Shadi: On a different subject: How did you get interested in hurricanes?

Dr. Gray: I did both my Masters and PhD (research) on a hurricane topic. When I got out of the Air Force, I went to University of Chicago . I studied under Herbert Riehl who was an important person in the field. He took me to Florida and got me started. Then he came out here. We had always done hurricane work at Colorado State and I just got going.

Shadi: You said that one of your students is involved with forecasting cyclones in Asia . Are you involved with forecasting internationally?

Dr. Gray: I used to be. I organized the first conference on tropical cyclones and storms. Half of the people were researchers and the other half were forecasters. They were from 28 countries. I have been all over the world to every cyclone center. Many people now working all over the world were my graduate students. I have been studying storms from a global point of view for a long time.

Shadi: How did you become interested in science?

Dr. Gray: I was interested in weather but what got me started was the Korean War. They (the US ) had an Air Force program where you could become an officer and specialize in weather forecasting. I joined that.

Shadi: And were you interested in studying science before that?

Dr. Gray: I was a geography major and I had taken math through calculus and some other science. I grew up in Washington and was very interested in geography, politics and places in the world. But I also had enough science and math. I was always good in math and they told me to major in math, but I did not like it that much. Then I got into graduate school and then took a lot of math and physics.

Shadi: You have obviously had many students, including graduate schools students who got their PhD and Masters degrees under you. How could we get more young people interested in science?

Dr. Gray: I think there are a lot of young people interested in the weather, particularly with television showing the beautiful pictures. Also, there are a lot of people living on the coast. Kids grow up with a lot of interest in the weather wanting to become weather-people. The interest in the weather has increased quite a lot over the last few years.