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Remembering Dr. Bill Gray, Hurricane Forecast Pioneer

Colorado State University

    

The 2016 Atlantic hurricane season is here and for the first time in decades South Florida will have to get through it without a man who was a pioneer in hurricane research. Dr. Bill Gray of Colorado State University (CSU) died in April. He's perhaps best known for his data-driven seasonal hurricane forecasts, which have been used for over 30 years.

WLRN talked to Dr. Phil Klotzbach, who started out as Dr. Gray's protegé and eventually became the other half of CSU’s hurricane forecast dynamic duo.

It’s hard to imagine a hurricane season without Dr. Gray.  In the early 1980s, why did he feel it was even necessary to start issuing a seasonal forecast?

Dr. Grey started issuing the seasonal hurricane forecast because he discovered that when you have warmer than normal waters in the center on the eastern tropical Pacific -indicative of El Nino conditions-, you tend to get fewer hurricanes in the Atlantic, due to an increase in strong upper level winds tearing apart storms.

Prior to when he started doing the seasonal hurricane forecasts, there really was no way to know how active the upcoming hurricane season was likely to be. And since he had this predictor and he discovered a few other predictors, he figured it was worthwhile putting out one of these seasonal hurricane forecasts.

What criteria did Dr. Gray use to predict how many storms there will be in a given season, how strong they will be and where they will make landfall?

Besides El Nino, he used predictors such as surface pressures in the tropical Atlantic -- lower pressures mean a more unstable atmosphere, which is generally conducive for a more active hurricane seasons.

He also used water temperatures in the Atlantic. Hurricanes live off of warm ocean water. So, more warm ocean water tends to mean a more active hurricane season.

He also looked at levels of vertical wind shear or the change in wind direction with height in the Atlantic -- when vertical wind shear is too strong, tends to tear apart storms and not allow them to become hurricanes and major hurricanes.

Why did Dr. Gray choose Colorado State University if this is a state that does not get hurricanes?

Dr. Gray followed his mentor and adviser ,Herbert Riehl, who was asked to start the Department of Atmospheric Science at Colorado State University. He [Dr. Gray], came from the University of Chicago, which again, is nowhere near where hurricanes tend to form. So it was Dr. Gray and Herbert Riehl who really kind of got the department started with hurricane research. And since Dr. Gray studied both hurricanes as well as typhoons in the Northwest Pacific, he said he chose Colorado to kind of split the difference between the two areas that he studied a lot.

If he were here, he would also tell you jokingly that the storm surge can't get you at 5,000 feet.

Along with an obvious love of storm forecasting what else did you and Bill Gray have in common.

We both were very big baseball fans. I grew up in Boston, so I'm a big fan of the Boston Red Sox.  He grew up in Washington D.C. and was consequently a big fan of the Washington Senators and Nationals. So we were united by the fact that neither of us liked the New York Yankees.

We also both were big history buffs --  he and I both talked a lot about the Civil War and well as World War II. So we had a lot of interests besides hurricane prediction.

Dr. Gray's stance on climate change raised many eyebrows in the scientific community. Where exactly did he stand on what causes climate change?

Dr. Gray’s stance on climate change was that he believed that most of the warming that we've observed since the middle part of the 19th century was due to natural causes -- not due to human induced CO2 warming.

The primary reason, he felt, was that the overall Atlantic thermohaline circulation had been going weaker over the past, say, 150 years. When that overturning circulation is weaker, you tend to get less bringing up of cold water to the surface in the tropics. So he thought that most of the warming was due to that.

He also felt that with CO2 causing a bit of warming, that would increase the speed of the hydrologic cycle -- or basically how quickly clouds form. If that circulation is going faster, it tends to lead to more upper level drying -- which tends to also counteract the CO2-induced warming by a slight drop in upper-level water vapor content.

Why do many forecasters think that this season will be the one where Florida's 10-year no-hurricane lucky streak will end?

Most of the seasonal hurricane forecasts that have been released so far this year are calling for a near-average Atlantic hurricane season. The long-term average is that Florida is hit by a hurricane about once every other year -- so there's about a 50/50 chance that Florida is hit in any particular year.

Florida has been going through an incredibly lucky streak -- we have  had no hurricanes make landfall in the state since  Wilma back in 2005. This shatters the old record of five years set from 1980 to 1984. Since this season has been predicted to be a near-average one, we can't say when or where storms are going to strike. But we do issue probabilities based on historical data.

In general, more active seasons do have more landfalls. This season we are predicting a near-average probability of landfall -- due to the fact that the overall hurricane season at this point we're predicting to be at near-average levels.

In all your years studying under Dr. Gray and working alongside him, what was the most important thing that you feel he taught you.

I really think one thing that Dr. Gray emphasized is to look globally at these storms -- not just get focused on what's going on in the tropical Atlantic.  To look at how these large-scale features are changing -- because conditions in the Atlantic may be very different in March and April from what they are during the peak months of the Atlantic hurricane season, from August to October.

Dr. Gray will be sorely missed. We were very close. I felt like he was more like a grandfather to me than just a mentor and advisor. I'll miss him greatly. 

Christine DiMattei is WLRN's Morning Edition anchor and also reports on Arts & Culture.
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