Looking Ahead To A Busy Hurricane Season

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Many forecasts for the 2010 hurricane season predict more named storms and major hurricanes than an average year. Phil Klotzbach, lead forecaster on the Hurricane Forecast Team at Colorado State University, discusses the climate factors that may stir up more Atlantic hurricanes this year.

IRA FLATOW, host:

All the eyes in the Gulf of Mexico, of course, have been turned toward the dramatic oil spill there. But, you know, any other year, any other time, this time of the year, people would be thinking of something else, the hurricane season. In about three weeks, the hurricane season will be here and a lot of the forecasts are now saying that the right climatic ingredients could be in place to make this a really big year for hurricanes, maybe on par with big years like 2005. And you remember that year, that was the year that spawned Hurricane Katrina.

So what are the factors that come together to create a big storm season? How much can we tell about the upcoming season by studying conditions in the past? Is it - excuse me - isn't climate change tweaking the variables a little bit? Joining me now to talk about that and the forecast, his forecast, for the hurricane season is Phil Klotzbach. He is lead forecaster for the hurricane forecast team at the Colorado State University in Fort Collins, Colorado. He's also a research scientist in the Department of Atmospheric Sciences there. Welcome to SCIENCE FRIDAY.

Dr. PHIL KLOTZBACH (Lead Forecaster, Colorado State University): Thank you very much for having me.

FLATOW: Looks - tell us about the forecast. It looks pretty intense.

Dr. KLOTZBACH: Yeah. Well, the way this forecast that we put out was in early April and at that time, we were calling for a pretty active hurricane season. A typical season has about 10 name storms, six hurricanes and two major hurricanes. We're currently predicting 15 name storms, eight hurricanes and four major hurricanes. So, if you kind of want to summarize it with one number, about 160 percent of the average season. So, yeah, pretty active.

FLATOW: And so, it looks something like 2005 which spawned Katrina.

Dr. KLOTZBACH: Well, no, not necessarily. I mean, 2005 had 15 hurricanes and 28 name storms, so we're not necessarily expecting to see that much activity. But, certainly, we do feel that conditions are going to be a lot more conducive for a lot of storms than say there were last year when we only had three hurricanes.

FLATOW: Is it basically looking through the hurricane record, the seasonal records, the maps and comparing what you see on those when it was a stormy year and seeing what's shaping up this year?

Dr. KLOTZBACH: Yeah, that's correct. Basically, the way that we come up with our forecast is we use historical data and we use the past. Like you said, what we do is we basically know which years in the past were active hurricane seasons and which years in the past were quiet seasons. And then what you do is you try to look and see what sets of climate conditions, how - what was the atmosphere like and what was the ocean like in active seasons in the past versus inactive seasons in the past, then you find that certain sets of conditions do occur.

One of the common ones that we use is El Nino. When you have El Nino, which is warmer than normal waters in the tropical Pacific, you tend to have fewer storms in the Atlantic and that's what we saw last year. But that El Nino appears to be dying now, so we don't think we're going to have that to help keep the season quiet this year.

FLATOW: Mm-hmm. So - El Nino is dying down and what other conditions make it look like a bad hurricane season?

Dr. KLOTZBACH: Well, one of the things that we've really noticed over the last several months is we've seen a very strong warming of the waters in the tropical Atlantic. The waters right now in the tropical Atlantic are running at near record levels, so certainly, very toasty right now. Now just because they're warm now doesn't guarantee they're going to be warm during the August to October period when we see most of our major hurricanes, but there is a fairly strong correlation there so that's another reason why we expect the season to be pretty active with the very warm waters that we have right now.

FLATOW: A question coming from Second Life from Pierre Mantis Burman(ph) says, will the oil spill in the Gulf have any impact on the hurricane season?

Dr. KLOTZBACH: Well, that's good question. There's been a lot of people asking similar questions. I think, really, when you get any sort of storm of any strength, say even a tropical storm, basically, the oil - the water would mix the oil and - or I should say the winds would mix the oil and the water together, so you wouldn't necessarily have the reduced evaporation from the oil slick.

I think one of the big concerns is that if we did get a hurricane in the Gulf and it happened to, you know, drive - have a fairly significant storm surge, it could drive the oily water further inland which could make a real mess. So, I think, certainly, there is some cause for concern, but obviously there's a lot of question as to how much oil is going to be left by the time that the hurricane season really ramps up.

FLATOW: Yeah, well, we don't know the answer to that question.

Dr. KLOTZBACH: No, exactly, we don't know the answer to that question and hopefully, we won't find out the answer this year.

FLATOW: So when you say really ramps up, what range of time are you speaking of?

Dr. KLOTZBACH: Well, basically, the most - even though the hurricane season starts on June 1st, then you certainly can get storms in June and July, about 90 and 95 percent of all major hurricane activity occurs after the 1st of August. So - and if you really want to pick a one-month time period where most of the storms occur, it's between about August 20th and September 20th is when you get, say, about 65, 70 percent of all your major hurricane activity. So that's the month where storms are most likely, but certainly you can obviously get storms in August and October, and even earlier and later in the season.

FLATOW: Do you see any connection between climate change and hurricanes in terms of the increasing water temperature, stuff like that? We keep hearing that the storms may be more intense.

Dr. KLOTZBACH: Well, that's a good question. Basically, what we find is that especially in the tropical Atlantic, there's this kind of multidecadal variability where your Gulf...

FLATOW: Wait, wait. A what?

Dr. KLOTZBACH: A multi - 25 to 30-year variability. It's multidecadal. It's a new term that they've - I don't know if atmospheric scientists coined it or what.

FLATOW: I thought you said mopey, at one point it was moping around. Mopey.

Dr. KLOTZBACH: Oh, no. Multi, multidecadal. So the variability that occurs on, say, 25 to 40-year timescales.

FLATOW: Yeah.

Dr. KLOTZBACH: Basically, we've seen these periods in the past with the Atlantic - the tropical Atlantic warms up quite a bit. We see a lot of major hurricanes and then it gets quiet and we have fewer. And if you look back at historical data, you can see these cycles going back to the late 19th century. So we don't really - we don't - and what I've done a little work looking globally at storms...

FLATOW: Right.

Dr. KLOTZBACH: ...and now obviously, observational data globally isn't always the greatest, and you may have some uncertainties especially if you go further back in time. But based on the data that we have, we really havent seen any observable trend in storms getting more intense...

FLATOW: Mm-hmm.

Dr. KLOTZBACH: ...with the fact that even water temperatures are warming because even if humans are causing global warming and causing the temperatures to warm, the warming not - doesnt just take place at the sea surface, it also takes place at upper levels in the atmosphere. And basically, the atmosphere doesnt really become a lot less unstable. Basically, the stability of the atmosphere remains about the same so you wouldn't necessarily expect to see stronger storms.

FLATOW: Well, Phil, thanks for the forecast and we'll keep our fingers crossed hoping we have safe hurricane season.

Dr. KLOTZBACH: Yes, here's hoping.

FLATOW: All right. Phil Klotzbach is the lead forecaster for the hurricane forecast team in Colorado State University in Fort Collins.

I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.

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