Predicting which African storms will intensify into hurricanes
Tel Aviv University researcher finds hurricanes ravaging US and Canada originate as disturbances in western Africa’s atmosphere
Hurricanes require moisture, the rotation of the earth, and warm ocean temperatures to grow from a mere atmospheric disturbance into a tropical storm. But where do these storm cells originate, and exactly what makes an atmospheric disturbance amp up full throttle?
A new study published in Geophysical Research Letters by Tel Aviv University’s Prof. Colin Price and his graduate student Naama Reicher of the Department of Geosciences at TAU’s Faculty of Exact Sciences finds most hurricanes over the Atlantic that eventually make landfall in North America actually start as intense thunderstorms in Western Africa.
“85 percent of the most intense hurricanes affecting the U.S. and Canada start off as disturbances in the atmosphere over Western Africa,” says Prof. Price. “We found that the larger the area covered by the disturbances, the higher the chance they would develop into hurricanes only one to two weeks later.”
Watching the clouds gather
Using data covering 2005-2010, Prof. Price analyzed images of cloud cover taken by geostationary satellites, which orbit the Earth at the precise speed of the earth’s rotation and take pictures of cloud cover every 15 minutes. This enabled Prof. Price to track the variability in cloud cover blocking the earth’s surface in West Africa between the months of June and November — hurricane season.
The coverage of clouds acts as an indication of atmospheric disturbances. The more clouds in an area, the larger the disturbance. Using infrared cloud-top temperature data gathered from satellites, Prof. Price assessed the temperatures of the cloud tops, which grow colder the higher they rise. He then compared his cloud data with hurricane statistics — intensity, date of generation, location, and maximum winds –from the same period using the National Hurricane Center data base.
“We first showed that the areal coverage of the cold cloud tops in tropical Africa was a good indicator of the monthly number of atmospheric disturbances — or waves — leaving the west coast of tropical Africa,” said Prof. Price. “The disturbances that developed into tropical storms had a significantly larger area covered by cold cloud tops compared with non-developing waves.”
What makes them special
According to Prof. Price, only 10 percent of the 60 disturbances originating in Africa every year turn into hurricanes. And while there are around 90 hurricanes globally every year, only 10 develop in the Atlantic Ocean.
“We wanted to know what was so special about these 10% of disturbances that develop into hurricanes. Was there something different about these storms at their genesis?” said Prof. Price. “By looking at each of these storms individually, we found again that the larger the cloud coverage originally in West Africa, the higher the value of the accumulated cyclone energy in a future hurricane. The conclusion, then, is that the spatial coverage of thunderstorms in West Africa can foretell the intensity of a hurricane a week later.
“If we can predict a hurricane one or two weeks in advance — the entire lifespan of a hurricane — imagine how much better prepared cities and towns can be to meet these phenomena head on,” Prof. Price says. He is currently examining the thunderstorm clusters around the eyes of hurricanes to study the intensification process of those destructive phenomena.
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“Don’t we already know at least one week to ten days or more ahead of time that a potential hurricane is headed in our direction?”
Yes, we have known about these easterly waves from African for decades and can predict their tracks fairly reliably a week or so in advance.
But this paper claims to have made progress in this research area by finding correlations between the cloud-top temperatures of storms in Africa with the eventual intensity and surface coverage of those storms which later developed into hurricanes.
Remember this is a PhD candidate, developing and validating a theory for his thesis, so some “hand-waving” can be expected in these “preliminary findings” papers. That’s fine. That’s the nature of scientific research.
But if this research does pan out successfully, then some day we might be able to predict that a particular Saharan storm, with probability X, will develop into a Category 5 hurricane with a diameter of 1000 km etc. I.e. we can add that capability to the existing capability of predicting the hurricane’s track.
Someone tel Aviv we already knew that.
Marq de Villiers had it all described in the history of Hurricane Ivan in his book Windswept in 2006 – this is not news…..
Windswept: The Story of Wind and Weather was published by Walker in New York and McClelland and Stewart in Toronto in January 2006.
My understanding of the article is that it centers in storms IN AFRICA, not in the Cape Verde Islands, not off the African coast, but actually still in the interior of the continent. Measuring their area of coverage or other details of the storms while still over land may furnish details farther in advance of storm development than would be possible by waiting for the hurricanes to form hundreds or thousands of miles out in the Atlantic. Obviously, I don’t have all the previous research or articles, but some of the comments above did seem to me to misstate or omit the central message of the article, as I read it.
How much farther in advance do we need? IF the conditions are right, and IF a hurricane forms near the Cape Verde Islands we in the U.S. have more than a week to watch it. Even at this time and stage there is no telling what will happen as it makes its way across the Atlantic. No one is going to shutter up, evacuate or take any other action this far out. It may not even stay a hurricane or it may not even come close to the U.S. even if it does no one knows at this time where it could make landfall. Usually at this time of year there are tropical systems closer to home to be watched first.
No duh.
Ya know, I recently read that there are a million PhDs in the world now. And those in academia are under the “publish or perish” dictum. Meaning they have to scrape the barrel to find ANYTHING to do a paper on, that no one else has already done. No joke.
I’m a florida lifer. I half remember seeing something about how the Cape Verde islands help kickstart African waves into hurricainable waves during August. September season. I wish I could find that again. This article broke one of two of my Cardinal rules. Don’t waste your money with Israelis studying hurricanes. And never never let Florida state people study arctic anything
Yup another case of scientists announcing the incredible genius of discerning the obvious insights of Farley Mowatt and other astute individuals who write about hurricanes or try like hell to avoid them in this case “What is upstream will end up down stream and the misery all depends on what happens along stream……”
Wait a minute… Tropical storms in CANADA???? Is that a misprint, or are they daffy?
Also, their math doesn’t add up. “According to Prof. Price, only 10 percent of the 60 disturbances originating in Africa every year turn into hurricanes. And while there are around 90 hurricanes globally every year, only 10 develop in the Atlantic Ocean.”
Am I the only person who calculates 10% of 60 as 6, yet they claim that 10 hurricanes “develop in the Atlantic” every year.
Since when does 6 equal 10?
I don’t get it.
Since most hurricanes that develop from Africa are quickly and easily tracked already, And we on the east coast don’t really do anything until it gets much closer and the path is known with more precision. I guess I’m not seeing the need or even potential for more advanced warning based on this study.