Global Drifter Program helping to forecast hurricane intensity

In August 2004, the National Hurricane Center and residents of southwest Florida were caught by surprise when Hurricane Charley strengthened in a matter of hours from a Category 2 storm to a Category 4. It went on to be the strongest hurricane to hit the country since Andrew in 1992 -- if only for a year.

Since then, scientists still haven't found a much better idea of how to forecast the intensity of hurricanes, but dataset by dataset, their ability is improving. In an era that has seen the frequency of destructive hurricanes accelerate, a research drive being led in places like San Diego is picking up as well.

That's right. The land of 75 degrees and mostly sunny is a major player in hurricane research.

On Sept. 21 of this year, for instance, a C-130 aircraft from the U.S. Air Force Reserve Weather Reconnaissance Squadron dropped 20 drifting buoys in the path of Hurricane Rita. These drifters were "Minimet" units invented at Scripps Institution of Oceanography and made by Oceanside's Pacific Gyre Inc. The Minimet units they make can measure sea surface temperature, air pressure, wind direction and wind speed (a measurement inferred by an underwater hydrophone that listens to ambient noise generated by breaking waves).

Housed in protective cardboard containers that dissolve when parachuted into the ocean, the drifters delivered surface air pressure and water temperature data to hurricane forecasters tracking the storm's path.

Although the wind speed data the drifters gathered seemed too noisy to be quickly interpreted, the deployment featured several impressive feats. All 20 drifters survived both the air drop and the hurricane itself, and the Hurricane Hunters 53rd Squadron successfully parachuted half of them in the direct path of the eye, a veritable bull's eye to storm track prognosticators.

But the world of marine climate modeling and forecasting is less attuned to such immediate gratification than in the collection of detailed data over many years. That's why Scripps' Professor Peter Niiler, the inventor of these drifters, might be forgiven for finding another event from the same week Rita made landfall even more thrilling than the flight of the Hurricane Hunters. On Sept. 18, the Global Drifter Program that he leads deployed its 1,250th buoy off Halifax, Nova Scotia.

In so doing, the National Oceanic and Atmospheric Administration program achieved its goal of complete coverage of the world's oceans 17 years after Niiler's first drifter was deployed. Today, thanks to this program, the world gets a sea surface temperature map delivered twice a week via Internet. It has also helped identify and produce new maps of all the world's major ocean currents, even in places like the Southern Ocean surrounding Antarctica where before, circulation patterns were merely guessed at.

In addition, meteorologists in the southern hemisphere are now able to identify major storms developing over the oceans there. Prior to 1982, when Niiler pitched to colleagues the idea of a buoy array deployed even in the most remote ocean stretches, forecasters used to miss a full third of southern hemisphere storms because there was simply no data to work with. Now the knowledge is so accessible, NOAA's Office of Climate Observation even runs an Adopt-a-Drifter program that has incorporated buoy data into the lesson plans of schools around the world.

None of the scientific knowledge came easy. The 250-odd research papers based on Global Drifter Program data came as a result of careful distillation of thousands of lines of information from the drifters radioed back via satellite. Niiler believes it will be thus with hurricanes like Rita. It wasn't the real-time data from the storm, though important, that will solve the hurricane prediction problem. The payoff of the exercise will come in five years, 10 years or 50 years, when the fearsome hurricane's physical effects are but another layer of detail in a history of storms gathered systematically over time.

How long it will take depends on the vitality of the drifter program going forward. The 1,250 units in the array do eventually die and require replacing every 18 months and officials hope to cover even more areas.

Despite the milestone last month, the program by its nature never reaches the finish line.

The future of the program may swing on the fortunes of NOAA, an agency currently dealing with profound budget cuts. The total cost of the Rita Hurricane deployment -- airplane and drifters -- was about $300,000, a lot of money but nothing considering the dividends the drifter fleet will pay for generations to come.

Monroe is senior science writer for UCSD's Scripps Institution of Oceanography Explorations magazine. Send comments to All letters are forwarded to the author and may be used as Letters to the Editor.

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