Above: Unmanned aircraft will undertake dangerous hurricane reconnaissance missions in the Caribbean for the first time in 2008.

The United States government is positioning four Australian-made, unmanned aircraft in Barbados to fly into Atlantic cyclones this year in what is expected to be an above normal season, according to the latest update from an American forecast team.

The Colorado State University team of Professor Bill Gray and Dr Philip Klotzbach have predicted an active season this year. Their updated forecast, released on Tuesday, has kept the same figures as their pre-season forecast in April: 15 storms, eight hurricanes, and four potentially destructive major hurricanes with winds in excess of 111 miles per hour.

There is an above average change that one of these destructive hurricanes will make landfall somewhere in the Caribbean, the forecasters said. They explained that one highly uncertain factor in this year's forecast is whether El Nino conditions remain weak or whether La Nina conditions will dominate.

The phenomenon, known as the El Nino Southern Oscillation (ENSO), is determined by the sea surface temperatures in the central to eastern Pacific Ocean. Warmer-than-normal temperatures are known as El Nino while cooler-than-normal temperatures are known as La Nina.

Each interact with the atmosphere and influence the weather in the Atlantic Ocean and the Caribbean, with a strong El Nino produces upper levels winds which are hostile to hurricanes forming while La Nina enhances hurricane formation. The forecasters said that the La Nina of late 2007 is waning and it appears that an El Nino is coming into force.

"The big question is whether this current observed warming will continue through this year's hurricane season. At this time, it appears unlikely that ENSO will transition to warm conditions by the August-October period," they said in their updated forecast. However, they added, conditions in the tropical Atlantic are becoming favourable.

"These conditions have trended even more favorable than were observed in early April. Our early June Atlantic predictor (Predictor 1) calls for a very active hurricane season in 2008. The current sea surface temperature pattern in the Atlantic is a pattern typically observed before very active seasons." The US National Ocean and Atmospheric Administration (NOAA) has forecast a "normal to near-normal season" with 12 to 16 storms, six to nine hurricanes, and two to five major hurricanes.

A "normal" season is based on the 50-year average between 1950-200 which is 9.6 storms, 5.9 hurricanes, and 2.3 major hurricanes (winds in excess of 111 miles per hour). The Tropical Storm Risk team in England has forecast 14.8 storms, 7.8 hurricanes, and 3.5 major hurricanes. Three other commercial meteorological services in the United States, WSI Corp, AccuWeather, and WRC (Weather Research Center) have produced vastly different figures. WSI has forecast an above average season with 14 storms, eight hurricanes, and four major hurricanes; AccuWeather expects 12 storms forming with none becoming hurricanes; while WRC forecasts 11 storms and six hurricanes.

Drones in service

However the season materialises, NOAA has positioned unmanned aircraft in Barbados, the most easterly island in the Caribbean archipelago, to fly into any system that develops. The drones will go where no hurricane hunter aircraft has gone before - 300 feet from the sea - to take atmospheric measurements. It's a dangerous altitude for aircraft as the crew and one Barbadian journalist from the Nation Newspaper discovered when their aircraft, flying into Hurricane Hugo in 1989, almost crashed when it penetrated the monster cyclone at 1,000 feet.

Since then the crews have not been allowed to fly their planes in under 10,000 feet, but that is exactly where they want to get the data. So they will eject cylinders from the plane, filled with electronic devices that take various atmospheric measurements every three seconds as they plummet toward the sea, before being eventually lost in the ocean. The data, relayed via satellite link to the National Hurricane Centre in Miami, has been invaluable in improving the accuracy of forecasts.

NOAA has invested US$3 million in these remote-controlled, single propeller aircraft that can fly at a top speed of about 70 miles per hour and cover 2,000 miles on a single US gallon of fuel, according to researchers. However, the planes won't operate from any US territory because the US Federal Aviation Administration has not given NOAA approval to operate the planes from American soil on safety grounds.

Because of the height at which the planes can fly, they can monitor the energy transfer from the sea's surface to the storm. Marty Ralph, a research meteorologist at NOAA's Earth System Research Laboratory, Colorado said that the drone will provide a continuous steam of information on a "big chunk of the atmosphere" that remains relatively unobserved and by coupling that with satellite information, they could "really understand how the hurricane is getting its energy and maintaining it".

"What you can do with the Unmanned Aircraft System (UAS) is fly down in a continuous mode and keep sampling, essentially follow the storm so we can actually track changes. It is a very unique capability. We are getting the types of measurements we should not otherwise be able to get," he explained. The drones, costing between US$50,000 and US$80,000 each, will also be used to track how fast Arctic summer ice will melt and whether Pacific storms will flood the west coast of America.

Source: www.caribbean360.com - June 4, 2008

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