Two P3-Orion "Hurricane Hunters'' and a Gulfstream G-IV jet from the National Hurricane Centre in Miami were on the Island over the weekend chasing the hurricanes swirling around the Atlantic. Bermuda Biological Station for Research sicentist Dave Malmquist toured the planes. This is what he found.

When these planes detect severe turbulence dead ahead, they head straight for it.

Three NOAA "Hurricane Hunter'' aircraft -- two P-3 Orion turboprops and a Gulfstream G-IV jet -- touched down in Bermuda late Thursday night for a well-earned respite after nine straight hours of flying through, over, and around Hurricane Dennis, the most threatening of the three tropical cyclones spinning in the western Atlantic this week.

All three planes have now returned to their base in Florida, once again flying through Dennis on their way home.

Stationed at McDill Air Force Base in Tampa, Florida, the aircraft are owned and operated by the US National Oceanic and Atmospheric Administration, or NOAA. Their primary mission is scientific -- to study how the atmosphere is structured and behaves both with and around a hurricane. Better understanding the atmosphere around a hurricane is crucial for improving forecasts of fast-moving storms like Bermuda's 1987 Hurricane Emily.

Reconnaissance flights, whose primary purpose is to gather the information forecasters need to predict a hurricane's track and intensity, are mostly flown by the other "Hurricane Hunters,'' a fleet of modified C-130 transport planes from Keesler Air Force Base in Biloxi, Mississippi.

Walking toward the P-3 that sits loudly idling on the Bermuda Airport's scorching tarmac, it's obvious that this isn't your ordinary aircraft. The first clue is the plane's nickname. Stenciled near its front door is "Kermit,'' a name unlikely to grace a regular commercial airliner any time soon. Alan Goldstein, our guide and an electronics engineer with NOAA's Aircraft Operations Centre, notes that the other P-3 is nicknamed "Miss Piggy''. It has already left Bermuda to fly back into Dennis and then continue home.

Another clue is the 20-foot, red-and-white striped pole that extends from the plane's nose, giving it the appearance of a grounded narwhal. Instruments on the pole were once used to gauge the speed of the wind around the plane, but those have since been replaced by an improved wind gauge built into the plane's nose. The "barber's pole'' remains because removing it would be more trouble than it's worth.

The most telling external indication of the plane's business is the dozens of "yin-yang'' hurricane decals pasted to its fuselage-one for each storm it has flown through. Two decals in particular catch the eye, as they each show a hurricane spinning in the opposite direction to the others. These represents the pair of hurricanes the plane has flown through in the Southern Hemisphere, where tropical cyclones rotate clockwise.

The true purpose of the P-3, and a stark reminder of how bumpy its ride must sometimes be, becomes clear the moment you climb up the steep gangplank and into the fuselage. Inside, the luxuries of a modern passenger plane, such as reclining seats, movie screens, and food carts, are notably absent.

Instead, a long line of computer monitors, radio microphones, and other paraphernalia stretch fore and aft along either side of the cabin.

In place of overhead bins are thick vinyl-covered pads, which line the walls all the way to the floor. These are presumably to protect the heads of any untethered crew when the plane encounters a particularly rough patch of air.

But it doesn't look like this is the kind of plane on which the captain would often turn off the "Fasten the Seat Belt'' sign. Indeed, bolted to the floor before each computer screen is a seat that comes with not just a lap belt, but a shoulder belt as well. Make that two belts-one for each shoulder.

Thankfully, the three pilots' seats are also equipped with these harnesses.

Mark Rogers, our guide inside the plane, says that the ride does get bumpy at times, particularly when Kermit flies through a spiral rain band or the hurricane's eyewall. The eyewall is the ring of rapidly rising, turbulent air surrounding the storm's clam eye. Because the eyewall is where the hurricane's strongest surface winds occur, researchers and forecaster alike are intensely curious to better understand its behaviour.

That's why on a "Vortex'' flight, the P-3's crew doesn't just fly through the eyewall once or twice to determine a hurricane's maximum winds and lowest atmospheric pressure, as is done on a reconnaissance flight. Instead, they fly through the eyewall repeatedly. The record for a single Vortex flight is 29 eyewall crossings.

The most harrowing experience aboard this P-3 occurred in 1989, when Kermit encountered a "mesovortex'' while flying through the eyewall of Hurricane Hugo. Hugo devastated the Caribbean and later wreaked $7 billion in damage when it came ashore near Charleston, South Carolina as a Category 4 hurricane.

"Mesovortex'' is a meteorologist's term for a medium-sized cyclone. It is much smaller than a hurricane, and much bigger than a tornado. When Kermit hit the Hugo mesovortex, it nearly pushed her into the water, which just happened to be a seething cauldron beneath 130 mph winds. At the same moment, Kermit's number 3 engine stopped working and burst into flames.

The only reminder of this episode, besides the crew's impassioned re-telling, appears in the metal rod that runs above the plane's aisle. Used as a support by unseated crew members when the ride gets rough, the rod still bears the sharp bend it received when struck by a flying object, thankfully not a crew member, during Hugo.

Rogers says that lightning doesn't hit the plane that often, "at least not on every flight''.

For the uninitiated, perhaps the most disquieting feature of Kermit is that she has two fairly large holes, albeit covered, in her floor. Rogers explains that these are launch chutes for the "dropsondes,'' or "sondes for short, that the crew drops into the underlying storm. Sondes are cardboard cylinders about the size of a roll of paper towels that are packed with tiny electronic sensors. These measure temperature, wind speed, relative humidity, and air pressure as they fall through the hurricane, and radio that information back to the plane, where it is recorded as research data and also forwarded via satellite to the National Hurricane Center (NHC) forecasters.

Chris Landsea, a scientist at the NHC's Hurricane Research Division in Miami, notes that these new sondes contain a GPS device that allows the crew to determine the sonde's altitude and geographic location much more accurately than before. This improves their understanding of the fine-scale dynamics of the hurricane's winds. But all those electronics come at a price. Each sonde, which ultimately plummets into the ocean and is lost, costs $500. On a typical flight, the crew will drop about 20 sondes.

The P-3 crew also drops "BT'' sondes. These fall to the ocean surface beneath the hurricane, where they release a weighted probe that measures the water temperature as it sinks. This allows the scientists to determine how deep the warm waters needed to support a hurricane extend.

"P-3s are tractor-trailers,'' says Alan Goldstein. "The G-IV is a race car.'' Indeed, unlike Kermit's unique and telling countenance, the G-IV parked nearby resembles the surrounding sleek corporate jets -- until you step inside. Instead of the expected wet bar and leather couches, the interior of this particular aircraft is jam packed with computers, computer monitors, radar screens, cables, seat belts, and a few sonde ports of its own. The "Gonzo'' nickname stencilled outside the door should have been a clue.

The G-IV is perfectly suited for surveillance missions. These are designed to explore not the hurricane itself, but the wider environment around and above the hurricane. It is this ambient environment that ultimately controls a hurricane's path and intensity. Because hurricanes can be quite large, with diameters of hundreds of miles and thunderstorms towering to 40,000 feet, exploring the atmosphere around a hurricane requires a plane that can fly fast, far, and high.

The G-IV fits the bill. It has a cruising speed of 450 mph, a range of 4,000 miles, and can fly as high as 45,000 feet. P-3s, on the other hand, have a cruising speed of only 300 mph, a range of around 2,500 miles, and typically fly at only 5,000 to 1,000 feet, with a maximum altitude of 25,000 feet.

Although P-3s are relatively slow, they make up for it in quickness, says Rogers. The P-3 pilot can continue to run the plane's engines at a high RPM even when travelling slowly, simply by changing the angle of the propeller blades, much as a boat driver can control speed at constant RPM by tilting the outboard motor. To speed up quickly, the P-3 pilot simply repositions the blades. This allows the type of rapid acceleration needed in a hurricane, where the 110-mph tailwind pushing the plane through the eye wall suddenly stops as the plane enters the clam of the eye. The G-IV, with all its speed, must ramp up its jet engines to accelerate quickly, so it tends to avoid really turbulent areas.

Kermit and Miss Piggy have been flying hurricanes since 1975.

Hurricane hunters At the time, they each cost $7 million, plus another $7 million each to install the needed electronics.

"These P-3s are the cleanest and best-maintained airlines around,'' says Goldstein. "They've flown only 5,000 hours in 20 years, although those have been very hard miles.'' In operation since 1997, the G-IV cost $48 million. The NOAA scientists think the cost is well justified. Only by observing what is happening in the atmosphere surrounding a hurricane can researchers better understand, and forecasters better predict, where a hurricane like Dennis might go, and how strong it might become. Given the thousands killed by Hurricane Mitch last year, the destruction wreaked by Emily in Bermuda, and the multi-billion dollar price tags left by hurricanes like Hugo and Andrew, $48 million seems a drop-sonde in a bucket.

Photos by Dave Maimquist In the eye of the storm: The nose -- and red and white striped wind gauges -- of one of the hurricanes hunting P3-Orions Drop sounds: Holes in the bottom of the P3-Orion are used to dro drop-sonds which indicate the strength of hurricanes and tropical storms.

Speed machines: Crew and visitors pose outside the National Hurricane Centre's $45 million Gulfstream G-IV jet -- a key weapon the struggle to learn more about hurricanes. The jet -- which is packed with computer equipment cruises at 450 mph and can fly as high as 45,000 feet.

Into the eye: Hurricane hunters go into the eyewall of storms to determine their strength and behaviour.

BIOLOGICAL STATION SCI