by Hugo du Plessis, May 2000
Imagine it is the hurricane season. A hurricane has been detected by satellite out in the Atlantic, and the radio has reported that an aircraft has been sent out to investigate. No doubt, like me, you had visions of a fairly ordinary crewed plane flying over the hurricane at a safe height just to find out what it looked like and where it was with greater precision than the satellite could.
As a group of yachtspeople found out when one of the hurricane hunter aircraft came into Piarco Airport, Trinidad, recently and was opened to the public, that simple vision is very wrong.
The special aircraft, one of a fleet maintained by NOAA (the United States National Oceanographic and Atmospheric Administration), is nothing less than sophisticated flying laboratories manned by teams of dedicated meteorologists and scientists. They fly right through the worst of a hurricane at quite a low level and analyze every aspect of it.
It is extremely uncomfortable as the plane is thrown around violently in the worst turbulence imaginable. It seems a wonder it can hold together. In fact the planes do suffer damage in some of the worst hurricanes, and over the years three have been lost with all hands. Their crews are courageous; they cannot bail if the plane gets into trouble. In hurricane conditions, a parachute would go up, not down, and anyway, nobody could survive in that sea, and no rescue boat would have a hope of reaching them.
The aircraft used are Lockheed WP-3D four-engine turbo-prop planes, with a wing span of 100 feet. Their range is 2,200 to 3,600 miles, depending on altitude, and their mission time is 8 to 11 hours. They are capable of speeds of 323 knots. The reason for the modest speed (by modern standards) and the turbo-props is so they can fly fairly slowly through a hurricane. A faster jet aircraft would come out the other side with its wings torn off.
Hurricane hunter planes are specially fitted out for their work with an impressive range of instruments. To allow the scientists to take accurate measurements, the aircraft has to try to fly straight and level. Because of the extreme turbulence, this requires both pilots to struggle with the controls. The flight engineer sits between them, manipulating the throttles to maintain constant height and speed, much like the throttle man on an offshore racing speedboat.
As well as the pilot, co-pilot, and flight engineer, there is a skilled navigator who has to know the exact course and position as they crisscross through the center of the hurricane. Other members of the 18-man crew are the flight director, senior meteorologist, computer operator, electronic technician, electronic engineer, radio operator, cameraman, scientists and observers.
The mission does not just make one pass to see where a hurricane is, but makes repeated passes for an hour or more to get as much data as flying time and the crew’s endurance will allow. Not surprisingly, air sickness can be a problem, especially for scientists.
The equipment includes an C-band radar in the nose, a large 360- degree scan C-band radar with a 12-foot antenna and 300-mile range in a big radome under the belly, and an X-band radar in the tail to give a vertical scan of cloud height. Radar altimeters and laser measure wave height and sea state.
The planes can drop radio sound buoys by parachute. Each buoy is equipped with GPS and transmits data on wind speed and direction, atmospheric pressure and temperature as it descends. When the buoys hit the sea, they transmit data on sea surface temperatures and then become bathythermographs, sending further information of sub-surface temperatures as they sink.
A long probe like a narwhal’s tusk sticks out in front of the aircraft to measure gusts. Other instruments obtain data about the clouds, the water content, ice particles, humidity and dew point, dust nuclei, solar radiation, carbon dioxide, steering winds, lightning and much else of interest to scientists and meteorologists. As the crew pointed out to us, there is still a tremendous amount to be learned about hurricanes. All the information is fed into a powerful onboard computer for later study, and whatever is of immediate interest is transmitted by radio back to the Hurricane Center in Miami.
Why send an aircraft and crew on dangerous missions like this? Why cannot satellites do the job? The weather satellites can spot the position of a hurricane but because of the associated dense cloud cover, they can give little information about its intensity. Moreover even the position is generally pretty vague. Anyone who listens to the hurricane forecasts on NMN knows that although the position is quoted to a tenth of a minute, say 10 miles, the margin of accuracy may be 60 miles or more, a whole degree of latitude. (Only NMN quotes a range of accuracy. Local radio stations misleadingly quote the position as gospel truth). Satellite passes may be infrequent or the angle poor. Sometimes it is interpolated. Hurricanes are a law unto themselves and go where they will. Only an aircraft flying right into the eye of the hurricane can accurately obtain the data. The aim is to try to predict where it will hit land in time to organise the evacuation of coastal areas and prepare for disaster. Accurate reports allow seafarers to take evasive action or seek out the safest hurricane holes.
A hurricane, as is well known, is a massive heat machine, fueled by heat sucked up from warm seawater. One interesting fact we were told was that last year tropical storm Emily, following close behind the dangerously big Hurricane Dennis on a similar course, never had a chance to develop because Dennis had sucked up so much warm water that the sea surface temperature was reduced by 10 degrees.
Outside the hurricane season the hurricane hunter aircraft do a wide variety of weather and atmospheric research worldwide, emphasising that weather is no respecter of manmade national boundaries. Being operated by NOAA, the hurricane hunter aircraft are civilian and therefore can overfly Cuba which welcomes their valuable contribution to safety.
So next time you hear that aircraft have been sent out to investigate a hurricane, say a prayer for the brave crew being thrown around on their dangerous and most uncomfortable mission so that we can be forewarned. And maybe one day, thanks to the data they collect, we may even know where a hurricane is heading and which island it is going to hit.
