The Hurricane Hunters

by Ivan Ray Tannehill

The Air Corps and Navy soon developed their own special methods. From the beginning the Navy preferred the low-level method; that is, they flew by the quickest route to the calm center of the storm, going in at a low level, generally at an elevation between three hundred and seven hundred feet. There are good reasons for this. Weather information—especially the facts they want about tropical storms—is vital to the safe operation of surface ships such as cruisers, destroyers and mine sweepers, and it is also used in the movement of aircraft from and to the decks of carriers. Task forces want to know about the speed and direction of winds at sea level, as well as the condition of the sea when storms are imminent.

It was the aim of the Navy to keep their weather reconnaissance aircraft below the level of clouds, where the aerologist could watch the surface of the sea as much of the time as is possible within the limits of reasonably safe operation. When in a tropical storm, the aerologist guided the pilot around or into the center. Down near the water, say one hundred to three hundred feet altitude, turbulence is apt to be very bad, sometimes extremely violent. Above seven hundred feet, clouds are likely to interfere and this was extremely dangerous at that altitude in those early years because the altimeter which they used to indicate height of the aircraft by pressure of the atmosphere was sometimes badly in error in a tropical storm. If the pilot and the aerologist lost sight of the water’s surface for a few minutes, they suddenly found the aircraft about to strike the precipitous waves of a storm-lashed sea.

Pressure of the atmosphere falls with increase of elevation, roughly one inch drop in pressure for each one thousand feet. If we put an ordinary barometer reading 29.90 inches in a plane on the ground and go up one thousand feet, it will read about 28.90 inches. The pressure altimeter is a special type of barometer that shows elevation instead of pressure. When the pressure is 29.90 inches and the altimeter is set at 0, we go up to where the pressure is 28.90 inches and it reads one thousand feet. But if the pressure over the region falls to 28.90 inches and the altimeter is not adjusted, it will read one thousand feet at the ground and be roughly one thousand feet in error when we go up to where the reading is 27.90 inches.

In ordinary weather, big changes in the barometer take place slowly and there usually is plenty of time for correction. In a flight into a hurricane, big changes take place rapidly. The change caused by the plane going up may be confused with the drop in pressure in the hurricane. If the plane is in the clouds when these changes take place, the pilot may have a frightening surprise on coming into the clear again. More recently, the hunters have been equipped with radar altimeters which give the absolute altitude for check. They send a radar pulse downward and it is bounced back from the sea surface to the instrument. The time it takes to go down and back depends on the height—the higher, the longer it takes—and the instrument is designed to give the indication very accurately in feet. Thus, the radar altimeter removed some of the dangers of low level flight.

So the Navy hunters moved in at low levels, preventing the “mush from becoming a splash” as they put it, and although their experienced pilots were marvelously efficient in flying on instruments in clouds or “on the gauges,” they kept the white welter of the storm-lashed sea in view whenever possible. Of course, it is not possible to fly straight into a storm center. The big winds carry the plane with them and so the pilot might as well use the winds to good advantage—he will go with them to some extent, whether he likes it or not.

If we imagine ourselves in the center of the hurricane, facing forward along the line of motion of the storm itself—not the motion of the winds around the center—we know that the safest sector to fly in is behind us on our left, and the worst is in front of us on our right. At the left rear, there is likely to be better weather—less dense cloudiness and not so much rain. The winds are not so violent. So the Navy pilot flies with the wind. He goes in until he has winds of, say, sixty miles an hour. He puts the wind on the port quarter and this carries him gradually toward the center of the hurricane.

When he gets the wind speed to suit him, he brings the wind between the starboard quarter and dead astern and flies ahead to the point where he thinks he has the best place to go for the center. According to Commander N. Brango, one of the Navy’s top specialists in hurricane navigation by air, “Choosing the proper run-in spot is tricky business, for it is the point at which the wind is the reciprocal of the storm’s direction of motion. The pilot must watch for this point carefully, as he may pass it quickly; if he does there is imminent danger that the drift may carry the aircraft into the most severe quadrant of the hurricane.” So the pilot goes into the center without wasting any time. Delay results in fatigue and it is important that the men be freshly alert. The pilot puts the wind broad on the port beam and he cannot possibly miss the eye. The next thing, the plane is in that amazing region where the sea boils, the breezes are light or missing altogether, the rain has ceased and the clouds are arranged in circular tiers, like giant spectators in a colossal football stadium.

This is a marvelous place. The crew is at ease. Coffee goes around. In the last few moments before coming into the eye, the craft leaks like a sieve. Everything is wet but the squirting from a hundred crevices in the plane ceases in the center and now it is possible to do some paper work. The aerologist is busy with the weather code and the radio man begins pounding out a message. They circle around. The pilot takes them up to maybe five thousand feet altitude and back down again, circling around.

And then the time comes to leave the center. The pilot calls a warning over the phone and there are two or three wisecracks. But this departure from the eye is dangerous. The plane begins to catch the shear of powerful winds around the center. Here a man can get thrown around violently and be seriously hurt, if he fails to get a good grip on something or neglects his safety belt.

Now the pilot sets the wind broad on the starboard beam and both he and the co-pilot hang onto the controls. This is rough going and there may be some surprises, but after a little they are out of the big wind circle and the navigator thinks the gales are down to something like fifty knots. The pilot sets course for the Navy airfield and the staccato notes of the radio continue to carry vital weather information to the forecasters. On this subject, Captain Robert Minter, an old hand, at one time in charge of aerology in the Office of Naval Operations, is full of enthusiasm. He guaranteed that the Navy could get a ship off the ground on a hurricane probe within an hour after the Weather Bureau forecaster asked for the information.