loomed from time to time ghost-like structures rising like huge white
marble monuments through the cirrostratus fog. Actually these were
shafts of supercooled water which rose vertically and passed out of
sight overhead as we viewed them from close at hand. Each time we passed
through one of these shafts the leading edge of the wing accumulated an
amazing extra coating of rime ice. This kind of icing would have been
easy to shake off if the plane had been fitted with standard de-icing
equipment. But it was not. We were so close to the center of the storm
by the time the icing was discovered that the shafts were too numerous
to avoid.
"Pilot Eastburn punched me and pointed to the indicated airspeed gage.
It stood at 166. 'At this elevation this plane stalls out at 163,'
Eastburn said, 'and in this thin air there is no recovery from a stall.'
He continued, 'We have got to get out of here fast!' I nodded agreement,
feeling a bit sheepish about the whole thing. After all, hadn't Vincent
Schaefer, of General Electric, just a few months earlier demonstrated in
the laboratory that water vapor could be cooled to a temperature of -39°
before freezing set in? But in the turbulent circulation of a
hurricane--this was fantastic! Unbelievable! But there certainly was no
guesswork about that six or eight inches of rime ice on the leading edge
of the wing!
"We got out of there all right, and fast, but we had to do it in a long
straight glide; the plane was simply too loaded with ice and too near
stall-out to risk the slightest banking action."
After all, the atmosphere is a mixture of gases and it obeys the laws of
gases. If the scientists assume that the big storm has a certain
structure and a certain circulation of air in its colossal bulk, there
are definite conclusions to be drawn concerning the physics of this
giant process in the tropical atmosphere. But if it turns out that the
assumptions about the structure and circulation are wrong, the
conclusions of the physicists may be exactly opposite to the truth. The
results of years of study, calculation and discussion seem to be
overthrown in one moment as a superfortress plunges into a vital section
and the crew sees things that ought not to be there!
Most important in the 1947 storm was the fact that conditions at a
height just below forty thousand feet were such as to go with a
circulation against the hands of a clock at maybe 130 miles an hour. The
plane going in that direction had a tail wind of ninety miles an hour.
And yet, the students of hurricanes during the past century were sure
that at some height well below that level the winds blew outward in a
direction _with_ the hands of a clock. In agreement with this
conclusion, most of the scientists had made up their minds in recent
years that the circulation in the lower part of these storms usually
disappears at twenty to thirty thousand feet. And so, if we are to
account for the removal of air in this great space extending down to the
sea surface, it must have been done well above forty thousand feet in
this case. And up at this height the air is so thin that it is almost
inconceivable that it could blow hard enough to account for air removal
in the average hurricane. On the other hand, this was a mature storm and
it may be that at this stage no air was actually being removed from the
system and that the gigantic circulation of the full-grown monster is
self-contained.
While it would be extremely interesting to understand the magic by which
nature so slyly removes the air from the hurricane under our very noses,
the practical question is whether or not its escape at the top is geared
in any way to the forward motion of the main body of the storm. The
answer to the first question may give the answer to the second, and
possibly also to the third question: what causes a hurricane to increase
in intensity--to deepen, as the weatherman says, having reference to the
fall of pressure in the center? He thinks of it as a hole in the
atmosphere.
This 1947 hurricane illustrates the great difficulty of finding answers
to our questions. But in any case, this was just one storm and all of
them are different in one way or another.
But to go back to the story of the guest rider from the Weather Bureau,
Robert Simpson, the story is not complete without a brief account of the
flight into Typhoon Marge. It raised its ugly head in the Pacific in
August, 1951, and on the thirteenth had passed Guam, a storm not well
developed but of evil appearance, showing signs of growth. That evening
Simpson arrived from Honolulu, where he was in charge of the Weather
Bureau office. He accepted an invitation from the Air Force to visit
Marge and on August 14, six hours after he alighted from Honolulu, was
airborne in a B-29 and on the way.
In a few hours Marge had grown into a colossus. It was nearly one
thousand miles in diameter, with winds exceeding one hundred miles an
hour in an area more than two hundred fifty miles in diameter. When the
hurricane hunters entered the center and measured the pressure, it
proved to be one of the deepest on record--26.45 inches at the lowest
point. From plane level, the eye was perfectly clear above, forty miles
in diameter and circular. The massive cloud walls around the eye rose on
all sides to thirty-five thousand feet, like a giant coliseum. The west
wall was almost vertical, with corrugations that suggested the galleries
of a gigantic opera house.
In the center, below the plane, they saw a mound of clouds rising to
about eight thousand feet, an unusual feature, but one that has been
observed in other tropical storms. The crew spent fourteen and a half
hours in the central region of this huge typhoon, getting data at levels
from five hundred feet up to twenty thousand. Down in the lower levels,
they found a horizontal vortex roughly five thousand feet in diameter,
extending from the cloud wall of the eye like a tornado funnel, in which
they encountered very severe turbulence. Another collection of data was
added to the growing accumulation and with it the notes of unusual
phenomena observed. Since that time Simpson has flown several hurricanes
in the Atlantic.
Now it is abundantly clear that the hurricane hunters are looking for
many important facts aside from the location of the tropical storm and a
measure of its violence. There are many questions unanswered. Here in
the warm, moist winds that blow endlessly across deep tropical waters
there are mysteries that have challenged man for centuries. Turning to
their advantage every discovery that science has pointed in their
direction, the hurricane hunters have cheated the big storms of the West
Indies of a very large share of their toll of human life. In struggling
to solve the remainder of the problem, they have two virtues that will
ultimately bring success--ingenuity and persistence. They push on
tirelessly in several hopeful directions.
The Navy has taken advantage of the strange fact that when a tropical
storm comes along it literally shakes the earth. There are little
tremors like earthquakes but very much smaller. The Greek word for
earthquake is _seismos_ and by putting _micro_ in front, meaning very
small, we have the word _microseism_. And so, the storm-caused little
tremors are called microseisms or slight earthquakes. The instrument
which registers these tremors is called a seismograph. When the earth
moves, even a very little, a body on the earth tends to hold its
position and the earth moves under it. In a small earthquake, a chair
will move across the floor. This kind of motion can be registered by
instruments.
In 1944 the Navy installed seismographs and began keeping records of the
slight tremors caused by hurricanes and typhoons. These studies have
shown that a tropical storm at a distance produces a small tremor which
becomes stronger as the storm center gets nearer. No one knows exactly
how the storm shakes the earth and causes the tremors. There are some
strange things about this. It seems that these microseisms are carried
along in the earth until they come to the border of a great geological
block and then do not pass readily into the next block. So there are
places in the Caribbean where the tremors weaken as they come to a
different earth block and this interferes with the indications picked up
by the instruments. The fact is that microseisms give signs of the
existence of a tropical storm and sometimes serve to alert the storm
hunters, but they are by no means good enough to replace the use of
planes in tracking them. But the studies of microseisms are being
continued.
For many years static on the radio, better known as atmospherics or just
"sferics," has been used in the endeavor to locate or keep track of
storms. At first the Navy tried it on West Indian hurricanes. The
instruments used will find the direction from which the sferics come
when they are received in a special tube. In more recent years, the Air
Force has used this scheme. It works to advantage in finding
thunderstorms, but tropical storms are so big and the sferics are not
found in any regular pattern around the central region. After years of
trial, it has been concluded that this scheme is not good enough to
replace other methods.
Of all the methods of this kind, radar is by far the best. But as the
radar stations on shore and the radar equipment on aircraft have
increased in numbers and have been improved to reach greater distances,
some new troubles have arisen. For many years the hurricane hunters took
it for granted that a hurricane has a clear-cut center which moves
smoothly along a path that is a straight line or a broad curve, but in a
few cases is a loop or a sharp turn. In other words, the center does not
change size and shape or wiggle around. In the past, when an observer on
a ship or on a plane reported a center of an odd shape or had it off the
smooth path the hunters were plotting, they said the observer had made
an error.
Now as the hunters have begun watching hurricane centers close by on the
radar, they see them changing shape and wiggling around. In fact, as
stated in a few cases in earlier chapters, they have seen false eyes and
have been confused by them until the true eye came into view on the
radar scope. If the true eye describes a wiggly path and changes size,
the hunters can draw the wrong conclusions about its direction of motion
unless they wait a while to see if it comes back to the old path. The
hurricane is a little like an eddy or whirl in water running out of the
bottom of a bowl. It is a violent boiling eddy that twists and changes
shape, and in a substance as thin as the atmosphere these motions are
not steady to such a degree that the observer can reach a quick
decision. At any rate, it is now apparent that the observers on ships
and aircraft did not make as many errors as was thought several years
ago.
There is another aspect that must be kept in mind. Radar shows areas
where rain is falling around the center of a hurricane and so the
center, having no rain, stands out as an open space on the radar scope.
This is very good if the storm has rain all around the center, but some
of them have very little rain on the southwest side, and in some cases
there is none to return an echo to the radar. In such a case, there is
only one side to the storm echo and the location of the center is not
revealed. Of course, these facts are known to the experienced radar men,
but they should be known to everybody interested in hurricane reports;
otherwise they are likely to expect too much accuracy from observations
of this kind.
For these and other reasons, the man on the aircraft has a very great
advantage in daylight, for he can see clouds of all kinds, measure the
winds and, by moving through the storm area at the speed of the modern
plane, he can see a large part of it in a short time. To find a
substitute for aircraft reconnaissance is going to be extremely
difficult. But at night the situation is quite different. The airman is
unable to see much without radar, except on a moonlight night and that
is not very good.
One suggestion that has been put forward by a number of different people
in recent years is that a balloon be flown in the calm center and
followed by radar or radio, thus keeping track of the storm's motion. It
is possible, of course, to fix a small rubber balloon (perhaps eight to
ten feet in diameter) so that it will remain at the same height for a
fairly long time. By one method the rubber balloon is partly filled with
helium and covered loosely with nylon. The balloon expands as it rises,
becoming less dense as the atmosphere gets thinner. It continues to rise
until it fills the nylon cover and cannot expand further. After that,
its density becomes the same as the air at some level previously chosen,
and from there it drifts along without rising or descending.
It is the idea that the obliging balloon would drift here and there in
the vagrant breezes of the eye, but when it came to the edge of the
powerful wind currents around the outside of the eye it would be guided
back in. No experiment has been carried out to prove that this would
happen but such trials have been scheduled and will be made at the first
opportunity. There is one difficulty. The question is how to get an
inflated balloon into the center and release it under proper conditions.
One of the men who has worked on a scheme of this kind is Captain
Bielinski, the Air Force officer who broke his hundred-dollar watch in a
typhoon and solemnly swore he would find an easier way to do it. He
calls his device "Typhoon Homer." He has worked on it for four years,
spending much of his own time and money.
There are reasons to believe that, after a few experiments, a height
could be found where the balloon would stay in the eye. So far as we
know, birds trapped in the center are held there. After battling
hurricane winds, they are so exhausted on getting into the center that
they could not remain there if the wind circulation tended to suck them
out into the surrounding gales.
Bielinski concluded that the balloon could not be thrown out from a
plane in even a partially inflated condition. The blast of air on
leaving the aircraft would destroy it or put it out of commission. So he
has an uninflated balloon and bottles of gas, a small radio transmitter,
and a float, all attached to a parachute.
The bottles and radio would be thrown out, the parachute would open, and
the gas would go through a tube from the bottles into the balloon. The
float, with a long line to the balloon, would rest on the water and
provide an anchor for the apparatus. The radio would send signals every
hour, the operators on shore would figure its location by direction
finding, and there would need to be no further aircraft flights into
that storm. The device, according to Bielinski, would continue to
operate for seven days.
Robert Simpson and others have had similar ideas, some favoring a device
that could be followed by radar, but Simpson prefers the radio
transmitter. To find out how the air circulation in the calm center
would affect the balloon, he planned experimental flights in hurricanes
to release a chaff made of a substance that could be followed by radar.
He tried it in 1953 and again in 1954, but something happened in each
case to prevent the experiment from being carried out. In one case, for
example, nearly everything was in readiness for an experimental flight
to take off when Edward Murrow of CBS arrived in Bermuda with his crew
and apparatus to put Hurricane Edna on television, and Simpson was moved
to the back of the plane. He and all others connected with it, including
Major Lloyd Starret, who had been brought in from Tinker Air Force Base
to work with Simpson, were glad to make way for a public service
program. But this shows one of the reasons why developments of this
kind, which depend on opportunities in only a few hurricanes a year,
take a discouragingly long time. There was no chance to test Bielinski's
device, or any other, for that matter. There have been laboratory
experiments also on a device to deflect the air streams around the bomb
bay of the aircraft so that a partially inflated balloon could be safely
released in the eye of a storm.
These devices are mentioned here to show the trend of thought. Something
similar to this may eventually serve to replace a large share of the
hazardous aircraft flights, but even if the center is satisfactorily
located in such a manner, much useful information on the size of the
storm, the force of its winds, and other data will be determined in many
cases only by aerial reconnaissance. With this in mind, both the Air
Force and Navy are substituting bigger and better aircraft for this
purpose.
The old B-29 Superfortress is being "put out to pasture," as they say in
the Air Force. The higher, faster, and farther flying Boeing B-50's are
replacing them, not only in hurricane reconnaissance but in the daily
flying of weather routes to help fill in the blank spaces on the world's
weather charts. The B-50's will go ten thousand feet higher than the
B-29's. Another advantage that appeals to the hurricane hunters who fly
on these missions is the electric oven, standard equipment on the B-50,
which will furnish hot meals at favorable times on the route, instead of
sandwiches and thermos coffee. The Navy, not to be outdone, is coming
out with the Super Constellation, which is being modified for hurricane
reconnaissance to replace the P2V Lockheed Neptune recently used.
As each new season comes, the hunters are wiser and better equipped. The
battle with the hurricane is joined. It is something to worry about,
like war and the H-bomb. At the end of the 1954 season, the executives
of the big insurance companies were in conference with grave faces.
Property damage from Carol, Edna and Hazel had mounted upward to around
a billion dollars. Reports had been circulated to the effect that the
slow warming of the earth in the present century is bringing more
hurricanes with greater violence and paths shifting northward to
devastate areas with greater populations. There was speculation about
the effects of A-bombs and H-bombs on hurricanes.
All this trouble comes from water vapor in the atmosphere. Without it,
the earth would be a beautiful place but useless to man. Even over the
tropical oceans it rarely exceeds five per cent of the bulk of the air.
In other regions, it is much less. But it is this vapor, constantly
moving from the oceans into the air and spreading around the world, that
builds the stormy lower layer of our atmosphere--the troposphere--where
clouds and storms, snow and ice and torrential rain, thunderstorms,
hurricanes and tornadoes thrive in season. Such tremendous energy is
needed to carry billions of tons of moisture from the oceans to the
thirsty land that all of these rain and storm processes are maintained
on the borderline of violence.
Here at the bottom of the atmosphere the vapor absorbs the heat radiated
from the sun. There is a swift drop in temperature as we go aloft. Moist
air pushed upward becomes cooled and ice crystals, water droplets,
snowflakes, are squeezed out. Clouds form, beautiful in the sunset,
gloomy on a winter day, threatening as the summer thunderstorm shows on
the horizon, fearsome as the winter blizzard takes command of the plains
and valleys. Here is water vapor coming to the end of a long journey
from the surfaces of distant seas. From here it goes to the land and
begins another long journey, in the rivers and back to the oceans. But
on the way to us, violence may be one of the principal ingredients. We
can't live without it and we have trouble living with it.
When this lush flow of water vapor from the tropical ocean to the
atmosphere becomes geared in some special manner to swiftly-moving air
from other regions, the process seems to get out of nature's hands.
Upward motion begins on a grand scale. Converging streams of air are
twisted by the spinning of the earth on its axis. And just as men begin
to see the picture, nature draws a veil by the condensation of water
vapor. Under this darkening canopy, violence grows with startling
swiftness. The water vapor that drew the curtain now releases energy
alongside of which the A-bomb shrinks to insignificance.
Far below the sea surface, the solid earth trembles. Avalanches of water
are torn from the ocean and hurled down the slopes of the gale. A
colossal darkening storm begins to move across the ocean. It sucks
inward the hot, moist lower atmosphere and brings it along with it,
using the vapor to feed its monstrous, seething caldron. Down here at
the surface of the earth, its winds are warm and humid. Its
tentacles--octopus-like arms--reach out with gale-driven torrents of
rain and begin picking everything to pieces. After hours that seem like
days, the central fury of the earth-blasting storm begins its
devastation of man's possessions.
And as it has proved to be unquestionably true that no two hurricanes
are exactly alike, so it is evident now that the same hurricane is
subject to massive changes from day to day. It has a life history. Like
the caterpillar that is transformed into the cocoon and then into the
butterfly, the tropical storm goes through definite stages. The problems
involved for the hurricane hunters in each of these distinct stages
demand separate solutions. Like a living thing, the monster has infancy,
youth, middle age and decline.
In infancy, its malevolent forces are directed vigorously toward the
mysterious removal of large quantities of air from above its gale-swept
domain. The excessive heat and moisture of its birthplace yield far more
energy than is needed to keep its mighty low-level winds in motion.
In youth, it is extremely violent and the removal of air brings
exceedingly low pressure into its center. Its outer parts become
ominously visible through the condensation of moisture on a grand scale,
cloaking its internal mechanism. Its destructive forces spread. In this
stage, the removal of air in upper regions continues in excess of the
inflow at the bottom in proportion to the horizontal expansion of the
system.
In middle age, its violent forces are directed toward maintenance of the
colossal wind system. The total energy it can derive from heat and
moisture no longer produces an outflow above in excess of the inflow of
air at the bottom. It expands in the vertical and its visible parts push
against the stratosphere. As it moves farther away from its birthplace
and the available energy begins to decline, it dies. For a few days
nature's processes for the transport of moisture from the oceans to the
thirsty continents have run amuck. Life and property suffered while
torrential rains fell.
So it is clear that in life the monster thrives on heat and water vapor.
Down at sea level it is a warm phenomenon. Only the heated air of the
tropical regions can hold enough moisture to feed the giant.
But up above, the full-grown hurricane is not a warm storm. Hunters
perspire at low levels but not in the top of the storm. There are icy
corridors through currents of air robbed of their heat by the monster
below. Pillars of supercooled water push upward into the thin
atmosphere. Snow flies with the shuddering winds at the top of the
troposphere. It is colder up here above the tropics than it is above the
poles. The fingers of the gale tremble with the cold and seem to make
gestures in defiance of the sun shining through the stratosphere. Water
vapor in great quantities has been carried high in the atmosphere and
nature seems powerless to bring equilibrium until land or cold water at
the earth's surface below shuts off the abundant supply of energy. And
when it does, the monster dies as it was born, hidden behind a veil
produced by lingering cloud masses derived from the vapor that gave it
life.
In the last few years, men have had the courage to fly into these
monsters. Some day, when other methods are used, people will look back
in amazement at these brave events. Here they can see how it happened,
how it was done, and feel admiration for the men who did it--the
hurricane hunters.
[Illustration: _IVAN RAY TANNEHILL_]
was born in Ohio, where he obtained both his degrees in science at
Denison University. While a boy in his early teens, he became intensely
interested in birds, stars and the weather. After finishing college, he
joined the Weather Bureau in Texas and a year later went through a
vicious hurricane at Galveston.