by Al Roker
As a student of humidity, Isaac Cline read tables (sometimes built into the hygrometer for quick reference) showing the exact humidity ratios. But experienced forecasters know the rough ratios by heart.
We concern ourselves with humidity mainly on hot days. When there’s lots of moisture in the air, it can’t accept much more moisture, and that means warmth has a harder time leaving our bodies via perspiration. With a temperature of 95 degrees Fahrenheit and a dew point of 90 degrees Fahrenheit, you’ll get a relative humidity of nearly 86 percent—quite uncomfortable. When air temperature and dew point are identical, humidity is said to be 100 percent. We really don’t like that.
There were other kinds of hygrometers as well, developed during Isaac Cline’s early career as a meteorologist. One, called a psychrometer, compared a wet thermometer bulb, cooled by evaporation, with a dry thermometer bulb.
And in 1892, a German scientist—he had the unfortunate name of Richard Assmann—built what was known as an aspiration psychrometer for even more minute accuracy. It used two matched thermometers, protected from radiation interference by a thermal shield, and a drying fan driven by a motor. By 1900, when Isaac Cline was working in the weather station in the Levy Building in Galveston, hygrometer science was at its apex.
But perhaps the most important element in weather forecasting is the barometer.
The role of barometric pressure—air pressure—is counterintuitive. We can directly feel the phenomena measured by anemometers and hygrometers—wind speeds and relative humidity: wind knocks us around and humidity makes us sticky. But the sensations caused by air pressure work differently from the way we might expect.
That difference has to do with the very nature of air. Usually we don’t think much about air. While we know it gives us oxygen, breathing is largely unconscious. We notice air when it’s very still or very windy. And we notice air when it stinks.
Otherwise we generally ignore the air. We imagine it as nothing but a weightless emptiness.
But air does have weight. That weight exerts pressure on the Earth’s surface, as well as on everything on the Earth: human skin and inanimate objects. We refer to the pressure of that weight as “atmospheric pressure,” and we measure it with a barometer.
When more and bigger molecules gather, air’s weight increases, and the atmosphere bears down snugly on all surfaces. We call that effect, not surprisingly, “high pressure.” The strange thing, though, is that high pressure—all that heavy weight of air—makes us feel freer, more energetic. It makes the air feel not heavier but lighter.
That’s because where pressure is high, relative humidity is suppressed. Warmth can’t lift as easily from the surface of any object—including from the Earth’s surface. Warm air currents are held at bay, moisture is blocked, winds remain stable. Rain, lightning, and thunder are discouraged. High pressure usually means nice weather.
By the same token, when we complain that the air feels heavy—on those days of sluggishness, when we feel as if we’re struggling through a swamp—heaviness is not really what we’re feeling. Just the opposite. On those days, the air has less weight, lower pressure.
The result, usually, is just some unpleasantness. That’s because lighter and fewer molecules in the atmosphere cause atmospheric “lifting.” Heat and moisture lift upward from all surfaces. The humidity gets bad.
But when barometric pressure falls low enough, winds may be expected to rise, clouds form, and rain, thunder, and lightning follow. With very low air pressure, things aren’t just unpleasant. They’re dangerous, sometimes deadly.
Barometers for measuring pressure had been part of experimentation in natural science since the 1640s, well before modern weather forecasting. For a long time, it just seemed interesting, and possibly useful, to know that atmospheric pressure exists at all. Or to see that it can do work—like pushing mercury upward in a column.
But soon people began to apply the science. They used pressure readings not only to note the existing weather but to predict future changes in weather. One scientist graduated the scale so the pressure could be measured in exact increments. Another realized that instead of pushing mercury upward, the scale could be turned into a circle to form a dial; that enabled far subtler readings.
Yet another change came with the portable barometer. Using no liquid, and therefore easier to transport on ships, the portable barometer took the form of a small vacuum-sealed metal box, made of beryllium and copper. Atmospheric pressure made the box expand and contract, thus moving a needle on its face. A barometer like that could be carried in a pocket by a ship’s captain. He could watch the pressure fall and know that he was sailing into a storm.
Just before Isaac Cline began studying, the widely traveled Vice-Admiral Robert FitzRoy, of the British Royal Navy, formalized a new system for detailed weather prediction based on barometric readings. FitzRoy had served as captain on HMS Beagle, Charles Darwin’s exploration ship, and also as governor of New Zealand. His idea was to go beyond just noting existing and future weather conditions. He found ways of communicating conditions from ship to ship. That aided safety at sea.
By the mid-nineteenth century, a large barometer of FitzRoy’s design was set up on big stone housings at every British port. Captains and crews could see what they were about to get into. In 1859, a storm at sea caused so many deaths that FitzRoy began working up a system of charts that would allow for what he called, for the first time anywhere, “forecasting the weather.”
Using the telegraph, which had recently become feasible for this kind of work, FitzRoy established an interconnected group of weather stations that made daily reports to a central station. Soon he was directing a system of storm-warning cones, hoisted at major ports, in response to information coming in from all stations. Boats could be ordered to stay at port under certain conditions. Using terms like “gale warning” and “small craft warning,” the modern weather bureau, familiar for decades to come, had been born.
And all of that was based on using a barometer for measuring rising and falling air pressure.
The military discipline of the training school at Fort Myer, Isaac Cline felt, fit neatly with the unflagging regularity, neatness, and precision that he began to see as critical to good weather reporting. Along with the use of instruments, the students studied the classic Weather Service and Signal Corps texts: Loomis’s Meteorology, Myer’s Manual of Signals, Instructions to Observers, Pope’s Telegraphy, and The Handbook for the Signal Corps. And they took strict exams on both theory and practice.
As graduation neared, what Cline and all of his fellow trainees wanted most was a job as assistant weather observer at a Weather Service post. Only sixteen men passing the Fort Myer course with the highest grades would get such an assignment.
Cline passed sixteenth.
He’d barely made the cut, but he was an observer. Cline was immediately assigned to the weather station at Little Rock, Arkansas. The Rocky Mountain locust had been ravaging the countryside. Cline’s assignment—along with taking and reporting weather readings—was to study the influence of weather conditions on the development and migration of that destructive insect.
By the time he arrived in Galveston, Texas, in 1889—only six years after taking up his first assignment in Little Rock—Isaac Cline possessed a remarkable trove of weather expertise. The Rocky Mountain locust had mysteriously disappeared from the West. Cline never got to know much about it.
But his barely making the cut as an observer certainly didn’t hold him back. Maybe it even inspired his commitment to excellence. In his early years as a weatherman, Cline learned how to make extremely accurate observations and remarkably reliable forecasts. When the weather observer at Fort Smith, Arkansas, died unexpectedly of a heart attack, Cline was sent there to take over temporarily. Soon he was in charge of the station at Fort Concho in Texas.
The move to Fort Concho began Isaac Cline’s long and fruitful relationship with the nation’s biggest state, which was just on the ver
ge of its fabled boom. A spur from the mighty Chisholm Trail brought thousands of head of cattle thundering into market in Fort Concho. The Texas & Pacific Railway had recently made nearby Abilene a stock-shopping point—the classic cowtown.
Also nearby, San Angelo had only recently been a lawless boom town full of gunfighters and saloon poker games. Range wars among various kinds of ranchers and family farmers, old feuds between Rebels and Yanks—all contributed to the wild mood of the Texas frontier.
But in contrast to the rowdy action around him, what Isaac Cline did all day was take readings, three times a day, from the barometer, the thermometer, the anemometer, the weathervane, the rain gauge, and the hygrometer; and combine those readings with eyeball observations of the type and movement of clouds and the amount of sun and rain. Then he would code those observations and telegraph them to Washington.
He had to be sure to be take the observations at exact times in order to allow Washington to coordinate them with readings taken at those same exact times at all the stations in the country. Perfect coordination contributed to a simultaneous observation of the continent at 7:35 A.M., 4:35 P.M., and 11:00 P.M. Washington time.
But Cline also took three other observations at local time: 7:00 A.M., 2:00 P.M., and 9:00 P.M. He took a seventh observation at noon. If anything seemed worrisome at noon in comparison to earlier readings, he was to telegraph his concern to Washington.
Then, exactly at sunset, he took another observation, describing the appearance of the western sky, the wind direction, cloudiness, barometer, thermometer, and hydrometer readings, and rainfall since the preceding report. That was telegraphed with the late-night report.
The office in Washington put together all this punctilious observation and simultaneous reporting from a multitude of stations in big sections of the country and sent forecasts to thousands of rural and urban post offices around the country. Above each post office, huge signal flags—up to six by eight feet—relayed the forecast to farmers, businesspeople, and anyone else who needed to know. Reports also went to newspapers.
At the weather stations, regulations were strict, thanks in part to the military discipline under which the entire service operated. And Isaac Cline was a full supporter of that strictness. He required complete adherence to the rules—from himself and, as he moved up the Weather Service ladder, from his assistants. Clerks were to keep desks, drawers, and file cases neat and clean. No paperwork was to be strewn about: all papers were to be returned to their files immediately after use and at the close of each day’s work. Every Saturday, a property officer policed and set up all rooms, halls, stairways, closets, and cellars.
There was to be no taking medicines at the watercoolers. No talking outside about what goes on at the office. No visitors, except on business, and visitors on business must transact it, then leave. No casual conversation. No writing private letters. No reading the paper. Business conversation only—carried on in a low tone of voice.
So it’s funny to think of Isaac Cline, with his fussy dedication to precision, responsibility, and routine, exemplifying anything of the improvisational spirit of young Texas. He’d quit smoking after his first few cigarettes. He avoided playing poker, first playing only with no ante and then breaking the habit altogether. He disapproved of the deleterious effects of alcoholic beverages. An abstemious weather forecaster doesn’t seem the ideal exemplar of growth in Texas.
And yet Cline was an army officer, a representative in Texas of federal authority. As such, his role was special. And Signal Corps officers were cocky. They didn’t wear uniforms. Even when under direct military orders, they were empowered to act as mavericks (originally a Texan term for wayward cattle). They carried out operations as they saw fit and liked to think of themselves not as normal army but as specialists, like the Army Corps of Engineers.
So Cline had his own kind of genteel machismo. It was based on his sense of himself as a gentleman, a federal agent, a scientist, and a doctor. And while a professional weatherman might not have made much of an impression on a pistol-happy drunk reeling out of a Fort Concho saloon, when Cline arrived in Texas, both the Weather Service and its parent, the Signal Corps, were in fact playing important roles in the key conflicts of the American West.
Indeed, when a Weather Service associate of Cline’s, Charles F. von Herrmann, became attached to the U.S. Army in the Southwest, he amazed the regular troops with the success of his innovations. This was during the effort to defeat Geronimo, the Apache leader who continued to elude the U.S. Army. Into the hunt for Geronimo, the Weather Service introduced heliography, a signaling system using no wires but only sunlight on a mirror. Flashing in Morse code via quick pivots of the mirror, a heliographer can send messages instantly, across great distances, where no other means exist.
Isaac Cline’s colleague von Herrmann thought heliography might serve as an ideal way of fighting Indians in the deserts and plains of New Mexico and West Texas. At first the system just seemed silly to many of the U.S. soldiers bent on tracking down Geronimo’s men. Heliography looked like a low-tech gimmick with no useful application.
Von Herrmann, undeterred, commanded army squads in setting up a complex system of heliographs in the theater of war. The New Mexican and Texan deserts possessed not only long-range, unobstructed views but also a degree of dryness in the air that made tiny details startlingly clear. Von Herrmann sited the mirrors on the bluffs and buttes above the flat plain. As he moved from mirror to mirror around the countryside, he became a bizarre sight. To protect his peeling red face from the New Mexico sun, he was wearing a wire frame secured to his waist and holding a white canvas tent over his head.
After much time-consuming experimentation—during which he had to suffer the skeptical mutterings of his troops—von Herrmann staged a triumph. The men stood amazed as he sent a comprehensible message ninety miles instantaneously. By setting up relays, the mirrors could soon send similar messages over 200 miles.
Some U.S. generals later claimed that the Indians under Geronimo were so amazed by the flashes of light that they were awed into surrender. But Geronimo was well acquainted with signaling over long distances, and he’d seen light and mirrors before. The generals’ claim seems more than unlikely.
More realistically, the troops themselves noticed that the Indians stayed away from areas where they knew heliographs had been stationed. Geronimo and his men knew exactly what the mirrors did: talking with sunlight, as Geronimo himself later put it, making it impossible for him to elude capture.
Not only aiding communication between U.S. troops, but also tracking and mapping Indian troop movements over a huge expanse, heliographs helped the United States close in on Geronimo. The modern science of meteorology gave the United States a tactical advantage that it had been lacking in the Apache wars.
Von Herrmann’s next assignment was to pack up Isaac Cline’s Fort Concho weather station and safely transport all the delicate instruments to Cline’s new assignment. This was in that once wild cowtown, rapidly becoming a real city: Abilene itself. There Cline launched what the Weather Service was now calling a First Order Weather Observation Station. That meant the station would employ all of the latest technology in use by the service at that time. The investment was a sign of federal confidence in the importance of Texas.
Cline’s First Order station in Abilene made use of self-registering instruments. Too expensive for smaller and less important stations, self-registration added a tricky and impressive feature to the classic tools of weather observation. In less expensive arrays, a weatherman has to write down all of the readings, taken at every interval, and keep them in tables. Downsides are the time involved, the tedium, and the natural potential for human error.
But by connecting a nib on a wire to the instrument’s dial or movement, a machine could be forced, by the very laws of physics that were creating the reading itself—evaporation of ether through a hygrometer tube, water rising in a rain gauge, pressure expansion and contraction in a barometer�
�to inscribe a mark on paper. That paper, thanks to tiny wheels moved by similar action, might unwind from a spool or slide vertically as the marks were made. With clockwork, the marking of the pen and the movement of the paper could be related with exact precision to the passing of time. And since, by the late nineteenth century, such mechanics could also be enhanced by motors and electricity, there was potential to bring down the costs of operating and maintaining these delicate yet labor-saving self-registering instruments.
In Abilene, Isaac Cline was not only able to make minute observations automatically but also to study the old rainfall and temperature records of the area. On that basis, he began to publish studies that became instant classics of modern scientific weather observation. Their titles don’t sound exactly thrilling: “Precipitation and Its Sources in the Southern Slopes,” “Summer Hot Winds on the Great Plains,” and so on. But they show his growing interest in becoming not merely a fine weatherman but also a major contributor to the science itself.
So by the time he came to Galveston in 1889, Isaac Cline had operated the most sophisticated weather forecasting technology of his day. He was a published expert in all kinds of weather phenomena. And he was developing a special interest in hurricanes.
Not all of the experience Cline brought to Galveston was meteorological. Back in Little Rock, finding himself with time on his hands, he’d taken up the study of medicine. Somewhat amazingly, he was now in fact, an M.D., having attended the University of Arkansas Medical School, only three blocks from the Little Rock bank building that housed his first weather station.
Those two vocations, meteorology and medicine, complemented one another ideally, Cline felt. For one thing, he said, each gave his mind rest from the other. That’s an indication of Isaac Cline’s approach to recreation.
He was writing his weather studies on his own time. He called that recreation too.