NOAA's Aviation Weather Center

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Historical Perspective

NOAA History

December 1, 1998 marks the 80th anniversary of the first government-issued route forecast for aviation. The forecast was issued for the Aerial Mail Service route from New York to Chicago. This was the second route established by the United States Post Office in the fledgling service. The first air mail route was from Washington, D.C. to New York, begun in May 1918.

Prior to December 1st, the Weather Bureau did provide information to pilots on flying conditions. However, these were generally in response to specific requests on a case-by-case basis. After the Wright Brothers' historic flights on December 17, 1903, interest in aviation increased steadily in this country. But it wasn't until the U.S. entry into the European conflict in April 1917 that the need for more formal weather information became a high priority item, especially for the military.

As the number of air mail routes increased, the Weather Bureau expanded the number of route forecasts to support them. This increase of services in support of aviation marked the beginning of a two-decade long period of rapid expansion of the Weather Bureau as a whole, encompassing everything from substantial increases in budget and personnel to advances in technology and communications. All these changes were driven by the need to know more about the atmosphere in order to improve the forecast service.

The air mail routes consisted of a major terminal at either end and a number of intervening sites that provided fuel and a refuge in case inclement weather prevented the pilot from continuing the flight. Gradually, surface observing sites were established at strategic locations along each route. The observations were relayed in sequence, from one end of the route to the other; hence the term "sequences", referring to groups of surface airway observations (SAOs).

It is worthwhile to take a brief look at the state of the Weather Bureau at the time of this meteorological milestone. The Bureau had increased its surface observing network to around 200 stations at the close of WWI, most of which were east of the Continental Divide. Observations were recorded just twice a day back then, at 8 a.m. and 8 p.m. Eastern time (or, in the parlance of the day, 75th meridian time). The observations were telegraphed back to the Central Office in Washington, D.C., where the data was manually decoded and plotted on a map, then hand-analyzed by the forecaster on duty.

Up to about 1910, very little was known about conditions above the surface. Knowledge gradually increased after the turn of the century as a result of very limited experiments with instrumented kites and tethered balloons. By 1918, the number of kite stations had increased, especially in response to the army's need for upper air data to support its field artillery and fledgling air corps units. When the first route forecast was issued on December 1st, the network consisted of 18 kite stations, 6 of which were Weather Bureau sites. In general, kite data was limited to the lowest 8,000 feet of the atmosphere, which was about the maximum amount of cable capable of being supported by the kite.

Meanwhile, aircraft design and powerplants were gradually evolving in the 15 years since the ground-breaking first flights of the Wright Brothers. Aircraft performance had increased considerably from that first fragile wood-and-canvas biplane powered by a 12 hp engine that gave a ground speed of barely 10 mph. As is often the case, the impending involvement of the U.S. in the European conflict spurred the development of airplanes capable of flying higher, faster and farther than ever before.

This steady increase in the maximum operational ceiling, speed and range of the aircraft of the day is precisely what led to the unprecedented expansion of the Weather Bureau over the next several decades. In order to issue more accurate forecasts of weather conditions on the ground and in the air, the Bureau's forecasters needed more information about the atmosphere to a greater depth than ever before. Yet the state of meteorological knowledge and the technology of the day meant that aircraft performance was increasing faster than the ability of forecasters to predict the flight conditions for the corresponding four-dimensional envelope within which the aircraft operated.

Nevertheless, the state of aviation was still quite primitive, compared to the present. Most aircraft were still fabric-covered wooden frames with multiple wings, although metal framework was becoming more common. The cantilevered-wing monoplane design was just emerging on the aviation scene. Virtually all aircraft were still open cockpit, and most did not provide supplemental oxygen.

Aircraft engines were becoming more powerful, especially with the introduction of the 12-cylinder, 400 hp Liberty engine. When installed in the American-built versions of the D.H.4, originally designed by Englishman Geoffrey de Havilland, it resulted in one of the finest single-engined bombers of WWI. Capable of speeds up to 145 mph, the D.H.4 was faster than most contemporary fighters, with a range of over 400 miles. However, most aircraft of the day operated at speeds of between 80 and 120 mph.

After the War to End All Wars, many surplus military aircraft were utilized to carry the mail over the ever-expanding network of routes. And thus began the Weather Bureau's race to keep up with the rapidly developing aviation industry.