The Zambretti Forecaster is a

weather forecasting Weather forecasting is the application of science and technology forecasting, to predict the conditions of the Earth's atmosphere, atmosphere for a given location and time. People have attempted to predict the weather informally for millennia a ...

instrument used in conjunction with a

barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...

. It interprets the reading of a barometer into one forecast from a large selection of permutations after making allowances for variable factors. These include wind direction, a rising, falling or steady barometer, and the

season A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and pol ...

Negretti and Zambra Negretti and Zambra (active 1850 – c. 1985) was a company that produced scientific and optical instruments and also operated a photographic studio based in London. History Henry Negretti (1818–1879) and Joseph Zambra (1822–1897) for ...

were scientific instrument makers, noted for their barometers. The Forecaster was produced in 1915 as a portable forecaster which needed minimal instrumentation, a simple barometer and an observation of the wind direction, and was easy to calculate with. It was produced as a small disc calculator made of overlaid discs of ivorine, an early plastic. Despite its simplicity, it achieved 90% accuracy for 12 hour forecasts. The original Zambretti algorithm has since been implemented in a number of electronic forecasters.

References

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