Zambretti Forecaster – a Weather Forecasting Instrument

The Zambretti Forecaster is a weather forecasting device that works in tandem with a barometer. The Zambretti algorithm is based on a weather forecasting instrument developed by Negretti and Zambra in the mid-1800s. It translates a barometer reading into a single forecast from a large number of permutations after accounting for variable factors. Wind direction, a rising, falling, or steady barometer, and the season are all examples.

The Zambretti Forecaster is a weather forecasting tool in the form of a circular slide rule that was introduced by the company Negretti and Zambra in 1920.

Negretti and Zambra were makers of scientific instruments, particularly barometers. The partners had already created a highly accurate barometer and realized that by applying weather forecasting principles to their barometer readings, they could also create a weather forecasting instrument. The Forecaster was created in 1915 as a portable forecaster that required minimal instrumentation, such as a simple barometer and an observation of wind direction, and was simple to calculate with. It was made as a small disc calculator out of overlaid ivorine discs, an early plastic. Despite its ease of use, it achieved 90% accuracy for 12-hour forecasts. The original Zambretti algorithm has since been implemented in a number of electronic forecasters.

The Zambretti Forecaster is a weather forecasting tool that was introduced in 1920 in the form of a circular slide rule. It claims to predict near-term weather accurately based on barometric pressure, pressure trend (rising, steady, or falling), and wind direction. It is based on the basic meteorology of pressure fronts. When you watch a weather forecast on TV, you’ll notice that high- and low-pressure areas are prominently displayed on the map. Wind and precipitation are strongly associated with pressure area boundaries. Furthermore, high pressure is usually associated with sunny weather, whereas low pressure is usually associated with cloudy, rainy, or snowy weather.

The Zambretti Forecaster has a lot of interesting features. First and foremost, there was no Mr. or Ms. Zambretti; rather, it was a trading name used by Negretti and Zambra, a well-known London instrument-making firm from the mid-nineteenth century until 1999. Second, a modern reproduction was available for purchase in the mid-aughts of the twenty-first century, though it does not appear to be currently available.