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Why did satellite observations make five-to-seven-day forecasts possible?

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Weather forecasting Doppler radars, such as this one operated by the U.S. National Weather Service at New Underwood, South Dakota, extract the Doppler frequency shift of the echo produced by a moving target by noting how much the frequency of the received signal differs from the frequency of the signal that was transmitted.

Satellite observations were essential to making five-to-seven-day, or medium-range, forecasts possible because they provided global, real-time data that were previously unavailable. Before the advent of meteorological satellites, it was impossible to obtain consistent, routine observations over vast, data-sparse regions such as the ocean waters of the Southern Hemisphere.1

These satellites allow for the collection of quantitative data on temperature, cloud patterns, and moisture distributions across the entire globe. This information is critical for numerical weather prediction (NWP) models, which require accurate initial conditions to calculate future atmospheric changes. By providing these comprehensive inputs, satellites enabled the development of global forecasting models—such as those used by the ECMWF—which became the standard in the 1980s and turned medium-range forecasting into a reality.123