Radar, Satellite and Forecast Models Are Not the Same

Radar samples energy returned to the instrument

Weather radar sends pulses and measures energy scattered back by precipitation and other targets. Reflectivity can indicate where hydrometeors are present and how strong the returned signal is; Doppler velocity estimates motion toward or away from the radar. Neither field is a direct photograph of rainfall at the ground. Beam height, distance, blockage, attenuation and non-weather echoes all matter.

A radar timestamp is the observation time of a scan or composite. Animation shows successive observations; it is not automatically a forecast.

Satellites observe radiation from above

Weather satellites measure reflected sunlight and emitted infrared or microwave radiation. Visible imagery reveals cloud texture during daylight. Infrared channels estimate radiative temperature and work day and night, while water-vapor and microwave products expose different atmospheric layers or properties. A bright or cold cloud top is not by itself a measured surface rain total.

Satellites provide broad coverage over oceans and remote regions where surface instruments and radars are sparse. Products may be direct radiance measurements or algorithms derived from several channels, so the product label matters.

Models calculate a possible future atmosphere

Numerical weather prediction starts from an analyzed atmospheric state built from many observations. Equations describing fluid motion, thermodynamics and physical processes are solved on a three-dimensional grid. Output has a model initialization time and one or more valid times. Those are different from the observation time shown on radar or satellite imagery.

Models have finite resolution and approximate processes smaller than their grid. Comparing multiple runs and ensembles helps reveal uncertainty; agreement does not turn guidance into an observation.

Warnings add expert and institutional judgment

An official watch, warning or advisory is not another sensor layer. It is an authority-issued product based on evidence, forecasts, thresholds and local responsibility. PlanetVexa keeps those products labeled as official-only rather than inferring warnings from colorful imagery or model values.