The dramatic decline in aircraft observations. Source: ECMWF

Computers are great, but as the famous saying goes "Garbage in, Garbage out".

And in the case of Weather Forecasting, it's "Bad Observations In, Bad Forecasts Out".

Forecasts are created from observations of the "current" conditions all around the world, and of course, locally to your location. These can be via various means: Ships sailing in the ocean, Planes flying in the sky, Satellite images of the ocean surface, Land Based automatic observation stations ...and of course many manual efforts such as weather balloons released into the atmosphere, and manual observations of cloud, rain and temperature.

Perhaps you've already put two and two together, and realised that there are significantly less planes and ships as the world shuts down to prevent the spread of the novel coronavirus.

The WMO (World Meteorological Organization) is concerned about the impact of the COVID pandemic regards the declining quantity of weather of weather observations.

Inflight measuring of temperature, and wind speed/direction are important information for both weather forecasting, and climate monitoring.

The Aircraft Meteorological Data Relay programme (AMDAR) is a system supported by commerical aircraft to transmit weather observations to ground stations via satellite or radio links. Europe, in particular, has seen the a dramatic decrease in the number of measures.

The 'good old days' of more and more observations Source: ECMWF

World Wide Coverage of Observations from Aircraft. Source: ECMWF