Large-scale weather forecasts are made using sophisticated computer programs that model a virtual world. The precision of the output of such a model depends on the quality of the input.
One of the usual sources of input is an airplane, which feeds back wind data in real time.
The coronavirus pandemic has greatly reduced the number of aircraft in operation. As a result, the incoming information has been reduced and the predicted winds at the height of the cruise can no longer be verified and the feedback cycle in the global model is much weaker.
According to the European Center for Medium-Range Weather Forecasts (ECMWF), "aircraft reports are second only to satellite data in their impact on forecasts. Between March 3 and 23, there was a 65 percent reduction in the reports received. Globally, the reduction was about 42 percent. "
There is a measurable reduction in the accuracy of the forecast winds, at the cruising altitude of the aircraft, if all reports from the aircraft are removed. There is a minor, but still statistically significant, impact on near-surface fields, up to 3 percent on surface pressure.
Other types of observations are likely to be less affected by the disruption than aircraft reports, and there may be some additional radiosonde (balloon) launches to try to mitigate the lack of aircraft data.
Satellite data provides a lot of information about temperature and humidity fields, but less about wind fields.
A major tornado season is approaching in the US. USA And in June the hurricane and typhoon season begins. While the effect, if any, on the forecast of these significant weather events has yet to be seen, hurricane force winds and typhoons are driven by the upper and middle atmospheres, so the inaccuracy in these forecasts may be significant.