We usually think that modern weather forecasting relies on satellite data and ground-based radar. While that is true to a large extent, commercial airplanes also play a vital role by providing real-time data and observation that is not always easy for other instruments to detect. This, and the failure of remote weather stations as vital repairs may become harder to perform, could have detrimental consequences in the case of extreme weather events.
The instruments on airplanes not only allow immediate observations but data provided by meteorological instruments also enable weather forecasting models to be more accurate.
Typically in North America and Europe, commercial airplanes would blanket wide areas, often overlapping near major cities. As flights are being cancelled due to the coronavirus pandemic, less aircraft in the air means less weather observation data collection by these plane.
This would enable meteorological instruments on flights to act as vital point data in a sampled region. Similar to kriging or other forms of weighted interpolation, data would feed large weather forecast models that would then update a forecasts sometimes to the minute.
Such data can prove vital in cases when fast-moving storms such as tornadoes or micro-bursts develop, as these types of events are difficult to forecast when they occur and where. However, on-board flight instrumentation can help determine the likelihood of extreme events occurring by providing more detailed and location-specific data.
Local temperature and wind data make up the most important components for regional weather forecasts. Macro-models are accurate in determining larger weather patterns but are not sufficiently detailed to provide information on what might happen in a small area.
Typically, flights would continuously send temperature and wind data back, helping to update and improve model forecasting by obtaining new data. The Aircraft Meteorological Data Relay (AMDR) is a system that sends updated aircraft data to models. Usually over 700,000 observations are sent per day, where the data contain wind and temperature readings.
Meteorologists are concerned by the lack of data because April and spring months are typically the most active months of major storms in the northern hemisphere. Satellite systems have improved in recent years where even wind data at some given points can be nearly accurately predicted, which can help mitigate the loss of data.
Models that predict extreme weather events can still be run; however, their accuracy will likely be less and this is the danger meteorologists worry about the most. They might be able to predict, for instance, the occurrence of a thunderstorm, but determining its severity will be difficult in any given location.
There is also another effect that coronavirus will have on weather forecasting. The World Meteorological Organization (WMO) operates a network of ground observation stations that transmit data back to a central system used for forecasting models, similar to AMDR, which this system also uses. However, these stations run in an automated fashion.
Repairs and updates to these stations are periodically needed. In normal circumstances, people would be able to fly to the locations of these stations and perform critical updates and repairs. The lack of flights and, in some places, complete isolation means that some stations may stop working in the coming weeks.
These stations are also affected by the lack of commercial aircraft, as they also depend on flights to transmit data for forecasting models. The stations, similar to commercial flights, are also vital in the data they provide and if they begin to fail then some regions may become difficult to forecast all together. Furthermore, even in remote regions and developing countries, where manual data are collected and transmitted back to provide updated forecasts, are beginning to decline.
This means that extreme weather events in many regions will likely be hard to determine. The potential threat is a major storm or extreme event threatening life could now be missed until it is too late, with our ability to respond to potential disasters diminished.
Weather data collected by commercial aircraft and even ground stations form critical parts in models that forecast extreme weather events. Such models keep us safe in a time of increasing frequencies of extreme weather, due to climate change, that also endangers life.
For now, these models may be less accurate due to the grounding of flights, while remote stations may also begin to cease operation due to a lack of maintenance. Satellite data have improved our weather forecasting in recent years; however, we are still dependent on data collected from local stations and from aircraft.
 For more on how commercial flights typically assist with weather forecasts, see: https://www.newscientist.com/article/2238842-the-coronavirus-pandemic-could-make-weather-forecasts-less-accurate/#ixzz6IDghalh8.
 For more on the effect and loss of commercial flights on forecasting weather, see: https://www.accuweather.com/en/severe-weather/coronavirus-canceled-flights-could-affect-weather-forecasting-at-exactly-the-wrong-time/711234
 For more on weather data from stations that might be lost, see: https://www.climatechangenews.com/2020/04/01/coronavirus-pandemic-threatens-climate-monitoring-wmo-warns/