IF ONLY WE KNEW! As we all do know, forecasting is always difficult, especially of the future. In a maritime climate like ours it’s even harder.
In Earth’s atmosphere, most of what we refer to as ‘weather’ takes place at the lower level where we all live – the troposphere. Above this lies the stratosphere. The boundary between the troposphere and the stratosphere is called the tropopause. The precise height of this region depends on our latitude and the timer of year (i.e. where the Earth is in its orbit).
In the lower stratosphere, there is a very dynamic wind system known as the jet stream which has a strong influence on our weather down in the troposphere. Jet stream winds can regularly reach over 100mph and are a reason why it can take less time to fly west to east over the Atlantic than it takes to fly east-west. In the images below, the red plots show the strongest jet stream winds. You can obtain a jet stream forecast up tom 10 days into the future at https://www.netweather.tv/charts-and-data/jetstream
As a rule of thumb, if the jet stream winds are:
These are not infallible rules, but do give a strong indication to help plan your observations.