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M81 by Ian Humphreys, WMA member

Will we have clear skies?                                        by Gordon Dennis

21/3/2020

1 Comment

 
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:
  • north of the British isles - we will experience fine and clear weather:
Picture
  • south of the British isles, - we will experience unsettled weather
Picture
  • overhead, this generally gives rise to occlusions, which are marked with low cloud and rain.
Picture
These are not infallible rules, but do give a strong indication to help plan your observations. 
1 Comment
Hugh Allen
21/3/2020 04:37:50 pm

Nice start Gordon. Now please can you arrange the fine weather :-)

Reply



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