The current expert view -perhaps speculation would be a better word - seems to be that the jet is weaker because of a warmer Arctic, hence a lower temp gradient to drive the jet. A strong jet just blasts through and creates mobile weather but a weak one can be stuck in a blocking pattern with nothing to move it on, and hence a period of repetitive weather lasting a month or more, as experienced this year in the UK with rain in March, a warm June and a cool July.
Where that block gets set up can depend on various global factors. This year, recent unusual warmth in NW USA / W Canada seems to have set up a wave train, swinging north there, south over the Great Lakes, north over Greenland, south over Britain. There's a diagram in the link, but it's not dated so it could be just for illustrative purposes. However, a BBC weatherman a couple of weeks ago was showing something similar claiming it represented the current situation. https://www.bbc.co.uk/weather/features/66177220
Last year the position of the loops was reversed, so we got the heat. Now we probably have to wait for the hurricane season to give the jetstream a jolt.
Edited by user
18 July 2023 13:40:52
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