The BBC's weather service produced this map, indicating that the centre is expected to transit just to the north of the Scottish mainland.

It seems that Storm Dave is being channelled towards the UK by a powerful jet stream, the flow of high level winds in the atmosphere were weather systems develop and are guided them around the globe.
In this case, what is now Storm Dave has been supercharged by the huge temperature contrasts across North America during recent days.

www.bbc.co.uk/weather/articles/ce3d7n10ypyo

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