Northwest Europe versus the Pacific Northwest

[Summer8906]

One thing I've noticed (from stats) is what appears to be a significant difference between the NW European climate and the superficially similar climate of the Pacific Northwest, particularly southwestern British Columbia and northwestern Washington State.

Both have oceans to the west and both are subject to relatively mild winters and cool summers, but there seems to be a marked difference in precipitation patterns.

If Vancouver is considered a representative city:

Vancouver - Wikipedia

EN.WIKIPEDIA.ORG

then it appears that Vancouver summers are markedly drier than somewhere equivalent in NW Europe, which would probably be somewhere towards the west of the UK or NW France, such as Bristol, Plymouth or Brest. (These are picked because, like Vancouver, they are close to the ocean, whereas somewhere like London is more remote).

For example, Bristol has 58.7mm precipitation in July, Plymouth 62mm, Brest 71mm, but Vancouver just 36mm (according to Wikipedia).

Vancouver has a very clear dry season, with July and August below 40mm and June-Sep all below 55mm, while the NW European cities above do not. On the other hand Vancouver late autumn / winter periods are extremely wet, with 189mm in November and 168mm in January. These high totals I would expect to be orographically-induced, with 1500m+ mountains rising immediately north of the city. But such orographic enhancement clearly does not occur in summer.

The NW European cities above do not exhibit such a marked seasonal variation.

It appears that, for whatever reason, the Pacific equivalent of the Azores high is very much stronger in summer than our Azores high is, keeping their summers reliably dry (so you could probably count on fine weather in Vancouver in July-Aug) , but wondering why this is?

On the other hand, Vancouver summer mean maxima are not spectacular at 22C in July and August, comparable with inland southern England (though rather higher than coastal cities such as Plymouth).

(I have visited the area once, in July 2004 when it was indeed very dry and pleasant, with some cloudier days in the low 20s and also some sunny days in the high 20s - though I believe this was an unusually good summer in the area).

 

Edited May 6, 2023 by Summer8906