Clouds marching past

The cold air outbreak that I wrote about a few days ago will hit the UK tomorrow (Sunday), with subzero temperatures as far south as London. Here’s a picture of the cold air on its way southwards, taken from Bergen today:

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The tall clouds are “mild” Cumulonimbus clouds forming as the moist, warm air over the sea surface rises in the cold air from the Arctic. I remember seeing such clouds, albeit more vigorous ones, during the IPY-THORPEX polar low field campaign in Andøya in northern Norway in March 2008.

Polar low brewing outside northern Norway

I just got an alert from the excellent BarentsWatch site about a polar low off the coast of northern Norway. Here’s the latest satellite image (downloaded from yr.no):

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You can clearly see the dual system between Iceland and Norway, and what’s nice about this is that we also see the edge of the cold air outbreak stretching west from the polar lows. Here are some satellite-based wind speeds from about 1600 GMT yesterday, taken from this site:

WMBas78_noaa

This shows nicely how strong the winds are along the edge of the outbreak.

Update: I just found winds from this morning, too, and here wind speeds of more than 50 knots (Force 10 on the Beaufort wind force scale) were estimated by the satellite:

WMBds78_noaa

That’s pretty hefty. We can trace the development back to the disturbance seen in this picture from Wednesday, a few hours before the wind snapshot above:

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It’s moving slowly, but seems to have built some strength since yesterday.