I'm not sure why the same forecasts seem to show the entire Arctic warming to above freezing while a low moves in?
This low looks like it might stay a little while, which I would expect to cool things down enough to change this season from a very early start to at least an average start for the melt ponding for much of the central basin.
On this blogsite it seems to be a common meme that High pressure= warm, Low pressure =cold. Somebody like to provide evidence for this? IMHO this is by no means true all of the time - I suspect it is close to 50-50 for being correct or incorrect. The main factors deciding the temperature being the history, size and position of the highs and lows.
As an example, for a high pressure (i.e. almost calm conditions at sea-ice level) with clear skies and fixed in location above the ice-pack please explain the mechanism by which the air temperature at 2m is relatively "warm"
;-) Michael frequently seems to have a bit of an incomplete understanding that is a) not representative for the crowd here, and b) seems a bit politically coloured to me.
I think much of that misunderstanding derives from a misunderstanding of the maps. While high pressure has sinking quite warm air at the 850 hPa maps, low pressure systems sweep up the relatively cool boundary layer air by Ekman transport. So, they must have a cool core over the arctic, which has, however, not a lot of meaning for the 2m level due to the different lapse rate. Yet, people see a cold spot on their map...
By the way, as we are at that, I have a bit of a trouble to understand something: We know that hurricanes do Ekman pump, i.e. a cyclonic vortex would give rise to spreading/upwelling. Now, what I do not understand fully is: When a low pressure system is sitting over the arctic, the wind vectors should actually point inwards and the ice at the surface should be compressed?
Underneath there could be quite a bit of upwelling, in particular, since the ice will be forced in the idealized picture into near circular motion pushing out the water beneath it. Any mistake in this? What dominates here?