Monday, January 02, 2006

well above normal

so over the past little while we've been experiencing above-normal temperatures here in winnipeg. today we're looking for a high of -4. the normal high for this time of year is -13. that's pretty good.

so what's causing this?

primarily it's a zonal flow across western canada. that means that the air aloft is moving from west to east, rather than from north to south (or south to north). this allows for pacific ocean-modified air to flood across the rockies, but more importantly it impedes cold air from moving southward. so while it's been cloudy recently (boy, has it been cloudy! i haven't seen the sun since i got back from the west coast on the 28th!) it's been relatively warm. and that's the trade-off we get here.

now, what's the root cause of this warm-up? i can't say for certain. the fact that the sea surface temperatures over the pacific are pretty much near normal, thereby not deflecting the jet stream more meridionally, seems as good an explanation to me as any.

on a completely different topic, there's a moderate risk of severe thunderstorms across some of the southern and southeastern u.s. it's only january 2, and yet things are cooking. okay, not exactly cooking--this potential outbreak seems more about the tremendous shear than it seems about instability. the storms produced in these situations are not often classical, difficult to identify on radar, and usually move so quickly that people get very little warning that something is coming.

dangerous situation, for sure.


At 4:26 PM, Anonymous The Manitoba Storm Spotter said...

So how come its been so cloudy this long? Its actually been cloudy everyday since at least
almost a week before christmas! When have we ever had this many cloudy days in a row?

I'm green with envy with all the storms in the south. I wish we got storms like that in january but then I guess there would be no snow and me and my snowmobile would not like that very much! I like snow anyways...

At 9:02 PM, Blogger Weather Central said...

well from the soundings i've looked at, it seems that the cloud is being generated by an inversion, which inhibits deep vertical motion and traps moisture underneath. as well, it eventually has to get cold at some altitude, so when it does, the cold air aloft and warmer air beneath it mix, giving you extensive cloud.

as for when we've had this many cloudy days in a row, i don't know. it does seem excessive, however.

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