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Autumn forecast

PostPosted: 2012 Sep 10, 16:33
by Len Wood
With the current record min in Arctic sea ice cover

it is tempting to think one could make a prediction for total rain this autumn.
I have done a correlation between minimum Arctic sea ice cover and EWP summer and
autumn rainfall over the last 10 years. Rather a short period I agree but nonetheless:
There is no significant correlation in autumn, but there is in summer.
99% significant using students t-test!

The trouble is the climate system is not that simple.
Ordinary and slope convection are going on. Evaporation over the northern open water is more to do with wind speed as the autumn progresses rather than SST.
The climate system is decidedly non-linear. Tropical disturbances (ex hurricanes) may enhance mid latitude depressions.

So no forecast.

Re: Autumn forecast

PostPosted: 2012 Sep 14, 19:22
by Nick Gardner
Len Wood wrote:So no forecast.

Well Len.

I am not a meteorologist by profession (I'm an environmental scientist), but that isn't going to stop me doing a hopecast as opposed to a forecast.

Autumn/winter Hopecast (No statistics here, just fingers crossed): warm, not too wet, lots of sunshine and no frosts (no scraping of windscreens etc), and defintely none of that nasty white stuff (we had enough of that in Dec 2010 to last a lifetime).

There, done it. Then again, a winter like last year wouldn't go amiss: mild, not too wet, quite sunny, only a small handful of slight frosts and no snow (and an early start to spring).

Re: Autumn forecast

PostPosted: 2012 Sep 14, 20:21
by greg_gruner
I don't know if you have seen this:

The Met Office have a new model that predicts surface winds based on stratospheric winds. To predict a season in advance is too much (and they don't give any winter forecast!) but it helps give more notice of cold spells (or so they think!)

It will be interesting to see what the jet stream does after its southward meander this summer.

Re: Autumn forecast

PostPosted: 2012 Sep 17, 22:42
by Len Wood
I am not sure how far ahead these new forecasts are meant to be good for.
I see they involve probabilities that are more confident the nearer the time of the cold snap.

As I see it, they probably cannnot do better than a week in advance.
This being the time it takes for a stratospheric warming to evolve and set itself up.