Sunday, January 27, 2013

"They can't even predict the weather 5 days in advance..."

I ran into this ancient meme again and would like to share some observations.  
The Meme goes like this:

“Meanwhile the Met Office in the UK never seems to be able to predict more than 5 days in advance.”

Doesn't that sound like a cliche more than any serious assertion?

I admit I don’t know about UK weather forecasting. And I’ll admit locally, (Southwest USA), the Weather Service does seem to forecast more snow and rain storms than we actually see, but they do have their "%ChanceOf" and other factors.

On the other hand, it seems that forecasts of Hurricane Sandy's path - and potential - got nailed pretty good a week before US landfall… and it seems to me tropical cyclone forecasting in general is pretty spot on.  So what about that?

I think it's another one of those human perception things.

It's like when every freak’n stoplight turns red on “me” when I’m in a hurry.  But, an actual log shows that statistically they didn’t – but being stopped when I’m in a rush sky-rockets my awareness of and annoyance with having to stop and wait.

I wonder, does anyone track and systematically quantify “forecast accuracy” for the Met Office or US Weather Service?  

I don't know, but if anyone out there does, please share the link.
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A bigger Logical Fallacy in this meme is that 
it ignores the range/standard of expectations being applied.

Weather has an unavoidable element of randomness and a cone of accuracy does exist.  

If you are confused why this should be so, it would be good to become familiar with the global heat distribution engine that is our climate.  
Watch some of those time lapse videos of cloud patterns or even better the 2nd video is an excellent recent NASA graphic review of our "Global Heat Distribution Engine" from space and within the oceans - the best presentation to date: Earth From Space (HD).

Global circulation

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notice how the movement of swirls never mirrors one another - yet, though it's complex, it's not chaotic as the swirls follow specific patterns and bands.  Notice that the range (bands) within which these flows occur are quite stable.  

Climate is like those broad bands and weather is like those individual swirls.

There really is a difference between them, but, 
let's not forget they are aspects of the same system.
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Another Logical Fallacy in this meme is that 
We expect weather-forecasters to know the weather in a particular place; at a particular time; to exacting details.

When the weather-forecaster says it will rain Tuesday and it doesn’t, we say they are wrong.  Even if the rain comes a few days later or earlier.

The point is that weather-forecasters are judged by an exacting and not altogether fair metric.

I’ll bet if we asked them to forecast a month’s temperature range and precipitation range for a particular location - that their accuracy range would be most impressive.

It’s like denialist wanting to see all the impacts of Anthropogenic Global Warming immediately when everyone who knows anything about our planet's geophysical processes appreciates that they operate at their own grand leisurely pace.

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