Why are the weather predictions often wrong?

[dirty.deeds]

I now live 14 miles from the metrological centre for the u.k ...and whenever they predict the weather it's usually wrong...There was the classic in the 1990's in the u.k where a well respected weatherman(michael fish) said there was not going to be a hurricane and then half the country got trashed ...laugh ,i would have if i hadn't been picking my roof up from the field next door...anyway,why do metrologists seem to be so inept at predicting weather?

[C1ay]

My forecast is never wrong. Every day there is a 50% chance that it will rain......eiher it will or it won't.

[Tormod]

Originally Posted by dirty.deeds

why do metrologists seem to be so inept at predicting weather?

Because it is an extremely difficult task. The Earth's weather system is a chaotic system and it is impossible to predict how it will be even 10 minutes from now with absolute certainty. A day or two you can get decent predictions, but the long term forecasts are basically just their best guesses after intepreting scientific data from weather stations and satellites.

[dirty.deeds]

That's a fair comment but...and a big but here...take today for instance,it's raining here and they come on the tv and tell me it's sunny!!!!! there 14 miles away,why don't they just look out of the window for the local weather and then ring around a few mates to see what it's doing elsewhere in the country for the national forecast?

By the way useless fact here but ,the tribe of toffs made a hit record about John Kettley one of the bbc weathermen,bet you've never had that in your country... a song about a weatherman in the top 10....the u.k is a bit surreal at times... lol...

[Tormod]

Originally Posted by dirty.deeds

That's a fair comment but...and a big but here...take today for instance,it's raining here and they come on the tv and tell me it's sunny!!!!!

Didn't you say you live in England? "Sunny" means "light showers". Need any other translations while we're at it?

[dirty.deeds]

we have two types of rain here..the stuff that falls vertically and the other type that is driven horizontally by the wind...we can experience both types on a typical sunny day...

As the brochure for devon says.....come to sunny devon where it rains 6 days out of 7 ,and on the 7th day it p**ses down....LOL...........

The metrology centre has some of the most powerful computers there with data covering a hundred years or so,so why can't they reliably forecast the next days weather? there are a lot of variables that can change the weather but with the unreliability of the forecasts of late ,the looking out the window form of weather reporting would be better than what is currently available..

[Eclogite]

There are two reasons why weather forecasts are inaccurate (this increases to three in the UK).
1. As Tormod pointed out the weather is a chaotic system. Tiny differences in inputs can generate massive differences in outputs. [I believe it has been established that this chaotic behaviour is not consistent. Some of the time the weather behaves in a more linear manner, with the changes thereby being quite predictable, then it reverts to chaotic mode and long term predictability vanishes.]
2. There are often significant differences in the precise weather experienced as we move even as little as half a mile. The weather forecasters are giving a prediction that is aimed at hundreds or thousands of square miles. It has been my experience that you can amend the general forecast to one appropriate to your area with a little practice. Thus, when I hear a forecast for sleet, I know I am going to get snow at my home and rain at my work, and sleet on the drive between them, even though both are separated by only nineteen miles.
3. (For the UK only ) It is a government conspiracy to ensure the principal topic of conversation amongst people in the UK remains the weather, thus inhibiting discussion of failings of the government.

[dirty.deeds]

Originally Posted by Eclogite

3. (For the UK only ) It is a government conspiracy to ensure the principal topic of conversation amongst people in the UK remains the weather, thus inhibiting discussion of failings of the government.

We have a government ?...I thought the country was being controlled by TV weathermen.. ....your right though,good point well made..

[Tormod]

Originally Posted by dirty.deeds

We have a government ?...I thought the country was being controlled by TV weathermen.. ....your right though,good point well made..

Didn't you know? Your government is slightly west of London (a place called Washington D.C.).

[Eclogite]

Originally Posted by Tormod

Didn't you know? Your government is slightly west of London (a place called Washington D.C.).

I think you are getting it confused with Crawford, Texas. Aren't we drifting off topic?
dirty.deeds, at least the weather persons are generally more attractive than the politicians, and when they tell untruths they do so unknowingly.