How do the weather people know what the wheather's going to be like a week in advance?

Question

Im going camping thurs-sun and the wheather says its gonna rain all those days... i hope they're wrong but how do they know? it even had an option where you could see the forecast for the whole month! I just don't understand how they could know... the wheather is unpredictable.

Answer 1

Weather is quite predictable to an extent.  They key is tracking water vapor, if you can do that, you know where it's going to be, and you can calculate what its effects are likely to be.

Doppler radar can detect water vapor.

Answer 2

Meteorologists study weather patterns.  It's predictable but not an exact science, which is why they say a "20% chance of rain".  Certain weather phenomena behave certain predictable ways.

Answer 3

Well, they use computer model forecasts, and try to predict the timing of front, low pressure systems, etc, basically anything that could cause rain, and then try to predict.  They are usually fairly accurate to about 3-5 days.  Then, more than 5 days out, with the timing and speed of fronts and storm systems, it gets very difficult to throw out a forecast.  But you can still never be sure even 12 hours out.  

For example, where I live, they had a 10% chance of rain (90% chance of no rain) out at the noon forecast yesterday from all the weather reports I listened to.  But then from 9pm-midnight, we got 4.75 in of rain.  

Bottom line is you never know, but you usually get some kind of idea.

BTW-when a 20% chance is given, that means that with similar weather conditions, you can expect rain 2 times out of 10.

Answer 4

I'm totally with you! I'm having the same dilemma  about camping this weekend! 20 to 30% chance isn't for sure! But sometimes they are right!

Answer 5

Because the weather travels around the world from west to east.  That is why they show radar.