Question

Why are weather forecasts unreliable?

Answer 1

We aren't able to find out what all the air molecules type is and how they interact with each other.

Explanation:

Weather mostly comes from air and how it interacts with other types of air. There's cold air, and there is warm air. Weather happens based on how these two types of air interact. However, our technology isn't accurate enough to predict how all the air molecules will interact and what weather it will create. Weather forecast are mostly educated guesses.

Answer 2

Weather forecasts are numerical simulations of fluid mechanics, heat transfer which are non-linear and can cause large errors beyond 3 days.

Explanation:

The Navier-Stockes equations that govern fluid motion are notoriously sensitive to initial conditions. Errors due to discretization on computer tend to grow, making forecasts rapidly unreliable.