The details of which days are going to be sunny a month out, which will be rainy, and when storms will arrive is chaotic and impossible even in theory to predict in detail more than a few weeks away. Practice is worse, there we manage no more than a few days, and this has been true for several decades.
That said, there are larger trends that can be predicted. For instance the seasons which come from astronomical facts. Or the several year El Niño/La Niña oscillation. Not to mention relatively slow moving Rossby waves in the jet stream. (One of which is bringing hot weather to Russia and monsoons to Pakistan right now.) These give useful information about what is likely to happen and keep happening over periods of weeks, months, and to some extent years.
But none of this brings us any closer to the idea of being able to give an exact weather forecast for a day 6 months in the future. That goal is impossible. And has been known to be impossible for several decades. Furthermore I assure you that this fact is well-known to every competent modern meteorologist. (The word "competent" does not necessarily cover people chosen primarily for their appearance to deliver the weather report for local TV stations.)
the forecast skill for ECMWF and NOAA have been improving pretty steadily over the last 15 years. Basically, we're seeing two days farther into the future now than 20 years ago.
I agree that chaotic dynamics and various noise sources limit the time horizon for weather predictions to perhaps 2 weeks.
I know what 'chaotic' means. Or where the seasons come from. The statement I was taking issue with is still complete nonsense. We can predict the weather, both in theory and in practice. He was saying that we can't and this is obviously untrue.
That said, there are larger trends that can be predicted. For instance the seasons which come from astronomical facts. Or the several year El Niño/La Niña oscillation. Not to mention relatively slow moving Rossby waves in the jet stream. (One of which is bringing hot weather to Russia and monsoons to Pakistan right now.) These give useful information about what is likely to happen and keep happening over periods of weeks, months, and to some extent years.
But none of this brings us any closer to the idea of being able to give an exact weather forecast for a day 6 months in the future. That goal is impossible. And has been known to be impossible for several decades. Furthermore I assure you that this fact is well-known to every competent modern meteorologist. (The word "competent" does not necessarily cover people chosen primarily for their appearance to deliver the weather report for local TV stations.)