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GraphCast: AI model for weather forecasting
291–300 of 310 posts
Re: GraphCast: AI model for weather forecasting
#292I find this quite surprising actually. You'd think predicting the weather is mostly a matter of fast computation. The physical rules are well understood, so to get a better estimate use a finer mesh in your finite element computation and use a smaller time scale in estimating your differential equations. Neural networks are notoriously bad at exact approximation. I mean you can never beat a calculator when the issue…
Shortcuts 100% exist. Imagine another physical problem. Simulating a sand grain and how it bounces off other sand grains or lodges against them. If you wanted to simulate a sand mountain, you could use a massive amount of compute and predict the location and behaviour of every single grain. Or, you could take a bunch of well-known shortcuts and just know that sand sits in a heap at the angle-of-repose. That angle dec…
You get the same result in a short span of time, heck you may even get a reliable error bound.
Where this falls apart is that error accumulates over time and not just for one heap of sand but for many such heaps of sand that also interact with other heaps of sand.
Predicting weather for the next hour is trivial. Aviation runs on the fact that you can forecast fairly accurately into the next hour most of the time.
The difficulty scales superlinearly over time due to the error accumulation over predictions
Re: GraphCast: AI model for weather forecasting
#293Earlier quoted context omitted.
Humm... are you referring to Google Flu? [1] That was a very different beast. It relied on using Google searches to infer the prevalence of various Influenza Like Illnesses in real time, while the CDC reports data with a 2-week lag. Notably, some of the queries they found to be correlated were... strange... like NBA results. Not unsurprisingly (in hindsight, at least) [2], this eventually broke down when epidemics an…
> Notably, some of the queries they found to be correlated were... strange... like NBA results. Doesn't seem that strange to me. The presence of a professional sports team in your area is correlated with an increase in flu rates. Getting an ice hockey (NHL) is pretty much the worst. https://www.upi.com/Health_News/2023/08/08/flu-deaths-sports...
That's definitely one factor, but from what I recall (it's been a while) the connection was slightly more subtle. The NBA season (Oct-Apr) overlaps the flu season (Dec-Feb) so if people are googling NBA results you're in either in or close to the typical flu season. If the NBA decided to change their schedule, the correlation would go away.
Re: GraphCast: AI model for weather forecasting
#294I've been really impressed at how much better weather forecasting has become already. I remember weather forecasts feeling like a total crapshoot as recently as 15 years ago or so.
If you live in an area with a lot of microclimates within one city, weather forecasting is honestly no better than astrology.
Re: GraphCast: AI model for weather forecasting
#295Earlier quoted context omitted.
Shortcuts 100% exist. Imagine another physical problem. Simulating a sand grain and how it bounces off other sand grains or lodges against them. If you wanted to simulate a sand mountain, you could use a massive amount of compute and predict the location and behaviour of every single grain. Or, you could take a bunch of well-known shortcuts and just know that sand sits in a heap at the angle-of-repose. That angle dec…
The point was that weather, unlike a sandheap, is a chaotic hydrodynamic system with turbulent flows, that means it's computationally intractable to do exactly, which is why weather forecasts are only good for a few days anyway. The example you gave does not really explain anything.
The sandheap is chaotic too - just one sand grain tumbling can be enough to start a landslip. But the end result tends not to depend on the minute details - if sand grain A didn't cause the landslip, then a few seconds later sand grain B would have.
Re: GraphCast: AI model for weather forecasting
#296I've been really impressed at how much better weather forecasting has become already. I remember weather forecasts feeling like a total crapshoot as recently as 15 years ago or so.
It still is. I farm outside of my day job and trying to schedule time to do things like cut hay is sort of a crapshoot. Hay needs a 3-4 day window to dry, rake and roll. This year I got rained on at least twice on days where the NWS showed clear and sunny for 3 days on the spot forecast. 20% or 50% chance of rain is almost useless knowledge. We went for weeks with a 20% chance and it never rained. We still got everyt…
Yup, I had the same issue. Showed 4 days of clear 80-90 degree weather. Twice in that timeframe it rained (!1 inch each time), ruined the cut.
Re: GraphCast: AI model for weather forecasting
#297Earlier quoted context omitted.
> Apple moved from using The Weather Channel to their own forecasting a year ago [1]. AFAIK they don't have their own forecasting models, they use same data sources as everyone else: https://support.apple.com/en-us/HT211777
Your linked article says they use their own, if you're on a version later than iOS 15.2.
No it does not. Read the secion "Data sources", they list all the usual regional providers.
Re: GraphCast: AI model for weather forecasting
#298I've been really impressed at how much better weather forecasting has become already. I remember weather forecasts feeling like a total crapshoot as recently as 15 years ago or so.
It still is. I farm outside of my day job and trying to schedule time to do things like cut hay is sort of a crapshoot. Hay needs a 3-4 day window to dry, rake and roll. This year I got rained on at least twice on days where the NWS showed clear and sunny for 3 days on the spot forecast. 20% or 50% chance of rain is almost useless knowledge. We went for weeks with a 20% chance and it never rained. We still got everyt…
If you live in an area with "summer storms" it's basically impossible to forecast anything more than a general area (usually thousands of square miles) that they will appear in.
Its like a shotgun shooting a wall. You can pretty accurately predict the area of the shot, but its incredibly hard to place where exactly each shot in that area will land.
Re: GraphCast: AI model for weather forecasting
#299I find this quite surprising actually. You'd think predicting the weather is mostly a matter of fast computation. The physical rules are well understood, so to get a better estimate use a finer mesh in your finite element computation and use a smaller time scale in estimating your differential equations. Neural networks are notoriously bad at exact approximation. I mean you can never beat a calculator when the issue…
> So apparently the AI found some shortcut for doing the actual computational work. That is also surprising as weather is a chaotic system. Shortcuts should not exist.
Why do you say that shortcuts should not exist? Even very basic statements like "falling pressure and increasing humidity indicate a storm is coming" are generally valid. I've done a little bit of storm-chasing and I'm able to point out areas that are likely to experience severe thunderstorms based on a few values (CAPE, dew point, wind shear, etc). I'm sure forecast meteorologists have even better skills. Are those not shortcuts?
Re: GraphCast: AI model for weather forecasting
#300Earlier quoted context omitted.
It still is. I farm outside of my day job and trying to schedule time to do things like cut hay is sort of a crapshoot. Hay needs a 3-4 day window to dry, rake and roll. This year I got rained on at least twice on days where the NWS showed clear and sunny for 3 days on the spot forecast. 20% or 50% chance of rain is almost useless knowledge. We went for weeks with a 20% chance and it never rained. We still got everyt…
If you live in an area with "summer storms" it's basically impossible to forecast anything more than a general area (usually thousands of square miles) that they will appear in. Its like a shotgun shooting a wall. You can pretty accurately predict the area of the shot, but its incredibly hard to place where exactly each shot in that area will land.
I do live in such an area and we end up just taking the risk a lot of the time. Most of the time it is fine. Sometimes disaster. It is a bit frustrating.