The truth behind the accuracy of weather forecasts
23 comments
·May 16, 2025gerdesj
Weather forecasts are based on models and extrapolation based on a lot of factors. I'm not too certain but I think that the smallest weather model cell size is about two miles squared or perhaps cubed - I don't know how the models work.
Weather forecast distribution is by "news". News is deployed at mostly fixed intervals.
Anecdote: In Yeovil, Somerset, UK. The topography here (its quite hilly here in a county with some fairly famous "levels") means that it can be pissing down with rain on one side of the town and be dry on the other side and so on.
Weather forecasting is a quite hard problem. The really hard problem is delivering it.
bmink
Weather forecast is best told as a narrative and reducing it to a sports score like temperature / rainfall will always be problematic for many regions.
I’m in SF and I have not looked at a “TV/app style” forecast in years. Instead every morning I read:
https://forecast.weather.gov/product.php?format=CI&glossary=...
During the day I look periodically at:
vrosas
Enjoy NOAA’s data while they still have funding.
mplanchard
I also like the pure NWS data, and will take a moment to shill Deep Weather on iOS, which provides a nice, easy interface to the NWS products for an area.
ttobbaybbob
or if you want nicely wrapped pure NWS data you can get results like https://trytako.com/card/EK32MAxL85E5_KOZy6R3/?dark_mode=tru... via our API
fred_is_fred
I've been looking for something like this but unfortunately I am halfway between two stations and with the mountains here makes enough of a difference that neither one is accurate.
FiatLuxDave
Does anyone know of any weather sites which show the actual outcomes? It is very easy to find forecasts. It is quite difficult to find what the weather actually was on a given day at a location, but at least it is possible. I have never seen a site that shows the predicted weather for a day alongside the actual weather for that day. I presume professional meteorologists know where to look for this data, but for the rest of us, it feels like it is hidden.
I know no one wants to advertise their mistakes, but showing a history of your accuracy which was transparently updated would build more credibility with the public than anything else. Perhaps someone is scraping this info and posting it?
nerdralph
Environment Canada has hourly historical data for many stations. Some may be daily. https://climate.weather.gc.ca/historical_data/search_histori...
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WalterBright
I've often better at predicting "will it rain" by looking out the window.
braiamp
Which makes sense depending on what the reach of the forecast is on geographical scales. In my country, you have 6-7 meteorological zones that needs predictions, but the forecasters would always say "area so-so will have rains", because those meteorological zones don't fit neatly into our administrative distributions. That also means that if a administrative area is split between two zones, is a 50-50 whenever or not the prediction will turn out to be accurate.
ggm
Dangerous to claim rain forecasts approach perfection. It may be statistically true, but it's highly politicised in Australia, it has strong ties to forward financial outcome in the farm sector which is primed to be suspicious of government and see the BoM as "the enemy" for a clutch of bizarre conspiracy theory reasons.
If you make this claim, be prepared for the hate storm when it gets it wrong for some marginalised community.
Also, the lack of warning processes in flood contexts means the BoM can claim it gets the rain forecast right, but the downstream flood alerts which lie in the hands of 3 tiers of government still break down. Who gets the blame? EVERYONE including the BoM.
I love the BoM. But, I worry about them too. They could be defunded for political gain.
Also: their app is crap and for bizarre reasons they still offer their weather radar in the best, most simplest, 1990s internet form over http:// urls because of the overhang of farm equipment which can't handle TLS https: connections. There is a good https: service but they modernised the UX. I would prefer the 1990s style, but delivered over secure transport. (browsers now routinely preference https: urls so you wind up with an interstitial delay. minor nit only)
If you use windy, or willyweather, it's federating BoM data with other sources.
danpalmer
I'm not Australian, and moved here a year ago, but the obsession with the BoM is... odd? As an outsider, I see a website that's a mess from the early 2000s, and weather forecasts that just aren't very good (neither accurate nor detailed?).
An event I was recently supposed to go to was called off because the BoM forecast rain all day 3 days out. Google Weather said it would be dry and sunny. It was dry and sunny. It's an anecdote not data, but so far I'm not understanding the national obsession based on this and a few other personal experiences.
layoric
Obsession is a bit much, but one of the few genuinely "for the public good" institutions remaining. Others we have seen get hollowed out or replaced. A lot of hard work has and does go into providing the services that the BoM does. We are a big country with a small population, and they have been around for over 100 years which is a long time considering our federation was around the same time.
I, and many other Australian's, like public institutions without a profit motive. Gutting these institutions usually ends up with worse privately operated ones.
ggm
Looking at what is happening to NOAA it's a right wing reaction to climate science: because climate and weather are sister topics, they go after the agency on one political agenda, (climate) and the other side of the coin (weather) suffers. And, most of the opposition from communities like farming comes from the strong suspicion of being "told what to do" about climate and land management.
It's a horrendous impedence mismatch. I did debate not directly putting right-wing into this, but my personal experience of speaking to people in the farming sector who are sharing hate on the BoM is that it's driven in right wing political agenda about "big government" and "world government" and "my tax dollars"
iamthemonster
I'm also a blow-in but I've been in Australia 14 years. "The BoM" is a fascinating Australian cultural artefact and even in weather-obsessed Britain (where Michael Fish was a household name in a similar category to Hitler and Stalin) there was nothing similar.
I think the parent comment goes some way to explaining something I find bizarre - the "extreme weather warnings" from the BoM, which they issue for every light breeze. I even have a fabric gazebo erected in my back yard, held down only by sandbags at the corners, and I don't have to disassemble it for every BoM "extreme weather warning" for wind/storms.
There are so many "extreme weather warnings" for wind that they'd be meaningless for everyone who's not in a small boat.
jamesfinlayson
I remember talking with someone who worked in Antarctica and he said there was a wall somewhere in the station that displayed weather forecasts from a bunch of government run weather services from a bunch of different countries - Australia's was apparently frequently different to what everyone else was saying (they had some long-running nick-name for it which I no longer recall).
jiggawatts
> I love the BoM.
You have no reason to. They're not a well-run, efficient organisation, even by government department standards.
> over http:// urls because of the overhang of farm equipment which can't handle TLS https: connections.
This is the public narrative, and is a brazen lie.
THERE IS NO SUCH FARMING EQUIPMENT!
Certainly not in 2025.
Their site DOES HAVE a certificate, and supports HTTPS, right now.
They just refuse to let you use it, redirecting a successful HTTPS connection back to HTTP.
If there was farming equipment (Which models? Vendors? Affecting how many farmers?) out there they would be broken right now because port 443 is open and listening. If they can connect to port 443, then they don't need to be redirected back to port 80 because they worked. If they can only connect to port 80, then the presence of port 443 makes no difference.
I keep pointing this out, and "true blue aussies that looooove the BoM" keep arguing about this. The BoM spends hundreds of millions on IT, tens of millions on consultancies like Accenture, but they can't manage a $50 certificate and a bog standard HTTP/HTTPS endpoint.
My iPhone, right now, can't connect to most BoM web pages because of this stupid, stupid issue! There is no mystical broken farming equipment, but there definitely are inconvenienced users like me!
After putting up this rant for years and years in various forums, a former BoM employee finally fessed up -- they were the one that tried switching HTTP to HTTPS years ago and "broke" their internal systems. Not non-existent farming equipment, it was BoM's own internal services that fell over.
Why?
Because they hadn't updated any of it in decades, and the software was so old that it couldn't handle "modern" cipher suites and TLS versions. Modern being "newer than SSL 3.0"... in 2015.
That's not the sign of a competently run organisation worthy of admiration.
RachelF
Farmers have a reason to be sceptical:
The BoM caused hundreds of millions of $ of damage to livestock farming - they warned about a huge drought in 2022 causing massive livestock culling. Instead there were years of above-average rainfall.
ggm
The BoM cop this both ways. People don't look to the candlestick error bars on their statements, and their long range weather forecast is outside the window of the ABC article we're discussing. I get how upsetting it is to de-stock but if their best belief is the risk is high, what else are they meant to do? If they hadn't said this, and there'd been the drought, they would have got your scorn too, right?
If you know a climate/weather bureau of comparable scale of footprint doing a better job, we'd all like to know. AFAIK there isn't one: most of the alternates work in different scale, with different climate forcing functions.
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I aggregate weather forecasts for the Event Horizon Telescope Collaboration, which is the collaboration behind those black hole images you might have seen.
We want to pick the best nights during an observing window based on the weather in 12 locations around the world. These are mostly locations on the peaks of mountains, where it's hard to do a good forecast because the ground is rugged on length scales that are smaller than the grid in the numerical computation.
Forecast accuracy has improved in recent years, but I'm really looking forward to AI forecasts. They appear to fix some systematic errors that are still present in traditional forecast simulations.