The accuracy of weather forecasts | Hacker News Reader

The accuracy of weather forecasts

abc.net.au

59 pointsBrajeshwar42 comments

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:

https://fog.today

Enjoy NOAA’s data while they still have funding.

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.

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.

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

NWS already has it wrapped nicely just supply your lat/long, and offers the XML version too. Example...

Hourly Weather Forecast Graph (48 hours)

https://forecast.weather.gov/MapClick.php?lat=28.4963&lon=-8...

XML Version

https://forecast.weather.gov/MapClick.php?lat=28.4963&lon=-8...

>I also like the pure NWS data

NWSNOW for Android, includes the vaunted "Forecast Discussion". Side load, No ads, no tracking, pure NWS and NOAA data.

https://www.nwsnow.net/

I made a val to clean this up a little better: https://www.val.town/x/greg_dryke/nwsForecastDiscussionWeb

The `<pre>` on the NWS site was really messy on mobile, this is nice and neat. Feel free to fork it and use your own, or this link should work for your NWS site too!

https://greg_dryke--0816a61c279c11f09d52569c3dd06744.web.val...

(No promises on possible future changes if you do start using it, but it's pretty stable.)

I found reader mode in Firefox Mobile worked fine too, but yours doesn't have the broken line breaks like reader mode did.

Is it possible to navigate to that page from weather.gov (not having a direct link)? Cannot find a way.

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?

Environment Canada has hourly historical data for many stations. Some may be daily. https://climate.weather.gc.ca/historical_data/search_histori...

agree.

Even a site that displays 'just' recent weather specifics (sans how the forecast was) would be quite helpful.

e.g., the hourly precipitation for the last week or month.

Am NOT talking about generalized monthly climate data, fwiw.

Anyone?

University of Iowa has a service to aggregate this sort of thing. It's CSV format, but otherwise seems like what you're looking for?

https://mesonet.agron.iastate.edu/request/download.phtml

Somewhat related: Before launching our new long range (5 day) turbulence forecast tool (for nervous flyers), we spent time experimenting to see how far out we could reliably predict turbulence. Once we had something promising, we started posting daily snapshots—each showing the forecast from five days earlier alongside what actually happened. The model updates continuously, and we’ve kept the process public to demonstrate how well it works, not just claim it does.

https://www.turbulenceforecast.com/drift

This NOAA National Blend of Models (NBM) viewer lets you enable observations and then roll back the forecast initialization date to see forecasts and observations at the same time.

It’s experimental, and selecting weather stations is a little clunky, but it has some really cool info that’s hard to find other places.

https://apps.gsl.noaa.gov/nbmviewer/?col=2&hgt=1&obs=true&fo...

Edit:

This GEFS plume viewer is cool, too.

https://www.emc.ncep.noaa.gov/users/meg/gefs_plumes/index.ht...

You can check a box to plot observations and then pick an older “cycle”.

Both are limited to the US.

I have wondered this for years. Several times I looked for a dataset of historical forecasts. It seems wild that with all the data available out there, there's no go-to source that has past forecasts together with the actual recorded data for each day. That said, these posts do mention some sources:

https://opendata.stackexchange.com/questions/2009/historical...

https://www.reddit.com/r/meteorology/comments/1crs6lu/seekin...

(These aren't "sites" that display the past data, just datasets you can download.)

One challenge is the forecast is constantly updated, as often as several times in a single day. So which forecast would you use for the predicted weather?

On https://weather-sense.leftium.com, you can see the daily forecasts change on a regular basis.

I'm curious if anyone has a good solution for this, how to accurately display cases where a storm might hit either Monday or Tuesday, say 50% chance each. If you just say there's a 50% chance of rain on both days, it looks like there's a significant chance (I guess 25%) that it will rain both days, when the real likelihood of both days raining might be far lower.

That's one reason https://weather-sense.leftium.com shows hourly forecast data:

- The chance of precipitation line tends to gradually go up and then back down over several hours.

- The expected mm of precipitation bars tend to be more actionable: the chance of precipitation may be high, but if the expected amount is low you are not likely to experience much, if any rain; much less need an umbrella.

- Sample screen shot with precipitation in forecast: https://github.com/user-attachments/assets/e003badb-4832-430...

---

https://openweathermap.org even gives minutely rain forecasts for the next hour.

Tangent, but I encourage everyone to actually learn how to predict the weather. Every region has its own peculiarities, and even on a small scale geography may have quite significant impact, so it is natural to focus on where you live. Moreover, you quickly find out that this skill is not about looking at the sky in a single moment and taking a snapshot of it, but rather about recognizing some trends and changes, more prolonged and more subtle as your knowledge grows.

You will find out how urban areas behave differently than rural ones, how plains differ from hills and mountains, how forest differs from meadows, where the small cumulus clouds are being formed and where they disappear, how wind shifts before the storm, how animals change their behavior etc. Some of this stuff can be widely applicable, but some will be specific to your area. And you do not even need to live in some remote areas to enjoy it.

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.

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.

I lived in a place where there is a lot of rain. But the rain can have many faces and especially in summer all weather sites would forecast rain and use a rain symbol for days when the data clearly says there is a high change of minimal rain and a lot of sun otherwise. Which is argueably a good "sunny" day for that area.

My solution was to reduce days to average temperature and sun hours instead of using precip to visualize a full day. And then focus on a "24 hour display" with 24 little icons where the rain instantly seemed a lot less.

Basically focusing on the good things.

There’s lots of different interpretation for what could be meant by the statement of “40% chance of rain tomorrow”.

Linked is that definition explained:

https://www.weather.gov/media/pah/WeatherEducation/pop.pdf

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.

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.

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.

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"

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).

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.

We loved Michael Fish. Nobody in my circuit mistook the Met Office for the NKVD. When he went off air, he had a fan club calling for his return.

He came to talk at our school in the mid-90s and a journalist from the local rag was allowed to sit in the audience for some reason. The journalist asked about 1987 and Michael Fish visibly deflated and looked around the room with a look of "who let the journalist in" before finally inhaling and giving his speech about how technically he said the hurricane wouldn't hit us, he didn't say we wouldn't have a storm.

But you're right, I think it was a sensationalist tabloid talking point to say "Michael Fish missed the hurricane" but he was a well loved weatherman.

I knew a few people in the UK astronomy community, and the Met office was a great place for them. Michael fish's multicolour knitted tank-tops sort of personified the home counties tolerance for minor departure from the norms.

One of my astro chums at Bracknell rode a thumpingly noisy 4 stroke indian with a side-car, smoked hand-rolled menthol cigarettes and appeared to want to become Patrick Moore in size and demeanour. I like to think he fitted in well.

I've stopped asking my Google Assistant if it will rain because it gets it wrong most of the time, at least for my location. I just look at the radar in the BoM app now (agreed that the website is terrible).

> 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.

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.

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.

I've often better at predicting "will it rain" by looking out the window.

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.

I've got an old foot injury that gets sore when rain is coming with surprisingly good accuracy

"Often" is qualitative.

Weather prediction should be quantitative.

TL;DR: That's nice.

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