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Modern Weather Forecasts Are Stunningly Accurate

theatlantic.com

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Re: Modern Weather Forecasts Are Stunningly Accurate

#101

Post by saalweachter »

brootstrap wrote: post #81

Just a little knowledge to drop, as a bachelor degree meteorologist and also coder / HN'er. Dont use your built in phone app for forecasts. Dont expect hour by hour precision (maybe for the next few hours sure, but not 2,3,4,5 days out). Trust nobody expect the trained professionals at NWS. These people look at ALL the models, they watch things like a hawk. I work with some of these nerds and it's crazy. They are lik…

In the Hudson Valley, we have (a) local weather nerd(s): https://hudsonvalleyweather.com .

It's especially nice for upcoming storms because they break down the region logically based on the relevant features (the river valleys and mountains), for instance: https://hudsonvalleyweather.com/wp-content/uploads/2019/01/1...

Re: Modern Weather Forecasts Are Stunningly Accurate

#102

Post by jdietrich »

brootstrap wrote: post #81

Just a little knowledge to drop, as a bachelor degree meteorologist and also coder / HN'er. Dont use your built in phone app for forecasts. Dont expect hour by hour precision (maybe for the next few hours sure, but not 2,3,4,5 days out). Trust nobody expect the trained professionals at NWS. These people look at ALL the models, they watch things like a hawk. I work with some of these nerds and it's crazy. They are lik…

If you really care about short-term weather forecasts, learn to read surface pressure charts and rainfall radar. It's not particularly difficult and it gives you a huge amount of additional information.

A summary forecast can only tell you so much, especially in changeable conditions and complex microclimates. Knowing the range of probable conditions is often much more useful than knowing the most probable condition.

Re: Modern Weather Forecasts Are Stunningly Accurate

#103

Post by starpilot »

chewz wrote: post #10

Just follow few models for a couple of weeks and you will notice how inaccurate the weather forecast is.* I do follow ECMWF and ICON and a bit of OpenWeather forecast and the differences in forecasted temperatures are often 2-3 degrees C. And everything with a horizon over 72 hours is just numerology. (OpenWeather showed -19C in early days of Feb just 2 days ago, today it is -2C). Now a model is just a model (I had s…

Windy's NEMS model is awesome for complex alpine terrain.

Re: Modern Weather Forecasts Are Stunningly Accurate

#104

Post by scott_s »

voyager2 wrote: post #60
maaaats wrote: post #40

Earlier quoted context omitted.

> it gets the 12 hour forecast right about 40% of the time Where are these figures from? Your emotions, or something scientifically rigid? If the former, having this discussion is meaningless.

"chance of precipitation is 80%, less than an inch possible" How would you determine, in a scientifically rigid manner, the limits on conditions which would validate that forecast as "right?" Or the inverse. What conditions would invalidate it as "not right?"

In a top-level comment upthread, jacques_chester posted a link to an overview of forecast verification methods: http://www.cawcr.gov.au/projects/verification/

Re: Modern Weather Forecasts Are Stunningly Accurate

#105

Post by subraizada3 »

brootstrap wrote: post #81

Just a little knowledge to drop, as a bachelor degree meteorologist and also coder / HN'er. Dont use your built in phone app for forecasts. Dont expect hour by hour precision (maybe for the next few hours sure, but not 2,3,4,5 days out). Trust nobody expect the trained professionals at NWS. These people look at ALL the models, they watch things like a hawk. I work with some of these nerds and it's crazy. They are lik…

I made a website that displays hourly weather forecasts from the NWS: https://www.subraizada.com/weather/kbmg

You can make a version for your location here: https://bitbucket.org/subraizada3/weather-generator/src - it should just generate a single HTML file which you can host anywhere.

An older version also showed the 'normal' weather.gov forecast embedded to the left of the hourly forecast, you can get that if you copy/paste the deleted part of this commit back into the python file: https://bitbucket.org/subraizada3/weather-generator/commits/...

Re: Modern Weather Forecasts Are Stunningly Accurate

#106

Post by saltcured »

kevin_thibedeau wrote: post #98
jacques_chester wrote: post #46

Many folks, when hearing forecasts have improved, will disagree. They can think of many times when the forecast was wrong, perhaps hilariously or disruptively so. This is textbook availability bias. You overestimate the failure rate because the failures were memorable, especially the major failures. But the far more frequent accurate predictions are not recalled, because they don't leave as much of an emotional impre…

If you live near where the jetstream boundary usually lies, forecasts are generally less accurate because small, less predictable shifts can have a large impact on daily weather.

Yes! As a west coast native and sometime visitor to the midwest, I'd say that is true for the whole western US at least. If you learn to read the forecasts and maps you can actually start to grok it and intuit the mechanics.

You can start to imagine the jet stream whipping like a hose and understanding that the exact rate of its swing might vary, causing weather fronts to sweep across the plains a little earlier or a little later, or steering the atmospheric river a little north or south as it sprays the coast. This is the mechanism behind those sudden wild changes in Chicago, when you switch between northern to southern weather in a single day.

And in the short-term data, you can watch a radar animation and get pretty good at predicting when a rain wall or big thunder cell is going to cross your location, and what to expect on a quick errand.

The only thing you cannot reason your way through is when the maps indicate large areas of instability and you really just have to set your mental threat condition and wait to see whether something erupts over your head or not. Afternoon thunderstorms in the mountains or coasts often have this uncertainty to them.

Re: Modern Weather Forecasts Are Stunningly Accurate

#107

Post by brootstrap »

travisjungroth wrote: post #89
brootstrap wrote: post #81

Just a little knowledge to drop, as a bachelor degree meteorologist and also coder / HN'er. Dont use your built in phone app for forecasts. Dont expect hour by hour precision (maybe for the next few hours sure, but not 2,3,4,5 days out). Trust nobody expect the trained professionals at NWS. These people look at ALL the models, they watch things like a hawk. I work with some of these nerds and it's crazy. They are lik…

Don't all those apps just get their data ultimately from the NWS?

Yes this is truth to some degree. However, you dont know what you are getting with an app. If you go to read the official NWS page, the forecasts are human curated by a pro. Apps likely are just taking model output directly and feeding it to you as gospel.

Re: Modern Weather Forecasts Are Stunningly Accurate

#108

Post by brootstrap »

wenc wrote: post #90
pxlpshr wrote: post #86

Earlier quoted context omitted.

I find Dark Sky to be the best forecasting tool for weather within the hour. It's almost always ahead of all the other apps in terms of the latest forecast.

I bought the app because of its hyperlocal forecasting, but it's been known to predict precipitation where there's none, and vice versa. I wonder if it does better in some geographies than others (e.g. high pressure system areas where things are more stable)

hyperlocal is a joke, sorry to say it. Just because you can downscale your grid to a very small number doesnt mean good data. It just means you can do statistics and mathy stuff to interpolate. Everyone forecasts better in stable times such as a strong high pressure ridge. The tricky part is the edge areas between air masses, the transition zones. This is where all the juicy weather actually happens and it is the hardest to model

Re: Modern Weather Forecasts Are Stunningly Accurate

#109

Post by gruez »

I skimmed this article and the linked sciencemag article and they seem to talk about wide scale weather events (eg. hurricanes), rather than the typical things that people look for in forecasts (yes/no rain, min/max temperature). A freakonomics article from 2008 found that at least for precipitation forecasts, weather forecasts don't fare much better than a simple probabilistic model. Has forecasts like these improved in accuracy?

Re: Modern Weather Forecasts Are Stunningly Accurate

#110

Post by labster »

brootstrap wrote: post #78
jacques_chester wrote: post #46

Many folks, when hearing forecasts have improved, will disagree. They can think of many times when the forecast was wrong, perhaps hilariously or disruptively so. This is textbook availability bias. You overestimate the failure rate because the failures were memorable, especially the major failures. But the far more frequent accurate predictions are not recalled, because they don't leave as much of an emotional impre…

Validating the wx is extremely hard. For instance, if you make a forecast, what do you use as the 'truth'? A weather station? Trust me, I've worked with plenty of station data, and it is trash. So now you are comparing a weather forecast against some suspect trash validation set. Nobody knows! The fact is, predictions will keep getting gradually better, more high res. But the fact our atmosphere & earth system is ins…

Hi fellow meterologist hacker. I too have a B.S. in atm sci and enough years in grad school that I'm still paying for it lol.

Yeah, the extent to which models are verified against their own data is pretty interesting -- even the reanalysis data only represents a best guess of a place with physics similar to Earth. It includes a lot of advected observations, thousands of miles from the original observation site, but still useful because at least you know something about the air over the oceans.

Even if we really do get a good handle on cloud physics, ultimately there are limits on how much we can model. Parameterizations have to happen, because of limits to computer time -- a 24h forecast completed in 26h is worthless. I'm honestly surprised that they've been pushing to get models to third order and higher approximations, because the errors in your initial conditions are larger, but apparently every little bit helps.

But forecasts are pretty good considering that weather modeling is a initial value problem where we only know the initial conditions at a few observation points of varying quality, a boundary value problem where the boundaries can have complex interactions with the internal state, and simulation run time really matters.

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