4 ms·

Same, but in a human context, are mundane atmospheric events so far off today that error bars would have any practical value and/or potentially introduce confus

Same, but in a human context, are mundane atmospheric events so far off today that error bars would have any practical value and/or potentially introduce confusion?

NegativeLatency 3y ago
For this reason I really enjoy reading the text products and area forecast discussion for interesting weather: https://forecast.weather.gov/product.php?site=NWS&issuedby=pqr&product=AFD&format=CI&glossary=1 https://forecast.weather.gov/product.php?site=NWS&issuedby=p...
- doubled112 3y ago
  Anybody happen to know if there's anything more detailed from Environment Canada than their forecast pages? https://weather.gc.ca/city/pages/on-143_metric_e.html https://weather.gc.ca/city/pages/on-143_metric_e.html I really like that discussion type forecast.
yakubin 3y ago
Absolutely. 15 years ago I could reasonably trust forecasts regarding whether it’s going to rain in a given location 2 days in advance. Today I can’t trust forecasts about whether it’s raining currently.
- Smoosh 3y ago
  It seems unlikely that the modelling and forecasting has become worse, so I guess there is some sort of change happening to the climate making it more unstable and less predictable?
  - lispisok 3y ago
    >I guess there is some sort of change happening to the climate making it more unstable and less predictable? I've been seeing this question come up a lot lately. The answer is no, weather forecasting continues to improve. The rate is about 1 day improvement every 10 years so a 5 day forecast today is as good as a 4 day forecast 10 years ago.
- LexGray 3y ago
  I think that is a change in definition. 15 years ago it was only rain if you were sure to get drenched. Now rain means 1mm of water hit the ground in your general vicinity. I blame an abundance of data combined people who refuse to get damp and need an umbrella if there is any chance at all.
  - yakubin 3y ago
    No. I mean getting drenched, when forecast predicted no rain. 1mm isn’t really noticeable by humans.
kqr 3y ago
Sure -- just a few day outs the forecast is not much better than the climatological average -- see e.g. https://charts.ecmwf.int/products/opencharts_meteogram?base_time=202312041200&epsgram=classical_15d_with_climate&lat=59.3326&lon=18.0649&station_name=Stockholm https://charts.ecmwf.int/products/opencharts_meteogram?base_... Up until that point, error bars increase. At least to me, there's a big difference between "1 mm rain guaranteed" and "90 % chance of no rain but 10 % chance of 10 mm rain" but both have the same average.
- jsmith45 3y ago
  The other thing is that many forecasts have a large range. So it might be that the left third of the forecast area has like a 99.9% chance of zero precipitation, the right third has a 99.9% chance of some precipitation, and there is some uncertainly about where the border will be, (and near the border might have less precipitation than the edge). The result is that I will be told ~50% chance of precipitation, but the places I care about might well be in the essentially 0% or essentially 100% parts. The single forecast for a decent size city problem impacts other parts like forecasted highs/low. Even without a front, in some cities that have incorporated much of their suburbs, it is not uncommon for the eastmost part and westmost part to differ by 5-6 degrees, and that is ignoring the inherent temperature differences found in the downtown areas.

Same, but in a human context, are mundane atmospheric events so far off today that error bars would have any practical value and/or potentially introduce confusion?

NegativeLatency 3y ago

For this reason I really enjoy reading the text products and area forecast discussion for interesting weather: https://forecast.weather.gov/product.php?site=NWS&issuedby=pqr&product=AFD&format=CI&glossary=1 https://forecast.weather.gov/product.php?site=NWS&issuedby=p...

doubled112 3y ago
Anybody happen to know if there's anything more detailed from Environment Canada than their forecast pages? https://weather.gc.ca/city/pages/on-143_metric_e.html https://weather.gc.ca/city/pages/on-143_metric_e.html I really like that discussion type forecast.

yakubin 3y ago

Absolutely. 15 years ago I could reasonably trust forecasts regarding whether it’s going to rain in a given location 2 days in advance. Today I can’t trust forecasts about whether it’s raining currently.

Smoosh 3y ago
It seems unlikely that the modelling and forecasting has become worse, so I guess there is some sort of change happening to the climate making it more unstable and less predictable?
- lispisok 3y ago
  >I guess there is some sort of change happening to the climate making it more unstable and less predictable? I've been seeing this question come up a lot lately. The answer is no, weather forecasting continues to improve. The rate is about 1 day improvement every 10 years so a 5 day forecast today is as good as a 4 day forecast 10 years ago.
LexGray 3y ago
I think that is a change in definition. 15 years ago it was only rain if you were sure to get drenched. Now rain means 1mm of water hit the ground in your general vicinity. I blame an abundance of data combined people who refuse to get damp and need an umbrella if there is any chance at all.
- yakubin 3y ago
  No. I mean getting drenched, when forecast predicted no rain. 1mm isn’t really noticeable by humans.

kqr 3y ago

Sure -- just a few day outs the forecast is not much better than the climatological average -- see e.g. https://charts.ecmwf.int/products/opencharts_meteogram?base_time=202312041200&epsgram=classical_15d_with_climate&lat=59.3326&lon=18.0649&station_name=Stockholm https://charts.ecmwf.int/products/opencharts_meteogram?base_... Up until that point, error bars increase. At least to me, there's a big difference between "1 mm rain guaranteed" and "90 % chance of no rain but 10 % chance of 10 mm rain" but both have the same average.

jsmith45 3y ago
The other thing is that many forecasts have a large range. So it might be that the left third of the forecast area has like a 99.9% chance of zero precipitation, the right third has a 99.9% chance of some precipitation, and there is some uncertainly about where the border will be, (and near the border might have less precipitation than the edge). The result is that I will be told ~50% chance of precipitation, but the places I care about might well be in the essentially 0% or essentially 100% parts. The single forecast for a decent size city problem impacts other parts like forecasted highs/low. Even without a front, in some cities that have incorporated much of their suburbs, it is not uncommon for the eastmost part and westmost part to differ by 5-6 degrees, and that is ignoring the inherent temperature differences found in the downtown areas.