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People seem to have different opinions on how good forecasts are. I think it likely depends on which model your forecast source of choice pulls from. I notice

People seem to have different opinions on how good forecasts are. I think it likely depends on which model your forecast source of choice pulls from. I notice that the weather on my Apple Watch corresponds exactly to what GFS says. GFS is OK for medium range, but I don't find it too useful for shorter range. NAM is better for a day or two out. HRRR is better for a few hours out. Rather than letting some aggregator simplify the weather for you, you can just look at the raw data yourself: https://weather.cod.edu/forecast/ https://weather.cod.edu/forecast/ For big events, the media briefings by the National Weather Service are good resources. But they often stop the briefings early; a few weeks ago we had a high probability of a large amount of snowfall. The updates stopped at like 9AM, the snow was forecast to start around 1PM. Watching the short term models showed that the probability for snow was decreasing (NYC was just below the snow/rain line), and indeed we got pretty much no snow. (It snowed, but it didn't accumulate and the change to rain happened early.) To be fair, the briefing from the weather service said that the changeover time between snow and rain was very uncertain and that it would be the difference between a little rain and major snow event. But my point is, you can always go get yourself some more data; the closer you get to the event, the more accurate the forecast is. (I don't know if any of you watch Skip Talbot, but he was looking at helicity swaths on the HRRR a few hours out, found a big one, and where HRRR predicted the strong rotation in the storm is pretty much exactly the path of a major tornado. HRRR is never going to be perfect, but it is right a lot.)

rootusrootus 3y ago
That's an interesting point about the Apple weather forecast. That correlates pretty well with my experience. It is exceptionally inaccurate at short range forecasts. It's kind of a running joke at this point.
- herpdyderp 3y ago
  The most humorous part to me is when it says it's currently raining or snowing and it's clear and sunny. How can a system be so wrong that it can't tell the current state of the weather?
  - bumby 3y ago
    From the article: >”These observations are then fed into numerical prediction models to forecast the weather.” In other words, the forecasts come from models, not necessarily real-time station readings. Those readings are inputs into the model, and the models may not get updated fast enough to reflect current conditions.
    - Fomite 3y ago
      Or it might be raining at the station the reading is being made at, but not where you are. Living in the west for example, a lot of weather stations are remarkably broad in the area they're expected to represent.
      - bumby 3y ago
        The point is that the forecasts are often not built from real-time weather station data, but models using various initial conditions.
  - ako 3y ago
    Forecast are usually for a larger area, 5x5 kilometers, or 10x10 kilometers. Even within this area, weather will not be the same everywhere, so they'll give a probability for the entire area. Windy.com lets you compare different models for a specific location, it also includes the size of the area per model: https://www.windy.com/?49.339,5.054,5 https://www.windy.com/?49.339,5.054,5 GFS is area is 22km, ECMWF 9km, ICON-D2 2.2Km, Arome 1.3Km, and UKV is 2Km. Even in a 1.3x1.3Km area it may not rain everywhere at the same time. And then there's also the time element, so it's 1.3Kmx1.3Kmx1Hrs (or 3Hrs). So lot's of variation possible.
    - amarcheschi 3y ago
      Yup, a few days ago I made a python script to help me choose whether to get to uni by bike or by moped when it rains (given two coordinates I calculate the angle(bearing?) and checks whether it rains, and the angle from which the wind blows to see if I'll get all wet in the face) and I had a bit of a hard time figuring out why two different providers, windy and openweathermap, gave me 2 different wind results. Eventually, I found out they were using a different model, it took a bit of time tho, because windy only has increments of hours, while the other one was more granular
- wiredfool 3y ago
  Apple weather quite often has the "expected radar" function show storms taking a 90 degree turn right around now, so you'll see rain coming from the west, and suddenly when it gets to predictions, it's traveling north. (Note, this is Ireland). Dark sky was a lot better. I've also noticed that Met.ie will typically predict more rain, and they're usually right. (e.g., last weekend was basically rain/drizzle/wind the whole time, met.ie nailed it, apple weather said that there would be an hour on Sat and all Sunday morning would be wet. Of course, predicting rain in Ireland is not difficult.
- blaufuchs 3y ago
  This one really kills me during Fogust in the Bay Area. I wake up and see the sun is gonna break through at ~1pm, oh no actually 2pm, oh no actually 3pm... oh no it's just another completely overcast day. I can understand missing a day or two, but it's bizarre when it happens day after day for weeks on end. You'd think the priors would get updated at some point.
- nirav72 3y ago
  I'm really surprised, considering that they bought darksky. When darksky was active, it was one of most accurate weather apps I had ever used for location specific rain forecast.
SiempreViernes 3y ago
Also useful to keep in mind is that predictions can become more accurate without necessarily improving in precision.
unsignedint 3y ago
I primarily rely on Windy for weather forecasts, which I find exceptionally useful due to its ability to compare multiple models. The variety of overlays available makes it an indispensable tool for all my weather-related needs. [0]: https://windy.com https://windy.com
- uoaei 3y ago
  Same here! Not to be confused with windy.app!
  - WillPostForFood 3y ago
    That is confusing! Does windy.com have an app?
    - unsignedint 3y ago
      Yes! https://play.google.com/store/apps/details?id=com.windyty.android https://play.google.com/store/apps/details?id=com.windyty.an... https://apps.apple.com/us/app/windy-com-weather-radar/id1161387262 https://apps.apple.com/us/app/windy-com-weather-radar/id1161...
- bamboozled 3y ago
  Windy uses some of the models mentioned including GFS, you can select the model you want to use. So I’m not sure it would be any more accurate than the Apple Watch.
  - unsignedint 3y ago
    If you're simply seeking basic weather information, then what you receive from your Apple Watch won't differ much. However, if you prefer to analyze and interpret the raw data yourself, Windy stands out as an excellent resource. It aggregates numerous data sources, offering a comprehensive platform for informed decision-making regarding the weather.
LeoPanthera 3y ago
Ultra-short-range weather on Apple devices uses what used to be called "Dark Sky", before Apple bought it. It's how you get those alerts that say things like "Light rain in 17 minutes".
- swores 3y ago
  Dark Sky was just the name of a weather app that included that feature earlier than Apple's weather app. But things like "rain in X mins" is a feature multiple providers & apps have (including Apple once they bought Dark Sky), it's not specifically what Dark Sky was nor is it exclusive to them/Apple. (And actually, Dark Sky was probably the best weather app all round, yet Apple despite buying them and using some of their tech still produce one of the worst weather apps in my experience.)
  - tomaskafka 3y ago
    Hi, if you miss the Dark Sky, I am running a privacy-conscious indie weather app that can be configured to look just like the Dark Sky app: https://weathergraph.app https://weathergraph.app It's subscription based though.
willmadden 3y ago
Where you live matters more. If you live near a mountain range, good luck getting accurate weather predictions.
ryandrake 3y ago
Our local TV station weatherman has a YouTube channel[1] where he geeks out every morning about the weather, providing a much more detailed forecast than he has time for during the brief windows he has on the TV news. Walks through the HRRR, NAM, GFS, satellite pictures, and other sources of information. It's a nice compromise if you find the raw data to be overwhelming. 1: https://www.youtube.com/@markfinanweather https://www.youtube.com/@markfinanweather
- jayknight 3y ago
  There's no substitute for a local meteorologist who knows how weather patterns work in your region and knows how to interpret the models and is good at communicating that to regular people.
  - genghisjahn 3y ago
    Agreed. For Philly I go to this guy. https://theweatherguy.net/blog/ https://theweatherguy.net/blog/
    - jayknight 3y ago
      And for Memphis: http://www.memphisweather.net/ http://www.memphisweather.net/
- dylan604 3y ago
  Absolutely. It is something that I find amusing about people moving from California, LA/SoCal in particular, where their weather is basically just a nice segue from celebrity talk into more celebrity talk that reads some report the producers pulled. Then, they move to town and are amazed at how much people actually pay attention to the weather and comment on how many people actively have open tabs with the live radar. I usually reply with when you need to know if your ride to Oz is coming or not, you pay a lot closer attention.
  - ghaff 3y ago
    With snow in particular, 20 miles can be the difference between sort of a nothingburger and you really don't want to leave the house if you don't need to.
ramraj07 3y ago
Relate to this much? https://xkcd.com/1324/ https://xkcd.com/1324/
AtlasBarfed 3y ago
It depends if you're over the age of probably about... 35 Three day forecast in the 80s and probably early 90s are about where, crap, 15 days out is, actually the 15day is probably better. Modern forecasting long term identifies the front movements, really well long term, even if they might be off a day and 5degrees. The old forecasts would be completely off. Source 50something
- dylan604 3y ago
  Wow, you're being generous. To me, Nostradamus could have predicted the 10-day forecast as accurately as some that I've seen from the 80s/90s. It's June in Texas, so we'll just say the 10-day is going to be sunny, hot, no rain. It's California in June, so we'll just say warm with June gloom burning off in the afternoon; warmer to hot inland. I didn't use any science data, and my forecast will probably have just as good of a chance as one that did. Nothing like the old Aggie weather station consisting of a chain suspending a rock. If rock is wet, it's raining. If rock is moving, it's windy.
monkburger 3y ago
The NAM overestimates southern jetstream energy. And the 3km is just awful for anything beyond 24hr. HRRR is OK, but usually <10 hours for better numbers. You should relllllly look at the soundings, though.
dan-robertson 3y ago
Mostly unrelated: are there any good weather apps that get and can visualise an ensemble forecast?
IG_Semmelweiss 3y ago
I find that more important than the model used, is that you get actionable intel. To me, actionable intel boils down to 2 P's . Precision, and Probability. So, I don't care if tomorrow there's a 50% chance of rain. I care that at a precise time of the day , say 9am, has a 10% precipitation and at noon is 90% , because i commute at 9am, not at noon. Wind is also an important factor if its raining. Temp as well. I need all this info presented as a mosaic. For this purpose, I find the NOAA forecast local by hour is unrivaled. https://www.weather.gov/okx/ https://www.weather.gov/okx/ . Enter ZIP and then in enter local forecast by hour. I have this URL bookmarked in my browser. I haven't looked back since. Example: https://forecast.weather.gov/MapClick.php?lat=33.797&lon=-118.062&unit=0&lg=english&FcstType=graphical https://forecast.weather.gov/MapClick.php?lat=33.797&lon=-11... I'd love to know if there is an android app that gives this level of detail, preferably, without spying into my microphone...
- Sn0wCoder 3y ago
  I second weather dot gov mapclick. This makes me want to finally fix my PWA that used the Dark Sky API that quit working in 2023. This PWA also had a feature to click an icon and feed the long/lat into the mapclick URL which is the feature I used most often. I had a bookmark for a free replacement API for Dark Sky (that I got from HN) but have since re-formatted my computer. I know slightly off topic, but does anyone have a recommendation for a good free (couple users a day) weather API? Any suggestions would be appreciated as this has given me the motivation to hook it back up. Cheers.
  - Sn0wCoder 3y ago
    I guess since I am linking to weather dot gov will just give their API a try. If anyone has suggestions, I am open since there are so many…. https://www.weather.gov/documentation/services-web-api https://www.weather.gov/documentation/services-web-api
- vel0city 3y ago
  I use the myRadar app on Android. It has a per hour graph of temperature and precipitation that makes it easy to quickly understand the next few hours. The paid version also gives easy access to more radar types like velocity
dylan604 3y ago
> I think it likely depends...my Apple Watch corresponds exactly to what GFS says. GFS is OK for medium range which is interesting, as i'm noticing the "within 15 minutes" level of notice on rain starting/stopping to have been close enough. the daily forecast last week said no rain even though the conditions really looked like it could at any moment. my iDevices pinged with rain starting soon even though the same apps forecast still did not suggest rain. it started raining with in "good enough" range of the app's notifications. the update to the native weather app have all been very good over the past 2 OS updates. maybe they have integrated whatever company they purchased for good, but for my local area on the globe, it has been pretty good. i haven't traveled in a good while, so maybe my market is in the sweet spot of getting a lot of attention??? BigD in case you're wondering
- perfectritone 3y ago
  Apple acquired DarkSky and sunsetted their API in the past few years. It always seemed more accurate to me than any other weather service. Sad to see it go.
  - dylan604 3y ago
    to me it didn't go, it just got rolled into Weather.app. I never used the original app, so I have not direct comparsion. however, if they are using the darksky data/tech/etc into weather.app, then it's better for me. not really sure where/how/why the new app updates are better under the hood, but they just are which makes it all seem like worthy upgrades
everdrive 3y ago
I use weather.gov the same way. If you look at the hourly forecast for your area, you get very verbose, useful, and accurate information. My mother in law always reports the weather, and it's always wrong because she's "asked google" or has seen it on TV. The un-aggregated information is excellent and almost always more accurate than what is reported from other sources.
y-c-o-m-b 3y ago
GFS = Great Faulty System as I like to call it. For 10-day regional weather, ECMWF is king. The problem will always be resolution though. For example here in the Pacific Northwest, the ECMWF can't distinguish our dynamic terrain very well (surface level vs 500-1000ft hilltops for example). This website allows you to select which weather model you want to use: https://www.pivotalweather.com/model.php?fh=loop&dpdt=&mc=&r=conus&p=sfct-imp&m=ecmwf_full https://www.pivotalweather.com/model.php?fh=loop&dpdt=&mc=&r...

rootusrootus 3y ago

That's an interesting point about the Apple weather forecast. That correlates pretty well with my experience. It is exceptionally inaccurate at short range forecasts. It's kind of a running joke at this point.

herpdyderp 3y ago
The most humorous part to me is when it says it's currently raining or snowing and it's clear and sunny. How can a system be so wrong that it can't tell the current state of the weather?
- bumby 3y ago
  From the article: >”These observations are then fed into numerical prediction models to forecast the weather.” In other words, the forecasts come from models, not necessarily real-time station readings. Those readings are inputs into the model, and the models may not get updated fast enough to reflect current conditions.
  - Fomite 3y ago
    Or it might be raining at the station the reading is being made at, but not where you are. Living in the west for example, a lot of weather stations are remarkably broad in the area they're expected to represent.
    - bumby 3y ago
      The point is that the forecasts are often not built from real-time weather station data, but models using various initial conditions.
- ako 3y ago
  Forecast are usually for a larger area, 5x5 kilometers, or 10x10 kilometers. Even within this area, weather will not be the same everywhere, so they'll give a probability for the entire area. Windy.com lets you compare different models for a specific location, it also includes the size of the area per model: https://www.windy.com/?49.339,5.054,5 https://www.windy.com/?49.339,5.054,5 GFS is area is 22km, ECMWF 9km, ICON-D2 2.2Km, Arome 1.3Km, and UKV is 2Km. Even in a 1.3x1.3Km area it may not rain everywhere at the same time. And then there's also the time element, so it's 1.3Kmx1.3Kmx1Hrs (or 3Hrs). So lot's of variation possible.
  - amarcheschi 3y ago
    Yup, a few days ago I made a python script to help me choose whether to get to uni by bike or by moped when it rains (given two coordinates I calculate the angle(bearing?) and checks whether it rains, and the angle from which the wind blows to see if I'll get all wet in the face) and I had a bit of a hard time figuring out why two different providers, windy and openweathermap, gave me 2 different wind results. Eventually, I found out they were using a different model, it took a bit of time tho, because windy only has increments of hours, while the other one was more granular
wiredfool 3y ago
Apple weather quite often has the "expected radar" function show storms taking a 90 degree turn right around now, so you'll see rain coming from the west, and suddenly when it gets to predictions, it's traveling north. (Note, this is Ireland). Dark sky was a lot better. I've also noticed that Met.ie will typically predict more rain, and they're usually right. (e.g., last weekend was basically rain/drizzle/wind the whole time, met.ie nailed it, apple weather said that there would be an hour on Sat and all Sunday morning would be wet. Of course, predicting rain in Ireland is not difficult.
blaufuchs 3y ago
This one really kills me during Fogust in the Bay Area. I wake up and see the sun is gonna break through at ~1pm, oh no actually 2pm, oh no actually 3pm... oh no it's just another completely overcast day. I can understand missing a day or two, but it's bizarre when it happens day after day for weeks on end. You'd think the priors would get updated at some point.
nirav72 3y ago
I'm really surprised, considering that they bought darksky. When darksky was active, it was one of most accurate weather apps I had ever used for location specific rain forecast.

SiempreViernes 3y ago

Also useful to keep in mind is that predictions can become more accurate without necessarily improving in precision.

unsignedint 3y ago

I primarily rely on Windy for weather forecasts, which I find exceptionally useful due to its ability to compare multiple models. The variety of overlays available makes it an indispensable tool for all my weather-related needs. [0]: https://windy.com https://windy.com

uoaei 3y ago
Same here! Not to be confused with windy.app!
- WillPostForFood 3y ago
  That is confusing! Does windy.com have an app?
  - unsignedint 3y ago
    Yes! https://play.google.com/store/apps/details?id=com.windyty.android https://play.google.com/store/apps/details?id=com.windyty.an... https://apps.apple.com/us/app/windy-com-weather-radar/id1161387262 https://apps.apple.com/us/app/windy-com-weather-radar/id1161...
bamboozled 3y ago
Windy uses some of the models mentioned including GFS, you can select the model you want to use. So I’m not sure it would be any more accurate than the Apple Watch.
- unsignedint 3y ago
  If you're simply seeking basic weather information, then what you receive from your Apple Watch won't differ much. However, if you prefer to analyze and interpret the raw data yourself, Windy stands out as an excellent resource. It aggregates numerous data sources, offering a comprehensive platform for informed decision-making regarding the weather.

LeoPanthera 3y ago

Ultra-short-range weather on Apple devices uses what used to be called "Dark Sky", before Apple bought it. It's how you get those alerts that say things like "Light rain in 17 minutes".

swores 3y ago
Dark Sky was just the name of a weather app that included that feature earlier than Apple's weather app. But things like "rain in X mins" is a feature multiple providers & apps have (including Apple once they bought Dark Sky), it's not specifically what Dark Sky was nor is it exclusive to them/Apple. (And actually, Dark Sky was probably the best weather app all round, yet Apple despite buying them and using some of their tech still produce one of the worst weather apps in my experience.)
- tomaskafka 3y ago
  Hi, if you miss the Dark Sky, I am running a privacy-conscious indie weather app that can be configured to look just like the Dark Sky app: https://weathergraph.app https://weathergraph.app It's subscription based though.

willmadden 3y ago

Where you live matters more. If you live near a mountain range, good luck getting accurate weather predictions.

ryandrake 3y ago

Our local TV station weatherman has a YouTube channel[1] where he geeks out every morning about the weather, providing a much more detailed forecast than he has time for during the brief windows he has on the TV news. Walks through the HRRR, NAM, GFS, satellite pictures, and other sources of information. It's a nice compromise if you find the raw data to be overwhelming. 1: https://www.youtube.com/@markfinanweather https://www.youtube.com/@markfinanweather

jayknight 3y ago
There's no substitute for a local meteorologist who knows how weather patterns work in your region and knows how to interpret the models and is good at communicating that to regular people.
- genghisjahn 3y ago
  Agreed. For Philly I go to this guy. https://theweatherguy.net/blog/ https://theweatherguy.net/blog/
  - jayknight 3y ago
    And for Memphis: http://www.memphisweather.net/ http://www.memphisweather.net/
dylan604 3y ago
Absolutely. It is something that I find amusing about people moving from California, LA/SoCal in particular, where their weather is basically just a nice segue from celebrity talk into more celebrity talk that reads some report the producers pulled. Then, they move to town and are amazed at how much people actually pay attention to the weather and comment on how many people actively have open tabs with the live radar. I usually reply with when you need to know if your ride to Oz is coming or not, you pay a lot closer attention.
- ghaff 3y ago
  With snow in particular, 20 miles can be the difference between sort of a nothingburger and you really don't want to leave the house if you don't need to.

ramraj07 3y ago

Relate to this much? https://xkcd.com/1324/ https://xkcd.com/1324/

AtlasBarfed 3y ago

It depends if you're over the age of probably about... 35 Three day forecast in the 80s and probably early 90s are about where, crap, 15 days out is, actually the 15day is probably better. Modern forecasting long term identifies the front movements, really well long term, even if they might be off a day and 5degrees. The old forecasts would be completely off. Source 50something

dylan604 3y ago
Wow, you're being generous. To me, Nostradamus could have predicted the 10-day forecast as accurately as some that I've seen from the 80s/90s. It's June in Texas, so we'll just say the 10-day is going to be sunny, hot, no rain. It's California in June, so we'll just say warm with June gloom burning off in the afternoon; warmer to hot inland. I didn't use any science data, and my forecast will probably have just as good of a chance as one that did. Nothing like the old Aggie weather station consisting of a chain suspending a rock. If rock is wet, it's raining. If rock is moving, it's windy.

monkburger 3y ago

The NAM overestimates southern jetstream energy. And the 3km is just awful for anything beyond 24hr. HRRR is OK, but usually <10 hours for better numbers. You should relllllly look at the soundings, though.

dan-robertson 3y ago

Mostly unrelated: are there any good weather apps that get and can visualise an ensemble forecast?

IG_Semmelweiss 3y ago

I find that more important than the model used, is that you get actionable intel. To me, actionable intel boils down to 2 P's . Precision, and Probability. So, I don't care if tomorrow there's a 50% chance of rain. I care that at a precise time of the day , say 9am, has a 10% precipitation and at noon is 90% , because i commute at 9am, not at noon. Wind is also an important factor if its raining. Temp as well. I need all this info presented as a mosaic. For this purpose, I find the NOAA forecast local by hour is unrivaled. https://www.weather.gov/okx/ https://www.weather.gov/okx/ . Enter ZIP and then in enter local forecast by hour. I have this URL bookmarked in my browser. I haven't looked back since. Example: https://forecast.weather.gov/MapClick.php?lat=33.797&lon=-118.062&unit=0&lg=english&FcstType=graphical https://forecast.weather.gov/MapClick.php?lat=33.797&lon=-11... I'd love to know if there is an android app that gives this level of detail, preferably, without spying into my microphone...

Sn0wCoder 3y ago
I second weather dot gov mapclick. This makes me want to finally fix my PWA that used the Dark Sky API that quit working in 2023. This PWA also had a feature to click an icon and feed the long/lat into the mapclick URL which is the feature I used most often. I had a bookmark for a free replacement API for Dark Sky (that I got from HN) but have since re-formatted my computer. I know slightly off topic, but does anyone have a recommendation for a good free (couple users a day) weather API? Any suggestions would be appreciated as this has given me the motivation to hook it back up. Cheers.
- Sn0wCoder 3y ago
  I guess since I am linking to weather dot gov will just give their API a try. If anyone has suggestions, I am open since there are so many…. https://www.weather.gov/documentation/services-web-api https://www.weather.gov/documentation/services-web-api
vel0city 3y ago
I use the myRadar app on Android. It has a per hour graph of temperature and precipitation that makes it easy to quickly understand the next few hours. The paid version also gives easy access to more radar types like velocity

dylan604 3y ago

> I think it likely depends...my Apple Watch corresponds exactly to what GFS says. GFS is OK for medium range which is interesting, as i'm noticing the "within 15 minutes" level of notice on rain starting/stopping to have been close enough. the daily forecast last week said no rain even though the conditions really looked like it could at any moment. my iDevices pinged with rain starting soon even though the same apps forecast still did not suggest rain. it started raining with in "good enough" range of the app's notifications. the update to the native weather app have all been very good over the past 2 OS updates. maybe they have integrated whatever company they purchased for good, but for my local area on the globe, it has been pretty good. i haven't traveled in a good while, so maybe my market is in the sweet spot of getting a lot of attention??? BigD in case you're wondering

perfectritone 3y ago
Apple acquired DarkSky and sunsetted their API in the past few years. It always seemed more accurate to me than any other weather service. Sad to see it go.
- dylan604 3y ago
  to me it didn't go, it just got rolled into Weather.app. I never used the original app, so I have not direct comparsion. however, if they are using the darksky data/tech/etc into weather.app, then it's better for me. not really sure where/how/why the new app updates are better under the hood, but they just are which makes it all seem like worthy upgrades

everdrive 3y ago

I use weather.gov the same way. If you look at the hourly forecast for your area, you get very verbose, useful, and accurate information. My mother in law always reports the weather, and it's always wrong because she's "asked google" or has seen it on TV. The un-aggregated information is excellent and almost always more accurate than what is reported from other sources.

y-c-o-m-b 3y ago

GFS = Great Faulty System as I like to call it. For 10-day regional weather, ECMWF is king. The problem will always be resolution though. For example here in the Pacific Northwest, the ECMWF can't distinguish our dynamic terrain very well (surface level vs 500-1000ft hilltops for example). This website allows you to select which weather model you want to use: https://www.pivotalweather.com/model.php?fh=loop&dpdt=&mc=&r=conus&p=sfct-imp&m=ecmwf_full https://www.pivotalweather.com/model.php?fh=loop&dpdt=&mc=&r...