Many of us check multiple forecasts before we bring our scopes out. Clear Sky Chart now shows two forecast models for cloud cover. Click on the top two lines and compare the predicted cloud cover. Scan below the chart for details on how accurate they are.
Check out the Clear Sky Chart for each MAS facility at http://www.mnastro.org/facilities/weather/
Clear Sky Chart
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Wayne
- Posts: 231
- Joined: Fri Sep 21, 2007 2:54 pm
- Real Name: Wayne Boline
- Location: Crystal, MN
Clear Sky Chart
Wayne
Meade ETX-70
Vixen VMC200LDG
Astro-Tech AT72ED
Vixen Porta II mount
Meade LXD55 mount
Meade LXD75 mount
Meade ETX-70
Vixen VMC200LDG
Astro-Tech AT72ED
Vixen Porta II mount
Meade LXD55 mount
Meade LXD75 mount
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Ron Schmit
- Posts: 1299
- Joined: Thu Jun 10, 2004 12:41 pm
Re: Clear Sky Chart
Here are some more details:
The new line is called: ECMWF Cloud
This is not a CMC forecast. It is data from the "European" Forecast Model ECMWF. It provides a cloud cover forecast. It's here for comparison with the CMC cloud cover forecast. The ECMWF model covers a larger area and forecasts further into the future. New data becomes available around 15:00 and 03:00 local time. Which is different than when the CMC forecasts update. This isn't an astronomy-specific forecast. So like many civil forecasts "clear sky" might still mean "some cirrus".
Accuracy Summary: The ECMWF forecast is more accurate than the CMC cloud forecast when predicting mostly clear, but less accurate when predicting mostly cloudy. But ECMWF forecasts out for 72 hours instead of 44 for CMC. The far future ECMWF cloud forecasts are still usable.
Accuracy details: Averaged over North America for the last 30 days: when the forecast is predicting less than 12 hours into the future, mostly-clear forecasts (cloud<25%) have been right 85% of the time. Mostly-cloudy forecasts (cloud>75%) have been right 71% of the time. When the forecast is predicting more than 60 hours into the future, the mostly-clear accuracy is 81% and the mostly-cloudy is to 71%.
Data from the Norwegian Meteorological Institute, also known as MET Norway.
The new line is called: ECMWF Cloud
This is not a CMC forecast. It is data from the "European" Forecast Model ECMWF. It provides a cloud cover forecast. It's here for comparison with the CMC cloud cover forecast. The ECMWF model covers a larger area and forecasts further into the future. New data becomes available around 15:00 and 03:00 local time. Which is different than when the CMC forecasts update. This isn't an astronomy-specific forecast. So like many civil forecasts "clear sky" might still mean "some cirrus".
Accuracy Summary: The ECMWF forecast is more accurate than the CMC cloud forecast when predicting mostly clear, but less accurate when predicting mostly cloudy. But ECMWF forecasts out for 72 hours instead of 44 for CMC. The far future ECMWF cloud forecasts are still usable.
Accuracy details: Averaged over North America for the last 30 days: when the forecast is predicting less than 12 hours into the future, mostly-clear forecasts (cloud<25%) have been right 85% of the time. Mostly-cloudy forecasts (cloud>75%) have been right 71% of the time. When the forecast is predicting more than 60 hours into the future, the mostly-clear accuracy is 81% and the mostly-cloudy is to 71%.
Data from the Norwegian Meteorological Institute, also known as MET Norway.