Clouds Forecast For Astronomical Purposes

Amateur and professional astronomers are always confronted by sky conditions when they observe during the night. In the preparation of your observation session, you can take advantage of the cloud forecastof the Canadian Meteorological Centre GEM Regional model, shown here as cloud forecasts. Interpret these images the same way you would for GOES Infrared satellite pictures found on various web sites.

[ Sat East Can · Sat West Can · Sat East Us · Sat West Us · Info ]

Regional model, satellite simulation, Eastern Canada window

The forecast set is updated between 4:00 and 5:00 UTC. Images for forecast hours...00 h UTC + ...

Animation · 03h · 04h · 05h · 06h · 07h · 08h · 09h · 10h · 11h · 12h · 13h · 14h · 15h · 16h · 17h · 18h · 19h · 20h · 21h · 22h · 23h · 24h · 25h · 26h · 27h · 28h · 29h · 30h · 31h · 32h · 33h · 34h · 35h · 36h · 37h · 38h · 39h · 40h · 41h · 42h · 43h · 44h · 45h · 46h · 47h · 48h

The forecast set is updated between 16:00 and 17:00 UTC. Images for forecast hours...12 h UTC + ...

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Regional model, satellite simulation, Western Canada window

The forecast set is updated between 4:00 and 5:00 UTC. Images for forecast hours...00 h UTC + ...

Animation · 03h · 04h · 05h · 06h · 07h · 08h · 09h · 10h · 11h · 12h · 13h · 14h · 15h · 16h · 17h · 18h · 19h · 20h · 21h · 22h · 23h · 24h · 25h · 26h · 27h · 28h · 29h · 30h · 31h · 32h · 33h · 34h · 35h · 36h · 37h · 38h · 39h · 40h · 41h · 42h · 43h · 44h · 45h · 46h · 47h · 48h

The forecast set is updated between 16:00 and 17:00 UTC. Images for forecast hours...12 h UTC + ...

Animation · 03h · 04h · 05h · 06h · 07h · 08h · 09h · 10h · 11h · 12h · 13h · 14h · 15h · 16h · 17h · 18h · 19h · 20h · 21h · 22h · 23h · 24h · 25h · 26h · 27h · 28h · 29h · 30h · 31h · 32h · 33h · 34h · 35h · 36h · 37h · 38h · 39h · 40h · 41h · 42h · 43h · 44h · 45h · 46h · 47h · 48h

Regional model, satellite simulation, Eastern United-States window

The forecast set is updated between 4:00 and 5:00 UTC. Images for forecast hours...00 h UTC + ...

Animation · 03h · 04h · 05h · 06h · 07h · 08h · 09h · 10h · 11h · 12h · 13h · 14h · 15h · 16h · 17h · 18h · 19h · 20h · 21h · 22h · 23h · 24h · 25h · 26h · 27h · 28h · 29h · 30h · 31h · 32h · 33h · 34h · 35h · 36h · 37h · 38h · 39h · 40h · 41h · 42h · 43h · 44h · 45h · 46h · 47h · 48h

The forecast set is updated between 16:00 and 17:00 UTC. Images for forecast hours...12 h UTC + ...

Animation · 03h · 04h · 05h · 06h · 07h · 08h · 09h · 10h · 11h · 12h · 13h · 14h · 15h · 16h · 17h · 18h · 19h · 20h · 21h · 22h · 23h · 24h · 25h · 26h · 27h · 28h · 29h · 30h · 31h · 32h · 33h · 34h · 35h · 36h · 37h · 38h · 39h · 40h · 41h · 42h · 43h · 44h · 45h · 46h · 47h · 48h

Regional model, satellite simulation, Western United-States window

The forecast set is updated between 4:00 and 5:00 UTC. Images for forecast hours...00 h UTC + ...

Animation · 03h · 04h · 05h · 06h · 07h · 08h · 09h · 10h · 11h · 12h · 13h · 14h · 15h · 16h · 17h · 18h · 19h · 20h · 21h · 22h · 23h · 24h · 25h · 26h · 27h · 28h · 29h · 30h · 31h · 32h · 33h · 34h · 35h · 36h · 37h · 38h · 39h · 40h · 41h · 42h · 43h · 44h · 45h · 46h · 47h · 48h

The forecast set is updated between 16:00 and 17:00 UTC. Images for forecast hours...12 h UTC + ...

Animation · 03h · 04h · 05h · 06h · 07h · 08h · 09h · 10h · 11h · 12h · 13h · 14h · 15h · 16h · 17h · 18h · 19h · 20h · 21h · 22h · 23h · 24h · 25h · 26h · 27h · 28h · 29h · 30h · 31h · 32h · 33h · 34h · 35h · 36h · 37h · 38h · 39h · 40h · 41h · 42h · 43h · 44h · 45h · 46h · 47h · 48h

These cloud forecast images are produced twice a day, around 17:30 UTC and 05:30 UTC (Universal time coordinated). To convert UTC time to local time, you have to take into account the time difference between your time zone and Greenwich time zone as well as daylight time if necessary. Thus,

• 17:30 UTC = 14:00 Newfoundland standard time (winter) = 15:00 Newfoundland daylignt time (summer)
• 17:30 UTC = 13:30 Atlantic standard time (winter) = 14:30 Atlantic daylight time (summer)
• 17:30 UTC = 12:30 Eastern standard time (winter) = 13:30 Eastern daylight time (summer)
• 17:30 UTC = 11:30 Central standard time (winter) = 12:30 Central daylight time (summer)
• 17:30 UTC = 10:30 Mountain standard time (winter) = 11:30 Mountain daylight time (summer)
• 17:30 UTC = 09:30 Pacific standard time (winter) = 10:30 Pacific daylight time (summer).

A few words regarding the colors on these images.

• Orange and white zones represent the coldest clouds, hence high clouds of cirrus type.
• Blue zones are low or mid-level clouds.
• Brown-green zones could be low clouds and/or the ground depending on the season.
• Turquoise zones show the ground.

To determine if you are looking at the ground or low clouds, do an animation and note if there is any motion of the brown-green zones. If you see movements, you are looking at low clouds. If the brown-green zones spread rapidly in all directions, you are probably seeing night time ground cooling.