Cloud Forecasts for Astronomers

[Phil Hart]

I started writing a post on my website about how to access raw cloud forecast data from the US GFS numerical weather model:

http://philhart.com/cloud_forecasts

Halfway through writing it, I discovered the launch of a trial alternative to the Clear Sky Clock for the rest of the world! It's called "APanel" by 7Timer:

http://7timer.y234.cn/V3/product.php...d=1&country=AS

It's what we've all been waiting for!

The raw data access I describe on my website has been quite good for the few months that I've been using it. For 2-3 nights ahead it's a great tool and better than any other combination of resources I've been using (and as much as I hate to say it, it's probably now better than most human forecasters, qualified or otherwise). It's been particularly good at forecasting high cloud which has often been a spoiler to other forecasts.

The APanel is based on the same US GFS model so the cloud forecast accuracy should be pretty good. I'm not sure how good the Seeing/Transparency forecasts will be - that will take an amateur community effort to assess!

The raw data access can provide much more detail about low/medium/high cloud, whereas the APanel lumps it all in one figure but it's much easier to use!

cheers
Phil
www.philhart.com/gallery/Astrophotography

[GTB_an_Owl (Geoff)]

thanks for that Phil

will go back and have a good look later

geoff

[RobF (Rob)]

Absolutely fantastic. Thanks Phil.

Have been organising a few links people had recommended to prepare for viewing nights, and didn't expect anything this comprehensive for Brissy for a while.

Rob

[Hagar (Doug)]

Great stuff Phil. The 7timer data got it spot on for here tonight. Didn't look good but it all cleared nicely.

Thanks Mate.

[iceman (Mike)]

Great, thanks Phil. I'll give it a whirl for my location.

[AstralTraveller (David)]

Great!!

I'll watch this site closely and compare the actual conditions to its forecast. It has the current conditions about right.

Thanks

[Jazza (Jay)]

Hey interesting site!
Got a problem though, (I may just be being stupid)
See the attached image.
What day is what?
Is the left most Sunday and the next (labelled Sunday) actually Monday?
Or is the one on the left Saturday (yesterday) and just not labelled?

[Liz]

Looks interesting, we have a public Astronomy night Monday, and its forecasting partly cloudy ....
Well, Jazza, that does look tricky, but then I realised it was Tassie time

[Jazza (Jay)]

*still looks lost*

[Alchemy (Clive)]

stunning , hope it works , have had a look , will keep an eye to see how well it does.

[§AB]

wow, worse than 2.5" seeing (the worst possible option) for every dot in Berwick. Now there's the proof I suspected all along But atleast now I know for 100% that my telescopes are not to blame for the constant blurry Jupiters and mangled stars

btw, that's a really cool find Phillip, thanks! It makes the American Clear Sky Clocks look like crap lol

[GTB_an_Owl (Geoff)]

have put a couple of links on my weather page for Terrigal and Mangrove for you local lot to look at if that is easier for you

geoff

[stringscope (Ian)]

Thanks Phil. Great find

[Phil Hart]

I've managed to go one big step better than my first round of information:

http://philhart.com/cloud_forecasts

It's possible to produce cloud forecast maps like the one below. This forecast was made yesterday for midday today (compare it to the satellite image for the same time).

Having a map enables much better intepretation than just boiling cloud cover down to a single percentage figure for one location.

I've also put a page together with a set of images comparing an actual infrared satellite image with forecasts made on the same day and up to 5 days ahead. The upshot is that forecasts 2-3 days ahead are pretty good! Beyond that it gets a bit flaky..

http://philhart.com/cloud_forecast_accuracy

cheers
Phil

[dugnsuz (Doug)]

Thanks Phil - this helped me plan my nights work...Darks!!
Cheers - a very useful find.
Doug

[glenc (Glen)]

Thanks Phil and Ye Quanzhi.
http://www.skyandtelescope.com/news/30516864.html
http://7timer.y234.cn/V3/product.php...d=1&country=AS