Is The Clear Sky chart reliable ?

[MG877]

Just curious how accurate is it , Either my chart lies to me or it is set up for some other planet !!

Last night it showed more dark blue than I have ever seen for cloud cover , seeing and transparency but outside was very cloudy . For tonight we have a white block in the cloud cover but tonight's weather forecast says says mostly clear .

Does any body find this a reliable tool ? or am I reading it wrong .

[njjmfm]

It is reliable. It's usually for the center of town or the observatory. Sometimes, weather can be very different in just a couple of kilometers

[Bob327]

Its a very rough "guesstimate" but I still use it However I sure take it with a grain of salt...

Bob G.
..

[fogfire]

It is more reliable than most other systems and when I doubt it I get kicked.

Example
Friday Accuweather said 10 of 10 for stargazing Clear Sky Clock said overcast. I thought it would be wrong.. it was right.
Last night Accuweather said 2 of 10 for stargazing Clear Sky Clock said it would be good until 1am. it was very clear at night until (guess when my clouds started to roll in)

No prediction system is perfect and you need to click on the square to view the full prediction map to see if you are on the boarder between two different weather types.. etc.. you need to learn to look at the full prediction.. but usually it is with in 1-2 hours of my cloud cover here. Which is pretty good.

[KeithBC]

It helps to understand how it is generated. Environment Canada creates computer-generated maps for the various parameters (cloud, seeing, transparency, etc) at hourly intervals. The computer model is quite good, better than their regular public forecasts, but it is after all, just a computer-generated map. Your clear sky chart is one pixel from each hour's chart. Here is the chart for tonight's cloud cover, with my pixel highlighted with a "+".

Untitled.jpg

So, the possible issues include both the accuracy of the computer model and the spatial resolution of the prediction. I have had the model forecast cloud throughout the region except for a small patch of clear sky over me. Since the clear patch was forecast to remain stationary, my clear sky chart showed a totally clear evening. In reality, the area was clouded over except for a small clear patch 3 miles east of me that remained stationary all evening. Was the model wrong? Not at all. In fact, that was some pretty @#$% good predicting. A 3-mile error on a continent-wide scale? That is impressive! But it made the difference between all-blue and all-white on my chart.

[MG877]

Thanks for the info guys , guess I will keep rollin the dice and hopefully get better with more experience .

[Pinkfuzzysocks34]

I sometimes feel the same way. It says it's going to be a great night for stargazing but then it clouds up and starts to storm, as predicted by NOAA. I roughly follow it, but generally don't make any concrete plans based on what it says.

[KeithBC]

If I have any doubt at all about the chart's predictions, I always click through it to the map to see what it is really trying to tell me.

[jdvann]

How much faith can you really put in the weather man? It's the oldest joke in the book....They have gotten better, but I believe they are better at telling you what is happening right now vs whats gonna happen.

[MG877]

Thank you Keith good post ! One more challenge to overcome on the never ending learning curve . If there were no challenges I would be board and I do not see that happening any time soon !