Happy Eldora Day!

Error distribution for Opensnow forecasts at Eldora

Error distribution for Opensnow forecasts at Eldora

Eldora Mountain Resort opened today. Which means that I can now take the bus to go boarding. Woot! In honor of that, I’m dedicating this post entirely to Eldora.

First, let’s look at the error distribution from the forecasts at Opensnow. It’s plainly clear that the distribution is not normal. There is a huge peak for errors between 0″ and 2.5″ and then the distribution falls of quickly (quicker on the negative side). The mean of the distribution is 2.248″ and the standard deviation is 2.760″. (If you really care, the skewness is 2.159″ and the kurtosis is 3.562″.) There are 4 days where the prediction was off by more than 7.5″.

Two of the error values are related, in that there was a large over-prediction one day and then a large under-prediction the next. That’s an artifact of my tracking since I only keep track of 24 hour snow forecasts. I’d like to keep track of 24, 48, and 72 hour forecasts, but that would involve extensive re-writing of code. However, if I did this it would be easier to verify storm totals. Right now, I really can’t do that since forecasts get updated every day. I’ll possibly add this when I have the time.

Error distribution for NWS forecasts at Eldora

Error distribution for NWS forecasts at Eldora

This is the NWS error distribution. There are again some obvious things that stick out. First, this distribution is heavily skewed to negative values, meaning that most of the time NWS is under-predicting at Eldora. However, if we look at the mean value it is 1.736″. So that one extreme over-prediction skews the mean to positive values. The standard deviation is 2.400″, which is less than Opensnow. I use standard deviation values as a proxy for how good overall the source is at predicting at a certain resort. The lower the value, the higher the skill. It’s not perfect, but it gives you an idea of how well forecasters are doing.

Eldora isn’t going to get snow today, but it’s a beautiful bluebird day out there. So I’m sure everyone that could make it is having a blast.

In site news, I’m still working on integrating the graphs into the resort pages. That won’t be finished until after Thanksgiving I don’t think. I simply don’t have the time to devote to it right now.

Until tomorrow!

My name is Nathan Johnson and I have a Masters degree in Meteorology. I also snowboard and live in Boulder, Colorado.I have a strong desire to see precise, accurate snow forecasts. It is my hope that independent validation and verification leads to better forecasts.

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