May 17, 2022: Aftercasting

We’re not forecasting any more, but Sean always finalizes his graphs to see how close the predictions came.

Short version: the thaw went better than expected.

Before we examine the final version, let’s go back and look at this spring’s first forecast, from late April.

You can click on these to see larger, sharper versions.

Early in the spring, Sean estimated that we’d need to reach a target thaw index of 190 points. That’s the horizontal yellow line. That value of 190 was based on the severity of the winter. Last winter’s freezing index was close to 1900 points, and a ratio of ten to one is his starting point for predicting the thaw.

April Thaw Forecast Graph.

The blue line is formed by plotting this year’s daily temperatures (Mean Daily Temperatures, to be specific). In the early spring, he sketches in the blue line using the weather forecasts, and then as time passes, he replaces the forecast line with actual data.

Now here’s the post-season analysis version.

Final Thaw Graph.

As you can see, the blue line plotted from actual weather reports rose more steeply than the early version based on weather forecasts.

Also, the ice melted at a slightly better rate than the base ratio of ten to one predicted, so the thaw was complete (marked with a yellow star) at a lower thaw index than the target of 190. It happens. Temperature is a big factor in the thaw, but it’s not the only one. Some of the other factors aren’t included in weather forecasts, especially long-term ones.

Perhaps you’d like to see how this spring’s temperature profile compares to other years in our records. Sean has a graph for that, too.

Spring Temperature Trend After Inflection.

In this graph, the timeline across the bottom is synchronized to each year’s Inflection Date, not the calendar date. Also, the lines for previous years continue to plot the rising cumulative index even after the ice is gone. We’re just comparing spring temperature trends, not trying to factor in ice thickness or anything like that.

This year’s data is shown in a dotted line, and it’s the second highest track on the graph. On both this graph and the previous one, that red line that we didn’t quite equal represents 2007, a very warm spring, so we did quite well this year. As Sean commented, once we finally got Mean Daily Temperatures above freezing*, they were often in double digits.

*When the Mean Daily Temperature goes above freezing and stays there, we call that the Inflection Date, and that’s what Sean bases his graphs on.

Lastly, the Shark-fin graph.

There’s really only one change to this. This year’s ice-out date of May 16 has been marked with a red dot, bringing the thaw phase to a close.

Shark-fin Graph.

Sean will continue to plot the summer numbers on here so that we can see how much summer heat we accumulate, which will affect water temperature and the inevitable freeze next winter.

In the meantime, here’s hoping that he can plot a summer fin that is tall and wide, because that would be the sign of a season that is both warm and long.

Signs of spring: The trees are leafing out, and I saw daffodils blooming in someone’s garden today!

Fun tidbit: Sean did some internet sleuthing, and as far as he can tell, Lake of the Woods Ice Patrol is the only website of its kind anywhere in the world.

I think that’s about if for this year. I’d like to thank everyone that helped.

Sean, of course, for the graphs and predictions.

The pilots and drone operators, and everyone who sent in photos. They made Ice Patrol possible this year.

The donors, who alleviated the stress of trying to do this on a shoestring budget. Having enough money to book flights meant I didn’t have to worry about going without aerial photos in the critical weeks.

The people who participated via email or the comments form. I received a lot of very helpful information from those sources, and it’s growing as a way to pool our knowledge.

And lastly, the followers and visitors. Ice Patrol had a busy spring this year, racking up nearly 75,000 views in under five months. Traffic peaked at over 2400 views a day. That keeps me going, and I’m tickled that people check in from all over the world.

Thank you all.

Ice Patrol will now go (mostly) dormant until next spring.

Talk to you then!