April 23, 2019: Graphs

I didn’t fly today, so I’m catching up on some graphs and predictions.

First, an updated graph from Sean C. You can click on it to see it full-screen.

To recap:

The blue line with the plot points tracks our actual daily mean temperatures so far.

The yellow line is based on weather forecasts. In theory, this is the path that the blue line will follow, but it gets less reliable the further into the future you look.

The solid red line represents a warm spring that racked up lots of high daily mean temperatures in a short time. It’s sort of a best-case line.

The solid green line represents a cool spring that took a long time to deliver a decent amount of heat. This is more of a worst-case scenario.

The horizontal dotted red line represents our goal for this year, a thaw index of 240. As each day’s mean temperature gets added to the blue line, we rise towards that goal.

The target index of 240 points is based on last year because the winter conditions were very similar as to both the length of the winter and the depth of the cold.

The vertical dotted red line indicates a date we might make it by. It was set to May 17th when this graph was first created, but we’ve already started to improve on that.

We might have an easier thaw if last winter’s frequent snowfalls degraded the quality of the ice compared to 2018. Soft ice wouldn’t require as many warm days to melt, so we could do it with less than 240 points.

Here’s a graph I made, using data provided by Sean, but presented in a different way. It’s wide, so you should probably click on this one to see it clearly.

I’ve given each year a horizontal bar that starts on the inflection date (when the mean daily temperature rose above freezing on a lasting basis) and ends on the day Lake of the Woods was ice-free. The most recent year is at the top, and the oldest year (2008) is at the bottom. Rather than line up all the inflection dates at the left edge, I displayed them on a calendar base, because a May thaw is apt to apt to get more hot days than a March one. You can see this: the lines that start really early run longer than the ones that start late.

Now it happens that our inflection date this year was April 13th, the same as 2016. I’m confident that this thaw will take at least as long as 2016’s, which ended on May 4th, so this year’s bar is solid blue up to that date. Realistically, there’s little chance of getting off that easy. The winter of 2015/2016 was a mild one, and the ice didn’t put up much of a fight.

I’ve tentatively shown a longer period of uncertainty in pale blue. I ran that out to as late as May 17th. That’s to match the prediction from Sean’s graph. I’m really hoping that’s on the pessimistic side. I didn’t have the heart to project anything worse.

It might be possible to be ice-free around the middle of the range—May 10th or 11th—if we thaw as fast as last year. We’re doing well in that regard right now, but there’s cooler weather forecast for the weekend and next week that could slow things down again.

The final result may depend on two basic things: how much ice we can melt during our current warm spell, and how that forecast cooler weather plays out.

There are also two wild cards: rain and wind. Rain has an enormous capacity to deliver heat energy deep into ice if there are cracks. Wind can do violent damage to ice sheets once there’s open water in contact with them.


April 15, 2019: Sean’s Analysis

I didn’t do a Signs of Spring post yesterday, but if you’re interested, snow is retreating wherever the sun shines, but lingering in shadowy places. I’ve seen a pair of Mallards, my first ducks of the year. Also a pigeon and a pair of Whisky Jacks. I heard a second-hand report (hearsay!) of a robin. Cyclists are emerging from their winter dens.

And now onto the main topic.

Contributor Sean C. is finally confident that we’ve reached the inflection point, the date when our daily mean temperature rises above freezing on a lasting basis. He figures this took place on Saturday, April 13th.

That means that from now on, the ice will be melting steadily.

Here’s the first of his graphs, depicting the severity of the winter.

Each of the downward spikes represents a winter, ending on the date of the inflection point. The depth of the spike represents the severity of the winter, and the width of the spike represents the duration of the ice-making period. In a nutshell, the winter that just ended was not the worst, but it was a very close match for the previous winter, which was pretty bad.

You can click on these graphs to see them full-screen and a bit bigger.

Here’s Sean’s graph comparing the way some recent winters unfolded.

2019 Freezing Index

In this figure, each winter gets a line in a different colour, and tracks across the calendar until it ends on the inflection date. A short shallow line, like 2012’s medium blue one at the top, represents a mild winter that started to thaw early. The awful winter of 2014 (which was also the deepest downward spike on the first graph) is the grey line that slopes down and down, making ice until mid April. Above that are two lines that track together at the end. The dark blue one is from a year ago, and the dark red one is this year. These years look as closely matched on this graph as they do on the first.

Okay. We’ve established that it was a crummy winter that dragged on into the middle of April. Now what?

Well, now Sean uses some math to figure out how much heat we’ll need to melt the ice formed over such a winter. He works out a thaw index based on the severity of the winter. The index lets him make predictions based on the long-term forecast, and it works like this: If a day has a mean temperature of 5ºC, we add five points to the total. If a day has a mean temperature of 7º, we add seven, and so on*. Then he works out how many of those points we’re likely to need to thaw this winter’s ice.

2019 Preliminary Forecast

Sean’s first version of this graph used the same thawing index he forecast last year: 200. However, when I asked Sean if it might be better to use the actual index of 242 that came to pass, he reconsidered, and issued a new version of the graph using an index of 240.

The amended graph now replaces the earlier version on this post. The higher index adds another day to the estimated time until we’re ice-free.

On this graph, the red line represents a really warm spring (2007) that hit 200 points in early May and the green line depicts a cold spring (2004) that took much longer. Please note: this graph isn’t about the thaw in those years, it’s just about how rapidly we accumulated enough warm weather. The very short blue line hiding in the lower left corner is 2019, with data points marked by blue dots to show the actual daily mean temperature achieved. The yellow line is what the weather forecast says we’re likely to get. If the forecast is accurate, the blue line will grow along the yellow path, and Sean will extend the yellow line as new forecasts come into effect. (There are longer forecasts, but plotting them day by day at this point would be wishful thinking)

The horizontal dotted red line indicates the target thaw index of 240 estimated for this year, while the vertical dotted red line marks the date we might reach it, based on the trend in the longer-term forecasts.

*A sort of fun thing we learned about daily mean temperatures: you might suppose that if the daytime high was 10ºC, and the overnight low was 0ºC, then the mean daily temperature would be 5ºC. That turns out to be not quite right. Actually, such a day is likely to produce a mean temperature closer to 6ºC. We seem to spend more hours near the high than the low. Perhaps this is due to spring’s long days and short nights.

If you’ve been following along, you’ll have noticed that the predicted date for reaching the target of 240 points is May 87th. May 18th is bad. It’s even worse than last year, mainly because the temperatures forecast for the next weeks are not high.

Still, there are other factors to consider.

The index itself is not precise; it’s an educated guess based on turning a limited set of  past data into a mathematical formula.

A more positive influence might be ice quality. All that snow this winter made for some poor ice. If it’s weaker and softer, it should melt faster.

Then there are the usual wild cards: rain, wind and sunshine.

In summary, this year looks a lot like last year. Rosy forecasts haven’t panned out, and a normal ice-free date in early May looks unlikely.

Plan on the middle of May and cross your fingers.



March 19, 2019: Graphs

Yesterday I talked briefly about Sean’s method for analyzing the winter temperatures to see how much ice we were likely to have. Here’s his first graph for 2019, an update that shows how this winter compares to the last few.

Each spike above the center represents a summer, with the rising line showing the degree days above freezing. When the mean daily temperature falls below zero in the autumn, the line drops vertically and the downward spikes show the degree days below freezing.

A spring day with a mean temperature of 10ºC would be ten degree days.

Based on the severity of the winter Sean estimates how many degree days it will take to thaw the lake, and then looks at the forecast to see how long that might take.

It doesn’t matter much whether we have eight weeks of barely above freezing temperatures, or three weeks of exceptional heat: the numbers come out about right either way. Once enough heat energy is delivered, the ice is gone.

Freeze Thaw Index Graph

So what can we see from this updated graph? The last point on the graph shows that right now, we’re still below freezing most of the time. On the day that the mean temperature goes from below freezing to above*, Sean will draw the vertical upward line that marks the end of winter and place a blue cross on the chart.

Once we reach that point, he’ll be able to estimate our Thaw Index: the number of degree days it might take to melt that much ice.

*For the long term, that is. A single above freezing day does not mark the change of seasons.

But we can already see that this has been a long cold winter. With a freezing index of -1756 degree days, we’re in the same ballpark as last winter. The two winters before that were a lot milder, and you’d have to go back to 2014 to see one that was much worse. That was an ugly winter.

Sean sent along another graph that compares the recent winters in a different way.

Winter Severity Graph

On this plot, each winter gets a different coloured line. Each line ends on the date the mean temperature rose above freezing. This (2019) winter is the dark red line. It goes horizontally after today’s date because we don’t have the whole story yet. We don’t quite know when we’ll switch to thawing and end the line.

That brutal 2014 winter is the grey line at the bottom. We made a lot of ice that winter.

Sean made an interesting point about last winter, represented by the dark blue line. It was leveling off nicely, looked like it was all over, and then things turned cold for three more weeks, which you can see as a late dip in the line that extended it into April.

In summary, this winter was cold enough to make a lot of ice.

There are two things that might tip the balance in favour of an earlier thaw: reports that the ice is not very solid because of frequent snowfalls, and a long-range forecast for warm spring weather.

I’ll start on aerial photography when I have a flight on a  clear day.


November 15, 2018: We’re Making Ice

We’ve changed seasons. The average daily temperature has dropped below freezing, and it looks like the actual inflection date was November 7th. Effectively, that’s when freezing became the fashion, rather than the fad. In the week before that, average temps were right around 0°C, except for a mild Sunday on November 4.

Sunday, November 4. The pond by the Scenic Nook trail on Tunnel Island had mostly frozen over.

On Wednesday the 7th, the daily average dropped to -4°C, and in the following week it went as low as -9.5°C.

Same pond a few days later

The forecast calls for fairly consistent low temperatures in the next weeks, and let’s face it, we’re not going to start any serious melting in December. Remember, we’re talking about daily averages here, not daytime highs.

In summary, we’re making ice now. North of Red Lake, small lakes have been frozen since about the beginning of November, and on yesterday’s training flight, I saw small bays on Lake of the Woods were icing over. Strong winds were keeping larger areas from freezing, for now.

This time of year, I always see an upsurge in emails and comments asking if I’ll be reporting on ice thickness. Ice fishers want to know! Sorry, I will not. I cannot judge the thickness of ice from an airplane, and I worry that if I report that a certain bay has frozen, people will take that to mean the ice is thick enough to support them safely.

Someone sent this graphic my way. It doesn’t say which Department of Natural Resources, but I think the credit goes to Minnesota. Note the caveat that these guidelines should only be applied to new clear ice.

Have a safe winter.



May 14, 2018: All Clear

I went flying today, and saw no ice on Lake of the Woods. You can click on this picture to view a larger version and zoom in to see for yourself.

In this photo, the nose of the King Air is aimed at Middle Island, with Hay Island to the left, Scotty Island just right of center, and Whiskey Island at the extreme right. The full span of the Barrier Islands is visible in the middle distance, and there’s no sign of the ice that was holding out in that area.

Yesterday’s satellite images were blurred, but some ice was visible. Today’s had some cloud cover, but by comparing two images, I was able to see pretty much the whole lake, and there was no visible ice, so I think even the ice down by Baudette is gone.

So I’m calling it. As of today, Lake of the Woods is ice free. The brick graph gets a magenta block for 2018 to celebrate.

This spring was one of the four latest springs of the sixteen on the graph; behind the curve, but not outrageously so.

To show the timing of the onset and conclusion of the thaw, here’s the finalized version of the floating bar graph. Each year’s bar starts on the Inflection Date (when the daily mean temperature rose above freezing) and ends on the date when the lake was ice free.

Depending on your monitor size and settings, you might want to zoom in on this to read the numbers. In summary, it shows that compared to other recent years, the 2018 thaw got off to a late start and then went fairly fast.

A quick note on other lakes in the region: all lakes in the Kenora, Red Lake, Sioux Lookout and Dryden area are clear of ice, with three exceptions:

  1. Shoal Lake, west of Kenora, still has a large patch of ice.
  2. Trout Lake, east of Red Lake, still has extensive ice.
  3. Lac Seoul, near Sioux Lookout, still has some ice near Kejick Bay.

I’ll be wrapping up the Ice Patrol for the season in the next few days. Thanks to everyone who visited this year- I had record traffic!

Special thanks to all who contributed with photos, comments or emails.

I couldn’t have done it without the help of my co-workers at MAG Canada.


May 11, 2018: Remnants Persist

Yesterday I said the weak ice between Scotty Island and Whiskey Island would be gone overnight. Wrong! Garry Hawryluk passed overhead on a WestJet flight at 6:00 this morning, and managed a few pictures at dawn. The light was poor, so I’ve enhanced the contrast on this one to make the ice more visible.

What I like about this photo is it shows the full span of that ice sheet south of the Barrier Islands. But if you look just above the big expanse of ice, you can see that the small patch in the Manitou survived the night. It did dip below freezing last night, but I think a bigger factor was that the wind died out: without wave action, the candled ice did not break up or blow away.

My own nefarious plan was to hold off on taking pictures until this afternoon, so I could say, “it was gone when I looked.” Unfortunately, it was still hanging on at 3:00pm.

This picture is centered on Town Island. Click on it to see a larger image, and click on that to zoom in, and you can see that small pans of ice still persist on the Manitou.

At full magnification, you can also see a boat passing by Lunny’s Island. The water is so smooth you can trace the wake all the way back to the Hades!

This picture shifts over to the left to show more of Bigstone Bay and Hay Island. Zoom in on this one and you can see a tiny forlorn patch of ice clinging to Needle Point, just left of the center of the picture. But the real reason I took this photo is I wanted to show the larger sheet of ice in the distance. The top right corner of the picture shows the area south of East Allie Island, and that big expanse of ice there is still, well, big. It looks set to hold on a bit longer.

Now that the thaw is almost complete, Sean and I are looking forward to finishing up our graphs for 2018.

Here’s Sean’s latest version of the prediction graph.

We reached a Thaw Index of 200 today, which Sean guessed (several weeks ago!) would be enough accumulated heat to melt all our ice. It turned out to be a very good guess, especially for a first attempt. Sean used temperature data from past years to work out a relationship between how cold a winter was and how much warmth it takes to melt the ice. That didn’t give him a magic number, it gave him a range. He still had to choose whether this year’s thaw would be rapid or sluggish. He went with a swiftish prediction, and chose a thaw index of 200 as his best guess. (A thaw index of 200 means that starting on the day the temperature averages above freezing, we add each day’s mean temperature to a total. When it adds up to 200, we hoped to be ice free.) Because it was late in the season, I also felt that the thaw would be fairly rapid, but it looks as if the ice won’t be 100% gone until we climb a bit higher than 200.

Remember, my method in previous years was to take aerial photographs and compare them to my archived pictures, and look for the ice to melt at roughly the same pace as those previous years. In other words, I didn’t even try to factor in the forecast, unless it called for a significant run of good or bad weather.

The trick with using long-term weather forecasts to graph mean temperatures in advance is: they’re forecasts, and they go wrong. This April, forecasts were calling for miserable weather. And they were right, at first. Then as May arrived, we started to get much warmer weather than predicted. Changes to the weather forecast meant changes to the ice-out date, but not to the desired index.

I won’t be flying again until Monday. Will I find any ice at all by then? We’re looking at a warm weekend. I’m guessing not.

May 7, 2018: Tom Stoyka & Dan Zvanovec

First a couple of pictures from a pair of guest contributors, Tom Stoyka and Dan Zvanovec. Tom did the flying, Dan took the pictures. They were flying over the west end of the Manitou, around Brûlé Point yesterday.

This picture looks west, with the tip of Brûlé Point dead center. Above that is Ptarmigan Bay, which looks to be mostly open, but you can see ice further west by Copper Island. In the foreground, by the leading edge of the wing, is a big pan of ice in the west end of the Manitou. These pictures were sized for speedy emailing, so you cannot click on them to see a high-resolution version.

This is a closer look at the same area. Brûlé Point is at the very top right corner above the wingtip, and the land in the upper part of the picture is part of the Western Peninsula, including Bluebell Lake at the left edge.

Thanks to Tom Stoyka and Dan Zvanovec for these photographs, and to Karen Loewen, who got Dan’s permission and sent them to me.

Next up, the latest graph from Sean C.

We’re still making rapid progress, warming up almost as fast as 2007, and staying on track to be 100% ice-free by May 11. That’s a full week better than I expected back in mid-April.

I’d like to take a moment to talk about one of Kenora’s best kept secrets. As an author, it bothers me that so many people don’t know we have a local independent bookstore.

Elizabeth Campbell Books is on Main Street, right next door to the Plaza Restaurant.

Elizabeth is a stellar supporter of local authors like me.

If my brand of girl-power science fiction isn’t your cup of tea, she’s got non-fiction as well as fiction, plus art and photography books, kid’s books and indigenous art.

Want to read about Kenora’s infamous bank bombing? The Devil’s Gap by Joe Ralko tells the story of Canada’s first suicide bomber. Bush Flying Captured features the splendid aircraft photography of Rich Hulina. Local history? Community Ties by Kathy Toivonen and Kim Manduca explores the railways of Northwestern Ontario.

There are many more great titles that I couldn’t list here.

She also has whole rooms full of used books perfect for the cottage or the trip to and from it, so don’t hesitate to look beyond the front showroom.

I hope to have more new pictures tomorrow. In the meantime, I’ve updated the satellite links, and added a new one. I haven’t had much time to play with it yet, but Kevin Weber sent me a link to the NASA site that shows the MODIS pictures. In these images, the view of Lake of the Woods is at an angle from the south.

Summary: some Lake Dwellers will be able to reach their camps near Kenora already, and more of the lake will be opening up every day. Keep an eye on the comments section for reports from active boaters.