Insights & News

“Ice in November to Bear a Duck…”

1st November 2019

Every autumn in the UK, this phrase from old weather lore starts appearing on weather forums:

“Ice in November to bear a duck, rest of the winter be slush and muck.”

In fact, I’ve genuinely seen this used as a basis to anticipate that winter will be either mild and wet, or cold and dry, depending on whether there’s been pond ice that can bear the weight of a small bird.

So, surely there’s truth in this connection reflected in observation data…?

Daily Detail to Dive Deeper
…Investigating The Lore

To check this out a bit, I’ve chosen to take the “Ice in November to bear a duck” part of the lore as literally as I can.

Rather than associating that with Novembers that were colder than average overall, I’ve taken a deeper dive, into the daily temperature data.

In this way, short spells of freezing weather within otherwise not very cold months are picked up (a monthly temperature mean will overlook such a thing).

Novembers with one or more days cold enough to produce pond ice at least a few centimetres thick (ducks don’t weigh much) have been awarded INTBAD (Ice in November To Bear A Duck) status.

Now of course, this isn’t an exact science – that would require records, spanning many decades without interruption, of whether ducks walked on ice or not. As far as I can see, such a thing does not exist (but please do let me know if I’ve missed something!). So, estimation will have to do.

‘Now of course, this isn’t an exact science – that would require records, spanning many decades without interruption, of whether ducks walked on ice or not. As far as I can see, such a thing does not exist…’

The Duck-Bearing Ice Estimator…

I have classified INTBAD months according to two simple temperature criteria. They’re based on first-hand experience, as, the past two decades, I’ve paid an unusual amount of attention to what’s going on with the weather and why. (Though less time observing duck welfare.)

Days Where Ice Might Have Held A Duck

Qualifying Novembers feature at least one instance of:

Either… A night with an overnight min. temp. of -5°C or below
Or… Two nights with overnight min. temp. of -3°C or below, and an intervening max. temp of 3°C or less

It was then simply a matter of analysing the weather data for only the winters (Dec-Feb) following INTBAD Novembers. The interest here is in how many of those winters were milder or wetter than average (positive anomalies).

Figure 1 displays a statistical analysis of the post-INTBAD winters for three cities. Cities were chosen to represent a far stretch of the UK: London, Leeds and Glasgow.

83% Nonsense?

When looking for patterns in anomaly data for a specified sample (in this case, group of years), a type of plot called a Box-and-Whisker comes in handy. It can be used to quickly assess how many items in the sample fall within certain distances of the zero line. More importantly, you can see how many are within certain distances above, versus certain distances below.

In the variation that I’m using (Figure 1), the ‘box’ of the plot illustrates the range within which the majority of items fall, while the ‘whiskers’ (T-shapes) show the highest and lowest items.

Figure 1: Box-and-Whisker plots of winter-mean temperature (top) and precipitation (bottom) anomalies for each of three UK cities.

Figure 1: Box-and-Whisker plots of winter-mean temperature (top) and precipitation (bottom) anomalies for each of three UK cities.

 

We can see, for the winter-mean temperature anomalies, the data for all three sites are spread near-evenly around their respective means. In fact, the symmetry is striking for both London and Glasgow. This indicates no meaningful relationship between the INTBAD condition and how cold the proceeding winter is overall.

There’s also no clear link evident for rainfall in either London or Glasgow, but for Leeds there’s an interesting exception!

Almost the entire spread of data is above the zero line, which implies that INTBAD conditions tend to precede a wetter than average winter there. In fact, 8 of the 11 identified winters were at least 15% above normal, which is an impressive proportion (~73%).

Something to Bear in Mind?

So, does this mean that “Ice in November to bear a duck, rest of the winter be slush and muck” is worth keeping in mind for northern parts of England?

Perhaps, but caution is advised – we’re only talking about one location here, and with such a small sample size, the high proportion of wet winters corresponding to INTBAD conditions could well be a result of other factors, or just a big coincidence.

Having said that, of the many examples of old weather lore, INTBAD is among the strangest, so finding any statistical patterns is enough to raise an eyebrow or two.

 

James Peacock MSc

Head Meteorologist at MetSwift

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