What’s with London’s freakishly warm fall weather?

Article content

London has seen some unusually warm autumn days so far, which have broken records or come close to doing so. Reporter Jack Moulton spoke with Environment Canada meteorologist Geoff Coulson about what’s going on, and what to expect.

Q: Last week, even Halloween Day, was surprisingly warm. Have there been a lot of records broken, or at least close calls recently?

Article content

Those last three days of October certainly saw a number of records set, or at least approached in the area. London did set a new record on Oct. 29 last week, (it) got up to high of 21.8 C, and that beat the old record (for that date) of 21.7 C set back in 1946. Currently, on Tuesday, we’re forecasting a high of 23 C, and the current record for Nov. 5 is 22.8 C set back in 2015.

Q: What is going on to cause this on and off warm weather?

We’re seeing a real progression of weather systems moving through. In advance of the weather systems are winds that have been coming from the south and the southwest, our warm-wind direction, and that’s been bumping the temperatures up and giving us the possibility of record-setting temperatures.

Then, when these weather systems roll through, when the cold front associated with them passes through, we tend to drop down to more seasonal temperatures. That trend looks like it is going to be continuing into the month of November.

Q: Are the goalposts shifting into November?

I think the overall forecast is still to have conditions warmer than normal in November, but the chances of seeing high temperatures in the low 20s will diminish as we get further into the month.

Article content

Article content

(There are) already some hints that as we get into next week, the possibility of the temperatures bumping back up again, perhaps not, as we said, to the low 20s, but still the potential of getting back into the teens for those daytime highs.

Q: Are these weather systems just happenstance, or is there something else contributing to it?

One thing of note in more recent weather patterns is the jet stream, which is our strong winds in the upper atmosphere.

That jet stream tends to act as the boundary between colder air masses to the north and warmer air masses to the south, and we’ve noticed over the last number of weeks that the jet stream has remained fairly far north, and so that’s kept a lot of the more active weather over more parts of northern Ontario, and also kept us in a somewhat milder airflow.

We may start to see more in the way of active weather as the month progresses. At this point, likely more in the form of rain, given the milder temperatures. But every once in a while, if we do get a blast of colder air, it could bring the possibility of some mixed precipitation, rain and snow, or even just some snowfall.

Article content

Q: What are you looking for heading into winter?

We had quite a long winter last year, and that was related to a very strong El Niño event, the warmer than normal waters in the Pacific off the coast of South America.

This year is expected to be a weak La Nina event. La Ninas don’t tend to affect our temperatures all that much, but we may in fact see a bit more in the way of precipitation. The overall forecast right now for the winter, which has been fairly consistent over the last number of weeks, is talking about generally warmer than normal conditions for November, December and for January.

Now, those forecasts are based on the average temperature. So there’s still lots of potential for us to tap into colder air masses, and to get shots of snow and lake-effect snow in the London area.

jmoulton@postmedia.com

Article content