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Weather Has A Way Of Evening Out

The weather page is prepared by Daniel Bezte. Dan has a BA Honours degree in geography, specializing in climatology, from the U of W. He has taught climate and weather classes at the U of W, and is a guest climate expert on CJOB’s morning show with Larry Updike. Daniel runs a computerized weather station on his 10 acres near Birds Hill Park, which he plans to develop into a small vegetable and fruit hobby farm.

Daniel welcomes questions and comments at [email protected]

It seems like our “stupid weather” has been replaced by, oh I don’t know, crazy, summer, hot weather – you take your pick. But there has definitely been a complete 180 in our weather! Starting pretty much right in the middle of the month, our weather went from some cruel spring-like joke, with near-record cold (and yes, some actual record cold) and the prospects of facing the sixth month in a row with below-average temperatures. Now we are facing mid-summer-like heat. In fact, looking back over the last dozen or so years, this current warm spell is the earliest long-duration heat wave (more than five days in a row) we have seen.

Don’t get me wrong, we do see hot temperatures in June, but they usually only last for a couple of days and then we see a day or two of cool weather before the heat returns. This year, the heat moved in on June 14th and it looks like it will last until about June 26th and possibly right through to the end of the month. Even in July or August that would be one impressive warm spell.

I don’t have the research paper I worked on back in my university days anymore, but I once looked at hot and cold spells across our region and whether or not they offset each other. It seemed like a good idea at the time, but by the time I finished the conclusions were basically – duh, of course they do! We are constantly dealing with average (normal) temperatures and using this as the comparison to how we are currently doing. Are we above-average or below-average today, this month, this year? When you think about it, we almost never see average temperatures. On any given day they are either above-average or below, and over the long run, these above-and below-average temperatures eventually cancel themselves out and we get a result pretty close to the average.

For example, most years the average temperature at any one place in Manitoba will usually average out to within 1 or 2C of the long-term average. If we look at monthly values we would see some months that are close to average while others are as much as 4C to 10C off the average for the month. Zoom in to the daily readings and once again we will have days close to the average, but we will often see days that are more than 10C away from the average. So, given enough time, periods of cold or warm weather will end up offsetting themselves, so yes, a period of cold weather will usually be offset by a period of warm weather.

Now, since we have gone through six months of colder-than-average conditions, does this mean we will now see six months of warmer-than-average conditions? Not necessarily. We could just as easily see the cool weather return. By the end of the year, chances are that we will likely be close to average for the year, and since we started off the year so far below average I would put my money on seeing more above-average temperatures between now and December than below average.

BACK TO THUNDERSTORMS

OK, enough of that. It is finally warm, so let’s enjoy it, and please don’t complain about it. A couple of weeks ago we were talking about thunderstorms and I promised we would get back to that discussion. In that discussion, we talked about just what ingredients you need for severe thunderstorms. We discussed rotating storms and venting at the top of storms. This week we will take a quick look at something called caps.

A cap is a weather term for a temperature inversion in the middle part of the atmosphere. This inversion prevents rising air from going any higher. In essence this cap or inversion acts like a lid trapping all the heat and energy close to the Earth’s surface. If the cap is strong enough nothing will happen. We will have a hot humid day, but any and all updrafts will be snuffed out before they can develop into a thunderstorm.

If the cap isn’t that strong, or the surface layer gets really warm, a really strong updraft can sometimes break through the cap. When this happens, it is pretty much just like what will happen if the lid on a pot of boiling water breaks its seal – all the trapped energy comes rushing through and all heck can break loose. Instead of several thunderstorms developing at different times sharing and dissipating all the stored up energy, only one or two storms develop at roughly the same time and develop very quickly, tapping into the large amount of stored up energy… but more on that later.

About the author

Co-operator contributor

Daniel Bezte

Daniel Bezte is a teacher by profession with a BA (Hon.) in geography, specializing in climatology, from the U of W. He operates a computerized weather station near Birds Hill Park.

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