As I pointed out in the last article, instead of zeroing in on the main culprit of severe summer weather — the thunderstorm — I am going to look at each type of weather warning and outline just what type of weather pattern brings about the best chance of experiencing that warning.
The first type of weather warning listed in my last article was the dust storm. Now, I live in the eastern part of Manitoba where there are a few more trees, and thinking back, I only remember hearing about this type of warning once or twice. Maybe out west this is a little more common, but overall, we rarely see this type of warning. (On a side note, I sure hope talking about this now isn’t an omen for the summer to come!)
When you think about it, a dust storm only needs two things, wind and dry open soil. Open soil is most likely to occur in the spring before vegetation has a chance to grow. We can also see open fields in summer if there are drought conditions, or in the fall after harvest.
Most often the best conditions for blowing dust occur in the spring right around the time when plowing begins. In spring, fields tend to have enough moisture from snowmelt to prevent blowing dust, but they can quickly dry out.
This leads us to the second ingredient — wind. In order to have consistently dry weather we usually have high pressure dominating our weather, which normally results in light winds. Sunny weather and light winds make for good drying conditions, but where will we get the strong winds necessary to create a dust storm? From a weather point of view, consistent high pressure usually means that the overall weather pattern is blocked up, preventing the normal progression of weather systems. This can result in the development of extreme jet stream patterns. These patterns allow for the creation of large temperature differences, so that when the systems finally break down and areas of low and high pressure move on, we can get very strong systems with unusually high wind speeds.
Over the last couple of years we have seen more than our fair share of these types of systems, but even then we’ve only experienced one or two blowing dust warnings. That is because sustained high wind events do not happen that often, and to get blowing dust you need the winds to occur when the conditions are just right in the fields. Personally, I hope that we don’t have to deal with any blowing dust warnings this year.
The next topic is to look back at what April brought us and then look ahead to see what the next four to six weeks might have in store.
April was an interesting month weather-wise across Alberta. After experiencing a March with temperatures a good 4.5 C above average, Alberta saw things cool down a bit in April. The southern region (represented by Calgary) and the northeastern region (represented by Peace River) recorded a mean monthly April temperature that was about 1.5 C above average. Meanwhile, the central region (represented by Edmonton) recorded temperatures that came in right around average.
The pattern of precipitation differed a bit relative to that of temperature. Southern and central regions reported between 10 and 15 millimetres of precipitation, or about 15 millimetres below their long-term averages for April. In the Peace River region, it was a little wetter with around 20 millimetres of precipitation, — right around the long-term average. Overall, April was a little warmer, and with the exception of the northern regions, drier than average.
So what do the weather models predict for the next couple of months?
Environment Canada is calling for above-average temperatures to continue, with conditions becoming wetter as the spring moves on. The Old Farmer’s Almanac is calling for near-average temperatures, along with below-average amounts of rainfall. The folks over at the Canadian Farmers’ Almanac seem to be calling for a mixed bag, with several mentions of fair weather along with unsettled conditions. I figure this indicates near-average temperatures along with near- to above-average amounts of rain.
Finally, my forecast is a tough one as I see almost equal chances of well-above-average temperatures with dry conditions or cool and wet conditions! All of this will depend on the position and strength of the persistent ridge of high pressure that has been dominating the western region over the last year or two. Only time will tell.