How does the saying/ song go? “Rain, rain, go away, come again another day.” I think for a lot of people across at least the southern third of the Prairies, “another day” could be a month from now. Farther north, conditions are almost the exact opposite. Months of dry weather have left things extremely dry. So just what the heck is going on this year? This is the question I have been emailed about the most over the last couple of weeks. Exactly why we’re in this pattern I can’t really answer, but I can make an attempt to explain what’s going on. I know that won’t help if you are staring at water-soaked fields or bone-dry ones, but for some of us, understanding what’s going on seems to help, at least a little.
Most of us have heard of the jet stream. I have discussed it in several different articles over the last few years.Jet streamsare high-altitude rivers of fast-moving air that usually occupy the space between two different air masses. Typically, in the Northern Hemisphere during the summer, we have two main jet streams, the arctic jet and the subtropical jet. The arctic jet occupies the space between the cold arctic air and the warmer mid-latitude air masses (our typical summer air mass). The subtropical jet stream occupies the space between our mid-latitude air mass and the hot, humid tropical summer air mass.
HEAT AROUND US
OK, so far so good. Usually in the summer, the difference in temperatures between these three main temperature regions is at its lowest. This results in fairly weak jet streams, at least compared to winter. This year we’ve been seeing some fairly strong jet streams. With it still being fairly cold up north and with record heat building to our south, I guess this is not that surprising. Oh, yeah, I forgot to mention there is heat around us. Over the southern and central United States and over eastern regions of North America there have already been some serious heat waves. Several cities in Texas broke not only daytime-high records with readings of over 100 F (38 C), but for a number of places it was the earliest that they have broken these 100 F records. The heat was as close to us as Minneapolis, where on June 7 they hit 103 F (39.4 C), which was their hottest day in 23 years!
So, there is a lot of heat just to our south, but the questions still remain: why isn’t
it making its way into our region, and why all the rain? Back to our look at the jet streams. Currently, the arctic jet is basically where it should be, well to our north, cutting across the far northern Prairies and into the southern territories. This jet is tracking systems across this region and keeping the cold air up north – for the most part. The southern jet, or subtropical jet, has been unusually active so far this year. This is allowing storm systems to become unusually strong. Combine this with all the warm, moist air pushing north into these storm systems and we get rain, lots of rain. But why are we only seeing it across southern regions?
This has to do with an area of high pressure that has been dominating the weather over the central and northern
Prairies. This region of high pressure is putting a pinch on all the stormy, wet weather to the south. As these systems develop over the western U.S. and begin to push north, they deepen, due to the strength of the jet stream and the particular path it is taking over North America. All the moisture from these storms is being dumped on the northern parts of the U.S. along with the southern parts of Canada. As the storm systems push to the northeast, the dominant area of high pressure keeps the central parts of the Prairies high and dry.
RAIN FARTHER NORTH
The other interesting part of this particular pattern is that, as these storm systems get really wound up, they are influencing the weather patterns over a very large area. As they push to the northeast they are pulling down the arctic jet, giving us these short blasts of cool weather every time one of these systems pulls away.
The final question is, when will it all end? If I knew that, I’d be rich. Looking at the current weather models it appears to be a good news/ bad news forecast. The models show the main storm track will push northward. This will hopefully bring more rain to the dry regions. The bad news is that the general pattern of unsettled weather looks like it will be with us for at least the next couple of weeks. I know that’s not what a lot of you want to hear, but I have a sneaking suspicion that by the end of August we may be regretting our wish for hot, dry weather.
Asthestormsystemspushtothenortheast, thedominantareaofhighpressurekeepsthe centralpartsofthePrairieshighanddry.