Edmonton was the hot spot with a mean monthly temperature of 18.6 C, which was about 2.5 C above average. Calgary came in second with a temperature of 18.2 C, about 1.7 C warmer than average. The Peace River region was not far behind with a mean monthly temperature of 17.6 C, about 1.3 C warmer than average.

The area from Edmonton northward saw near to above average rainfall in July. Both Edmonton and Peace River reported around 90 millimetres of rain, which was near average for Edmonton and about 20 mm above average for Peace River.

The southern half of the province was drier, with some regions seeing near average rainfall while other were a little below average. Calgary reported around 40 mm of rain, which was about 20 mm below average.

As for the latest outlooks for September, the Old Farmer’s Almanac predicts average temperatures along with above average rainfall. The Canadian Farmers’ Almanac calls for near to below average temperatures as it mentions “chilly” weather near the end of the month. Its precipitation forecast also calls for above average amounts.

NOAA calls for near to above average temperatures with near average precipitation. The CFS model forecasts near average temperatures and above average precipitation. The CanSIP’s forecast is for above average temperatures and precipitation.

Last on the list of weather models is the ECMWF or European model, and its forecast is for September to be near average for both temperature and precipitation.

Patterns of wreckage

Now let’s discuss straight line winds. While most of us know tornadoes can produce the most powerful winds on earth and can be truly awe inspiring, not many of us will experience one. But I can pretty much guarantee that, if you live on the Prairies, you will experience a thunderstorm that produces very strong straight-line winds. Sometimes these winds can be so strong and devastating that their damage is attributed to a tornado, and the only way to determine cause is to look at the pattern of damage.

With tornadoes, the damage will be more random, with trees and objects broken and thrown in different directions due to the swirling air. With straight line winds, nearly all damage is in one direction.

Nearly all straight-line winds, or at least the really damaging ones, occur near the leading edge of a thunderstorm. Thunderstorms are made up of updrafts and downdrafts. Air moves upward due to either being warmer than the air around it or by being forced upward as horizontally moving air is deflected by something like a cold front. Downdrafts are a little more difficult to understand.

When a thunderstorm is moving in, we often get that first big blast of wind that causes everyone to run for shelter and announces the arrival of the storm. There are two main reasons for these winds.

First, all the air rising to the top of the storm has to go somewhere. In a strong storm, an overhead jet stream vents away this air but often not all of it is vented. Eventually the built up air becomes big enough, or the updraft weakens, and that air falls toward the ground.

Combine this falling air with the rain that is also falling. As the rain falls, it pushes on the air around it, much like a big waterfall. This downward moving air hits the ground and then has to flow somewhere.

The area of falling rain acts like a wall, preventing much of the falling air from flowing back into the storm, so instead, this air is funneled or pushed in front of the storm. These downbursts can be short-lived or they can continue for long distances as the thunderstorm travels.

Long-lived events are known as derechos, though they are not common in Canada. Peak wind speeds in these downbursts can routinely hit over 100 km/h with gusts at over 200 km/h.

The worst derecho on record in Canada occurred last May in southern Ontario and Quebec. Winds speeds were recorded as high as 190 km/h along a path that extended for nearly 1,000 km and took nearly nine hours to play out.

Damages exceeded $750 million, making it the sixth most costly weather disaster on record. Sadly, 12 people were killed, mostly from falling trees.

In front of a thunderstorm is not the only place were strong straight-line winds can occur. Often, we can get very strong winds in the middle of the storm. One reason is the jet stream or strong upper-level winds.

Strong thunderstorms often need strong upper-level winds to help vent the rising air. Occasionally, these winds get caught in a strong downdraft and are deflected toward the surface. If they make it all the way to the surface, they spread out and flow in several directions depending on the angle.

This type of straight-line wind can be confused with a tornado because they often seem more chaotic than winds that precede a thunderstorm.

The post Thunderstorms and straight-line winds appeared first on Alberta Farmer Express.

Thunderstorms can bring a wide variety of severe weather with them: heavy rains, hail, high winds, lightning, and, on some occasions, tornadoes.

After an extended period of dry weather across large portions of southern and central Alberta, an upper-level low brought significant rains to almost all areas. This leads nicely into this issue’s topic of severe summer weather and heavy rainfall.

While we do not necessarily need thunderstorms to bring heavy rain, generally, most of our really big rainfalls are associated with them. As you probably already know, warm air can hold a lot more moisture than cold air. At -20 C, the air can hold about 1.0 gram of water for every cubic metre. At 0 C, that increases to around 5.0 grams, at 20 C it is around 17 grams, and it jumps all the way up to 30 grams per cubic metre at 30 C.

This would mean that a storm system forming on a hot summer day may have up to six times as much water to work with as one that formed at near-zero temperatures.

We also have to remember that the atmosphere is vertical, with heights during the thunderstorm season typically reaching 10,000 metres.

While the amount of moisture within this column of air is not vertically uniform, we can still make some back-of-the-envelope calculations to get an idea of just how much water can be available in the atmosphere to form rain.

Let’s say that in a really moist atmosphere about one-quarter of a one metre by one metre by 10,000-metre column of air is close to having 100 per cent humidity, and that the average air temperature of this part of the column is about 20 C. That would mean that each cubic metre of air would have about 17 grams of water, but let’s say 15 grams just to make the math a little easier.

So the column of air would have around 10,000 x one-quarter x 15 grams of water or 37,500 grams. One gram of water is roughly equivalent to one cubic centimetre (cm3). So this column of air would have about 37,500 cm3 of water or 37.5 litres.

If all this moisture could fall out of the column of air that would equal about 37.5 millimetres of rainfall.

Now these calculations are just hypothetical, but it gives you a bit of an idea as to just how much water can be in the atmosphere above our heads.

Meteorologists calculate this figure, and it is referred to as precipitable water or PWAT. The amount of PWAT varies greatly from place to place, time of year, and type of air mass that is in place. Take the storm system that brought all the rain in the middle of June — the moisture in the atmosphere was thick, with a good part of the atmosphere being close to saturated. This resulted in PWAT values that were in the 30- to 40-millimetre range.

So these warm-season storms can have a lot of water to work with. Yet if a thunderstorm was just dealing with the amount of water in the air within the thunderstorm itself, then we would not actually see any huge rainfalls.

If all the water in a column of air was condensed out, the most precipitation we would typically see in our region is about 50 millimetres. So how can we get storms that dump more than this, sometimes as much as 100 to even 250 millimetres? The answer is — the horizontal movement of air.

If you watch the flow of air across our planet you will see how storm systems can tap into huge flows of air that can literally cover thousands of square kilometres. This means that as a storm is condensing out the moisture available for rainfall, new moisture is moving in to replace that moisture, allowing rainfall amounts to really ramp up.

In thunderstorms, the movement of the storm and its short life cycle will put a limit on just how much rain can fall. But sometimes thunderstorms will stall over a region, allowing for some truly extreme rainfall events.

At other times, we can get something called thunderstorm training. This is when a series of thunderstorms form in the same general area and follow each other, one after another, bringing several rounds of heavy rainfall.

Just what is considered heavy rainfall across our region?

According to Environment Canada, a short-duration summer rainfall warning will be issued if 50 millimetres of rain or more is expected within a one-hour period — usually caused by thunderstorms. Whereas a long-duration rainfall warning will be issued if 50 millimetres or more is expected to fall within a 24-hour period or if 75 millimetres or more is expected to fall within 48 hours. This is usually the result of a slow-moving area of low pressure, though this could also be related to several rounds of heavy thunderstorms.

We will continue our look at severe summer weather by looking at high winds and hail in the next few issues.

The post Heavy rain — where does all that water come from? appeared first on Alberta Farmer Express.

After a very active summer last year, I thought it might be time to look at this topic again. I also thought it would be a good idea to take a more detailed look at the topic this year.

With that in mind, I am going to start with the basics: What happens when solar energy is absorbed and how does this energy eventually result in the development of thunderstorms?

When solar energy is absorbed by an object, the molecules in that object are excited, which causes them to vibrate quicker. The faster they vibrate the warmer the object. So it is fairly apparent why objects will get warm, but now the question is: How does this heat energy get transferred from the object to the atmosphere? The answer lies within four different processes — conduction, convection, advection, and latent heat transfer.

Conduction is the simplest process to understand as it is the transfer of energy from one molecule to the next. As solar energy strikes a surface, the molecules in that object gain energy and they begin to vibrate faster and faster — the object warms up. If you were to put your hand on that object, the molecules on the surface of the object would be vibrating next to the molecules on your hand and some of that energy would be passed onto the molecules in your hand.

Now because the molecules in your hand are vibrating faster, your hand will begin to feel warm. This is conduction of heat.

When we are looking at the Earth, solar energy striking its surface causes the molecules to vibrate and heat up. The molecules in the air immediately over the ground surface begin to vibrate faster too as they come into contact with molecules in the ground and thus the air heats up. This process will only be able to heat about the bottom two centimetres of the atmosphere, so now the question is: How does this heat get transferred throughout the atmosphere? You guessed it — this is where convection, advection, and latent heat transfer come in.

Basically, convection and advection are very similar. They both refer to the physical mixing of the atmosphere. Convection is when the mixing occurs primarily in a vertical direction and advection is when it is occurring in a primarily horizontal direction. How convection takes place has to do with density and the fact that less dense objects are more buoyant.

When part of the atmosphere is heated through conduction, the molecules are vibrating faster and that faster motion also means they need more space around them. Taking up more space means there will be fewer molecules in a given area. Since density is calculated by dividing mass by volume, fewer molecules (less mass) in a given volume of air would result in a lower density of that air. Since the air is now less dense than the air above it, that air will begin to rise, taking heat energy from the surface of the Earth and moving it into the atmosphere. Once this heat energy is in the atmosphere, currents of air (wind) can move the heat horizontally from one area to another. This is known as advection.

The final process for moving heat energy around is by latent heat transfer. The term ‘latent’ means that something potentially exists, but is not currently in existence or realized. In latent heat, we have heat that exists, but is not actually present yet as heat.

So how does this work?

It has to do with water and the fact that it takes heat energy to turn water from a liquid to gas. As water absorbs solar energy, the molecules get excited and vibrate faster and faster. Eventually, the molecules at the surface of the water droplet will vibrate fast enough to break free from the rest of the water molecules and float away — they are now a gas. What is interesting is the heat energy it took to cause the liquid water molecule to become gas molecules is still contained within those gas molecules — the potential energy is there.

The gaseous water molecules float away from where they acquired their heat energy and at some point begin to lose some of their energy and cool down. As they cool, they eventually condense back into liquid water, and at that point, release all of the heat energy they absorbed to become a gas (or evaporate) in the first place.

Since it takes a lot of heat to evaporate water, it releases a lot of heat when it condenses. This is one of the main driving forces behind the major storm systems that we see, and plays a huge factor in the development of thunderstorms.

We’ll explore this more in future articles as we continue our annual look at thunderstorms.

The post Weather school is back in session — here are the basics of thunderstorms appeared first on Alberta Farmer Express.

A classic definition of a tornado is a violently rotating column of air that extends from a thunderstorm to the ground, which may or may not be visible as a funnel cloud. For this rotating column of air to be classified as a tornado, it must touch the ground.

• More with Daniel Bezte on the Alberta Farmer: Spot the warning signs of a tornado

As to how tornadoes form, the real answer is: We just don’t know.

Tornadoes usually develop from supercell thunderstorms, but these are difficult to predict. Even if we were able to accurately predict where and when these thunderstorms would develop, the intense part of the thunderstorm usually only covers an area of a few hundred square kilometres. Within this few hundred square kilometres, the really severe weather may only occur in a small area of maybe 10 to 20 square kilometres. Now, if we look at the size of a tornado, we would find that they range from as small as about 40 metres to as large as two kilometres across, with the average width being around 100 to 200 metres. This means that, as far as weather phenomena are concerned, tornadoes are very small, which makes them difficult to study.

Now, before I go on to look at tornadoes in more detail, let’s first take a look at one of the weakest members of the tornado family — the funnel cloud, and in particular, something called a cold-air funnel.

The fundamentals behind the development of these funnel clouds are very similar to how tornadoes get started and will serve as a good starting point for our look at tornadoes.

All tornadoes develop out of what we refer to as a funnel cloud. In strong thunderstorms, these funnels elongate and may eventually touch the ground to become a tornado, but a funnel cloud all by itself is not considered a tornado. While a fair bit of research has been done on tornadoes and the storms that produce them, very little research has been done on cold-air funnels and so we know very little about them.

In general, cold-air funnels form in environments where we would not typically expect severe weather to develop, that is, in hot, muggy, unstable air. Usually, cold-air funnels will form when there is a large pool of cold air aloft that is most often associated with an upper-level low. These conditions provide two critical ingredients that are believed to be necessary for the development of cold-air funnels — instability and vorticity.

If you think back to what you know about instability in the atmosphere, you should remember that warm air will rise and cold air will sink. If the atmosphere is unstable you need either really warm air at the surface, or very cold air in the upper atmosphere. This is why there needs to be a pool of cold air aloft for cold-air funnels to form, because this provides the first ingredient — instability, or rising air.

The second ingredient is vorticity. This simply means spinning air. Areas of low pressure are large areas of spinning air, too large to form into a funnel cloud or tornado. But within this large area of spinning air, smaller regions get ‘spun up’ creating what meteorologists call a vorticity-rich environment, which contain lots of little eddies of spinning air. Scientists believe one of these small eddies of spinning air gets caught in an updraft. This updraft then pulls on and elongates the eddy, causing it to contract in width. And just like a figure skater pulling their arms in during a spin, this causes the rotation to gain momentum, creating a funnel cloud.

These funnel clouds are generally very weak and short lived, and will rarely become strong enough or last long enough to touch down. If they do touch down, they can then be referred to as tornadoes, but even then they rarely cause much damage, often comparable to that of a very strong dust devil. In fact, when these cold-air funnels do touch down they are sometimes referred to as land spouts.

Since the potential exists for cold-air funnels to touch down as a tornado, Environment Canada has to issue special weather statements to warn the public about them. Since they rarely touch down, and even when they do they rarely cause damage, such statements will usually urge the public to be watchful for these to occur and to take precautions if necessary. So you don’t have to go diving for the nearest storm shelter if you do see one of them forming.

We’ll continue our discussion on more severe tornadoes and straight-line winds next time.

The post Severe summer weather. Taking a look at thunderstorms and wind appeared first on Alberta Farmer Express.

There are a lot of questions about this subject, and little information available. That’s why the team at Farming Smarter developed its own hail damage simulation machine, which it unveiled at the organization’s recent field school.

“We wanted to do this so we could test management practices that could be considered crop recovery attempts for hail,” said general manager Ken Coles. “You have this crop that you’ve invested in, and when it gets beat up, you want to give it some medicine to help it along.”

The team at Farming Smarter had many farmers coming to it with questions about hail recovery products, and found a lack of scientific data on how crops recover from hail.

Questions abound

Hailstorms cause crop tissue damage, stem breaks, bruising, scraping, and leaf defoliation. When hail crushes a mature crop, it often wipes it out. But an early crop can recover and so it’s difficult to assess the damage, said Ian Wood, an adjuster with the Agricultural Financial Services Corporation.

Typically a sample of 100 plants is used to assess what percentage was damaged. Adjusters will often wait for about 10 days before they come out for an assessment, so they can see how much of the crop has actually died.

But the survivors can be in for a rough ride. For example, open wounds on a plant can become a vector for disease, allowing it to be attacked by opportunistic pathogens.

“There’s a lot of talk about whether or not hail causes disease or contributes to disease,” said Rod Werezuk, a research technologist with Alberta Innovates Technology Futures in Vegreville. Werezuk has been simulating hail damage on crops for research purposes for four years. It’s an area that hasn’t seen a lot of study, but that hasn’t stopped claims being made for so-called ‘hail recovery’ products. Farming Smarter will be testing these products as well as regular fungicides, nutrient blends, and growth regulators on plots with simulated hail damage.

“Most people like to talk about rescue attempts, but most people don’t know what’s going to work,” said Werezuk, who works mainly with plant pathology. “Although hail damage has been simulated in research for a couple of decades now, we’re still left with these questions.”

Simulating hail damage

In a real-life situation, hail damage is uneven, which makes it difficult to study. So researchers used controlled trials that can be reproduced, which allow both scientists and adjusters to gather accurate data. All treatments applied to damaged plots are applied to uninjured check plots as well, so the true effects of the treatments can be studied.

After consulting with members of Alberta Innovates Technology Futures in Vegreville, the staff at Farming Smarter simulated hail damage by whipping test plots with dog chains. A local company, Kirchner Machine, custom built a hail damage simulator that can be attached to a front-end loader for larger plots. The simulator consists of a bar covered in dog chains which whips the crops to simulate heavy hail damage.

For the purpose of the study, test plots will be damaged at various levels and different growth stages. Crops in the study, funded by the Alberta Pulse Growers, include fababeans, dry beans, peas, wheat and canola.

“We can also play with the timing of the application and the treatment,” said Coles.

Being able to conduct controlled studies next to check plots will shine a light on what works, he said.

“We hope that in creating the simulator, we’ll be able to test some of these products and get some more funders on board,” said Coles.

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I was going to take a break from our examination of severe summer weather for this issue and examine some of the unique weather events that have taken place across the world over the last month or two. But I think the timing is just right to begin our look at the most prevalent of severe summer weather — thunderstorms and the hail they can bring.

First of all, when it comes to thunderstorms, we need to clarify something right off the top. I have discussed this several times in the past, and I know everyone doesn’t read my articles. But it still makes me crazy when I hear people getting all worked up about a severe thunderstorm watch and then being upset about how inaccurate the forecast was when no thunderstorm happened. A severe thunderstorm watch is when conditions are favourable for severe thunderstorms to take place. It does not mean that severe storms have formed and will hit your area — when that happens, a severe thunderstorm warning is issued.

• More with Daniel Bezte: Know your weather alerts before severe summer weather hits

Severe thunderstorms can bring almost all of the major types of severe summer weather, but one of the most devastating is hail. While tornadoes usually get most of the attention, and they can be truly devastating, they are rare. Just ask around — very few people have ever seen, never mind felt, the full impact of a tornado. I know I have never experienced one. Ask the same question about hail and pretty much everyone will have a story about a big hailstorm, or two… or three!

Unless the hail occurs in March or early April, I don’t think there is a single farmer or gardener who thinks hail is neat or cool. I used to be one of those who loved hail — until I owned my own car, house, and had a vegetable garden!

Just how often can you expect to see hail across the Prairies?

Over most of the Prairies it would be one to three times a year. There are hot spots that can see hail upwards of five times per year and they are in south-central Alberta, extreme southern Saskatchewan, and south-central Manitoba.

By far the most active area is in south-central Alberta, and in particular, Calgary. Looking at the most expensive hailstorms across Canada the vast majority has occurred in Alberta, with a few bad ones in Manitoba. Looking at the dates for the most destructive hailstorms and we find that with only a few exceptions, all occurred in July.

The big question is: Why does Alberta in particular, and then southern Manitoba, see so many bad or damaging hailstorms compared to the rest of the country? Well, for Alberta it has to do with topography (or the lay of the land), whereas in Manitoba it has more to do with its closer proximity to Gulf moisture that can help to fuel really big storms.

Hail forms when a particle passes from the warm (liquid) part of the cloud into the cold (freezing) part of the cloud. When this occurs, any water on the particle freezes and you now have a small hailstone. Most thunderstorms produce hail, the question is whether or not the temperatures in the storm and the updraft are such that the hailstones will make it to the ground before they melt. If a hailstone forms and just keeps going up to the top of the thunderstorm it wouldn’t accumulate much ice and will remain small. For hailstones to get really big they must go back into the warm (liquid) section of the storm, pick up more water, then go back up into the cold section of the cloud so the water can freeze. Repeat this cycle a number of times and you can get some really big hailstones.

In Alberta, the higher terrain allows for lower freezing levels in the atmosphere, which means hailstones don’t have much chance of melting on their way down — so they can be fairly large. In Manitoba, the deep Gulf moisture allows storms to get very high with strong updrafts, which can keep hailstones aloft for long periods of time, allowing large ones to develop.

When it comes to hail, size really does matter! Pea-sized hail will do little, if any, damage to structures and plants, while golf ball-sized ones can literally destroy everything in their path.

When it comes to measuring hailstone size, things become a little strange. That is, you don’t usually hear that the hail will be around 50 millimetres in diameter. Instead, you hear that the hail was the size of a golf ball or an egg. Of all the things we measure in regards to weather, hail has by far the most descriptive measurements. Some of the more common descriptive terms used for hail and the approximate size of hailstones are:

• Pea – 5 mm in diameter
• Marble – 10 mm in diameter
• Grape – 15 mm in diameter
• Ping-pong ball – 40 mm in diameter
• Golf ball – 45 mm in diameter
• Egg – 50 mm in diameter
• Pool ball – 60 mm in diameter
• Tennis ball – 65 mm in diameter
• Baseball – 70 mm in diameter
• Grapefruit – 100 mm in diameter
• Softball – 115 mm in diameter

In the next issue I think we’ll take that break from severe summer weather to explore some of the unique weather happenings from around the world.

The post When it comes to hail, not all parts of the Prairies are equal appeared first on Alberta Farmer Express.

According to the Weather Underground, the NASA database showed March 2015 as having the fifth-greatest departure from average and so far we have seen five of the top 10 monthly departures from average occur over the last year. In NOAA’s data, the last 12 months have been the warmest 12-month period on record, with seven of the past 11 months tying or setting a global monthly record. Personally, I am still sticking to my opinion that the cool pattern that has been keeping eastern North America below average will continue to slowly shift eastward, setting the stage for a very warm late spring and summer across central North America.

Alert Ready

OK, now on to this issue’s topic: severe summer weather. It seems appropriate to start this off by talking about the federal government’s recent announcement about a new emergency alert system, Alert Ready. It is basically a distribution infrastructure that will allow for the rapid dissemination of information about imminent danger coming from any source. The technology for this new system has been in place for years and was voluntary, but as of March 31, it now has to be used by all broadcasters. Check out alertready.ca for more information.

When it comes to severe summer weather, or any severe weather, there are three levels of alert. Knowing these levels and what they mean is the first step to keeping yourself informed and safe. Personally, it drives me crazy when I hear people talking about different alerts, because often they get them all mixed up!

The first level is a special weather statement. These are issued when unusual weather is expected to develop, but isn’t expected to meet or exceed severe weather levels. This type of alert means the weather will likely affect your day, but probably won’t cause a serious disruption to your daily routine.

The next level is a weather watch. This means severe weather conditions have not yet developed, but forecasters feel there is a good chance that they will develop. This is the one most people get mixed up. When a watch is issued, it means you should pay attention to the weather around you and keep an eye on the weather around you. You should keep track of weather reports and other online weather sources. Be prepared to take safety precautions and to take action quickly should severe weather develop and a warning is issued.

You guessed it: the final level is a weather warning. This means severe weather has developed and is occurring. When dealing with severe summer weather, warnings can sometimes be issued in advance, but due to the nature of summer severe weather the lead time is often very short, sometimes giving you only a few minutes. This is why you need to be paying attention when there is a weather watch issued. If you hear of a warning for your area, take action immediately.

What’s severe here?

So, what kind of severe summer weather affects our region of the world? The table here shows Environment Canada’s list of the different weather warnings we could see across the Prairies during the summer, along with brief descriptions.

This year I’m going to take a little bit of a different slant on examining these conditions. While we will still take a closer look at the main severe weather culprit, thunderstorms, I am going to take a wider view by examining the weather pattern and conditions needed for these seven different types of warnings to develop. So stay tuned, and let’s hope that severe summer weather holds off for a little while yet!

• Dust storm — Blowing dust reducing visibility to less than 800 metres for more than one hour.
• Heat — Temperature or humidex values expected to reach 40 C.
• Rainfall (short duration) — 50 mm or more rain is expected to fall within one hour.
• Rainfall (long duration) — 50 mm or more rain is expected in 24 hours or 75 mm or more in 48 hours.
• Severe thunderstorm — One or more of the following conditions is imminent or occurring: Wind gusts of greater than 90 km/h; hail two centimetres in diameter; heavy rainfall as per rainfall criteria.
• Tornado — A tornado has been reported or there is evidence on radar of a tornado.
• Wind — Sustained winds of 70 km/h or more, and/or gusts to 90 km/h or more.

The post Beginning our look at severe summer weather appeared first on Alberta Farmer Express.