Usually around this time of the year I start my annual look at severe summer weather, but before we dive into that topic, the global March temperatures are in and the planet has beat another record. March 2015, according to the U.S. National Oceanic and Atmospheric Administration (NOAA), was the warmest March since records began in 1880. It was the third-warmest March, according to NASA, and the lower atmosphere recorded the fifth-warmest March in the 37-year satellite record, according to the University of Alabama Huntsville.
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.
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.