Greetings everyone,
Welcome to yet another approaching Summer season, but what is possibly to be expected? As we all know, weather plays a highly important role in having safe and successful fireworks displays, and so it is necessary to pay attention to atmospheric conditions and report them - I'll get to what should be focused on a little later. In any case, first, let me say that this Spring has, so far, been incredibly disappointing, where we had long spells of cool weather (even during mainly sunny days), frost, as well as enduring periods of rainfall. Though this has been the common trend across most of Eastern Canada, Western Canada was dealing with Winter-like weather for most of the month of May, where large amounts of accumulating snow (yes, snow), sleet, freezing rain and obviously well below average monthly temperatures were observed in many regions. Though the West has improved over the last week, temperatures are expected to cool down and balance off with the East as we get into June. Therefore, I feel this unseasonably cool and unsettled trend may, overall, linger on for a little while longer throughout most of Canada before we see more consistent Summer weather. It is actually a possibility that this won’t occur until around mid-June, so I can’t really offer any positive news until around then.

I have prepared an analysis that may help to explain this trend.
It is to my belief that the recent and persistent La Nina that was present during the Winter, while dwindling for most of Spring, is likely the primary force governing the overall dismal conditions we’ve witnessed this season. Cool sea-surface temperatures (SSTs) seen off of the Eastern equatorial Pacific are likely suppressing any significant warming, even in many parts of the U.S. Atmospheric circulation patterns are responding accordingly. If you examine synoptic weather maps throughout May, the polar jet stream has been, on average, following a fairly zonal, or latitudinal pattern, and so undulations in the form of amplified ridges (which usually flood in nice warm weather) were seldom present. In addition, the jet stream has been often located more towards the South than usual, which ultimately prevents warm moist air from circulating further North – hence the lack of consistent South to Southwesterlies in Eastern Canada. As such, I would theorize, then, that these average jet stream configurations and the subsequent delay in consistent warmer temperatures across the nation are likely the result of a temperature lagging effect in response to the current slowly changing SSTs in the Eastern equatorial Pacific moving towards a neutral state from the last La Nina.
Despite all this, I am still firmly holding onto the prediction that I stated earlier (in the Thunderstorm vs. Fireworks thread), where we should see a normal to slightly above normal Summer in terms of temperature, particularly in July. However, we'll have to be a little more patient for Summer-like conditions due to a possible temperature response lagging behind changing Pacific SSTs. Remember, though, that Summer doesn't officially start until the 21st of June.

Precipitation itself should follow a similar trend, and, again, I’m still expecting fair activity in terms of thunderstorms this Summer, a few of which could reach strong to severe criteria (the average being 1-3 severe t-storms in Montreal per Spring-Summer). Both April and May have followed the precipitation forecast well in terms of being above normal, particularly May, though it is clear that May has been below the average with respect to temperature – our monthly average for May 2009 was barely 17 Celsius (this is cooler than even May 2000 and comparable to May 1997), and the norm is averaged at 19.5 C. Interestingly, this year, so far, has had a history of possessing a relatively large number of windy days, too.
So that’s the breakdown. To sum it up, a normal to slightly above normal Summer (similar to last year) should be in store for us in terms of both precipitation and temperature, mainly because of predominantly “neutral” conditions as well as a slowly building El Nino in the Eastern Pacific. El Nino should continue to develop into the Summer and Fall and persist for the months thereafter, meaning that we may be in for milder weather this coming Winter as compared to the last two harsh ones. With this sort of setup, I believe hurricane season will be fairly active as well – a tropical depression (Tropical Depression 1) recently developed in the Atlantic, even though the season doesn’t officially start until today, June 1st. A developing El Nino, however, may suppress high frequency down the line.
Other than that, I’m hoping for nice cooperating weather for the 2009 fireworks season. Please feel free to report any weather conditions in this topic as we approach fireworks days. However, as always, I recommend waiting at least 2-3 days in advance to make any statements, as things usually become increasingly uncertain any earlier (some exceptions, of course), especially in Summer. It’s always a good idea to report mainly wind speed and direction (remember that light Westerlies coupled with high moisture content is the worst combination for people viewing from La Ronde), precipitation if any, as well as humidity levels. Forecasting thunderstorms can often be trickier, but it’s always good to report the risk, especially for strong to severe t-storms. Finally, it’s also handy to keep an eye on the forecast during setup days. That said, again, I’m sincerely hoping for a perfect weather record this year, much like what was seen in 2004 for the 20th anniversary. Should bad weather affect any fireworks days, though, I’m sure that our 10:00 p.m. “weather barrier” will kick in, as it commonly does.
Trav.
