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 Montreal Fireworks Forum —› General —› Weather Cooperation (or not) for Summer 2016.
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Posted: Jul 25, 2016 12:06:18   Edited by: Smoke

Very nice photos! Thank you for sharing these, Fred and ryguy2008.

It was a rare situation where I found it necessary to disagree with model data and go more with instincts (it is usually a combination of using the two). During the day, the wind flow was virtually opposite of projections given by "all" models, and there was really no sign of this changing into the evening. This may have been due to the thunderstorms in the area earlier that altered the general wind flow locally. It was only until about 11:00 p.m. that winds started to become more NW in the area.

And indeed, convective rain showers were persisting until between dinner time and sunset before more completely subsiding. With the timing of this rain shower, it increased the possibility of seeing a defined rainbow once the sun came out (since the sun was lower in the sky at the time, and given the size of the individual drops, as shown in Fred's photo), and once the cloud was at a far enough distance relative to observers as it departed.


Posted: Jul 26, 2016 00:32:11

Another area of low pressure is expected to affect S. Ontario to S. Quebec through mid-week this week, including on the day Wednesday (July 27th). This system will help re-circulate tropical weather back into these regions, with maximum temperatures reaching 31-33 C ubiquitously, coupled with moderate humidity, inducing humidex values of 34-35 C. By evening, humidity increases to high, and with temperatures remaining as warm as 28-29 C in the greater Montreal area at the time, a humidex of 35 C is favorable. During the day, however, a weak cold front is expected to advance southeastward and, with moderate instability present, provide some lift for sparsely distributed convective rain showers and non-severe thunderstorms (30% probability). The lack of stronger thunderstorms, despite hot temperatures, is more so due to overall weak lift along the front and somewhat restricted low-level moisture early in the forecast period. This front should eject farther SE of the regions in time for the early-evening, so the rainfall threat should diminish during the time, especially after sunset. Skies should be mostly sunny, but becoming more partly cloudy by afternoon and evening (large and vertically defined cumulus clusters and high-level cirrus) There is some uncertainty in the timing of the front, though, so this will have to be monitored in coming model data.

Winds are expected to be generally WSW during the day and may persist into the evening, and a shift to a westerly to eventually WNW pattern may unfold in time for the early-evening. Wind speeds are shown to be gusty during the afternoon hours but should weaken in time for the evening period. Speeds during the afternoon are 23-26 km/h (occasional gusts of 37-41 km/h) and then weaken quite sharply to 7-11 km/h (possibly less) by early-evening. This would indicate that winds could be blowing the smoke fairly gently towards the La Ronde audience directly (with more tendency towards central and left-hand sections of the audience). Smoke accumulations could be extensive and frequent due to high humidity developing into the evening period, which would often cause the display to appear murky.

Another update to come by later today (July 26th to early-July 27th).


Posted: Jul 26, 2016 23:33:01

Forecast details mentioned above continue to be applicable for the day tomorrow (July 27th), although some modifications have been made to precipitation probabilities and wind velocity. As such, here are predominant weather conditions that will affect the Montreal area for Wednesday, July 27th:


Temperatures are expected to be hot during the afternoon period, with a maximum of 31-32 C by mid-afternoon. Humidity remains fairly high through the afternoon hours but rises further into the evening period. Temperatures do not fall significantly into the evening (assuming no interference from convective rains or thunderstorms) due to high humidity, so a mid- to late-evening temperature of 28-29 C in the metropolitan area is favored. High humidity will support a humidex of 33-34 C by the mid-evening period (including display time). Note that if convective rain showers and/or thunderstorms do occur persistently, then temperatures will fall to 21-22 C, and moisture/humidity will rise to very high levels.


As mentioned in the previous posting, a weak cold front is expected to slide SE over the course of the day and will affect E. Ontario to extreme S. Quebec by late-afternoon through to the early-evening, although there are now signatures that it could continue to influence these regions until as far as the mid-evening period. Isolated thunderstorms and convective rain showers (30% probability) are possible by mid-afternoon, but convective coverage should become more scattered (40% probability) by late-afternoon to mostly early-evening, as the front draws closer. The weak nature of the front and modest wind shear fields should prevent very scattered to widespread convection, as well as be more supportive of non-severe thunderstorms. However, dynamics do suggest the possibility of sparsely distributed strong thunderstorms (30% probability) by late-afternoon. Convection should diminish more after 9:30 p.m. tomorrow (becoming more isolated in distribution until the early-overnight), but the greatest likelihood for convective development will be from 5:00 p.m. through to sunset. Have an umbrella (or some form of head covering) with you for mostly the early-evening. If no rainfall occurs, expect partly cloudy skies (clusters of vertically defined cumulus clouds from the afternoon, and high-level cirrus clouds).


There remains some uncertainty with the overall wind direction for the evening period, but WSW to SW appears to the predominant scenarios at this point in time. There is more general agreement, however, as to a SW flow throughout the afternoon that should continue into the evening period. This would be much more beneficial for the La Ronde audience. Fortunately, speeds are also more favored to be slightly stronger (11-14 km/h) to clear away fairly rapidly accumulating smoke (mostly along low- to mid-level). As a result, this would suggest that the smoke would be pushing mostly to the right of the La Ronde audience, but also pushing towards extreme right-hand sections of the audience. Smoke from upper-level shells, however, would be moving a little more directly towards right-hand sections of the audience. *Note also that if thunderstorms do occur in the area, the local wind flow will temporarily be altered.

In summary, a typical July evening, with very warm temperatures, high humidity, and light SW winds. Convective rain showers and mostly non-severe thunderstorms (40% probability) will also be possible during the late-afternoon to early-evening.

*Another update to follow tomorrow afternoon (July 27th) to further address wind direction/speed, and the thunderstorm/convective rain risk.


Posted: Jul 27, 2016 18:06:38

The thunderstorm/convective rain shower risk will continue throughout the early-evening, but the best chance for more scattered coverage (40% probability) continues to be late this afternoon through to about sunset. Beyond 9:00 p.m. coverage will likely revert to being more isolated (30% probability). At this point, convection has been most pronounced to the North and NW of the island, and mostly into S. Ontario.

Winds should still be SW by the mid-evening period, given the positioning of the front, so the smoke (at all altitudes) should be moving reasonably quickly towards mostly right-hand to sometimes central sections of the La Ronde audience (notably smoke from high-level shells). Mid- to late-evening temperatures should also be 27-28 C.

All other factors continue to be applicable.


Posted: Jul 28, 2016 23:35:48

A large area of high pressure will likely migrate SE in time for tomorrow (July 29th) and persist for the final weekend of July. This system will play an important role in the development of a possible heat wave to begin August (mostly the August 2nd-August 5th period) as it slides farther SE and positions itself over the Atlantic. Some long-term models are even hinting at a possible unusually hot August 2016.

Under the influence of high pressure, conditions will further stabilize this weekend (including Saturday, July 30th), and so convective initiation will remain minimal and instead give way to pleasant conditions for the next several days. Humidity on Saturday is expected to remain low, but it could become more borderline low to moderate by the mid-evening. Maximum temperatures of 26-27 C are favorable for the mid-afternoon period, and evening temperatures should be a pleasant 23-24 C, with a mild humidex of 25-26 C, in the metropolitan area. Mostly high-level cirrus and a few isolated fair-weather cumulus clouds are favorable, but skies should be largely clear for the day.

Winds will need to be monitored, however, since they may potentially be very light (speeds of 4-7 km/h), with variable directional tendencies, as is common with high pressure systems. At this point, though, very light NNE winds are possible, so, like the opening display, the smoke could be moving very gently towards spectators on the bridge immediately adjacent to La Ronde. Extensive smoke accumulations, however, are not favorable due to lower humidity levels.

*Another update to follow later tomorrow (July 29th), along with subsequent updates on the afternoon of July 30th.


Posted: Jul 29, 2016 13:42:12

Trav, thanks for the amazingly accurate weather forecasts again this year. We've managed a completely dry season! I'm pretty sure it will be the case for tomorrow, too, for the closing!


Posted: Jul 29, 2016 23:18:43

Details specified in the above posting remain, in large part, applicable for tomorrow (July 30th). As such, here are the most likely conditions for the Montreal area for Saturday, July 30th.


Maximum temperatures of 26-27 C are favorable for tomorrow mid-afternoon. Humidity should be on the low side for most of the day, so a humidex is negligible. By the mid- to late-evening, a temperature of 24-25 C is more likely (including display time), and humidity is expected to increase to borderline low-moderate levels, inducing a mild humidex of 26-27 C.


Under the influence of high pressure, mostly clear skies are favorable, and convective rain showers will be kept at a minimum. A few high-level cirrus and very sparsely distributed low-level fair-weather cumulus will likely be present through the day (only patches of high-level cirrus clouds during the evening as the air further stabilizes).


Wind direction will continue to be monitored, but recent and latest data supports very light to occasionally calm winds, as mentioned in the previous posting. Speeds of 3-6 km/h to calm are favorable through the day, but especially by the evening period. Under such conditions, directional tendencies are much more variable locally (due to local influences on the wind becoming more important when speeds are very light). Still, a NNE pattern is likely to be the most overall favorable scenario, causing the smoke to move very, very gently towards spectators on the bridge immediately near La Ronde. Extensive periods of smoke accumulation are very likely (notably during active sections, and along low- to mid-level of the display), but the smoke itself should not be building too excessively (or inheriting a very thick texture) due to lower amounts of humidity. Still, this could very frequently cause the display to appear murky (from all vantage points) with virtually small displacement of smoke accumulations as the display progresses.

In summary, a warm evening, with mostly clear skies, borderline low-moderate humidity, and very light to calm winds.

*Another update concerning wind velocity to come by tomorrow mid-afternoon (July 30th).
Not a problem for the forecasts, Paul! It was definitely a challenging year for overall wind direction, in particular, but yes, we remained dry throughout the season during the 10:00-10:30 p.m. time slot, and I am very confident for the same tomorrow! I think the wind speed could be often problematic tomorrow, though, as speeds could resemble what we witnessed during Switzerland’s display, possibly a touch weaker.


Posted: Jul 30, 2016 11:31:48

At 11:30am, La Ronde website already indicates that the parking is reaching capacity. (Of course, Osheaga doesn't help.)

It's the peak of the vacation season, the last opportunity to see a fireworks at La Ronde and perfect weather conditions: all ingredients are mixed for the most crowded day of the year at La Ronde. Don't arrive late, you may be jammed in the traffic!


Posted: Jul 30, 2016 18:13:01

Latest runs continue to suggest very light to occasionally calm winds developing late this afternoon into the evening, with speeds of 4-7 km/h. Periods of large smoke accumulations (but not overly thick smoke due to lesser humidity levels) are still favorable, with overall small smoke displacement. Wind direction should be ENE by late this evening, causing the smoke to move very gently towards sections of the bridge nearest to the river and Notre-Dame/de Lorimier/Viger Street. Smoke should also be moving gently towards spectators on Notre-Dame Street nearest to the bridge. Temperatures should also be 23-24 C by mid- to late-evening, along with borderline low-moderate humidity inducing a humidex of 26-27 C.

All other factors remain applicable.

And so concludes the weather reports for 2016. Although the competition is shortly coming to an end, I will continue to provide weather forecasts and outlooks on Facebook, mostly when severe to extreme weather becomes favorable for this general area.



Posted: Sep 3, 2016 00:17:08   Edited by: Smoke

Weather conditions this long weekend (September 3rd-September 5th) and, therefore, for the 10-minute display scheduled for about 8:45 p.m. on September 4th, are expected to be governed by a strong area of surface high pressure and accompanying mid- to upper-level ridge. These atmospheric features will play an important role in diverting the remnants of Hurricane Hermine gradually to the NE at it travels North, keeping S. Ontario to S. Quebec dry and pleasant this weekend.

Maximum temperatures of 27-28 C are expected by the mid-afternoon of September 4th, and temperatures should be 26-27 C during the early-evening for the greater Montreal area. Humidity levels should remain moderate, inducing a fairly small humidex of 28-29 C. No precipitation is expected, although the remains of Hurricane Hermine, in addition to slightly moderating maximum temperatures, would also affect the overall wind direction somewhat. At this point, surface and near-surface winds are projected to be light (at 6-9 km/h) through the day, including the evening, with SE directional tendencies, so the smoke could be moving clear to the right of La Ronde, but it would be moving towards far left-hand sections of Notre-Dame street (i.e. in the direction of the Olympic Stadium), and fairly gently. Smoke accumulations should not be overly large, however, due to moderate humidity. Skies should be partly cloudy, with mostly a few patches of cirrus clouds as the dominant cloud type, with large expanses of clear breaks between them.

Another update to follow by later this evening (September 3rd), or the morning of September 4th, mostly to address wind direction.


Posted: Sep 3, 2016 23:40:13   Edited by: Smoke

Weather conditions specified in the above posting continue to hold largely constant. As such, here are the dominant weather conditions for Sunday, September 4th for the Montreal area.


Maximum temperatures of 26-27 C are generally favorable by the mid-afternoon period. Temperatures drop to about 25-26 C by the early-evening. Humidity should be borderline low-moderate during the day but increases to moderate standards by the early-evening, inducing a slight humidex of 27-28 C by that time.


Under the influence of strong high pressure, precipitation development will be kept to a minimum. Some weak lift in the area will likely generate some patches of cirrus clouds, but skies should remain mostly clear, including into the evening, with continued isolated clusters of cirrus clouds.


With high pressure in the area, surface and near-surface winds are typically expected to be light to very light through the day, with speeds of 4-7 km/h (occasionally calm), and generally from the ESE. Southeasterlies should become more dominant by the early-evening, causing accumulating smoke to very gently move to the right of and partially away from the La Ronde audience, and toward far left-hand sections of Notre-Dame Street (heading North). Even though just a 10-minute display, periods of smoke accumulation will be favorable, but thick smoke is not likely.

In summary, a pleasant evening, with warm to very warm early-evening temperatures, very light SE winds, moderate humidity and mainly clear skies (a few cirrus cloud clusters).

*If necessary, another update will follow into the mid-afternoon of tomorrow (September 4th) to address wind direction.


Posted: Sep 3, 2016 23:59:32

It's very pleasant to read such weather forecast, especially for a such "bonus" display!


Posted: Sep 4, 2016 16:50:43

Indeed, it is a pleasant forecast! The only aspect that I would modify slightly is the evening temperature, reducing it to 23-24 C, with a humidex of 26 C. All other details hold constant.
I will also soon be posting my late-Fall and Winter outlook for 2016-2017, as well as preliminary thoughts on Spring and Summer 2017. In general, though, I am anticipating a harsher late-Fall and Winter for the mid-November to March period, in terms of temperatures and snowfall (more so for snowfall than bitter cold). I also suspect a cooler and wetter Spring and Summer, including a larger number of thunderstorm days and fewer days with maximum temperatures of 30.0+ C.

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