Hello everyone,

As the full schedule has recently become available, I thought that it would be appropriate to proceed creating this thread.

I will post here weather conditions for each of the eight (8) fireworks days for this year. These reports will include a preliminary forecast approximately two (2) days in advance from fireworks evenings, followed by a more finalized outlook about 24 hours prior to each of those evenings. In cases where further follow-ups are necessary, additional updates would be provided in separate posts on the display day itself. This would especially be applicable for situations of light/calm winds, unfavorable wind direction, and if/when thunderstorms/convective rainfall become apparent. Reports will include descriptions of temperature and humidity, rainfall potential, and wind speed/direction.

I also am very excited to share the news with forum members that I recently received my PhD in in the area of climate/atmospheric science and extreme weather.

Looking forward to the displays, as well as importantly ideal weather conditions to accompany them all.

Trav.

Congratulations on the PhD Trav!

I remember back many decades ago one of my fellow graduate students announcing when she got hers: "They may need to put me away, but they're going to have to call me Doctor!"

BobFF

What a wonderful news, Trav! This is a great achievement! Wow, congratulations!

And thank you to bring back this popular and very useful thread (actually, the most useful of all)!

Fred

Indeed hearty congrats Trav! I think I got my PhD before you were born!

Paul

Hi Bob, Fred and Paul,

Many, many thanks to you all for your very kind words and wishes for this milestone! Very much appreciated!

And yes, I am more than happy to create this weather thread for this latest edition of Montreal fireworks!

Cheers,

Trav.

The first opening display of 2024 (June 27th) would collectively be accompanied by generally good weather conditions, despite the extent of late-day cooling.

As a high pressure system begins displacing farther SE, a drier and cooler air mass would gradually establish itself in the region. In response to this, humidity would remain low, and the maximum temperature would reach a more reserved 21 C. By around sunset and beyond, however, conditions would be cool (15-16 C by display time) as temperatures are allowed to decrease more quickly, with amplified apparent cooling due to the continued breezy Westerly/WNW flow.

At the same time, prior to high pressure reaching this region more forcefully, lift along a cold front and shortwave trough would continue to support scattered convective rainfall during the predawn period to noon (40% probability). Beyond the early-afternoon, lift would become increasingly limited, supporting large clusters of fair-weather cumulus and overhead cirrus. Thereafter, the sky would adopt a distinct clearing that would permit for largely clear skies during display time.

Winds would be notably gusty from the WNW to West through most of the morning to late-afternoon period, with base speeds of 26-32 km/h and maximum gusts reaching 43-46 km/h during that time. By just before sunset, though, speeds diminish to 13-17 km/h under identical directional tendencies. This would allow the accumulated smoke to move sufficiently quick towards notably left-hand and central sections of the La Ronde audience, sometimes creating moments of haze if viewing from there. High-altitude smoke would be advancing more rapidly overhead towards left-hand sections of the audience, and partially over central sections (and for anyone viewing on the bridge behind the park).

Another update to follow by late this evening into early-predawn (June 26th-June 27th).

Trav.

Weather conditions described in the above posting continue to largely hold. As such, presented here is the expected pattern for this first display day (June 27th) for the greater Montreal area.

Temperature/Humidity

The temperature distribution for the day would be well cooler than normal – a distinction from the well warmer than normal pattern realistically featured by this June. As such, a maximum of 21-22 C is favored, though local rain-cooled air would lead prompt a localized decrease to 16-17 C temporarily. For the late-evening, including around display time, the temperature would be allowed to cool to 15-16 C. This represents the coolest conditions to appear during a fireworks evening, including display time, since the opening of show of 2016. A light sweater would be ideal to have on standby, especially if expected to be out for extended periods, and considering the somewhat breezy WNW flow persisting. Humidity would remain low, and so a Humidex is negligible.

Precipitation

As per the above posting, a secondary cold front and accompanying shortwave trough would be affecting principally the morning period, causing periods of moderate to heavy rainfall locally during early-predawn. In light of some stalling of these lifting features, some instability would linger through to the mid-afternoon. This would keep the convective rainfall risk intact until then, though the convective coverage would be isolated (30% probability for rainfall), and any rainfall would be brief due to fast SE/ESE movement. As the environment stabilizes into the late-afternoon, skies would adopt mostly large clusters of fair-weather cumulus, followed by a rapid clearing post-sunset.

Wind

Winds would resolutely hold onto a WNW tendency at all altitudes through the day. Wind speeds remain quite gusty through most of the morning to afternoon, with speeds of 26-32 km/h, and corresponding gusts sometimes achieving 44-47 km/h. Mostly post-sunset, wind speeds would diminish considerably but still hold a somewhat a breezy nature (13-17 km/h), adding an extra apparent chill in the air. Accumulated smoke would also be quickly displacing towards left-hand and large parts of central sections of the La Ronde audience, with higher-altitude smoke moving the most swiftly. At times (mostly during more active sections), the display would appear murky relative to the on-site audience (and for those watching from the bridge behind the park), but significant smoke accumulation would not be expected.

If necessary, another update will be provided by this mid-afternoon.

Trav.

The first in-competition display day (July 4th) would meet with much more Summer conditions, as compared with the considerably cooler situation produced by the day of the opening show (June 27th).

A fairly strong circulation of very warm to hot and highly humid air will advect into Southern Ontario to Southern Quebec over the next few days (and, really, much of this month into the beginning of August). The Japanese display and upcoming displays would, therefore, be a part of this potentially persistently hot pattern. Conditions on July 4th would entail a healthy SW/WSW flow in this region, prompting temperatures to reach 29-30 C in the greater Montreal area, along with very high humidity. This would create a maximum Humidex of 37 C. For display time, a temperature of 25-26 C is favorable (Humidex of 32 C).

At the same time, a weak cold front will be advancing SE through the day, affecting this region during the mid- to late-evening. Lift associated with this feature would be modest but sufficient to guide isolated convective rain showers and non-severe thunderstorms (30% probability). This will be something to monitor. Skies should be mostly clear early, followed by larger clusters of defined cumulus and overhead cirrus for the mid-afternoon to late-evening.

As the weak cold front shifts SE for the evening, wind direction could also adopt a more Westerly to WNW pattern, including during display time. Wind speeds would be sustained at 19-23 km/for the day (occasional gusts of 32-37 km/h). By late-evening, speeds should diminish to 13-17 km/h. As such, rapidly accumulating smoke should be displacing reasonably quickly (faster displacement at the highest altitudes of the display), but towards the La Ronde audience – at this point, left-hand sections and adjacent portions of central sections of the audience would be affected. If, however, the cold front ejects into the area sooner, then movement focused to left-hand sections would be more favorable. Due to the high humidity, significant smoke accumulation will be possible depending on the overall pacing of the display (and the extent of smoke-rich products along low- to mid-levels). At the same time, the introduction of an extensive laser-driven segment in these coming shows would be helpful for allowing any large smoke build-up to clear at that time.

Another update to follow late this evening into early-predawn (July 3rd-July 4th).

Trav.

Weather patterns detailed in the previous post remain mostly applicable. As such, described below are the expected conditions for this first in-competition display day (July 4th) for the greater Montreal area.

Temperature/Humidity

With a considerably warmer circulation of very warm and highly humid air, the first in-competition display day would offer a sharply different atmosphere than that featured by the opening, on June 29th. In light of this, a maximum of 29-30 C is favored, with a corresponding maximum Humidex of 37 C. Limited cooling would also take place for the late-evening, including display time, and so the temperature would only be allowed to cool to 26-27 C. Continued (very) high humidity would favor a Humidex of 33 C during display time. Note that if rainfall does occur, the air would cool to 23-24 C, along with enhanced humidification.

Precipitation

Adhering to the previous post, a weak cold front would be affecting primarily the evening period. The extent of dynamical lifting with this feature would be rather modest, but it would still be sufficient for sparsely-distributed convective rainfall and briefly-sustained non-severe thunderstorms in the area. As such, a 30% probability for rainfall is suitable for the evening period. Mostly clear conditions are favored for much of the day, though a gradual increase in cloud coverage via more defined cumulus clusters and overhead cirrus would be favored for the mid-afternoon to late-evening period.

Wind

SW to later WSW wind tendencies are favored. Wind speeds would be breezy during the late-morning to afternoon 19-23 km/h, and corresponding gusts sometimes achieving 32-37 km/h. Wind speeds decrease considerably after sunset, but they still continue with a slightly breezy pattern (12-16 km/h). In light of the cold front stalling somewhat, this would be enough to sustain a WSW flow (as opposed to the NW flow suggested in the previous posting). This would be helpful to better displace the rapidly accumulating smoke (at times) due to the higher humidity concentration. However, this would also displace the smoke towards right-hand sections of the La Ronde audience and partially adjacent central sections. Higher-altitude smoke would be advancing more directly and quickly towards central and right-hand sections. Particularly for the more active portions of the display, a hazier appearance would occur relative to the on-site audience at notably low- to mid-altitudes of the display (and for those watching from the bridge behind the park). However, although smoke build-up would be larger during portions this display (especially if some smoke-rich products are periodically used), the smoke should often clear quickly enough. Furthermore, as previously mentioned in the post above, the introduction of an extensive laser segment in this show and future ones will be helpful in this regard.

Another update will be provided by this mid-afternoon (July 4th) to address any changes to the nature of the evening convection, as well as wind direction.

Trav.

To follow-up with the previous post, wind speeds would be a little weaker for post-sunset than what was described above (8-11 km/h). However, the overall directional tendency would be more SW downstream of the weak cold front. As such, periods of extensive smoke accumulation are favorable, moving slowly towards mostly right-hand sections of the La Ronde audience, causing the display to sometimes appear hazy notably deeper into it at mostly its right end. At the same time, though, smoke at the highest altitudes would still be moving more quickly in that direction overhead, which would help, but also towards partially central sections of the audience. The overall richness of the colors from the shells and other products used may also sometimes appear dimmer due to the high humidity.

As mentioned, the extent of the smoke accumulation depends upon the overall pacing of the show and/or the amount of smoke-rich products appearing along low- to mid-altitudes of the display. Also as described in the previous two postings, the introduction of an extensive laser segment would be beneficial in this situation.

Apart from the light winds, sparsely-distributed convective rainfall and non-severe thunderstorms remain possible in the area for this evening and going forward into predawn, and so it is possible to see lightning flickering occasionally in the distance towards the NW and West late this evening.

Trav.

Conditions for the Italian display day (July 7th) would be characterized by a progressively stabilizing environment late-day as a weak area of high pressure ejects SE into this region. Ahead of this feature would be a partly cloudy sky occupied by mature cumulus. This is because lingering instability from July 6th would continue to invite some risk (30% probability) for convective rainfall during the morning to mid-afternoon period of July 7th. By late-afternoon, skies do clear more extensively, leaving behind some clusters of cirrus and isolated patches of less defined cumulus. In this setting, a maximum temperature of 29 C would also be favored in the greater Montreal area under continued borderline high to very high humidity (Humidex of 35 C). The late-evening would correspondingly feature a temperature of 25-26 C, and the high/very high humidity would send the Humidex to 32 C.

Winds would be in the form of SW through most of the day, being breeziest during the late-morning to afternoon, at 17-21 km/h (occasional gusts of 29-33 km/h). A reduction in speed to 12-15 km/h would be favored for the late-evening period in the wake of the aforementioned high pressure zone advancing East. As such, at all altitudes, accumulating smoke deeper into the display should be able to evacuate fairly quickly towards right-hand sections of the La Ronde audience, though the smoke at the highest altitudes would be also moving more swiftly towards partially central sections of the La Ronde audience overhead (a similar situation to the Japanese display). Smoke accumulation itself would be thicker during more active sections of the display, but the smoke should be displacing quickly enough most of the time despite the display sometimes taking on a hazy appearance along its low- to mid-altitudes at the right-hand side (La Ronde’s right). Some potential for a WSW flow deeper into the evening, and so this will have to be monitored.

A more finalized report to follow by early-predawn tomorrow (July 7th).

Trav.

The weather analysis presented in the above post concerning the Italian display day (July 7th) remains applicable. As such, presented below are the weather conditions for the greater Montreal area for July 7th.

Temperature/Humidity

A maximum temperature value of 29 C is favorable. Together with a continuation of borderline high to very high humidity, a corresponding maximum Humidex of 35 C is likely. The late-evening would feature limited cooling, as was the case for the Japanese display. As such, a display/show-time temperature of 25-26 C, with a Humidex to 32 C caused by high/very high humidity, should appear.

Precipitation

The day itself would be governed by some lingering instability during primarily the mid- to late-afternoon period. However, as a weak anticyclone advances East, a more stabilized environment would be favored by late-afternoon into the evening. Extensive cloud cover would first overspread the region during most of the morning, followed by breaks in this cloud deck. The broken afternoon skies would be comprised of some mature cumulus clusters and overhead cirrus. The afternoon instability would result in sparsely-distributed convective rainfall (20-30% probability of rainfall). By late-afternoon, skies do clear more extensively, as clusters of cirrus and isolated patches of less defined cumulus remain at the time.

Wind

A healthy SW flow should control much of the day. Speeds are strongest over the course of the late-morning to afternoon period, at 17-21 km/h (occasional gusts of 29-33 km/h). These speeds decrease to 12-15 km/h for the late-evening. Under such a configuration, accumulating smoke, venturing deeper into the display, would be advancing reasonably fast towards (far) right-hand sections of the La Ronde audience. At the highest altitudes of the display, the smoke would be displacing even more quickly toward right-hand and partially central sections of the La Ronde audience overhead (again, similar to what was observed during the Japanese display). In light of the high humidity, smoke accumulation would become more extensive when active and/or smoke-rich sections of the display appear. That being said, this smoke should be displacing quickly enough despite the display sometimes taking on a hazy/murky appearance along its low- to mid-altitudes deep in the show at the right-hand side of the display (i.e. La Ronde’s right).

If necessary, another update will appear here this mid-afternoon (July 7th) concerning wind direction.

Trav.

Recent/newest data reveals more of a WSW flow for this late-evening (July 7th). As such, this would allow the smoke, at all altitudes, to move somewhat more directly towards the La Ronde audience (mostly right-hand and partially central sections).

All other details remain valid in the post above.

Trav.

Trav, thank you again to dutifully provide these weather forecasts and updates for each show.

Do I need to say that your next posts are highly anticipated? I am afraid the depression from Beryl is going to impact the Austrian setup and the display. Hopefully, the winds are not going to be too strong on Thursday evening.

Fred

Following significant rainfall for setup today (July 10th), the Austrian display day (July 11th) would be influenced by the continued effects of the remnants of Hurricane Beryl. That being said, the evolutionary process and trajectory during extratropical transition could in a sense be more beneficial to Thursday than Wednesday because of this region being granted access to the warm sector of this system. As this happens, the low-cloud deck would exhibit enough discontinuity that the Sun should get through more regularly by late-morning Thursday and going forward. However, the interaction of this solar heating with very high humidity would encourage scattered convective rainfall and isolated non-severe thunderstorms among these in this region (40% probability for rainfall collectively through the afternoon-evening and 30% probability for thunderstorms during the afternoon).

More concerning, however, would be the potentially very light wind fields combined with likely what would become the most humid conditions to appear so far this month. This may result in substantial amounts of smoke accumulation deeper into the display - notably true when the display becomes active, and when it begins relying more on any smoke-rich products along low- to mid-altitude. That said, smoke at the highest altitudes would be displacing a little more quickly towards right-hand sections of the La Ronde audience.

The temperature itself would be quite warm, given the richness of the humidity in place already. To that end, a maximum of 26-27 C would be favorable for the greater Montreal area as the Sun breaks through more regularly, but the very high humidity contribution would send the Humidex to as much as 36 C. During the late-evening, 24 C is favorable, along with a corresponding Humidex of 32 C. This would be under mostly cloudy skies (a stratiform/low-cloud deck) with some clear breaks.

Another update to follow during early-predawn tomorrow (July 11th).

Fred – you’re more than welcome, and no problem for the updates!

Trav.