Hello everyone,

As we are now just under two weeks from the beginning of the 2019 competition, and being the precise midpoint of June, I thought that it would be reasonable to post this thread.

Here, I will typically post weather reports just prior to each of the eight display days. I will initially release preliminary reports approximately two days before each fireworks day, followed by finalized forecasts the evening previous. These reports will include information about daily temperature, humidity sky conditions, rainfall coverage (if any), and wind speed and direction. In cases where rainfall and/or thunderstorms are possible on fireworks days, subsequent updates will become more necessary, and so these may be provided as far as the mid- to late-afternoon of those particular days. This would also be applicable in situations where wind speeds are potentially either too weak or too strong, or if unfavorable wind direction is possible.

You are also more than welcome to post any weather-related information that you would like to share!

As always, I am hopeful for ideal weather conditions for all displays, as well as for the setup periods.

For anyone interested, my Spring-Summer 2019 outlook may be found here (released March 17th), so feel free to take a look:

https://www.linkedin.com/pulse/warmer-stickier-stormier-than-normal-la te-spring-summer-travis-moore/

Cheers,

Trav.

Trav, we are looking forward to read your inaugural weather forecast! It is great to have this thread back on the forum.

Fred

Im landing in two days, i have been checking the wheather forecast and it doesnt seem very friendly, at least for the first week of july. I would like to hear the Smoke’s opinion.

Following near-heat wave status over the June 26th-June 28th period for Southern Quebec, cooler conditions are expected for Sunday, June 30th. However, after Monday/Canada Day, at least near-heat wave status is likely for the July 2nd-July 5th period. Saturday, June 29th, itself will be a part of the transition to these briefly cooler conditions for Sunday and so could feature unstable conditions through the day.

For Saturday, a weak but broad area of low pressure will eject NE, though there remains some uncertainty as to the overall trajectory of this system. During the morning period, mostly cloudy and wet conditions are favorable North of the low’s warm front. As the system drifts farther North, larger clear breaks should gradually emerge by late-morning and onward. However, as these clear breaks emerge, along with further moisture enrichment, there appears to be a window of opportunity for thunderstorm development (some strong – this may induce severe thunderstorm watches by afternoon) during the late-afternoon to early-overnight due to enhanced instability ahead of the advancing cold front. It is the air flow behind this cold front that will temporarily allow for a cooler, drier airmass to follow for most of the day Sunday (June 30th). Depending on how much to the North the area of low pressure advances on Saturday, it will determine the degree of instability, and so this will need to be carefully monitored. At this point, convective coverage should be increasing to scattered by late-evening, so a 60% probability for rainfall is favorable for this time (40% for the afternoon to just after sunset).

For these reasons, a maximum temperature of 26-27 C is likely. As much as 28-29 C is possible if the clouds break earlier in the morning, if there is no interference from rain during the afternoon, and if the low travels farther North. Humidity should be high through most of the day, partly due to the evaporation associated with early-day convective rain showers and/or thunderstorms, and through any convective rains and/or thunderstorms during the afternoon period. By late-evening, the temperature should drop to 22-23 C (except 20-21 C if rainfall occurs) in the greater Montreal area. Borderline high to very high humidity should make it feel like 28-29 C during this time.

Due to the uncertainty of the low’s trajectory, it is unclear what the predominant wind flow will be by the evening period. Winds are likely to be somewhat breezy during the afternoon (14-19 km/h, with occasional gusts of 24-28 km/h), from the WSW, which should continue into the evening. This would allow the smoke to reasonably quickly drift towards right-hand and partially central sections of the La Ronde audience. That said, humidity is expected to remain relatively high during the evening period before the cold front passes through this region, and so smoke accumulations are likely to be high at times. This is most applicable during active sections of the display, and where smoke-rich products are used along low-level. The smoke should be displacing adequately most of the time, though, but the smoke itself will be expanding in response to the higher moisture level.

*Another update to follow by later this evening (June 28th), especially to address rainfall potential and overall wind circulation for tomorrow/Saturday.

Trav.

Details presented in the above posting continue to be largely applicable for this 2019 opening display day, though with some revisions to wind speed and direction. As such, here are the most favorable conditions for the greater Montreal area for today (Saturday, June 29th).

Temperature/Humidity

A very warm and humid airmass continues to affect Southern Ontario to Southern Quebec. Sufficient breaks in the cumulus cloud deck will allow for ample solar heating, especially by late-morning and onward. This would favor a mid-afternoon temperature of 27-28 C before convective rainfall and/or thunderstorms potentially interfere by mid- to late-afternoon. Humidity should be borderline high to very high, and so a humidex of 34-35 C is likely by mid-afternoon. Into the late-evening, the temperature value should decline to 22-23 C (humidex of 28-29 C), although if rainfall or thunderstorms affect the area, temperatures closer to 20-21 C are more favorable, with a humidex of 26-27 C.

Precipitation

A sharp cold front will be ejecting SE through the day today and will be the focus for convective rainfall and scattered thunderstorms (some reaching strong to severe standards). As mentioned above, frequent breaks in the cumulus cloud deck should lend support for moderate instability by mid-afternoon, and sufficient lift will eventually favor scattered convective coverage (i.e. 40% probability of precipitation) through the afternoon, but 60% by mid-afternoon. Continued instability and favorable lift into the evening period will allow scattered convective coverage, as well (60% probability). Thunderstorm severity should decrease not long beyond sunset, but thunderstorms altogether will continue to be possible throughout the evening. For these reasons, severe thunderstorm watches will be possible, especially NW of the island this mid- to late-afternoon, but an advisory could eventually be introduced on the island and neighboring locations. The strongest thunderstorms will be capable of intense lightning, torrential rains and locally damaging wind gusts along thunderstorm gust fronts. Skies should be partly cloudy (large clusters of defined cumulus) for the evening. It is also with a fair possibility that a small break will occur during display time, with lightning being seen flashing in the distance. This will have to be monitored.

Wind

Westerly to WNW winds are favored through the day, but with speeds of 13-17 km/h. By evening, WNW tendencies should continue, but with speeds diminishing to 8-11 km/h, although some uncertainty remains with overall evening wind velocity. In these situations, the smoke should be blowing slowly towards left-hand and partially central sections of the La Ronde audience, and towards those positioned on the bridge behind the park. Periods of (extensive) smoke accumulation will be possible due to high humidity, light winds, and potentially near-saturated air if persistent rainfall occurs during or just prior to the display. This is mostly applicable deeper into the display, during more active segments, and along low-level, notably in cases if/when smoke-rich products are used. This could sometimes cause the display to appear murky.

If necessary, subsequent updates will follow by this afternoon (June 29th), especially for convective rainfall/thunderstorm risk and wind speed/direction.

Trav.

The MeteoMedia radar shows that a line of thunderstorms is approaching the Montreal area.

MeteoMedia radar projection also shows that a second line of thunderstorms may move across Montreal around... 10pm.

Fred

No changes to the above-mentioned details. The thunderstorm/convective rainfall risk will continue this evening (although, again, the “severe” risk will likely ease into the late-evening, as well as a reduction in thunderstorm coverage - this could give a narrow window of opportunity for drier conditions during display, with lightning seen in the distance). Wind speed and direction also continue to be largely the same, except that more NW to NNW tendencies are favored (allowing smoke to move more towards extreme left-hand sections of the La Ronde audience and those behind, on the bridge. Very high level smoke should be moving somewhat faster relative to lower-level smoke accumulations (same direction), but periods of extensive smoke accumulation will still be possible farther down. If thunderstorms are in the area, note that the wind flow will temporarily be disrupted, and the smoke would more favorably move towards the La Ronde audience If the display is not overly active, it would give time for the smoke to displace to some extent deeper into the display.

Trav.

The aforementioned potential heat wave continues for this week (July 2nd-July 5th). Strong and amplified ridging towards the East this week will encourage a circulation of very warm and moist air across much of Eastern Ontario to Southern Quebec. As such, July 3rd will be a part of this pattern.

A maximum temperature of 30 C is expected by mid-afternoon, along with a late-evening temperature of 27-28 C, in the greater Montreal area. Humidity is also likely to be high. This would yield a humidex of 34-35 C during the mid-afternoon and 32-33 C by late-evening.

No precipitation is expected, but modest lift in the area will support patches of high-level cirrus and a few fair-weather cumulus throughout the day, including the evening period. Therefore, mostly sunny skies are favored, and large clear breaks for the evening.

Wind speeds are expected to be light for the day under the influence of stable conditions. Wind speeds of 7-11 km/h are favorable for the day (except 13-17 km/h during the afternoon). Directional tendencies are largely in the form of WSW, but by evening, there are/have been indications of a shift to SW. Thus, the smoke should be moving gently towards far right-hand sections of the La Ronde audience. Note, however, that smoke from higher level shells may be moving towards right-hand and partially central sections of the audience directly, and at a somewhat faster pace. Some periods of smoke accumulation will be possible during more active segments along low- to mid-level, and mostly deeper into the display, due to the light winds and relatively high humidity. Still, the speeds should be narrowly enough to allow the smoke to displace adequately most of the time, especially at very high-level.

Another update to follow by later this evening (July 2nd) or early-pre-dawn of July 3rd to confirm these conditions.

Trav.

Conditions discussed in the above posting continue to be applicable for the South Korean display, as well as for the day itself. As such, I present here the expected conditions for Wednesday/today, July 3rd for the Montreal area.

Temperature/Humidity

The potential for heat wave status continues for this week across extreme Southern Quebec. As today is a part of this event, a maximum temperature of 30 C is likely. By late-evening, around display time, temperatures should still remain as high as 26-27 C in the greater Montreal area. As humidity should be high through the day, a maximum humidex of 35 C is favorable during the mid-afternoon, while at 31-32 C for the late-evening under borderline moderate-high humidity.

Precipitation

No rainfall is expected. Modest lift in the area, however, should encourage a few clusters of high-level cirrus (i.e. wispy/feathery-looking formations) and clusters of fair-weather cumulus (puffier low-level clouds). Skies should be mostly clear for the evening, with residual isolated cirrus.

Wind

Wind velocity is expected to be WSW at 7-11 km/h through the day. By late-afternoon (i.e. near sunset), directional tendencies are still shown to shift to SW, with wind speeds of 6-9 km/h. This would cause the smoke to drift rather gently towards right-hand sections of the La Ronde audience. Very high-level smoke should be moving somewhat faster overhead but more towards right-hand and partially central sections of the La Ronde audience. Due to light winds and approximately high humidity, periods of smoke accumulation will be possible deeper into the display, and principally along low-level, causing the show to occasionally appear hazy. This is mostly applicable during more active segments, and whenever smoke-rich products are used. Smoke accumulation will be most prominent to La Ronde’s right-hand side as the display progresses. Fortunately, humidity levels will not be very high for the evening, and there should be narrowly strong enough wind speed to help displace the smoke quickly enough most of the time. Thus, particularly extensive smoke accumulations are not expected.

If necessary, another update will follow by this mid- to late-afternoon (July 3rd), mostly directed at any subtle changes in wind speed and/or direction.

Trav.

A weak cold front will be migrating SE through the early portion of the day on Saturday, July 6th across S. Ontario to S. Quebec. This feature will be the principal source of lift for scattered convective rainfall and some mostly non-severe thunderstorms during the morning to mid-afternoon period. However, because of the early timing of the cold front, it would appear that the severe thunderstorm risk will be limited and, thus, more focused farther South of these regions. Still, there exists a narrow window of opportunity for a few stronger thunderstorms to develop by late-morning before evolving with Southward and SE progression.

Fortunately, this also suggests steadily improving conditions by the late-afternoon and evening of July 6th. That said, during this time, a trough, also advancing SE, could encourage some isolated rain showers (30% probability) just prior to and a little after sunset before the air stabilizes further thereafter. Therefore, by late-evening, including display time, skies should be partly cloudy (this would include some clusters of residual cumulus and cirrus) due to weak lift in the area.

Temperatures in the greater Montreal area should also be 24-25 C during the display. The humidity level will be dropping rather quickly after sunset, from very high early in the evening to moderate later in the evening. A maximum temperature of 28-29 C will be possible on the day Saturday itself, providing that rainfall and cloud cover do not interfere with solar heating too extensively. A humidex of 36-37 C is possible by mid-afternoon, and 28 C by late-evening/display time.

The decline in temperature and mostly humidity later in the evening will also be accompanied by a shift in wind direction. Through the early portion of the day, winds will be in the form of SW to WSW, but by mid-afternoon, a transition to WNW to NW is favorable. Beyond sunset and closer to display time, this should become NNW to even straight Northerlies. Winds should also be breezy through the day, at 17-22 km/h, and there are indications that this could continue through the evening (15-19 km/h, with occasional gusts of 27-31 km/h). This would allow the smoke to drift rather quickly, at all altitudes, clear to the left of the La Ronde audience (right for those on Notre-Dame Street), although moving unfavorably towards those on the bridge closest to the park, making the display appear murky there. This could also cause the display to appear sometimes murky for those at the Old Port, but particularly extensive smoke accumulations are not expected.

Another update to follow by later tomorrow evening (July 5th) or early-pre-dawn July 6th.

Trav.

What was stated in the above posting continues to largely be applicable. As such, here are the weather conditions expected for the greater Montreal area for Saturday, July 6th.

Temperature/Humidity

As the circulation of warm, moist air enters these regions through to the late-afternoon period, a maximum temperature of 28-29 C is expected. By the late-evening, the temperature should decrease to 22-23, including during display time. Humidity will be very high during the morning period, but humidity will drop rather drastically by late-evening. Thus, the humidity gradient will be quite apparent between early in the day and later in it – even during the evening itself, the decline will be noticeable between early- and late-evening (i.e. between sunset and display time to midnight). Therefore, a maximum humidex of 35-36 C is favored by early-afternoon, and a more negligible humidex of 25 C by late-evening due to low humidity.

Precipitation

As mentioned in the above posting, a cold front will be advancing SE through the early portion of the day. This front will be the focus for scattered convective rain showers and mostly non-severe thunderstorms. Due to the rather early timing of the front, there continues to be reason to believe that thunderstorm severity will be limited in these regions, with a better chance for more robust intensification farther South and SE by mid-afternoon. Nevertheless, there exists a narrow window of opportunity for stronger thunderstorms to develop in S. Quebec (including the island) by late-morning to early-afternoon, especially near the New York border. By mid-afternoon, skies should begin to clear, with residual high-level cirrus coupled with clusters of fair-weather cumulus (i.e. puffy clouds with limited vertical definition). This combination of low- and high-level cloud should continue into the evening, but with even larger clear breaks emerging by late-evening. The aforementioned trough will also eject to the SE a littler earlier, which would favorably discourage isolated rainfall for the late-afternoon to early-evening period.

Wind

As with the above posting, wind direction will largely be in the form of WSW for the early-portion of the day. However, the shift to NNW is more favorable to occur by the mid-afternoon period, as opposed to the early-evening, as high pressure begins to drift SE behind the cold front. Wind speeds of 17-22 km/h will be possible early in the day, with a slight decrease by late-evening to 14-18 km/h (though occasional gusts of 27-31 km/h). At all altitudes, these wind fields would allow the smoke to displace rather quickly clear to the left of the La Ronde audience (clear to the right for those on Notre-Dame Street). That said, the smoke would unfavorably be moving towards those positioned on that section of the bridge immediately bordering La Ronde, causing the display to appear murky from there. This effect may also, to some extent, be observed from the Old Port.

If necessary, another update will follow by tomorrow mid-afternoon (July 6th), mostly to address wind speed and/or direction.

Trav.

A return flow of very warm, moist air under a developing ridge of high pressure will affect S. Ontario to S. Quebec over the July 9th-July 11th period, creating conditions suitable for another possible heat wave. This is especially possible for extreme S. to SW Quebec. As such, the Portuguese display day (July 10th) will be a part of this event.

A maximum of temperature of 31 C is likely for the greater Montreal area by the mid-afternoon of July 10th, followed by only a slightly decline to 27-28 C by late-evening, including display time. High humidity will also be present by mid-afternoon, and so a maximum humidex of 36-37 C is likely by that time, whereas 33-34 C is favorable for the late-evening.

Although rainfall is not expected, weak lift and modest instability in the area will support large clusters of high-level cirrus (wispy-looking clouds) and clusters of somewhat vertically defined cumulus. This combination of cloud should persist through the evening period, though the clusters of cumulus are likely to reduce in number by evening.

Winds should be in the form of SW throughout much of the day. Near sunset, a shift to SSE to even SE will likely occur. However, wind speeds will be light through the day (except a little breezier, at times, during the mid-afternoon), especially post-sunset, at 6-9 km/h. This would allow the smoke to displace quite gently but clear to the right of the La Ronde audience and often moving narrowly fast enough. Light winds and high humidity would favor periods of smoke accumulation deeper into the display along low- to mid-level, notably during/following active sections, and if/when smoke-rich products are used. Accumulations of smoke will be most noticeable to La Ronde’s right-hand side, sometimes causing the far right-hand section of the display to appear hazy and/or partially hidden. It is possible for SE winds to also be present by display time, which would help to push the smoke a little more directly away from the La Ronde audience as it moves to the right (slowly). Therefore, this will continue to be monitored.

Another update to follow later this evening (July 9th) into pre-dawn July 10th.

Trav.

Forecast details presented in the above posting continue to be applicable for the day today. As such, here are the conditions expected for today (July 10th) for the greater Montreal area, and for the Portuguese display.

Temperature/Humidity

Very warm/hot and humid air continues to affect S. Ontario to S. Quebec under a developing ridge of high pressure. This suggests a maximum temperature of 30-31 C by mid-afternoon for the greater Montreal area. Due to high humidity, very little cooling is expected by late-evening. Therefore, a temperature of 27-28 C is likely. A maximum humidex of 36-37 C should also be present during the mid-afternoon, and with continued high humidity for the late-evening, including during display time, a humidex of 33-34 C is favorable.

Precipitation

No rainfall is generally expected. However, as outlined previously, weak lift and some instability will be suitable enough for large clusters of high-level cirrus cloud (i.e. wispy-/feathery-looking clouds), along with gradually some large clusters of somewhat vertically developed cumulus. This will create partly cloudy conditions that will linger into the evening period, though the number of cumulus clusters should decrease enough to allow for more clear breaks. To add to the above posting, though, very sparsely distributed brief convective rain showers (20% probability) will be possible in this general area, especially North of the island, over a narrow window of opportunity during the mid-afternoon before subsiding thereafter. (Strong) Thunderstorms will be favorable for the day Thursday (July 11th).

Wind

Light winds continue to be likely throughout the day, even during the mid-afternoon. Winds should be in the form of SW early in the day but will evolve into more of a SSW to straight Southerly flow by the mid- to late-afternoon. Beyond this, winds should become SSE post-sunset, and then SE by/near display time, at 6-9 km/h. This would allow the smoke, at all altitudes, to displace slowly clear to the right of the La Ronde audience, as well as away, moving towards far left-hand sections of Notre-Dame Street (Notre-Dame’s left, going NE). Very high-level smoke should further be moving a little faster relative to low- to mid-level smoke. Periods of smoke accumulation will be possible to La Ronde’s right (Notre-Dame’s left) deeper into the display (inducing sometimes hazy conditions to La Ronde’s right-hand side) but mostly during/following more active segments. Nevertheless, wind speeds should (narrowly) be sufficient to steer the smoke fast enough most of the time, and the easterly component in the wind fields should help viewers at La Ronde in light of fairly weak wind speeds. For those on Notre-Dame Street, being positioned closer to the bridge for viewing would be ideal.

If necessary, another update will follow this afternoon (July 10th) to address wind speed and/or direction.

Trav.

The environment of July 17th across extreme Southern Quebec, including the island of Montreal, will be characterized by very high humidity early in the day. It is largely this humidity that will drive instability supportive of scattered convective showers and isolated non-severe thunderstorms during the first half of the day as an East-West-oriented cold front shifts South. Consequently, humidity levels will be declining through the afternoon period and will reach moderate standards by the early-evening.

For the greater Montreal area, due to extensive early-day cloud coverage and periods of rainfall, a maximum temperature of 23-24 C will be possible. That said, under very humidity during the late-morning to early-afternoon, a maximum humidex of 31 C is favorable. By late-evening, the temperature should drop to 21-22 C, but with borderline low-moderate humidity, the humidex will be negligible.

While convective rainfall and isolated non-severe thunderstorms are favored for July 17th, the early timing of the aforementioned cold front would mean that convection will be confined to the morning to mid-afternoon period, as high pressure forces a drier and cooler air mass by late-afternoon to evening (i.e. near sunset and onward). Mostly clear skies will be present by late-evening, with some residual high-level cirrus in the distance (i.e. distant wispy/feathery clouds).

As high pressure advances South, winds will shift to a breezy NNE flow in time for the evening (NE by mid-afternoon). Speeds of 11-15 km/h are likely for the late-evening period, including during display time. This would allow the smoke, at all altitudes, to drift relatively quickly (especially high-altitude smoke) clear to the left of the La Ronde audience (clear to the right for those on Notre-Dame Street). However, smoke would be travelling frequently towards those on that adjacent section of the bridge immediately bordering La Ronde, causing the display to sometimes appear hazy from there - this effect could also be observed from the Old Port. However, no real periods of significant smoke accumulation are expected during the American display. The breezy nature of the winds, though, could occasionally induce a slight chill as they blow due to lower humidity and somewhat cooler temperatures by late-evening.

Another update to follow by either this evening (July 16th) or pre-dawn July 17th.

Trav.

Weather information presented in the above posting remains mostly applicable. However, some minor revisions were made to maximum temperature, humidity and wind direction. As such, here are the expected weather conditions for the greater Montreal area for Wednesday, July 17th.

Temperature/Humidity

A very warm and very humid air mass will continue to linger through much of the day prior to the passage of an East-West-oriented cold front. The pre-frontal environment will be characterized by mostly cloudy skies consisting of a cumulus cloud deck early in the morning. However, as the morning progresses, recent and latest model data suggest breaks in this cloud deck emerging by late-morning. This would allow sunlight to break through earlier and will, thus, allow for a higher maximum temperature to be attained by mid-afternoon. As a result, a daytime high of 29-30 C is favorable (especially if rainfall does not interfere excessively), and with very high humidity, a maximum humidex of 37 C to locally 38 C is likely. By late-evening, including display time, the temperature will decline to 21-22 C, but with moderate humidity, a modest humidex of 25 C is favorable.

Precipitation

While no rainfall is expected during the evening, some minor lift in the area will support a few residual high-level cirrus in the distance (i.e. distant wispy/feathery clouds), leaving largely clear skies by late-evening, as mentioned in the previous posting. Earlier in the day, however, scattered convective showers and isolated non-severe thunderstorms will be possible ahead of the cold front up to the mid-afternoon, although convective coverage should decrease by mid-afternoon as high pressure begins to drift farther South. That said, with more opportunities for solar heating, larger instability could narrowly support some organized convection later in the morning to early in the afternoon before these shift South. Nevertheless, the strongest thunderstorms will remain into New York state, but some of the convective rainfall in extreme S. Quebec may still locally be torrential in this environment during the late-morning/early-afternoon period, especially if it is accompanied by thunder/lightning. Conditions will steadily improve by mid-afternoon, although isolated rain showers are still possible during the mid-afternoon (30% probability, as compared to 40% during the early-afternoon).

Wind

Winds are expected to shift to a NNE to NE regime by late-afternoon in response to high pressure. This flow would allow for a drier and somewhat cooler air mass to temporarily settle into the region before (very) hot and moisture-rich air returns for the July 19th-July 21st period (inducing near-heat wave status). Wind speeds of 12-16 km/h are likely for the evening. However, there appears to be more of a transition to NE tendencies by late-evening (including display time) following the original NNE flow. This would allow the smoke, at all altitudes, to move fairly quickly clear to the left of the La Ronde audience, as well as away. Higher-altitude smoke should be moving most rapidly. At the same time, the smoke would be displacing towards portions of the bridge over the river, causing the display to appear murky from there, as well as from the Old Port. For those on Notre-Dame Street, it would be best to be positioned away from the bridge (going NE) to avoid occasional smoke interception, although smoke interception is more important for those on the bridge closest to Notre-Dame Street and the river. Fortunately, significant smoke accumulation continues to not be expected during the American display.

If necessary, another update will follow by this mid-afternoon (July 17th) to address wind direction.

Trav.