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 Montreal Fireworks Forum —› General —› Weather Cooperation (or not) for Summer 2017.
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Posted: Jun 15, 2017 23:06:34

I thought that it would now be appropriate to introduce this thread, as we are just a little over two weeks until the first display of the 2017 season.

I will include here weather reports that outline temperature patterns, moisture/humidity concentration, precipitation (rainfall), and wind velocity, for each of the fireworks displays. Additional information will be provided in situations where thunderstorms become favorable (notably strong to severe thunderstorms), or if wind speeds are expected to be either too strong or too weak. Some preliminary details will be supplied typically two evenings prior to each display, with a finalized report on the day before a scheduled display, or on the morning of the display date. If necessary, additional postings will follow on the day of the display, especially if/when thunderstorms are possible, or if wind speed/direction is expected to be unfavorable.

Feel free to also post any weather information that you would like to share, as you are more than welcome to do so - local observations can be very useful, so please share your reports!

For those interested, my Spring-Summer 2017 outlook can be found here (the document was originally released on March 17th – St-Patrick’s Day):

https://www.facebook.com/notes/travis-moore/winter-2016-2017-and-a-loo k-ahead-to-spring-summer-2017/10154952251701346/

In summary, I am projecting a late-Spring and Summer that is warm to very warm across S. Ontario to S. Quebec, but not quite as warm as what was observed in 2016. This includes slightly fewer days with maximum temperatures of 30.0+ C (for the island of Montreal, specifically, I am projecting 12-15 such days, with two to perhaps three heat waves possible). That said, this should be more of a humid season that may come close to 2015's overall humidity level over the May-September period. I also anticipate a stormy season, so more thunderstorms than normal are possible this year across these regions, though fewer severe thunderstorms than in 2016. This may also drive an above normal rainfall pattern this Summer, especially in areas where thunderstorms repeatedly influence.

Again, I hope for ideal weather conditions for all displays this year, as well as their respective setup periods (at least in large part).

Trav.


Posted: Jun 29, 2017 23:43:31

A very buoyant air mass is expected to govern Canada Day across S. Ontario to extreme S./SW Quebec as an area of low pressure brings with it very warm and very moist air. At the same time, a cold front and mostly series of shortwave troughs will be moving East/NE and will the focus for thunderstorm/convective rainfall development through the day. While it is currently unclear how these lifting features will affect the evening period, lift does appear greatest during the pre-dawn to late-afternoon time frame, likely causing at least scattered thunderstorm coverage during that time. Stronger thunderstorms will also be possible in this environment during the day, although with restricted solar heating and weak cooling rates aloft, coverage of these storms should be isolated at best. Latest model guidance suggests a zone of steeper cooling rates into the evening to early-overnight period, which could encourage sustained thunderstorm intensity and coverage (provided enough lift, which needs to be monitored), though convective coverage should be reduced from what it is in the afternoon. Latest indications would suggest that thunderstorms and convective rains will be mostly focused in New York state for the evening because lift is maximized there, leaving mostly cloudy skies for extreme S./SW Quebec.

Early-evening temperatures in the Greater Montreal area should be as much as 25-26 C and dropping to 22-23 C by mid-evening (except 20-21 C, if there is persistent light rain showers). With borderline high to very high humidity, a humidex of 29-30 C is favorable for the mid-evening. Sufficient lift will induce mostly cloudy skies (large clusters of cumulus) with clear breaks. Latest analyses suggest winds to begin with a SE component early in the day, and then transition to the SW by early-evening in extreme S. Quebec, including the island of Montreal. Wind speeds are gusty, from the SE for the afternoon, with sustained speeds and gusts of 23-31 km/h and 43-52 km/h, respectively. Near-saturated surface air and high humidity will favorably induce rapidly accumulating smoke (especially along low- to mid-level and with any smoke-rich products), but with fast wind speeds, the smoke should be moving quickly, and towards right-hand sections (partially central sections) of the La Ronde audience. Wind gusts, however, will need to be followed, as they may be near or slightly above the 40 km/h threshold. Other model solutions show considerably lower wind speeds because of a different trajectory in the area of low pressure.

Another update will follow by tomorrow evening (June 30th), or by pre-dawn July 1st, especially to address wind speed/direction and thunderstorm potential for the evening in this region.

Trav.


Posted: Jun 30, 2017 09:31:01

Trav, thank you for this detailed report, I am sure that many of us will look at the updates. We'll apparently have to deal with active weather conditions for this opening show, I am especially concerned with the wind. Hopefully, it is going to slow down during the evening.

Fred


Posted: Jul 1, 2017 01:39:28

The information presented in my previous update is mostly applicable for today (July 1st-Canada Day). As such, here are the most likely conditions to be present for the day for the greater Montreal area:

Your Canada Day forecast

Temperature/Humidity

With ubiquitous cloud coverage, maximum temperatures in extreme S./SW Quebec should reach 24-25 C, but this maximum value is mostly confined to later in the afternoon period, near sunset, when some solar heating should break through the cloud deck. Temperatures should drop slightly to 22-23 C by the mid-evening period (except 20-21 C, if some rainfall occurs). Humidity will also remain very high throughout the day and persist through the evening period, generating a humidex of 29-30 C for the evening period.

Precipitation

As mentioned in the previous posting, a cold front and shortwave trough will eject East through the day and will be the focus for (deep) convective development. Although persistent cloud coverage should significantly limit instability, the degree of lift with these features, coupled with rich surface moisture, will be conducive to thunderstorm development. Lift associated with these features still appears greatest during the mid-afternoon period. However, the lack of instability will likely keep thunderstorm coverage isolated to scattered, at best, through the day and into the evening period. Instability, though, is shown to be increasing slightly into the evening, likely due to the aforementioned cold pool of air aloft moving into the region by about sunset, along with more broken skies.

The convective/thunderstorm threat should begin to diminish more substantially by the late-evening, towards 11:00 p.m. and onward. Coverage becomes more isolated by about 9:30 p.m. (30% probability), with most of the thunderstorms/rainfall farther East/NE/NNE, but the thunderstorm/convective rainfall threat should continue in and around the island through the evening, but especially the early-evening, when colder air aloft could sustain/encourage thunderstorm development. The primary threat with thunderstorms in this environment will be torrential rains and locally damaging winds. Intense lightning will also be possible, particularly up to the early-evening.

Wind

Some uncertainty as to wind velocity for the evening period (especially since thunderstorms are still possible), but wind speeds are shown to still be gusty through the mid-afternoon (mostly from the 4:00-6:00 p.m. time frame), from the ESE to eventually SE. Speeds, though, should decrease to lighter standards (13-17 km/h) by about sunset and onward before increasing again by later overnight. Directional tendencies are still expected to be SW (with a slight SSW component) for the evening, so the rapidly accumulating smoke should be moving reasonably quickly to the right of the La Ronde audience. However, extreme right-hand sections could still encounter smoke. Due to very high humidity and near-saturated surface air, periods of smoke accumulation will be favorable during times of higher activity, especially along low- to mid-levels, and if smoke-rich products are extensively used. Note that if thunderstorms are in the area, or close by, the local wind flow will be temporarily disrupted.

Other updates will follow into this afternoon to further assess the thunderstorm risk for the evening period, as well as wind speed and direction. If not, then the information presented here would still be applicable.

And no problem for the reports, Fred!

Trav.


Posted: Jul 1, 2017 16:08:04

It seems to be less rainy and less windy than expected. Chances for improvement with tonight forecast?

Fred


Posted: Jul 1, 2017 16:44:51

It seems to be less rainy and less windy than expected. Chances for improvement with tonight forecast?

Indeed, the sun is even coming out a bit! The radar looks hopeful, for now, too!

Paul


Posted: Jul 1, 2017 17:37:57

No real changes to the information presented in the previous posting. However, instead of wind speeds increasing during the mid-afternoon period, as suggested above (4:00-6:00 p.m.), they should more favorably increase (from the SSW to SW) closer towards midnight. Speeds of 11-14 km/h are favorable for the mid-evening (including display time). Periods of smoke accumulation are still favorable with the somewhat light wind speeds (directional tendencies are the same).

The emergence of more breaks in the cloud deck for solar heating at this point is also consistent with the details in the "Temperature/Humidity" section, although this, in addition to cooler temperatures aloft overspreading the region shortly, will likely encourage thunderstorm development over the coming hours. Thunderstorm coverage, though, should remain scattered, at best, and still become more isolated by about 9:30 p.m., with partly cloudy skies. Severe thunderstorm watches are currently enforced for sections of E. Ontario and may briefly spread farther East if thunderstorm coverage increases. The number of storms should decrease beyond the early-evening, but they will exist in an isolated distribution (mostly focused North/NNE of the island).

Trav.


Posted: Jul 2, 2017 13:17:44

The reason for the sudden transition to a Westerly wind direction towards the final few minutes of the display was that rainfall was moving into the area at the time, as you specified. Due to instability present throughout most of the evening, isolated convective rainfall was still very much possible. That particular rainfall itself was associated with a small, weakening thunderstorm cluster previously forming to the North, and occasional lightning was observed in that direction by not long after 9:00 p.m.

Thank you for these specifications, which I paste from the Opening review thread. I believed that some lighting appeared north-east from La Ronde around that time, but I saw it just once, so I was not sure whether it actually happened or not.

Fred


Posted: Jul 7, 2017 01:08:40

A series of shortwave troughs behind today’s (July 7th) surface cold front will be the focus for convective rain showers and mostly non-severe thunderstorms for Saturday, July 8th, mostly during the morning to mid-afternoon period. During the morning hours, however, there appears to be a narrow window of opportunity for a few stronger thunderstorms to develop due to instability being maximized at the time. By the mid- to especially late-afternoon, convective coverage should decrease and become sparse as the shortwaves eject East, but some instability for brief convective rain showers will persist up to about sunset. More breaks in the cloud deck for sunlight should emerge by the early-afternoon, and skies should be mostly clear by late-evening (a few large patches of cumulus and cirrus).

For the Greater Montreal area, maximum temperatures are expected to be about 22-23 C, with high (not very high) humidity. Humidity should become moderate in time for the late-evening (including display time), and temperatures should fall to 18-19 C (humidex of 21-22 C.
Winds will also be somewhat light (12-16 km/h, except breezier during the mid-afternoon, at 17-21 km/h) through the day, first from the NNE during the morning, and then switching to WSW tendencies by the early-afternoon, persisting through to the evening. By late-evening, a slight shift towards the SW is possible, but the predominant directional tendencies are mostly WSW into the evening period. As such, the smoke should be moving at a reasonable pace, though some smoke accumulation will be possible during more active sections of the display due to moderate humidity. At this point, the wind should be directing the smoke towards the La Ronde audience, with a focus towards right-hand and central sections. This will often times cause the display to appear murky, especially during times of larger activity. If a SW component becomes more predominant in later data, then more smoke concentration to right-hand sections of the audience will be favored.

Another update to follow later today or pre-dawn July 8th to finalize conditions, especially to address wind direction.

*Fred – thank you for sharing your observations concerning July 1st’s lightning occurrences – indeed, lightning detection data is consistent with what you had seen at the time.

Trav.


Posted: Jul 8, 2017 01:10:09

Details specified in the above posting still largely remain constant. As such, here are the predominant weather conditions for the greater Montreal area for Saturday, July 8th.

Temperature/Humidity

Temperatures are expected to rise to 22-23 C by mid-afternoon. If periods of rain are persistent, then the maximum temperature should be about 19 C. By the late-evening period, including display time, a value of 18-19 C is largely applicable. Humidity will remain high (not very high) through the day and fall to borderline moderate-high standards by the mid-evening, creating a slightly humidex of 21-22 C.

Precipitation

As mentioned in the above posting, a series of shortwave troughs will move East/NE through mostly the first half of the day will be the focus for ubiquitous cloud coverage, convective rain showers and isolated non-severe thunderstorm clusters. A few more organized thunderstorms, however, appear possible during the morning to early-afternoon period, but convective coverage should become sparser by the mid-afternoon. Some instability will persist in the area, however, until about sunset, so isolated convective rain showers will exist up to roughly that point (30% probability), leaving partly cloudy skies (with large clear breaks) by the mid- to late-evening (patches of large cumulus and cirrus). More periods of sunlight should emerge by the mid-afternoon.

Wind

Winds continue to be mostly in the form of West-Southwesterlies (WSW) by the late-afternoon period (more NNW to NW during the early- to mid-afternoon). Speeds of 12-16 km/h are favored throughout the day, including the evening. As such, the smoke (and some pyrotechnic debris) should still be moving towards the La Ronde audience, mostly focused on central and right-hand sections. With borderline moderate-high humidity, some periods of smoke accumulation will be possible during times of higher activity, but the smoke should be usually moving at a reasonable pace. The display could often appear murky for those at La Ronde.

If necessary, another update will follow by the mid-afternoon today (July 8th) for wind direction.

Trav.


Posted: Jul 8, 2017 17:06:38

According to the projection shown by the radar of MeteoMedia, a line of rain/heavy rain would move through La Ronde area around 8:00-8:30pm. I hope that it is going to change for the best.

Fred


Posted: Jul 8, 2017 18:07:19

Hi Fred,

It is quite possible, as isolated convective rainfall should continue up to about sunset - potentially a little after.

Simulated radar, while useful, can often have difficulty in projecting the character and distribution of convection-related precipitation, mostly because of the scale at which convection occurs, as well as its complexity. As a result, these simulations are often subject to change for any specific time frame. The assumption of continued convective rainfall development over the next few hours, though, is consistent with the dynamics in place, just that the actual location of the rainfall is uncertain.

Also, I would reduce wind speeds slightly this evening to 8-11 km/h (same directional tendency), so periods of smoke accumulation are still quite possible (mostly during times of larger activity and if smoke-rich products are extensively used), especially with continued borderline moderate-high humidity. The smoke should be moving somewhat gently.

Trav.


Posted: Jul 13, 2017 23:51:52

An area of high pressure is expected to drift East/SE through the day Saturday (July 15th) and lead to mostly fair weather conditions. By contrast, a weak low pressure system will more favorably occupy the early-morning hours of the day and lead to more extensive cloud coverage and a sparsely distributed convective rain showers, but more breaks in the cloud deck will emerge by late-morning and onward.

Maximum temperatures for the greater Montreal area should be 25-26 C, with high (not very high) humidity. This moisture level should generate a humidex of 31-32 C. By the late-evening period, including display time, temperatures should fall to 21-22 C, but with continued high humidity, a humidex of 26-27 C is likely. Thus, this should be a warmer and a little more humid evening than what was observed for the Italian display. Skies should be mostly clear, though some weak lift in the area should generate a few isolated clusters of cumulus.

Winds are projected to be largely light for the day, beginning as NNE for the morning period and transitioning to WSW for the early-afternoon. SW tendencies then develop by the late-afternoon to early-evening period, and then potentially SSW by late-evening (this will have to be monitored). Speeds of 12-16 km/h are likely during the afternoon period but 9-12 km/h for the evening, especially late-evening. As such, smoke should be moving fairly gently to the right of the La Ronde audience, although right-hand sections may receive some smoke, typically smoke from high-level shells. Due to continued high humidity, a few periods of smoke accumulation are possible, but mostly along low- to mid-levels, and mostly towards right-hand sections of the display, notably during more active sections.

Another update to follow later tomorrow evening, or during the pre-dawn of July 15th.

Trav.


Posted: Jul 15, 2017 01:24:16

Information presented in the above posting are still largely applicable. Therefore, here are the weather conditions projected for the greater Montreal area for Saturday, July 15th:

Temperature/Humidity

A SW flow will be strengthening through the day, and coupled with more periods for solar heating by the late-morning to early-afternoon, maximum temperatures should reach 26-27 C, with high humidity (at times borderline high-very high). Thus, a humidex of 33-34 C is still favored. By the late-evening, including display time, temperatures drop to 22-23 C, with continued high humidity. This will make it feel like 29 C.

Precipitation

Due to the aforementioned area of weak low pressure, some early-day convection will be possible during the morning period, with extensive cloud coverage and sparsely distributed light rain showers. By late-morning (near noon), more breaks in the cloud deck should emerge and allow for the sun to break through. By the evening, large clear breaks should continue, accompanied by clusters of low-level cumulus, alto-cumulus, as well as cirrus. The thunderstorm/convective rain shower risk will resume by Sunday, July 16th.

Wind

Winds are still expected to be light through most of the day, notably the morning period. By the early-afternoon, a SW flow should develop and continue into the evening period. Speeds of 8-11 km/h are expected during the morning hours (from the North to NNW) but increase to 12-16 km/h (so, slightly breezy) for the late-afternoon to evening (from the SW). As such, the smoke should be moving mostly to the right of the La Ronde audience, although extreme right-hand sections could receive accumulations (mostly overhead smoke from high-level shells due to a more WSW component at those altitudes). Due to high humidity, some periods of smoke accumulation will be possible, mostly during times of higher activity, and typically focused towards right-hand sections of the display along low- to mid-level. That said, the smoke should be moving at a reasonable pace, which is important at these moisture levels.

If it becomes necessary, another update will follow by the mid-afternoon of today (July 15th), mostly to address wind direction, wind speed and cloud coverage extent. If not, then what is stated in this posting will still apply.

Trav.


Posted: Jul 17, 2017 23:36:41

A developing circulation of very warm and humid air will affect S. Ontario to S. Quebec by July 18th and persist through to most of July 21st. As such, Wednesday, July 19th will be a part of this tropical-like pattern, with very warm to locally hot temperatures and borderline high to very high humidity. At the same time, however, a weak cold front and accompanying shortwave trough will be advancing towards E. Ontario to extreme S./SW Quebec later in the day and could generate scattered thunderstorms/convective rainfall during the late-afternoon to early-overnight period.

For the greater Montreal area, maximum temperatures of 28-29 C are expected, with mostly borderline high to very high humidity, creating a humidex of 35-36 C. Temperatures decline to 23-24 C by late-evening, but with continued high humidity, a humidex of 29-30 C is likely. If rainfall occurs, then temperatures will more favorably drop to 19-20 C. Skies should be partly cloudy during the evening, mostly consisting of large clusters of vertically developed cumulus.

Winds are typically from the SW during the day (except SSW for the morning), which is likely to persist into the evening. The overall flow resembles that of the Polish display, so the smoke should be moving reasonably quickly towards mostly right-hand sections of the La Ronde audience. However, note that the overhead smoke from higher-level shells could be moving more directly towards right-hand sections of the audience and partially central sections. Also note that if thunderstorms/convective rainfall are in the area, the wind would more likely shift towards the audience (mostly left-hand sections). Speeds of 11-14 km/h are likely for the evening period (including display time). Smoke accumulations should be mostly focused to the right-hand sections of the display, along low- to mid-level. Breezier SW winds (19-24 km/h – occasional gusts of 31-34 km/h) should be present for the mid-afternoon.

The thunderstorm risk will have to be monitored. Although solar heating should be ample, along with rich surface moisture, the degree of lift is not entirely clear, casting uncertainty in the overall convective coverage – this is especially the case for the evening period. However, latest data analysis suggests dynamics supportive of scattered thunderstorm development by the mid- to late-afternoon, with some thunderstorm sustenance beyond sunset. Given this, I would, at this point, assign a 40% probability of precipitation for the mid-afternoon to early-overnight time frame for this general area (greatest likelihoods to the NW of the island). Thunderstorms should typically be non-severe, but a few isolated stronger thunderstorms will exist.

Another update to follow late tomorrow evening (July 18th) to pre-dawn July 19th, mostly to address the thunderstorm risk.

Trav.


Posted: Jul 19, 2017 01:21:27

Details mentioned in the above posting are still largely applicable. As such, here are the predominant weather conditions for the greater Montreal area for Wednesday, July 19th.

Temperature/Humidity

Maximum temperatures of 27-28 C are expected, and values drop to 23-24 C by late-evening, including display time. With borderline high to very high humidity, a maximum humidex of 35-36 C should occur, and by the late-evening, a humidex of 31-32 C is likely. Should rainfall occur, temperatures should fall to 20-21 C.

Precipitation

A weak surface cold front and shortwave trough will eject SE through the day and affect extreme E. Ontario to extreme S./SW Quebec by the mid-afternoon. Latest and recent model solutions suggest somewhat restricted lift associated with the cold front, but lift with the shortwave trough appears strong enough for a scattered thunderstorm/convective rainfall distribution for these regions (40% probability of convective rainfall/thunderstorms) - this is mostly applicable for the mid-afternoon to about sunset, when lift appears maximized with this feature. Beyond sunset, forcing for ascent weakens with the eastward progression of the trough, so the overall convective coverage should become sparsely distributed (30% probability of convective rainfall/thunderstorms). Thus, the focus will be up to sunset into slightly the early-evening. Greatest likelihoods for convective rainfall during the forecast period appear greatest to the NW and North of the island. Thunderstorms are largely expected to be non-severe, but a narrow window of opportunity for isolated stronger storms will exist during the mid- to late-afternoon period, especially NW/North of the island. Partly cloudy skies are typically expected for the evening, with large clusters of defined cumulus. Distant lightning will also be possible.

Wind

Winds should exhibit predominantly SW tendencies throughout most of the day (except SSW for the morning period). That said, directional tendencies could shift to WSW by late-evening due to the influence of the cold front at the time. Wind speeds are expected to be breezier through the late-morning to evening period (not just the mid-afternoon), at 17-21 km/h (occasional gusts of 29-34 km/h). By late-evening, wind speeds should slightly weaken, to 13-17 km/h, so slightly breezy. As such, under continued borderline moderate to high humidity, the smoke should be building relatively quickly (especially during more active sections of the display) but moving sufficiently. The smoke should also be moving more directly towards right-hand and partially central sections of the La Ronde audience – this is particularly true for overhead higher-altitude smoke. Accumulations should be mostly focused towards right-hand sections of the display, along low- to mid-level. If convective rainfall/thunderstorms are in the area, then the smoke could turn towards the audience more directly, but mostly towards left-hand sections of the audience, given storm motion.

If necessary, I will post subsequent updates here into the afternoon today (July 19th) concerning (deep) convection and wind direction/speed.

Trav.


Posted: Jul 19, 2017 16:24:38

Information previously presented above holds constant. Wind direction is still expected to more consistently transition to WSW into later this evening, but speeds are shown to be a little lighter at the time, at 8-11 km/h, from their breezier nature throughout most of today. As such, the smoke (at all altitudes) should be blowing somewhat gently towards right-hand and central sections of the La Ronde audience, which could cause the display to frequently appear murky as it develops. With borderline high to very high humidity, some periods of smoke accumulation will be possible (depending on the overall pace of the show).

Scattered convective rainfall development is still expected until especially sunset to a little into the early-evening (brief light rain showers have been reported this mid-afternoon on sections of the island). A few thunderstorms could also still form in the general area over the coming hours. Partly cloudy skies are also favored for the late-evening, with larger clear breaks. Convection should continue through the evening, but the rain showers should still become much more isolated.

Trav.


Posted: Jul 20, 2017 12:52:40   Edited by: Enkil

Smoke, was there any reason why the wind was from SE instead of SW last night? Smoke was blowing on the left-hand and central sections. I think the same thing happened last Saturday (or the previous one). I always rely on your posts to go to a spot in the park where I can avoid the smoke, but something is not right this season. It also looks like the La Ronde audience is cursed with smoke this year.


Posted: Jul 20, 2017 17:18:33

Hi Enkil,

Indeed, central and left-hand sections of the La Ronde audience were affected the most by smoke yesterday evening (July 19th). Although forecast details above suggested that the La Ronde audience would receive smoke accumulations more directly, it was also the left-hand sections that were affected this time (more than right-hand sections). Winds were typically coming out of the WNW just prior to and during the German display to cause the smoke to move towards left-hand and central sections - this was especially notable at higher altitudes, as compared to lower-level smoke accumulations. One reason for the lighter winds and the presence of WNW tendencies in place of the projected WSW was that the decaying thunderstorm that moved through by the late-afternoon (the rain was quite intense in the West Island) slightly disrupted the wind flow for the coming hours. Additionally, the air further moistened, and humidity was already so high prior to that rainfall. This created an environment conducive to rapidly developing and near-stationary smoke accumulation. Consistent with this, in the primary posting above, the following was specified:

Accumulations should be mostly focused towards right-hand sections of the display, along low- to mid-level. If convective rainfall/thunderstorms are in the area, then the smoke could turn towards the audience more directly, but mostly towards left-hand sections of the audience, given storm motion.

Either way, though, with or without convective rainfall, it was likely that the wind would push the smoke towards the audience, with the central sections involved in either scenario.

And, yes, the Italian display had smoke more directed at all sections of the on-site audience, and the smoke was moving mostly towards right-hand sections (and partially central) during the Polish display. The opening show was the most forgiving, but due to a defined convective rainfall, the smoke turned towards the audience during the dying minutes of that display.

So, you're absolutely right: The luck with smoke this year for La Ronde has been lousy thus far, and this Saturday (July 22nd), for France, may not feature the best wind speeds (more details on that to come). It is mostly due to the manner in which weather systems and their accompanying flows of air have affected the area this year so far, notably on fireworks days. Plus, when two displays per week begin to take place, the odds of having unfavorable weather increases for a given display.

Trav.


Posted: Jul 21, 2017 01:28:54

An area of low pressure is expected to move East into this weekend for S. Ontario to S. Quebec. Concurrently, a strong area of high pressure will also be advancing SE and will favorably prevent the warm sector of the low to advance into S. Quebec. As a result, warmer, humid and unstable conditions are expected more into S. Ontario than S. Quebec on Saturday, July 22nd. That said, the low pressure system and its broad warm front will be in fairly close proximity to S. Quebec to allow for a persistent layer of ubiquitous high-level cirrus cloud coverage through most of the day, including into the evening period (possible clearing by late-evening). Rainfall and thunderstorms (some severe) associated with this system should remain farther South and SW of the region, into E. Ontario to S./SW Ontario.

Due to cirrus cloud coverage, the degree of warming should be somewhat restricted. Maximum temperatures for the greater Montreal area on Saturday are expected to be 25-26 C, and humidity levels should be moderate, which is the lowest they have been since July 13th. This will create a humidex of 29-30 C. By late-evening, temperatures should drop to 19-20 C, and humidity levels should fall to borderline low to moderate standards, creating a mild humidex of 21-22 C.

It is not yet entirely clear as to the character of the winds Saturday evening. In the above post, it was briefly mentioned that speeds may be relatively weak/unfavorable by late-evening, but in other data analyses that were examined, the speeds opposingly appear rather breezy into the late-evening. These differences may be due to some difficulty in the models’ ability to resolve the actual interaction between the high pressure and low pressure systems for the time frame in terms of pressure gradient intensity. At this point, directional tendencies seem to be favoring NNE to even NE by late-evening (with speeds of 12-16 km/h). This would favor the smoke to move adequately towards the bridge, mostly those sections bordering the park. Some sections of Notre-Dame Street could also be affected. Rapid smoke accumulation is not favored in this environment, but wind velocity will have to be monitored in coming model runs.

Another update to follow late-day today (July 21st) or during the pre-dawn of July 22nd.

Trav.


Posted: Jul 22, 2017 02:02:14

Details mentioned in the above posting are still largely applicable. As such, here are the predominant atmospheric conditions for the greater Montreal area for today, July 22nd.

Temperature/Humidity

Maximum temperatures are likely to reach 25 to 26 C this afternoon, with values dropping to 19-20 C by the late-evening period. Humidity should be moderate throughout the day (as compared to the borderline high to very high concentrations featured by the July 15th-July 21st period), so this will generate a maximum humidex of 28-29 C. For the late-evening, a mild humidex of 22-23 C is favorable.

Precipitation

As mentioned in the above posting, an area of low pressure will drift closely to our South and will eventually stall somewhat (setting the stage for a cool and wet start to the work week). Meanwhile, an area of high pressure will eject SE, which will keep the low pressure system farther South. The low’s stationary front will be positioned closely to the South, but little lift is shown North of this feature. That being said, a shortwave trough will also be migrating East into the early- to mid-afternoon period and could generate some sparsely distributed light rain showers. Lift associated with this trough does weaken into the late-afternoon, so rainfall generation should subside by then. Do to some lift, skies should be partly cloudy during most of the day, with mostly mid- to high-altitude clouds and sunny breaks between them. Further clearing should occur by the late-afternoon, with just a few isolated patches of cirrus.

Wind

With the positioning of the high and low pressure systems in the area, winds are expected to largely be light to very light throughout most of the day (6-9 km/h), especially during the morning to early-afternoon period. However, winds do gain some speed by the mid-afternoon, increasing to 10-13 km/h (including through to the late-evening). Winds begin as NE during the morning and transition to Westerlies into the early-afternoon period. As the pressure systems move farther East, though, surface and near-surface winds should begin evolving into more of a North to NNE tendency into the late-evening (including display time). As a result, the smoke (at all altitudes) should be moving fairly gently, but adequately, clear to the left of the La Ronde audience (right for those on Notre-Dame Street) and head towards adjacent sections of the bridge overlooking the park. This will obscure viewing from those sections of the bridge and also could sometimes affect viewing for those at the Old Port. Some periods of smoke accumulation are possible, but typically during the more active sections of the display, and along low- to mid-level. Accumulations will also be mostly focused towards left-hand sections of the display, but the smoke should not be building up rapidly due to much lower moisture/humidity levels.

If necessary, another update will follow by the mid-afternoon today (July 22nd) to address wind speed and direction.

Trav.


Posted: Jul 22, 2017 17:07:26

Details mentioned in the above posting still hold constant. I would just reduce wind speeds slightly for this evening, to 5-8 km/h, so the smoke should be moving (very) gently to the left of the La Ronde audience due to NNW tendencies. At times, though, it is possible that the smoke could be near-stationary, so there would be no apparent direction in those situations. Periods of extensive smoke accumulation are possible (depending on the overall nature of the display). Moderate humidity could also boost smoke thickness somewhat.

I would also increase temperatures slightly for this evening to 20-21 C, with a mild humidex of 23-24 C. Skies should be mostly clear this evening, with a few clusters of mid- to high-altitude clouds.

Trav.


Posted: Jul 25, 2017 01:26:08

An area of high pressure will move East towards the North Atlantic into the day Wednesday (July 26th). As it does, and with the aid of low pressure farther West, this will circulate a warm and progressively more humid air mass into S. Ontario to S. Quebec for both July 26th and especially July 27th.

With this circulation, a more Southerly to SSW flow will govern these regions, including the greater Montreal area, for the day Wednesday. Humidity, while lower during the morning hours, will increase to borderline moderate to high standards by the mid-afternoon period. Some lift in the area will favorably allow for a persistent layer of cirrus cloud coverage mostly into the afternoon period because of an approaching warm front associated with the aforementioned low pressure system. Cloudiness will restrict how much heating actually occurs, so maximum temperatures of 24-25 C (humidex of 28-29 C). Cloud coverage should further increase towards lower altitudes into the late-afternoon to mostly evening period, with some preliminary light rain showers possible near midnight and especially into the overnight as the air further saturates and lift increases. The timing of initial rainfall development will have to be monitored, but skies should be cloudy for the evening. This will keep temperatures from dropping off too much, so late-evening temperatures should be 20-21 C (humidex of 25 C).

Wind speeds are expected to be generally light through most of the day, but they will increase into the mid-afternoon period, at 13-17 km/h (slightly breezy). Speeds decrease to 8-11 km/h for the evening, and directional tendencies throughout the day are largely in the form of SSW to sometimes straight Southerlies. SSW is more favorable into the evening. As such, the smoke should be moving reasonably quickly (notably higher-altitude smoke) and clear to the right of the La Ronde audience (left for those on Notre-Dame Street). Smoke accumulations should not be overly high, but they will be more focused at right-hand sections of the display (left for those on Notre-Dame Street).

Another update to follow by either late-day July 25th or pre-dawn July 26th, especially to address possible late-evening light rain showers.

Trav.


Posted: Jul 25, 2017 23:45:39

Details outlined in the previous posting still hold constant. As such, here are the most likely weather conditions for the greater Montreal area for Wednesday, July 26th.

Temperature/Humidity

Due to a SSW circulation and some early-day periods for solar heating, maximum temperatures of 24-25 C are expected. Humidity should increase to high (not very high) standards and will likely induce a humidex of 29-30 C. By late-evening, temperatures fall to 21-22 C, with a humidex of 26-27 C due to continued high humidity.

Precipitation

As mentioned in the previous posting, mostly cloudy skies are expected through most of the day, beginning into the early-afternoon period. Skies should be mostly sunny for the morning, but more uniquitous high-level cirrus should make an appearance into the afternoon (with continued breaks for sunshine), followed by increasing coverage of lower-alitude cloudiness (cumulus to alto-cumulus) as the atmosphere saturates from the top-down. This increased cloud coverage is due to an occluded front moving in from the West, and increased lift ahead of this boundary will eventually cause bands of light light rain showers to begin forming during the late-evening, typically near midnight. Some preliminary scattered light rain showers and drizzle will also be possible prior to midnight (including during display time), but mid-levels of the atmosphere appear dry enough to cause most of the rain to evaporate prior to reaching the surface at the time. I would assign a 40% probability of light rain/drizzle for the late-evening period, but 80% near midnight. Thunderstorms become increasingly possible for the late-afternoon of July 27th.

Wind

Winds are likely to be SSW to occasionally straight Southerly for the day. Speeds should be light, at 8-11 km/h during the morning but increase to 15-18 km/h (slightly breezy) for the mid-afternoon. Speeds diminish slightly to 9-13 km/h for the evening (so, still a touch breezy), including display time. As such, the smoke should be moving clear to the right of the La Ronde audience (left for those on Notre-Dame Street), with smoke accumulations mostly focused to the right. The smoke should also be moving reasonably quickly, even though it will build somewhat quickly under the higher humidity. That said, the smoke will be moving a little more quickly with respect to higher altitude smoke, which should be advancing from overhead to extreme right-hand sections of the La Ronde audience.

Another update to follow, if necessary, into the mid-afternoon of tomorrow (July 26th).

Trav.


Posted: Jul 26, 2017 16:25:13

Latest data analysis indicates that wind direction should shift to more SW from the current overall SSW pattern featured by this afternoon and morning (July 26th), so the smoke should be moving fairly quickly, at all altitudes, towards (extreme) right-hand sections of the La Ronde audience. Speeds of 12-16 km/h are favored (still slightly breezy).

Also, it was not specified above, but if there are some light rain showers/drizzle, then late-evening temperatures of 19-20 C will be more favorable. Chances for light rain showers or drizzle are the same for late this evening, so have an umbrella or some form of covering equip, even if it does not actually rain during the display. Dry air aloft should induce some evaporation of preliminary light rain/drizzle, but the light rain should eventually make it to the ground by mid- to late-evening (again, especially closer to midnight).

For all other information, please refer to the above posting.

Trav.


Posted: Jul 28, 2017 00:09:26   Edited by: Smoke

A broad area of high pressure will drift SE by today (July 28th) and will be the governing system for this weekend across S. Ontario to S. Quebec. This system will keep maximum and minimum temperatures below average but still generally pleasant across these regions, with plentiful sunshine and low humidity levels.

For the greater Montreal area, maximum temperatures of 22-23 C are expected by the mid-afternoon of July 29th, and with low humidity, the humidex factor will be negligible (maximum humidex of 24 C). By late-evening, temperatures will be more liable to fall quicker due to progressively lighter winds, clear skies and low humidity. Temperatures of 17-18 C are favorable, so it will be a touch on the cool side (especially when the gentle breezes hit you). No rainfall is expected, and high pressure will keep an Atlantic low to the SE, which will affect New England with persistent rainfall and embedded thunderstorms.

With the aid of the aforementioned Atlantic low to the SE, winds are likely to be in the form of NNE to straight Northerlies (occasionally NE) throughout the day. Speeds, however, do vary, from gustier tendencies (17-22 km/h – occasional gusts of 27-33 km/h) during the late-morning to mid-afternoon to weaker speeds (9-12 km/h) developing by the late-afternoon. As a result, smoke from the fireworks should be moving clear to the left of the La Ronde audience (right for those on Notre-Dame Street) at a reasonable pace (slightly quicker movement with respect to very high-altitude smoke). Smoke accumulations should be light and moving towards sections of the bridge bordering the park. The display may appear slightly hazy for those viewing from the Old Port.

Another update to follow by either later today (July 28th) or pre-dawn July 29th.

Trav.


Posted: Jul 29, 2017 01:58:35

Weather information presented above is still largely applicable. However, there are notable changes in wind speed that will be addressed below. Here are the dominant conditions for today (July 29th) for the greater Montreal area:

Temperature/Humidity

With intense solar radiation, maximum temperatures should reach 24-25 C by mid-afternoon. Humidity levels will be low, so a very mild humidex of 25-26 C is favorable. By late-evening, temperatures fall to 20-21 C (a little warmer than previously outlined). Humidity levels do increase slightly to borderline low to moderate, so a slight humidex of 22-23 C is favorable. The UV will be high for the late-morning to afternoon.

Precipitation

No precipitation is expected due to high pressure governing the region this weekend. Lift is expected to be very weak, so clear skies are favorable throughout the day, including the evening. A few isolated cirrus and fair-weather cumulus clouds should make an appearance during the afternoon to early-evening.

Wind

Winds are still expected to be in the form of NNE throughout the day. However, wind speeds should remain light, including during the mid-afternoon, at 9-13 km/h (slightly breezy during the mid-afternoon, at 12-16 km/h). By evening, wind speeds reduce further to very light to occasionally calm standards (3-6 km/h). One reason for this is the reduced pressure gradient between the low to the SE and this high pressure system. This casts some uncertainty as to overall wind direction due to localized effects becoming more important at very light speeds. That said, NNE to NE tendencies should be present for the evening, so the smoke will likely be moving very gently to the left of the La Ronde audience (right for those on Notre-Dame Street) and towards bordering sections of the bridge. At times, the smoke may appear near-stationary as the display unfolds, but particularly thick accumulations are not expected due to lower humidity levels. Accumulations should be most present towards left-hand sections of the display (right for Notre-Dame Street spectators). The display may often appear hazy at its left-hand sections, and especially for those viewing from the Old Port and bridge.

*Another update to follow by the mid-afternoon of today (July 29th) to address wind velocity.

Trav.


Posted: Jul 29, 2017 16:53:40

No significant changes to forecast details presented in the above posting. However, for wind velocity, it appears that more NE to even occasional ENE directional tendencies are favored for this evening, with continued very light speeds of 3-6 km/h (occasionally calm conditions into the late-evening). As such, the smoke should be moving very gently (possibly, at times, near-stationary) more towards right-hand sections of Notre-Dame/Viger Street, that is, those sections closest to the bridge. Humidity should remain low, so, as mentioned above, excessive smoke build up is not expected. The display could also still appear hazy frequently towards left-hand sections of the display (right for those on Notre-Dame Street), in particular, especially for those viewing very close to the bridge on Notre-Dame Street, and towards the Old Port. High-altitude smoke, though, should be moving a little faster (same general direction) than that at lower-altitudes.

Although speeds are very light this evening, the Easterly component in the wind fields should benefit viewers at La Ronde the most.

Trav.


Posted: Aug 3, 2017 23:59:15

A strengthening area of low pressure and amplified mid-level trough will advance East/NE into tomorrow (August 4th) and will continue to generate instability into most of the day Saturday (August 5th). For extreme S./SW Quebec, a sharp cold front, along with lift associated with the trough, could yield scattered strong to severe thunderstorms late-day August 4th into early pre-dawn August 5th. Thunderstorms and convective rainfall should continue into the morning of August 5th. Although the cold front will move off to the East of the island of Montreal by late-Saturday morning, the aforementioned trough will continue to provide the lift necessary for scattered convective light to moderate rain showers (and isolated non-severe thunderstorms) for the afternoon to early-evening period (40% probability of rainfall). More periods for sunlight should emerge by the late-morning to afternoon period as a result of partly cloudy skies, but this, combined with high humidity levels, will amplify instability. Skies should be partly cloudy for the evening.

For the greater Montreal area, temperatures should reach 23-24 C by mid-afternoon Saturday. With continued high humidity, a maximum humidex of 29-30 C is favorable. By late-evening, temperatures drop to 19-20 C, but with moderate humidity, so a mild humidex of 22-23 C will be applicable.

Winds are expected to be fairly gusty through the day, first from the SSE to South during the morning, and then transitioning to SSW to eventually SW behind the cold front (SW by late-afternoon, and potentially even WSW by late-evening). Speeds of 24-28 km/h are projected for the late-morning, late-afternoon and evening periods (somewhat weaker during the late-morning to mid-afternoon). Occasional gusts of 38-43 km/h are possible during these times, so this will have to be monitored in upcoming data analyses. As such, smoke accumulations should be light and moving quickly towards right-hand sections of the La Ronde audience.
Smoke at higher altitudes should be moving somewhat more rapidly, and in the same direction.

Another update to follow late-day tomorrow (August 4th) or pre-dawn August 5th, with subsequent updates, as necessary into the afternoon of August 5th.

Trav.


Posted: Aug 5, 2017 02:14:00

Conditions mentioned in the above posting are still largely applicable. As such, here are the predominant weather conditions for the greater Montreal area for today (August 5th).

Temperature/Humidity

Maximum temperatures of 23-24 C are expected by the mid-afternoon period. With borderline high to very high humidity, a humidex of 29-30 C is applicable. By the late-evening, temperatures fall to 18-19 C, along with a drop in humidity to moderate levels, so a mild humidex of 21-22 C is likely. The drop in humidity becomes more noticeable by a little prior to sunset.

Precipitation

As mentioned in the above posting, a broad trough will affect extreme E. Ontario to extreme S./SW Quebec through most of today with scattered light to moderate convective rain showers (40% probability of rainfall) and isolated non-severe thunderstorms (30% probability). There does appear to be a narrow window of opportunity, however, for a few organized thunderstorm clusters during the early- to mid-afternoon, as periods of sunlight emerge by near lunch time and onward due to partly cloudy skies. Periods of rain and continuous cloud coverage are most favored during the morning hours, but some instability induced by solar heating and rich surface moisture could, again, encourage a few thunderstorms and convective rain showers for the afternoon period. Following sunset, convection should largely subside as lift associated with the trough pushes farther East and the air stabilizes, leaving clusters of residual cumulus clouds and clear breaks.

Wind

Winds begin in the form of Southerlies and SSE for the morning to early-afternoon. By mid-afternoon, directional tendencies become SW, which will persist into the evening and possibly become even WSW by late-evening. Speeds are still to be monitored, however, as gusts could be reach 38-44 km/h (sustained at 23-27 km/h) through the morning hours, and from the mid-afternoon to evening period. This is due to a tigthening pressure gradient, as well as the nature of this area of low pressure. As such, smoke from the fireworks should be pushing very quickly towards right-hand sections (partially central) of the La Ronde audience. Smoke accumulations should be light. Due to wind gusts hovering around the 40 km/h threshold, it is possible for brief delays in commencing the display, especially since the wind will be directed towards portions of the La Ronde audience.

*Another update to come to address wind speed and direction by the mid-afternoon of today (August 5th).

Trav.
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