First Significant Severe Weather Event of the Season Strikes Oklahoma
This past Wednesday severe storms erupted across much of Oklahoma bringing with them very large hail and even tornadoes. It was the biggest severe weather day this year in the states, up to now (but many more are to come). A surface low was located in central Oklahoma with dryline extending southward, cold front crashing south from the north side of the low, and a warm front extending northeastwards from the low. There were two main focus areas for the storms – along the dryline and near the triple point/along the warm front. A moderate risk was issued by the SPC and covered the areas of concern. The outlook also included a 5% tornado risk with 45% hatched hail probabilities. A moderate jet streak was in place with dewpoints in the high teens, which together provided sufficient shear and CAPE for supercells.
As expected, several storms initiated on Wednesday afternoon and grew into supercells. Two supercells were of most concern before storms consolidated into squall lines: one near Tulsa and one near Oklahoma City. The storm that approached Tulsa showed strong rotation on radar early in its lifetime –a tornado warning was able to be issued well before it hit the city. By the time it reached a suburb of Tulsa, Sand Springs, a tornado touched down and tore through a trailer park. In addition to that, hail, the size of tennis balls, were reported in Tulsa’s metro region as the supercell’s hail core passed over the city. The tornado (preliminary rating of EF-2) injured over a dozen people and one person lost their life in the trailer park.
Aerial view of the damage to the trailer park in Sand Springs. (Source: Tulsa World)
The Oklahoma City storm fired off the dryline initially but then got undercut by the cold front – meaning it had little tornado potential. Interestingly enough, the supercell was able to catch up to the cold front and interact with it, enhancing the vorticity in the area – likely being a contributing factor to the formation of the tornado. With this mesoscale interaction playing a significant part in the cause of the tornado, not much lead time was provided to residents (it happened quickly). Unfortunately the twister (preliminary rating of EF-1) touched down in the city of Moore, OK which got hit by a devastating twister in 2013 and had seen two other strong tornadoes since 1999. No injuries were associated with this one, thankfully.
Compilation of radar images before/during/after the Moore tornado showing the storm’s interaction with the cold front. (Image compilation by @VORTEXJeff / Twitter)
The pattern could become active again by the middle of next week, but it is still too early to be certain. April to late May is typically the busiest time of the year for severe weather in the Southern US Plains, due to plentiful moisture before the jet stream shifts further north for the summer.
This photo of a funnel cloud was taken just southwest of Winnipeg.
Welcome to our summary of the 2014 thunderstorm season across Southern Manitoba! This post will summarize these statistics and compare this year’s thunderstorm season to the last couple seasons. In case you are curious, a brief explanation of how I gathered these statistics can be obtained by following this link.
Thunderstorm Days
The number of days with thunderstorms across southern Manitoba broken down into 6 regions. Includes the date of first thunderstorms and last thunderstorms.
In total, there were 94 thunderstorm days across southern Manitoba in 2014 (southern Manitoba being defined as the area shaded in the map above). This was slightly higher than in 2013 (89 thunderstorm days) but still much lower than in 2012 (~ 109 thunderstorm days). This is mainly the result of a late spring and thus, a late start to the season in both 2013 and 2014. 2012 featured an early spring with numerous thunderstorm events in March and April. This year, no thunderstorms occurred in March and only 2 thunderstorm days occurred in April. In fact, southeastern, eastern and Interlake portions of southern Manitoba did not see their first thunderstorm until the third or fourth week of May, at least a month later than usual. Winnipeg didn’t get its first thunderstorm until May 20, the 8th latest first thunderstorm on record since 1953.
The distribution of thunderstorm days, as seen in the map above, was fairly uniform across southern Manitoba overall. Similarly to 2012 and 2013, the region east of Lake Winnipeg saw notably less thunderstorm activity.
Interestingly, there was a thundersnow event in January! Although lightning detection products did not record the lightning, lightning was reported by residents west and southwest of Winnipeg on the evening of January 15; more specifically between Carman and Winkler. This was associated with a very strong cold front behind a potent Alberta Clipper. This clipper also brought record winds and high temperatures across the Prairies. Unfortunately, I could not find any data on winter thunderstorm activity in Manitoba historically. The only other occurrence of lightning in January I could find was a report in the Daily Free Press of lightning on January 16, 1876 (Penziwol, 2004). This is not to say that lightning has never occurred in January since then, but that is the only other report I could find. Nonetheless, this year’s thundersnow event was extremely rare for Manitoba.
In Winnipeg, 23 thunderstorm days occurred at the airport in 2014. Although this is the most since 2010, it is still below the normal of ~26–27 thunderstorm days. In fact, we have not had an above normal season since 2007. The last thunderstorm recorded was on September 8, tying for 10th earliest last thunderstorm since 1953. This puts the season at 112 days long, the 5th shortest on record. However, this statistic is a bit misleading. Thunderstorms did occur in southern parts of the city 3 times after September 8, including 2 events in October. I recorded 27 thunderstorm days here in South St Vital this year and the season lasted 156 days.
Severe Thunderstorm Warning Days
The number of days in which severe thunderstorm warnings were issued through 2014 in Manitoba, broken down by forecast region.
In total, there were 34 days with a severe thunderstorm warning issued in southern Manitoba. This is similar to 2012 but much less than in 2013 (45 severe thunderstorm warning days). The first warning was issued on May 24 and the last on September 8, putting the season at 108 days long. This is a tad less than in 2013 (110 days long) and 2012. As has been the case the last few years, southwestern Manitoba saw the most severe thunderstorm warning days in 2014.
Tornadoes
The number of days tornado warnings were issued across Manitoba in 2014, broken down by forecast region.
There were 4 tornado warning days in 2014, half the number in 2013 (8 days) but double the number in 2012 (2 days). The Red River Valley area saw the most. In fact, the warning zone southeast of Winnipeg, which Steinbach is situated in, saw 3 tornado warning days, the highest of all warning zones in Canada this year. However, only one of these warnings actually produced a confirmed tornado (an EF–0 southeast of La Salle on July 26).
From what I could find, 4 EF–0 tornadoes were confirmed in Manitoba this year. However, it is likely that there were more (many go unconfirmed). July 26 was the biggest tornado day of the year with 3 landspout tornadoes confirmed (all EF–0). 2 were in the Interlake near Waterhen and the other was southeast of La Salle.
A tornado might have touched down (unconfirmed) southwest of Winnipeg July 5. Part of the A Weather Moment team (Scott, Matt, Julien & Kyle) watched the storm as it evolved and managed to capture at least 2 funnel clouds. One of these is seen in Matt’s funnel cloud picture at the top of this post. After reporting this funnel to Environment Canada, a tornado warning was issued for the City of Winnipeg.
Monthly Frequency
Thunderstorm-related days per month (thunderstorms, severe thunderstorms and tornadoes) for Southern Manitoba in 2014.
For the first time since I started gathering these statistics in 2010, the busiest month of the year for thunderstorm activity across southern Manitoba was in June. The maximum is typically in July, but this year there was an unusual local minimum in activity in July with just 18 thunderstorm days. Residents in southwestern Manitoba were especially hard hit in June with multiple rounds of heavy thunderstorms and rains mid-late month. Over 150 mm of rain fell in the heaviest hit areas in just a period of 2 weeks. 251.6 mm of rain fell in June in Brandon, the rainiest June on record since 1890. 219.8mm of this fell in just the last 12 days of the month. Extensive overland and river flooding occurred as a result, as many of you likely still remember well.
If interested in comparing, follow these links for the 2013 and 2012 graphs: 2013, 2012.
Reference Cited
Penziwol, Shelley. (2004). Storm Signals: A History of Weather In Manitoba. Great Plains Publications. Winnipeg, Manitoba. Page 3.
Above-normal temperatures[1] will continue through the remainder of the week as a southwesterly flow aloft continues to pump relatively mild Pacific air over the Prairies.
Wednesday
17°C / 8°C
Increasing cloud with a chance of showers
Thursday
15°C / 7°C
Mainly cloudy
Friday
16°C / 5°C
Some morning cloud, then sunny
Unsettled Wednesday
Today will be the most unsettled day of the week thanks to a (very) weak cold front pushing eastwards across the Red River Valley today. A fairly sunny start to the day will become more mixed by mid-day with a slight chance of shower activity in Winnipeg mid-day into the early afternoon. It seems most likely that the activity will remain to the east of Winnipeg, with showers or even thunderstorms almost a certainty in the Whiteshell southwards to the US border.
Precipitation forecast for this afternoon from the Canadian RDPS model.
The American NAM weather model has been an outlier for several runs in a row, producing a fairly potent band of showers and thunderstorms over the western Red River Valley and pushing eastwards through the day. Given the weak surface forcing, mediocre moisture and the rate and evolution of the upper-level destabilization, it seems that the NAM is probably over-doing things and not a likely forecast. It’s worth mentioning here as an outside possibility, though, given its consistency in producing that outcome.
Other than the showers, strong southerly winds at 40 gusting 60km/h will taper off this afternoon behind the weak cold front as they shift to westerly at around 20km/h. The temperature will climb to around 17°C today.
Skies will clear out this evening as the temperature drops near 8°C for the overnight low.
Pleasant End to the Week
Thursday and Friday will both be pleasant fall days – especially for late October. Dry weather will be the name of the game for both days with highs in the mid-teens and fairly light winds. Some cloud will push across the Red River Valley on Thursday night but otherwise things will be mainly sunny/clear. The temperature will dip to around 6 or 7°C on Thursday night and a bit cooler – near 5°C – on Friday night.
Heading into the weekend, the weather continues to look pleasant with highs in the teens, no real threat of rain and plenty of sunshine. Enjoy!
Normal daytime highs for this time of year sit around the 8°C mark. ↩
Temperatures will be on the slide as a low pressure system bringing unsettled weather today draws in cooler air behind it, plunging southern Manitoba into yet another spell of unseasonably cool weather.
Wednesday
17°C / 10°C
Cloudy with a few showers
Thursday
16°C / 5°C
Mainly sunny, showers likely in the evening
Friday
10°C / 1°C
A few sunny breaks, otherwise mainly cloudy with light showers
Wednesday
Today will be a mainly cloudy day here in Winnipeg with rather pleasant temperatures – highs will be around 16 or 17°C – alongside a brisk southerly wind to 30–40km/h. The warmer temperatures are thanks to a strongly wound-up low pressure system lifting northwards near the Manitoba-Saskatchewan border. It will spread an area of rain through Manitoba, but the bulk of it should be isolated along the main deformation axis of the system, sliding northwards through SW Manitoba and Parkland Manitoba into the northern half of the province. Scattered showers will likely be seen through the Red River Valley, but it doesn’t seem like much organized precipitation will develop; as such, rainfall amounts should remain fairly low over the region.
Total precipitation forecast by the RDPS from 7AM to 7PM today.
Skies will remain mostly cloudy this evening with a chance for some shower activity continuing until around the middle of the night. Clearing will begin afterwards as we head to a low of around 5°C.
Thursday
Thursday will actually be quite a pleasant day; most of the cloud cover should be off to our east leaving us with quite a bit of sunshine through the day as we head to a high once again around 16°C. By late afternoon, though, skies should begin to cloud up in advance of a potent shortwave barreling down in the northwesterly flow behind today’s system. Showers will develop under the shortwave as it progresses southeastwards with much of the Red River Valley seeing some amount of rainfall before 9PM or so. There is a slight chance of seeing some lightning or small hail in some of the shower activity if it manages to develop intensely enough.
A simulated RADAR image from the NAM depicting the potent shortwave moving through on Thursday.
A brief reprieve will be in store for the middle of the night, but more shower activity is expected to move through later overnight into Friday morning on the back-side of the shortwave. The temperature will dip to around 5°C.
Friday
Friday will start off cloudy with a few remnant showers from the shortwave pulling off to the east. The shower activity should move off relatively quickly, but there’s a slight chance things will linger a little longer if the shortwave stalls out over SE Manitoba. Afterwards we’ll be entrenched in a northwesterly flow with Arctic air spilling southwards into the province. Our temperature will top out around 10°C with some lake-effect drizzle/showers likely in the lee of the lakes.[1]
The Arctic air mass moving in will be the coldest air mass of the season so far in Southern Manitoba. Temperatures will drop to 0–2°C on Friday night under mainly clear skies and a brisk northwesterly wind. Some areas will see cloud streaming off of the lakes, again though where that cloud goes will depend exactly on which way the wind blows.
Cool Weekend Ahead
This weekend will be a cool one as cold Arctic air entrenches itself over the province. Daytime highs will sit in the low teens with overnight lows in the low single digits, perhaps even dipping just below 0°C. Sunday may bring the chance for some shower activity pushing in from the east, but things look rather uncertain at this point.
The wind direction makes it look unlikely that the lake-effect activity will push into Winnipeg; keep in mind that which areas see lake-effect precipitation is extremely sensitive to wind direction. ↩
