Friday, 8 January 2016

9th Warmest December Fitting End to 9th Warmest Year

It was a tale of two seasons in December. The month began remarkably mild with temperatures more typical of October. By mid month, winter made an abrupt entrance as a parade of snowstorms buried southern Manitoba just days before Christmas.

As mentioned, remarkable warmth started December across southern Manitoba. Temperatures exceeded the freezing mark for 8 to 10 days in Winnipeg during the first half of December. December normally only sees 4 days above freezing according to the 1981-2010 normal. 14-consecutive days from the 3rd to 16th never dropped below -9°C at Winnipeg airport, amazing when you consider this is about the normal high in December. One of the warmest days was on December 3 when temperatures reached 7°C downtown and 4°C at the airport. The only record broken during the warm spell was on December 9 when a high of 5.6°C at the airport broke the old record of 5.1°C in 1990.

The warmth was most impressive where there was no snow cover. 3 to 7 cm of snow was leftover from November in the Winnipeg area and this actually kept temperatures lower than they could have been. Areas without snow cover southwest of the city and in southwestern Manitoba saw much warmer temperatures. Many locations reached double digits and in some cases more than once. In Morden, four days exceeded 10°C, three of which were record highs. The high of 14.2°C on December 4 was the third warmest on record in December since 1904. Some thermometers reportedly reached 15°C, more typical of late September or early October. There wasn't a single snowflake on the ground at the time. A similar milestone was reached in Brandon with a high of 11.1°C on the 4th, the third warmest in December since 1890.

The first half of December (December 1 to 15) averaged -3.0°C at Winnipeg airport, the second warmest first half of December on record since 1872. The warmest was in 1913 with an average of -2.1°C.

Winter set in by December 16. Three snowstorms occurred from the 16th to 23rd, dumping 40 cm of snow in Winnipeg. The biggest snowstorm was on the 16th and 17th when about 20 cm fell in Winnipeg. Strong winds helped carve drifts up to two-feet deep in some spots. 18 cm fell on the 16th alone at the official Charleswood station, breaking the old record of 8.4 cm in 1942 for the day. With all the snow in mid December, travel was difficult. Residential streets were difficult to navigate and vehicles were getting stuck in the snow. Thanks to the snowfall, snow depth in Winnipeg sat at 30 cm on Christmas morning, the deepest snow pack on Christmas day in 15 years (since a 30 cm depth in 2000).

In total, 44.0 cm of snow fell in Winnipeg in December, 83% above normal and the 12th snowiest December on record. With an average mean temperature of -8.1°C, it was also the 9th warmest December on record since 1872. This was 5.4°C above normal.

It was a very warm year across southern Manitoba overall. In Winnipeg, 2015 averaged 4.2°C, the 9th warmest year on record since 1872. Highs averaged 10.1°C, tied 7th warmest. This was only the 9th year since 1872 to see highs averaging in the double digits and the 3rd in the last 10 years.

In terms of precipitation, amounts were very close to normal at the airport. However, other parts of the city saw much more precipitation. At my station in south St Vital, there was 544.0 mm of rain, 120.4 cm of snow and 632.3 mm of precipitation.

More details will be provided in a future post on A Weather Moment so stay tuned.

Thursday, 7 January 2016

#4, #3 & #2 - Top 10 Weather Stories of 2015 in the Winnipeg Area

#4 - May Long Weekend Storm System

The strongest low pressure system of the year, a Colorado Low, slammed southern Manitoba during the May Long Weekend. Heavy rain, damaging wind, large waves on the lakes and even snowfall occurred, making for one of the worst May long weekends in recent memory weather-wise.

The rain in Winnipeg began late on Saturday May 16 and continued throughout the entire day on Sunday May 17. In total, 35-50 mm fell in the city. 31.3 mm fell at Winnipeg airport on May 17 alone, breaking the old rainfall record of 22.9 mm in 1903 for the day. The heaviest rains fell southwest of Winnipeg and in southwestern Manitoba. 50-90 mm fell from Morden to Carman to Melita. Significant overland flooding occurred as a result. Many farm fields were underwater.

The rain was accompanied by very strong winds. Winds were sustained between 47 and 63 km/h at Winnipeg airport for 22-consecutive hours, from 6 am on May 17 to 3 am on May 18. Wind gusts were stronger, gusting at times between 80 and 95 km/h. A peak gust of 93 km/h was recorded in Winnipeg. The wind damaged property, caused power outages and uprooted trees. In addition, larges waves and storm surge occurred on Lake Manitoba and Lake Winnipeg. Some local residents on the south shore of Lake Winnipeg said it was one of the worst storms they've seen on the lake.

Behind the system on Monday May 18, snow and strong wind occurred. Temperatures dipped to freezing in the evening on May 17, causing rain to changeover to snow. Snow continued throughout the night, ending in the morning. The cold and wind combined to produce wind chill values of -9. About a dusting to 3 cm of snow fell in Winnipeg, depending where you were. 2.5 cm was measured in Charleswood on May 18 alone, just shy of the old snowfall record of 3.0 cm in 1963 for the day. A snow depth of 2 cm was recorded in the morning observation, breaking the old record of trace cm for the day. The snow melted in the afternon as temperatures rose above freezing. This was the latest spring snowfall in Winnipeg since 2002 when a trace cm fell on May 23 and the latest snowfall accumulation since 1969 when 0.3 cm fell on June 12. Prior to this year, snow had fallen on May 18 only 4 times since 1872. Heavier snow fell west of the city with a swath of 10-15 cm from Boissevain to McGregor to Teulon to the Gimli area.

A full summary of the storm was posted on A Weather Moment.

#3 - Warm and Moist Fall

It was a very warm fall across southern Manitoba (likely is partly thanks to a strong el nino). All three months finished in the top 30 warmest on record since 1872 in Winnipeg: September was 6th warmest, October tied 30th warmest and November tied 16th warmest. As a whole, it was the 4th warmest fall on record since 1872 with an average mean temperature of 7.3°C, tied with 1953 and 2009. Brandon also had a 4th warmest fall on record (since 1890), averaging 6.2°C.

Top 10 warmest falls (Sep-Oct-Nov) in Winnipeg since 1872 (by average mean temperature):
1.  8.6°C (1963)
2.  7.9°C (1931)
3.  7.5°C (1923)
4.  7.3°C (1953, 2009, 2015)
7.  7.2°C (1948)
8.  7.1°C (1914, 1920)
10. 7.0°C (1922)

The warmth in September was already discussed previously in the top 10 series and will not be rediscussed here.

In October, the most significant warmth was during the Thanksgiving weekend. Temperatures reached the low to high 20's on Saturday the 10th and Sunday the 11th. Although Winnipeg didn't break any records, many parts of southern Manitoba did. The warmest temperatures were seen along the US border where records highs near 28°C occurred in Pilot Mound, Morden and Sprague.Winnipeg reached a maximum of 24.6°C on the 11th. Even some weak thunderstorm activity occurred in the evening on the 11th, ahead of a strong low pressure system which produced damaging winds the following day. October as a whole saw 22 days above 10°C, above the normal of 17 days.

In November, warm conditions continued. An incredible 25-consecutive day streak of above normal temperatures occurred from October 26 to November 19. During this time, 10-consecutive days from October 27 to November 5 never dropped below freezing. Warmth and high humidity returned mid November before winter-like conditions arrived. Temperatures exceeded 10°C from the 14th to 16th. A high of 13.1°C on the 15th was just a couple degrees shy of the old record of 15.6°C in in 1939. Unusually high humidity also occurred with dewpoints reaching 9.4°C on the 16th and 9.3°C on the 17th, both daily record highs. These were also the latest occurrences of dewpoint over 9°C on record since 1953. Thanks to the high humidity, a record high minimum temperature of 5.3°C was achieved on November 16, the warmest daily minimum for so late in the year.

In the end, dewpoint temperatures averaged 3.2°C in fall 2015 (September to November). This made it the second most humid fall on record since 1953. September dewpoint temperatures averaged 9.8°C, the third highest on record. November dewpoint temperatures averaged -2.9°C, the highest on record, beating the old record of -3.0°C in 1981.

Thanks to warm conditions, the first accumulative snowfall did not occur until November 18 in Charleswood, Winnipeg's official station for snowfall reports. This was the 4th latest first snowfall accumulation of the season since 1872. It was also a month later than the 1981-2010 normal of October 18. In addition, no snowfall was recorded in October, only the 16th time this has occurred since 1872.

#2 - August 22-23 Severe Thunderstorms and Heavy Rains

Significant thunderstorms and heavy rain pummelled Winnipeg and the surrounding area on August 22 and 23. Due to extreme nature of the event and the large area affected, the event is considered number two in the top 10 series.

The event began overnight on August 22 when severe thunderstorms developed north of a warm front. The bulk of the storms remained north of Winnipeg and so the city was spared the worst. The city did get a spectacular lightning show however. Cottage-country north of Winnipeg and a few towns northwest of the city took the brunt of the storms. Very large hail fell from Westbourne to Teulon to Matlock to Beaconia to Silver Falls. The largest hail stone reported was 10 cm in diameter, located near Silver Falls. Significant and widespread damage occurred as a result. Locally 40-50 or more mm of rain also fell within an hour, causing overland flooding. The following table gives a chronology of storm reports from the event.

Table: Chronology of storm reports from the overnight thunderstorms of August 22
Approx time
2:00 am
Nickel to golf ball size hail.
4:15 am
Quarter size hail with significant accumulation. Tree, garden and vehicle damage occurred. 43 mm of rain in 1 hour caused overland flooding. Mounds of hail still remained on the ground hours after the storm.
4:45 am
5 cm diameter hail.
5:15 am
Grand Marais
Golf ball size hail.
5:30 am
Baseball size hail punched holes in roofs and totalled almost every vehicle left outside during the storm. 50+ mm of rain also fell within an hour.
5:45 am – 6:00 am
Pine Falls, Powerview and Silver Falls area
Nickel to softball size hail. One photo showed a 10 cm diameter hailstone.

Heavy thunderstorms developed again midday in the Red River Valley. Winnipeg was particularly hard hit by these. 50 mm fell in less than 1 hour in parts of the south end. Nickel to toonie size hail, wind gusts to 80 km/h and frequent lightning also occurred, making for quite a storm to remember. Numerous streets and underpasses flooded and some were impassable. Water seeped into and flooded parts of St Vital Mall. Lightning caused a few fires and wind snapped branches.

The afternoon thunderstorms also dumped some large hail in other areas. Nickel to quarter size hail fell in Oakbank, Winkler and Jessica Lake. Training thunderstorms continued to pummel southeastern Manitoba late afternoon and evening, dumping significant rainfall. Rain from these also spread into the Winnipeg area and Red River Valley. Wrap-around rain around the low pressure system continued to drench south and southeastern Manitoba in the overnight and morning on August 23. Two-day rainfall totals were significant. Widespread totals of 50 to 110 mm occurred throughout the Red River Valley, southeastern Manitoba and the Interlake. In Winnipeg, close to 75 mm fell in southern sections of the city. At Winnipeg airport, about 46 mm fell. 38.4 mm of this fell on August 22 alone, breaking the old record of 38.1 mm in 1959 for the day.

Monday, 4 January 2016

#7, #6 & #5 - Top 10 Weather Stories of 2015 in the Winnipeg Area

#7 - Sizzling in September... Again

A three-day heat wave started September in southern Manitoba. Temperatures exceeded 30°C and in some cases the 32°C required for heat wave status. No record highs occurred in Winnipeg but a record high minimum of 21.0°C was achieved on September 3. This was also the second highest daily minimum temperature on record in September since 1872.

The main story during the heat wave was the humidity as dewpoints rose to record highs. Two high dewpoint records and three high minimum dewpoint records were broken. Dewpoint reached 23.1°C on September 3, the second highest dewpoint on record in September since 1953. This was just shy of the all-time September high dewpoint of 23.4°C on September 2, 1983. A record dewpoint of 22.9°C was also achieved on September 4, the third highest dewpoint in September. In addition to these records, an all-time September high minimum dewpoint was acheived on September 3, with a minimum dewpoint observation of 18.7°C. The previous all-time September high was 17.2°C in 1960 and 2005. The high heat and humidity pushed humidex values to 40.1 on September 2 and 42.0 on September 3. The humidex of 42.0 was the second highest in September since 1953. These were two of only six occurrences of humidex over 40 in September since 1953.

Occurrences of humidex over 40 in September since 1953:
1.  45.9  (Sep 2, 1983)
2.  42.0  (Sep 3, 2015)
3.  41.4  (Sep 5, 1978)
4.  41.2  (Sep 2, 1960)
5.  40.4  (Sep 6, 2013)
6.  40.1  (Sep 2, 2015)
Winnipeg September 4, by Felicia Wiltshire
The heat wave ended with a bang as strong thunderstorms hit on September 4 and 5. Severe nocturnal thunderstorms between 1 and 8 am on September 4 dropped dime to toonie size hail south and east of Winnipeg and northwest of Minnedosa. Minor crop damage was reported near Strathclair. Strong thunderstorms moved up the Red River Valley in the afternoon, dumping flooding rains and producing strong wind gusts. The Winnipeg area was one of the hardest hit areas with 30 to 50 mm of rain in just under an hour and wind gusts over 80 km/h. Significant street flooding occurred as a result. With more rain later in the day, daily totals sat between 40 and 60 mm. The airport recorded 41.1 mm for the day, breaking the old record of 36.8 mm in 1872. Heavy thunderstorms moved up the Red River Valley again the following day. 15-30 mm fell southeast of Winnipeg with locally close to 40 mm near Letellier.

Another hot day occurred on September 13. Temperatures exceeded 30°C across southern Manitoba. Winnipeg reached 31.6°C, just shy of the old record of 31.7°C in 1927. The hottest temperatures were along the US border with highs between 32 and 34°C. Numerous records were broken including in Morden and Pilot Mound where highs of 33.8°C and 33.3°C occurred. Generally warm conditions continued throughout the remainder of September with numerous days over 20°C and 25°C. In total, 5 days exceeded 29°C in Winnipeg, tied with three other years for second most in September since 1872.

Overall, it was the 6th warmest September on record since 1872 in Winnipeg with an average mean temperature of 15.8°C. It was the warmest September since 2009 and the second warmest since 1949. Dewpoint temperatures averaged 9.8°C, the 3rd most humid September since 1953. 3 days saw dewpoints over 20°C, tied with 1970 and 2005 for second most in September.

Top 10 warmest Septembers in Winnipeg since 1872 (by average mean temperature)
1.  17.7°C  (2009)
2.  16.8°C  (1948)
3.  16.6°C  (1940)
4.  16.3°C  (1897)
5.  16.1°C  (1906)
6.  15.8°C  (2015)
7.  15.6°C  (1931, 1967)
9.  15.4°C  (1920, 2013)

#6 - An Active Manitoba Thunderstorm Season Despite a Late Start

It was a late start to the thunderstorm season across southern Manitoba. The first severe thunderstorm event didn't occur until June 1. In Winnipeg, the first thunderstorm recorded at the airport was on June 7, the third latest start to the thunderstorm season since 1953.

Top 5 latest starts to the thunderstorm season at Winnipeg airport since 1953:
1. June 28 (1958)
2. June 10 (2013)
3. June 7 (2015)
4. June 3 (1992 and 1995)

However, the late start was not forewarning a tame thunderstorm season. Once things got going, they really got going. In the end, Manitoba had the greatest number of reported tornadoes and waterspouts in Canada for 2015. In addition, Manitoba had the most severe hail and severe thunderstorm rain events of the three Prairie provinces. This year was different from the last 4 years in that Winnipeg and the Red River Valley as a whole finally got in on the action.

At least 11 tornadoes and waterspouts occurred in Manitoba in 2015, the most in more than 5 years and the most in Canada for the year. Two events this year brought worldwide attention: at least 2 tornadoes and waterspouts on July 18 near Matlock and at least 3 tornadoes on July 27 in southwestern Manitoba (according to Justin Hobson's chase story).

On July 18, a landspout tornado near Matlock travelled over Lake Winnipeg, becoming a waterspout. The storm then produced at least one other waterspout. The two waterspouts occurred simultaneously, as seen in the photo below by Wray Pearce. The storm and waterspouts were very photogenic and photos spread around the world on social media.
Twin Water Spouts over Lake Winnipeg at Matlock
Two waterspouts over south basin of Lake Wpg July 18; by Wray Pearce
On July 27, a supercell thunderstorm travelled over 100 km from Tilston to northeast of Virden, producing multiple tornadoes in a 3-hour timeframe. Some were quite violent as seen on storm chasers' videos. One tornado reached close to a kilometre wide. Luckily, the strong tornadoes dodged all major communities and narrowly missed Virden. Only a few farms experienced some damage. Environment Canada sent a damage survey team to investigate. The worst damage they saw was from a high-end EF-2 tornado (winds close to 200 km/h). It is entirely possible that the tornadoes may have been even stronger, but when/if they were they weren't hitting anything significant. Photos and video of the tornadoes can be seen by following this link.

Hail was also a big story this summer across southern Manitoba. Almost half of severe hail reports were in August thanks to extreme nocturnal thunderstorm activity mid and late month. Significant hail events occurred on August 12, 22 and 28 and are described later. The following table summarizes the number of reports by category received to Environment Canada in the 3 Prairie provinces from May to September. Notice that Manitoba had the most severe hail and severe thunderstorm rain reports. Also note that number of reports is not equivalent to number of events.

Table: Number of thunderstorm-related reports by category and by Prairie province from May to September 2015

On August 12, severe nocturnal thunderstorms impacted the Onanole area near Riding Mountain Nat'l Park around 7 am. Hail up to golf ball-size damaged vehicles and damaging winds knocked over dozens of trees. The wind also tore part of a home's roof and blew it 300 metres away. Residents in the area thought they had witnessed a tornado, but given the situation it is more likely that it was a microburst. Storms then moved into the Neepawa and Gladstone areas between 8 and 11 am, dropping quarter to golf ball-size hail which damaged crops and vehicles. Widespread thunderstorms continued their trek southeastward throughout the afternoon, dropping loonie-size hail near Plum Coulee and loonie to golf-ball size hail around Vita and Caliento.

Altona Aug 28, by Colleen Otto Harder
The August 22 event will be described in detail later on in the top 10 events series. On August 28, damaging nocturnal hailers occurred southwest of Winnipeg. Toonie-size hail and larger fell from Austin to St. Claude to Roseisle to Plum Coulee to Altona. The Plum Coulee to Altona region was hardest hit with hail up to baseball-size. Major damage occurred in Altona with broken windshields and siding, flattened and shredded plants/trees, damaged crops and dented vehicles. The storm also dumped about 26 mm of rain, causing some street flooding.

Significant hail, wind and flooding rain events also occurred on June 27, July 4 and July 15. Details on these events can be retrieved in the summer summary that was posted here.

#5 - A Very Early Spring

March 13 in Winnipeg. Source: CBC
Similar to 2010 and 2012, spring began much earlier than usual in 2015. April-like temperatures and snow pack melt arrived by the second week of March. The winter snow pack dissapeared in Winnipeg by March 15, tying with 1995 for third earliest snow melt since 1955. This was just a day later than in 2012 and a day earlier than in 2010. It was also a drastic change from 2013 and 2014 when the snow did not melt until April 28 and April 21 respectively. The 1981-2010 normal is April 3.

Record warmth arrived on March 14 and 15 with temperatures reaching the teens. Winnipeg reached 13.2°C on March 14, breaking the old record of 11.4°C in 1981. A high of 14.3°C was achieved the following day, just 0.1°C off the old record of 14.4°C in 2012. The warmest temperatures occurred along the US border with highs reaching the high teens in some cases. Morden reached highs of 18.3°C and 17.6°C, the earliest occurrences of temperature over 16°C on record since 1904. The high of 18.3°C on March 14 broke the old 2012 record by an impressive 7.1°C! Nights were unusually mild as well. A morning low of 6.7⁰C in Winnipeg on March 15 was the warmest morning low for so early in the year since 1953. Previously, the earliest we had a morning low as warm or warmer than that was on March 19, 2012 with a morning low of 16.0°C.

Temperatures after the 15th were no longer record breaking but remained above normal. In the end, March averaged -3.0°C, 2.8°C warmer than the 1981-2010 normal and the 20th warmest March since 1872. Even thunderstorms occurred on March 30 west and north of Winnipeg. Some small hail fell. No thunder could be heard in Winnipeg but some small hail was reported in the south end when some convective showers rolled through.

Warm conditions did continue in April before tapering off in May. The spring as a whole (March to May) tied 22nd warmest with an average mean temperature of 4.5°C.