Wednesday, 31 December 2014

#7, #6 & #5 - Top 10 Weather Stories of 2014 in The Winnipeg Area

#7 - Mild And Lack of Snow in December

     Manitobans were relieved that December 2014 did not follow 2013's path. After a 6th coldest December last year, December 2014 was much more tame as a lengthy warm spell brought spring-like conditions mid month. The warm period lasted approximately 21 days from December 6 to 26, and was only interrupted by a couple short and insignificant cool downs. The average high during this period was -2.8°C, well above the normal of about -9°C for the period. Lows were even more extreme, averaging -9.3°C, significantly above the normal of -18°C for the period. 5 days exceeded the freezing mark, only slightly above the normal of 4 days.

     The downside to the warmup was the cloudiness. Several consecutive days of cloudy skies, fog and freezing drizzle occurred. Although this kept daytime highs a little lower, overnight lows were very mild thanks partly to the cloudiness. 13 days did not even drop below -7°C. In addition, 3 high minimum records were broken. The record on December 12 was particularly notable. The minimum of -0.5°C shattered the old record of -3.9°C back in 1877, Winnipeg's warmest December on record. 5 high dewpoint records were also broken: 1 high maximum and 4 high minimums. The high minimum dewpoint records shattered the old records by 4 to 5°C.

     Freezing drizzle and rain fell on 7 days, covering everything in a sheet of ice. About 0.7 mm of drizzle fell on December 14 alone, breaking the old rainfall record of 0.3 mm in 1928. About 1 mm fell during the month, tying for 24th rainiest December since 1872.

     The height of the warmup occurred December 11 to 14. Although highs remained not far from 0°C around Winnipeg (partly due to low cloud), temperatures were in the mid to high teens just 1 km above the surface. Sunshine did show up in southwestern Manitoba, allowing for much warmer temperatures at the surface. Highs reached high single digits in some traditionally milder locations. Even a few double digit highs occurred around Boissevain and Deloraine. Deloraine in particular reached 10.3°C on December 11.
Bare fields near Emerson on Christmas Eve; Source

     There was also a notable lack of snow in December. Snow depth remained under 10 cm the entire month. Significant melting mid month dropped our snow pack to just 3 or 4 cm by a week before Christmas. Outside the city, open farm fields were quite bare up until Christmas Eve when a couple cm fell. Around Emerson, it was a brown Christmas with only a dusting of snow on the ground.

     In the end, December averaged -10.0°C, tied 23rd warmest December on record since 1872. Only 7.2 cm of snow fell, the 16th least snowy December. In addition, only 4.8 mm of precipitation fell during the month, the 8th driest December on record since 1872 (note that this value was obtained using a combination of data from The Forks and Airport stations (The Forks had to be used on some days because the airport did not record precipitation on some days that did see precipitation fall)). Unfortunately, any money the city saved on snow clearing in December was spent salting and sanding icy roads.

#6 - Summer's Revisit in Late September 


     Late September is usually when we worry about our first frosts of the season, but this year mid-summer heat made a welcomed return to southern Manitoba. 
The fall colours were spectacular in September

     From September 22 to 27, temperatures soared well into the 20’s and 30’s across southern Manitoba, 5-20°C above normal. In Winnipeg, all but one of these 6 days exceeded 25°C. September 26 was the hottest with a high of 30.2°C, just shy of the old record of 31.7°C in 1952. However, it was even hotter in southwestern Manitoba where the heat was unprecedented for so late in the season (at least since records began). In Brandon, highs of 34.0°C and 32.8°C on the 25th and 26th respectively were not only record highs but also the hottest temperatures for so late in the season since 1890. Previously, Brandon had not seen those types of temperatures any later than September 22. The Manitoba hotspots during the warm spell were Swan River and Wawanesa where temperatures reached a scorching 35.1°C.

     Only one temperature record was broken in Winnipeg – a record high minimum of 17.4°C on September 26. This was also the warmest minimum for so late in the year since 1872. Humidity was the main story in the RRV with dewpoints well into the teens and humidex values into the 30’s. 6 daily high dewpoint records were broken in Winnipeg - some exceeding the old record by 2-3°C. A maximum dewpoint of 18.1°C on September 26 was one of the highest dewpoint values for so late in the season on record. A maximum humidex value of 35.8 that day was the latest occurrence of humidex over 35 on record since 1953. Previous record was on September 19, 2004 when a humidex value of 38.1 occurred. This follows the latest occurrence of humidex over 40 on September 6 last year.

     Thanks to the late month warm spell, September finished 0.6°C above normal. As a result, September 2014 was the 16th above normal September in the last 21 years.

Stormy skies Aug 24 near Warren, Manitoba

#5 - Drenching August Rains 


     A second active period this summer occurred from mid August to early September. Multiple rounds of thunderstorms and heavy rains dumped impressive rainfall totals once again across southern Manitoba. Although amounts were not as high as they were in June, they were enough to cause additional flooding.  

     In total, 104.4 mm of rain fell at Winnipeg airport in August, 32% above normal and the 23rd rainiest August since 1873. 85.4 mm fell in just the last 15 days of the month. However, amounts were highest in central and southwestern parts of the city where 130 to 200 mm of rain fell in August. Thanks to an active and humid weather pattern mid-late month, dewpoints averaged 14.4°C in August, 4th highest on record since 1953. 24 days saw dewpoints over 15°C, above the normal of 18 days. Two daily high minimum dewpoint records were broken during the month.

     August 21 was the big event for Winnipeg. Stationary pulse thunderstorms developed right over the city in the late afternoon and early evening (see radar loop). Torrential downpours lasted for over an hour in central, western and southwestern portions of the city before the storms finally rained themselves out. In total, 40 to 100 mm of rain fell from downtown to Whyte Ridge, an entire month’s worth (see City of Winnipeg rainfall map). The event was classified as over a 1-in-100 year event over downtown according to the City of Winnipeg. Significant overland, underpass and street flooding resulted. According to CBC, water infiltrated some buildings and basements and some traffic lights were knocked out. Other parts of the city saw significantly less rainfall with amounts ranging anywhere from a trace to 30 mm. Some photos of the flooding can be seen here.

     A widespread rain event associated with a Colorado Low dumped high rainfall totals across all of southern Manitoba August 23-24. Highest amounts fell in the Interlake and southwestern Manitoba where 50 to 80 mm was recorded. Winnipeg received 20-30 mm. Highest amounts in the RRV occurred around Steinbach and Morden with 35-45 mm.

Blinding rain, not a blizzard - Steinbach (Credit: Bonnie Stanwick)
     August 29 featured another deluge, but this time south of Winnipeg. Large, slow-moving heavy thunderstorms moved from Carman to Niverville to Steinbach late morning and early afternoon, creating blinding downpours (the picture to the right, by Bonnie Stanwick, gives an idea of how heavy the rain was). Generally, 30 to 70 mm of rain fell in less than an hour. However, localized unofficial amounts of 75 to 125 mm were reported. In Steinbach, 66.8 mm of rain was recorded at the MAFRI station. According to Environment Canada, 50-60 mm fell in the Steinbach area in less than half an hour. Significant overland flooding occurred with many streets, fields and yards under deep floodwater. You can follow this link for a video of flooded streets in Steinbach.
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A list of sources can be found here

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