Thursday, 1 January 2015

#4, #3 & #2 - Top 10 Weather Stories of 2014 in The Winnipeg Area

#4 - Super-Soaking June Storms 


Biblical amounts of rain fell over the Prairies again this year – this time in mid and late June. While Winnipeg and the Red River Valley did see well above normal rainfall, amounts were much higher out west.

147.1 mm of rain fell at Winnipeg airport in June, 65% above normal and the 12th rainiest June since 1872. Most of the rain fell in the last 18 days of the month with a whopping 133.8 mm. Heavier amounts fell in southern and eastern portions of the city where over 160 mm fell in June, more than 140 mm of which fell in the last 18 days of the month.

Most of the rain fell during two multi-day rain events. The first was from June 13 to 16. This particular rain event affected mostly the Parklands, Interlake, southeast and Red River Valley portions of southern Manitoba where anywhere from 20 to 120 mm of rain fell (see rainfall map here). In Winnipeg, generally 65-80 mm fell. 69.9 mm fell at Winnipeg airport, the greatest rainfall event since late May 2010. Heavier amounts fell to the north and east with 93.5 mm in Beauséjour and 120.6 mm in Lockport. Localized training thunderstorms on June 14 caused these higher amounts. Most of the rain fell on June 15 with a Colorado Low. 40.1 mm fell at the airport June 15 alone, obliterating the old record of 18.3 mm in 1928.

Another significant rainfall occurred June 19 with 20-30 mm in Winnipeg. The Brandon area was hit hard as a training band of heavy downpours moved through for several hours. A whopping 75.2 mm was recorded at Brandon airport.

Another multi-day rain event occurred June 27 to July 1 (see rainfall map here). Winnipeg received 35 to 65 mm during the period. Southwestern Manitoba and southeastern Saskatchewan were hit hard as multiple waves of heavy rain and thunderstorms drenched the region with 90 to 200 mm. Amounts included about 138 mm in Brandon and about 164 mm in Deloraine. June 27 was particularly wet in the Brandon area with 50+ mm locally. According to some of my family members, the town of Rapid City experienced significant flooding as a creek burst its banks onto properties and streets after thunderstorms dumped over 75 mm of rain.

The TCH east of Brandon; Credit: Randall Paull
Too much rain in too little time on top of already wet soils spelled disaster. Significant overland and stream flooding occurred on both sides of the Saskatchewan-Manitoba border.  Creeks and rivers burst their banks as they neared or exceeded record levels, including the Assiniboine River. Vast expanses of farm field flooded and several highways were closed and washed out. Water even topped portions of the Trans-Canada Highway, as seen to the right in the photo by Randall Paull on twitter. Water also topped the access road to the Brandon airport, causing flight cancellations. Many communities issued states of emergency, including the City of Brandon. The situation was reminiscent of spring 2011 – the only difference this time was that the flooding was caused by heavy summer rains. Flooding of this calibre occurring in the middle of summer is almost unheard of in these areas.

The systems that affected southern Manitoba late month, particularly a system which moved in on June 29, were more typical of spring or fall systems. Station-level pressure dropped to 95.78 kPa at Winnipeg airport at 6 pm on June 29, the 4th lowest pressure reading in June on record since 1953. Very strong winds behind the system brought damaging winds to southwestern Manitoba. Brandon recorded sustained winds of 50 to 70 km/h and gusts of 80 to 100 km/h. A maximum sustained wind of 72 km/h and maximum gust of 104 km/h were recorded.

In the end, 251.6 mm of rain fell in Brandon in June. This was not only the rainiest June but also by far the rainiest month on record since 1890. It obliterated the old record of 217.3 mm in August 1980. Even more impressive, 219.8 mm of this rain fell in just the last 12 days of the month, more than half the annual normal. A large swath of the Prairies from Brandon, Manitoba to Lethbridge, Alberta saw record June rains. As a result, it’s no mystery that flooding was so severe. Thankfully for southeastern Manitoba, the rains were less intense. Thus, flooding was not as concerning as it was out west.

To finish off, the Brandon Sun had some great photos of the flooding in southwestern Manitoba. You can view them by following this link.

#3 - January 15 ''Super-Clipper'' 

An unusually potent clipper system raced across the Prairies January 15-16. It produced rapidly rising temperatures to record highs, record winds, significant blowing snow and even thundersnow.

The system began by producing record winds and high temperatures in the morning and afternoon in Alberta and Saskatchewan. Edmonton municipal airport (near downtown) recorded a wind gust of 120 km/h, the strongest wind on record in Edmonton. Old record was 117 km/h on June 6, 1960. Similar story in Saskatoon where a gust of 115 km/h was recorded, breaking the old January record of 111 km/h in 1986. A summary of the damages caused in Edmonton can be seen here, and in Saskatoon here. Numerous record high temperatures were also reached with highs reaching mid to high single digits.

In Winnipeg, temperatures reached a record 3.3°C early evening (old record 2.2°C in 1973) after a low of -27.4°C in the morning. This 30.7°C warmup was the greatest single-day warmup on record since 1872.

Table: Top 5 greatest single-day ('calendar-day') warmups since 1872

Magnitude of warmup
Jan 20, 1874
May 12, 1949
May 19, 1899
Jan 30, 1934

Note that the previous table does not consider how rapidly the warmup occurred. In this case, temperatures rose 30.7°C in just 14 hours. However, even greater rates of warming have occurred in the past. For example, on April 28, 1985, temperatures rose 26°C in just 8 hours (from 4°C to 30°C).