Top ten weather stories for 2012: story four
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4. March’s Meteorological Mildness
A leading American climatologist called the March 2012 heat wave the most extraordinary temperature anomaly in North American history. It was off the scale in every way: intense, huge and long-lasting. The heat eclipsed every previous temperature record and upstaged the winter that wasn’t. Around mid-March, temperatures soared throughout central and eastern Canada, with many cities registering the kind of weather reserved for early summer. Record and near-record breaking temperatures (dating back to the start of record-keeping in 1948) dominated two-thirds of North America and contributed to the warmest March on record across the Prairies and in the Great Lakes and St. Lawrence basin.
The warmth resulted from a large low-pressure centre to the northwest of the Great Lakes and a strong stationary high-pressure system in the East. Rotating in opposite directions, the systems acted like two gigantic connecting gears, generating a large surface pressure gradient that maintained moderate winds from the southwest for more than two weeks. Warm air funnelled north between them all the way from the Gulf of Mexico well into Canada, leaving temperatures as warm in Kapuskasing as they were in Corpus Christi. Added to the mix was a historic negligible snowcover; instead of losing energy to melt snow and ice and thaw the ground as it travelled north, the air was able to keep its heat. Also of note, a persistent west-to-east jet stream further north than usual kept cold Arctic winds confined to the upper regions of Canada, enabling warm air to surge northward unhindered.
The following is a sample of the unbelievable Canadian temperature records set during March’s heat wave:
- Fort Frances, Ontario, normally frozen solid in mid-March, reached 26°C. On March 19, the town recorded a minimum temperature of 15.1°C; the previous record high for the day was 10°C.
- Winnipeg soared to 20.9°C on March 19 – the earliest-ever temperature above 20°C in a calendar year. Just as crazy, an intense thunderstorm with heavy rain occurred at 7 pm. The next day the temperature topped 23.7°C.
- Windsor had 10 straight days above 20°C – a record for longest duration.
- At Halifax, the mercury reached 27.2°C on March 22, breaking the previous record of 11.8°C set in 1983.
- In Petawawa, the afternoon temperature on March 21 reached 28.8°C, which was almost 17 degrees warmer than the previous record of 12.2°C and the highest temperature ever recorded in Ontario in March.
- When temperatures in Abitibi-Témiscaming exceeded 27°C, it was an incredible 25 degrees warmer than normal.
- Lake Major, Nova Scotia was the nation’s hot spot at a remarkable 30°C on March 22.
- Halifax, Charlottetown, Fredericton, Hamilton, Winnipeg, Toronto, Ottawa, Montreal and Quebec City were just a few of the hundreds of stations that broke their all-time March records. For more than half the country, the number of temperature records broken was in the thousands – a record for the number of records broken.
Even with a soft winter, millions of Canadians seemed grateful for an early spring with unusual warmth and abundant sunshine. Runners and cyclists jammed sidewalks and road shoulders; there were huge energy savings for greenhouse growers, homeowners and commercial customers; cities saved millions on snow removal; and several golf courses opened their earliest ever. Even farmers got in on the action, pushing their planting weeks ahead of schedule.
But not everyone was basking in the sunshine. A record-warm March cut the maple sugar season short in Ontario and western Quebec with fewer-than-average yields. The run started early with less than ideal flow weather and ended abruptly when trees started budding, making sap unusable. In Ontario, skating rinks and toboggan and ski runs closed before the profitable March break. In most regions of Canada, pollinating trees and grasses started producing in unison, contributing to an early explosion of pollen. Even people without allergies were experiencing throat tickles and inflammation. In Quebec, flooding was an issue in several areas as the heat melted any snow very quickly. The largest flood evacuation in the province happened between March 22 and 24 when over 700 residents left their homes in St-Raymond de Portneuf. And in Perth-Andover, New Brunswick the abnormal March heat triggered one of the largest ice jams and floods in history. In the Atlantic Ocean, an early loss of ice cover hampered the seal hunt and presented a significant barrier to seal mothers that rely on ice to give birth and nurse their pups.
Fruit trees in the East were particularly impacted by the early warm weather – blooming nearly five weeks ahead of schedule – so when a killing frost hit Ontario, Quebec and New Brunswick orchards in late April the damage was extensive. Apple growers took the biggest hit when temperatures plunged below -5°C for a dozen hours or more in late April. The combination of cold air, light winds and clear skies – deadly ingredients for hoar frost – produced a white sheath on rooftops, windshields and fragile blooms. The catastrophic flash freeze wiped out about 80 per cent of Ontario’s apple blossoms and resulted in less than half the yields for tender fruits, with total losses estimated at more than $100 million. Strawberry growers also faced multiple frosts with yields generally 50 per cent less than normal.
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