Weather Forecasts, Facts and News for Winnipeg & Southern Manitoba
Author: Matthieu
Matt has been a member of the AWM team since January 2012, writing the weekly feature Elsewhere in Weather News which highlights weather news from across the globe. Matt has lived in Winnipeg all his life and has been a weather enthusiast since a very young age. He is currently completing his B.Sc. in Atmospheric Sciences at the University of Manitoba.
Southern Ontario, Midsection of US Anticipate Ice Storm
A major ice storm has been taking shape as of Friday night across parts of Oklahoma and Texas and will continue to push northeast. A potent cold front with Arctic air filtering in behind it is clashing with gulf moisture moving north and thereby creating prime conditions for ice accumulation from Oklahoma all the way to southern Ontario. Dangerous travel conditions are expected as there could be significant ice accumulation due prolonged periods of freezing rain through this weekend. With this comes the possibility of downed power lines so residents have been made aware to prepare for power outages across southern Ontario. So overall, not ideal conditions for holiday travel this weekend as all kinds of precipitation will be falling across the eastern half of the US and southern Ontario.
Freezing rain sounding from Oklahoma on Friday evening. Note the shallow freezing layer near the surface where the arrow is. (Souce: Twisterdata)
Freezing rain forms when there is a deep layer of warm air that is above freezing aloft. As the ice crystals fall and meet the warm layer, they melt and become raindrops while falling towards the ground. A shallow layer of cold air just above the surface of the earth must also be present for freezing rain to form. Supercooled water droplets – drops of liquid water that exist in below freezing air, will be in place and won’t have enough time to freeze into ice pellets, thus will freeze (as ice) on contact as they hit the ground.
In addition to this, a severe weather outbreak is expected in Dixie Alley of the US today. The outbreak is associated with the same system as the cold front slices through the warm, moist air mass in place. A moderate risk has been issued by the Storm Prediction Center as well as a 15% hatched area for tornadoes in Mississippi and northern Louisiana. Chances of tornadoes are quite high, the only possible limiting factor is that CAPE will be fairly low (only around 500-1000J/kg) but this will still be sufficient for supercells which will quickly evolve into a quasi-linear convective system – a line of severe thunderstorms that can have bowing segments. SPC gives fairly strong wording for today in Dixie Alley saying that “there is potential for several tornadoes – some of which should be strong”.
By Monday night the system will have moved off the US East Coast but will still be a weather-maker for Atlantic Canada.
Editor’s Note: The following is a guest post by @jjcwpg, originally posted here and has been updated with some relevant links from A Weather Moment.
July 13, 2013 southwestern Manitoba; most significant storm event of season; @lovestormsmb and I were there.
For the 4th consecutive year, I have gathered statistics on thunderstorm and severe thunderstorm frequency across southern Manitoba. An explanation of how I gathered these statistics as well as notes on accuracy can be viewed here. I have divided southern Manitoba into 6 regions: west, southwest, south, southeast, east and Interlake. These regions can be seen here. I understand the zones are not equal in size; I plan to try to improve this next year. Lastly, I’d like to thank you in advance for taking the time to read this post as it is one of my favourite posts of the year!
Number of days in 2013 thunderstorms were observed in each region.
The 2013 thunderstorm season was less active than in 2012 in all regions of southern Manitoba. The greatest decline in thunderstorm days was in the Interlake, southeast and east parts of Manitoba where in some cases there were more than 10 thunderstorm days less than in 2012. The Interlake saw the greatest decline, dropping from 67 thunderstorm days in 2012 to only 55 this year. In total, there were 89 thunderstorm days across southern Manitoba this year, compared with 109 last year.
One reason for the decline is because 2012 had a very long thunderstorm season, lasting from March to November. This year, the first thunderstorm did not occur until April 30, and the last on October 11 putting the season at 165 days long, compared with 237 days last year.
The season began quite late in some areas this year, in large part thanks to an incredibly late spring. The South, Interlake and East zones did not see their first thunderstorm until May 14, 2 months later than last year. On a more local scale, Winnipeg saw its first t-storm on June 10, the second latest start to the thunderstorm season since 1953.
Number of days in 2013 a severe thunderstorm warning was issued for each region.
Again in Winnipeg, there were only 17 thunderstorm days this year at the airport, tying for 4th least in a year since 1953. It just so happens that one of the years we tied with was 2011. This really follows the trend of the past few years of below normal thunderstorm activity in the city. The last time we had an above normal season was 2007. The last 6 years have averaged some 6 days below the 1981–2010 and 1971–2000 normal of 26 to 27 days.
In comparison, Brandon had 23 thunderstorm days this year, and I recorded 20 here in south St Vital.
The map to the left shows the number of days with a severe thunderstorm warning issued by Environment Canada in each warning zone. It appears southwestern Manitoba was the busiest this year for severe thunderstorms. The season in Manitoba lasted from June 9 to September 26, or 110 days, compared with 116 days last year. Click here for a map of the length of the severe thunderstorm season in each warning zone this year.
Number of days a tornado warning was issued in each region through 2013. Also plotted are confirmed and unconfirmed tornado events.
The last map I have is of tornadoes, as seen to the right. The colours in the warning boxes represent the number of tornado warning days this year, and the dots represent unconfirmed (possible or probable) and confirmed tornadoes (coloured by intensity). Only 4 tornadoes were confirmed, but many more may have touched down.
The most notable twister was in Sioux Valley, First Nation, west of Brandon on July 18. It was a strong EF–0 tornado, and moved right through town, destroying a few homes and leaving a few injured. Other than that, the most significant potential tornado event was in the Pipestone to Hartney area on July 13. Significant damage occurred in the area, including to the arena in Pipestone which half of it had been flattened. It is still up in the air wether a tornado occurred or not. Either way, according to Discover Westman, some recall the storm as being the worst storm in recent memory in southwestern Manitoba.
The storm also only worsened the flooding conditions in Reston, which saw yet another round of biblical rains with the storms. In fact, the town had received about 352 mm of rainfall in just a 24 day period from June 20 to July 13 according to Manitoba Agriculture.
Lastly, the following graph summarizes the number of thunderstorm days, severe t-storm warning days and tornado warning days across all of southern Manitoba per month:
Summary of all thunderstorm statistics for all of Southern Manitoba broken out by month.
Thanks for reading! A summary of the severe storm season across Canada will come late next week.
This past week a weak cyclone hit India’s east coast as a weak cyclone depression. The cyclone – Cyclone Lehar was classified as a severe cyclone in the Bay of Bengal with winds over 100km/h but has since been downgraded. Unfavorable sea surface temperatures and shear for storm development did a good job on tearing up the storm apart before landfall. The storm made landfall as a tropical depression on Thursday, with winds of 60-70km/h at landfall. Evacuation precautions were taken by the India Meteorological Department because of the strength of the cyclone while it was over the Bay of Bengal but the only real threat that Lehar brought was flood threat. No significant damage was reported from the storm but some crops have been damaged and a few districts vulnerable to flooding in India’s Andhra Pradesh state have been affected by flooding.
Cyclone Lehar as it was struggling to organize over the Bay of Bengal. (Source: NDTV)
Arctic air dominated over a good part of both Europe and the United States this week which brought minimal significant weather to the regions. Apart from significant snowfall associated with a trough of low pressure affecting the eastern seaboard of the United States earlier this week, active weather has been kept to a minimum. The next big weather event is likely to be a winter storm which will affect the northern states (MT, ND) and even southern Manitoba on Tuesday and Wednesday of next week.
Severe flooding has been taking place in Sardinia, Italy this past week causing residents to rush for higher ground. Sardinia is one of Italy’s islands located in the Mediterranean Sea; about 1.7 million Italians reside here. An upper level low drew in moist air from the Mediterranean Sea and spun just off the coast of Sardinia, causing for some significant flooding on the island. Rainfall totals generally ranged between 35 and 50mm on the island, which is over half of their monthly total for November.
Severe flooding in the city of Uras, on the island of Sardinia. (Source: AP)
As this fell in a span of about 24 hours, sewers were unable to handle these large volumes of water in that short period of time. In some areas water levels reached about three meters, causing roads and bridges to be washed away. As of Friday night 18 fatalities had been reported. Several waterspouts and brief tornadoes had also been spawned by this system off of Italy’s coast and on the mainland.
Tornadoes Rip through US Midwest
In last week’s post of EIWN the risk for severe storms affecting the Midwest US had been briefly talked about. The event that occurred on Sunday was a fairly significant event; the moderate risk talked about in last week’s post had been upgraded to a high risk on Sunday – a risk only issued once or twice by the SPC when major severe weather events are imminent. This severe weather event followed up with all the hype ahead of it. In total, 106 tornado reports were received and 74 tornadoes were confirmed. Two of these were classified as EF-4 strength and 33 classified of EF-2 strength and higher, making November 17th a significant tornado outbreak in the Midwest. There were also numerous (400+) wind damage reports scattered from Iowa to New Jersey, as expected with the high shear environment on that day. One of the strongest tornadoes of the day – an EF-4 ripped through the town of Washington, Ill., where some houses were completely ripped apart by the twister. Death toll from the outbreak is at eight but could have been significantly higher if not for the good forecasting and swift warning issuance by NWS.
Map of all the warnings and watches issued on the 17th. Tornado watches/warnings in red and severe thunderstorm watches/warnings in blue. Polygons are the warnings. Click on image to enlarge. (Source: SPC)
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