Saturday, November 21, 2015

The week ahead..

A general look at the weather this week..

Sunday Nov 22nd: Hi: +1C. 
Some snow then turning milder. 
System tracking through central MB will spread an area of snow across the Interlake and eastern Manitoba. Bulk of snow will be mainly north and east of Winnipeg where 2-5 cm is possible, but Winnipeg will likely see a period of snow between 9 am and 3 pm, with a dusting to 2 cm possible. Once the snow ends, winds will shift into the west and draw in milder air sending temperatures up to the 0 or +1C mark by late afternoon.

Monday Nov 23rd: Hi: +2C 
Fair and mild. 

Tuesday Nov 24: Hi: +1C 
Fair and mild.

Wednesday Nov 25th: Hi: -2C in the morning falling to -8C by evening.
Turning windy and colder with snow.
A potent storm system emerging from the west coast will track across Montana and into the Dakotas bringing a widespread area of snow across southern Manitoba. Current indications are for 2-5 cm of snow for Winnipeg during the day. Increasing north winds and colder temperatures will likely produce areas of blowing and drifting snow especially in the afternoon and evening. 

Thursday Nov 26th: Clearing and colder: Hi -10C. 
Generally fair but cold. Temperatures dipping to -20C Thursday night.

Friday Nov 27th: Hi: -7C 
Nicer afternoon after a cold start to the day with temperatures at or below -20C.

Saturday Nov 28th:  Hi: -4C 
Milder with a chance of flurries. 

Sunday Nov 29th: Hi -5C 
Grey Cup day: Fair and seasonably cold.
At this early point, it looks like conditions should be fair and seasonably cold for the Grey Cup with average temperatures for late November and no precipitation expected. Models are not showing any major storm systems over the Grey Cup weekend, with a warming trend expected for the first week of December.  Things could change, but at this point, weather conditions look favourable for the Grey Cup game.

Tuesday, November 17, 2015

Major storm system to bring first wintery blast of season across southern and central MB Wednesday night into Thursday...

A pair of strong storm systems over North America will converge into a major storm system over the Manitoba/Ontario border late Wednesday, bringing the first onslaught of wintery weather to much of southern Manitoba Wednesday night into Thursday.  This will be the first real taste of winter for many in southern Manitoba after what has been an exceptionally mild fall to this point with little in the way of snow or cold weather.  Wednesday will start off cloudy and mild with periods of rain developing in the afternoon ahead of the converging storm systems. Things start to get interesting later Wednesday afternoon into Wednesday evening as the two storm systems begin to converge over NW Ontario producing an increasing NW flow of colder air across southern Manitoba. Rain will change to snow Wednesday evening as temperatures drop below the freezing mark, and continue through Wednesday night into Thursday morning. Strong northwest winds of 50-60 km/h with gusts of 70-90 km/h will produce locally poor visibilities in snow and blowing snow with local power outages possible due to the combination of ice buildup and strong winds. Snowfall amounts for Winnipeg and the RRV are expected to the in the 5 cm range with the bulk of snow falling across central and northern Manitoba, including the interlake and Whiteshell regions where locally heavier bands of lake effect snow are possible. As a result, expect a slower commute Thursday morning as drivers deal with the first snowfall of the season along with subfreezing temperatures and strong winds.

Sunday, November 15, 2015

Very mild start to November as extended autumn continues.. but change to colder weather on the way this week

It was another glorious fall-like weekend across southern MB with sunny skies and temperatures in the double digits. Sunday's high of 13.1C in Winnipeg was almost 15C above normal for Nov 15th, and was our 21st straight day above normal (since Oct 26th). The weather was par for the course in what has been an exceptionally mild start to November across much of central and eastern North America, especially over the upper US midwest and central Canada, including southern MB. In Winnipeg, the average temperature over the first half of November has been +3.3C, which is almost 6C above normal for the Nov 1-15 period.  Every day this month has been above normal so far and the coldest temperature this month has been only -6.4C, even though normal lows are now close to -10C. The downside of the mild weather has been frequent cloud cover, with only 4 days of sunshine through the first 12 days of the month. Snow however has been virtually absent in Winnipeg, with only a couple days with some light flurry activity. As of mid November, the grass is still green in the city thanks to a lack of deep freezes so far.

Figure 1 (left): Mean temperature and anomaly from normal (C) showing core of exceptional warmth this November over upper midwest  
Figure 2: (right) Winnipeg mean daily temperature past 30 days (Oct 16 - Nov 15) showing persistence of above normal temperatures over past 4 weeks

As mild as it's been, it may be surprising to learn that Winnipeg has had even milder starts to November in previous years. At 3.3C, the first half of November this year will rank only as the 8th mildest start to November since 1872. The warmest start to November (as defined by the mean daily temperature from Nov 1-15) was in 1981 and 1931, with an average temperature of +4.9C over the first half of the month.  Nov 1981 saw 10 days reach +10C or more in the first half with a peak of 18.2C on Nov 4th.  This year, Winnipeg has recorded only 4 days in November of +10C or more. This shows that our warmth this year has been mainly due to exceptionally mild nights, rather than mild days. Frequent cloud cover and lack of cold air intrusions has resulted in a persistence of mild nights with temperatures well above normal minimums for November. The top 10 warmest first halfs of November in Winnipeg since 1872 are:

So what does the rest of November look like? Well, mild weather is expected to continue the first half of this week, then a pattern change around mid week as a strong storm system brings a substantial cool down later this week with temperatures likely falling below normal for the first time this month. We may even see our first shot of accumulating snowfall here in the city Wednesday night into Thursday. Colder than normal temperatures will dominate through next weekend before a moderating trend next week.

Multi-model ensemble shows big temperature dip coming to
Winnipeg by Thu Nov 19th (850 mb temps top)
The transition to colder weather will likely be accompanied by
our first snowfall Wed night into Thursday  (precip amts bottom)

Friday, October 30, 2015

A mild October.. will mild pattern continue through November?

October 2015 was another mild month over the Prairies with temperatures averaging some 2-3C above normal over western and central Canada. In Winnipeg, the month finished with an average temperature of +7.1c, or 2.1C above the normal October average of +5.0C (30 year average). The mild weather comes on the heels of a warm September that finished 3C above normal, and was Winnipeg's 6th warmest September since 1872. The combined Sep-Oct average temperature of 11.5C made it Winnipeg's 9th warmest such period since 1872. (30 year average is +8.9C)

Map of temperature anomalies (left) showing widespread warmth in October over western North America. 30 day temperature graph for Winnipeg (right) showing dominance of above normal temperatures during October.  

Weather outlook for November 2015

According to NOAA, the mild weather pattern is expected to continue through much of November across the Prairies, with generally above normal temperatures over the next 2-4 weeks. (see maps below)  This doesn't mean warm weather every day, but generally a greater frequency of above normal temperatures during the next month.

CPC temperature outlooks maps for early and late November
 (8-14 day outlook left, and 3-4 week outlook right) 

The mild pattern appears to be in response to a very strong El Nino that has developed over the Pacific this year, and is currently on track to be one of the strongest El Nino episodes recorded since reliable records began in 1950. As of October, the 3 month averaged El Nino index was at +1.5 and expected to climb to +2 or higher by December, the strongest El Nino since 1997, regarded as the strongest El Nino event since 1950.  

Backgrounder: 2015 El Nino 

 Top: Graph of Oceanic Nino Index since 1950 showing strongest ENSO events
Lower: Graph of this year's El Nino ocean temperature anomalies expected to peak by December 

Note that Winnipeg had its second warmest winter on record in 1997-98, thanks to the unusually strong El Nino that year. That winter saw very little snow through December, with only a trace of snow on the ground in Winnipeg on Christmas day. The winter finished with an average temperature of -8.2C, a whopping 6C above normal, and the second warmest winter on record in Winnipeg, second only to that of the incredibly mild winter of 1877-78 (another very strong El Nino year)

NOAA winter outlook for Dec 2015-Feb 2016 showing greater odds
for drier and warmer than normal winter over Prairies

Will El Nino bring mild weather for Grey Cup? (Nov 29 2015 in Winnipeg)    

Grey Cup organizers and football fans are hoping that the mild weather pattern so far this autumn will continue through November, or at least through Nov 29th when the 103rd annual Grey Cup is scheduled at Winnipeg's Investors Group Field. Normal highs in Winnipeg by the end of November are around -6C, with lows of -14C. Temperatures on Nov 29th however have ranged from a high of +6C to a low of -33C (based on Winnipeg airport data since 1938). Last year, Winnipeg saw a high of -8.7C on Nov 29th with a low of -19.6C, and a game time temperature of -16C with strong northerly winds of 40 km/h giving windchills of -28 to -30. Officials are hoping for much milder conditions this year as footballs fans gather for the annual football finale. Given previous El Nino patterns, there are better odds this year that temperatures will be warmer than normal in Winnipeg for the end of November. Crunching some numbers from similar El Nino patterns in the past shows about a 55% chance of above normal temperatures for late November this year (highs > -4C), a 25% chance of below normal temperatures (highs < -7C) and a 20% chance of near normal temperatures (-4 to -7C)

So it appears that milder than normal conditions are favoured for the Grey Cup this year. If so, it would be the third consecutive time that Winnipeg has hosted the Grey Cup with mild weather (along with 2006 and 1998). But as any sports fan will tell you, underdogs can always win a game. So although mild weather is the odds on favourite this year, it only takes one storm system to bring in an untimely shot of snow and cold weather to southern Manitoba at the end of November, even during an El Nino year. This year's strong El Nino would lower the odds of that happening, but you can't rule it out completely. So let's hope the mightly forces of the El Nino Zephyrs from the west prove too strong for the punishing attack of the Arctic Express from the north. Go team El Nino!!


RECORD HIGH: +  7.2C (1932)
RECORD LOW:  -36.7C (1875)

NOV 19 2006 ........Clear. High + 1.5C, low -9.2C.   Kickoff temp: -3C
NOV 22 1998 ....... Sunny. High + 9.7C, low: 0.6C.  Kickoff temp: +5C. Record mild day!
NOV 24 1991 ....... Sunny. High - 15.6C, low: -21.9C. Kickoff temp: -16C

- Very strong El Nino pattern favours milder than normal conditions for late November
- 55% chance of highs > -4C on game day, 25% chance of highs < -7C

Sunday, October 11, 2015

Powerful winds expected overnight through Monday morning.. gusts of 100 km/h or more expected.

After an unseasonably warm and pleasant Thanksgiving weekend, the weather will be taking a dramatic turn tonight into Monday as a pair of cold fronts push across southern Manitoba. The first cold front is pushing through this evening and will shift balmy south breezes into the west with temperatures falling into the teens. A few showers and isolated thunderstorms are possible along this front with westerly wind gusts of 60 km/h possible. The second cold front will be pushing through the RRV early Monday morning, ushering in powerful NW winds and much cooler temperatures in the single digits.. a dramatic difference from Sunday's almost summerlike weather. The big story Monday however will be the winds.. with sustained north to NW winds of 60-70 km/h gusting to 100 km/h or more at times. This can lead to roof and tree damage as well as local power outages.  The strongest winds are expected between 4 am and noon in Winnipeg and the RRV, before the winds start diminishing somewhat in the afternoon (but still strong into the early evening)        

Note that a rare STORM force wind warning has been issued for Lake Manitoba and the south basin of Lake Winnipeg for Monday morning. Storm force wind warnings are issued for winds of 48 knots (90 km/h) or greater on the lakes. These warnings are seldom issued and are used only for the strongest windstorms on the lakes. As a result, mariners and cottage owners need to be prepared for very strong north to northwest winds off the south end of the lakes gusting to 100 km/h or more overnight through Monday morning, with major crashing waves causing local shoreline erosion. This is NOT a time to be on the water, so stay onshore Monday until winds subside.

So batten down the hatches.. a major change in the weather is on the way!  


Strongest wind gusts reported Oct 12 2015 
(EC and MB ag-wx stations) 

Starbuck .............. 104 km/h
Gretna ..................100 km/h
Victoria Beach ....... 96 km/h
Emerson ................ 96 km/h
Elm Creek ............. 96 km/h
Altona ..................  95 km/h
Winnipeg .............. 94 km/h
Treherne ............... 94 km/h
Morris ................... 86 km/h
Gimli ..................... 86 km/h