Wednesday, 27 August 2014

Warmer; Some Storm Chances

     Nothing but sun in the RRV today. I'm expecting a high around 23-24°C in Winnipeg. Warmer night tonight with lows in the low teens. Much better than the 7.9°C low this morning at the airport.

     The sun continues tomorrow as temperatures reach high 20's. Highs around 27-28°C look likely for Winnipeg. There will be a risk for thunderstorms in southwestern Manitoba in the evening as a cold front approaches. An isolated severe storm cannot be ruled out there.

     A cloudy start to Friday with a chance of showers and thunderstorms associated with the cold front. Skies should clear for the afternoon, but it will be cooler behind the front with highs only in the low 20's.

     Looks like we will warmup already for Saturday with highs in the mid 20's. Another cold front moves into southwestern Manitoba late in the day which could bring some more thunderstorm activity to the area. Again, isolated severe storms cannot be ruled out closer to the Saskatchewan border. That front will pass through the RRV on Sunday bringing a chance for showers and thunderstorms again.

Tuesday, 26 August 2014

March to August Temperature Forecast Evaluation

     It is time to look back and see how my Winnipeg forecast, issued daily in the 'Winnipeg Forecast' tab, has faired. I have only evaluated the temperature forecast due to the fact that precipitation and wind forecasts are a little trickier to compare with other forecasts. Different weather agencies have different methods of giving out precipitation and wind forecasts. Some will give you a range, others will give more precise values. This makes it difficult to compare their forecasts with mine. Temperatures are not a problem because all forecasts will give just one specific value as their forecast.

     The evaluation period goes from March 1, 2014 to August 23, 2014. To evaluate how my temperature forecasts have faired, I have compared them to forecasts by various sources: Environment Canada, The Weather Network, Intellicast, Accuweather, A Weather Moment and CBC Manitoba. I will not give the specific results of these sources, because I feel I should not do so if I do not have their permission. Instead, I will compare the results of my forecast with the average result across all sources.

     First, the following table shows what percentage of temperature forecasts were PERFECT. For example, a forecast high of 33°C would be considered a perfect forecast if the actual high was between 32.5°C and 33.9°C.

Table 1: Percentage of temperature forecasts that were perfect (from March 1, 2014 to August 23, 2014)

My forecasts
Average of all sources
Range of all sources
Day 1 high
Day 2 AM low
Day 2 high
Day 3 AM low
Day 3 high


     I am happy with the results. My forecasts had the highest percentage of perfect forecasts for both the day 1 and day 2 highs. May and July were the best months for the day 1 forecast with percentages of 58% ad 62% respectively. May was an exceptional month considering the average across all sources was just 32%. Interestingly, day 2 forecasts in July faired better than the day 1 forecasts. 66% of day 2 forecasts were perfect that month. Day 3 high forecasts continue to be my downfall, averaging slightly below average.

    Overall, considering all the temperature forecasts from day 1 to day 3, July was the best month (47%) and March the worst (27%). This is to be expected because temperatures tend to be less predictable in the colder months versus the warmer months.

     The last table below shows the percentage of forecasts that were WITHIN 1°C of the actual value. For example, a forecast high of 33°C would be considered within 1°C of actual if the actual high was between 31.5°C and 34.9°C.

Table 2: Percentage of temperature forecasts that were within 1°C of actual (from March 1, 2014 to August 23, 2014)

My forecasts
Average of all sources
Range of all sources
Day 1 high
Day 2 AM low
Day 2 high
Day 3 AM low
Day 3 high


     Again, day 1 high forecasts continue to be my strength. July was the best month with 97% of day 1 forecasts being within 1°C of actual. March was the worst at 68%. Overall, all forecasts from day 1 day 3 were within 1°C of actual 66% of the time, above the average of 63% across all sources. July was my best month at 83% and May the worst at 53%.

     I will continue to compare my forecasts with other forecasts for the foreseeable future. It has become a goal of mine to continue to remain above average and provide the best day 1 to day 3 temperature forecasts for Winnipeg. Unless interest is high, I don't plan to give another evaluation post like this one until next spring. Thanks for reading :)

Sunday, 24 August 2014

Thunderstorm Potential Today; October-Like Tomorrow

     Thunderstorms did not materialize in the RRV and southeastern Manitoba overnight. However, widespread rains still managed to dump some decent rainfall totals. In Winnipeg, generally 15-25 mm of rain fell from yesterday evening to 9 am this morning, including:

South St Vital 21.8 mm
Norwood 21 mm (via Brad)
Charleswood 20.8 mm
Winnipeg Airport 18-19 mm

      Winnipeg actually ended up on the lower end of things as most of the RRV and southeastern Manitoba actually got more. Generally, 25-45 mm fell in the remainder of the RRV and in southeastern Mantioba. Steinbach, Morden and Somerset have received some of the highest totals with 43.1 mm, 41 mm and 44.0 mm respectively, since yesterday (according to Manitoba Agriculture and Environment Canada).

     Highest totals so far have been in southwestern Manitoba and in the Interlake. Generally 40-50 mm has fallen in the Interlake in just the past 9 hours. Even higher amounts of 45-65 mm have already fallen in extreme southwestern Manitoba, west and southwest of Brandon:

Reston 63.6 mm
Pierson 62.2 mm
Melita 54 mm
Bede 52.8 mm
Virden 46.1 mm
Deloraine 42.6 mm

     Rain will taper off later this morning for the RRV. As the centre of low pressure and a cold front swing through this afternoon and evening, thunderstorms may develop. Some of these may be strong with hail, strong winds and funnel clouds possible. However, severe potential is contingent on some sunshine in southern Manitoba today. There is some clearing moving in from North Dakota this morning, but it's still hard to say if this will fill up with cloud later on. Depending on how much sun we can get, severe thunderstorms will be possible in the RRV and southeastern Manitoba. It will also be quite humid this afternoon with dewpoints in the low 20's, forcing temperatures into the mid 20's for some.

     MUCH colder tomorrow behind the system. Temperatures will remain steady in the low teens. This, combined with breezy west-northwest winds and shower activity, will make tomorrow feel more like October.

     Warming up later in the week with highs in the high teens Tuesday, low 20's on Wednesday and even warmer for the end of the week.

Friday, 22 August 2014

More Rain to Come

     A very slow-moving cold front last night in the RRV helped trigger one of the biggest rain events of the year in Winnipeg. A heavy thunderstorm remained stationary over central and southwestern parts of the city for over an hour. Generally 40-80 mm of rain fell from Charleswood to Whyte Ridge to dowtown. Much lower amounts fell in southeastern, eastern and northern parts of the city where amounts ranged anywhere from a trace mm to 30 mm. I received 16 mm here in River Park South. Here are some amounts from yesterday via Cocorahs, Weatherfarm, Environment Canada and other backyard stations (Robsobs, Kyle, Matt and myself) (including the rains from the morning):

Rainfall total August 21, 2014
Whyte Ridge
60-84 mm
Bridgwater Forest
70 + mm
57-66 mm
Downtown (UofW)
64.8 mm
St James
50.6 mm
41.9 mm
Old St Vital
29-31 mm
South St Vital
17.9 mm to 31 mm
Wpg Int’l Airport
20.6 mm
5-7 mm

    Considering the normal August rainfall in Winnipeg is 79.2 mm, some parts of the city saw a month's worth of rain in just 2 hours. It's no mystery that there was major road-flooding last night. The rain is also on top of another heavy rain event in the Lindenwoods area  (30-40 mm) back on Monday.

     It was also extremely moist/humid yesterday. With a maximum dewpoint observation of 21.5°C at the airport at 6:00 pm, we were just shy of a dewpoint record (old is 21.7°C in 1969). However, the minimum dewpoint observation yesterday was just 17.2°C, a record high minimum for the day. Old record high minimum dewpoint was 15.1°C in 1981.

     Unfortunately, the gloomy weather continues. Cloudy skies are expected today and tomorrow with minimal breaks in the cloud. A bit of drizzle or light rain may fall at times before the big rain event tomorrow night.

More rain is on the way
     A strong low pressure system moving up from the United States will bring a widespread rain event to southern Manitoba late tomorrow into Sunday. At this time, it appears the bulk of the rain will begin tomorrow evening for Winnipeg and last until Sunday morning. The rain may be quite heavy at times and there may be a few embedded thunderstorms. 15-30 mm or more could fall throughout the RRV and southeastern Manitoba, including Winnipeg. Localized amounts up to 40 mm are possible under the heaviest bands and if any thunderstorms do occur, but most areas will see less than that. Stay tuned in the comments below for updates.

     Scattered showers with embedded thunderstorms remain possible through the afternoon and evening on Sunday. There could even be some sun, allowing temperatures to reach low 20's. Generally cloudy skies look to continue Monday with a few showers possible at times. Chilly, fall-like conditions look to continue through to mid-week before things begin to warmup by the end of the week.