TorontoForecast.com - Blog

Another exciting day for weather enthusiasts here in Southern Ontario. Thunderstorm watches were issued right before lunchtime all over Southern Ontario in anticipation of more thunderstorms in the region.

The first round hit north of the city around lunchtime in Markham and Richmond Hill area. Heavy rain and hail pounded the area. Then a major cell hit the Toronto East York area around 1400 EDT (finally). The event was preceded by darkening clouds as indicated by the graph below:

The solar radiation reading from our weather station dropped from:

1333 EDT: 800 W/m2

1334 EDT: 281 W/m2

1349 EDT: 95 W/m2

1437 to 1449 EDT: 5 W/m2

As shown in the graph, temperature also dropped significantly during the peak of the storm. In fact, temperature fell 2 degrees from 15.8 deg. C to 13.8 deg. C in ten minutes (1452 to 1502 EDT).

I have some images of the radar but I forgot to transfer it from my office computer. Nevertheless, here is a graph of the maximum rainfall rate in the Toronto East York (Sunnybrook Park area) from my weather station:

For 9 minutes, the maximum rainfall rate exceeded 100 mm/hr. The highest rainfall rate from the thunderstorm was 195.2 mm/hr, one of the highest ever recorded this year. After about 30 minutes of lightning show and heavy rain, the final rainfall total is 33.8 mm.

Nature of thunderstorms is local; that is, one area can be pounded by heavy rain while ten blocks away, it’s just cloudy. As an example, here is the rainfall accumulation for today:

Toronto East York (TorontoForecast.com weather station) - east side of the city: 34.0 mm

Toronto Pearson International Airport - west side of the city: only 2.4 mm

York University weather station - north end of the city: 25 mm

Toronto City - downtown: 10 mm

Like I said in my previous blogs, weather is local.

Nevertheless, today’s storm brought our monthly total rainfall so far to 151.8 mm and more rain is in the forecast.

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