TorontoForecast.com - Blog

If you’re in the Great Lakes region, expect to experience more rain and winds for the next 24 hours.  Southern Ontario had its first round of rain Saturday night courtesy of the remnants of Tropical Storm Lowell.  TS Lowell formed in Mexico but its remnants moved eastward and joined a cold front that brought heavy rain in Southern Ontario.  Here are some notable 24-hour rainfall total ending at 2:00 a.m. September 14:

Windsor:  75.2 mm

Goderich:  57.8 mm

Harrow AAFC:  56.1 mm

Ridgetown:  47.9 mm

Eriaeu:  42.0 mm

Elora:  40.8 mm

In the Toronto region, here are the 24-hour totals as of 2:00 a.m., September 14:

Buttonville Airport:  26.0 mm (broke the old record of 21.6 mm set in 1996)

Toronto Downtown:  18.5 mm

Toronto East York (www.TorontoForecast.com):  15.6 mm

Toronto City Centre:  15.0 mm

Toronto Pearson:  14.8 mm

Starting at 6 pm tonight, the Greater Toronto Area will feel effect of the remnants of another tropical storm, Hurricane Ike.  Hurricane Ike was a category 2 hurricane when it hit Galveston, Texas Saturday morning.  Computer models are showing that the centre of the low will stay northwest of the city so the heaviest rain will be in communities near Lake Huron.

Based on which computer model you refer to, the bulk of the precipitation will hit around 6 pm with the heaviest rainfall around midnight.  Scattered thunderstorms can increase total precipitation but current models indicate that the GTA will receive between 25 and 45 mm of rain before it’s over by early Monday morning.

The event will also be accompanied by very low SLP at around 992 mb and strong southerly winds gusting to 70 km/h shifting to the NW early Monday morning.

For the latest weather forecast and observations, visit our main site:

www.TorontoForecast.com

http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=IONTORON16

Our latest weather update will be released on Monday morning with rainfall totals in Southern Ontario.

Feel free to leave a comment or two.

Weather is local!

Kristoffer Moraleja

It’s official! The wettest summer on record (if you based it on Toronto Pearson’s weather data). As of August 10th, here’s the cumulative rainfall record from June 1st:

Three of the four stations exceeded the 300 mm mark and I won’t be surprised if we hit the 400 mm level before the month is over. More rain is in the forecast with slightly below temperatures.

For comparison, here’s the five wettest summer at Toronto Pearson Airport:

Note that the climatological summer spans from June to August. The all-time record from the downtown weather station is still standing at 402.6 mm.

In my next weather blog, we’ll explore the standard in measuring rainfall. If you’re interested on snowfall measurements and world record snowfall accumulations, please refer to my previous blogs last winter.

For the latest weather forecast and models, visit out main site: www.TorontoForecast.com

Feel free to leave a comment or two

KLM

Unsettled weather pattern throughout the month of July produced bouts of showers and thunderstorms in the Greater Toronto Area. Although most weather stations exceeded the 100 mm mark, rainfall was not distributed evenly throughout the city due to unpredictable and localized nature of thunderstorms. As elucidated in the Toronto July Weather Summary Table below, the west end of the city received the most rain while northern communities received almost 4 inches (100 mm) less than Toronto Pearson Airport.

In terms of average temperatures, the Toronto East York was the warmest spot while the Island Airport, as expected, was the coolest location due to lake breeze effect.

Nevertheless, the total precipitation at Pearson Airport is quite impressive considering not only the July monthly rainfall record was broken, the cumulative June-July rainfall is also a record.

However, the all-time July rainfall record of 206.8 mm at the Toronto Downtown weather station remains untouched.

For the complete weather summary including graphs and records for the Toronto East York Weather Station, click on the links below:

Table: toronto-east-york-weather-summary-july-2008.pdf

Graph: toronto-east-york-weather-summary-graphs-july-2008.pdf

For your daily weather needs, visit our main site: www.TorontoForecast.com

Feel free to leave a comment or two

You’ve probably noticed that the ground is wetter than usual these days.  It’s no surprise then to see many mushrooms popping up in your lawns lately.   So far, all weather stations around the city of Toronto has reported above average precipitation for the month of July.

 Here’s the breakdown as of July 21st:

Toronto East York (www.TorontoForecast.com):  74.6 mm

Toronto City (downtown):  99.8 mm

Toronto City Centre (Island Airport):  100.0 mm

TheWeatherNetwork (Oakville):  121.7 mm

Burnhamthorpe:  123.1 mm

Toronto Pearson:  130.0 mm

As you’ve noticed, as you move westward in the city, the total precipitation increases.  Here’s a proof based on the weekly total precipitation from July 15th to 22nd (Intellicast.com):

For reference, Toronto Pearson is labelled as CYYZ inside the orange box.  The image shows that areas in the west received between 25 and 75 mm of rain while on the east side, it’s 50 mm or less.

The water levels are also dangerously deeper than average. Here are some stats between July 20th and 21st from some hydrometric stations in the city:

Don River at Todmorden:  water rose from 12.1 m to 13.7 m

Don River at York Mills:  water rose from 0.6 m to 1.6 m

West Highland Creek at Scarborough Village:  water rose from 2.5 to 3.7 m

Therefore, enjoy visiting the parks but be careful when walking near rivers and creeks.

Finally, we’ve updated our main weather site so don’t forget to visit it:  www.TorontoForecast.com

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The numbers are in and June is one of the hottest and wettest ever. Click the links below for the weather summary and graphs (pdf version).

Toronto East York June Graphs:
toronto-east-york-weather-summary-graphs-june-2008.pdf

Toronto East York June Table:

toronto-east-york-weather-summary-june-2008.pdf

Read the comments from my previous blogs for more detailed weather analysis including radar and satellite images.

Our main site, www.TorontoForecast.com, is currently undergoing major improvements. The final version is expected to finish late this week so keep visiting.

Please feel free to comment on any of the blogs featured here. I would love to hear from you.

Enjoy the site

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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A stubborn low pressure system centred in Northern Ontario has created a moist and unstable airmass in the Great Lakes region. The reason for the prolong period of moist and cloudy day is because the low pressure system is not being propelled by the continental jet stream. As a result, it has relatively stayed at its location not moving easterly, which is typical of most systems under the influence of a jetstream.

Nevertheless, northern parts of the city of Toronto was battered with hail, heavy rain and frequent thunder and lightning. The most impressive cells battered a quadrant covering Islington Avenue to Yonge Street and Sheppard Ave West to Steeles Avenue West. Fortunately, a trusted weather station is located in the worst part of the storm. The York University weather station was battered by heavy rain and hail for at least half an hour. The total rainfall was 48.1 mm, with rainfall rates exceeding 50 mm/hr (could be higher but the graph legend only goes up to 50 mm/hr).

Here are some images from the most affected area:

Note that the cell north of the city remained in the same area for at least half an hour. The Atmospheric Environment Service of Environment Canada in G. Ross Lord Park was also bombarded with heavy rain and frequent lightning. At the time of posting, no report yet of rainfall total from the AES Headquarter location.

I would have to contact Dr. Peter Taylor of York University to obtain the rainfall extreme and wind gust when the storm passed the campus. Nevertheless, I wished the storm moved a few kilometeres south to Toronto East York.

The total monthly rainfall so far here at Toronto East York is 117.6 mm with our huge deluge of 43.6 mm on the 15th of June. In the last ten days, we accumulated 82.6 mm of rain. Therefore, I don’t think we need to water our plants this week considering more showers are expected in the next seven days.

Major site improvement in www.TorontoForecast.com on Canada Day. Please submit your suggestions on what do you want to see in the site.

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What an amazing day! With unstable airmass induced by a moisture-laden atmosphere and lake breezes, the Greater Toronto Area was pounded by impressive thunderstorms today. Thunderstorm watches and warnings were issued for most of Southern Ontario and Toronto is one of the worst hit area. Toronto Pearson International Airport recorded a wind gust of 98 km/h at 1832 EDT.

Here at Toronto East York (Sunnybrook area), three distinct cells hit the area with the worst one occurred around 1400 EDT. Here are the radar images when the main cell hit our station (indicated by the temperature reading of 76 deg. F):

Here is another radar view:

The table below shows the weather conditions during the storm:

Note that for 10 full minutes, the rainfall rate was in excess of 100 mm/hr. For two minutes, the rainfall rate peaked at 426.6 mm/hr - the highest ever recorded by the Toronto East York weather station. I never experienced such storm before in Toronto - sheet of rain with visibility less than 10 feet, frequent lightning and thunder and pea-sized hail.

It was also unusually dark. The solar radiation reading dropped from 800 W/m2 to 139 W/m2 in one minute (1555 EDT to 1556 EDT). The reading dipped to 84 W/m2 at 1606 EDT during the heavy deluge.

We received 26.0 mm of rain in 20 minutes - another extreme record. You will also notice that the pressure dropped significantly during the storm and winds gusted to 37 km/h.

In fact, the storm was so severe that I called the weather hot line of The Weather Network and e-mailed Brian Hill of 680 News, Michael Kuss of CityTV and Environment Canada.

Minor cells followed in late afternoon and another strong cell hit the area just before 2000 EDT. Essentially, Toronto was in an outflow boundary - a storm-scale boundary separating thunderstorm-cooled air (outflow) from the surrounding air; similar in effect to a cold front, with passage marked by a wind shift and usually a drop in temperature. Here is the storm track for the evening storm:

A more close-up view of Toronto East York station after the passage of the cell (just north of the East York map marking):

Weather conditions from the evening storm (table and graph):

The peak wind gust was 42 km/h!

Note the drop in temperature and excessive rain for more than five minutes. The peak rainfall rate this time was 202.2 mm/hr.

It’s past 2330 EDT and it’s still raining. The total rainfall so far is 43.6 mm and it’s the most rain we ever got here at Toronto East York in less than 12 hours. I won’t be surprised to surpass the 50 mm before the 0200 EDT, the end of a climatological day.

Stay safe and please feel free to leave a comment.

KLM

It’s been a while since I updated my blog. It’s summer by the way and I’m enjoying every bit of it. Furthermore, major updates in our major site, www.TorontoForecast.com, on Canada Day but more on that in another blog.

In the last four days, Southern Ontario has been suffering from an extended period of heat and humidity. Humidex advisories, t-storm warnings and even a tornado watch have been issued. Here is a brief summary of maximum temperatures and THSW index (combination of temperature, humidity, sun and wind readings):

May 6: 33.8 deg. C (THSW: 44)

May 7: 32.5 deg. C (THSW: 41)

May 8: 34.5 deg. C (THSW: 44)

May 9: 35.1 deg. C (THSW: 46)

As you can see, today is the hottest day so far and it felt like 46 this afternoon. Of course, we also have the perfect ingredient for severe t-storms. As of 22:55 EDT, we already received 18.0 mm of rain and it’s still raining. We got some major impressive cells this afternoon and at 16:31 EDT, we recorded a rainfall rate of 303.2 mm/hr!

Here are some radar images of nocturnal t-storms in the area (Toronto East York weather station is indicated by a temperature of 76 deg. F in the map in Sunnybrook Park area):

Don’t forget to visit our main site: www.TorontoForecast.com

Cheers,

KLM

What a wonderful day to be outside today. The weather is perfect with comfortable temperature and lots of sunshine. I also noticed that people are often in better mood in this kind of weather and with air quality index readings in the good category, what else could you ask more? I had a delightful walk in downtown Toronto during my lunch today and I enjoyed every minute of it.

For today’s summary, here are the observed max. and min. temperatures in the city:

Toronto Pearson: 21.0 / 8.2

Buttonville Airport: 22.1 / 8.6

Downtown Toronto: 20.1 / 10.2

Toronto City Centre: 17.6 / 9.5

Toronto East York PWS: 22.7 / 9.6

The hot spot in Ontario is Bancroft with a high today of 23.3 deg. C while nationwide, Maniwaki, Quebec reached 24.1 deg. C. If you’re wondering where’s the coldest place in Canada today, it’s Mould Bay, NWT with a low of -17.0 deg. C this morning while Peawanuck is the coldest in the province with a low of -5.6 deg. C. In fact Environment Canada issued a special weather statement for Northern Ontario for a mixture of wet snow and freezing rain.

Here in Toronto, we will get wet but at least it’s the liquid type. The cold front from the low pressure system centred in Northern Ontario will reach the Detroit/Windsor area around lunch time and the Horseshoe region late afternoon/early evening. I expect that the pressure will drop around 1005 mb with strong southerly winds (up to 55 km/h) shifting to WNW in the evening. Rainfall will be light (6-8 mm) unless we got lucky and get thunderstorm. The Storm Prediction Center in the US has put the Great Lakes under slight risk level of having thunderstorm tomorrow. Our next round of precipitation is on Friday night extending to Saturday and cooler weather will persist at least until the end of next week.

Enjoy the weather!

For the latest weather forecast and computer models, visit our site: www.TorontoForecast.com

As predicated in my May 5th blog, Toronto was battered with strong easterly winds gusting up to 50 km/h. Our Mother’s Day trip to the Toronto Botanical Garden was quite an experience considering the high was only 15.4 deg. C but the lack of sunshine and howling winds made the apparent temperature closer to 10 deg. C. On a positive note, I was happy to see a weather station at the botanical garden.

Luckily, the center of the storm stayed south of us resulting in less impressive rainfall amounts. The American Midwest was inundated with tornado warnings issued in Kansas, Oklahoma and Missouri to name a few. In Newton County, Missouri ten people were reported to be killed while six people lost their lives when a tornado ripped a 20-block area in Picher, Oklahoma. Furthermore, a 4.25 inch (10.8 cm) diameter hail was reported in Baxter Springs, Kansas.

As of 6:00 pm, the low was centered in Missouri with a SLP well below 990 mb. Here in Toronto, I expect the pressure to dip to around 1000 mb and rainfall amounts less than 5 mm.

It’s Sunday and here’s the first report on the temperature accuracy study. The root mean square error (RMSE) is a quadratic scoring rule which measures the average magnitude of the error. Since the errors are squared before they are averaged, the RMSE gives a relatively high weight to large errors.

I have also added the mean absolute error (MAE) into the calculation which is the weighted average of the absolute errors (i.e. Ipredicted-actualI). Since we just started our analysis a few days ago, please note that the values below only cover the period of May 9-10. Any statistician will tell you that your analysis is more meaningful if you have more data. Therefore, we will have a better picture of which weather source provides the most accurate forecast once we have a bigger sample. Nevertheless, here is the preliminary result:

So far, Environment Canada (EC), The Weather Network (TWN) and The Weather Channel (Weather.com) have the best record with RMSE and MAE of 1.0 deg. C. Note that the lower the value, the better their forecast (i.e. closest to actual observed temperature).

For latest weather information and live weather readings, visit our site: www.TorontoForecast.com

Feel free to comment

With many sources of weather forecasts, one could wonder why the predicted forecast high for Toronto varies depending on your source. Of course, one can argue that temperature readings closer to the lake will be much different from one further inland. However, when forecasters predict the maximum temperature, they often refer to what’s expected at the airport. As such, I decided to conduct a study for the next six months as to which weather source has the highest % of having the correct forecast. It is important to remember though that weather forecasting is still a relatively young science and weather prediction is still imperfect. Therefore, this mini-study is not meant to criticize the skill or accuracy of the weather source but hopefully allow us to appreciate how difficult it is to forecast weather. As the adage goes, “Don’t shoot the messenger.”

Methodology: The next day maximum temperature forecast will be obtained at 10:00 pm Eastern Time the night before from the following sources:

• Environment Canada - government run weather agency

• The Weather Network - private Canadian weather company owned by Pelmorex Inc.

• 680 NEWS AM radion station - offers a Weather Guarantee Contest

• CityTV - lead meteorologist Michael Kuss

• GlobalTV - lead meteorologist Anthony Farnell

• Accuweather.com - international private weather company

• Weather.com - private American weather company

The sites were chosen because the weather forecasts are readily available through the Internet and therefore we can compare their temperature forecast high as of 10:00 pm. The official observed maximum temperature will be based from Toronto Pearson International Airport’s (CYYZ) observation as reported from the National Climate Data and Information Archive.

Comparison Calculation: The maximum temperature forecast error will be calculated by subtracting the maximum temperature forecast from the observed maximum temperature, and squaring the result. This method of calculation is called the root mean square error (RMS) where the individiual errors are squared, added, then divided by the number of errors (ie, the number of observations) and the square rooted. In essence, it summarizes the overall error and you maintain the units, degrees Celsius. It will also help us determine which one can provide the most correct forecast rather than the one who can give us the exact temperature forecast.

I will post the results on a weekly basis every Sunday and the final analysis will be revealed six months from now. To start our study, the 10:00 pm forecast for Friday, May 9, 2008 is as follows:

Environment Canada - 16 deg. C

The Weather Network - 14 deg. C

680 NEWS AM radion station - 18 deg. C

CityTV - 14 deg. C

GlobalTV - 15 deg. C

Accuweather.com - 18 deg. C

Weather.com - 16 deg. C

As you can see, the temperature forecast spread is 4 deg. C and it will be interesting indeed to watch their forecasts in the weeks and months ahead.

For Toronto climate information, visit our main site: www.TorontoForecast.com

With rain in the forecast, it is a great opportunity to explore the May precipitation records in Toronto. Based on Toronto Pearson’s 71 years of weather records, here are the extremes:

24-hour precipitation record: 92.7 mm (May 31, 1944)

24-hour snowfall record: 2.3 cm (May 7, 1976) and trace of snow on the ground

Wettest May: 208.6 mm (1942)

Driest May: 9.4 mm (1949)

Four of the 20 wettest days in the history of CYYZ (>50 mm) occurred in the month of May:

May 15, 1942 - 50.3 mm

May 31, 1944 - 92.7 mm

May 16, 1974 - 53.1 mm

May 12, 2000 - 53.8 mm

The wettest May endured five major weather systems with the most intense one occurred during the last three days of the month in 1942. The three day rainfall total was 60.4 mm where 58.9 mm fell in just two days! Although the center of the low was in the Minnesota and Iowa border, the warm front extended up to Eastern New York. With strong southerly winds and humid conditions, it felt like mid-summer than late spring. Maximum temperature peaked at 30.0 deg. C and the mean was a mild 22.5 deg. C.

Below is the weather map forecast produced by the U.S. Department of Commerce Weather Bureau on May 31st, 1942.

The weather map was produced from the Washington, D.C. weather bureau and forecasts can be obtained using automated phone messages. Note, however, that the forecast map was not released full 7 days after it was created. Imagine Environment Canada releasing weather “forecast” maps for what happened last week.

Current indications reveal that the mean temperature for the next 10 days will be below normal. Environment Canada’s mean temp anomaly shows that Southern Ontario will be around 0.5 to 0.8 deg. C below normal while the National Weather Service in the US puts a 70% probability of being below normal.

The continental map below courtesy of the National Centers for Environmental Prediction and the Center for Ocean-Land-Atmosphere Studies predicts that areas west of Quebec with the exception of the territories will experience below seasonal temperatures.

Southern Ontario will also experience bouts of rain resulting in cloud cover and temperatures in the low to mid teens. Current weather models don’t show a lot of convection from these systems but I’m watching for the one that’s expected to arrive early next week. Although it’s still too early for actual rainfall amounts but winds will be strong from the east gusting to 50 km/h and SLP of around 990 mb.

For live weather conditions, visit www.TorontoForecast.com

The major low pressure system that has been affecting Southern Ontario in the past three days finally exited the area but it left copious amounts of rain. The system was much stronger when it hit the American Midwest resulting in about 82 tornado & 217 severe wind reports and 457 severe t-storm warnings.

The climax reached Toronto at 1700 EDT where a line of heavy rain pounded the area. The continental water vapour content map shows that the moisture extends from the Gulf of Mexico all the way up to James Bay in northern Ontario/Quebec.

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Based on radar estimate, the rainfall intensity peaked around 45-50 dBZ as the line moved in a northeasterly direction. In the radar map below, storm “C8″ located in Markham had a cloud top of approximately 10,000 feet, Vertical Integrated Liquid (VIL) of 7kg/m2 and it’s moving to the NE at 38 knots.

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When the line hit the east side of the city at 1715 EDT, it brought heavy rain and strong winds. Here is a snapshot of the radar image as it pounded the Toronto East York Weather Station (look at the station in the East York area with a temp reading of 54 F).

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In fact the passage of the storm line resulted in rapid temperature dropped and rise in barometric pressure as indicated in the graph below from the Toronto East York weather station. The pressure rose from 1003.6 mb to 1005.1 mb in just one minute (17:13 to 17:14 EDT).

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Closer analysis indicated that the temperature dropped 2.3 deg. C from 15.0 deg. C to 12.7 deg. C in a matter of ten minutes (17:12 to 17:22 EDT). For five minutes, the rainfall rate was more than 100 mm/hr until it reached the peak at 160 mm/hr at 17:20 EDT.

In the end, the 24-hour rainfall accumulation was 16.8 mm and the total storm accumulation from May 1-3 is 25.8 mm. For more weather information and live weather readings, visit www.TorontoForecast.com.

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