My parents sent me a few pictures of the damage around the cottage up at Golden Lake. Fortunately, our cottage was fine, but our neighbours’ properties have a lot of downed trees. Apparently, the neighbours saw a waterspout on the other side of the lake and there are unconfirmed reports of a tornado touching down in the area.

These are on our neighbour’s property:

Some poor U-Haul trailers at the storage place across the highway:

If you look closely, you’ll be able to make out the branches caught on the power lines that caught fire when the power was restored. A few seconds after my mom took this picture the line breaker on one of the poles blew with an impressive “bang!”. The firemen then put the flames out and stuck around to make sure that the fire didn’t flare up again.

A tip o’ the hat to my mom who took these photos.

I’ve been keeping an eye on the Franktown radar this afternoon. The storm that has been making its way down the Ottawa Valley has been tracking in the direction of the magenta arrow in this image:

If you’re in the path of the storm, you should probably take cover. Environment Canada has issued a number of tornado warnings for places in Eastern Ontario this afternoon.

My parents are at the cottage on Golden Lake (the lake immediately above the tail of the arrow) and they told me that they’ve never seen a storm like this one. Lots of trees and branches are down, the power’s out and so are the land lines. And apparently they can see “round 2” approaching. They’re in one of the places where a tornado warning has been issued, so hopefully they’re be ok!

It’s shaping up to be an interesting afternoon weather-wise. I took a look at the Franktown radar a few minutes ago and saw a large purple blog making its way towards Ottawa. The snapshot to the right is the most recent radar image (as of about 12:55) and the purple blob has spread out a bit and become a red and yellow blog that covers a slightly larger area. The track of the incoming weather suggests that the strongest part of the storm is going to pass just to the south of Ottawa, but that could change, of course, or the rain north of the blob could pick up some energy and develop into more exciting weather.

Looking at the weather trends for the last 24 hours, you can see the pressure had dropped since noon yesterday:

The aviation forecast suggests that we’ll see thunderstorms, possible including hail, from 3pm:

TAF AMD CYOW 231635Z 2316/2412 21010KT P6SM SCT060
FM231900 21015G25KT P6SM -TSRA BKN050CB TEMPO 2319/2320 VRB25G50KT 1/2SM +TSRAGR OVC040CB
FM232000 21015G25KT P6SM BKN050 TEMPO 2322/2401 VRB15G30KT 2SM TSRA OVC040CB
PROB30 2323/2401 VRB25G50KT 1/2SM +TSRAGR OVC040CB
FM240100 24010KT P6SM BKN040 TEMPO 2401/2408 6SM -SHRA BR BKN020
BECMG 2402/2404 28008KT
RMK NXT FCST BY 231800Z=

Fun stuff, eh?

As almost everyone certainly is aware by now, it’s hot in Ottawa today. The “low” this morning was about 20°C and it has hit 32°C for a high.

However, it feels much hotter than that because of the humidity. This perceived temperature is known as Humidex. Environment Canada reports the humidex whenever the temperature is at least 20°C and the dew point (the temperature at which the moisture in the air will condense) is above 0°C and when the humidex is at least 25. So, on hot muggy days, you’re probably going to see a humidex value in the weather reports, which you can see in this graph that shows the air pressure (blue), temperature (red) and humidex (orange) for the last 24 hours in Ottawa:

You can calculate the humidex yourself using the formula found on Environment Canada’s website, which I’ve adapted slightly for clarity:

[math]a=6.11 * e^{(5417.7530 * (\frac{1}{273.16} – \frac{1}{(dewpoint+273.16)}))}[/math]

[math]b=(0.5555) * (a-10.0)[/math]

[math]Humidex=temperature + b[/math]

The “e” in the first equation is a mathematical constant that is approximately equal to 2.7182818284.

So, if the temperature is 32°C and the dewpoint is 23°C, the humidex will be 42 when you plug the numbers into the equations and round up. According to the Canadian Centre for Occupational Health and Safety, a humidex of 42 will cause “great discomfort” and you should “avoid exertion”.

Of course, it’s the Wednesday before the Ottawa Dragon Boat Race Festival, which means I have two dragonboat practices this evening. At least I’m steering rather than paddling! If we’re lucky, maybe the 30% probabiliy of thunderstorms will transpire and knock some of the humidity out of the air:

TAF CYOW 202038Z 2021/2118 22007KT P6SM SCT050
PROB30 2022/2024 VRB15G25KT 2SM TSRA BR BKN015 OVC040CB
FM210000 26005KT P6SM FEW040
BECMG 2114/2116 22012KT
RMK NXT FCST BY 210000Z=

The thunderstorms arrived a bit ahead of schedule, but not excessively so:

SPECI CYOW 291837Z 24010G20KT 10SM TS BKN061CB 31/18 A2953 RMK CB7 CB SSW-N + E-SSE SLP000 DENSITY ALT 2700FT=

Basically, the TAF from this morning forecast their arrival as early as 3pm, but they arrived at 2:37pm — 23 minutes early. The SPECI observation reported the wind from the SW at 10 gusting 20 knots, 10 miles visibility, moderate thunderstorms, ceiling at 6100′ consisting of cumulonimbus clouds (CB). The remarks basically that that there were CBs pretty much surrounding the airport except to the south and northeast. The density altitude of 2700′ is pretty impressive given that the airport is at 374′ ASL, so the air pressure was very low — as evidenced by the altimeter setting of 29.53″ Hg (compared to the standard of 29.92″ Hg). Not too surprising given the temperature was 31C at the time.

I thought I’d take a look at the TAF to see if they had issued a new one from the one in my previous post and sure enough it was amended this afternoon:

TAF AMD CYOW 291842Z 2918/3018 24012G22KT P6SM BKN040
TEMPO 2918/3001 VRB20G35KT 1SM +TSRA BR BKN006 OVC030CB
FM300100 23008KT P6SM BKN140
BECMG 3002/3003 27008KT
FM300500 28005KT P6SM SKC
FM301500 29012KT P6SM FEW060
RMK NXT FCST BY 292100Z

Previously, the thunderstorms were a 40% probability, but I guess when they actually happen it’s time to change that to TEMPO (occurences of less than an hour). 🙂

It looks like the weather this afternoon could be exciting:

TAF CYOW 291441Z 2915/3012 VRB03KT P6SM FEW200
BECMG 2915/2917 20012KT
FM291900 20012G22KT P6SM BKN040 PROB40 2919/2923 VRB20G35KT 1SM +TSRA BR BKN006 OVC030CB
FM292300 23008KT P6SM BKN140
BECMG 3000/3002 28010KT
FM300500 28005KT P6SM SKC
RMK NXT FCST BY 291800Z=

The section I’ve highlighted in red basically says that between 3pm and 7pm today there is a 40% probability that the winds will be 20 knots gusting to 35 knots (37 to 65 km/h) from variable directions (in other words, from any direction) with 1 mile visibility and heavy thunderstorms and rain (+TSRA) and very low clouds (ceiling at 600′) and cumulonimbus clouds.

And Environment Canada’s special weather statement this morning included the following:

Today..Scattered thunderstorms are expected across southern Ontario. There is a slight risk they may be severe with damaging winds, large hail and torrential downpours. An isolated tornado is also possible in Extreme Eastern Ontario near the Quebec border. Also, isolated non-severe thunderstorms are possible over Northeastern Ontario near the Quebec border.

The storm that blasted through the area last Friday evening spawned a couple of tornados in Quebec, so hopefully people will heed the warning. Speaking of watches and warnings, it appears that we’ve been under a severe thunderstorm watch since mid-morning:

Ottawa North – Kanata – Orléans
10:48 AM EDT Tuesday 29 May 2012
Severe thunderstorm watch for
Ottawa North – Kanata – Orléans issued

Potential for severe thunderstorms this afternoon.

This is an alert to the potential development of severe thunderstorms with large hail, damaging winds or heavy rainfall..Monitor weather conditions and listen for updated bulletins.

A cold front will move through Eastern Ontario this afternoon which will trigger thunderstorms. Some of these thunderstorms may become severe with damaging winds and heavy downpours being the main threats. The cold front will move out of Ontario by early evening bringing an end to the threat of severe thunderstorms.

So, keep an eye on the Franktown radar this afternoon. If you see a line of orange, reds and purples or little groups of reds and purples, chances are good that’s where the thunderstorms are. If you happen to be in their path, take cover.

In addition to the pictures I posted of yesterday’s storm, I took a couple of videos as a massive wall of rain and wind crossed the Ottawa River just upstream of Bate Island.