Sunday, October 1, 2017

September 2017 Summary

Some historical temperatures during a dry September 

Well that was quite an end to September with the longest heat wave of the “summer” and some historical temperatures.  The most significant streak was the 15 days above 25°C between the 12th and the 26th, that is something we have never seen before in September during the 100+ years of weather records in the region (the previous record was 13 such days back in 1947).

Some other notable events were the 5 days in a row above 30°C, which is something we have only seen a few times, the last was back in 1952.  Finally, the high temperature on the 24th of 32.2°C was the highest seen that late in the year since September 24, 1931 when it was 32.8°C.

Not surprisingly, the overall temperature was almost 3 degrees above average, what might be surprising is that this is colder than the last 2 years although they didn’t have the extreme highs we saw this year.  It is also useful to remember that this year the month started off cool during the first week.

But since I have you here can we talk a bit about recent Septembers?  Fun fact: no other month has seen more consistently above average temperatures.  In the past 20 years of data at the UW weather station, there has not been one in the below average range and only once was it even slightly below average (by 0.1 degrees in 2006).

The month was also very dry with only 38.0 mm of precipitation compared to the average of 87.8 mm, with half of the total coming during the first 4 days.  This dry month puts the total precipitation for the year at 813.4 mm, which is still well above, but a bit closer to the average of 683.5 mm than it was at the end of August.

Summary for September 2017:
Maximum Temperature 32.2°C
Minimum Temperature 3.8°C
Average Daily High Temperature 24.1°C (Long term average 20.4°C)
Average Daily Low Temperature 10.7°C (Long term average 8.6°C)
Total Precipitation 38.0 mm (Long term average 87.8 mm)

(Long term averages based on 1981-2010 data for the Waterloo Wellington Airport)

August 2017 Summary

An average August for both temperature and precipitation 

Although we didn’t see lots of really hot temperatures this month (only one day above 30°C), we also didn’t see lots of cold ones.  This resulted in the overall temperature being just 0.2 degrees below average, but this is still within the average range.

This may be surprising to some, but the fact is we have seen a string of warm months of August in recent years with this year’s overall temperature being the coolest since 2008.  In the 20 years of data at the UW Weather Station, only one August (2004) was cold enough to be in the below average range.  It was also a lot cooler than last year when we had 8 days over 30°C in August.

The month started out very wet, but with drier conditions in the last week the total precipitation of 93.6 mm was within the average range coming in a bit higher than the average for August of 83.9 mm.

The total precipitation for the year of 775.4 mm is well above the average of 596.0 mm.  For the last few months we have been in second in the “wettest year to date” category, however, there were lots of wet months of August in the past so we have dropped down to the sixth wettest year so far since records in the area began just over 100 years ago.

Summary for August 2017:
Maximum Temperature 30.7°C
Minimum Temperature 6.2°C
Average Daily High Temperature 24.5°C (Long term average 24.8°C)
Average Daily Low Temperature 12.9°C (Long term average 12.9°C)
Total Precipitation 93.6 mm (Long term average 83.9 mm)

(Long term averages based on 1981-2010 data for the Waterloo Wellington Airport)

Thursday, August 24, 2017

Solar eclipse 2017

These are my recollections of my trip down to the US to get on the line of totality during the solar eclipse on August 21, 2017.  As well as just experiencing the eclipse I also took along a temperature sensor to record the effects of the sun being blocked.

Just a bit on the logistics, I stayed in a small town called Glasgow, Kentucky the night before the eclipse and woke up early to drive to Bledsoe Creek State Park in Tennessee which is east of Nashville.  I was worried there might be some traffic, but it was open roads all the way.  I got there about an hour and half before the park opened and was car number 120 in line.  The park was mostly forested, but there was a hydro cut where most people set up their camps as there was a pretty good open view of the sky.

It was nice being somewhere that wasn't wall to wall people, but enough people to have a good group experience.  There were also a few people with very large telescopes, including one guy who had his connected to a computer screen so everyone could see a close up of the sun.

The day was really hot and sunny, with high temperatures of around 35C.  A few clouds appeared in the early afternoon, but just one covered the sun about an hour before totality, after that it was clear.

About 10 or 15 minutes before totality is when it started to get noticeably less bright, note I didn't say darker, but it started to feel not quite so hot and I could take off my sunglasses.  I think this was made all the more noticeable because it was so hot that day.

Once the moon's shadow actually passed over it of course became dark almost instantly, it wasn't pitch black but maybe about as dark as it is 15 minutes after a regular sunset.  Also interesting was the horizon which looked like sunset or sunrise, but instead of just in one part of the horizon it was all around.  Then everything went in reverse once the sun came back out.

Here is a video that I made just by putting a phone on the ground, it starts about a minute before totality and goes till about a minute after.  You can see how quickly it got dark and how the sky changed during the event (note the I'm standing out of the camera's view, I don't know the people who are actually seen in the video):

Something I didn't notice until I watched the videos was just how loud the cicadas got during the eclipse.  If you watch this "time-lapse" I made you can see both the reduction in the light as well as the background noise.  This one starts about 5 minutes before totality and each segment is about 1 minute apart:

Here is the graph of temperature during the eclipse in Tennessee, I kept one of the sensors in the sun (not the usual way to measure temperature I know) and one in the shade.  You can see that the sensor in the sun went down about 7C and the one in the shade got down to about the same temperature but started about a degree lower (the variation in temperature before 14:00 is probably just me setting everything up getting the sensor out of my car, as well the temperature looks like it was still going up when I left the park so I didn't get the entire rising limb of the temperature graph):

And closer to home, at the UW weather station there was understandably a lessor effect on the air temperature:


With the eclipse being 75% or so in the region, there was a large effect on the incoming solar radiation and the wind speed, as shown in the graphs below:

Overall it was a great experience and I recommend trying to get into the path of totality if you can make it.  The only downside was that after getting out of the park there was about 5 hours of bumper to bumper, stop and go traffic to get away from the totality line.  So my biggest advice for the eclipse in 2024 is that wherever you are, stay somewhere close and spend the night so you don't have to deal with the traffic.

Thursday, August 3, 2017

July 2017 Summary

A dry July with average temperature 

A pretty average month for temperature, although it was half a degree warmer than average overall, this is still within the average range.  It was also very consistent as there were only 2 individual days that were more than 5 degrees from the average (you can see in the graph that the measured temperature was within the green band most of the time)

The wet first half of the month couldn’t make up for the very dry last half (only 11 mm after the 17th).  The final total for July was 64.0 mm which is a lot lower than the average of 98.6 mm.

With this dry month, the total precipitation for the year of 681.1 mm is now a bit closer to the average of 509.0 mm.  However, it is still the second wettest year so far (still behind 1947).

Summary for July 2017:
Maximum Temperature 29.9°C
Minimum Temperature 10.8°C
Average Daily High Temperature 25.9°C (Long term average 26.0°C)
Average Daily Low Temperature 15.1°C (Long term average 14.0°C)
Total Precipitation 64.0 mm (Long term average 98.6 mm)

(Long term averages based on 1981-2010 data for the Waterloo Wellington Airport)

Friday, July 21, 2017

June 2017 Summary

A hot June with average precipitation

During June we saw a few hot days (3 over 30°C), some colder ones (3 less than 18°C) and a whole lot of average ones.  However, continuing the trend for the last few years the nighttime lows were much warmer putting the overall temperature just over 1 degree above average.

Although the last week was really wet, it was actually quite dry to start off the month.  So the rain at the end of the month only managed to get the total for the month of 77.8 mm close to but still a bit below the average of 82.4 mm.

Looking at the first half of the year, the total precipitation of 617.8 mm is the second wettest first 6 months of the year, only coming behind 1947 when there was 624.8 mm.

Summary for June 2017:
Maximum Temperature 31.2°C
Minimum Temperature 6.4°C
Average Daily High Temperature 24.1°C (Long term average 23.6°C)
Average Daily Low Temperature 13.1°C (Long term average 11.5°C)
Total Precipitation 77.8 mm (Long term average 82.4 mm)

(Long term averages based on 1981-2010 data for the Waterloo Wellington Airport)