I disagree with our weather forecasters on TV

[MasterB]

Only one thunderstorm warning was issued which was Tue from 10PM to 11PM which the storms weakened and at 11:30PM was when I heard the thunderstorm just about 10 minutes before midnight saw a big flash of lightning and then a loud thunder which I swear something fell but couldn't see what fell thou. The storms that came to Chi they weakened heavy rain and a few rumbles of thunder for a couple of hours 1PM to 3PM and that was about it for Kazoo until 2:30AM when the thunderstorms began again no warnings were issued and the thunderstorm watch expired early was to go through 3AM canceled it at 12:30AM for West Michigan.

I have had a thunderstorm from late Monday/early Tue and late Tue night, Wed afternoon, and late Wed/early Thur. Glad that it will be quiet and no daily thunderstorms I just want the storms to get in and out is all and not days of them, also happy I didn't lose power feel sorry for those that are without power wow 180K at one point without power saw that on ACCUWeather website today.

[jsf]

At one point there were 800,000 DTE people without power, still out around me, luckly I still have power

[jadednihilist]

To jaded or MW, or anyone who might know:
*Customarily, storms of a severe nature seem to lesson in intensity towards the late evening or overnight. I wonder why this hasn’t been the case lately….
*Has this been a relatively rough storm season? It seems like we’ve had some calm summers the last few years. I do remember some stormy summers in the early 1980s.

My apologies for the late reply. I, too, was one of the many without electricity. I had generator power, but lost cable and internet with the Thursday morning storms. Everything's been restored today.

As MW said, what we saw was mostly elevated convection. We can explain convective instability going back to thermodynamics. Density is inversely proportional to temperature at constant pressure, so the warmer the temperature, the less mass per unit volume it occupies. Thus, the relatively weaker the gravitational force is for that particular parcel of air. Cooler parcels are then more dense and heavy than warmer parcels. So, the natural tendency towards an equilibrium is for relatively cool air to sink towards the surface, and warm air to rise up aloft.

Since pressure decreases exponentially with height, we can't make the assumption that pressure is constant with vertical motions, and thus the relationship between density and temperature is a bit more complex. That's why we use lapse rates, or the rate at which temperature decreases with height, to diagnose convective instability. The steeper the lapse rates, the sharper the vertical temperature gradient is, and the more unstable the atmosphere becomes. Since, as a parcel rises, it cools, the relative humidity of the parcel increases and reaches saturation, creating clouds and eventually precipitation.

With surface based instability, the sun heats up the ground, which heats up the adjacent lower layer of the atmosphere much more quickly than the air aloft. Evidence of surface based instability generally manifests in the formation of cumulus clouds (usually at the top of the boundary layer). If the atmosphere above the boundary layer is unstable, the cumulus clouds continue to grow eventually into a precipitation producing cloud, and maybe even cumulonimbus clouds. This is the typical mode of thunderstorm development in the daytime.

At night, the ground cools off pretty quickly, and it cools the surface layer more quickly than the air aloft. Thus, the lowest levels of the atmosphere are pretty stable. This stability can be reduced if we're in a deeply tropical airmass with high dew points because of the higher specific heat capacity of the water vapor-rich air. So, the surface is less stable than it otherwise would be if we were in a drier air mass. The added moisture also makes it easier for a parcel to reach saturation, enhancing cloud and storm processes. However, this alone isn't enough for nocturnal convection. We need the presence of unstable air above the nocturnal stable layer. This is typically done by strong winds bringing in warmer, moister air just above the boundary layer, known as the low-level jet, driven by larger scale meteorological processes. Thus, above the surface, we end up triggering deep convection like we saw overnight Wednesday into Thursday morning.

Typically, elevated convection is not severe. This is because the denser air in the nocturnal stable layer dampens the transfer of winds aloft down to the surface. However, if the surface stability isn't quite strong, the dampening effects are weaker and stronger wind gusts can still mix down to the surface. Another possibility from elevated convection is that the air aloft is so deeply unstable due to steep lapse rates that it aids in the formation of large hail, which often occurs in the great plains.

As a quick aside, another mode of elevated convection is what occurs in the cool sector north of a warm front. Warm winds like to move above a warm front, creating a layer of elevated instability triggering precip, regardless of time of day. That's often why you see widespread precipitation on the north side of the warm fronts around here. The relative dryness south of the front in the warm sector can often be explained by a thermal inversion aloft (warm air above cool air creating stability), or a lack of a trigger to initiate convection.

As to the local climatology, I have limited expertise in that. I defer to MW, Rate This, WOHO who have lived here much longer and know more about how this summer compares to decades past. I will say that this is the most active summer that I've experienced since moving here in 2012 (although I was not here during the summers of 2014 and 2015). I lived here in the 90s as well, but I was a child then and really only 1997 and 1998 stick out to me as active years from my lived experience.

[BKRPDM]

Questions/comments for the group:
1) Why haven’t we had any “Ozone Action Days” lately? I’m surprised….
2) Paul Gross talked for days last week about the cool, pleasant days planned for this weekend; but that obviously changed…thoughts?
3) This long term (seems like all summer) pattern of such high dew points…have we had any summers recently that had similar dew points? How rare is this?

[WOHO]

1988 we had 40 days of 90+, but, didn't have the dew points, in fact no moisture, nothing like the wet windshields every morning for the last 2 weeks. Ozone action days should be a concern if the air masses don't change, and we don't want to have tailpipe test certificates.

[bmw]

Speaking of dehumidifiers, over 2 million were just recalled because they may overheat and burn down your house.

https://www.cpsc.gov/Recalls/2021/two-m ... e-and-burn#

[jadednihilist]

Questions/comments for the group:
1) Why haven’t we had any “Ozone Action Days” lately? I’m surprised….
2) Paul Gross talked for days last week about the cool, pleasant days planned for this weekend; but that obviously changed…thoughts?
3) This long term (seems like all summer) pattern of such high dew points…have we had any summers recently that had similar dew points? How rare is this?

My apologies for the late reply. I've been super busy lately.

For question 1, I don't have a great answer, but I do agree with MW that it may have to do with the amount of rain we've had this summer. I can say that ground ozone tends to form in the presence of volatile organic compounds (such as incomplete combustion of fossil fuels or plant emissions, such as isoprene) and nitrogen oxides (NOx; also a byproduct of burning fossil fuels, agriculture/fertilizers, lightning). A reduction in sources, solid ventilation (winds pushing in "cleaner" air), or deposition (precipitation) can all reduce ozone precursors and limit ground ozone formation.

For the third question, I downloaded DTW daily temperature data going back to 1959. Since daily dew points aren't kept, a solid proxy would be daily minimum temperatures. Since meteorological summer consists of the entire months of June, July, and August, I just took the mean max and min temp of each summer of each year and plotted it:


In this time period, our mean low temperature is 60.9ºF. This year - through Aug 28th - is tied in 3rd place with 1995 at 65.1ºF. The warmest nights also occurred in the summers of 2010 (65.3ºF) and 2005 and 2018 (65.2ºF). So, you are correct that this is a humid summer.

Meanwhile, the mean high temperature in the summer 81.6ºF. So far in 2021, our mean high temp is 83.1ºF, which places us in 10th place for warmest summers in terms of max temperatures.

To see what affect climate change has had on our summer temperatures, I did a quick linear regression of mean max and min temperatures each year. There's no clear trend on max temps in the summer. That doesn't mean temperatures aren't rising; it simply means there's too much noise/variability in the data to discern a trend. However, our minimum temperatures have been increasing at a rate of around 0.11ºF per year (with an R^2 value of 0.56; which suggests that the relationship is real and robust). I would interpret this trend to signify that climate change over the last 62 years has caused an increase in overall moisture content in the atmosphere, so our summers are indeed more humid than they used to be, on average.

If anyone is interested in the raw data, I sorted mean summer max/min temps in order from coolest-to-warmest (it was a pain doing it the other way around):

Summer Mean Maximum Temperatures (Ranked Coolest to Warmest):

Code: Select all

Rank:  1	 Year: 1992 	 Mean Max Temp: 76.3 deg F
Rank:  2	 Year: 1985 	 Mean Max Temp: 77.6 deg F
Rank:  3	 Year: 2004 	 Mean Max Temp: 78.6 deg F
Rank:  4	 Year: 2009 	 Mean Max Temp: 78.6 deg F
Rank:  5	 Year: 1997 	 Mean Max Temp: 78.7 deg F
Rank:  6	 Year: 2000 	 Mean Max Temp: 78.8 deg F
Rank:  7	 Year: 1972 	 Mean Max Temp: 78.8 deg F
Rank:  8	 Year: 1979 	 Mean Max Temp: 79.0 deg F
Rank:  9	 Year: 1982 	 Mean Max Temp: 79.0 deg F
Rank: 10	 Year: 1989 	 Mean Max Temp: 79.6 deg F
Rank: 11	 Year: 1960 	 Mean Max Temp: 79.8 deg F
Rank: 12	 Year: 1967 	 Mean Max Temp: 79.9 deg F
Rank: 13	 Year: 1980 	 Mean Max Temp: 80.0 deg F
Rank: 14	 Year: 2003 	 Mean Max Temp: 80.1 deg F
Rank: 15	 Year: 1965 	 Mean Max Temp: 80.1 deg F
Rank: 16	 Year: 1969 	 Mean Max Temp: 80.1 deg F
Rank: 17	 Year: 2014 	 Mean Max Temp: 80.2 deg F
Rank: 18	 Year: 1990 	 Mean Max Temp: 80.2 deg F
Rank: 19	 Year: 1961 	 Mean Max Temp: 80.3 deg F
Rank: 20	 Year: 1964 	 Mean Max Temp: 80.3 deg F
Rank: 21	 Year: 2015 	 Mean Max Temp: 80.5 deg F
Rank: 22	 Year: 1981 	 Mean Max Temp: 80.5 deg F
Rank: 23	 Year: 2013 	 Mean Max Temp: 80.7 deg F
Rank: 24	 Year: 1986 	 Mean Max Temp: 80.8 deg F
Rank: 25	 Year: 1962 	 Mean Max Temp: 80.8 deg F
Rank: 26	 Year: 1968 	 Mean Max Temp: 81.1 deg F
Rank: 27	 Year: 1996 	 Mean Max Temp: 81.2 deg F
Rank: 28	 Year: 1975 	 Mean Max Temp: 81.3 deg F
Rank: 29	 Year: 1998 	 Mean Max Temp: 81.3 deg F
Rank: 30	 Year: 1970 	 Mean Max Temp: 81.6 deg F
Rank: 31	 Year: 1978 	 Mean Max Temp: 81.7 deg F
Rank: 32	 Year: 1966 	 Mean Max Temp: 81.7 deg F
Rank: 33	 Year: 1999 	 Mean Max Temp: 81.7 deg F
Rank: 34	 Year: 1974 	 Mean Max Temp: 81.8 deg F
Rank: 35	 Year: 1973 	 Mean Max Temp: 82.0 deg F
Rank: 36	 Year: 1963 	 Mean Max Temp: 82.0 deg F
Rank: 37	 Year: 2001 	 Mean Max Temp: 82.0 deg F
Rank: 38	 Year: 1993 	 Mean Max Temp: 82.1 deg F
Rank: 39	 Year: 1994 	 Mean Max Temp: 82.1 deg F
Rank: 40	 Year: 2008 	 Mean Max Temp: 82.1 deg F
Rank: 41	 Year: 2006 	 Mean Max Temp: 82.1 deg F
Rank: 42	 Year: 2007 	 Mean Max Temp: 82.2 deg F
Rank: 43	 Year: 2017 	 Mean Max Temp: 82.3 deg F
Rank: 44	 Year: 2019 	 Mean Max Temp: 82.3 deg F
Rank: 45	 Year: 1977 	 Mean Max Temp: 82.6 deg F
Rank: 46	 Year: 1987 	 Mean Max Temp: 82.8 deg F
Rank: 47	 Year: 1971 	 Mean Max Temp: 82.9 deg F
Rank: 48	 Year: 2021 	 Mean Max Temp: 83.1 deg F
Rank: 49	 Year: 1959 	 Mean Max Temp: 83.2 deg F
Rank: 50	 Year: 1983 	 Mean Max Temp: 83.2 deg F
Rank: 51	 Year: 2010 	 Mean Max Temp: 83.6 deg F
Rank: 52	 Year: 2018 	 Mean Max Temp: 83.6 deg F
Rank: 53	 Year: 2002 	 Mean Max Temp: 83.6 deg F
Rank: 54	 Year: 1984 	 Mean Max Temp: 83.7 deg F
Rank: 55	 Year: 1995 	 Mean Max Temp: 84.0 deg F
Rank: 56	 Year: 2011 	 Mean Max Temp: 84.2 deg F
Rank: 57	 Year: 1976 	 Mean Max Temp: 84.3 deg F
Rank: 58	 Year: 1991 	 Mean Max Temp: 84.3 deg F
Rank: 59	 Year: 2020 	 Mean Max Temp: 84.3 deg F
Rank: 60	 Year: 2005 	 Mean Max Temp: 84.3 deg F
Rank: 61	 Year: 2016 	 Mean Max Temp: 85.2 deg F
Rank: 62	 Year: 2012 	 Mean Max Temp: 85.7 deg F
Rank: 63	 Year: 1988 	 Mean Max Temp: 86.2 deg F

Summer Mean Minimum Temperatures (Ranked Coolest to Warmest):

Code: Select all

Rank:  1	 Year: 1963 	 Mean Min Temp: 55.7 deg F
Rank:  2	 Year: 1965 	 Mean Min Temp: 55.9 deg F
Rank:  3	 Year: 1964 	 Mean Min Temp: 56.0 deg F
Rank:  4	 Year: 1962 	 Mean Min Temp: 56.9 deg F
Rank:  5	 Year: 1982 	 Mean Min Temp: 57.2 deg F
Rank:  6	 Year: 1979 	 Mean Min Temp: 57.5 deg F
Rank:  7	 Year: 1972 	 Mean Min Temp: 57.6 deg F
Rank:  8	 Year: 1971 	 Mean Min Temp: 57.6 deg F
Rank:  9	 Year: 1992 	 Mean Min Temp: 57.6 deg F
Rank: 10	 Year: 1967 	 Mean Min Temp: 57.8 deg F
Rank: 11	 Year: 1978 	 Mean Min Temp: 57.9 deg F
Rank: 12	 Year: 1985 	 Mean Min Temp: 57.9 deg F
Rank: 13	 Year: 1960 	 Mean Min Temp: 58.0 deg F
Rank: 14	 Year: 1976 	 Mean Min Temp: 58.0 deg F
Rank: 15	 Year: 1977 	 Mean Min Temp: 58.7 deg F
Rank: 16	 Year: 1974 	 Mean Min Temp: 58.8 deg F
Rank: 17	 Year: 1966 	 Mean Min Temp: 59.0 deg F
Rank: 18	 Year: 1984 	 Mean Min Temp: 59.1 deg F
Rank: 19	 Year: 1980 	 Mean Min Temp: 59.5 deg F
Rank: 20	 Year: 1961 	 Mean Min Temp: 59.5 deg F
Rank: 21	 Year: 1981 	 Mean Min Temp: 59.7 deg F
Rank: 22	 Year: 2004 	 Mean Min Temp: 59.8 deg F
Rank: 23	 Year: 2009 	 Mean Min Temp: 59.9 deg F
Rank: 24	 Year: 1986 	 Mean Min Temp: 59.9 deg F
Rank: 25	 Year: 1970 	 Mean Min Temp: 60.4 deg F
Rank: 26	 Year: 1969 	 Mean Min Temp: 60.6 deg F
Rank: 27	 Year: 1968 	 Mean Min Temp: 60.7 deg F
Rank: 28	 Year: 1989 	 Mean Min Temp: 60.7 deg F
Rank: 29	 Year: 1983 	 Mean Min Temp: 61.0 deg F
Rank: 30	 Year: 1975 	 Mean Min Temp: 61.1 deg F
Rank: 31	 Year: 1997 	 Mean Min Temp: 61.1 deg F
Rank: 32	 Year: 2014 	 Mean Min Temp: 61.1 deg F
Rank: 33	 Year: 1990 	 Mean Min Temp: 61.1 deg F
Rank: 34	 Year: 2003 	 Mean Min Temp: 61.4 deg F
Rank: 35	 Year: 1959 	 Mean Min Temp: 61.4 deg F
Rank: 36	 Year: 2000 	 Mean Min Temp: 61.5 deg F
Rank: 37	 Year: 1996 	 Mean Min Temp: 61.5 deg F
Rank: 38	 Year: 1973 	 Mean Min Temp: 61.6 deg F
Rank: 39	 Year: 2015 	 Mean Min Temp: 61.8 deg F
Rank: 40	 Year: 2008 	 Mean Min Temp: 61.8 deg F
Rank: 41	 Year: 1994 	 Mean Min Temp: 61.9 deg F
Rank: 42	 Year: 2017 	 Mean Min Temp: 62.1 deg F
Rank: 43	 Year: 1988 	 Mean Min Temp: 62.3 deg F
Rank: 44	 Year: 1998 	 Mean Min Temp: 62.5 deg F
Rank: 45	 Year: 2007 	 Mean Min Temp: 62.6 deg F
Rank: 46	 Year: 2001 	 Mean Min Temp: 62.8 deg F
Rank: 47	 Year: 1991 	 Mean Min Temp: 62.8 deg F
Rank: 48	 Year: 1993 	 Mean Min Temp: 63.0 deg F
Rank: 49	 Year: 2013 	 Mean Min Temp: 63.1 deg F
Rank: 50	 Year: 2019 	 Mean Min Temp: 63.1 deg F
Rank: 51	 Year: 1987 	 Mean Min Temp: 63.2 deg F
Rank: 52	 Year: 2002 	 Mean Min Temp: 63.3 deg F
Rank: 53	 Year: 2006 	 Mean Min Temp: 63.5 deg F
Rank: 54	 Year: 1999 	 Mean Min Temp: 63.5 deg F
Rank: 55	 Year: 2012 	 Mean Min Temp: 63.9 deg F
Rank: 56	 Year: 2020 	 Mean Min Temp: 63.9 deg F
Rank: 57	 Year: 2016 	 Mean Min Temp: 64.6 deg F
Rank: 58	 Year: 2011 	 Mean Min Temp: 64.6 deg F
Rank: 59	 Year: 1995 	 Mean Min Temp: 65.1 deg F
Rank: 60	 Year: 2021 	 Mean Min Temp: 65.1 deg F
Rank: 61	 Year: 2005 	 Mean Min Temp: 65.2 deg F
Rank: 62	 Year: 2018 	 Mean Min Temp: 65.2 deg F
Rank: 63	 Year: 2010 	 Mean Min Temp: 65.3 deg F

Data source: https://www.ncdc.noaa.gov/cdo-web/search (Station: KDTW)

[km1125]

Interesting data. Wish you could plot data from further back, but it looks like the DTW data only goes back to the 40's.

I'm curious because I thought the 60's and 70's were the coolest decades of the century, so I'm not surprised if there was a trend warmer in the later years.

I tried to do a similar thing with the data from NWS Pontiac, but it appears there were chunks of data missing. Seems like all of August daily data from 1923 was gone, as were several years from 1999 to 2011.

This is what I cobbled together. Definitely shows a dip in the 60's and 70's, but relatively flat from through the whole century. Doesn't seem to bump up until this century.

[jadednihilist]

Yeah, data aggregation is a pain for sure... and I also agree with your point regarding the 60s-70s. When I have more time, I can probably gather a longer record of Detroit-area averages, which would be good for detecting trends. I settled with the easiest dataset to work with mostly to answer the humidity question for this summer.

There's also plenty of other datasets (ERA, NARR, NCEP reanalysis, etc) that go back farther in time and are easier to work with, but these are all essentially weather models constrained by observations - so there is going to be some error. However, for long term temperature trends, this shouldn't be an issue. These models just don't handle convective precip very well.

[BKRPDM]

Any comments from the experts on:

*Tuesday’s quick-moving storms? Dew points were very pleasant up until the late morning, and it was seasonably cool.
*Paul Gross called for these storms quite accurately by Sunday morning.
*The wacky High Wind Warning that was in effect for about 90 minutes last night. Thankfully those winds didn’t materialize, but what was out there that caused them to post; and a HWW, not just a Wind Advisory?

[jsf]

I saw on channel 7 last night about 9:30 that a tornado was on the ground near Flat Rock, about 2 minutes later the warning was dropped. Not a word about it this morning so I don't know where it was or if any damage.I heard the emergency alert was sent off and phones were buzzing all over Downriver, still no word.

[WOHO]

Yes, emergency notifications went off on cellphones Downriver: Flat Rock, Trenton, Woodhaven... so was it just a radar TVS possible rotation, or did anyone see a funnel near Flat Rock?

[km1125]

I saw on channel 7 last night about 9:30 that a tornado was on the ground near Flat Rock, about 2 minutes later the warning was dropped. Not a word about it this morning so I don't know where it was or if any damage.I heard the emergency alert was sent off and phones were buzzing all over Downriver, still no word.

I don't recall them saying it was actually on the ground. They were saying "radar-indicated possible tornado" or something like that. 2, 4 and 7 were focused on the same area that was just west of I-75 near Carleton and Exeter and would have generally been heading towards Flat Rock. The warning was until 9:45, but the cell broke up a bit early and they cancelled the warning (IIRC) around 9:30.