Welcome to October! At Grand Rapids the average 30 year mean for October is 51.5° there is a average of 4.02” of rain and melted snow fall. The average snow fall is 0.3” The record high at Grand Rapids is 89 way back on October 1st 1897 in more recent times it reached 88 on October 8th 2007. The record low of 18 was set on October 30th 1988 and October 21st 1974. The most snow fall was in October 1967 when Grand Rapids had 8.4” of that 8.2” fell on October 27th
From time to time our poster Mookie complains on the fact that since the updated 30 year averages have been posted Grand Rapids has had departures relative to average cooler than other locations in Lower Michigan. Well boys and girls I wrote the NWS office and here is the reply that I received.
Hi James
We believe the issuance of the 1991-2020 normals data plays a role in this since we noticed that these changes are happening more since the latest 30-year normals period was issued by NCEI in 2021. However, other factors may be occurring such as station siting, microclimatology, and differences in the period of record. For example, we moved the Lansing ASOS in 2004 because a cool bias was noticed with the ASOS’s minimum temperatures given the sensor’s proximity to a low elevation area on the airfield. Some of those cooler readings from the mid 1990s-2004 would have been factored into the 1991-2020 normal data, which may partially explain why it doesn’t take as much warmth with respect to Grand Rapids to achieve a larger departure from normal. Over the years, various ASOS locations have had their temperature sensor aspirators replaced or entire temperature systems replaced due to wear and tear. Worn or inoperable aspirators cause warmer readings because air is not circulating properly. We usually notice this pretty quickly and our technicians make repairs. It is not really possible for us to quantify whether factor X or Y played a greater role in explaining why some stations have an easier time reaching greater departures from normal than others.
Recently we performed a regional analysis of departures from normal. This issue you raise is seen on a regional scale as well and is difficult to fully explain. You would think that given similar weather conditions between relatively nearby cities over the course of time, the cities would rank relatively similarly in terms of temperature statistics. This isn’t always the case.
The rankings for the summer (June 1 Sept1) for the mean temperature at Muskegon 9. Lansing 7 Grand Rapids 39 Flint 40 Detroit 20. That means Lansing had its 7th warmest summer while Grand Rapids had its 39th warmest. As for the mean percentile June 1st to September 1st Muskegon 93. Lansing 96 Detroit 87. Grand Rapids 70 and Flint 60. For the year to date (January 1 to September 1) the mean temperature ranking at Muskegon 13. Lansing 15 Detroit 34 Grand Rapids 51 Flint 49. As for the percentile mean Muskegon 89 Lansing 90 Detroit 77 Grand Rapids 60 and Flint 51
Notice how consistently Muskegon and Lansing rank close together, and Grand Rapids / Flint / Detroit rank fairly close together. We have no reason to believe that Grand Rapids is reporting bad data, or that Lansing is reporting bad data. I think the question of why we’re seeing differences in departures from normal is complex and due to multiple factors. It may be better to assess departures from normal across a broader area as opposed to one point, which would be a better representation of the region since the differences in departure would be smoothed out. Areal averages are something that climate scientists would be looking at versus one station’s data.
Hope that helps!
Brandon Hoving, PEM
Observing Program Leader
Meteorologist
National Weather Service
Grand Rapids, MI
It seems as if the NWS is aware of the issue.
Slim
My trip up north was great had a nice time. We went to Alpena yesterday spent some time there then made our way back along 23 that hugs the Lake Huron shoreline down to Standish. I seen you asked yesterday Nathan about the fall colors. They are coming along nicely up in Otsego and Montmorency Counties. The area between Gaylord and Atlanta looked pretty good with the colors. Peak for them I’d say is another week or just a touch over a week away. There wasn’t as much color over closer to Lake Huron that will still be a little… Read more »
Alpena was always sort of off the beaten path. I lived there with my mom and dad for a few years in the early 60’s and my sister got married and stayed there. We lived in Ossinekee about 10 miles south of Alpena. The house we lived in was on old US 23. My sister lived on Nicholson Hill road. Here house was about 3 miles west of the lake but it was about half way up the hill and you could see the lake from her house.
Slim
“There is even potential for a few wet snow
flakes to mix in with pcpn mainly across higher elevations of our
northern fcst area.”
Maybe the first flakes of the season for some next week?
Here is a summery of temperature departures for September. At Grand Rapids the mean was 63.7° that was a departure of +0.2 since that is less than 0.5 that is considered near average. The high for the month was 85 on the 3rd and the low was 38 on the 23rd at Holland the mean was 63.9° that was a departure of +1.0 the high for the month was 85 on the 1st and the low was 39 on the 23rd at Muskegon the mean for the month was 65.3 for a departure of +1.8 the high for the month… Read more »
You listed Lansing twice….is one of them supposed to be Muskegon?
yep I will change that thanks
Slim
I have updated it, Once again thanks
Slim
Also… anyone read the forecast discussion from this morning? Looks like there could be a few snowflakes across the northern counties later next week (!!!)
It seems like the NWS has this handled well, they are former masters students and phd students who are highly skilled in this science. I’m sure they know what they are doing. Thanks Slim and the NWS for getting this info!
Interesting for sure, thanks Slim! Seems to be a combination of things that is kind of hard to nail down. What we’re the September temperature departures?
I have posted a temperature summery for central Lower Michigan
Slim