6/6/24

One of the Warmest Winters & Springs Followed by a Warm or Cool Summer?




Southeast Lower Michigan Summer 2024 Outlook

I look for the Summer Temperatures to average normal to above; while rainfall is also expected to be normal to above. I use the two-tier category for all of Southeast Lower Michigan and reasons mentioned below. Another trend clearly observed is rainfall is even more variable during the summer with convective rains - and sometimes it's feast or famine. 

Abbreviated Review of Winter/Spring Temperatures

Spring of 2024 was an extraordinarily warm spring across Southeast Lower Michigan. And really; not unlike the very mild winter of 2023-24 it followed as far as high ranking for above normal temperatures. See both seasons below:

Top 20 Coldest/Warmest Winters in Southeast Lower Michigan
 
Rank Detroit Area* Flint Bishop** Saginaw Area***
Coldest Warmest Coldest Warmest Coldest Warmest
Temp Year Temp Year Temp Year Temp Year Temp Year Temp Year
1 18.8 1903-1904 36.9 1881-1882 16.7 1976-1977 34.0 2023-2024 15.7 1962-1963 33.3 1931-1932
2 19.3 1874-1875 35.7 1931-1932 17.0 1962-1963 33.4 1931-1932 16.5 1917-1918 33.2 2023-2024
3 19.7 1976-1977 35.2 1889-1890 17.8 1958-1959 33.0 2015-2016 16.6 1919-1920 31.7 2015-2016
4 19.7 1917-1918 34.8 2023-2024 18.6 1978-1979 32.2 1982-1983 17.5 1978-1979 30.9 1997-1998
5 20.4 1962-1963 33.8 2001-2002 19.0 2013-2014 31.7 2001-2002 18.0 1977-1978 30.6 2011-2012
Top 20 Coldest/Warmest Springs in Southeast Lower Michigan
 
Rank Detroit Area* Flint Bishop** Saginaw Area***
Coldest Warmest Coldest Warmest Coldest Warmest
Temp Year Temp Year Temp Year Temp Year Temp Year Temp Year
1 41.7 1875 55.2 2012 40.8 1947 53.3 2012 39.8 1950 52.4 2012
2 42.0 1888 53.1 2010 41.1 1984 51.2 1921 40.1 1926 52.1 1977
3 42.4 1940 52.9 1991 41.5 1960 50.7 1991 40.4 1940 50.8 2010
4 42.5 1877 52.7 1977 41.6 1950 50.5 1977 40.6 1947 50.1 1985
5 42.6 1926 52.5 1921 41.7 1996 50.3 1987 40.9 1923 50.1 1921

As you can see the spring season hasn't been updated yet by the NWS DTX above but looking at the facts and figures for the three-month period /Mar-May 2024/ leaves us with an approximate spring temperature average for all three locations.

City   Spring Ave / Ranking

Detroit          53.4 / 2nd warmest Spring

Flint               51.1 / 3rd warmest Spring

Saginaw       50.6 / 4th warmest Spring

Taking this one step further; it's pretty safe to summarize that the 6th month period winter into spring /Dec - May/ was the warmest period all three cities have had since their perspective record periods started.

ENSO STATUS

https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

ENSO Forecast

May 2024 Quick Look

Published: May 20, 2024

A monthly summary of the status of El Niño, La Niña, and the Southern Oscillation, or ENSO, based on the NINO3.4 index (120-170W, 5S-5N)

As of mid-May 2024, waning El Niño conditions persist in the central-eastern equatorial Pacific (between 160E to 160W), with important oceanic and atmospheric indicators aligning with ENSO-neutral conditions. All models in the IRI ENSO prediction plume forecast ENSO-neutral for May-Jul, 2024, which then persists during boreal summer seasons of Jun-Aug, and Jul-Sep, 2024. La Niña becomes the most probable category in Aug-Oct, 2024 through Jan-Mar, 2025.

Summer 2024 Analogues

Over a century of similar Neutral ENSO timings (El Nino Spring>Summer Neutral>Autumn La Nina)






The first most striking feature of the analogues is the dominance of cooler (below-normal) summers earlier in the sample, basically before 1973. After; mainly warmer summers tended to hold sway (normal-above) especially from 1988 on. The other notable trend change has been the wetter summers in the same time period as warmer summers but more scattered with still a few months dry. This warmer trend later in my opinion is due to the expanding city and DTW airport heat island affect (mainly overnight lows) and the more recent, general climate warming. That's not to say a cool summer or dry summer can't happen and they will - but less frequent. 

Several warm season analogues were active with storms and subsequent severe weather. Notably; 1973, 1988, 2007 & 2010. It's also worth noting; generally several of the 1970s severe weather seasons were also active (based on analogue data up to 2010 review data). On the flip side; focusing on the latest analogue, 2016 - severe weather tally was one of lowest.


The above summer analogue later year data and trend of the past six months certainly speaks volumes for a normal to above normal temperature summer in 2024. With that said; another contrary indicator has been the predominant upper low and the intermittent strong flow from the northern Canada and even the Arctic into June. This feature is a semi permanent feature -more or less- through the seasons with generally a fading trend into summer and sometimes, even early fall. This is basically what I would expect this summer and fall, being a increasing La Nina ENSO.

Leaning on the preponderance of data; I look for the Summer Temperatures to average normal to above; while rainfall is also expected to be normal to above. I use the two-tier category for reasons mentioned above and for all of Southeast Lower Michigan. Another trend clearly observed is rainfall is even more variable during the summer with convective rains - and sometimes it's feast or famine.

Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian
 



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