Another Hot Summer Across Southeast Lower Michigan But Was It Hotter Than Last Summer? /Final & Outlook Critique-9/11/11

Like the 5 pound chicken thought as she gave birth to the 6 pound egg...GLAD TO GET RID OF IT! That's been the more common retort (in so many words;-) when chatting with inhabitants of Southeast Lower Michigan about the Summer of 2011. While many do not mind a warm summer, this past summer again made the record books in the top five hottest summer in the Detroit Metropolitan area. The *preliminary summer stats at Detroit will go down as 74.36 degrees /or 74.4/+3.0 rounded/.  
Ironically, that turns out to be the same average attained last summer...74.4!  But again, a bit of that heat record is accounted for by the warm overnight lows related to the metro heat island around Detroit. This is much more obvious when one looks at Flint and Saginaw who... surprise, surprise...actually had a cooler summer than last summer! That's right, while Detroit tied it's average mean for last summer and placed in fourth place for hottest summer two years in a roll, both Flint and Saginaw actually fell shy of last summer's average temperature!  Flint averaged 71.83 / or 71.8/+3.4 rounded/ degrees for this summer, a full half degree /0.5/ cooler than last summer when the temperature averaged 72.3. Saginaw with an average temperature of 71.33 / or 71.3/+2.4 rounded/ this summer, averaged a full 0.7 tenths of a degree cooler than last summer with an average temperature of 72 even. The cooler temperatures at both Flint and Saginaw are especially notable when looking at the hottest summer rankings.  Flint's temperature last summer placed in 7th place for hottest while this summer placed in 12th place. Saginaw's data has even more of a notable difference with last summer placing 7th /like Flint/, however this summer placed way down near the bottom of the list at 16th!  Averaging all three locations together gives a mean temperature this summer of 72.5 degrees across Southeast Lower Michigan. This is nearly a half degree /0.4/ cooler than last summer when the average came to 72.9

The question I proposed at the beginning of the blog is thus answered. Basically, over the entire SE Michigan area, it was NOT a hotter summer that last year when the averages and hottest summer placement are looked at (and in the future that is what will be considered first, where the cities placed on the hot summer's list). When all three cities are averaged together, then NO. However, when considering the hot July and 90 degree days across the area it was a hotter summer than last summer!
Top 20 Coldest/Warmest Summers in Southeast Lower Michigan
RankDetroit Area*Flint Bishop**Saginaw Area***


  16 -     71.3   2011  

*Note: all data is preliminary as official data from NWS is not available as of  9/7/11 

There are a number of reasons why this summer seemed as hot or hotter than last summer. The first reason "boils down" (pun intended) to our miserable July this summer. The second reason is the number of 90 degree or better days this summer . The third, which is more debatable, is the cool and wet spring that proceeded this summer.

1-While last summer's July was also hot,  averaging 75.0 degrees in Southeast Lower Michigan or close to 3.3 degrees above normal, our most recent July was even worse with an average temperature across the land of 77.4 degrees or about 5.7 degrees above normal! Detroit recorded it's hottest July and month on record this summer while Flint recorded it's third hottest July and third hottest month with 76.8 /+6.2/ degrees.  Saginaw recorded its fourth hottest July and fourth hottest month with 76.1 /+4.9/ degrees.  Remember too, this is normally our hottest month anyway across Southeast Lower Michigan.  When you consider that, it's exceptional that we could muster an average temperature for July of nearly six degrees above normal at Detroit.  Standard deviation ranges during the summer months are much narrower (or smaller) than the winter months.

2-The number of 90 degree days this year thus far totals 23 ... as opposed to last years tally of 17 (and our last 90 last year was Sep 21st, 2010).  In that bunch of 90 degree days or plus this summer, it would be remiss of me if I did highlight the ungodly heat and humidity on the 2nd when we just about nicked the century mark with a 99 and then, succumbing to it on the 21st with a 100 degree high (and hottest for the summer) at Detroit! July by fall had the largest amount (it usually does) of 90s. A total of fourteen 90 degree or plus days occurred during the month.

3- There was a marked difference in spring time weather this season as opposed to the spring of 2010.  At the end of the Summer of 2010, we had just completed the hottest six-month stretch (spring-summer) of heat. The Spring of 2010 was indeed warm ranking the warmest in history at Detroit, 5th warmest at Flint and 2nd warmest at Saginaw. So basically, we were already accustomed to warmer weather. On the flip side, this spring was basically lousy with cool and wet weather dominating, from my Spring Review:

As it turned out, the spring temperatures for Southeast Michigan /ave 46.1 just -0.3 below the 46.4 norm/ and well less than a degree below normal being well within the normal range. The number of cool days this past spring were many and many people have commented to me about the “lousy spring”.  However, looking at just the average temperature and departures would counter that claim, truly another case where statistics lie as the dominant pattern was cool! None of the three cities even placed in the top 20 coolest springs (tell that to your friends).

Of course the other big problem about the spring weather was it was very wet. Also from the Spring Review: 

Spring Rains Were Aplenty
No disagreement here it was wet and the stat’s clearly reflect that! Detroit came in second place for wettest spring on record with 14.60” /1947 was the wettest at 16.31”/ Flint handily smashed its record wet spring with 17.00” even, /the previous wettest spring was in 13.80” in 1945/. And, while it was wet further north in Saginaw, the magnitude wasn’t nearly as great as in Flint nor Detroit. Saginaw received 11.88” which placed further down the list in tenth position.

      How does this summer compare to other hot summers in Detroit?


Ave High
J-  80.4
J-  89.3
A-  82.6   

Ave Low
J-  60.7
J-  69.3
A-  63.7



Looking at the charts, one can see that this summer's average temp of 74.4 is a duplicate of last summer and is nearly a duplicate of 1995 and 2005 (2nd/3rd hottest summers at just a tenth higher). So where does the more notable difference show up?  This past summer's high temperature /84.1/  averaged over a 1/2 degree warmer than last year (and no one will debate that one).  Still, it was far "cooler" that our summer of 1988 when the average high temperature of was 86.2! (editor note: to me and I'm sure many others, the Summer of '88 will long be remembered as the hottest summer in recent memory even though it placed 5th (now 6th) in the hottest summer rankings. That summer saw high temperatures push to 90 or better 39 days with five of those, 100's).  No summer  since 1988 has even come close!  It was only because the overnight low temperatures averaged lower with its "desert-like" atmosphere at times). 

The summer of 1995 was the closest to this summer in regards to average highs/lows and number of 90s (there was also a 100 that summer too). The summer of 1955 was a little hotter in average highs (containing 9 more 90s+).  It also had one hot July,  I made note of this in my July write-up.

July 2011 

Detroit July Ave:     79.3 - Hottest July/month on record
Flint July Ave:        76.8 - Third hottest July/month on record
Saginaw July Ave:  76.1 - Fourth hottest July/month on record

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 12.2 Feb-1875 79.0 Jul-1955 10.9 Jan-1977 78.0 Jul-1921 9.4 Jan-1912 77.5 Jul-1921
2 12.8 Jan-1977 79.0 Jul-1921 12.8 Feb-1979 77.7 Jul-1935 10.4 Jan-1918 76.8 Jul-1916
3 13.1 Jan-1912 77.9 Jul-1916 13.1 Jan-1963 76.7 Jul-1934 11.6 Jan-1963 76.2 Jul-1935
4 13.2 Jan-1918 77.7 Jul-1931 13.4 Feb-1978 76.5 Jul-1955 11.7 Feb-1904 76.0 Jul-1931
5 14.8 Feb-1934 77.1 Aug-1995 13.8 Jan-1994 76.1 Jul-1931 12.1 Jan-1994 75.9 Jul-1955

July of 1955 was previously the hottest July (some data actually shows that July averaged 79.1). The difference that summer was August was also hot with an average temperature of 75.7 (2 1/2 degrees hotter than this August). It was June that was cooler in 1955 with 68.5 as opposed to this June's 70.6.

Rainfall across Southeast Michigan was quite variable in both amounts and frequency. Notable dry spells were seen in some locations from late June into late July. July was also a "precipitation extreme month" with very wet and dry conditions existing in unison. Parts of the area saw less than .50" of rain up until very heavy rains from storms hit the entire region very late in the month. Widespread reports of flooding were sent to the NWS on the 27-28th across the region. These heavy rains camouflaged (on July's rainfall map, see July blog) the intense dry spell that engulfed some of the region from late June into late July that led to parched lawns and gardens.  Not so at Detroit Metro Airport (Detroit's official climate site) and nearby downriver communities, they got hammered with most of the storm activity through the month. This led to the second wettest July on record at Detroit with 7.66" (second only to 1878 with 8.76"). Curiously, this is not unlike last summer when much of the severe weather and heavy rains also fell south of I-94.  The driest areas in July (before the late month heavy rains) extended from northern Washtenaw and Wayne counties, north into Brighton, Saginaw and Flint and eastward into the interior of the Thumb Region.

By the end of the summer, the three climate stations saw normal to above normal with the entire region seeing around normal, though time-dispensed very unevenly,  to locally above normal in the heaviest storm areas. 

Summer 2011        /Rainfall/    /Norm/   /Depart/    /Summer 2010/
Detroit                       10.76          9.89       +0.87            11.97 
Flint                           10.84          9.57       +1.27             5.93  
Saginaw                    10.32          8.94       +1.38             9.21 
Note the big difference in Flint's rainfall this summer as opposed to last summers.

Severe Weather
Severe weather episodes across the region were sporadic in nature with two to four events each month about an average to slightly above average season depending on location. Tornado events were below average with three confirmed in the CWA (see below). Damage from the summer storms was overwhelmingly from straight line winds. August contained four notable events of straight line winds (9th,13th,20th,24th) with numerous power outages most notable occurring across Detroit north  suburbs where power remained out locally for up to 5 days. Another stormy area during the entire summer, like last summer, occurred over the southern suburbs of Detroit and the Downriver Communities where heavier rains fell (mentioned above). A confirmed tornado /EF0/ occurred on August 20th near Chesaning in Saginaw County. Another confirmed tornado /EF0/ on July 25th at Sanford  in Midland County. A third tornado /EF1/ occurred in Bay County near Willard
back on May 31st. Individual storm events in the DTX CWA can be found here.

June-Aug rainfall maps (courtesy of the Midwest Climate Center)

Right from the get go,  I stated the summer analogues were too cold and first thing I dismissed in my Outlook.

"I feel the analogue’s temperature departures are too cool and in the end, I expect temperature departures to place within -0.5 to +1.0 of the norm."

Of course, I still was wrong and not warm enough in my original summer outlook even going against the analogues (and even going as much as a degree above, we managed around 3 degrees above)! 
However in my own defense, I upped the temperatures in my mid-summer update issued 7/13.

I have decided to up my temperature departure for the summer to 1 1/2 to  3 degrees above normal. As far as 90 degree days, I originally went 8-12 days for the entire region. I will also boost that to 11-15 for the Detroit and Flint areas but remain with the original projection for the Saginaw Valley region
While the average temperature departures were in the ballpark in the update, the number of 90 degree days, especially at Detroit and Flint which still too conservative. However, I failed to see any summer outlooks that called for a top ten warmest summer in Southeast Michigan with some even calling for a cool summer ;-). I did, however, zero in and discussed the problematic pattern that I felt would develop for the summer. Years of experience did tell me the ridge, already rearing it ugly head in the south late spring, was going to expand and be a major force to reckon with (but exactly where that would be was yet to be told). This is why I decided against the cool analogues. In addition, the Neutral pattern over the Pacific had little or no influence on the jet stream (there were even some La Nina traits still in the global pattern).

From the Outlook:

"projections for the upper wind pattern suggest ridging over the south-central part of the country will periodically expand into the Great Lakes bringing more heat into the region. The temperature outlook is a tough call and will mainly depend on the how strong the ridge becomes and its placement. At this time, it looks like the ridge will oscillate from just to our west (Midwest) to the eastern third of the country. This will bring periods of heat and cool downs" 

The overall pattern expected did indeed develop but the placement of the ridge axis was much stronger and encompassed much of the center and eastern part of the country (this was brought up in the July update). Interestingly, the analogues did intimate there was a likelihood of a high amplitude jet stream in the cards for the summer with the nearly unanimous projection of below normal temperatures.  The big (and important) difference was the placement of the dominant troughs: being over the far northwest and northern Atlantic rather than over the east. 

Their was a strong, amplified jet over southern Canada between the hot ridge over the Texas region and deeper than average upper low over northwest Canada and the Atlantic. In fact,  much of the summer was dominated by a weak negative Arctic Oscillation. At first glance this would be surprising given the hot summer we had, however heights were lower than average in northwest Canada and the north Atlantic which squeezed or amplified the jet and allowed the strong ridge to nose well up into the Arctic. This in turn forced the polar jet far south (see maps) over northwest Canada and the north Atlantic relating to the weak negative AO.