Reflections Back on the Summer of 2015

Cant believe summer's already hit the road? However; with last week's cool temperatures and this weeks hot - think again. As far as meteorological fall it begins on Sep 1st, though the calendar may differ about three weeks. It's nice to review this past summer to see how we stacked up against a typical summer in Southeast Lower Michigan along with how my Summer Outlook and analogues fared.

Summer Review

Temperatures across the area actually averaged very close normal for the summer with readings swinging above normal to below and back again. The summer might have "felt" somewhat cooler than normal because we lacked any really hot weather spells during the period. In June through August time-frame; we felt only a few more than half our normal 90 degree days at both Detroit and Flint with just six /average is 8-12/. Of course, this is changing this first week of September where already some more 90s have been recorded. Inhabitants around the Saginaw region really got short-changed if you like hot weather with just two days where the thermometer hit or exceeded  90 degrees, the entire three month period. There were plenty of 80s (several upper 80s) however, which made up for the lack of really hot weather. While there were muggy days and nights, they came in just occasional periods which also made the summer more tolerable.

Generally; the summer started on the wet side with a gradual lessening to the rainfall periods and drier conditions mid summer; only to be replaced with normal to above rains again late summer.  Therefore; all regions saw adequate rainfall with normal to above normal totals in the summer. While severe weather popped up during the season, thus far it's been below average with only a few notable events.

Let's check out the analogues for Detroit that I chose for the summer; against the actual readings and averages.

Detroit's summer analogues performed exceedingly well and actually accounted for the very slight below normal departure mainly due to the inflated heat island norms. The average temperature of 71.1 degrees fell right on the average temperature projected by analogues /71.1/, not an easy feat to do. Rainfall totals also came remarkably close to the average projected /9.92"/ with 10.24" actually falling, or just a third of an inch /.32"/ higher.

Analogues for Flint and Saginaw were not figured for the summer but temperatures for the entire region were discussed and forecasted. From the Summer Outlook;

Temperatures :

Overall; I look for temperatures to average around normal but with notable swings as the upper low and troughing in eastern Canada via for dominance against upper ridging, aided and at times, even suppressed by El Nino affected winds across the south. This is a difficult forecast as we dealing with two distinctive upper wind patterns, not always present in such fashion in the summer. The outcome is not only going to be affected by conflicting air masses but also with the timing and the extent of dominance by each air mass. 

Also, the chances of long hot spells are less than average and subsequently; average to below average /8-12/ so too are the amount of 90 degree days.  Overall, while a typical /six normal/ summer dominated as far as temperatures.

That being said; In the end, I look for  temperatures averaging between +1.5 degrees and -1.5 degrees of the summer norms across Southeast Lower Michigan...a bit wider range than typical.

Rainfall:

I look for rainfall to be quite variable as mixed data presents conflicting results and where and how much may also be exasperated more than what is typical for many summers. Taking all data (past and present) into account; rainfall is expected to be above normal over the southern sections of Southeast Lower Michigan and normal to possible even below across the Saginaw Valley and Thumb Region. As with temperatures, timing of the wettest and driest periods will be quite variable - not unlike the spring.

 

Resulting temperatures for all of Southeast Lower Michigan averaged a 1/2 degree /+0.5/ above normal when both Flint and Saginaw were factored in to Detroit's data. Not surprising Flint and Saginaw data averaged above normal given the cooler norms when compared to Detroit. Still, this was well within the projected temperature forecast  (-1 1/2 to +1 1/2) and actually fulfilled the above normal range average projected at both Flint and Saginaw.

Rainfall, on the other hand was higher across the Saginaw Valley than what was expected with Saginaw receiving nearly a foot /11.96"/ and just over three inches /3.09"/ above normal! This was primary due to a wet August as convective boundaries fired off and stalled a bit further north as the summer advanced. In fact; just four days accounted for nearly five inches of the August's total at Saginaw! Thunderstorms containing heavy rain fell on the 2nd /1.55"/, 10th /1.11"/, 14th /1.31"/ and 23rd /0.99"/ which made up 4.96" of the 5.50" that fell /or 90%/. All locations had normal to above normal rainfall which was projected, save the Saginaw Valley.


See the temperature and precipitation table below for the entire region:

All data is preliminary
________________________________________________________________________________

Next up; what will this El Nino Autumn bring to Southeast Lower Michigan.

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