Yes, that's right! The one degree /-1.1/ below normal at Detroit is purely a function of the warmer 30 year normals for Detroit (as compared to Flint and Saginaw who actually averaged normal to slightly above - see stats below) The warmer normals at Detroit are mainly due to the expansion of Detroit's heat island out into the suburbs including Detroit Metro Arpt. In addition (and more proof of the heat island affect); the 70.6 degree average at the Detroit landed squarely on the 100 year normal for Detroit before the artificial heating /70.6/.
Want more proof that backs up the heat island affect at Detroit; look at the normal temperatures and this summer's averages at both Flint and Saginaw (below) whose sites have negligible heat island affects. Flint actually averaged about a degree /+0.9/ above normal, why Saginaw averaged almost right on normal /+0.2/. In fact at Flint, both June and August averaged close to 2 1/2 degres above normal! Therefore, none of the climate sites in Southeast Lower Michigan landed anywhere near the top 20 coolest for the summer.
Reasons it felt even cooler:
Oh there were cooler statistics; the notable less than normal 90s across the entire region!
Detroit felt only three 90 degree or better temperatures. One each month, with the highest at 94 on 7/22/14. Flint only felt one 90 degree day on 6/17/14 during the summer season while Saginaw also felt a 90, on 6/28/14. These recorded 90s are far below the normal or average across Southeast Lower Michigan where 8-12 are routinely seen in a year (it is still possible yet to catch one or two in September).
Another big reason (if not the biggest) was the notably cooler than normal July. All three stations rallied on below normal statistics there! As far as my opinion, if temperatures are gonna be below normal...JULY is the welcome month!
|Top 20 Coldest/Warmest Julys in Southeast Lower Michigan
|Rank||Detroit Area*||Flint Bishop**||Saginaw Area***|
Still another reason it felt cooler; it's been hotter in recent years and thus, comparatively it "felt" cooler. And finally to a lesser extent if felt cooler; it rained a lot - more than average at all three sites.
My analogues and outlook temperatures and projected averages performed well and right from the get go when I dismissed the projection's of a notably cool summer...
Overall; a comfortable summer is on tap as I look for temperatures to average around normal to slightly below for the summer. That being said I don't anticipate a notably cool summer. I look for temperatures to average between +1.0 degree and -2.0 degrees of the summer norms across Southeast Lower Michigan (see a more thorough discussion under Analogues). Many others are calling for a cooler than normal summer across the Great Lakes; including Southeast Lower Michigan.
Since late fall of 2013, we have had a couple of years which take full marks for past prediction of the past few seasons; 1880-81 and 1981-82. And, maybe not surprising; 1881 contained a normal summer while 1982 had a cool summer (like our two prevalent trends seen). Another year; 1899 joins these analogue ranks as a decent performer during the winter and a good parallel this spring. All three analogues projected a cool spring with the temperature pattern we've seen this spring with time; below normal - normal - above normal. These analogue springs averaged below normal because of a very cold beginning to the season but will a gradual trend change from below to normal to above (Mar; Apr, May). The Summer of 1899 turned out to have a normal summer, therefore we have two normal summers and one below for the recent better performing analogues.
While the summer temperature and averages performed well; the pattern unfolded slower than prevailing analogues...just like the spring. May's above normal warmth held through much of June while June's expected coolness showed up by July. The sign wave pattern returned to normal and above in August. While overall temperatures pattern trends and numbers/averages for the summer are realized, the timing remained somewhat elusive. And as stated before, temperature patterns most of the time don't come neatly wrapped in monthly intervals in the real meteorological world, therefore this signal is least important.
Wet and Wetter!
It was the 19th wettest summer at Detroit with 12.75"; 17th wettest at Flint with 12.04" and Saginaw just missed 20th spot with 10.52 (20th 10.63").
Of course the big news of the summer around metro Detroit was the big flash flooding event on August 11th with 4.57" of rain officially at Detroit. Other totals were higher and lower for a complete write up see here. The rainfall total at Detroit in August was 6.32", which made it the 9th wettest! Had that on day of flooding rains not occurred, August would have been drier than normal with just 1.75" falling the remainder of the month.
That 4.57" of rain in a calendar day was also quite noteworthy! After researching my records from Detroit, I noted that amount was the second highest amount of rain ever to fall on a calendar day in Detroit! "Previous record was back in 1926 with nearly the same... 4.51" on August 17th, 1926. However this is NOT the record of all time for a date...that record also occurred in the 1920s...occurring back on July 31, 1924 with 4.74".
You might remember last summer around metro Detroit was also a wet one; actually wetter than this one with its rainfall total; a whopping 16.13" of rain fell making it the third wettest summer of all time records in Detroit. However; Flint and Saginaw were decidedly drier and not placing in the top 20 wettest list.
I look for rainfall to be quite variable as mixed data presents conflicting results but this is not unlike many summers. Taking all data (past and present) into account; rainfall is expected to be around normal over the southern sections of Southeast Lower Michigan and normal to below across the Saginaw Valley and Thumb Region.Rainfall projections for the summer, are really a mixed bag, as it frequently is in the summer with four normal rainfalls, four below and two above with the average skewed on the drier side. A notable trend from many of the summer analogues are wetter conditions early and/or mid summer with drier weather later summer.
No doubt about it my call for normal rains south and normal to below south was too dry. While lesser rains did fall in the far northern sections of the region, most areas still received above normal rain. This was primarily do to just a day or couple days of torrential rains. In addition; the jet stream remained active across southern Canada and the Mid West as expected see Stormy Weather, below.
All in all it seamed rather normal to maybe somewhat above normal for severe thunderstorm activity/warnings but well below for tornadoes with just two confirmed this summer. Don't quote me on these statistics since they aren't out.
Stormy Weather?As mentioned above; the data to me depicts a notable confrontation zone and I believe we have just recently entered it as of late May. Typically, the busiest times for severe weather in these parts is June into July; with mid June to mid July prime-pickens. I've included the severe weather stats for Southeast Lower Michigan since 1980. Looking above at our analogue summers since then are 1982, 1991, 1997 and 2002 and all but 1982 contained normal to above normal (or busy) severe seasons. That's not surprising given the jet stream that's been dominant in Canada this year. Were this upper jet continued to be aggressive, notable wind events, squall lines and possibly a derecho event or two across the country would be the risk.
This confrontation zone held well (too well) through the summer as the upper low/northwest jet stream remained active all summer and thus, the parade of cold fronts, warm fronts and resulting heavier rains.
Overall when considering both temperatures and precipitation, two analogue years held us in good stead for the summer; 1957 and 1968. Both were wet with temperatures averaging close to this summers (see analogue chart)
Next Up...The Autumn Outlook.
Note; this summer data is preliminary and has not been released by the NWS
as of 900pm Monday, Sep 1st 2014.
Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian