JUNE TEMP STATISTICS
DETROIT June '14 Norms Departures
AVG. MAXIMUM 80.1 79.3 +0.8 AVG. MINIMUM 60.9 59.5 +1.4 MEAN 70.5 69.4 +1.1
AVG. MAXIMUM 80.0 77.9 +2.1 AVG. MINIMUM 58.2 55.2 +3.0 MEAN 69.1 66.5 +2.6
AVG. MAXIMUM 79.4 77.9 +1.5 AVG. MINIMUM 59.9 56.5 +3.4 MEAN 69.7 67.2 +2.5
Along with temperatures being on the higher side of normal thus far, the best performing analogues on average, continue to be relative. Two of the best performing analogue summers averaged around normal and one below normal.
Also from the Outlook;
Best Performing Analogues since Autumn '13
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 June's in the analogues averaged a bit below normal (see below /-.7/) and had the best chance (along with August) of averaging below normal; there was quite a variance of temperatures ranging from 64.2 to 72.4. This is over eight degrees which is fairly impressive for a summer month. Simply put; it was mainly about whether the ridge or trough dominated during the month - or some of both and timing. As stated many times; patterns can't be wrapped up in monthly intervals and one must look at the overall pattern in time. Normal to above normal temperatures began to hold sway in May (as expected in the spring outlook), especially later May which has continued into June but with some notable cool breaks...thus tempering the monthly average. Junes overall temperature performance followed 1963, 1991 and 2002. Now two of these summers averaged above normal and thus...a trend to watch but one month, a trend does not make. However; in the monthly data; July's had the best chance averaging above normal (maybe we're ahead of schedule ;-)). Analogue timing may well be slow and July actually ends up normal or even below since the upper jet in Canada remains strong. In any event, our upper air, precipitation and storm pattern timing has come to fruition thus far.
From the Outlook:
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. Off the top of my head; both 1991 (derecho) and 1997 (squall line and tornado) contained notable July squall lines and tornado and 2002's severe weather season was overall, busy.
As one can easily see, the zone of air mass confrontation between all of these systems is like most summers and extends from the Great Plains, east through the Great Lakes and on to the East Coast.
This upper air pattern has dominated with routinely heat and humidity pushing northeast into the region and cold fronts still routinely surging out of Canada. From the Outlook:
Analogue Upper Wind Data
Past analogue upper wind data paints upper height ridging and oscillations extending from the Rocky Mountains eastward into the Gulf States and points north into the Great Plains to Eastern Great Lakes. In conjunction; an Upper low pressure oscillated over the eastern half of Canada and extended south and oscillated from the western Great Lakes to off the East Coast. This type of pattern would give us overall normal temperatures during the summer with warm to hot spells routinely extinguished by parading Canadian cool air masses. If one or the other prevails more; of course it will be cooler or warmer than expected. Looking at recent past trends along with this analogue data and subsequent pattern suggests to me normal to below normal temperatures.
The upper jet stream across Canada remains amplified along with impressive jet wind maxs at times. This along with frequent moderate to strong instability from the Plains eastward into the Lakes and Ohio Valley/East Coast has ignited storms, severe weather and plentiful rains.
The upper air pattern now affecting the region has brought fresh, cooler Polar air into the Great Lakes once again as the troughs and upper lows settling across eastern Canada remain active. No hot July 4th this year...but beautiful with highs in the 70s.
In the Outlook, I expected best rains to fall over the southern half of Southeast Michigan, closer to the main instability axis during the summer. Here is the rainfall pattern thus far...
And percent of mean (or normal) rainfall....
As one can see it's been wet and stormy from portions of the Plains, Mississippi Valley, Midwest, southern Great Lakes into the northern Ohio Valley. The southern half of Southeast Michigan has seen the highest rainfalls with up to 150% of the norm. Northern areas range from near normal rain to only 50% of normal. Therefore thus far; the best rains have been across the south.
Of course one month is only a third of the way through the summer and there's a lot of weather to be had between now and September. And many more chances to be wrong, or right.
Bill Deedler -SEMI_WeatherHistorian