After Several Hot Summers; Finally a More Comfortable Summer in 2013? Do Recent Atmospheric Conditions Foretell Our Summer?

The past three summer's across Southeast Lower Michigan have been bears at times for heat and misery. The Summer of 2012 was not only hot it was rather dry early in the season and thus, it was a tough growing season where water was not readily available. Beneficial rains came too late and too much, especially north of I-69 where heavy rains led to the wettest August on record at Saginaw with 9.3"

                                                         Summer of 2012      

Detroit's Hottest Summer's

Rank	Average Temp.	Year
1	74.8	2012
2	74.8	2005
3	74.5	1995
4	74.5	1955
5/6	74.4	2010/11

So dry was the southern two thirds of Southeast Michigan (especially after a hot and dry July) that the drought index crept up into our back yard. The map below showed the rainfall needed to alleviate the parched conditions by early August, 2012.

As mentioned above, to add  insult to injury the dry landscape in 2012 was parched with blazing sun and heat. Actually, this heat occurred in both July 2011 and July 2012!

Average Temperature Records for July

Detroit Rank Average Temp. Year 1 79.3 2011 2 79.0 1955, 2012, 1921 5 77.9 1916 6 77.7 1931

Flint Rank Average Temp. Year 1 78.0 1921 2 77.7 1935 3 76.8 2011 4 76.7 1934 5 76.5 1955 6 76.1 2012

Tri-Cities Rank Average Temp. Year 1 77.5 1921 2 76.8 1916 3 76.4 2012 4 76.1 2011, 1935

                                                        Summer of 2011 / 2010        

While cooler (not making the top ten hottest summers) at Flint and Saginaw, the Summer of 2011's temperature average equaled that of 2010 at Detroit. Note the temperature placement for all three cities for the Summer of 2011 and 2010. Keep in mind, this chart was done before the Summer of 2012..so it is not included. The Summer of 2010 was an all inclusive hot summer for all three cities under the Hottest Summers list at the time.

Top 20 Coldest/Warmest Summers 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	66.5	1915	74.8	2005	65.4	1992	74.2	1933	64.8	1915	73.0	1933
2	67.0	1992	74.5	1995	66.1	2009	74.0	1934	65.1	1992	73.0	1931
3	67.3	1927	74.5	1955	66.2	1958	72.7	1936	65.5	1982	72.5	1955
4	67.5	1875	74.4	2010/11	66.3	1960	72.6	1939	65.8	1945	72.3	1995
5	67.6	1903	74.2	1988	66.5	1969	72.6	1931	65.9	1950	72.1	1930
6	67.8	1985	74.0	1933	66.6	2004	72.6	1921	65.9	1924	72.1	1921
7	67.9	1912	73.8	1949	66.7	1985	72.3	2010	66.1	1985	72.0	2010
8	67.9	1907	73.7	1921	66.8	1972	72.3	1949	66.4	2009	72.0	1988
9	68.1	1982	73.6	1952	66.8	1967	72.2	1955	66.4	2004	72.0	1937
10	68.2	1972	73.5	1991	66.9	1962	72.0	1935	66.4	1979	71.9	1936
11	68.3	1979	73.5	1959	66.9	1927	71.9	1938	66.5	1977	71.7	1998
12	68.3	1902	73.5	2002	67.0	1982	71.8	1988/11	66.6	1951	71.5	1934

Heaviest rains and storms these two summers /2011-2010/ held over the southern tier of Southeast Lower Michigan...mainly from Ann Arbor to Detroit and south to the Ohio border. This led to the second wettest July on record at Detroit with 7.66" in 2011.  Curiously, this is not unlike the Summer of 2010 when much of the severe weather and heavy rains also fell south of I-94.

So all this is of the past; what about the future...this summer?

ENSO Conditions are Basically Worthless in Helping Project This Summer's Pattern

Below is the Pacific Sea Surface Temperatures /SST/ projected by the Euro Model for the summer. The concentration of the projections lie in the black rounded rectangle; or immediately south of the 0C line.

The latest ENSO projections have "basically" flat-lined into the summer. Flat-lined meaning they are and are expected to continue nearly dead-on neutral /La Nada/ for the summer. It is difficult enough during the winter season to investigate and project a dominant influence solely based on this sort of pattern; but for the summer, forget La Nada. At least during the winter, other patterns such as the NAO, AO, PDO and PNA are better relied on but in the summer, these too are generally weak and more transitory.

So then; what hints of a summer pattern and forecast is Mom Nature suggesting for this summer?

Temperatures

Recent hemispheric patterns and analogue summers (discussion below) suggest to me a more comfortable summer than the past several. In fact, temperatures should average closer to normal or average between 1.0 degrees below normal to 1.5 degree above. While quite variable, temperature patterns for the summer hint the primary (or  likely) temperature pattern for the summer is above normal temperatures early to mid summer with a close secondary (chance) during mid to late summer.

Rainfall

Dominant trends past (previous analogues) and recent (past few months) suggest variability in rainfall trends. April was wet while May was dry relative to normal or average rainfall. While the majority of analogue summers lean toward the dry side; a minority were especially wet! More discussion follows in the analogue section.

We've already seen this wider range variability recently and it looks like it will continue. When speaking of summer's total rainfall; I look for a range of below normal to above normal given the present and past trends. Areas these will occur at this early juncture is very much a crapshoot and only if we go by the recent trends of the spring and subtle analogue trends; heaviest rainfall is intimated to be from the I-96/696 corridor northward through Flint, Port Huron, Saginaw and the Thumb Region. 

Hemispheric Patterns

As the summer ridge builds into the center part of the country, I look for it to oscillate over the Great Lakes and the East, routinely bringing warm to hot weather to the region. However; it should be duly noted that the distinct upper air pattern that has been a key player since mid winter into spring, albeit naturally weakening with time and becoming less frequent, shows no signs of leaving during the summer. I'm speaking of the occasional blocking across the northern latitudes in which I expect to play a distinctive role this summer.  By occasionally phasing with weaker mid continental impulses, troughing will dive into the Great Lakes and points east and thus, intermittently deliver enough cooler spells of weather to balance out somewhat, the heat and humidity we do get for a more normal and comfortable summer than the past several.

The ECHAM model below, in my opinion, has picked up on the expected pattern I see evolving based on our recent and analogue pattern. Here I use its projected two meter /surface temperature/ for the country this summer with my estimated upper wind /500 MB/ pressures and flow.

                                  Projected  Summer 2013 Temperatures /C/ & Suggested Upper Wind Pattern

Summer Analogues

As one can see; the analogue summers below represent variable La Nina conditions that transitioned to Neutral.
 
                                        2013 Summer Neutral Analogues (following variable intensities of La Ninas)

Note: years where the la Nina to neutral pattern occurred for the second time in two year

or so are denoted with a “2” following the year. Normals used 1971-2000 for related years.

Analogue Trends Seen

Temperatures

The Neutral analogue summers are really quite mixed on the temperature front this time which is hardly surprising given the hemispheric and SST environment. Even though Detroit’s summer data favors normal to below normal temperatures, one must closely compare this data to Flint and Saginaw. The reason being, the normals at Detroit were increased in the past few data sets (1971-2000 & also 1981-2010) due to mainly the effect of the local heat island that now encompasses the Detroit Metro Airport; whereas Flint and Saginaw saw little change in their normals. This would logically then, skew Detroit’s departure temperature data down somewhat. In any event; analogues suggest normal temperatures will prevail.

Rainfall and Severe Weather

Rainfall averaged decidedly below normal in the analogue set with about 75% below normal...a strong trend. However; the remaining years were very wet and while a minority of years, it still is an important subset of wet years! This suggests to me that the pattern portrayed in my hemispheric discussion could lead to a stalling of the frontal conflict and storminess and thus, runs the risk of repeating in the same general region. While analogues state drier summers prevailed; we still run the distinct risk of a stormier summer including training echoes if the pattern happens to stall in our neck of the woods. In conjunction with this kind of scenario; there is more likelihood of a wider range of rainfall amounts from below normal to above over Southeast Lower Michigan.

Look for continuing updates and discussions on the summer pattern throughout the summer.

Summer commences on June 21st, 2013 @ 104 AM EDT. Enjoy the Summer!

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