While severe weather was at bay the majority of the summer; there is
still plenty of other things to mention about the Summer of 2018. Again,
it was warm with hot spells like so many other summers this new millennium.
Feast or famine in the title not only refers to periodicity of the rain
but also the resulting amounts. If this summer felt familiar it should,
the
Summer of 2016 was very similar with it's pattern of heat and erratic rainfall though it was warmer, still.
There is a stark contrast in the summer temperatures again between
Detroit; and both Flint and Saginaw and especially White Lake in the northern suburbs (see Statistics Table, below). Detroit's average temperature of
74.4 made it the 6th warmest summer on record in the warmest summer lists. However; this was more as a result of the heat island frequently affecting overnight low temperatures and somewhat less due to the highs. Detroit
Metro Airport /DTW/ average highs came in at 83.4 degrees while the normal or average
high for the summer is 81.4 degrees therefore; the average high was two degrees above normal. Looking at the average low departure speaks more of
the heat island. The normal average low for the summer is an even 62
degrees. The average low for the Summer of '18 was 65.2 or 3.2 degrees
above normal.
Heat Island Micro-Climate
What's even more significant about Detroit's normals is that the
temperatures at the Detroit Metro Airport have been contaminated
by the sprawling heat island affect since the 1980s. Case in point; the
average summer temperature in Detroit in the 1980s (using 1951-80 norms) was
just 70.0 degrees as compared to 71.7 now; or +1.7 warmer. The norms at Flint /FNT/ rose just 0.4 of a degree from 68.2 to 68.6 in the same time period. I don't have the exact change at Saginaw /MBS/ but I know when we did an in-house study at DTX years back, it showed little change. I worked at the NWS/DTW from the 1970s thru mid 1990s and witnessed the change in the airport's micro - climate and it's gradual temperature rise. My co-worker at the time, Dennis Dixon did an in-house study on the local heat island beginning in the 1980s at DTW. Later, the new runways with the McNamara development in 2002, has likely only added to the problem. New normals for our present period (1991-2020) should be processed in the early 2020's. One guess as to what they'll show with temperature norms?
Summer's, What It's All About...
Chart - 1
Perhaps no place is the heat island at Detroit Metro Airport become more apparent than in the temperature records - take for example the warmest summer records. Detroit's average temperature of 74.4 degrees and placed 6th for warmest summer on record. In comparison, Saginaw just managed to squeak out 16th warmest summer and Flint never even placed! In fact, Flint's average at 70.5 was a full degree /1.1/ below the 20th warmest spot for Flint.
Chart - 2
Looking back at 21 summer temperature averages at the NWS at White Lake /DTX/ shows that this past summer was in at 6th place (a small sample, indeed with just 21 summers). What stands out the most is the fact that all the rest of warm summers beat out this summer's average by a degree or better.
DTX Summer ave temp Year
1- 70.5 2005
2- 70.3 2010
3- 69.5 2011
4- 69.2 2012
5- 68.6 2016
< 6- 66.9 2018
*Updated to add from the NWS Summer Temperature/Rainfall Averages
Feasts or Famine Summer Rains
The isolated to scattered heavier rains that appeared over the
southern areas of Southeast Lower Michigan (including DTW) early in the summer moved north
over the northern half of the region in August. Heavy rains at both
Flint and Saginaw more than made up for what had been a dry summer at
both locations June and July. In contrast; many southern areas including
DTW saw deficits of rain in August. The driest parts of this summer came latter part of June and the first half of July. Rainfall at Detroit Metro while being around normal at that time; did not represent much of the region as evidenced by these rainfall in percent of the mean, maps. The worst of the dry spell came the first part of July; especially across the southern areas of South-central and Southeast Lower Michigan.
1 2
The lack of rain during these periods can really be appreciated by looking at Map 2. Most
areas saw less that less 1/4" of rain in July through mid month and that time period actually could be extended to June 23rd - July 13th. More general rains and thunderstorms appeared later in the summer. The areas in and around both Flint and Saginaw received 7-8"+ of rain in August. Flint measured 7.69" while Saginaw had 8.02". Both stations posted the 4th wettest August since records began. The surplus of rain; mainly due to convective training rains, shows up well over northern parts of Southeast Lower Michigan in this August departure rainfall map.
*Updated to add from the NWS Summer Temperature/Rainfall Averages
Summer Analogue Performance
I already surmised the analogues were too cool and is why I went a numerical value of up to 1.5 degrees above normal for the summer. The average temperature departure across the Southeast Lower Michigan came in at +1.8 (see SE Mich temperature departure in Chart-1) As noted above, what can play havoc with these outlooks can be the heat island at Detroit Metro Arpt.
The best analogue years were 2006 and 2012. Analogue 2006 was a warm and somewhat wet summer like some parts of the region; whereas 2012 was even warmer than 2006 but drier - again like some other parts of the region. Looking further back into the spring; shows 2012 was a warmer spring than this past spring. In fact, Spring of 2012 was the warmest spring on record at all three stations. That year of 2012 recorded 30 annual 90 degree days at Detroit. Thus far this year; Detroit has recorded 25 through Sep 10 2018 and it's still possible to record a few more. So, as you can see both summers, 2006 and 2012 are good candidates for analogues.
Another recent summer, 2016 was not a strong hemispheric analogue as far as ENSO timing but is a good analogue for weather and patterns. That summer the SST's were changing from a El Nino pattern to Neutral; whereas this year's SST's pattern is the reverse; going from a Neutral pattern to El Nino. However; given the SST's were still similar during both summers; the Neutral Summer of 2016 was also another very warm summer and fairly wet across the Upper Midwest and Ohio Valley.
| SUMMER 2018 ANALOGUES |
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| DETROIT | JUN | JUL | AUG | SUM AVE | SUMMERS | 90 DEG DAYS |
| T | E | M | P | S |
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| 1894 | 70.7 | 73.9 | 69.4 | 71.0 | 1 | N/A |
| 1899 | 68.7 | 71.5 | 72.2 | 70.8 | 2 | 6 |
| 1911 | 69.5 | 73.6 | 70.7 | 71.3 | 3 | 14 |
| 1918 | 66.6 | 71.1 | 74.8 | 70.8 | 4 | 15 |
| 1951 | 67.8 | 72.7 | 69.5 | 70.0 | 1 | 7 |
| 1976 | 70.6 | 72.7 | 70.7 | 71.3 | 5 | 21 |
| 1985 | 62.8 | 71.3 | 69.2 | 67.8 | 2 | 3 |
| 2000 | 69.4 | 70.3 | 70.8 | 70.2 | 3 | 1* |
| 2001 | 69.5 | 73.5 | 74.1 | 72.3 | 6 | 14 |
| 2006 | 69.3 | 76.1 | 72.9 | 72.8 | 1 | 10 |
| 2009 | 67.8 | 68.9 | 71.2 | 69.3 | 4 | 4 |
| 2012 | 72.3 | 79.0 | 73.0 | 74.8 | 2 | 30* |
| Ave | 68.8 | 72.9 | 71.5 | 71.1 | AVE | 11 |
| Norm | 69.4 | 73.6 | 72.0 | 71.7 | NORM | 8-12 |
| Dep | -0.6 | -0.7 | -0.5 | -0.6 |
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| DETROIT | JUN | JUL | AUG | SUM TOT | SUMMERS | TSTM DAYS |
| P | C | P | N |
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| 1894 | 2.63 | 2.62 | 0.16 | 5.41 | 1 | NA/NA |
| 1899 | 1.82 | 2.95 | 0.62 | 5.39 | 2 | NA/NA |
| 1911 | 1.48 | 0.79 | 1.31 | 3.58 | 3 | NA/5_9/7_6 |
| 1918 | 3.30 | 0.74 | 1.29 | 5.33 | 4 | NA/5_7/6_8 |
| 1951 | 3.13 | 4.10 | 2.99 | 10.22 | 1 | 29/7_8 |
| 1976 | 3.26 | 1.47 | 1.68 | 6.41 | 5 | 29/4_7/5 |
| 1985 | 1.62 | 3.96 | 4.88 | 10.46 | 2 | 37/7_9 |
| 2000 | 4.90 | 5.40 | 4.63 | 14.93 | 1 | 39/6_7/8 |
| 2001 | 3.40 | 1.16 | 2.87 | 7.43 | 6 | 33/4_5_8/6 |
| 2006 | 3.95 | 4.38 | 2.05 | 10.38 | 3 | 29/7_9 |
| 2009 | 5.27 | 2.56 | 2.76 | 10.59 | 4 | 21/5_5 |
| 2012 | 1.31 | 3.67 | 2.25 | 7.23 | 7 | 34/7_8 |
| Ave | 3.00 | 2.82 | 2.29 | 8.11 |
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| Norm | 3.52 | 3.37 | 3.00 | 9.89 | TSTM | LEGEND |
| p | -0.52 | -0.55 | -0.71 | -1.78 | First # | Annual Total |
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| Color | Temps | Degrees | Rain | Inches |
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| Legend: | Below | 1.0> | Below | 1.00> | NA | Not Avail |
| Normal | 0.0-1.0 | Normal | 0.00-1.00 |
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| Above | 1.0> | Above | 1.00> |
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Autumn Analogues - More of the Same or not?
A weak El Nino is expected to continue to evolve during the fall. Weak El Nino's tend to affect our Autumn weather negligibly, especially if at the forefront of a developing El Nino. A moderate to strong El Nino tends to bring wet, cool falls to the region and luckily it doesn't appear she's is or will advanced that much.
As just discussed above; 2006 and 2012 were our best analogues and while the Summer of 2016 is a good analogue for the Neutral summer; the pattern went off into a La Nina that fall, not El Nino.
Check out the following Autumns of 2006/2012
Temperatures
Precipitation
By the looks of the temperature patterns in 2006/2012; the El Nino's were already affecting the country by Autumn with cooler than average weather extending from the Great Lakes south into the Ohio Valley and Southeast. Precipitation was generally typical for the falls in the Lakes but above in the Ohio Valley.
Autumn 2018
As we progressed into fall a notable cooling engulfed the area - as though Mom Nature read the calendar season change. Extended model guidance basically brings back the more normal to above temperature pattern recently experienced. The best performing analogues for the summer, especially in regard to temperatures; conflicts with the fall warmer models below.
Comparing the analogue data with the computer data results in both temperature and precipitation conflicts
Check out the Outlook for the Fall by model standards...
Temperatures
One doesn't have to be a climate guru or meteorologist to see the various models keep our normal to above normal temperature regime continuing with the American model the most aggressive for warmth.
Rainfall
There is a discrepancy between the models as far as precipitation for the fall also with the American CFSv2 and British model leaning toward a wetter, mild fall; while the European and France model leans more toward normal precipitation, possibly a bit below. Again, the American model is the most aggressive in chances for the wetter scenario. These wetter solutions would intimate that El Nino begins to exude its influence sooner.
Temperatures & Precipitation For the Autumn
Given the conflicting recent and analogue patterns along with model forecast;
I look for an average fall with regard to temperatures with normal to above precipitation.
Look for that all important Winter Outlook in early November!
Upcoming Autumn/Early Winter Dates:
Autumn arrives on Saturday Eve, Sep 22nd at 954PM.
Halloween is on Wednesday, October 31st
Thanksgiving is the earliest possible this year: Thursday, Nov 22nd.
Winter arrives on: Friday, Dec 21st at 522PM EST
Christmas is Tuesday; Dec 25th 2018
Making weather fun while we ALL
learn,
Bill Deedler
- SEMI_WeatherHistorian
