6/21/19

The Summer That Wasn't - Summer of 1992


With our cool June and wet weather in most areas thus far; I'm reminded of a time where the summer weather was actually, all downhill from here. Early June 1992, had been nicer than this June. BTW, that 67.0 degree average for the Summer of '92 in Detroit is about what we've averaged thus far this June. This gives you an idea how the whole summer felt like. Picture it; Spring of '92 (27 years ago)...

Temperatures during the late Spring of 1992 by all accounts were quite normal across Southeast Lower Michigan. May was generally a pleasant but dry month with temperatures averaging near normal. However, a subtle but definite change was beginning to evolve in the weather pattern late in the month.

After a warm spell occurred mid-May with high temperatures climbing into the mid 80s, a strong cold front raced southeast across the region on the 23rd, bringing with it thunderstorms and much colder weather. The high on the 23rd reached 80 degrees in Detroit and 74 at Flint, but on the 24th, the best the mercury could do was a cool 52 in Detroit and only 49 at Flint. Though the 52 at Detroit was not a record low maximum (that chilly honor belongs to a "high" reading of only 44 in 1925), the 49 degree reading at Flint was, and both were more than 20 degrees below the normal.

Both cities did, however, establish record lows the following morning when the temperature skidded down to 35 at Detroit and 30 at Flint. The rest of May remained below normal which brought the monthly averages back to near normal. This turn to sharply colder weather late in the month reflected a temporary shift in the Jet Stream. A strong northwesterly wind blew from the Arctic southward into the Great Lakes region. When looking back, this temporary shift in the upper wind pattern was a foreboding of things to come during the Summer of '92.

Like its predecessor, the first half of the month of June was similar to the first half of May with a rather dry and benign weather pattern. Temperatures averaged slightly above normal with only minor deviations. Ironically, an abrupt change to much colder weather was heralded in around the official start of summer (11:14 pm on June 20th), between the 19th and 21st. In retrospect, this chilly annunciation of summer was uncannily accurate and most fitting for what became the second coldest summer ever recorded in Detroit and the coldest at Flint since records began.

Just before the arrival of the unseasonably cold air mass, temperatures climbed to what would be one of two 90s in Detroit and the only 90 in Flint that year.  An unusually strong and vigorous cold front was pushed across Southeast Lower Michigan by a massive, cool high pressure system in southern Canada. The temperature change between the 17th and 20th was quite impressive over the region. Detroit and Flint both rose into the lower 90s (Detroit-92, Flint-93) on the 17th but on the 20th, the day after frontal passage, readings barely climbed above the 50 degree mark (Detroit-52, Flint-51), a forty degree drop! Both of these readings were record low maximums for the date. Low temperatures the next few mornings were in the upper 30s to mid 40s with Detroit establishing a record low of 42 on the 21st and Flint missing its record low by two degrees with a low of 39 on the 22nd. These are normal low temperatures in Southeast Lower Michigan for late April.

June averaged 2.2 degrees below normal at Detroit with a mean temperature of 65.5, while Flint was 1.7 below normal with a mean temperature of 64.2. Had it not been for the above normal temperatures the first half of the month, the monthly temperature departures would have been greater. Like May, June was again on the dry side across Southeast Lower Michigan with about two-thirds the normal rainfall.

The timing of the lousiest weather during the summer could have not been worse, coming right at the time when the summer is usually at its best, July into August. These months are usually heavy tourist and vacation months in the Great Lakes. The month of July was just about a total wash-out, figuratively and literally. Not only was the month abnormally cool, it was extremely wet, especially across the northern suburbs of Detroit into Flint (where it ended up with the honor of being the wettest July ever with 9.35 inches of rain, a hefty 6.54 above the normal). Across the northern suburbs of Detroit, over 7 inches (7.32) fell in Farmington and nearly 7 inches (6.92) was recorded in West Bloomfield. Officially at Detroit Metropolitan Airport, 5.91 was tallied up during the month which was 2.81 above normal. To add insult to injury, when it did rain, many times it was on or near the weekend. Every weekend showed rain falling either on one or both of the days and sometimes it wasn't just a passing shower. Flint measured nearly three inches of rain (2.72) on Saturday the 18th. Then, later in the month at the start of the weekend on Friday, the 31st, another 2.18 inches was dumped on the area. In Detroit, during the 4th of July weekend, a half an inch of rain fell on Saturday. Then on the following Saturday and Sunday (11th-12th), 1.24 inches accumulated, not to mention the 1.04 that fell on Monday, the 13th. In fact, if your vacation fell during that week of the 11th through the 19th, it rained every day but the last with the rain totaling 3.75 inches. It was even worse in Flint, where rainfall measured a whopping 4.70 inches for that vacation week!

July 1992 ended up the second coldest July on record at Detroit since 1870 with a mean temperature of 68.8 (the coldest occurred in 1891 with 67.2). It was the coldest July ever in Flint back to 1942 with a mean temperature of 66.9 (see Chart-1). Also, while it was the 11th wettest July at Detroit, it made the top of the list at Flint with the 9.35 inches that fell. When combining the cool temperatures and heavy rainfall, all of Southeast Lower Michigan experienced the worst weather in July on record. The other 10 wetter Julys in Detroit were not as cool, nor was the coolest July in 1891 a wet one. Interestingly enough, there were no record lows set in either Detroit or Flint. One explanation would be with all the rainfall, cloud cover averaged above normal (over 7 out of 10 tenths coverage for the month) and thus, this would somewhat hold up the overnight low temperatures. While on the subject of cloud cover, sunshine at Detroit averaged at pitiful 49 percent, down significantly from the 68 percent normally enjoyed in July. As would be expected, there were record low maximum temperatures set, two in both Detroit and Flint (see Chart-1). There were no 90 degree temperature days in Southeast Lower Michigan during July, the month that usually has the most with an average of 5.

It remained unseasonably cool right through August across Southeast Lower Michigan, though it did begin to dry up somewhat with normal to below normal rainfall. An average temperature of 66.7, which was 3.8 below normal, made it the 3rd coldest August on record in Detroit. In Flint, the temperature averaged 65.2 degrees which was 3.3 degrees below normal, making it the second coldest August on record. The temperature did manage to top 90 (91) only for the second and last time in Detroit that summer on August 10th, while Flint flirted with, but just missed its second 90 (89) the same day. Both cities only had six days during the month that averaged above normal reflecting a series of cold fronts that routinely pushed through the area. Two more record low maximums were established in Detroit, while one was set at Flint (see Chart-1) but again, no record lows were managed.

The cooler than normal weather held into early fall with both Detroit and Flint averaging a degree or two below normal in September. Precipitation again rose to above normal levels with Detroit reporting the 7th wettest September on record with 5.55 inches or rain.

While there were a few theories floating around as to the cause of our unusually cool summer, the most accepted and credited was the eruption of Mt. Pinatubo which occurred exactly one year earlier (June 14-15th, 1991) in the Philippines. The volcanic ash that was spewed into the atmosphere, circumnavigated the globe and caused a slight decrease in solar warming into the following year.

The average temperature for the three month (June-August 1992) summer period in Detroit was 67.0 which was 3.1 below the normal of 70.1 degrees. This made the Summer of 1992 the second coldest on record back to 1870. The coldest was just a half degree colder at 66.5 and occurred way back in 1915. The difference between that summer and the Summer of  92 was June of 1915 was cooler (ave: 63.1) than June of 1992, while July was warmer (ave: 70.4) and August again cooler (ave: 66.0). In Flint, the temperature averaged 65.4 degrees which made it the coldest summer on record back to 1942. Normally the summer temperature averages 68.4 through the three month period (see Chart-1).



                                                       C H A R T - 1
                                                       Summer of 1992
___________________________________________________________________
                                                      
T    E   M   P   E   R   A   T   U   R    E    S          ---                       PRECIPITATION                 
Monthly Average/Depart - Record Low Max - Record Low - Rainfall/Depart
                                                Dates                        Dates         
___________________________________________________________________
-MAY        
DETROIT    58.3     + .2        -----                        35/25th           1.33/ -1.44
FLINT        57.3     + .9        49/24th                   30/25th           1.64/ -1.14
--------------------------------------------------------------------------------------
-JUNE
DETROIT   65.5    - 2.2         52/20th                   42/21st           2.35/ -1.08
FLINT       64.2    - 1.7         51/20th                    46/28th          2.26/  - .97
--------------------------------------------------------------------------------------
-JULY
DETROIT   68.8    - 3.1         65/23rd, 65/30th     -----              5.91/ +2.81
FLINT       66.9    - 3.2         64/23rd, 64/30th      -----              9.35/ +6.54
--------------------------------------------------------------------------------------
-AUGUST
DETROIT   66.7    - 3.8         65/14th, 62/28th     -----               2.50/  +.71 
FLINT       65.2    - 3.3           59/28th                    -----               3.50/  +.12
--------------------------------------------------------------------------------------
-SEPTEMBER
DETROIT   61.4    - 1.9          -----                                                  5.55/ +3.30
FLINT       60.2    - 1.0          -----                     * 34/23rd            2.50/ +  .15
--------------------------------------------------------------------------------------
-SUMMER OF  92  (June - August)
DETROIT   67.0    - 3.1
FLINT        65.4    - 3.0
___________________________________________________________________
* superseded in 1995 with 27 degrees


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


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6/3/19

Summer Outlook 2019 for Southeast Lower Michigan - Cool Spring; Cool Summer?

Temperatures:

Overall; I look for temperatures to average around normal or within -1 1/2 to +1 1/2 degrees of the normals for Southeast Lower Michigan. As far as the patterns researched and analogue projections; see my Temperature trends discussion under analogues.

Rainfall:

Look for the general pattern of above normal rainfall to continue into the summer across Southeast Lower Michigan. Analogue summers showed many wet summers with rainfall a couple of inches above normal on average. As far as the pattern researched and analogue projections, see my Rainfall trends discussion under analogues.

Spring Finally Sprung 

The upper air pattern has been very repetitious as of late; basically continuing the general pattern of the winter albeit with obviously; somewhat warmer weather. But not that warm as the Spring of 2019 has gone down in history as a cooler than average spring. May averaged about a degree below normal across Southeast Lower Michigan; April came in-line with normal while March was the biggest offender; averaging close to three degrees below normal! On the whole; Southeast Lower Michigan averaged a degree or two below normal for the entire spring, depending location. Coolest was across the Saginaw Valley and Thumb.


And yes, it's been a wet spring across much of Southeast Lower Michigan with the exception over the Saginaw Valley. The wettest month relative to normal was April.






Hemispheric Discussion 

Above average SST's continue the weak El Nino over the Pacific for our summer with SST's hovering just a titch above normal. Look for the SST's to return closer to normal later this Fall. As of this writing; next winter the ENSO looks to be either a Neutral ENSO or possibly even the beginnings of a La Nina. Note the latest CFv2 is hinting at a collapse of SST's later this summer into the Autumn.



The Analogues for the Summer show some interesting trends:





Temperatures Trends by Month

Let's start with June; a cool or below normal June? That's what all my data is pretty well showing; from analogues, to current and projected upper air patterns, CFS Climate model which looks out over  most of June and CFSv2 model, for all of June. Can't argue much with that; though anything can happen we could be all wrong ;-) Let's hope we can slide by with a "close to normal" June. Also, many times changes occur mid or late month and this June could very well be one of those and warm up with time.

Even though they were just as many cool Junes as warm Junes in the analogues (5/5); the difference here was the cool June departures were more notable than the warm departures for June. The five cool Junes averaged in at 64.7; well below the June norm of 69.4. These cool Junes averaged just under five degrees below normal and were precisely why the average for all of the June sample came in below normal also, at 68.6 /-0.8/. On the flip-side; the warm June's averaged in at 71.9 or 2 1/2 degrees above the June norm or just about half of the cool departure. There was just a couple of normal Junes in the 12 numbered sample

Things started to heat-up in July as well they should with six Julys above normal, averaging better than the degree needed for an above normal month. The normal Julys placed a close second with five in number with only one cool July - a far cry from June's stats. Overall, the July temperature averaged +0.6 above normal but again not enough to declare the month - by average - a categorized above normal month. Still, there were quite a few notably warm Julys with the above normal six averaging 75.8 or better than two /+2.2/ above normal.

By August; a bit closer to a normal temperatures were found but with the above normal Augusts just winning out at five; there were four normal Augusts and three cool Augusts. Average temperatures dropped slightly to 72.3 for all 12 August months.  However; again like the Julys, the warmer, above normal Augusts average at 74.7; nicely above /+2.7/ over the 72.0 norm.

Summers:

What all this data leads to is five cool summers; four warm summers and three normal - or average summers in our sample this go-around. And as one would think: this averages to a strong likelihood of a normal or average summer with ironically the mean temperature at Detroit coming in right at normal with 71.7 degrees on the analogues.

Analogue trends suggest a cooler than average June and a normal to above normal July and August. This then leads to basically a normal summer. A lot will deal with the evolution of the upper air pattern that's been overall; holding to the pattern established way back in the winter. The Pacific jet fighting for dominance - and winning more often than not- over the Polar Jet over central and eastern Canada. This would be expected for two reasons once the normal retraction of the summer-time Polar Jet and two; the Pacific Jet remains somewhat energized due the the warm waters of the Pacific.

Rainfall:

The strongest trend seen in the rainfall side of the analogues is above normal rainfall. Half of the analogues showed above normal rainfall with another three denoting normal or average summer rainfall. That only leaves three drier than average summers in the sample of 12. While the average rainfall for all of the summers comes in at 11 1/2" of rain /11.54"/ and well above the 9.89" normal; this doesn't average just the wet summers. At that pace; the six about normal rainfalls average in at a whopping 13.90" - a very wet signal. Being these are just half of the analogue members; generally that's not strong enough of a signal to use alone. However; besides the six wet summers, there were the three normal which boost it up to nine normal to above normal rains which leaves us with an average rainfall of 12 1/2"  /12.49'/; still comfortably above the 9.89" Even the drier summers weren't all that terribly dry with the three averaging at 8.66". A quite interesting and sort of a weird fluke; all three dry summers totaled at: 8.67, 8.66, 8.66".

While all months averaged above normal for rainfall; basically as the summer went on the chances are it gets warmer and wetter. That's pretty simplistic but in some regards; makes sense. As the warmer air surges northward more often during the summer, I look for more occurrences of severe weather.

Model Projections:

The models temperatures projections are in fairly good agreement for the monthly outlooks with generally a near normal outlook; while the three month season is in good agreement. Looking at the month's individually: June does suggest a lean toward below normal, July; a lean toward above normal and August normal - not unlike the detailed analogues. Therefore; the monthly computer broad-scale projections of the model do  reflect the analogue details.

 




 

 

A consensus of the foreign models suggest a near normal temperature summer also. Interestingly; the large area of below normal temperatures in the mid part of the country is reflected by both the foreign models and American and actually; encroaches the western Great Lakes.



I'll be back during the summer for noteworthy weather events; many on the FB WeatherHistorian chat and have a great summer.

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

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5/22/19

Winter 2018-19: A Disappointment for Snow Buffs But Not Necessarily for Cool Weather Lovers



The onset of winter weather was a struggle in the Winter of 2018-19 across much of extreme Southeast Lower Michigan for cold temperatures, snowfall and storms as a whole.  Many of the impressive snow produces rode across Northern Michigan or occasionally further south in the Ohio Valley with much of Southeast Lower Michigan missing out. Strangely enough; the month of November contained some of the more frequent snowfalls and totals for the season.

December’s weather was exceedingly mild and non-eventful as far as snowfall. Temperatures averaged several degrees above normal – more classic of a stronger El Nino winter rather than the weak Madoki El Nino Winter at hand. Complimenting the unusually mild weather was the lack of snow with generally less than an inch falling across the entire region; far below the normal of 7-10”.  

January entered the scene as December left with overall; relatively mild winter weather holding sway for the first two-thirds of the month. A sharp change in the jet stream later in the month brought true Arctic cold in two aggressive blasts. One cold swoop followed the first winter snowstorm the 19-20th creating generally 4-7” of snow over the south and 1-4” over the north with temperatures plunging below zero the 20th - 21st. After a brief reprieve from the cold, another more serious cold wave surged south from the Arctic near the close of the month on the 28th and persisted right into the opening of February. Temperatures cratered down into the 10 to 20 below zero range on the 30th and 31st and zero to -10 on February 1st

February turned out to be an average month as far as temperatures across all of Southeast Lower Michigan. Snow varied from below average over extreme Southeast Lower Michigan including Detroit and Ann Arbor southward, to above over central and northern areas including  Flint, Saginaw Bay and the Thumb Region.

For the “winter-proper” /Dec-Feb/ period; temperatures averaged-out within the normal range over all of Southeast Lower Michigan. As stated; winter in reality did not really get going until well into January with the cold air arriving with a vengeance later in the month. Snowfall was on and off through the season with December and March the lighter of the snowfall months, February was mixed and November and January; the snowiest relative to normals.

While the winter temperatures averaged normal; the overall cold season /Nov - Mar/ averaged colder than normal and is the main reason the "winter" season felt so long. Here the biggest offender was November with temperature departures 4 1/2 to 5 1/2 below the normal. That; combined with a rather snowy month for November brought in the winter deceivingly early. This was especially noticed since the balance autumn up to then, contained long lasting warmth and a rather late tree-leaf falling and baring. This was notably problematic for homeowners, gardeners and landscapers with snowfalls on leaf piles to be cleared.

The temperature statistics below show the winter months, the winter temperature average and departures. This is for Detroit, Flint and Saginaw with SE Michigan data averaging all three stations together.  In addition; I've included the cold season temperatures/departures spoken about above. Note the entire cold season Nov-Mar averaged a degree below normal for the five month period. Especially significant when you consider December averaged a good four degrees above normal for contrast ( Dec stats also included in the cold season).






WINTER OUTLOOK/ANALOGUE PERFORMANCE

FORECAST

Temperatures - Normal to Below
As with the majority of winters; look for temperatures during the 2018-2019 winter to be quite changeable as opposing air masses via for dominance under a fluctuating jet stream. The ongoing pattern recently experienced this fall is also telegraphed in the Winter Analogues for 2018-19. 

Various computer guidance for the upcoming winter is also having difficulty with what type of El Nino will occur (see model section). While analogues and some models suggest an a typical El Nino pattern, my research also confirms this with colder temperatures than what is typical. I believe during this winter; the Pacific jet will be fighting against a sometimes more impressive colder northern Polar/Arctic Jet coming in from Canada. This winter's analogues are strongly suggesting a normal to below normal temperature winter is at hand with the clear majority pointing in that direction (see Analogues, below).

In the final analysis; I look for Southeast Lower Michigan winter temperatures to average +1.0F  to  -3.5F of normal.

Epilogue: Resultant Winter Temperature Departure /+0.7/  Resultant Cold Season Departure /-1.0/

Results confirmed a normal winter temperature along with  a /+0.7/ numerical figure for all of Southeast Lower Michigan - as the forecast reads. Normal range used +1.0 > -1.0; while below is <1.0 degree. As far as the cold season average; that came in one degree below average (see chart). The two upper air winter patterns expected; materialized. In the analogue monthly discussion; December had the most likely chance to average above normal, as was the case.

The overall pattern was reflected well in the analogue projections for the winter. As a result; the more dominant Pacific jet and especially timing (also see cold season "Epilogue") was also reflected in the pattern.

FORECAST

Precipitation (Rain & Snow water equivalent) - Normal to Below
While jet stream pattern has been busy as of late; as the El Nino sub-tropical jet rev's up into the winter, this is likely to drag the southern, wetter storm track south of the Lakes into the Ohio valley and points south and east - up the Coast. Most analogues and models suggest a drier than average winter. Keep in mind however; many times we have a below normal precipitation amount with normal or even above normal snowfalls. 
 
Epilogue: Resultant 2018-19 Seasonal Snowfall – Normal to Below

Season snowfalls behaved well to forecast of normal to below. The below normal snows fell across the extreme southeast corner of lower Michigan; normal across the remainder of the area using the analogue scale posted. The storm tracks discussed did materialize well north of Southeast Michigan and in the Ohio Valley. While the snowfall season started with a snowy November, snowfall frequency dropped off somewhat in the majority of the snow season.

Heavy winter precipitation fell to the northwest of Southeast Lower Michigan and to the south. The heaviest amounts were concentrated in the Upper Midwest and northern Great Lakes and across the middle Ohio Valley (see precipitation/snow maps below). The wetter above normal precipitation is clearly seen in these areas while the drier, normal to below normal area is reflected across Southeast and South-central Lower Michigan. According to the precipitation maps, the driest or below normal area occurred from the Jackson area east into southern Metro Detroit and points south; or basically south of I-94 (this also reflected snowfall).

From the Analogue Outlook: Actually; all (analogue) months had quite a number of below normal snows with somewhat less above normal - which lead to the slightly below normal winter snows as a whole.  As always, the main thing we are concerned with are the snowfall trends of the winters and to a lesser extent; the snowfall totals. The main trend was for normal but on the lighter side of normal and thus far; we are following the dominant trend seen early with a cold and snowy November.

Earlier analogue year winters - which were the balance of the sample analogues this go around - strongly suggested a normal to below snowfall winter. This clearly did happen in both the snowfalls and precipitation across Southeast Lower Michigan (again; see precipitation and snowfall percent of mean maps below).

(Note - Below Normal snowfall; less than /- 5.0"/ of the winter average snowfallNormal snowfall; +/- 5.0" of the winter average snowfall and above Normal snowfall; better than /+5.0"/ of snow above the average).

SNOWFALL SEASON AMOUNTS/DEPARTURES
SEA TOT

31.3
DETROIT
42.5

-11.2
 Depart


52.4
FLINT
47.4

5.0
 Depart


44.0
SAGINAW
41.5

2.5
 Depart
Snow
Inches

Below
<5.0

Normal
>-5<5.0

Above
>5.0





Temp Maps


Precipitation and Snow Maps






















SNOWFALL MAP ACROSS SOUTHEAST LOWER MICHIGAN SNOW SEASON 2018-19




Well; Summer's just around the corner and will the cool weather persist into the summer? Look for a short discussion on the Spring of '19 and the Summer 2019 Outlook late May-early June time-frame.

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


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