...The Winter of 1997-98...Sometimes Calm, Sometimes Wild,
   But Through It All, Unseasonably Mild...
By: William R. Deedler, Weather Historian, WFO Pontiac/Detroit Mi

With effects of El Nino helping to keep the Arctic air at bay,
the winter of 1997-98 will definitely be remembered across
Southeast Lower Michigan as unseasonably mild and wet, especially
January into February. December differed somewhat from January
and February, yet it too was milder than normal, but not by
nearly as much and it also was a bit drier than normal. Even 
with being milder and drier, a picturesque snowstorm hit the 
area from Flint south through metro Detroit on December 10th,
leaving 2 to 7 inches of snow with the heaviest falling in
Detroit's west and northern suburbs. It turned out that this
storm produced the heaviest snow that metro Detroit would see
during the winter months of December through February. The snow
was lost by the Christmas Season, when it would have been most
appreciated, only to be replaced by heavy rain and sleet
Christmas Eve and nothing but scattered snow showers Christmas
Day.

During January, the abnormally mild winter weather got into 
full swing. Temperatures averaged 8 to 10 degrees above normal
across Southeast Lower Michigan. It turned out to be the seventh
warmest January on record in Detroit (back to 1870) and the
fourth warmest in Flint (back to 1943). The warmest of the
weather arrived during the first week of the New Year. Even 
with the mild weather, snowfall only averaged 2-4 inches below
normal with generally 8-12 inches falling and nearly all of that
fell during the second half of the month. 

A fairly active storm track during the month brought above
normal rainfall to all of the region. Precipitation averaged
one to two inches above normal and this trend continued right
into February, with the notable exception of the first week.
During this week, exceptionally nice, early spring-like weather
was experienced by all in Southeast Lower Michigan, including
several spring loving birds and animals who, like the rest of
us probably wondered, "What happened to winter"? Temperatures
averaged a good 10 degrees above normal with little, if any
rainfall. Readings frequently pushed into the 50s during the
afternoon, flirting with, but never quite breaking, the existing
record highs. While it did cool down somewhat by mid-month, 
temperatures never went below normal. In fact, every single day
in February at both Detroit and Flint averaged above normal, a
rare climatic statistic, indeed! In the end, February's temp-
eratures averaged about 11 degrees above normal across Southeast
Lower Michigan. It became the second warmest February on record
in Detroit (including the warmest this century) and the warmest
on record in Flint. 




As February unfolded, the temporary reprieve from storm
systems and rainfall during the first 10 days ended. Both
Detroit and Flint again had more than the usual amount of 
rain in February (which is normally one of the drier months).
Rainfall was especially plentiful in metro Detroit, where
rainfall amounts averaged about two inches above normal. 
Besides the unusually mild temperatures experienced during
February, another just as outstanding weather feature was the
almost non-existence of snow. Only a trace of snow fell in
Detroit during February and .4 in Flint. This was the first 
time that only a trace of snow was recorded at Detroit during
any February since 1880.

In fact, only one other winter month (Dec-Feb), recorded less
snow and that was in December 1889 when no snow fell. At Flint,
the .4 of snow that fell was the least ever recorded during
February (or any other winter month, for that matter), since
1950.

Another incredible temperature fact that had never occurred
before in Detroit since 1870, was the absence of single digits.
Through March 20th, 1998, no single digits had been recorded 
at Detroit Metro Airport during the winter season of 1997-98. 
The lowest temperatures recorded were two 11 degree readings, 
one on December 31st and the other on January 14th.

The temperature statistics of the winter of 1997-98 in 
Southeast Lower Michigan are as follows...

                      TEMPERATURES        
-------------------------------------------------------------
           December    January    February    Winter   Normal
-------------------------------------------------------------
Detroit     32.3        32.8        36.7       33.9     25.5 
(Depart)   (+4.0)      (+9.9)     (+11.3)     (+8.4)

Flint       29.9        29.9        34.6       31.5     24.1
(Depart)   (+2.7)      (+8.4)     (+11.1)     (+7.4)
 
_____________________________________________________________

The Detroit area averaged about 8 1/2 degrees above normal or 
what is typical during a winter. The average temperature of 
33.9 put the winter of 1997-98 into fourth place for warmest
winters on record since 1870. One has to look back to the dust
bowl days of the 1930's, to the winter of 1931-32, to find a
warmer winter. That winter placed second for warmest with an
average temperature of 35.6. The other two mild winters (first
and third place), occurred in the 1800's. Third place belongs
to the winter of 1889-90 with an average 35.0. Finally, the
warmest recorded winter in Detroit's weather history occurred 
way back in 1881-82 with a very mild average temperature of 
37.0 degrees. This mild winter average was helped immensely by
an unusually warm February, which averaged 39.5 degrees.

And what winter, did this winter replace as the fourth warmest
winter?  Why, it was none other than the El Nino winter of 1982-83, 
our last "strong" El Nino winter. What could be more fitting
and logical, since this year's El Ninos strength was expected to
be at least equal, if not exceed that of 1982-83.

At Flint, the average temperature of 31.5 degrees also did not
place this past winter in first place for warmest. After a
scan of the climate records, the honor of first place stayed 
with the El Nino winter of 1982-83. During that winter, Flint
averaged 32.2 degrees or .7 warmer than this past winter. One
hypothesis as to why Flint was unable to beat the winter average
of 1982-83 and Detroit did, would be because of the expansive
heat island effect of metro Detroit. Since the winter of 1982-83 
(and especially in the western suburbs, where Detroit Metro
Airport is located), an expansion of commercial and housing
development has taken place. Occasionally, even Metro Airport's
(as compared to Detroit City Airport, where records were taken
before 1959) overnight low temperatures are artificially inflated
due to the urban sprawl thats happening around it. This is 
especially true when a southeast to norheast, to north wind
blows. Then again, when checking nearby Toledo Ohio's winter
average temperature, it was found they too, like Detroit, had
exceeded their winter average of 1982-83. 

One of the classic effects of El Nino is the development of an
unusually strong southern stream (southern U.S.) storm track
during the winter months. This prediction certainly rang true
across that region with frequent low pressure systems dumping
heavy amounts of precipitation along with some notable severe
weather outbreaks in the deep south. When the storm track pivoted
northward into the Great Lakes states, Southeast Lower Michigan
was frequently either in the storm track or near it. This was
especially true for metro Detroit, January into February, which
caused the above normal precipitation.

                      PRECIPITATION
_____________________________________________________________
-------------------------------------------------------------
          December    January    February    Winter    Normal
-------------------------------------------------------------
Detroit     1.89        2.78        3.60       8.27      6.32
(Depart)   (-.93)     (+1.02)     (+1.86)    (+1.95)

Snow/Dpt  6.1/-4.8    8.3/-3.5     T/-9.2      N/A       41.7    
_____________________________________________________________
Flint       1.06        3.16        1.65       5.87      4.78 
(Depart)  (-1.05)     (+1.77)      (+.37)    (+1.09)   

Snow/Dpt  6.9/-4.4    8.0/-4.3    .4/-9.9       N/A       48.9    
_____________________________________________________________   
-------------------------------------------------------------


Though the season snowfall total is yet to be determined, it
is fairly safe to say that snowfall across the region will 
come in below normal. That is, unless we get a big clobbering 
this spring. I has happened, as evidenced by the 24.5 inches
of snow that fell on April 6th, 1886, the most ever in a
single day in Detroit!

While this past winter's weather pattern started out resembling
that of 1972-73 in December, January into February
were more similar to the December/January 1983 pattern. 
Temperatures averaged well above normal during both winter
periods with very little snowfall. During this past winter, 
the El Nino effect seemed to grow as the winter evolved, 
reaching its maximum in February whereas in 1982-83, the 
effect was strongest earlier in the winter. 


Looking at this spring, let's reflect back to the springs that
followed the strong El Nino winters of 1972-73 and 1982-83.
Similarities are spotted in both springs. First off, both 
springs averaged wetter than normal including above normal
snowfall (both through April and in 1973, into May)! In 
addition, temperatures generally started the spring at/or
above normal but eventually went below normal by late spring.
Both Mays (1973/83) averaged below normal in temperatures and
above normal in rainfall. Checking all El Nino years back to 
1950 (total of 11) showed much more variability in spring-time
temperature and precipitation than the strongest El Nino
years. The cooler/wetter trend of the post strong El Nino
springs obviously contains far fewer years and subsequent 
data; therefore, its reliability is certainly questionable.

Severe weather frequency after El Nino winters since 1950
(total of 11) was even more variable. Just looking at 
confirmed tornado statistics in Southeast Lower Michigan 
showed the following...

1952 - 0         1970 - 0          1987 - 8 
1959 - 2 *       1973 -22 *        1988 -12  
1964 - 4         1977 -10          1992 - 2 
1966 - 2         1983 - 9 *

The above years average to 6.5 tornadoes per year, while the 
average number of tornadoes annually during the past 50 years
comes to 6.6, virtually no difference. Narrowing this data 
down to the three strong El Ninos(*), 1958-59, 1972-73 and 
1982-83 just reflects the broad spectrum of results. There 
were only 2 tornadoes confirmed during the severe weather 
season of 1958; on the other hand, there were 22 confirmed in
1973 (the most ever) and nine were confirmed in 1983. Another
variable that must be considered here, though, is the better
tracking and reporting procedures that have evolved since the
1950s/60s, when generally fewer tornadoes were reported.

I wish to thank my fellow employee Rich Pollman for his 
research into Southeast Lower Michigan's tornado statistics
in El Nino years. 

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