3/2/14

Spring 2014 Outlook For Southeast Lower Michigan

After one very cold and snowy winter that really has yet to complete its run; it might sound a bit premature to talk about spring. However, officially by meteorological calendar standards /Mar - May/ we have now entered spring. And yes, as you pretty well expect, the next several days in the first week of March are going to feel like the last several with no really discernible difference. But what does the spring season on the whole look like as far as temperatures and precipitation when researching past analogue seasons that portrayed our cold winter the best. And, what about model projections for the spring season, do they agree or disagree with the analogues?

Temperatures:

Look for temperatures to average below normal to normal with three month departure below the normal spring temperature. See reasoning below...

Precipitation:
Look for precipitation to average normal to below with the three month departure below the normal spring precipitation. See reasoning below...


ENSO

Little overall change is expected on the larger hemispheric scale as far as ENSO this spring as neutral conditions continue in the Pacific. As one can see by computer Pacific SST projections; little if any influence is expected from that region for the world.




Spring 2014 Analogues

The spring analogues were chosen as a subset of the winter analogues that performed the best in relation to temperature and lesser extent, snowfall. The original raw set of Winter 2013-14 analogue winters projected a colder than average winter with variable amounts of snowfall possible. From there, I narrowed it down by mid January to the coldest of winters with near normal to above in snowfall. these six winters were used in our spring outlook. The normals, averages for the six winters and departures are displayed on the bottom of the chart. The best performing analogues, 1981-82 and 1880-81 are displayed on the top of the chart. Remember; these analogues reflect what happened locally in Southeast Lower Michigan (using metro Detroit's data for the spring) in the past under similar hemispheric conditions. It's mainly their general temperatures/precipitation and trend that is most important and to a lesser extent, their numerical departures.




Immediately one can note these springs were not the nicest as far as temperatures (see color legend).  Four out of the six springs went on to be colder or below normal as far as temperatures. The other two, averaged in the normal camp with no above normal springs seen (far right column, under spring average). The real drain on the spring temperatures were the colder than normal Marches and Aprils. Early in the spring anyway, showed the best chance of averaging below normal with three Marches below normal and three near normal. Narrowing this down further, when using our two best analogues for the winter, Winter of 1981-82 and Winter of 1880-81 both following Marches were colder or below normal. Moving on to April, three Aprils averaged below normal and two ranked near normal and one in fact, averaged above normal /4/1899 - 50.5/ +1.2/. However, when averaging the six Aprils in the analogue set, the average came in at 2.6 below the normal of 49.3 degree and almost identical to the March departure of 2.5 below it's normal of 37.2. In addition, again using our two best winter analogues, 1981-82 and 1880-81, both Aprils averaged decidedly below normal. Ironically; both March and April of 1982 and 1881 averaged similar temperatures with above average snowfall in Detroit. It will be interesting to see if this plays out a third time or the present cold and snowy pattern is cut off quicker than in those two analogue years. The most striking change that was seen in the analogues was the warmer or above normal Mays. Out of the six Mays, three averaged above normal, two averaged near normal and just one below normal. Was the polar cold was finally exhausted and the dominant upper wind pattern modified and changed? It appears that way. This is at least, encouraging for warmer than normal times ahead in mid to late spring, anyway.

Therefore; while the majority of springs started out with below normal temperatures, a subtle trend back to normal and even above normal could be summarized as the springs unfolded. This would seem to have logical support when one considers the gradual melting of the snow along with the extensive ice cover on the Great Lakes. This surface moderation along with a gradual relaxation of the predominant northwest upper jet stream looks subtle to the analogue results. Or, in other words, the previous cold analogue winter guidance and resultant extensive ice cover of the Great Lakes and bountiful snow cover (as seen in our two best analogues); encouraged a longer lag of below normal temperatures in the spring season than usually seen.

Spring Precipitation

Overall, spring precipitation averaged around normal to below in the analogue years. On average, normal to above normal precipitation early in the season gave way to normal to below normal later in the season. Five out of the six springs contained a notable dry period with the best chance being in April or May.  Early in the season was feast or famine for snowfall with half of the sample containing above normal snowfall and half below; the aforementioned analogue years 1982, 1881 along with 1899 contained well above. It should be noted freezing precipitation also was noted these years.

Severe Weather Seasons (into the summer)

Looking over the severe weather stats for the analogue years since 1980 (locally) and 1961 (tornado stats map from SPC), The analogue years averaged normal to below normal for severe weather. Perhaps this is not surprising since many of the  analogues averaged colder than normal and when it did warm up, precipitation amounts dropped off comparable to normal. Of course; there were a few busier years but more occurred in the summer, which is typical anyway.

Severe Weather Stats for Analogues from 1980 to 2006; note the average amount on the bottom was 45 days.

Annual Totals
Year
Hail
Wind
Tornado
Total
Rpt
Days
Rpt
Days
Rpt
Days
Rpt
Days
1980
58
17
186
32
29
16
116
37
1981
13
7
54
21
5
3
23
22
1982
45
15
117
19
17
9
79
28
1983
86
15
283
30
22
12
130
34
1984
31
12
79
29
20
12
71
39
1985
103
16
158
22
13
9
129
31
1986
72
21
165
36
34
19
140
46
1987
30
16
196
31
16
13
62
38
1988
75
22
198
35
19
10
113
40
1989
32
17
128
30
19
13
70
38
1990
33
16
141
21
23
12
79
27
1991
78
24
320
39
29
10
136
46
1992
66
24
262
32
52
16
170
42
1993
61
22
168
29
8
7
77
37
1994
159
30
239
37
12
8
183
48
1995
76
27
272
41
8
5
92
48
1996
120
35
244
41
14
8
148
56
1997
118
30
330
39
21
5
160
45
1998
270
36
595
39
28
16
326
52
1999
165
28
385
40
15
9
195
45
2000
292
30
381
46
16
9
324
53
2001
198
39
356
53
41
11
280
66
2002
145
39
394
53
22
6
189
62
2003
359
42
559
47
17
12
393
55
2004
326
45
489
45
22
10
370
60
2005
164
32
523
38
3
3
170
48
2006
424
50
404
49
12
9
448
70
AVG
133
26
282
36
20
10
436
45
 
                                                                                                                                                                                                                                                                                                                                                                                                                    Tornado occurrences/ranks in all analogue years since 1961


 
 


Computer Model Temperature Outlook for Spring in Southeast Lower Michigan

Looking at the computer model /CFSv2/ temperature outlooks for first the entire spring season and then, by monthly projections shows very strong support for the analogues. As one can see, below normal temperatures (blue shading) are suggested for the entire Great Lakes region for the spring as a whole. Interesting how this latest computer projection nearly duplicates local findings, right down to the month.


Monthly Breakdown of Temperatures




During the next few months; I'll have more posts on the Historic Winter of 2013-14.

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