Traverse City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Traverse City clear sky chart from 2005-11-05 to 2017-08-12.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
33%
15900
11%
46652
8%
15856
36%
15856
16%
35018

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
14%
900
3%
2506
1%
895
15%
895
5%
2266
January16th to endNight
15%
960
4%
2688
2%
960
16%
960
6%
2389
February1st to 15thNight
18%
760
5%
2282
3%
758
20%
758
8%
1947
February16th to endNight
22%
631
8%
1893
4%
631
26%
631
9%
1569
March1st to 15thNight
31%
720
14%
2141
9%
720
35%
720
18%
1563
March16th to endNight
36%
720
17%
2064
13%
720
40%
720
22%
1451
April1st to 15thNight
30%
539
14%
1797
9%
539
37%
539
17%
1250
April16th to endNight
38%
540
19%
1623
12%
540
45%
540
25%
1088
May1st to 15thNight
39%
540
14%
1620
10%
540
44%
540
21%
1131
May16th to endNight
46%
562
15%
1498
8%
561
53%
561
31%
967
June1st to 15thNight
45%
505
12%
1405
8%
505
49%
505
27%
936
June16th to endNight
57%
516
13%
1416
8%
516
59%
516
31%
901
July1st to 15thNight
65%
510
16%
1360
11%
510
68%
510
41%
801
July16th to endNight
59%
564
16%
1417
10%
531
61%
531
37%
865
August1st to 15thNight
65%
527
19%
1517
15%
524
68%
524
35%
881
August16th to endNight
57%
525
17%
1645
15%
525
60%
525
29%
995
September1st to 15thNight
52%
550
17%
1705
14%
550
55%
550
27%
1086
September16th to endNight
50%
657
19%
1815
14%
657
53%
657
29%
1176
October1st to 15thNight
38%
660
16%
1872
11%
660
42%
660
21%
1351
October16th to endNight
24%
704
9%
2288
6%
704
28%
704
11%
1793
November1st to 15thNight
26%
700
14%
2276
11%
700
31%
700
14%
1690
November16th to endNight
20%
750
7%
2385
5%
750
22%
750
8%
2023
December1st to 15thNight
11%
900
2%
2700
1%
900
12%
900
4%
2455
December16th to endNight
12%
960
4%
2739
1%
960
14%
960
6%
2444

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
14%10%47%6%34446%31%
47272
Night
14%11%5%8%7%34446%28%
46820
Cloud CoverDay
14%10%47%6%34446%32%
47281
Night
15%11%5%8%7%34446%28%
46825
TransparencyDay
52%5%11%19%9%
46958
Night
57%411%17%8%
46652
SeeingDay
18%6%26%28%15%4
5869
Night
20%7%28%30%12%1
15902

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
15%17%10%15%10%5%43348%
1432
16th to endDay
11%16%9%16%11%7%7%4237%
1536
February1st to 15thDay
11%14%8%13%15%5%7%33411%
1577
16th to endDay
11%16%8%13%11%5%5%44413%
1580
March1st to 15thDay
11%11%410%9%3445%5%27%
1808
16th to endDay
14%10%5%7%6%25%447%31%
2171
April1st to 15thDay
19%12%34424345%32%
2151
16th to endDay
17%10%35%434446%35%
2337
May1st to 15thDay
16%7%26%6%34445%36%
2331
16th to endDay
11%5%25%435%5%47%44%
2616
June1st to 15thDay
13%5%345%2445%8%41%
2520
16th to endDay
11%5%245%3445%9%40%
2520
July1st to 15thDay
10%42343446%8%48%
2520
16th to endDay
9%42443446%9%46%
2655
August1st to 15thDay
8%5%244346%6%8%44%
2348
16th to endDay
14%5%24424447%44%
2204
September1st to 15thDay
15%5%25%43445%8%39%
1914
16th to endDay
15%5%24425%46%9%38%
1815
October1st to 15thDay
20%9%36%5%44446%31%
1757
16th to endDay
24%14%48%5%445%5%5%17%
1584
November1st to 15thDay
15%15%5%6%6%3445%7%25%
1582
16th to endDay
16%23%7%11%7%2333414%
1572
December1st to 15thDay
17%19%11%16%10%343228%
1260
16th to endDay
18%22%11%12%7%443248%
1482
January1st to 15thNight
16%17%10%12%10%5%6%33211%
2506
16th to endNight
11%16%8%14%12%7%6%44410%
2688
February1st to 15thNight
11%15%8%12%13%5%5%44414%
2280
16th to endNight
13%14%7%16%9%35%34417%
1893
March1st to 15thNight
12%10%5%8%6%34445%33%
2128
16th to endNight
13%9%5%7%6%2345%5%34%
2064
April1st to 15thNight
20%12%35%423445%32%
1797
16th to endNight
17%8%35%422446%40%
1623
May1st to 15thNight
15%6%26%6%36%6%5%7%33%
1620
16th to endNight
11%6%25%4245%6%8%42%
1496
June1st to 15thNight
13%5%25%5%345%5%7%40%
1405
16th to endNight
9%5%15%5%3446%9%43%
1416
July1st to 15thNight
9%41432435%10%50%
1440
16th to endNight
7%423445%35%8%50%
1513
August1st to 15thNight
6%3245%3447%8%49%
1526
16th to endNight
12%5%25%423347%48%
1645
September1st to 15thNight
13%7%25%5%33345%45%
1705
16th to endNight
16%415%42335%8%43%
1815
October1st to 15thNight
19%8%46%6%23346%34%
1872
16th to endNight
21%11%46%8%45%446%22%
2288
November1st to 15thNight
15%14%48%6%35%446%27%
2276
16th to endNight
18%19%6%9%7%45%435%14%
2385
December1st to 15thNight
16%19%11%13%9%45%3338%
2700
16th to endNight
16%20%10%11%8%444449%
2739

Percentage Cloud Cover SE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
15%18%10%15%11%442338%
1432
16th to endDay
11%16%10%16%12%7%7%3336%
1536
February1st to 15thDay
12%14%9%13%16%46%44312%
1577
16th to endDay
12%16%8%11%12%5%6%44413%
1580
March1st to 15thDay
11%10%411%9%445%46%27%
1818
16th to endDay
14%9%5%7%5%34447%31%
2170
April1st to 15thDay
19%11%35%424345%33%
2151
16th to endDay
16%9%36%43435%6%35%
2337
May1st to 15thDay
16%7%35%6%34445%37%
2331
16th to endDay
10%6%24435%45%7%44%
2616
June1st to 15thDay
13%5%25%5%3445%8%42%
2520
16th to endDay
11%5%25%5%345%5%9%41%
2520
July1st to 15thDay
10%423425%45%8%48%
2520
16th to endDay
9%42342446%10%47%
2655
August1st to 15thDay
8%4245%35%6%6%8%45%
2348
16th to endDay
15%5%24424447%44%
2204
September1st to 15thDay
16%435%33445%8%40%
1914
16th to endDay
15%5%25%3245%6%9%38%
1815
October1st to 15thDay
20%9%36%5%34447%31%
1757
16th to endDay
24%15%47%5%35%446%17%
1584
November1st to 15thDay
15%15%47%5%3445%7%25%
1582
16th to endDay
17%24%8%10%6%3233413%
1572
December1st to 15thDay
16%19%12%17%10%332238%
1260
16th to endDay
18%22%10%13%7%343239%
1482
January1st to 15thNight
16%17%10%13%11%6%5%32210%
2506
16th to endNight
12%15%9%14%13%6%6%34410%
2688
February1st to 15thNight
12%15%9%13%13%5%5%43314%
2273
16th to endNight
13%15%6%16%9%4444417%
1893
March1st to 15thNight
12%10%5%8%6%35%445%33%
2141
16th to endNight
14%10%5%7%6%23446%34%
2064
April1st to 15thNight
21%11%36%413446%32%
1797
16th to endNight
17%8%35%422346%40%
1623
May1st to 15thNight
15%5%26%6%36%5%5%7%33%
1619
16th to endNight
11%6%25%3245%6%8%43%
1496
June1st to 15thNight
13%5%25%5%245%5%6%41%
1405
16th to endNight
10%425%5%35%46%10%43%
1416
July1st to 15thNight
10%3142243411%50%
1440
16th to endNight
6%43443445%8%50%
1513
August1st to 15thNight
6%3245%345%6%9%48%
1526
16th to endNight
12%6%25%424246%47%
1645
September1st to 15thNight
14%6%26%423345%45%
1705
16th to endNight
17%5%146%2235%7%43%
1815
October1st to 15thNight
19%9%37%5%24346%33%
1872
16th to endNight
22%10%49%7%34446%22%
2288
November1st to 15thNight
16%14%46%6%25%45%6%27%
2276
16th to endNight
18%19%7%10%6%445%25%14%
2385
December1st to 15thNight
17%20%10%13%10%35%3338%
2700
16th to endNight
16%20%10%12%8%343449%
2739

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
81%46%5%1
1433
16th to endDay
82%36%5%
1536
February1st to 15thDay
77%38%8%
1579
16th to endDay
72%48%10%2
1580
March1st to 15thDay
57%5%12%16%6%1
1818
16th to endDay
52%5%12%22%5%1
2171
April1st to 15thDay
53%310%21%10%
2151
16th to endDay
49%5%10%15%16%2
2337
May1st to 15thDay
48%49%23%10%3
2331
16th to endDay
37%6%13%25%15%1
2620
June1st to 15thDay
40%5%11%26%14%1
2520
16th to endDay
39%7%14%23%13%1
2520
July1st to 15thDay
33%5%11%30%18%1
2371
16th to endDay
34%7%11%26%17%1
2488
August1st to 15thDay
35%6%13%30%12%
2333
16th to endDay
39%6%11%26%14%2
2204
September1st to 15thDay
41%5%13%26%11%
1914
16th to endDay
41%6%17%24%10%
1815
October1st to 15thDay
54%5%10%21%8%
1757
16th to endDay
68%5%13%9%2
1584
November1st to 15thDay
58%412%16%7%
1582
16th to endDay
75%5%11%7%1
1572
December1st to 15thDay
84%36%5%
1260
16th to endDay
81%38%5%1
1482
January1st to 15thNight
80%37%6%1
2506
16th to endNight
78%49%6%1
2688
February1st to 15thNight
73%49%10%2
2282
16th to endNight
69%411%11%3
1893
March1st to 15thNight
53%5%12%18%9%
2141
16th to endNight
49%412%22%9%
2064
April1st to 15thNight
52%49%21%11%1
1797
16th to endNight
45%410%20%16%2
1623
May1st to 15thNight
48%6%11%20%10%3
1620
16th to endNight
38%5%14%25%13%2
1498
June1st to 15thNight
41%6%12%23%15%
1405
16th to endNight
36%6%15%24%15%1
1416
July1st to 15thNight
30%413%29%19%2
1360
16th to endNight
32%5%15%28%17%1
1417
August1st to 15thNight
30%6%17%31%12%
1517
16th to endNight
37%414%26%15%1
1645
September1st to 15thNight
40%5%13%23%16%
1705
16th to endNight
40%5%15%29%8%
1815
October1st to 15thNight
52%49%21%10%
1872
16th to endNight
62%6%12%13%4
2288
November1st to 15thNight
57%5%13%15%7%
2276
16th to endNight
73%411%7%2
2385
December1st to 15thNight
82%47%5%1
2700
16th to endNight
79%310%41
2739

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
18%7%38%28%5%
90
16th to endDay
32%5%25%29%7%1
96
February1st to 15thDay
18%13%46%17%3
90
16th to endDay
20%9%43%16%9%
81
March1st to 15thDay
21%14%25%25%11%
108
16th to endDay
27%422%29%14%1
288
April1st to 15thDay
28%5%27%27%8%3
270
16th to endDay
21%8%30%22%14%3
270
May1st to 15thDay
20%6%29%23%13%4
288
16th to endDay
13%7%32%26%14%4
516
June1st to 15thDay
17%5%28%29%13%3
495
16th to endDay
12%430%32%14%5%
495
July1st to 15thDay
13%423%31%21%5%
475
16th to endDay
10%424%33%19%7%
515
August1st to 15thDay
12%217%32%24%10%
357
16th to endDay
22%5%14%26%22%8%
268
September1st to 15thDay
19%219%26%19%12%
255
16th to endDay
16%418%33%21%6%
254
October1st to 15thDay
25%6%24%27%12%2
238
16th to endDay
26%11%39%18%4
96
November1st to 15thDay
18%14%22%31%12%1
90
16th to endDay
26%20%22%24%5%
87
December1st to 15thDay
30%31%23%11%11
60
16th to endDay
28%19%42%8%1
87
January1st to 15thNight
25%10%32%24%6%
900
16th to endNight
18%11%36%25%7%
960
February1st to 15thNight
19%8%36%27%6%
761
16th to endNight
22%12%28%28%8%
631
March1st to 15thNight
17%9%32%29%9%
720
16th to endNight
18%7%28%34%10%1
720
April1st to 15thNight
26%7%29%28%7%
539
16th to endNight
19%6%31%30%10%1
540
May1st to 15thNight
18%6%28%34%11%
540
16th to endNight
14%5%26%35%17%
563
June1st to 15thNight
18%424%37%14%
505
16th to endNight
12%223%40%19%1
516
July1st to 15thNight
12%115%41%26%1
510
16th to endNight
9%120%38%26%2
564
August1st to 15thNight
7%116%43%28%2
527
16th to endNight
13%216%40%24%2
525
September1st to 15thNight
20%219%30%21%5%
550
16th to endNight
19%319%32%21%4
657
October1st to 15thNight
25%424%30%14%1
660
16th to endNight
29%10%28%24%5%
704
November1st to 15thNight
25%10%30%25%7%
700
16th to endNight
29%11%31%22%4
750
December1st to 15thNight
26%14%36%18%3
900
16th to endNight
25%9%37%23%3
960
Page generated at 2017-08-13 14:16:18. Version ac04

Copyright 2017 A. Danko


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