The Shoals
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Shoals clear sky chart from 2005-11-05 to 2017-09-16.

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
53%
15403
24%
46769
19%
15359
59%
15359
31%
28172

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
32%
900
23%
2506
11%
895
43%
895
27%
1633
January16th to endNight
31%
791
25%
2327
13%
791
41%
791
25%
1542
February1st to 15thNight
31%
704
21%
2112
10%
701
41%
701
26%
1358
February16th to endNight
32%
631
23%
1893
13%
631
40%
631
24%
1232
March1st to 15thNight
33%
720
19%
2160
11%
720
40%
720
25%
1392
March16th to endNight
45%
648
22%
2019
16%
648
51%
648
31%
1208
April1st to 15thNight
47%
539
26%
1797
20%
539
57%
539
33%
1008
April16th to endNight
53%
540
25%
1800
20%
540
62%
540
34%
993
May1st to 15thNight
57%
540
22%
1662
17%
540
62%
540
30%
1008
May16th to endNight
68%
561
21%
1682
19%
561
70%
561
35%
973
June1st to 15thNight
76%
540
21%
1554
18%
540
77%
540
40%
899
June16th to endNight
79%
540
25%
1440
20%
540
80%
540
44%
836
July1st to 15thNight
77%
510
17%
1360
16%
510
78%
510
37%
854
July16th to endNight
80%
564
20%
1607
21%
531
82%
531
40%
901
August1st to 15thNight
82%
539
20%
1788
24%
536
82%
536
36%
980
August16th to endNight
75%
573
22%
1910
27%
573
75%
573
29%
1143
September1st to 15thNight
70%
582
22%
1842
22%
582
71%
582
32%
1080
September16th to endNight
65%
661
29%
1826
24%
661
67%
661
36%
1105
October1st to 15thNight
65%
660
35%
1815
30%
660
68%
660
41%
1045
October16th to endNight
57%
704
33%
2169
29%
704
64%
704
37%
1222
November1st to 15thNight
55%
700
31%
2276
29%
700
63%
700
37%
1239
November16th to endNight
44%
720
27%
2340
21%
720
52%
720
29%
1369
December1st to 15thNight
41%
720
24%
2340
17%
720
51%
720
27%
1453
December16th to endNight
35%
816
20%
2544
14%
816
43%
816
23%
1699

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
11%5%25%5%35%5%5%7%42%
47973
Night
11%5%2442445%7%47%
46962
TransparencyDay
39%5%11%21%17%4
47668
Night
35%411%22%20%5%
46771
SeeingDay
12%314%23%27%18%
5507
Night
14%420%32%24%4
15405

By Month

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
19%7%36%422335%41%
1432
16th to endDay
18%5%2442335%5%43%
1889
February1st to 15thDay
17%7%36%423245%41%
1750
16th to endDay
16%7%35%5%23435%41%
1580
March1st to 15thDay
15%7%26%5%3445%6%37%
1800
16th to endDay
13%6%25%5%35%45%8%38%
2212
April1st to 15thDay
12%5%344235%5%7%45%
2151
16th to endDay
10%435%43445%7%45%
2160
May1st to 15thDay
13%436%5%35%5%47%41%
2289
16th to endDay
9%5%26%6%35%46%8%40%
2431
June1st to 15thDay
5%4246%36%6%7%8%43%
2401
16th to endDay
43246%46%7%7%11%41%
2520
July1st to 15thDay
8%5%25%7%48%6%8%10%33%
2520
16th to endDay
5%435%6%46%6%8%11%35%
2445
August1st to 15thDay
5%326%6%47%6%9%10%38%
2160
16th to endDay
9%6%26%6%46%5%6%10%34%
2292
September1st to 15thDay
11%6%25%6%45%5%6%7%39%
2106
16th to endDay
10%5%25%433446%49%
1824
October1st to 15thDay
10%5%243345%46%49%
1815
16th to endDay
11%413322345%56%
1700
November1st to 15thDay
11%41332334455%
1582
16th to endDay
15%5%144225%35%48%
1620
December1st to 15thDay
19%8%25%5%23445%37%
1620
16th to endDay
19%10%36%422335%39%
1674
January1st to 15thNight
17%7%24423445%44%
2506
16th to endNight
16%7%35%5%33445%41%
2327
February1st to 15thNight
16%7%35%423335%43%
2103
16th to endNight
16%6%35%5%24345%42%
1893
March1st to 15thNight
15%5%35%43445%7%40%
2160
16th to endNight
13%5%23424446%47%
2019
April1st to 15thNight
11%42432346%8%48%
1797
16th to endNight
11%32332445%7%51%
1800
May1st to 15thNight
10%425%42445%8%44%
1661
16th to endNight
5%424435%5%5%9%48%
1682
June1st to 15thNight
43136%35%46%11%49%
1554
16th to endNight
22135%26%5%7%10%51%
1440
July1st to 15thNight
5%3345%35%6%8%10%42%
1440
16th to endNight
3324325%5%8%15%44%
1718
August1st to 15thNight
32145%35%7%8%11%46%
1800
16th to endNight
6%425%6%35%5%7%9%42%
1910
September1st to 15thNight
11%4134345%5%8%47%
1842
16th to endNight
9%5%23424346%51%
1826
October1st to 15thNight
9%414323345%56%
1815
16th to endNight
14%6%1331222457%
2169
November1st to 15thNight
11%41331335%5%55%
2276
16th to endNight
15%6%2331333450%
2340
December1st to 15thNight
16%5%24323446%43%
2340
16th to endNight
19%8%25%4235%45%39%
2544

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
47%26%17%22%3
1433
16th to endDay
42%37%22%20%3
1889
February1st to 15thDay
45%28%21%18%3
1752
16th to endDay
45%29%20%18%4
1580
March1st to 15thDay
47%48%18%15%5%
1800
16th to endDay
43%413%21%15%
2213
April1st to 15thDay
37%310%23%18%6%
2151
16th to endDay
36%49%26%20%3
2160
May1st to 15thDay
42%410%22%16%4
2289
16th to endDay
40%414%25%13%2
2435
June1st to 15thDay
33%7%14%25%16%1
2401
16th to endDay
31%7%14%22%19%3
2520
July1st to 15thDay
40%7%19%19%9%3
2371
16th to endDay
37%7%18%24%10%
2293
August1st to 15thDay
36%8%16%20%14%2
2148
16th to endDay
44%6%12%23%10%2
2292
September1st to 15thDay
42%6%14%18%13%4
2106
16th to endDay
36%5%8%22%23%5%
1824
October1st to 15thDay
34%47%20%25%6%
1815
16th to endDay
30%3420%32%9%
1700
November1st to 15thDay
32%26%18%30%9%
1582
16th to endDay
37%46%21%24%5%
1620
December1st to 15thDay
48%38%19%15%5%
1620
16th to endDay
48%210%19%15%2
1674
January1st to 15thNight
42%36%20%22%4
2506
16th to endNight
45%36%21%18%5%
2327
February1st to 15thNight
44%18%21%18%4
2112
16th to endNight
44%36%21%20%3
1893
March1st to 15thNight
42%49%19%16%7%
2160
16th to endNight
36%411%26%18%2
2019
April1st to 15thNight
32%411%24%20%6%
1797
16th to endNight
31%312%23%23%4
1800
May1st to 15thNight
36%5%12%21%20%3
1662
16th to endNight
31%5%15%26%15%4
1684
June1st to 15thNight
27%6%17%25%20%2
1554
16th to endNight
24%7%14%28%21%3
1440
July1st to 15thNight
31%7%19%25%10%4
1360
16th to endNight
25%7%22%27%15%1
1607
August1st to 15thNight
26%8%20%25%16%2
1788
16th to endNight
35%7%16%23%12%4
1910
September1st to 15thNight
33%5%16%20%17%5%
1842
16th to endNight
32%5%8%20%23%9%
1826
October1st to 15thNight
29%46%21%26%11%
1815
16th to endNight
32%2317%31%12%
2169
November1st to 15thNight
31%25%21%25%14%
2276
16th to endNight
37%26%19%26%7%
2340
December1st to 15thNight
40%48%22%19%5%
2340
16th to endNight
46%310%18%16%3
2544

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
28%7%31%18%11%2
90
16th to endDay
21%6%50%16%32
96
February1st to 15thDay
18%6%51%15%6%1
90
16th to endDay
23%8%32%24%8%2
81
March1st to 15thDay
21%13%38%18%5%2
90
16th to endDay
16%6%27%28%19%
260
April1st to 15thDay
15%10%22%29%18%2
270
16th to endDay
15%319%32%21%7%
270
May1st to 15thDay
14%5%16%29%21%11%
288
16th to endDay
13%312%25%22%22%
331
June1st to 15thDay
8%7%17%32%32%
376
16th to endDay
5%19%24%34%23%
495
July1st to 15thDay
8%15%27%30%26%
475
16th to endDay
5%314%29%45%
358
August1st to 15thDay
9%415%37%31%
313
16th to endDay
10%1319%37%26%
332
September1st to 15thDay
14%1416%36%26%
315
16th to endDay
13%18%21%38%15%
257
October1st to 15thDay
13%114%29%29%11%
255
16th to endDay
17%313%23%33%10%
99
November1st to 15thDay
21%5%23%27%16%5%
90
16th to endDay
17%433%24%15%4
90
December1st to 15thDay
24%436%21%13%
90
16th to endDay
22%9%37%25%5%
96
January1st to 15thNight
21%9%34%27%7%
900
16th to endNight
19%5%37%32%4
791
February1st to 15thNight
20%9%33%31%5%
704
16th to endNight
19%9%34%32%3
631
March1st to 15thNight
18%8%34%32%5%
720
16th to endNight
15%5%28%32%17%
648
April1st to 15thNight
11%5%31%35%14%1
539
16th to endNight
12%325%39%16%2
540
May1st to 15thNight
10%319%38%25%2
540
16th to endNight
7%19%36%36%7%
563
June1st to 15thNight
46%37%43%7%
540
16th to endNight
315%29%48%12%
540
July1st to 15thNight
6%1427%47%13%
510
16th to endNight
4422%47%20%
564
August1st to 15thNight
4222%54%15%
539
16th to endNight
9%1123%52%10%
573
September1st to 15thNight
14%17%25%43%8%
582
16th to endNight
11%28%34%39%3
661
October1st to 15thNight
11%214%34%31%5%
660
16th to endNight
16%317%33%26%2
704
November1st to 15thNight
11%422%37%20%3
700
16th to endNight
16%7%26%33%14%
720
December1st to 15thNight
19%6%28%33%10%
720
16th to endNight
23%6%28%34%6%
816
Page generated at 2017-09-17 11:05:43. Version ac04

Copyright 2017 A. Danko


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