Greenville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greenville clear sky chart from 2005-11-05 to 2017-09-20.

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
60%
15100
25%
46904
22%
15069
65%
15069
36%
26128

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
51%
717
19%
2506
18%
716
56%
716
27%
1503
January16th to endNight
46%
768
22%
2511
19%
768
52%
768
25%
1572
February1st to 15thNight
50%
696
20%
2283
18%
696
56%
696
24%
1430
February16th to endNight
49%
632
22%
1895
18%
632
55%
632
25%
1231
March1st to 15thNight
44%
720
14%
2079
11%
720
48%
720
22%
1418
March16th to endNight
43%
768
18%
2046
11%
768
48%
768
25%
1378
April1st to 15thNight
45%
719
17%
1799
8%
719
48%
719
27%
1234
April16th to endNight
53%
720
22%
1800
11%
720
57%
720
38%
1105
May1st to 15thNight
55%
500
24%
1580
18%
500
61%
500
39%
814
May16th to endNight
63%
374
19%
1496
21%
374
66%
374
26%
819
June1st to 15thNight
69%
360
23%
1440
29%
360
75%
360
37%
677
June16th to endNight
80%
360
32%
1440
44%
360
84%
360
56%
536
July1st to 15thNight
90%
340
32%
1360
45%
340
91%
340
68%
443
July16th to endNight
90%
438
40%
1473
46%
411
91%
411
72%
510
August1st to 15thNight
88%
557
37%
1630
31%
554
89%
554
68%
702
August16th to endNight
85%
764
44%
1910
28%
764
86%
764
78%
870
September1st to 15thNight
86%
720
40%
1800
27%
720
87%
720
73%
850
September16th to endNight
78%
675
41%
1828
34%
675
83%
675
66%
839
October1st to 15thNight
64%
660
29%
1980
27%
660
71%
660
44%
1012
October16th to endNight
67%
704
31%
2117
31%
704
72%
704
44%
1112
November1st to 15thNight
59%
700
23%
2275
22%
700
64%
700
31%
1311
November16th to endNight
53%
720
21%
2448
20%
720
58%
720
30%
1382
December1st to 15thNight
48%
720
20%
2520
17%
720
54%
720
21%
1604
December16th to endNight
39%
768
21%
2688
15%
768
48%
768
19%
1776

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
8%6%12212335%59%
47950
Night
9%7%12212346%57%
47082
TransparencyDay
28%38%20%22%16%
47627
Night
29%410%21%20%12%
46905
SeeingDay
16%16%29%22%11%3
5793
Night
13%5%15%34%26%3
15113

By Month

Percentage Cloud Cover SW (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
9%9%1441345%8%45%
1432
16th to endDay
12%13%3321345%6%42%
1712
February1st to 15thDay
13%9%2432345%7%44%
1582
16th to endDay
10%17%3331335%7%39%
1579
March1st to 15thDay
14%13%34323347%37%
1880
16th to endDay
13%16%13313347%40%
2178
April1st to 15thDay
12%13%2432345%6%40%
2149
16th to endDay
10%6%23322345%55%
2160
May1st to 15thDay
6%413223246%62%
2367
16th to endDay
11%6%24423345%50%
2615
June1st to 15thDay
7%323313345%60%
2520
16th to endDay
321122380%
2520
July1st to 15thDay
1111212482%
2520
16th to endDay
111122384%
2592
August1st to 15thDay
2111123381%
2319
16th to endDay
11112386%
2292
September1st to 15thDay
21121232478%
2160
16th to endDay
321112236%74%
1899
October1st to 15thDay
8%32321233464%
1650
16th to endDay
10%423312335%57%
1755
November1st to 15thDay
10%5%1332446%8%50%
1584
16th to endDay
11%8%23333346%48%
1509
December1st to 15thDay
15%9%3431435%9%38%
1440
16th to endDay
15%14%24334446%37%
1536
January1st to 15thNight
9%8%2442335%7%47%
2506
16th to endNight
11%12%23314435%46%
2511
February1st to 15thNight
13%9%2331345%8%43%
2271
16th to endNight
12%14%23323246%44%
1895
March1st to 15thNight
12%14%3432345%8%38%
2079
16th to endNight
12%12%2322335%7%45%
2046
April1st to 15thNight
10%11%234245%5%9%41%
1799
16th to endNight
10%7%12312347%56%
1800
May1st to 15thNight
7%312323236%62%
1580
16th to endNight
10%5%23324445%53%
1496
June1st to 15thNight
6%412212346%64%
1440
16th to endNight
31111222277%
1440
July1st to 15thNight
11111112383%
1440
16th to endNight
111112385%
1574
August1st to 15thNight
1122124478%
1639
16th to endNight
11122483%
1910
September1st to 15thNight
2111123480%
1800
16th to endNight
31111123478%
1828
October1st to 15thNight
7%31221233466%
1980
16th to endNight
8%312212346%61%
2117
November1st to 15thNight
10%5%2231345%8%51%
2275
16th to endNight
10%7%1432235%7%51%
2448
December1st to 15thNight
16%9%23322347%43%
2520
16th to endNight
16%13%23322336%40%
2688

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
38%6%14%26%12%1
1432
16th to endDay
42%5%10%20%13%7%
1712
February1st to 15thDay
40%5%13%23%15%2
1582
16th to endDay
45%5%10%26%10%2
1579
March1st to 15thDay
48%5%9%19%13%3
1880
16th to endDay
45%5%14%19%11%3
2178
April1st to 15thDay
44%5%13%20%14%1
2149
16th to endDay
33%412%26%19%4
2160
May1st to 15thDay
25%310%27%27%6%
2367
16th to endDay
36%410%24%19%4
2619
June1st to 15thDay
26%49%19%24%15%
2520
16th to endDay
10%1416%38%27%
2520
July1st to 15thDay
7%2311%25%49%
2371
16th to endDay
8%2210%22%53%
2430
August1st to 15thDay
9%2312%28%43%
2303
16th to endDay
6%1213%34%42%
2292
September1st to 15thDay
10%2412%32%37%
2160
16th to endDay
13%26%27%29%21%
1899
October1st to 15thDay
24%46%25%28%11%
1650
16th to endDay
29%310%22%22%11%
1755
November1st to 15thDay
32%6%13%24%16%6%
1584
16th to endDay
38%311%25%17%3
1509
December1st to 15thDay
44%5%10%24%14%
1440
16th to endDay
48%6%11%17%14%1
1536
January1st to 15thNight
37%5%13%25%14%2
2506
16th to endNight
41%5%9%18%17%8%
2511
February1st to 15thNight
40%5%10%24%14%3
2283
16th to endNight
42%411%26%12%2
1895
March1st to 15thNight
45%5%13%17%13%4
2079
16th to endNight
40%8%14%22%12%3
2046
April1st to 15thNight
41%6%16%21%11%2
1799
16th to endNight
30%5%12%30%17%4
1800
May1st to 15thNight
25%313%27%23%6%
1581
16th to endNight
33%6%14%24%17%4
1496
June1st to 15thNight
21%7%13%20%24%12%
1440
16th to endNight
13%25%18%37%22%
1440
July1st to 15thNight
8%1410%28%46%
1360
16th to endNight
7%2212%23%52%
1473
August1st to 15thNight
10%2314%28%39%
1630
16th to endNight
7%2316%30%40%
1910
September1st to 15thNight
9%25%11%35%35%
1800
16th to endNight
12%25%24%33%21%
1828
October1st to 15thNight
23%38%25%26%12%
1980
16th to endNight
24%410%26%26%7%
2117
November1st to 15thNight
32%6%12%26%16%5%
2275
16th to endNight
33%412%26%17%5%
2448
December1st to 15thNight
42%6%10%22%17%
2520
16th to endNight
46%5%8%18%18%2
2688

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
46%133%15%3
60
16th to endDay
30%12%22%22%10%1
240
February1st to 15thDay
27%13%25%26%7%
237
16th to endDay
28%17%25%21%6%
238
March1st to 15thDay
32%22%20%13%8%2
270
16th to endDay
28%22%27%14%6%
288
April1st to 15thDay
32%21%23%15%41
269
16th to endDay
24%23%27%17%6%1
270
May1st to 15thDay
17%25%29%18%7%1
288
16th to endDay
19%14%28%17%13%5%
330
June1st to 15thDay
16%17%33%20%9%3
315
16th to endDay
419%33%23%14%4
315
July1st to 15thDay
38%40%28%12%6%
305
16th to endDay
112%40%25%12%7%
327
August1st to 15thDay
414%37%23%13%6%
315
16th to endDay
215%29%25%17%9%
332
September1st to 15thDay
312%27%31%19%5%
315
16th to endDay
8%17%29%26%14%3
272
October1st to 15thDay
13%17%29%20%15%3
255
16th to endDay
20%17%24%26%10%
267
November1st to 15thDay
13%321%21%34%6%
90
16th to endDay
16%18%25%23%15%
71
December1st to 15thDay
40%11%23%21%3
60
16th to endDay
17%18%17%26%18%1
64
January1st to 15thNight
14%5%22%40%15%2
720
16th to endNight
19%6%23%32%16%1
768
February1st to 15thNight
20%6%16%39%15%
704
16th to endNight
23%6%16%36%13%2
632
March1st to 15thNight
23%10%17%30%15%2
720
16th to endNight
21%12%18%26%19%
768
April1st to 15thNight
18%10%21%33%15%1
719
16th to endNight
14%11%17%31%20%4
720
May1st to 15thNight
9%8%20%34%23%1
501
16th to endNight
13%313%28%35%5%
375
June1st to 15thNight
9%313%33%36%3
360
16th to endNight
439%39%41%1
360
July1st to 15thNight
2333%56%3
340
16th to endNight
433%55%5%
438
August1st to 15thNight
25%35%49%7%
557
16th to endNight
19%42%42%4
764
September1st to 15thNight
227%31%47%8%
720
16th to endNight
3410%37%33%10%
675
October1st to 15thNight
11%6%13%32%30%5%
660
16th to endNight
10%314%35%29%5%
704
November1st to 15thNight
13%417%37%23%3
700
16th to endNight
16%7%18%37%19%1
720
December1st to 15thNight
23%5%16%37%15%1
720
16th to endNight
26%7%22%32%11%
768
Page generated at 2017-09-21 04:18:19. Version ac04

Copyright 2017 A. Danko


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