Chattahoochee River National Recreation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chattahoochee River National Recreation Area clear sky chart from 2005-11-05 to 2017-04-09.

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
49%
15002
23%
45443
16%
14960
57%
14960
28%
28078

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
27%
720
23%
2327
9%
716
43%
716
22%
1443
January16th to endNight
27%
768
25%
2448
12%
768
42%
768
22%
1542
February1st to 15thNight
32%
703
26%
2112
11%
701
47%
701
27%
1291
February16th to endNight
26%
631
25%
1893
9%
631
40%
631
25%
1184
March1st to 15thNight
32%
720
23%
2064
12%
720
42%
720
28%
1311
March16th to endNight
40%
768
21%
2112
13%
768
46%
768
30%
1320
April1st to 15thNight
42%
618
26%
1834
18%
618
52%
618
33%
1072
April16th to endNight
50%
495
25%
1559
18%
495
59%
495
34%
903
May1st to 15thNight
53%
495
21%
1485
13%
495
59%
495
29%
923
May16th to endNight
65%
513
20%
1538
14%
513
69%
513
32%
940
June1st to 15thNight
74%
495
18%
1485
16%
495
75%
495
31%
922
June16th to endNight
79%
495
17%
1485
15%
495
80%
495
35%
867
July1st to 15thNight
69%
465
14%
1395
13%
465
69%
465
26%
936
July16th to endNight
74%
522
15%
1469
14%
489
76%
489
27%
959
August1st to 15thNight
73%
494
20%
1501
20%
491
73%
491
28%
969
August16th to endNight
66%
525
17%
1750
19%
525
67%
525
21%
1197
September1st to 15thNight
65%
646
20%
1801
19%
646
66%
646
27%
1224
September16th to endNight
62%
657
23%
1815
18%
657
65%
657
29%
1175
October1st to 15thNight
57%
660
33%
1820
26%
660
63%
660
38%
1074
October16th to endNight
53%
704
34%
2112
26%
704
65%
704
39%
1161
November1st to 15thNight
51%
700
30%
2262
26%
700
61%
700
37%
1215
November16th to endNight
41%
720
27%
2340
18%
720
54%
720
30%
1351
December1st to 15thNight
36%
720
23%
2340
14%
720
48%
720
26%
1428
December16th to endNight
32%
768
20%
2496
14%
768
41%
768
19%
1671

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
13%5%2443446%8%42%
45831
Night
12%42442445%7%45%
45642
TransparencyDay
38%7%12%19%17%4
45532
Night
36%6%10%19%20%6%
45445
SeeingDay
15%6%17%22%22%16%
4740
Night
14%6%22%29%22%4
15005

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
16%5%35%323446%42%
1611
16th to endDay
19%5%3332335%5%44%
1773
February1st to 15thDay
16%5%14425%447%43%
1750
16th to endDay
18%5%2442435%5%42%
1580
March1st to 15thDay
15%6%15%43435%8%41%
1896
16th to endDay
17%4143245%5%8%42%
2111
April1st to 15thDay
13%5%2442445%6%46%
1986
16th to endDay
10%414424347%51%
2069
May1st to 15thDay
11%425%425%45%9%44%
2136
16th to endDay
9%4145%345%6%9%44%
2223
June1st to 15thDay
8%414435%5%8%12%38%
2145
16th to endDay
3213436%6%8%12%47%
2145
July1st to 15thDay
11%435%6%47%7%8%11%29%
2145
16th to endDay
7%425%6%48%7%9%10%32%
2283
August1st to 15thDay
9%415%5%38%7%8%11%34%
2116
16th to endDay
14%6%26%7%46%6%7%10%27%
2100
September1st to 15thDay
13%5%35%5%35%5%6%9%36%
1818
16th to endDay
16%5%2442435%5%44%
1815
October1st to 15thDay
12%413312345%56%
1808
16th to endDay
12%32321224458%
1760
November1st to 15thDay
13%41331335%5%55%
1593
16th to endDay
15%425%323445%48%
1620
December1st to 15thDay
17%7%25%423447%39%
1620
16th to endDay
24%7%3443333436%
1728
January1st to 15thNight
18%6%23324345%44%
2327
16th to endNight
17%5%26%433345%44%
2448
February1st to 15thNight
15%5%13423435%48%
2103
16th to endNight
17%42442335%5%45%
1893
March1st to 15thNight
14%5%24424446%47%
2064
16th to endNight
12%424424447%48%
2112
April1st to 15thNight
11%5%133245%48%50%
1834
16th to endNight
11%32341435%8%50%
1559
May1st to 15thNight
9%424435%46%7%45%
1484
16th to endNight
7%3145%35%5%5%8%48%
1538
June1st to 15thNight
6%3245%346%8%13%40%
1485
16th to endNight
3213435%7%8%11%46%
1485
July1st to 15thNight
7%436%6%36%7%7%11%35%
1485
16th to endNight
4325%7%37%7%9%12%36%
1577
August1st to 15thNight
6%434446%6%7%12%40%
1512
16th to endNight
11%6%25%6%45%6%7%9%34%
1750
September1st to 15thNight
9%5%25%6%45%5%5%9%39%
1801
16th to endNight
14%32443445%8%43%
1815
October1st to 15thNight
11%414313347%54%
1820
16th to endNight
10%32332332460%
2112
November1st to 15thNight
11%313223236%57%
2262
16th to endNight
15%413323345%52%
2340
December1st to 15thNight
14%6%35%423347%45%
2340
16th to endNight
21%6%35%42335%6%36%
2496

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
42%49%14%24%4
1612
16th to endDay
41%37%19%21%6%
1773
February1st to 15thDay
40%38%20%22%3
1752
16th to endDay
42%37%20%19%6%
1580
March1st to 15thDay
41%5%9%19%19%4
1896
16th to endDay
39%6%13%20%16%3
2112
April1st to 15thDay
38%49%21%21%4
1986
16th to endDay
32%410%24%23%4
2069
May1st to 15thDay
36%7%14%20%17%2
2136
16th to endDay
34%9%13%25%14%2
2227
June1st to 15thDay
35%11%19%25%7%1
2145
16th to endDay
26%9%17%28%14%2
2145
July1st to 15thDay
42%11%18%17%7%1
2006
16th to endDay
40%14%17%18%8%1
2128
August1st to 15thDay
38%11%17%20%9%1
2103
16th to endDay
49%10%13%15%9%
2100
September1st to 15thDay
41%10%13%17%14%2
1818
16th to endDay
40%5%11%17%20%4
1815
October1st to 15thDay
31%5%8%18%27%8%
1808
16th to endDay
29%36%18%31%11%
1760
November1st to 15thDay
31%27%16%32%9%
1593
16th to endDay
37%46%16%27%7%
1620
December1st to 15thDay
43%48%20%15%7%
1620
16th to endDay
51%48%16%14%5%
1728
January1st to 15thNight
41%37%17%23%5%
2327
16th to endNight
42%35%18%22%7%
2448
February1st to 15thNight
37%37%19%21%9%
2112
16th to endNight
40%36%20%23%5%
1893
March1st to 15thNight
37%5%9%19%19%8%
2064
16th to endNight
35%5%10%23%19%4
2112
April1st to 15thNight
33%49%22%23%7%
1834
16th to endNight
31%5%8%22%22%8%
1559
May1st to 15thNight
35%7%14%20%19%2
1485
16th to endNight
32%8%13%26%14%3
1540
June1st to 15thNight
31%11%20%25%9%1
1485
16th to endNight
26%10%19%23%17%2
1485
July1st to 15thNight
37%11%18%21%8%2
1395
16th to endNight
34%12%20%20%10%1
1469
August1st to 15thNight
34%11%14%25%12%1
1501
16th to endNight
42%10%16%15%12%1
1750
September1st to 15thNight
39%9%13%18%13%4
1801
16th to endNight
37%7%11%19%17%6%
1815
October1st to 15thNight
30%5%10%17%28%8%
1820
16th to endNight
29%25%16%31%13%
2112
November1st to 15thNight
29%36%16%32%12%
2262
16th to endNight
35%36%18%27%9%
2340
December1st to 15thNight
39%49%20%18%7%
2340
16th to endNight
48%38%16%18%5%
2496

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
20%14%33%22%7%2
90
16th to endDay
21%26%36%11%4
96
February1st to 15thDay
14%27%33%22%2
90
16th to endDay
24%14%39%18%2
81
March1st to 15thDay
19%16%26%26%9%1
186
16th to endDay
16%9%31%27%13%2
288
April1st to 15thDay
17%12%31%19%16%2
245
16th to endDay
14%5%19%31%25%3
210
May1st to 15thDay
11%6%24%25%17%15%
228
16th to endDay
13%111%23%28%20%
267
June1st to 15thDay
9%28%18%29%32%
255
16th to endDay
37%23%25%38%
255
July1st to 15thDay
12%5%20%29%31%
245
16th to endDay
8%412%32%40%
270
August1st to 15thDay
12%15%18%32%29%
253
16th to endDay
16%16%21%29%24%
268
September1st to 15thDay
14%15%21%29%26%
255
16th to endDay
20%112%27%27%10%
254
October1st to 15thDay
16%319%25%25%8%
255
16th to endDay
14%5%18%25%28%8%
272
November1st to 15thDay
27%13%19%17%17%2
101
16th to endDay
10%10%33%25%16%4
90
December1st to 15thDay
24%15%31%18%10%
90
16th to endDay
36%12%28%18%4
96
January1st to 15thNight
22%13%31%23%7%
720
16th to endNight
19%13%35%26%4
768
February1st to 15thNight
19%12%31%31%4
704
16th to endNight
18%13%37%26%3
631
March1st to 15thNight
17%10%35%29%6%
720
16th to endNight
14%10%28%31%14%
768
April1st to 15thNight
15%8%30%30%14%
618
16th to endNight
11%427%34%20%1
495
May1st to 15thNight
10%325%33%24%2
495
16th to endNight
10%113%29%36%7%
515
June1st to 15thNight
7%9%32%38%10%
495
16th to endNight
38%32%42%13%
495
July1st to 15thNight
8%16%23%47%12%
465
16th to endNight
6%16%20%52%12%
522
August1st to 15thNight
7%7%24%49%10%
494
16th to endNight
13%5%25%44%9%
525
September1st to 15thNight
12%17%25%44%9%
646
16th to endNight
16%210%36%31%2
657
October1st to 15thNight
14%320%31%24%5%
660
16th to endNight
11%6%22%32%23%4
704
November1st to 15thNight
14%6%25%29%23%2
700
16th to endNight
17%10%28%28%15%
720
December1st to 15thNight
17%9%30%30%10%1
720
16th to endNight
24%10%27%29%7%
768
Page generated at 2017-04-10 09:00:41. Version ac04

Copyright 2017 A. Danko


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