Robert W. Woodruff Scout Reservation
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Robert W. Woodruff Scout Reservation clear sky chart from 2005-11-05 to 2017-09-15.

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
48%
15480
20%
46918
14%
15438
54%
15438
25%
30196

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
25%
720
19%
2327
10%
716
37%
716
16%
1574
January16th to endNight
25%
768
21%
2475
9%
768
38%
768
18%
1652
February1st to 15thNight
29%
703
21%
2112
9%
701
40%
701
21%
1383
February16th to endNight
20%
631
21%
1893
7%
631
32%
631
17%
1293
March1st to 15thNight
27%
720
20%
2064
10%
720
36%
720
21%
1392
March16th to endNight
35%
768
18%
2112
10%
768
41%
768
25%
1409
April1st to 15thNight
40%
632
23%
1890
15%
632
50%
632
29%
1135
April16th to endNight
47%
540
23%
1686
16%
540
55%
540
29%
1034
May1st to 15thNight
50%
540
16%
1620
9%
540
55%
540
26%
1052
May16th to endNight
68%
561
18%
1683
13%
561
70%
561
30%
1051
June1st to 15thNight
71%
540
14%
1620
12%
540
72%
540
28%
1036
June16th to endNight
79%
540
16%
1620
14%
540
80%
540
33%
986
July1st to 15thNight
74%
510
12%
1530
12%
510
74%
510
26%
1005
July16th to endNight
78%
564
15%
1595
13%
531
79%
531
28%
1037
August1st to 15thNight
75%
539
17%
1609
16%
536
75%
536
27%
1066
August16th to endNight
70%
573
19%
1910
20%
573
71%
573
24%
1230
September1st to 15thNight
62%
702
16%
1962
14%
702
63%
702
25%
1328
September16th to endNight
60%
657
22%
1815
19%
657
63%
657
30%
1175
October1st to 15thNight
54%
660
33%
1831
26%
660
61%
660
35%
1090
October16th to endNight
48%
704
31%
2112
23%
704
59%
704
33%
1224
November1st to 15thNight
51%
700
29%
2276
25%
700
60%
700
33%
1265
November16th to endNight
37%
720
24%
2340
16%
720
49%
720
23%
1436
December1st to 15thNight
35%
720
19%
2340
14%
720
43%
720
18%
1575
December16th to endNight
30%
768
18%
2496
12%
768
38%
768
16%
1768

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%6%36%6%35%5%6%7%37%
47808
Night
10%6%25%5%345%5%7%43%
47116
TransparencyDay
44%7%11%17%15%3
47509
Night
39%7%12%19%16%4
46919
SeeingDay
14%8%18%21%20%15%
5352
Night
14%10%20%28%21%4
15483

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
13%9%37%5%3435%5%37%
1611
16th to endDay
12%8%37%434445%41%
1747
February1st to 15thDay
12%9%5%6%5%25%446%36%
1750
16th to endDay
14%7%38%434346%38%
1580
March1st to 15thDay
13%9%45%425%5%5%8%36%
1895
16th to endDay
12%8%45%5%25%45%6%38%
2111
April1st to 15thDay
10%7%25%5%3446%7%41%
2067
16th to endDay
11%6%25%6%34447%42%
2274
May1st to 15thDay
12%6%36%6%45%5%5%6%37%
2331
16th to endDay
9%5%36%7%46%6%6%7%35%
2431
June1st to 15thDay
7%6%36%6%5%7%7%8%9%30%
2340
16th to endDay
5%425%7%47%7%7%11%37%
2340
July1st to 15thDay
9%6%38%8%5%7%7%7%9%25%
2340
16th to endDay
7%5%37%8%6%9%9%8%8%26%
2465
August1st to 15thDay
7%426%8%5%8%7%9%11%28%
2337
16th to endDay
13%6%37%8%5%7%7%6%7%26%
2292
September1st to 15thDay
11%6%38%8%46%6%6%7%30%
1975
16th to endDay
14%5%26%6%3346%8%38%
1815
October1st to 15thDay
11%414324445%53%
1798
16th to endDay
11%7%2432322357%
1759
November1st to 15thDay
10%5%14223345%54%
1582
16th to endDay
12%7%34423447%45%
1620
December1st to 15thDay
12%7%5%6%5%35%5%6%6%35%
1620
16th to endDay
16%11%35%5%34446%35%
1728
January1st to 15thNight
13%7%38%5%35%5%45%38%
2327
16th to endNight
13%9%36%5%34445%38%
2475
February1st to 15thNight
11%9%45%5%25%345%42%
2103
16th to endNight
13%9%37%5%245%4438%
1893
March1st to 15thNight
12%8%35%5%2445%6%41%
2064
16th to endNight
10%8%35%5%33346%43%
2112
April1st to 15thNight
9%425%33445%7%49%
1890
16th to endNight
8%5%345%24347%48%
1686
May1st to 15thNight
10%6%25%435%5%6%9%41%
1619
16th to endNight
6%3244347%7%11%44%
1682
June1st to 15thNight
43245%36%6%8%13%40%
1620
16th to endNight
3224346%6%8%11%46%
1620
July1st to 15thNight
7%3246%37%6%8%11%38%
1620
16th to endNight
43145%46%7%8%13%38%
1703
August1st to 15thNight
5%4246%36%5%7%11%41%
1620
16th to endNight
9%5%25%5%45%6%6%10%39%
1910
September1st to 15thNight
9%5%26%6%45%6%6%8%39%
1962
16th to endNight
8%5%25%425%46%8%44%
1815
October1st to 15thNight
10%413323346%55%
1831
16th to endNight
9%5%2442333456%
2112
November1st to 15thNight
10%5%24323336%54%
2276
16th to endNight
11%7%25%433446%46%
2340
December1st to 15thNight
13%7%46%5%3445%6%37%
2340
16th to endNight
15%11%46%5%445%47%31%
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
47%5%6%16%19%4
1612
16th to endDay
43%5%7%19%18%5%
1747
February1st to 15thDay
48%47%17%18%3
1752
16th to endDay
46%5%8%17%18%3
1580
March1st to 15thDay
45%6%8%15%17%5%
1895
16th to endDay
45%7%13%18%13%2
2112
April1st to 15thDay
40%5%11%21%16%3
2067
16th to endDay
40%6%9%20%18%3
2274
May1st to 15thDay
45%7%11%19%13%2
2331
16th to endDay
44%10%13%17%12%1
2435
June1st to 15thDay
44%11%18%19%5%
2340
16th to endDay
37%11%16%20%12%2
2340
July1st to 15thDay
50%11%16%15%41
2201
16th to endDay
47%12%16%13%8%1
2310
August1st to 15thDay
43%14%15%16%7%1
2324
16th to endDay
53%11%13%13%7%1
2292
September1st to 15thDay
49%9%11%14%11%3
1975
16th to endDay
43%5%14%14%19%3
1815
October1st to 15thDay
33%6%9%17%26%7%
1798
16th to endDay
34%35%20%26%9%
1759
November1st to 15thDay
31%47%15%31%9%
1582
16th to endDay
39%47%16%24%6%
1620
December1st to 15thDay
47%5%9%15%16%5%
1620
16th to endDay
50%5%10%14%15%4
1728
January1st to 15thNight
47%6%7%15%18%4
2327
16th to endNight
47%46%16%19%5%
2475
February1st to 15thNight
44%38%18%19%4
2112
16th to endNight
47%5%7%19%17%2
1893
March1st to 15thNight
43%6%9%18%16%5%
2064
16th to endNight
41%5%13%23%14%1
2112
April1st to 15thNight
34%5%11%24%19%4
1890
16th to endNight
36%6%11%23%18%4
1686
May1st to 15thNight
38%8%15%21%14%1
1620
16th to endNight
29%13%19%24%10%2
1684
June1st to 15thNight
32%13%23%22%7%
1620
16th to endNight
28%11%21%21%13%2
1620
July1st to 15thNight
35%12%23%19%7%1
1530
16th to endNight
31%15%23%19%9%1
1595
August1st to 15thNight
33%14%17%22%11%
1609
16th to endNight
39%9%19%20%10%1
1910
September1st to 15thNight
39%10%16%16%13%3
1962
16th to endNight
36%8%12%20%18%3
1815
October1st to 15thNight
30%6%10%20%25%6%
1831
16th to endNight
33%35%19%28%9%
2112
November1st to 15thNight
31%36%19%27%10%
2276
16th to endNight
39%5%6%19%22%7%
2340
December1st to 15thNight
46%5%10%14%17%6%
2340
16th to endNight
52%5%8%15%15%3
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
23%24%32%17%2
90
16th to endDay
18%41%27%7%5%
96
February1st to 15thDay
23%27%40%8%
90
16th to endDay
32%22%33%11%1
81
March1st to 15thDay
26%13%32%18%8%1
185
16th to endDay
16%17%26%24%13%1
288
April1st to 15thDay
15%14%25%23%16%2
270
16th to endDay
15%7%22%26%20%7%
270
May1st to 15thDay
14%10%29%16%16%13%
288
16th to endDay
11%6%18%26%18%18%
331
June1st to 15thDay
9%29%27%26%24%
315
16th to endDay
8%117%21%22%28%
315
July1st to 15thDay
13%210%22%21%29%
305
16th to endDay
7%419%28%39%
326
August1st to 15thDay
12%211%21%22%29%
313
16th to endDay
14%19%14%30%29%
332
September1st to 15thDay
11%5%12%16%36%18%
311
16th to endDay
15%413%20%33%12%
254
October1st to 15thDay
14%6%18%28%21%9%
255
16th to endDay
14%10%18%25%25%5%
271
November1st to 15thDay
22%7%30%25%11%3
90
16th to endDay
18%17%30%20%12%1
90
December1st to 15thDay
24%27%24%18%31
90
16th to endDay
32%19%33%13%1
96
January1st to 15thNight
23%19%28%22%6%
720
16th to endNight
19%20%30%26%3
768
February1st to 15thNight
21%17%29%28%3
704
16th to endNight
20%22%31%21%3
631
March1st to 15thNight
19%18%31%24%5%
720
16th to endNight
16%13%28%28%12%1
768
April1st to 15thNight
14%15%26%30%11%1
632
16th to endNight
11%7%27%33%17%1
540
May1st to 15thNight
12%7%24%32%19%3
540
16th to endNight
8%213%34%32%8%
563
June1st to 15thNight
5%111%31%39%10%
540
16th to endNight
47%31%43%13%
540
July1st to 15thNight
7%26%25%50%9%
510
16th to endNight
5%5%20%51%16%
564
August1st to 15thNight
8%5%26%45%13%
539
16th to endNight
10%16%24%46%10%
573
September1st to 15thNight
11%210%27%38%9%
702
16th to endNight
13%214%35%30%3
657
October1st to 15thNight
12%6%20%30%22%6%
660
16th to endNight
12%9%22%30%21%3
704
November1st to 15thNight
13%9%21%31%20%4
700
16th to endNight
18%16%24%26%13%
720
December1st to 15thNight
20%13%25%29%10%1
720
16th to endNight
24%15%26%25%6%
768
Page generated at 2017-09-16 00:58:31. Version ac04

Copyright 2017 A. Danko


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