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 2018-04-23.

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
47%
16339
21%
49534
15%
16297
54%
16297
25%
31873

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
26%
780
19%
2522
10%
776
37%
776
16%
1700
January16th to endNight
26%
832
22%
2681
10%
832
39%
832
18%
1779
February1st to 15thNight
28%
763
20%
2292
9%
761
39%
761
20%
1531
February16th to endNight
20%
683
20%
2049
7%
683
31%
683
16%
1415
March1st to 15thNight
26%
780
20%
2236
9%
780
35%
780
20%
1509
March16th to endNight
33%
832
18%
2288
10%
832
40%
832
24%
1548
April1st to 15thNight
41%
685
23%
2048
15%
685
50%
685
29%
1230
April16th to endNight
47%
558
24%
1742
16%
558
55%
558
28%
1070
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
63%
717
25%
1980
22%
717
66%
717
32%
1244
October1st to 15thNight
55%
720
32%
1998
26%
720
62%
720
36%
1181
October16th to endNight
48%
768
33%
2304
25%
768
60%
768
34%
1323
November1st to 15thNight
51%
760
27%
2471
24%
760
60%
760
32%
1402
November16th to endNight
39%
780
26%
2535
18%
780
51%
780
25%
1527
December1st to 15thNight
35%
780
20%
2535
13%
780
44%
780
18%
1705
December16th to endNight
29%
832
18%
2704
12%
832
38%
832
15%
1918

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%5%7%37%
49982
Night
10%6%25%5%3445%7%43%
49732
TransparencyDay
43%7%11%17%15%3
49683
Night
39%7%12%19%17%4
49535
SeeingDay
15%9%19%21%19%14%
6096
Night
14%10%20%28%21%4
16342

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
12%9%37%5%3435%5%38%
1746
16th to endDay
11%8%36%434445%42%
1893
February1st to 15thDay
13%9%5%7%5%24446%35%
1900
16th to endDay
15%7%37%434446%37%
1710
March1st to 15thDay
13%9%45%425%45%7%37%
2053
16th to endDay
12%9%46%5%35%45%6%37%
2287
April1st to 15thDay
10%7%25%5%35%5%6%7%41%
2240
16th to endDay
11%6%25%6%34446%42%
2332
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%
1986
16th to endDay
13%5%25%5%335%6%8%40%
1980
October1st to 15thDay
11%314424445%53%
1961
16th to endDay
11%7%1432322357%
1919
November1st to 15thDay
11%5%24323346%52%
1717
16th to endDay
11%6%34423447%46%
1755
December1st to 15thDay
13%7%46%5%35%5%5%6%36%
1755
16th to endDay
16%11%35%5%34446%34%
1872
January1st to 15thNight
12%7%38%5%35%5%45%38%
2522
16th to endNight
13%9%36%5%34445%39%
2681
February1st to 15thNight
13%9%45%5%25%345%40%
2283
16th to endNight
13%9%37%5%246%4437%
2049
March1st to 15thNight
13%8%35%5%25%45%6%41%
2236
16th to endNight
11%8%35%5%33346%43%
2288
April1st to 15thNight
10%5%2433445%7%49%
2048
16th to endNight
9%5%345%24347%48%
1742
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%48%
1980
October1st to 15thNight
10%413323346%56%
1998
16th to endNight
9%5%2442333356%
2304
November1st to 15thNight
10%5%24323346%53%
2471
16th to endNight
10%7%24433446%47%
2535
December1st to 15thNight
13%7%46%5%35%45%6%37%
2535
16th to endNight
14%11%46%5%45%447%31%
2704

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
46%6%7%16%20%4
1747
16th to endDay
42%5%7%19%18%6%
1893
February1st to 15thDay
49%47%17%17%2
1902
16th to endDay
46%5%9%16%18%3
1710
March1st to 15thDay
45%6%8%15%17%6%
2053
16th to endDay
46%7%13%18%12%2
2288
April1st to 15thDay
40%5%12%21%16%3
2240
16th to endDay
41%6%9%20%18%3
2332
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
1986
16th to endDay
41%5%14%16%19%3
1980
October1st to 15thDay
33%6%9%17%26%6%
1961
16th to endDay
33%25%20%26%10%
1919
November1st to 15thDay
33%47%15%29%8%
1717
16th to endDay
37%47%16%26%7%
1755
December1st to 15thDay
47%5%9%17%16%5%
1755
16th to endDay
50%5%10%14%14%4
1872
January1st to 15thNight
46%6%7%15%18%4
2522
16th to endNight
46%46%16%19%5%
2681
February1st to 15thNight
46%48%18%18%4
2292
16th to endNight
47%6%7%18%16%2
2049
March1st to 15thNight
43%5%8%17%16%6%
2236
16th to endNight
43%5%13%22%14%1
2288
April1st to 15thNight
34%5%11%24%19%4
2048
16th to endNight
36%5%10%22%19%4
1742
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
33%8%13%22%19%2
1980
October1st to 15thNight
30%5%10%21%26%6%
1998
16th to endNight
32%35%20%28%10%
2304
November1st to 15thNight
32%47%19%25%10%
2471
16th to endNight
37%5%6%19%23%7%
2535
December1st to 15thNight
46%6%10%15%16%5%
2535
16th to endNight
52%5%8%15%14%3
2704

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%25%34%14%4
135
16th to endDay
19%38%21%13%6%
144
February1st to 15thDay
25%25%40%8%
135
16th to endDay
30%22%35%11%
120
March1st to 15thDay
27%16%31%16%6%
238
16th to endDay
18%19%28%21%11%1
352
April1st to 15thDay
17%14%27%24%13%2
330
16th to endDay
17%7%21%25%20%6%
289
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%35%18%
315
16th to endDay
12%311%23%34%14%
314
October1st to 15thDay
14%5%17%31%22%8%
315
16th to endDay
15%11%18%25%23%5%
335
November1st to 15thDay
22%8%31%26%8%2
135
16th to endDay
12%16%34%21%12%2
135
December1st to 15thDay
26%21%27%20%2
135
16th to endDay
25%25%36%12%
144
January1st to 15thNight
22%19%28%22%6%
780
16th to endNight
19%20%29%25%4
832
February1st to 15thNight
22%17%28%27%4
764
16th to endNight
20%22%31%21%3
683
March1st to 15thNight
19%19%31%23%5%
780
16th to endNight
17%14%28%27%11%
832
April1st to 15thNight
14%15%25%31%10%1
685
16th to endNight
12%7%27%33%17%1
558
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
12%212%34%34%4
717
October1st to 15thNight
12%6%20%30%24%5%
720
16th to endNight
12%10%21%30%22%2
768
November1st to 15thNight
13%8%20%32%20%4
760
16th to endNight
17%15%24%27%15%1
780
December1st to 15thNight
21%12%25%29%10%1
780
16th to endNight
23%15%27%26%6%
832
Page generated at 2018-04-24 10:03:01. Version ac04

Copyright 2018 A. Danko


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