Washington-on-the-Brazos State Historic Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Washington-on-the-Brazos State Historic Site clear sky chart from 2005-11-05 to 2019-06-10.

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
51%
17711
25%
53880
18%
17663
58%
17663
32%
31841

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
37%
1049
27%
2717
12%
1045
45%
1045
30%
1765
January16th to endNight
34%
1120
26%
2912
10%
1120
43%
1120
30%
1870
February1st to 15thNight
31%
869
22%
2510
9%
863
40%
863
24%
1657
February16th to endNight
24%
654
23%
2124
8%
654
37%
654
22%
1342
March1st to 15thNight
29%
630
25%
2310
13%
630
43%
630
20%
1432
March16th to endNight
34%
672
23%
2464
14%
672
47%
672
26%
1405
April1st to 15thNight
34%
629
23%
2301
14%
629
48%
629
26%
1316
April16th to endNight
38%
624
24%
2078
18%
624
49%
624
28%
1215
May1st to 15thNight
39%
629
22%
1915
17%
629
47%
629
29%
1170
May16th to endNight
56%
659
26%
1973
22%
657
65%
657
40%
1092
June1st to 15thNight
76%
612
24%
1836
27%
612
80%
612
49%
919
June16th to endNight
77%
585
19%
1755
22%
585
80%
585
39%
996
July1st to 15thNight
80%
555
19%
1665
22%
555
82%
555
41%
921
July16th to endNight
85%
612
20%
1738
24%
579
86%
579
43%
931
August1st to 15thNight
89%
575
29%
1717
32%
572
90%
572
57%
797
August16th to endNight
78%
621
17%
2110
20%
621
79%
621
31%
1228
September1st to 15thNight
75%
585
16%
2145
20%
585
76%
585
28%
1263
September16th to endNight
70%
582
26%
2145
29%
582
71%
582
30%
1192
October1st to 15thNight
75%
685
33%
2245
30%
685
77%
685
44%
1113
October16th to endNight
57%
832
34%
2496
24%
832
63%
832
42%
1339
November1st to 15thNight
51%
820
27%
2460
19%
820
56%
820
33%
1464
November16th to endNight
49%
942
31%
2622
17%
942
56%
942
35%
1544
December1st to 15thNight
38%
1050
26%
2730
14%
1050
44%
1050
27%
1845
December16th to endNight
35%
1120
20%
2912
10%
1120
40%
1120
25%
2025

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%41%
54617
Night
10%5%2442445%7%49%
54082
TransparencyDay
40%6%11%19%16%6%
54317
Night
33%5%12%21%17%9%
53887
SeeingDay
12%417%25%27%11%
7608
Night
13%5%23%34%20%2
17713

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
18%6%24414445%44%
1881
16th to endDay
18%6%24323245%46%
2016
February1st to 15thDay
20%8%35%313345%41%
2015
16th to endDay
19%8%35%6%2333438%
1920
March1st to 15thDay
21%7%36%423436%37%
2310
16th to endDay
13%7%35%434446%43%
2462
April1st to 15thDay
12%7%36%5%24347%40%
2307
16th to endDay
11%6%26%5%2435%6%43%
2487
May1st to 15thDay
10%6%36%6%35%6%6%8%36%
2692
16th to endDay
8%425%6%46%7%6%9%38%
2846
June1st to 15thDay
43236%45%8%8%9%43%
2653
16th to endDay
7%5%25%6%5%9%8%8%9%31%
2535
July1st to 15thDay
7%335%6%46%6%8%9%36%
2535
16th to endDay
5%325%7%5%7%7%8%11%37%
2674
August1st to 15thDay
3235%45%7%6%10%48%
2486
16th to endDay
5%426%7%47%6%7%10%37%
2438
September1st to 15thDay
9%426%7%47%5%6%8%37%
2145
16th to endDay
6%5%27%7%46%6%6%6%39%
2145
October1st to 15thDay
8%3145%345%47%51%
2031
16th to endDay
12%41332233459%
2080
November1st to 15thDay
9%6%25%435%45%6%45%
2058
16th to endDay
13%5%24423345%51%
1995
December1st to 15thDay
19%8%35%5%33335%40%
1890
16th to endDay
19%8%35%5%25%34436%
2016
January1st to 15thNight
16%6%24323335%47%
2717
16th to endNight
17%6%24323345%47%
2912
February1st to 15thNight
17%8%35%313236%43%
2507
16th to endNight
16%7%24423345%44%
2124
March1st to 15thNight
17%6%35%423447%41%
2310
16th to endNight
9%6%2443435%7%48%
2464
April1st to 15thNight
8%5%345%2445%9%46%
2301
16th to endNight
10%5%24433446%49%
2078
May1st to 15thNight
8%6%25%5%35%46%8%43%
1914
16th to endNight
4223425%5%6%10%52%
1971
June1st to 15thNight
22222346%12%58%
1836
16th to endNight
3213435%5%7%12%50%
1755
July1st to 15thNight
421343347%11%53%
1755
16th to endNight
22133245%7%12%53%
1846
August1st to 15thNight
21121336%12%64%
1727
16th to endNight
43145%35%7%7%11%45%
2110
September1st to 15thNight
6%4345%25%5%6%9%45%
2145
16th to endNight
8%4145%3446%9%46%
2145
October1st to 15thNight
4324323347%61%
2245
16th to endNight
10%31321222462%
2496
November1st to 15thNight
10%5%24424346%50%
2460
16th to endNight
11%424323345%54%
2622
December1st to 15thNight
17%7%245%2335%5%42%
2730
16th to endNight
18%9%25%423336%40%
2912

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
41%38%14%21%10%
1882
16th to endDay
41%35%15%22%12%
2016
February1st to 15thDay
45%36%15%16%11%
2016
16th to endDay
49%36%13%16%9%
1920
March1st to 15thDay
49%47%13%19%6%
2310
16th to endDay
41%47%18%22%5%
2464
April1st to 15thDay
44%37%18%16%10%
2307
16th to endDay
40%5%9%17%19%7%
2487
May1st to 15thDay
43%6%10%18%13%6%
2692
16th to endDay
38%8%12%22%16%2
2850
June1st to 15thDay
30%8%15%25%17%2
2653
16th to endDay
42%10%14%20%9%1
2535
July1st to 15thDay
38%9%19%21%10%
2396
16th to endDay
35%10%20%25%7%
2519
August1st to 15thDay
27%9%19%29%12%1
2472
16th to endDay
39%9%20%20%8%1
2438
September1st to 15thDay
41%8%14%19%11%4
2145
16th to endDay
41%7%10%17%14%7%
2145
October1st to 15thDay
32%6%10%21%15%13%
2031
16th to endDay
29%26%15%27%18%
2080
November1st to 15thDay
37%6%11%18%17%8%
2058
16th to endDay
35%46%15%23%14%
1995
December1st to 15thDay
48%37%15%17%7%
1890
16th to endDay
50%47%14%15%7%
2016
January1st to 15thNight
40%26%17%20%13%
2717
16th to endNight
39%35%14%22%14%
2912
February1st to 15thNight
44%45%13%17%14%
2517
16th to endNight
43%37%16%16%12%
2124
March1st to 15thNight
43%47%15%18%9%
2310
16th to endNight
36%411%18%20%7%
2464
April1st to 15thNight
35%5%10%19%17%11%
2301
16th to endNight
35%410%20%18%9%
2078
May1st to 15thNight
37%5%13%20%16%7%
1915
16th to endNight
25%6%16%31%16%3
1973
June1st to 15thNight
18%6%17%31%23%2
1836
16th to endNight
26%8%21%29%12%1
1755
July1st to 15thNight
23%8%25%30%11%
1665
16th to endNight
20%9%29%30%9%
1738
August1st to 15thNight
13%5%26%38%13%1
1717
16th to endNight
28%11%25%25%7%1
2110
September1st to 15thNight
33%9%21%20%10%5%
2145
16th to endNight
31%6%15%20%16%8%
2145
October1st to 15thNight
22%5%12%26%18%13%
2245
16th to endNight
27%35%14%27%21%
2496
November1st to 15thNight
34%5%11%22%18%8%
2460
16th to endNight
32%47%17%22%16%
2622
December1st to 15thNight
43%38%18%16%9%
2730
16th to endNight
46%36%15%17%10%
2912

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
18%7%29%31%10%2
180
16th to endDay
23%10%38%17%9%1
192
February1st to 15thDay
26%18%30%18%6%
180
16th to endDay
34%16%30%11%5%
159
March1st to 15thDay
25%14%38%16%5%
180
16th to endDay
11%9%38%29%9%1
192
April1st to 15thDay
16%14%34%20%12%1
186
16th to endDay
18%7%29%27%13%1
379
May1st to 15thDay
13%7%33%31%12%1
589
16th to endDay
9%5%26%33%20%4
677
June1st to 15thDay
5%18%37%39%8%
616
16th to endDay
7%27%31%38%12%
570
July1st to 15thDay
416%28%37%21%
550
16th to endDay
3221%49%23%
595
August1st to 15thDay
5%216%52%22%
549
16th to endDay
10%414%41%28%
350
September1st to 15thDay
10%1320%37%27%
180
16th to endDay
8%1318%41%27%
180
October1st to 15thDay
48%32%33%20%
180
16th to endDay
25%317%21%23%7%
192
November1st to 15thDay
17%318%38%17%2
180
16th to endDay
16%7%28%29%12%5%
180
December1st to 15thDay
31%427%18%10%7%
180
16th to endDay
31%11%32%17%5%
192
January1st to 15thNight
19%10%26%31%11%
1050
16th to endNight
20%10%30%30%7%
1120
February1st to 15thNight
22%10%30%30%6%
869
16th to endNight
24%7%40%24%2
654
March1st to 15thNight
20%11%36%26%5%
630
16th to endNight
12%6%42%29%7%
672
April1st to 15thNight
10%10%39%33%5%
629
16th to endNight
14%5%37%31%10%
624
May1st to 15thNight
11%6%38%34%7%
630
16th to endNight
5%330%41%17%1
659
June1st to 15thNight
411%55%25%2
612
16th to endNight
49%49%32%4
585
July1st to 15thNight
36%41%41%6%
555
16th to endNight
3241%45%5%
612
August1st to 15thNight
2245%45%4
575
16th to endNight
6%235%47%6%
621
September1st to 15thNight
8%5%28%48%8%
585
16th to endNight
9%17%27%45%7%
582
October1st to 15thNight
6%110%41%33%5%
685
16th to endNight
12%422%33%24%2
832
November1st to 15thNight
12%5%25%35%19%1
820
16th to endNight
14%6%25%34%18%1
942
December1st to 15thNight
22%8%25%31%11%
1050
16th to endNight
24%9%26%29%8%
1120
Page generated at 2019-06-10 18:29:49. Version ac04

Copyright 2019 A. Danko


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