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 2017-09-22.

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
52%
15430
25%
46966
18%
15382
58%
15382
32%
27572

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
36%
899
25%
2327
11%
895
43%
895
29%
1540
January16th to endNight
34%
960
28%
2496
11%
960
43%
960
30%
1590
February1st to 15thNight
35%
743
25%
2144
10%
737
45%
737
27%
1346
February16th to endNight
25%
562
26%
1824
9%
562
40%
562
26%
1100
March1st to 15thNight
30%
540
26%
1980
13%
540
45%
540
22%
1207
March16th to endNight
35%
576
23%
2112
15%
576
48%
576
27%
1198
April1st to 15thNight
33%
539
22%
1971
12%
539
48%
539
26%
1127
April16th to endNight
37%
540
24%
1800
17%
540
48%
540
27%
1071
May1st to 15thNight
39%
539
20%
1641
15%
539
47%
539
30%
989
May16th to endNight
56%
563
26%
1685
24%
561
64%
561
38%
957
June1st to 15thNight
75%
540
21%
1620
23%
540
79%
540
48%
827
June16th to endNight
78%
540
19%
1620
22%
540
81%
540
39%
923
July1st to 15thNight
78%
510
21%
1530
24%
510
81%
510
41%
851
July16th to endNight
84%
564
19%
1594
22%
531
85%
531
41%
874
August1st to 15thNight
89%
539
29%
1610
33%
536
89%
536
57%
747
August16th to endNight
76%
573
17%
1947
21%
573
78%
573
29%
1157
September1st to 15thNight
76%
540
17%
1980
20%
540
78%
540
30%
1140
September16th to endNight
71%
513
28%
1891
31%
513
72%
513
32%
1016
October1st to 15thNight
73%
579
34%
1899
31%
579
75%
579
43%
948
October16th to endNight
59%
704
35%
2112
25%
704
66%
704
45%
1100
November1st to 15thNight
52%
700
28%
2100
20%
700
57%
700
33%
1242
November16th to endNight
48%
807
31%
2247
18%
807
55%
807
35%
1333
December1st to 15thNight
38%
900
26%
2340
14%
900
44%
900
27%
1582
December16th to endNight
36%
960
21%
2496
10%
960
42%
960
26%
1707

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%
47902
Night
9%5%2442445%7%50%
47168
TransparencyDay
39%6%11%18%16%7%
47602
Night
32%5%12%21%17%9%
46973
SeeingDay
10%415%26%30%11%
5426
Night
12%5%23%35%20%2
15432

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%24314445%44%
1611
16th to endDay
18%6%2432323447%
1728
February1st to 15thDay
17%7%34313345%45%
1720
16th to endDay
15%8%35%6%2333443%
1649
March1st to 15thDay
22%7%35%422336%38%
1980
16th to endDay
14%7%35%433346%43%
2110
April1st to 15thDay
12%7%35%5%24347%40%
1977
16th to endDay
11%7%26%5%3445%6%41%
2160
May1st to 15thDay
10%6%46%6%35%6%6%8%36%
2306
16th to endDay
9%435%6%46%6%6%8%36%
2430
June1st to 15thDay
43246%46%8%7%9%41%
2340
16th to endDay
6%5%25%6%5%9%8%8%9%31%
2340
July1st to 15thDay
8%335%6%47%7%8%9%35%
2340
16th to endDay
5%325%7%5%7%7%8%11%33%
2466
August1st to 15thDay
3235%35%7%6%11%48%
2340
16th to endDay
6%427%7%47%6%7%10%36%
2249
September1st to 15thDay
7%426%6%37%5%5%8%40%
1980
16th to endDay
6%5%26%6%36%6%6%6%42%
1881
October1st to 15thDay
8%4145%335%36%52%
1719
16th to endDay
10%31332233462%
1760
November1st to 15thDay
8%5%25%435%45%6%48%
1758
16th to endDay
14%5%2442334450%
1710
December1st to 15thDay
18%7%35%5%34335%39%
1620
16th to endDay
17%8%345%25%445%38%
1728
January1st to 15thNight
17%7%24323335%45%
2327
16th to endNight
17%6%23223345%48%
2496
February1st to 15thNight
14%7%35%323235%48%
2141
16th to endNight
14%6%2443334448%
1824
March1st to 15thNight
17%5%25%423347%44%
1980
16th to endNight
9%6%2443435%6%49%
2112
April1st to 15thNight
8%5%35%5%2445%8%46%
1971
16th to endNight
11%5%34433447%47%
1800
May1st to 15thNight
6%5%25%5%35%46%9%44%
1640
16th to endNight
4323425%6%6%10%50%
1683
June1st to 15thNight
221322446%12%57%
1620
16th to endNight
2223435%6%7%12%49%
1620
July1st to 15thNight
5%21343347%11%53%
1620
16th to endNight
32133245%8%12%51%
1702
August1st to 15thNight
211121336%12%64%
1620
16th to endNight
4415%5%35%7%7%11%44%
1947
September1st to 15thNight
5%424425%5%6%9%47%
1980
16th to endNight
8%4135%3346%9%49%
1891
October1st to 15thNight
5%324223346%61%
1899
16th to endNight
8%31322332464%
2112
November1st to 15thNight
9%5%245%24345%52%
2100
16th to endNight
12%424323235%54%
2247
December1st to 15thNight
16%7%35%42335%5%42%
2340
16th to endNight
16%9%25%423336%42%
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
41%39%13%21%10%
1612
16th to endDay
41%35%14%21%14%
1728
February1st to 15thDay
41%26%17%18%13%
1721
16th to endDay
45%37%14%18%11%
1649
March1st to 15thDay
48%36%13%20%7%
1980
16th to endDay
42%47%16%22%6%
2112
April1st to 15thDay
43%47%17%16%10%
1977
16th to endDay
41%5%9%18%17%7%
2160
May1st to 15thDay
44%7%10%16%13%7%
2306
16th to endDay
41%8%12%20%15%2
2434
June1st to 15thDay
32%8%14%23%17%2
2340
16th to endDay
43%10%14%20%9%1
2340
July1st to 15thDay
38%8%18%23%9%
2201
16th to endDay
38%10%21%23%6%
2311
August1st to 15thDay
27%9%19%30%12%
2326
16th to endDay
40%9%20%20%7%1
2249
September1st to 15thDay
39%8%14%20%12%4
1980
16th to endDay
39%7%10%18%16%8%
1881
October1st to 15thDay
32%6%9%19%16%16%
1719
16th to endDay
26%36%15%29%18%
1760
November1st to 15thDay
34%5%11%18%18%9%
1758
16th to endDay
36%46%13%23%16%
1710
December1st to 15thDay
48%38%14%16%7%
1620
16th to endDay
47%47%15%16%8%
1728
January1st to 15thNight
41%25%15%20%13%
2327
16th to endNight
38%35%15%22%14%
2496
February1st to 15thNight
38%45%14%20%16%
2151
16th to endNight
39%37%16%17%14%
1824
March1st to 15thNight
41%47%15%19%11%
1980
16th to endNight
35%411%17%21%9%
2112
April1st to 15thNight
35%5%10%18%17%12%
1971
16th to endNight
37%5%11%20%15%10%
1800
May1st to 15thNight
36%5%14%20%15%9%
1641
16th to endNight
27%7%16%29%16%3
1685
June1st to 15thNight
19%6%17%29%24%2
1620
16th to endNight
26%8%22%29%12%1
1620
July1st to 15thNight
24%8%23%32%11%
1530
16th to endNight
21%10%31%28%7%
1594
August1st to 15thNight
14%5%26%40%13%
1610
16th to endNight
30%11%25%25%6%1
1947
September1st to 15thNight
31%8%20%21%11%5%
1980
16th to endNight
29%6%15%21%17%10%
1891
October1st to 15thNight
22%5%11%25%19%16%
1899
16th to endNight
24%35%16%28%22%
2112
November1st to 15thNight
33%5%9%22%19%9%
2100
16th to endNight
32%46%14%21%19%
2247
December1st to 15thNight
43%39%18%16%8%
2340
16th to endNight
44%37%15%17%10%
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%6%31%32%10%
90
16th to endDay
20%11%41%14%10%1
96
February1st to 15thDay
8%22%35%24%8%
90
16th to endDay
18%19%32%18%11%
81
March1st to 15thDay
26%14%32%18%7%
90
16th to endDay
10%13%28%32%13%2
96
April1st to 15thDay
16%9%31%25%15%2
96
16th to endDay
19%7%28%27%14%1
270
May1st to 15thDay
13%9%34%30%9%1
443
16th to endDay
11%427%32%19%4
517
June1st to 15thDay
5%18%36%38%8%
495
16th to endDay
6%27%30%38%14%
495
July1st to 15thDay
416%31%38%17%
475
16th to endDay
4221%48%22%
515
August1st to 15thDay
6%214%52%23%
493
16th to endDay
13%15%15%40%24%
289
September1st to 15thDay
2422%43%27%
135
16th to endDay
5%113%42%35%
108
October1st to 15thDay
1441%44%8%
90
16th to endDay
18%413%16%37%9%
96
November1st to 15thDay
15%318%37%20%4
90
16th to endDay
21%7%28%25%10%6%
90
December1st to 15thDay
30%321%23%13%8%
90
16th to endDay
27%15%33%18%5%
96
January1st to 15thNight
20%11%26%31%10%
900
16th to endNight
20%10%31%30%7%
960
February1st to 15thNight
17%11%30%33%6%
743
16th to endNight
21%7%42%25%3
562
March1st to 15thNight
20%10%35%27%5%
540
16th to endNight
12%7%40%30%8%
576
April1st to 15thNight
11%8%41%33%5%
539
16th to endNight
15%5%36%30%10%
540
May1st to 15thNight
9%6%40%34%7%
540
16th to endNight
6%329%41%17%1
563
June1st to 15thNight
412%53%26%2
540
16th to endNight
39%48%33%4
540
July1st to 15thNight
46%43%40%4
510
16th to endNight
3341%45%5%
564
August1st to 15thNight
2144%46%4
539
16th to endNight
7%233%49%6%
573
September1st to 15thNight
7%5%30%48%7%
540
16th to endNight
8%18%28%44%7%
513
October1st to 15thNight
7%111%43%31%4
579
16th to endNight
10%422%34%26%2
704
November1st to 15thNight
11%5%25%35%21%1
700
16th to endNight
14%6%26%33%17%1
807
December1st to 15thNight
21%8%25%32%11%
900
16th to endNight
22%9%27%30%8%
960
Page generated at 2017-09-23 05:43:36. Version ac04

Copyright 2017 A. Danko


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