Tomahawk
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tomahawk clear sky chart from 2005-11-06 to 2024-01-12.

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
33%
24855
14%
74668
8%
24797
39%
24797
19%
52866

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 10thNight
22%
950
11%
2648
4%
946
29%
946
15%
2019
January11th to 20thNight
21%
908
10%
2541
4%
908
26%
908
13%
2019
January21st to endNight
21%
990
9%
2758
3%
990
26%
990
13%
2217
February1st to 10thNight
23%
900
13%
2340
4%
900
29%
900
18%
1756
February11th to 20thNight
23%
827
18%
2222
5%
823
32%
823
19%
1605
February21st to endNight
19%
592
14%
1776
4%
592
28%
592
15%
1318
March1st to 10thNight
33%
720
17%
2160
9%
720
38%
720
21%
1461
March11th to 20thNight
29%
617
18%
2057
11%
617
39%
617
20%
1362
March21st to endNight
32%
594
18%
2020
13%
594
40%
594
18%
1399
April1st to 10thNight
26%
540
13%
1800
9%
540
34%
540
17%
1284
April11th to 20thNight
33%
533
17%
1775
13%
533
40%
533
19%
1226
April21st to endNight
32%
540
15%
1696
9%
540
39%
540
19%
1176
May1st to 10thNight
28%
540
12%
1440
6%
540
32%
540
19%
1071
May11th to 20thNight
33%
531
16%
1416
7%
531
40%
531
24%
1002
May21st to endNight
46%
583
11%
1552
5%
582
49%
582
25%
1080
June1st to 10thNight
47%
540
13%
1440
6%
540
51%
540
29%
939
June11th to 20thNight
42%
540
11%
1440
6%
540
45%
540
27%
976
June21st to endNight
52%
540
14%
1440
7%
540
55%
540
33%
920
July1st to 10thNight
60%
525
16%
1400
8%
525
63%
525
43%
805
July11th to 20thNight
53%
522
16%
1392
8%
522
56%
522
34%
873
July21st to endNight
64%
591
21%
1487
12%
558
67%
558
44%
849
August1st to 10thNight
60%
537
19%
1423
13%
534
63%
534
34%
914
August11th to 20thNight
57%
534
20%
1620
17%
534
62%
534
29%
1008
August21st to endNight
55%
594
18%
1980
18%
594
59%
594
27%
1208
September1st to 10thNight
52%
540
20%
1800
19%
540
58%
540
30%
1054
September11th to 20thNight
50%
561
23%
1821
20%
561
56%
561
31%
1084
September21st to endNight
40%
720
17%
1980
10%
720
45%
720
26%
1327
October1st to 10thNight
36%
720
18%
2155
12%
720
42%
720
24%
1417
October11th to 20thNight
29%
720
15%
2160
8%
720
36%
720
18%
1517
October21st to endNight
29%
792
13%
2569
7%
792
36%
792
15%
1874
November1st to 10thNight
28%
740
18%
2406
10%
740
38%
740
20%
1610
November11th to 20thNight
21%
887
13%
2597
5%
887
28%
887
15%
1959
November21st to endNight
22%
950
13%
2660
6%
950
28%
950
15%
2025
December1st to 10thNight
21%
950
9%
2660
2%
950
27%
950
14%
2050
December11th to 20thNight
16%
948
9%
3222
2%
948
22%
948
9%
2536
December21st to endNight
15%
1039
7%
4815
3%
1026
22%
1026
5%
3926

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
14%10%47%6%45%5%5%7%33%
74762
Night
13%10%48%6%35%5%5%7%34%
74977
TransparencyDay
49%7%12%21%10%1
74462
Night
49%7%12%21%10%1
74797
SeeingDay
18%13%31%23%12%4
14845
Night
18%10%32%29%10%1
24864

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 10thDay
11%11%8%10%9%5%6%5%6%7%23%
1517
11th to 20thDay
11%15%8%13%9%5%5%45%7%17%
1448
21st to endDay
12%13%8%13%7%5%6%45%8%19%
1598
February1st to 10thDay
8%13%5%9%8%48%6%6%7%27%
1620
11th to 20thDay
9%10%6%11%8%45%5%6%7%30%
1625
21st to endDay
13%13%7%10%8%45%45%7%25%
1480
March1st to 10thDay
13%12%5%8%7%45%45%6%32%
1800
11th to 20thDay
11%10%5%9%7%35%5%5%6%35%
1918
21st to endDay
17%11%5%7%7%445%6%6%28%
2335
April1st to 10thDay
16%12%5%8%7%45%46%5%29%
2160
11th to 20thDay
20%11%5%7%6%3445%6%29%
2134
21st to endDay
19%10%36%7%35%45%7%30%
2259
May1st to 10thDay
18%8%37%7%35%5%5%7%32%
2520
11th to 20thDay
15%9%47%6%45%5%5%5%36%
2479
21st to endDay
14%8%37%6%35%5%6%8%36%
2725
June1st to 10thDay
13%5%36%5%35%5%5%8%41%
2520
11th to 20thDay
14%6%26%6%36%6%5%8%38%
2520
21st to endDay
11%7%36%5%35%6%6%10%37%
2520
July1st to 10thDay
8%424346%6%8%10%46%
2520
11th to 20thDay
9%6%35%6%35%5%6%7%44%
2520
21st to endDay
9%435%5%46%5%6%9%45%
2743
August1st to 10thDay
10%6%36%6%35%6%6%9%41%
2507
11th to 20thDay
14%6%26%5%345%6%8%42%
2277
21st to endDay
13%7%25%5%345%5%8%43%
2376
September1st to 10thDay
14%7%25%5%2445%8%43%
2160
11th to 20thDay
13%7%36%5%35%5%5%7%41%
2120
21st to endDay
17%9%26%5%445%6%7%34%
1980
October1st to 10thDay
16%9%36%5%45%5%5%7%35%
1800
11th to 20thDay
19%13%48%6%35%5%5%6%25%
1800
21st to endDay
21%13%48%5%34347%28%
1786
November1st to 10thDay
15%11%36%6%35%46%7%34%
1672
11th to 20thDay
14%15%5%12%7%45%5%45%23%
1582
21st to endDay
14%13%5%11%7%35%5%6%6%25%
1520
December1st to 10thDay
12%13%7%13%10%5%6%45%6%20%
1520
11th to 20thDay
12%16%7%12%10%5%6%5%46%17%
1918
21st to endDay
20%23%7%10%7%4442315%
2783
January1st to 10thNight
11%11%5%10%9%5%6%6%6%7%24%
2648
11th to 20thNight
11%14%6%13%8%46%5%47%22%
2541
21st to endNight
11%15%7%12%9%45%5%6%6%20%
2758
February1st to 10thNight
8%11%6%11%8%5%6%5%5%6%29%
2340
11th to 20thNight
8%11%410%7%46%5%5%7%32%
2221
21st to endNight
13%13%6%9%7%46%5%5%6%28%
1776
March1st to 10thNight
12%10%36%6%45%5%5%7%38%
2160
11th to 20thNight
11%11%46%5%4446%5%39%
2057
21st to endNight
16%11%37%5%34446%36%
2020
April1st to 10thNight
20%9%47%5%345%6%6%31%
1800
11th to 20thNight
23%9%45%423446%35%
1775
21st to endNight
18%9%5%7%5%3445%7%34%
1696
May1st to 10thNight
18%10%46%6%45%5%6%6%31%
1440
11th to 20thNight
16%10%36%5%25%447%37%
1416
21st to endNight
13%6%25%6%46%5%6%8%39%
1551
June1st to 10thNight
13%5%25%435%46%8%44%
1440
11th to 20thNight
11%7%37%6%35%6%6%8%40%
1440
21st to endNight
8%6%35%5%35%5%6%10%44%
1440
July1st to 10thNight
8%42432446%9%55%
1440
11th to 20thNight
7%5%35%445%5%6%9%48%
1440
21st to endNight
6%314325%46%9%56%
1575
August1st to 10thNight
8%435%6%35%6%7%8%46%
1432
11th to 20thNight
12%5%25%5%3445%6%48%
1620
21st to endNight
13%6%35%435%45%6%47%
1980
September1st to 10thNight
12%6%25%43445%7%48%
1800
11th to 20thNight
11%5%25%43445%7%49%
1821
21st to endNight
14%8%35%5%3445%8%40%
1980
October1st to 10thNight
15%7%35%5%35%5%5%6%41%
2155
11th to 20thNight
17%12%46%6%235%47%33%
2160
21st to endNight
18%13%36%7%45%5%6%6%28%
2569
November1st to 10thNight
15%10%47%6%24447%37%
2406
11th to 20thNight
14%12%5%10%7%45%45%6%28%
2597
21st to endNight
13%13%5%10%8%45%5%47%26%
2660
December1st to 10thNight
10%14%6%11%8%445%5%7%25%
2660
11th to 20thNight
11%16%7%11%9%45%5%5%5%21%
3279
21st to endNight
22%20%6%10%6%34345%17%
4884

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 10thDay
59%7%10%17%6%1
1518
11th to 20thDay
68%6%7%10%8%
1448
21st to endDay
63%5%12%13%7%1
1598
February1st to 10thDay
55%6%11%17%11%
1620
11th to 20thDay
52%7%10%21%8%2
1634
21st to endDay
59%6%10%17%8%1
1480
March1st to 10thDay
52%5%14%18%10%2
1800
11th to 20thDay
49%5%13%20%10%2
1918
21st to endDay
55%6%10%20%8%1
2335
April1st to 10thDay
55%5%11%17%11%1
2160
11th to 20thDay
56%5%9%19%9%1
2134
21st to endDay
55%5%9%18%12%1
2259
May1st to 10thDay
50%7%13%20%9%1
2520
11th to 20thDay
49%6%11%22%11%1
2483
21st to endDay
46%7%11%24%11%1
2725
June1st to 10thDay
40%8%15%27%11%1
2520
11th to 20thDay
43%8%14%21%13%1
2520
21st to endDay
40%9%18%23%10%1
2520
July1st to 10thDay
30%8%17%31%14%
2451
11th to 20thDay
36%8%13%27%14%3
2445
21st to endDay
33%8%16%26%16%1
2591
August1st to 10thDay
38%8%15%28%9%2
2492
11th to 20thDay
40%8%14%26%11%
2277
21st to endDay
39%7%14%24%15%1
2376
September1st to 10thDay
39%6%14%28%12%1
2160
11th to 20thDay
41%8%18%26%8%
2120
21st to endDay
47%7%12%25%8%
1980
October1st to 10thDay
46%7%13%26%8%
1800
11th to 20thDay
57%7%11%16%7%1
1800
21st to endDay
57%6%12%19%6%
1786
November1st to 10thDay
48%7%12%22%10%1
1672
11th to 20thDay
61%6%10%15%6%1
1582
21st to endDay
58%8%14%16%31
1520
December1st to 10thDay
64%6%10%16%4
1520
11th to 20thDay
66%6%11%12%5%
1915
21st to endDay
74%5%6%10%5%
2783
January1st to 10thNight
56%7%12%17%7%1
2648
11th to 20thNight
61%7%10%15%6%
2541
21st to endNight
63%6%8%15%8%1
2758
February1st to 10thNight
54%6%8%20%11%2
2340
11th to 20thNight
50%6%12%20%10%2
2222
21st to endNight
55%6%12%17%8%1
1776
March1st to 10thNight
46%6%13%23%11%2
2160
11th to 20thNight
46%6%12%22%13%2
2057
21st to endNight
49%6%10%21%12%2
2020
April1st to 10thNight
52%6%8%17%15%1
1800
11th to 20thNight
50%5%9%19%13%3
1775
21st to endNight
48%7%10%21%13%1
1696
May1st to 10thNight
51%7%12%18%10%1
1440
11th to 20thNight
47%6%10%23%12%2
1417
21st to endNight
42%9%14%22%12%1
1552
June1st to 10thNight
37%8%14%30%12%1
1440
11th to 20thNight
41%7%14%22%14%2
1440
21st to endNight
33%9%17%30%10%2
1440
July1st to 10thNight
25%7%16%34%17%1
1400
11th to 20thNight
31%9%15%28%14%3
1392
21st to endNight
25%7%18%32%16%3
1487
August1st to 10thNight
33%10%15%27%14%2
1423
11th to 20thNight
35%8%13%27%15%2
1620
21st to endNight
36%8%13%24%16%3
1980
September1st to 10thNight
34%6%12%31%15%1
1800
11th to 20thNight
33%7%15%34%10%
1821
21st to endNight
42%7%14%27%10%
1980
October1st to 10thNight
41%8%12%28%11%1
2155
11th to 20thNight
49%6%14%21%9%1
2160
21st to endNight
54%7%12%19%8%
2569
November1st to 10thNight
47%5%13%22%13%
2406
11th to 20thNight
56%7%13%14%10%1
2597
21st to endNight
57%6%13%18%5%1
2660
December1st to 10thNight
58%7%13%18%4
2660
11th to 20thNight
63%6%11%15%5%
3281
21st to endNight
70%5%6%14%4
4884

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 10thDay
15%17%33%24%9%2
270
11th to 20thDay
22%12%35%24%6%1
243
21st to endDay
20%13%38%22%7%
264
February1st to 10thDay
17%15%48%15%5%
240
11th to 20thDay
15%21%44%13%7%
240
21st to endDay
18%21%45%14%1
198
March1st to 10thDay
18%20%37%18%8%
240
11th to 20thDay
20%19%34%16%8%3
240
21st to endDay
25%14%30%21%7%3
421
April1st to 10thDay
23%15%32%24%6%
420
11th to 20thDay
31%13%24%23%8%1
412
21st to endDay
24%13%29%22%10%2
421
May1st to 10thDay
22%16%31%21%9%1
603
11th to 20thDay
18%16%31%23%9%4
625
21st to endDay
18%13%27%24%14%4
679
June1st to 10thDay
12%12%32%27%13%4
630
11th to 20thDay
15%9%33%27%11%4
630
21st to endDay
12%9%31%27%16%5%
630
July1st to 10thDay
9%5%26%30%21%9%
621
11th to 20thDay
12%8%28%27%17%8%
618
21st to endDay
7%6%28%33%17%9%
684
August1st to 10thDay
11%5%27%28%24%6%
626
11th to 20thDay
16%5%21%25%25%7%
561
21st to endDay
14%11%24%25%20%6%
495
September1st to 10thDay
16%11%23%26%19%5%
450
11th to 20thDay
13%9%28%30%16%3
450
21st to endDay
20%16%24%26%12%2
450
October1st to 10thDay
19%16%24%29%9%4
270
11th to 20thDay
21%25%32%16%6%
270
21st to endDay
31%16%37%13%3
297
November1st to 10thDay
21%14%36%22%6%2
270
11th to 20thDay
23%21%39%12%4
270
21st to endDay
21%20%41%13%4
270
December1st to 10thDay
18%15%40%20%6%
270
11th to 20thDay
23%19%40%15%21
270
21st to endDay
28%22%34%14%2
297
January1st to 10thNight
15%11%41%27%6%
950
11th to 20thNight
19%11%37%26%7%1
908
21st to endNight
19%9%37%29%6%
990
February1st to 10thNight
14%12%38%29%6%
900
11th to 20thNight
14%14%41%25%6%
827
21st to endNight
19%15%38%23%5%
592
March1st to 10thNight
16%13%34%28%8%1
720
11th to 20thNight
17%11%38%26%7%
617
21st to endNight
21%8%31%27%11%2
594
April1st to 10thNight
23%10%36%24%6%1
540
11th to 20thNight
28%8%27%30%7%
533
21st to endNight
23%9%32%28%7%1
540
May1st to 10thNight
23%11%32%27%6%1
540
11th to 20thNight
21%9%32%29%9%1
531
21st to endNight
15%8%25%36%15%1
584
June1st to 10thNight
13%7%26%41%13%
540
11th to 20thNight
14%7%30%39%10%
540
21st to endNight
11%6%24%43%16%1
540
July1st to 10thNight
8%323%38%24%2
525
11th to 20thNight
9%6%27%35%22%1
522
21st to endNight
8%222%43%22%3
591
August1st to 10thNight
9%221%42%25%1
537
11th to 20thNight
14%220%34%27%2
534
21st to endNight
14%7%22%34%21%2
594
September1st to 10thNight
15%5%22%37%17%4
540
11th to 20thNight
12%5%29%34%18%2
561
21st to endNight
20%10%27%30%13%1
720
October1st to 10thNight
18%9%31%27%14%1
720
11th to 20thNight
22%12%31%26%8%
720
21st to endNight
25%8%33%25%9%
792
November1st to 10thNight
19%10%37%28%5%1
740
11th to 20thNight
19%14%39%22%6%
887
21st to endNight
20%15%35%23%5%
950
December1st to 10thNight
18%13%37%25%6%1
950
11th to 20thNight
20%12%37%23%8%1
950
21st to endNight
27%12%34%23%4
1045
Page generated at 2024-01-09 06:14:40. Version ac07

Copyright 2024 Attilla Danko


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