Denali National Park & Preserve -- Headquarters
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Denali National Park & Preserve -- Headquarters clear sky chart from 2005-11-05 to 2017-09-17.

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
44%
13107
8%
46143
7%
13085
45%
13085
14%
33608

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
45%
776
9%
3223
9%
776
47%
776
13%
2233
January16th to endNight
49%
819
12%
3249
10%
819
52%
819
15%
2218
February1st to 15thNight
51%
731
15%
2705
14%
727
53%
727
19%
1715
February16th to endNight
37%
635
12%
2188
10%
635
39%
635
15%
1547
March1st to 15thNight
56%
570
16%
2190
19%
570
58%
570
18%
1392
March16th to endNight
59%
584
13%
2008
15%
584
59%
584
19%
1342
April1st to 15thNight
44%
539
4%
1603
4%
539
45%
539
15%
1209
April16th to endNight
55%
513
0%
1335
0%
513
55%
513
26%
926
May1st to 15thNight
50%
324
0%
1044
0%
324
50%
324
17%
750
May16th to endNight
53%
188
0%
776
0%
187
54%
187
16%
505
June1st to 15thNight
39%
180
0%
548
0%
180
39%
180
11%
441
June16th to endNight
45%
180
0%
360
0%
180
45%
180
16%
310
July1st to 15thNight
41%
170
0%
605
0%
170
41%
170
10%
490
July16th to endNight
31%
241
0%
788
0%
226
31%
226
7%
665
August1st to 15thNight
31%
358
0%
1074
0%
356
32%
356
7%
912
August16th to endNight
34%
563
0%
1513
0%
563
34%
563
9%
1271
September1st to 15thNight
32%
540
2%
1704
2%
540
33%
540
11%
1343
September16th to endNight
28%
505
3%
1818
4%
505
28%
505
6%
1528
October1st to 15thNight
37%
614
5%
2069
5%
614
37%
614
10%
1648
October16th to endNight
47%
736
8%
2507
7%
736
48%
736
15%
1821
November1st to 15thNight
40%
730
6%
2773
6%
730
41%
730
12%
2070
November16th to endNight
47%
761
12%
3129
14%
761
49%
761
13%
2185
December1st to 15thNight
46%
864
11%
3324
12%
864
48%
864
13%
2430
December16th to endNight
45%
986
7%
3610
6%
986
46%
986
12%
2657

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%11%5%9%7%46%5%5%6%21%
48726
Night
6%10%5%10%8%46%6%6%7%26%
46230
TransparencyDay
60%8%14%11%4
48313
Night
53%8%15%14%6%1
46148
SeeingDay
21%11%21%22%18%5%
8803
Night
12%8%16%25%26%10%
13115

By Month

Percentage Cloud Cover NW (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
10%8%14%7%5%5%5%5%8%29%
716
16th to endDay
15%49%11%5%8%7%6%10%28%
974
February1st to 15thDay
7%38%6%47%7%7%9%36%
1159
16th to endDay
16%5%12%9%47%7%7%8%30%
1286
March1st to 15thDay
27%5%9%8%47%10%7%6%30%
1770
16th to endDay
17%49%8%6%8%7%5%6%31%
2210
April1st to 15thDay
211%6%11%10%5%8%5%7%6%21%
2343
16th to endDay
39%6%9%8%5%6%6%6%7%28%
2623
May1st to 15thDay
6%14%5%8%7%45%5%7%8%24%
2907
16th to endDay
12%10%48%6%36%6%6%7%27%
3337
June1st to 15thDay
21%12%6%9%8%46%5%5%6%14%
3410
16th to endDay
24%10%48%8%45%446%17%
3600
July1st to 15thDay
29%9%47%6%45%5%6%6%15%
3312
16th to endDay
33%11%47%6%45%5%45%10%
3324
August1st to 15thDay
26%14%49%8%35%445%13%
2880
16th to endDay
28%15%5%8%7%345%4412%
2689
September1st to 15thDay
18%12%410%8%45%5%5%6%20%
2255
16th to endDay
17%19%5%8%6%4445%6%16%
1847
October1st to 15thDay
8%17%7%10%6%2445%7%23%
1561
16th to endDay
5%11%6%11%8%35%5%6%7%28%
1363
November1st to 15thDay
313%7%13%9%5%7%45%5%23%
1085
16th to endDay
49%36%7%7%10%7%6%7%27%
829
December1st to 15thDay
311%411%6%38%9%7%7%25%
622
16th to endDay
28%411%6%310%9%7%8%27%
624
January1st to 15thNight
110%7%12%8%46%5%6%7%28%
3223
16th to endNight
19%6%9%8%5%7%7%7%9%27%
3249
February1st to 15thNight
16%48%8%5%6%6%7%7%36%
2693
16th to endNight
19%6%12%9%47%6%5%9%27%
2188
March1st to 15thNight
26%39%8%48%9%6%7%32%
2190
16th to endNight
15%5%9%8%6%7%7%7%7%32%
2008
April1st to 15thNight
211%6%11%8%38%6%6%7%25%
1603
16th to endNight
38%46%8%36%6%8%11%31%
1335
May1st to 15thNight
8%12%46%6%46%7%6%7%29%
1043
16th to endNight
10%9%47%425%7%6%8%34%
776
June1st to 15thNight
18%8%6%9%7%48%46%5%20%
548
16th to endNight
20%7%37%9%35%6%6%7%21%
360
July1st to 15thNight
21%8%5%7%6%36%7%49%18%
645
16th to endNight
29%8%48%7%36%5%48%13%
842
August1st to 15thNight
22%13%5%7%6%46%6%5%7%15%
1080
16th to endNight
26%13%47%4345%46%19%
1513
September1st to 15thNight
15%12%37%8%35%5%6%8%23%
1704
16th to endNight
17%20%6%9%6%36%44415%
1818
October1st to 15thNight
9%15%7%11%7%45%45%7%20%
2069
16th to endNight
6%12%6%11%7%4446%7%28%
2507
November1st to 15thNight
410%7%12%10%47%5%5%6%25%
2773
16th to endNight
39%5%10%7%6%8%7%5%5%30%
3129
December1st to 15thNight
311%5%10%8%37%6%6%8%27%
3324
16th to endNight
19%6%11%8%6%7%7%7%7%25%
3610

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
52%6%13%15%6%5%
716
16th to endDay
47%6%16%18%8%2
974
February1st to 15thDay
39%8%15%20%11%4
1159
16th to endDay
46%9%12%18%12%
1286
March1st to 15thDay
46%8%10%14%16%3
1770
16th to endDay
48%8%12%14%14%2
2210
April1st to 15thDay
59%7%14%14%2
2343
16th to endDay
50%7%18%17%4
2623
May1st to 15thDay
55%7%18%16%2
2907
16th to endDay
52%9%16%16%5%
3341
June1st to 15thDay
70%7%13%7%1
3410
16th to endDay
67%7%14%8%1
3600
July1st to 15thDay
67%9%17%5%
3123
16th to endDay
75%9%12%3
3115
August1st to 15thDay
73%7%15%4
2861
16th to endDay
75%7%11%4
2689
September1st to 15thDay
66%7%15%9%1
2255
16th to endDay
68%7%11%10%1
1847
October1st to 15thDay
59%9%17%7%41
1561
16th to endDay
53%10%17%14%3
1363
November1st to 15thDay
60%7%14%14%3
1085
16th to endDay
49%10%15%13%11%
829
December1st to 15thDay
52%11%11%12%10%1
622
16th to endDay
46%12%22%13%4
624
January1st to 15thNight
51%7%13%16%5%5%
3223
16th to endNight
49%7%14%17%8%2
3249
February1st to 15thNight
42%7%12%19%14%3
2705
16th to endNight
50%7%12%17%10%
2188
March1st to 15thNight
42%8%12%15%17%4
2190
16th to endNight
46%6%10%19%13%3
2013
April1st to 15thNight
55%8%13%19%3
1603
16th to endNight
41%8%23%22%3
1335
May1st to 15thNight
50%8%17%19%4
1044
16th to endNight
46%7%20%19%6%
776
June1st to 15thNight
62%8%16%11%1
548
16th to endNight
60%10%18%9%1
360
July1st to 15thNight
61%11%22%4
605
16th to endNight
67%10%20%2
788
August1st to 15thNight
66%10%16%5%
1074
16th to endNight
64%10%17%7%
1513
September1st to 15thNight
59%9%20%10%
1704
16th to endNight
71%6%10%8%2
1818
October1st to 15thNight
62%7%17%5%5%1
2069
16th to endNight
53%7%21%12%41
2507
November1st to 15thNight
58%6%15%16%2
2773
16th to endNight
50%9%13%15%9%1
3129
December1st to 15thNight
52%10%12%14%8%1
3324
16th to endNight
52%10%18%12%41
3610

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
10%10%16%30%23%10%
30
16th to endDay
38%21%29%28%8%
160
February1st to 15thDay
6%13%12%25%24%18%
211
16th to endDay
9%14%31%22%15%5%
211
March1st to 15thDay
5%10%28%30%19%5%
240
16th to endDay
5%9%22%31%25%6%
411
April1st to 15thDay
7%15%26%23%21%5%
437
16th to endDay
7%11%22%27%25%6%
450
May1st to 15thDay
13%9%21%26%20%7%
468
16th to endDay
15%14%24%26%15%2
677
June1st to 15thDay
24%10%22%22%16%4
798
16th to endDay
23%8%16%19%24%7%
855
July1st to 15thDay
30%7%17%19%19%6%
678
16th to endDay
36%11%21%16%11%3
670
August1st to 15thDay
31%14%23%16%9%4
494
16th to endDay
40%11%18%18%10%1
523
September1st to 15thDay
27%19%24%14%10%4
466
16th to endDay
38%12%19%16%10%2
283
October1st to 15thDay
19%15%18%23%17%6%
225
16th to endDay
11%7%16%26%25%12%
240
November1st to 15thDay
9%8%16%30%22%11%
184
16th to endDay
13%10%10%16%30%20%
30
December1st to 15thDay
6%320%50%20%
30
16th to endDay
318%15%28%18%15%
32
January1st to 15thNight
7%8%16%29%27%9%
780
16th to endNight
5%9%20%32%25%7%
819
February1st to 15thNight
410%18%28%26%11%
734
16th to endNight
6%14%22%29%22%3
635
March1st to 15thNight
5%8%14%38%27%5%
570
16th to endNight
4414%22%35%18%
585
April1st to 15thNight
5%10%19%25%27%10%
539
16th to endNight
7%6%14%23%35%13%
513
May1st to 15thNight
15%6%13%22%28%13%
324
16th to endNight
10%10%15%25%32%5%
188
June1st to 15thNight
20%8%17%23%25%3
180
16th to endNight
20%6%10%17%35%10%
180
July1st to 15thNight
30%39%16%33%7%
170
16th to endNight
27%9%14%19%23%5%
241
August1st to 15thNight
27%10%16%20%17%7%
358
16th to endNight
31%8%11%17%22%8%
563
September1st to 15thNight
22%12%18%18%18%9%
540
16th to endNight
30%10%16%14%21%7%
505
October1st to 15thNight
19%12%13%21%24%9%
614
16th to endNight
12%6%13%29%27%11%
736
November1st to 15thNight
7%7%20%28%24%11%
730
16th to endNight
8%8%18%25%27%11%
761
December1st to 15thNight
9%7%16%24%27%14%
864
16th to endNight
5%9%18%31%23%11%
986
Page generated at 2017-09-18 04:38:19. Version ac04

Copyright 2017 A. Danko


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