Knik River Swimming Hole
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Knik River Swimming Hole clear sky chart from 2005-11-05 to 2018-01-20.

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
35%
13725
9%
48425
6%
13692
39%
13692
13%
35635

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
32%
869
11%
3454
8%
866
38%
866
13%
2394
January16th to endNight
28%
828
13%
3164
8%
828
34%
828
15%
2205
February1st to 15thNight
31%
734
13%
2608
7%
730
37%
730
18%
1729
February16th to endNight
26%
605
12%
2158
6%
605
31%
605
13%
1538
March1st to 15thNight
36%
570
17%
2172
11%
570
47%
570
18%
1374
March16th to endNight
49%
585
14%
2005
14%
584
53%
584
20%
1313
April1st to 15thNight
40%
539
4%
1648
2%
539
42%
539
13%
1291
April16th to endNight
44%
540
1%
1407
0%
540
45%
540
21%
1037
May1st to 15thNight
44%
389
0%
1110
0%
389
44%
389
15%
857
May16th to endNight
52%
242
0%
936
0%
241
52%
241
15%
654
June1st to 15thNight
43%
180
0%
720
0%
180
43%
180
9%
565
June16th to endNight
45%
180
0%
720
0%
180
45%
180
6%
590
July1st to 15thNight
42%
170
0%
680
0%
170
42%
170
7%
558
July16th to endNight
35%
344
0%
971
0%
322
33%
322
7%
842
August1st to 15thNight
32%
394
0%
1158
0%
392
32%
392
8%
997
August16th to endNight
32%
573
1%
1528
0%
573
32%
573
8%
1325
September1st to 15thNight
29%
540
3%
1751
2%
540
30%
540
6%
1499
September16th to endNight
35%
545
5%
1959
4%
545
36%
545
9%
1553
October1st to 15thNight
36%
666
8%
2241
7%
666
37%
666
12%
1736
October16th to endNight
41%
816
10%
2665
8%
816
43%
816
14%
1987
November1st to 15thNight
33%
805
9%
2911
6%
805
37%
805
14%
2152
November16th to endNight
36%
825
17%
3257
12%
825
45%
825
16%
2167
December1st to 15thNight
32%
858
9%
3458
8%
858
36%
858
10%
2555
December16th to endNight
33%
928
8%
3744
6%
928
37%
928
11%
2717

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%7%45%5%5%7%26%
49185
Night
10%10%47%7%35%5%6%7%30%
48527
TransparencyDay
57%10%14%11%4
48788
Night
53%9%13%13%7%1
48430
SeeingDay
19%11%27%26%14%1
8709
Night
15%9%29%28%15%1
13727

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
5%11%5%8%8%25%45%6%35%
812
16th to endDay
5%12%6%9%6%45%7%6%8%28%
1164
February1st to 15thDay
412%46%6%35%5%47%37%
1255
16th to endDay
5%10%410%6%36%6%5%7%33%
1313
March1st to 15thDay
36%36%5%45%46%6%44%
1788
16th to endDay
310%47%7%36%6%6%8%35%
2211
April1st to 15thDay
414%7%8%8%46%7%7%5%26%
2297
16th to endDay
310%48%6%46%6%6%9%31%
2553
May1st to 15thDay
10%10%48%7%45%5%6%7%27%
2841
16th to endDay
12%8%36%5%35%5%5%7%35%
3178
June1st to 15thDay
16%10%47%7%46%6%6%7%22%
3240
16th to endDay
18%9%37%7%46%6%6%7%21%
3240
July1st to 15thDay
17%10%5%9%7%35%6%6%7%20%
3240
16th to endDay
23%8%47%7%46%5%5%6%20%
3128
August1st to 15thDay
26%8%5%7%7%46%5%5%6%17%
2795
16th to endDay
27%9%48%6%35%45%5%18%
2674
September1st to 15thDay
26%11%27%7%35%5%45%18%
2208
16th to endDay
22%11%36%7%45%5%4423%
2001
October1st to 15thDay
19%11%46%5%35%46%6%27%
1719
16th to endDay
9%10%36%6%345%6%10%33%
1557
November1st to 15thDay
6%13%5%6%5%45%6%5%8%30%
1277
16th to endDay
5%9%48%5%335%5%6%39%
1033
December1st to 15thDay
9%12%47%6%5%445%9%30%
829
16th to endDay
28%410%7%36%7%8%11%27%
832
January1st to 15thNight
5%9%5%7%8%45%5%6%6%34%
3454
16th to endNight
5%12%5%7%6%35%5%6%9%31%
3164
February1st to 15thNight
49%6%6%6%3445%7%40%
2596
16th to endNight
6%10%5%8%7%45%5%7%9%29%
2158
March1st to 15thNight
47%46%7%35%46%6%41%
2172
16th to endNight
310%47%5%445%6%7%39%
2005
April1st to 15thNight
6%18%5%7%7%5%6%6%5%6%24%
1648
16th to endNight
48%47%7%36%7%7%7%35%
1407
May1st to 15thNight
10%9%48%7%46%6%6%6%29%
1109
16th to endNight
11%9%36%425%5%5%8%35%
935
June1st to 15thNight
18%10%47%6%36%5%45%26%
720
16th to endNight
18%9%37%5%46%6%7%7%21%
720
July1st to 15thNight
22%11%5%8%5%25%5%5%7%20%
720
16th to endNight
26%8%48%5%35%5%5%6%18%
1041
August1st to 15thNight
24%9%38%7%46%46%5%19%
1164
16th to endNight
29%9%37%6%435%4419%
1528
September1st to 15thNight
26%11%37%7%45%5%5%6%17%
1751
16th to endNight
23%11%37%6%35%45%6%22%
1959
October1st to 15thNight
18%12%36%7%35%44429%
2241
16th to endNight
10%12%47%6%36%5%5%7%30%
2665
November1st to 15thNight
6%12%38%7%46%5%5%7%32%
2911
16th to endNight
6%9%37%7%35%5%6%7%36%
3257
December1st to 15thNight
9%12%5%8%6%35%5%6%6%30%
3458
16th to endNight
410%5%9%7%46%6%7%8%28%
3744

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
49%8%10%15%11%4
812
16th to endDay
52%9%10%15%10%
1164
February1st to 15thDay
45%9%13%16%12%2
1255
16th to endDay
50%8%14%16%9%1
1313
March1st to 15thDay
38%9%9%15%18%8%
1788
16th to endDay
47%9%13%15%12%1
2211
April1st to 15thDay
59%9%13%13%4
2297
16th to endDay
49%10%18%18%3
2553
May1st to 15thDay
58%8%14%13%4
2841
16th to endDay
48%9%18%19%3
3182
June1st to 15thDay
62%10%15%9%1
3240
16th to endDay
63%11%17%5%2
3240
July1st to 15thDay
64%11%18%3
3051
16th to endDay
66%12%17%2
2935
August1st to 15thDay
69%11%14%3
2776
16th to endDay
68%10%12%6%1
2674
September1st to 15thDay
68%10%12%7%1
2208
16th to endDay
64%9%13%9%3
2001
October1st to 15thDay
58%10%15%11%31
1719
16th to endDay
47%14%16%14%5%1
1557
November1st to 15thDay
52%10%13%14%7%1
1277
16th to endDay
46%8%13%15%13%2
1033
December1st to 15thDay
53%12%13%11%8%1
829
16th to endDay
51%12%13%15%5%1
832
January1st to 15thNight
49%9%11%15%9%5%
3454
16th to endNight
49%9%13%18%9%1
3164
February1st to 15thNight
43%9%10%19%14%2
2608
16th to endNight
50%9%12%15%9%2
2158
March1st to 15thNight
42%7%8%14%17%9%
2172
16th to endNight
42%9%15%17%13%2
2010
April1st to 15thNight
59%8%14%13%4
1648
16th to endNight
44%12%21%17%3
1407
May1st to 15thNight
55%9%15%15%3
1110
16th to endNight
49%9%19%18%3
936
June1st to 15thNight
60%10%18%9%1
720
16th to endNight
61%15%16%5%1
720
July1st to 15thNight
64%11%20%21
680
16th to endNight
65%14%17%2
971
August1st to 15thNight
67%11%16%4
1158
16th to endNight
68%9%13%5%2
1528
September1st to 15thNight
68%10%12%7%
1751
16th to endNight
63%7%15%9%2
1959
October1st to 15thNight
58%8%14%11%6%
2241
16th to endNight
52%10%15%14%6%1
2665
November1st to 15thNight
52%11%12%14%8%
2911
16th to endNight
46%8%11%19%11%2
3257
December1st to 15thNight
55%9%13%11%9%
3458
16th to endNight
53%10%13%14%6%1
3744

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
17%17%24%22%14%3
81
16th to endDay
11%12%33%28%12%
233
February1st to 15thDay
6%14%32%23%15%6%
217
16th to endDay
8%18%33%24%12%1
211
March1st to 15thDay
6%12%37%31%12%
240
16th to endDay
8%11%27%25%23%2
412
April1st to 15thDay
10%15%30%28%14%1
435
16th to endDay
10%10%31%34%12%
450
May1st to 15thDay
15%12%31%26%12%
468
16th to endDay
15%13%31%27%11%1
572
June1st to 15thDay
21%10%30%25%10%
675
16th to endDay
21%8%21%29%17%2
675
July1st to 15thDay
23%5%22%29%17%1
645
16th to endDay
27%8%23%27%12%1
574
August1st to 15thDay
29%12%21%22%12%1
494
16th to endDay
32%12%22%23%8%
523
September1st to 15thDay
31%14%25%19%7%1
460
16th to endDay
29%12%21%21%14%1
324
October1st to 15thDay
28%9%24%21%14%1
270
16th to endDay
16%9%24%24%20%4
288
November1st to 15thDay
14%7%32%25%16%3
266
16th to endDay
12%8%23%30%19%5%
103
December1st to 15thDay
6%15%15%37%20%4
45
16th to endDay
12%14%27%18%22%4
48
January1st to 15thNight
8%15%33%27%13%1
870
16th to endNight
11%10%39%25%11%
828
February1st to 15thNight
5%13%41%27%9%1
734
16th to endNight
11%11%40%26%8%
605
March1st to 15thNight
7%10%37%34%10%
570
16th to endNight
7%7%24%34%24%1
585
April1st to 15thNight
11%9%25%30%21%
539
16th to endNight
8%7%28%32%22%
540
May1st to 15thNight
13%5%24%36%18%1
390
16th to endNight
13%5%22%36%19%2
242
June1st to 15thNight
18%325%33%17%1
180
16th to endNight
22%416%30%25%1
180
July1st to 15thNight
25%5%14%24%30%1
170
16th to endNight
31%6%17%19%23%1
344
August1st to 15thNight
31%5%21%22%16%1
394
16th to endNight
32%5%20%26%14%1
573
September1st to 15thNight
33%7%21%22%13%1
540
16th to endNight
30%7%19%24%16%1
545
October1st to 15thNight
23%9%24%21%20%1
666
16th to endNight
15%8%25%28%20%1
816
November1st to 15thNight
13%7%36%31%10%
805
16th to endNight
10%10%32%31%12%1
825
December1st to 15thNight
14%13%30%23%13%5%
858
16th to endNight
9%12%33%29%13%1
928
Page generated at 2018-01-21 09:19:23. Version ac04

Copyright 2018 A. Danko


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