Hatcher Pass Lodge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hatcher Pass Lodge clear sky chart from 2005-11-05 to 2017-10-16.

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%
13173
8%
46843
6%
13139
36%
13139
13%
34159

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
35%
780
10%
3196
8%
776
39%
776
14%
2176
January16th to endNight
30%
805
13%
3105
8%
805
36%
805
15%
2140
February1st to 15thNight
32%
734
14%
2619
8%
730
39%
730
18%
1732
February16th to endNight
27%
605
11%
2158
6%
605
32%
605
14%
1543
March1st to 15thNight
35%
570
18%
2178
13%
570
47%
570
21%
1324
March16th to endNight
45%
586
15%
2008
14%
585
48%
585
21%
1283
April1st to 15thNight
33%
539
3%
1641
2%
539
34%
539
13%
1298
April16th to endNight
42%
540
1%
1406
1%
540
42%
540
19%
1040
May1st to 15thNight
37%
377
0%
1098
0%
377
37%
377
15%
848
May16th to endNight
47%
235
0%
908
0%
234
47%
234
16%
616
June1st to 15thNight
36%
180
0%
720
0%
180
36%
180
9%
560
June16th to endNight
39%
180
0%
720
0%
180
39%
180
8%
584
July1st to 15thNight
37%
170
0%
680
0%
170
37%
170
6%
570
July16th to endNight
31%
335
0%
945
0%
313
30%
313
7%
818
August1st to 15thNight
32%
384
0%
1146
0%
382
32%
382
8%
977
August16th to endNight
28%
573
1%
1528
0%
573
28%
573
8%
1316
September1st to 15thNight
28%
540
3%
1746
3%
540
28%
540
7%
1484
September16th to endNight
29%
547
4%
1962
5%
547
30%
547
9%
1585
October1st to 15thNight
35%
664
9%
2239
8%
664
37%
664
14%
1705
October16th to endNight
36%
741
10%
2463
7%
741
38%
741
16%
1780
November1st to 15thNight
28%
730
8%
2693
5%
730
31%
730
13%
1964
November16th to endNight
34%
750
16%
3012
11%
750
43%
750
16%
1956
December1st to 15thNight
33%
776
9%
3216
9%
776
37%
776
11%
2362
December16th to endNight
28%
832
7%
3456
4%
832
31%
832
10%
2498

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
23%15%5%7%6%34445%19%
48669
Night
15%16%6%8%6%34445%25%
46943
TransparencyDay
62%6%14%11%4
48270
Night
57%5%14%14%7%1
46848
SeeingDay
27%5%18%25%18%4
8580
Night
21%7%19%27%20%3
13174

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
9%19%7%9%43434432%
743
16th to endDay
5%21%7%8%5%45%445%26%
1119
February1st to 15thDay
5%18%7%6%5%34445%32%
1242
16th to endDay
5%16%8%9%7%3345%7%26%
1316
March1st to 15thDay
412%6%8%6%3434440%
1782
16th to endDay
415%7%8%7%445%47%29%
2211
April1st to 15thDay
7%23%8%11%8%36%445%17%
2304
16th to endDay
8%16%6%9%6%37%5%5%6%22%
2554
May1st to 15thDay
14%19%47%7%35%445%21%
2853
16th to endDay
20%12%46%6%3445%6%27%
3206
June1st to 15thDay
29%12%47%6%36%445%15%
3240
16th to endDay
32%13%36%5%36%5%5%5%13%
3240
July1st to 15thDay
37%13%47%6%2435%5%9%
3240
16th to endDay
40%10%48%43333412%
3155
August1st to 15thDay
43%11%36%5%243349%
2806
16th to endDay
39%11%47%5%3444312%
2674
September1st to 15thDay
42%12%36%42333313%
2214
16th to endDay
32%15%5%7%5%3333415%
1998
October1st to 15thDay
26%16%36%5%23335%22%
1721
16th to endDay
14%17%37%5%245%5%6%26%
1426
November1st to 15thDay
8%22%6%9%6%3444423%
1165
16th to endDay
11%17%5%8%5%2444433%
948
December1st to 15thDay
11%19%6%9%7%2244426%
744
16th to endDay
321%9%7%9%5%6%45%5%19%
768
January1st to 15thNight
8%16%6%9%6%4434331%
3196
16th to endNight
7%20%7%7%5%345%45%27%
3105
February1st to 15thNight
417%7%8%6%24345%34%
2607
16th to endNight
7%15%8%13%6%3445%6%23%
2158
March1st to 15thNight
5%11%6%8%6%25%445%38%
2178
16th to endNight
5%15%7%8%6%245%46%34%
2008
April1st to 15thNight
8%23%8%11%7%45%34319%
1641
16th to endNight
10%15%6%7%7%46%45%6%25%
1406
May1st to 15thNight
15%18%5%9%6%4444423%
1097
16th to endNight
17%12%5%7%42445%6%28%
907
June1st to 15thNight
28%11%5%8%6%23337%18%
720
16th to endNight
30%10%5%6%5%35%5%5%5%16%
720
July1st to 15thNight
36%8%37%346%436%14%
720
16th to endNight
41%10%35%42225%5%15%
1013
August1st to 15thNight
38%7%47%6%34445%13%
1152
16th to endNight
40%11%45%5%2333317%
1528
September1st to 15thNight
39%11%46%5%3334414%
1746
16th to endNight
32%14%46%5%2434317%
1962
October1st to 15thNight
26%16%36%5%23325%24%
2239
16th to endNight
12%19%47%5%345%5%5%24%
2463
November1st to 15thNight
9%21%5%9%7%35%44423%
2693
16th to endNight
8%17%48%5%35%445%32%
3012
December1st to 15thNight
12%22%6%7%5%34345%24%
3216
16th to endNight
5%18%8%11%8%36%44423%
3456

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%410%16%11%5%
743
16th to endDay
55%312%17%9%
1119
February1st to 15thDay
48%412%16%14%2
1242
16th to endDay
52%5%14%16%10%1
1316
March1st to 15thDay
42%29%18%18%8%
1782
16th to endDay
48%315%17%12%1
2211
April1st to 15thDay
64%413%13%4
2304
16th to endDay
55%6%15%18%3
2554
May1st to 15thDay
60%6%14%14%4
2853
16th to endDay
52%5%17%19%4
3210
June1st to 15thDay
66%7%15%9%1
3240
16th to endDay
66%9%16%5%2
3240
July1st to 15thDay
72%7%17%3
3051
16th to endDay
71%8%16%3
2960
August1st to 15thDay
75%7%13%3
2787
16th to endDay
72%6%12%6%1
2674
September1st to 15thDay
72%7%11%7%1
2214
16th to endDay
69%413%9%2
1998
October1st to 15thDay
61%316%11%41
1721
16th to endDay
51%6%19%15%5%1
1426
November1st to 15thDay
58%313%17%6%
1165
16th to endDay
51%214%16%12%2
948
December1st to 15thDay
58%5%13%12%8%1
744
16th to endDay
60%6%14%13%31
768
January1st to 15thNight
52%5%12%16%9%4
3196
16th to endNight
53%311%19%9%1
3105
February1st to 15thNight
49%39%19%15%3
2619
16th to endNight
55%5%11%16%10%1
2158
March1st to 15thNight
42%38%16%18%9%
2178
16th to endNight
45%415%18%13%2
2013
April1st to 15thNight
64%414%12%4
1641
16th to endNight
52%6%20%15%4
1406
May1st to 15thNight
61%415%16%2
1098
16th to endNight
50%6%18%20%3
908
June1st to 15thNight
65%419%9%1
720
16th to endNight
65%9%18%5%1
720
July1st to 15thNight
69%8%18%2
680
16th to endNight
70%9%16%3
945
August1st to 15thNight
70%7%17%4
1146
16th to endNight
71%7%13%6%2
1528
September1st to 15thNight
71%6%13%7%1
1746
16th to endNight
68%414%9%2
1962
October1st to 15thNight
61%315%13%5%
2239
16th to endNight
55%5%16%14%6%1
2463
November1st to 15thNight
59%315%15%6%
2693
16th to endNight
49%312%19%11%2
3012
December1st to 15thNight
58%5%12%11%10%1
3216
16th to endNight
57%5%15%13%5%1
3456

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
26%10%14%33%8%7%
57
16th to endDay
17%11%18%34%13%3
224
February1st to 15thDay
15%6%24%26%15%11%
216
16th to endDay
9%15%32%24%15%2
211
March1st to 15thDay
8%9%34%32%12%2
240
16th to endDay
10%8%20%25%27%7%
418
April1st to 15thDay
17%7%25%24%22%2
434
16th to endDay
17%8%20%33%18%1
450
May1st to 15thDay
18%8%23%26%20%1
468
16th to endDay
25%6%20%29%15%2
593
June1st to 15thDay
32%6%19%21%17%2
675
16th to endDay
30%213%24%24%4
675
July1st to 15thDay
33%210%24%24%5%
645
16th to endDay
36%312%28%16%3
593
August1st to 15thDay
40%214%21%15%5%
494
16th to endDay
40%413%26%12%2
523
September1st to 15thDay
42%312%24%13%2
460
16th to endDay
37%314%20%18%4
327
October1st to 15thDay
35%414%20%18%5%
270
16th to endDay
22%416%25%20%9%
243
November1st to 15thDay
21%6%24%23%16%7%
224
16th to endDay
17%7%12%29%17%14%
78
December1st to 15thDay
13%36%33%33%10%
30
16th to endDay
21%34%15%18%9%
32
January1st to 15thNight
13%11%24%31%16%3
780
16th to endNight
17%7%28%29%14%1
805
February1st to 15thNight
11%10%31%29%14%3
734
16th to endNight
13%8%34%28%14%
605
March1st to 15thNight
9%9%31%33%13%2
570
16th to endNight
10%7%18%29%30%4
586
April1st to 15thNight
18%6%16%28%25%4
539
16th to endNight
14%6%16%29%31%2
540
May1st to 15thNight
17%5%15%34%23%4
378
16th to endNight
20%311%33%29%2
235
June1st to 15thNight
28%39%28%24%5%
180
16th to endNight
34%35%16%35%4
180
July1st to 15thNight
34%2217%35%6%
170
16th to endNight
42%3416%26%5%
335
August1st to 15thNight
38%29%22%22%4
384
16th to endNight
42%37%20%22%3
573
September1st to 15thNight
40%28%23%20%4
540
16th to endNight
36%312%19%21%5%
547
October1st to 15thNight
32%313%23%23%4
664
16th to endNight
20%6%18%29%21%3
741
November1st to 15thNight
19%6%28%28%14%2
730
16th to endNight
17%10%23%27%18%3
750
December1st to 15thNight
21%8%20%27%15%6%
776
16th to endNight
12%12%27%29%14%4
832
Page generated at 2017-10-17 12:35:28. Version ac04

Copyright 2017 A. Danko


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