Hope Slide
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hope Slide clear sky chart from 2005-11-05 to 2017-04-30.

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
22%
14099
8%
45552
5%
14071
26%
14071
12%
35391

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
14%
747
9%
2665
4%
743
21%
743
8%
2188
January16th to endNight
16%
768
8%
2688
4%
768
20%
768
9%
2161
February1st to 15thNight
12%
698
5%
2324
2%
698
15%
698
7%
1973
February16th to endNight
18%
632
9%
2002
5%
632
25%
632
10%
1623
March1st to 15thNight
12%
720
4%
2112
1%
720
15%
720
8%
1807
March16th to endNight
11%
768
4%
2035
2%
768
13%
768
8%
1762
April1st to 15thNight
17%
719
4%
1799
2%
719
18%
719
10%
1528
April16th to endNight
22%
506
6%
1580
4%
506
25%
506
10%
1278
May1st to 15thNight
34%
329
10%
1320
13%
329
38%
329
13%
928
May16th to endNight
29%
342
3%
1368
5%
342
30%
342
9%
1064
June1st to 15thNight
27%
330
2%
1194
1%
330
28%
330
12%
904
June16th to endNight
32%
330
3%
1155
1%
330
33%
330
15%
840
July1st to 15thNight
47%
310
7%
1085
5%
310
49%
310
30%
617
July16th to endNight
51%
348
12%
1286
14%
326
57%
326
35%
626
August1st to 15thNight
63%
339
15%
1321
20%
337
67%
337
32%
669
August16th to endNight
44%
596
16%
1646
11%
596
48%
596
33%
1027
September1st to 15thNight
45%
660
19%
1650
9%
660
48%
660
34%
1074
September16th to endNight
35%
656
16%
1796
10%
656
38%
656
20%
1293
October1st to 15thNight
25%
660
10%
1980
8%
660
30%
660
16%
1479
October16th to endNight
19%
704
6%
2222
3%
704
23%
704
10%
1785
November1st to 15thNight
5%
700
5%
2425
2%
700
10%
700
5%
2136
November16th to endNight
14%
720
4%
2520
2%
720
17%
720
7%
2078
December1st to 15thNight
10%
720
6%
2520
2%
720
15%
720
7%
2077
December16th to endNight
5%
797
4%
2859
1%
797
9%
797
5%
2474

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%17%46%42333424%
46203
Night
21%18%46%5%34335%23%
45708
Cloud CoverDay
18%18%5%7%5%34345%24%
46203
Night
16%19%5%8%5%34345%23%
45711
TransparencyDay
63%310%14%6%1
45863
Night
63%311%13%6%1
45552
SeeingDay
28%20%32%14%3
5315
Night
25%13%33%20%7%
14107

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
27%20%5%6%5%2323418%
1272
16th to endDay
19%23%5%6%423335%21%
1536
February1st to 15thDay
21%23%5%8%5%34335%13%
1538
16th to endDay
13%27%8%7%6%3434218%
1472
March1st to 15thDay
18%28%8%8%6%4333311%
1846
16th to endDay
19%28%9%7%6%343348%
2188
April1st to 15thDay
21%32%5%7%42334310%
2149
16th to endDay
21%29%47%42433413%
2357
May1st to 15thDay
19%21%36%423445%24%
2301
16th to endDay
34%14%36%5%25%43415%
2391
June1st to 15thDay
37%13%35%43223320%
2434
16th to endDay
35%8%35%43334421%
2475
July1st to 15thDay
18%5%2442443445%
2475
16th to endDay
15%423323346%50%
2480
August1st to 15thDay
17%41342345%7%45%
2299
16th to endDay
19%5%16%43335%6%40%
2204
September1st to 15thDay
18%5%15%33232448%
1980
16th to endDay
26%10%25%5%23335%32%
1833
October1st to 15thDay
25%11%36%44335%5%25%
1650
16th to endDay
28%17%35%43334420%
1649
November1st to 15thDay
34%24%5%5%3233329%
1432
16th to endDay
20%22%6%6%6%24335%19%
1440
December1st to 15thDay
16%25%7%7%43433419%
1440
16th to endDay
17%29%9%9%6%2232313%
1362
January1st to 15thNight
27%21%5%6%43223418%
2665
16th to endNight
19%22%6%7%5%23347%17%
2688
February1st to 15thNight
23%22%7%6%5%3434415%
2312
16th to endNight
15%25%6%7%5%2343420%
2002
March1st to 15thNight
19%23%7%7%6%3444314%
2112
16th to endNight
21%27%6%6%43433315%
2031
April1st to 15thNight
15%29%48%6%35%33415%
1799
16th to endNight
19%25%46%5%3445%5%18%
1580
May1st to 15thNight
17%18%35%324335%31%
1319
16th to endNight
31%11%35%42445%6%19%
1368
June1st to 15thNight
29%10%35%5%2443425%
1194
16th to endNight
25%10%37%6%23346%27%
1155
July1st to 15thNight
16%413323345%50%
1155
16th to endNight
12%312324437%53%
1381
August1st to 15thNight
10%6%1332335%7%53%
1329
16th to endNight
13%6%15%5%245%5%7%42%
1646
September1st to 15thNight
16%6%2442323351%
1650
16th to endNight
24%9%24424336%32%
1796
October1st to 15thNight
23%11%26%5%4333430%
1980
16th to endNight
28%15%47%5%3444418%
2222
November1st to 15thNight
32%22%5%5%5%3333311%
2425
16th to endNight
24%23%6%6%5%3323416%
2520
December1st to 15thNight
19%21%5%8%5%25%335%17%
2520
16th to endNight
18%27%7%9%6%2333314%
2859

Percentage Cloud Cover SW (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
22%21%5%8%5%23236%17%
1272
16th to endDay
15%23%7%7%423445%21%
1536
February1st to 15thDay
17%23%8%9%6%3335%5%12%
1538
16th to endDay
11%25%8%10%5%3434318%
1472
March1st to 15thDay
13%30%7%11%6%3443310%
1846
16th to endDay
15%28%9%10%7%344447%
2188
April1st to 15thDay
17%30%7%8%5%433449%
2149
16th to endDay
17%26%7%9%5%25%34413%
2357
May1st to 15thDay
14%23%46%6%24445%23%
2301
16th to endDay
29%17%47%5%2444415%
2391
June1st to 15thDay
30%15%36%5%3333419%
2434
16th to endDay
30%12%46%6%3434421%
2475
July1st to 15thDay
14%8%25%423445%44%
2475
16th to endDay
11%5%34422446%50%
2480
August1st to 15thDay
13%5%1433345%7%46%
2299
16th to endDay
15%7%25%5%34446%39%
2204
September1st to 15thDay
15%8%25%32223448%
1980
16th to endDay
21%13%35%433336%31%
1833
October1st to 15thDay
20%14%47%6%34446%25%
1650
16th to endDay
22%19%5%7%5%3334420%
1649
November1st to 15thDay
27%26%6%8%5%243438%
1432
16th to endDay
14%23%7%8%7%33435%18%
1440
December1st to 15thDay
13%24%7%10%5%35%32418%
1440
16th to endDay
14%28%10%11%5%3332312%
1362
January1st to 15thNight
21%23%6%7%42333417%
2664
16th to endNight
15%23%7%7%6%33346%17%
2688
February1st to 15thNight
17%24%7%9%6%3434414%
2312
16th to endNight
11%23%9%10%5%23435%19%
2002
March1st to 15thNight
12%23%8%10%8%445%3414%
2112
16th to endNight
15%26%9%8%5%3443414%
2035
April1st to 15thNight
12%27%6%9%6%35%34415%
1799
16th to endNight
13%24%6%9%5%24446%17%
1580
May1st to 15thNight
15%16%45%5%24446%30%
1319
16th to endNight
22%17%46%5%3345%7%19%
1368
June1st to 15thNight
22%14%36%5%3434425%
1194
16th to endNight
18%13%47%4335%46%27%
1155
July1st to 15thNight
12%6%1441235%7%50%
1155
16th to endNight
8%413434347%54%
1381
August1st to 15thNight
8%6%1332335%7%54%
1329
16th to endNight
9%6%26%5%245%5%7%43%
1646
September1st to 15thNight
11%9%2442333351%
1650
16th to endNight
20%10%16%5%34436%31%
1796
October1st to 15thNight
19%15%45%44333429%
1980
16th to endNight
23%17%48%5%3444418%
2222
November1st to 15thNight
26%24%5%9%5%2323410%
2425
16th to endNight
19%23%7%8%5%3343416%
2520
December1st to 15thNight
15%22%7%10%5%2444417%
2520
16th to endNight
14%26%9%12%7%3333412%
2859

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
69%47%11%5%1
1272
16th to endDay
66%310%11%6%2
1536
February1st to 15thDay
72%5%8%8%41
1538
16th to endDay
71%38%12%3
1472
March1st to 15thDay
78%49%6%1
1846
16th to endDay
80%39%5%
2188
April1st to 15thDay
79%38%7%1
2149
16th to endDay
73%5%11%6%2
2357
May1st to 15thDay
62%413%13%6%
2301
16th to endDay
72%5%11%8%1
2395
June1st to 15thDay
69%310%12%21
2434
16th to endDay
65%411%13%4
2475
July1st to 15thDay
43%411%23%13%3
2316
16th to endDay
34%214%25%17%3
2312
August1st to 15thDay
36%317%30%9%2
2282
16th to endDay
44%313%26%10%1
2204
September1st to 15thDay
40%211%25%17%2
1980
16th to endDay
56%210%17%10%2
1833
October1st to 15thDay
60%212%16%7%
1650
16th to endDay
67%311%14%4
1649
November1st to 15thDay
79%36%6%11
1432
16th to endDay
69%47%10%5%2
1440
December1st to 15thDay
71%46%11%4
1440
16th to endDay
77%45%7%4
1362
January1st to 15thNight
71%36%11%5%1
2665
16th to endNight
69%28%10%6%2
2688
February1st to 15thNight
74%46%9%41
2324
16th to endNight
68%38%14%21
2002
March1st to 15thNight
73%311%8%2
2112
16th to endNight
74%311%9%
2035
April1st to 15thNight
72%312%9%1
1799
16th to endNight
66%5%13%11%2
1580
May1st to 15thNight
55%5%16%16%6%
1320
16th to endNight
63%6%16%10%2
1368
June1st to 15thNight
60%416%12%4
1194
16th to endNight
54%7%18%15%3
1155
July1st to 15thNight
34%418%26%13%1
1085
16th to endNight
26%419%27%19%2
1286
August1st to 15thNight
29%423%29%11%
1321
16th to endNight
35%5%20%26%11%1
1646
September1st to 15thNight
37%313%23%19%2
1650
16th to endNight
52%312%17%10%2
1796
October1st to 15thNight
58%310%18%9%
1980
16th to endNight
68%210%13%4
2222
November1st to 15thNight
78%46%6%21
2425
16th to endNight
72%27%8%6%2
2520
December1st to 15thNight
71%48%12%3
2520
16th to endNight
77%36%7%4
2859

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
315%43%26%10%1
60
16th to endDay
28%14%48%7%1
64
February1st to 15thDay
35%19%31%10%3
198
16th to endDay
28%19%31%16%4
220
March1st to 15thDay
38%31%24%41
270
16th to endDay
35%28%27%8%1
288
April1st to 15thDay
36%22%25%12%2
269
16th to endDay
30%26%27%12%2
267
May1st to 15thDay
32%20%28%15%1
228
16th to endDay
43%12%25%14%21
266
June1st to 15thDay
35%16%28%15%2
379
16th to endDay
33%19%30%13%2
420
July1st to 15thDay
19%18%40%18%1
400
16th to endDay
14%18%44%17%22
289
August1st to 15thDay
15%13%43%19%7%
255
16th to endDay
15%20%37%22%3
268
September1st to 15thDay
25%19%29%16%8%1
255
16th to endDay
25%22%28%17%5%1
255
October1st to 15thDay
25%26%30%10%5%
255
16th to endDay
33%9%36%17%2
161
November1st to 15thDay
35%20%40%3
64
16th to endDay
26%21%23%13%10%5%
60
December1st to 15thDay
28%23%36%8%3
60
16th to endDay
17%20%45%17%
64
January1st to 15thNight
32%16%32%15%2
747
16th to endNight
25%17%37%15%3
768
February1st to 15thNight
29%13%35%17%2
704
16th to endNight
21%17%35%20%4
632
March1st to 15thNight
26%20%34%14%3
720
16th to endNight
28%16%37%13%3
768
April1st to 15thNight
26%15%29%22%4
719
16th to endNight
23%12%35%22%5%
506
May1st to 15thNight
22%6%29%27%13%
330
16th to endNight
26%428%31%9%
343
June1st to 15thNight
26%6%29%27%8%
330
16th to endNight
23%7%30%29%9%
330
July1st to 15thNight
12%5%29%36%15%
310
16th to endNight
9%334%35%16%
348
August1st to 15thNight
10%120%41%25%
339
16th to endNight
12%432%34%16%
596
September1st to 15thNight
15%7%26%23%23%2
660
16th to endNight
24%8%26%26%13%
656
October1st to 15thNight
28%10%29%24%6%
660
16th to endNight
32%13%31%17%4
704
November1st to 15thNight
39%17%34%7%2
700
16th to endNight
30%17%32%14%41
720
December1st to 15thNight
25%17%42%13%1
720
16th to endNight
27%20%42%8%
797
Page generated at 2017-04-30 17:40:05. Version ac04

Copyright 2017 A. Danko


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