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Vernonia
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vernonia clear sky chart from 2005-11-05 to 2019-01-28.

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
41%
16379
12%
52241
10%
16352
44%
16352
17%
37483

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%
838
8%
2926
7%
836
34%
836
9%
2373
January16th to endNight
35%
881
9%
2963
9%
881
37%
881
11%
2339
February1st to 15thNight
29%
758
7%
2483
5%
758
32%
758
9%
2061
February16th to endNight
31%
684
9%
2187
6%
684
35%
684
11%
1745
March1st to 15thNight
30%
780
6%
2198
6%
780
31%
780
10%
1830
March16th to endNight
27%
832
5%
2265
4%
832
28%
832
8%
1945
April1st to 15thNight
27%
779
6%
1949
3%
779
28%
779
12%
1630
April16th to endNight
41%
620
10%
1778
6%
620
43%
620
17%
1340
May1st to 15thNight
40%
425
14%
1595
13%
425
47%
425
19%
1007
May16th to endNight
49%
407
9%
1624
10%
406
54%
406
16%
1108
June1st to 15thNight
40%
390
8%
1544
8%
390
46%
390
18%
1003
June16th to endNight
47%
390
14%
1365
13%
390
55%
390
26%
808
July1st to 15thNight
62%
370
19%
1373
20%
370
71%
370
45%
616
July16th to endNight
62%
408
25%
1544
26%
386
78%
386
54%
586
August1st to 15thNight
74%
561
24%
1707
19%
559
80%
559
57%
770
August16th to endNight
66%
692
29%
1934
19%
692
71%
692
48%
1018
September1st to 15thNight
67%
780
27%
1950
15%
780
70%
780
52%
1077
September16th to endNight
56%
776
22%
2147
16%
776
59%
776
33%
1316
October1st to 15thNight
50%
780
18%
2340
17%
780
54%
780
26%
1522
October16th to endNight
44%
832
14%
2519
13%
832
46%
832
18%
1822
November1st to 15thNight
31%
820
8%
2834
8%
820
34%
820
10%
2299
November16th to endNight
34%
840
6%
2940
7%
840
35%
840
11%
2308
December1st to 15thNight
36%
840
10%
2940
10%
840
38%
840
11%
2272
December16th to endNight
22%
896
5%
3136
5%
896
23%
896
6%
2688

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
19%11%47%6%34445%28%
53357
Night
17%9%47%6%34446%31%
52405
Cloud CoverDay
22%10%36%5%24445%29%
53357
Night
20%9%36%5%24445%32%
52409
TransparencyDay
56%5%11%15%9%1
53024
Night
52%6%12%16%9%2
52242
SeeingDay
24%10%25%23%11%3
7538
Night
23%5%20%31%17%1
16388

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%16%5%9%6%3434216%
1672
16th to endDay
23%14%5%8%7%3433321%
1876
February1st to 15thDay
24%16%6%9%6%34435%13%
1711
16th to endDay
22%18%6%11%7%4422416%
1571
March1st to 15thDay
29%17%6%9%6%3334312%
2090
16th to endDay
29%17%6%9%8%35%3339%
2311
April1st to 15thDay
28%16%6%8%6%34345%13%
2329
16th to endDay
23%14%5%8%6%35%44418%
2454
May1st to 15thDay
20%10%47%5%2345%5%29%
2685
16th to endDay
21%10%48%7%45%5%5%6%19%
2839
June1st to 15thDay
22%11%47%7%3445%5%22%
2742
16th to endDay
15%9%36%6%35%45%8%30%
2925
July1st to 15thDay
8%424423346%54%
2837
16th to endDay
8%314323347%56%
2881
August1st to 15thDay
7%5%2442335%7%52%
2494
16th to endDay
7%6%25%42335%6%50%
2619
September1st to 15thDay
6%5%24424446%53%
2340
16th to endDay
15%7%37%5%34446%36%
2139
October1st to 15thDay
20%8%37%5%34345%31%
1950
16th to endDay
24%10%37%6%34335%27%
2057
November1st to 15thDay
28%13%5%8%7%35%445%12%
1683
16th to endDay
25%14%5%8%7%3443318%
1680
December1st to 15thDay
22%13%48%6%45%445%20%
1680
16th to endDay
29%15%5%9%7%3433415%
1792
January1st to 15thNight
25%12%5%9%6%2444418%
2926
16th to endNight
22%13%5%8%7%34445%21%
2963
February1st to 15thNight
18%14%6%9%8%36%43418%
2471
16th to endNight
19%13%5%9%7%35%435%22%
2187
March1st to 15thNight
23%14%5%8%7%35%345%18%
2198
16th to endNight
22%16%5%10%8%35%45%5%12%
2261
April1st to 15thNight
21%14%6%10%7%35%435%18%
1949
16th to endNight
17%11%46%5%345%5%8%27%
1778
May1st to 15thNight
12%8%47%43446%6%36%
1595
16th to endNight
14%6%26%5%46%6%6%9%31%
1624
June1st to 15thNight
14%7%5%7%6%2445%6%35%
1544
16th to endNight
8%8%35%42436%8%44%
1365
July1st to 15thNight
321432445%7%60%
1449
16th to endNight
3212212349%66%
1640
August1st to 15thNight
31221335%8%65%
1715
16th to endNight
5%31332245%7%59%
1934
September1st to 15thNight
5%213323347%64%
1950
16th to endNight
9%425%5%345%5%8%46%
2147
October1st to 15thNight
16%5%25%434446%41%
2340
16th to endNight
20%7%37%5%3445%5%32%
2519
November1st to 15thNight
26%10%47%7%46%45%5%17%
2834
16th to endNight
21%11%49%6%35%5%35%22%
2940
December1st to 15thNight
18%11%5%7%7%45%5%5%5%23%
2940
16th to endNight
26%15%5%10%7%3433315%
3136

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
33%13%5%7%6%3333217%
1672
16th to endDay
26%14%48%6%2333421%
1876
February1st to 15thDay
30%16%48%434335%13%
1711
16th to endDay
28%17%5%9%5%3333316%
1571
March1st to 15thDay
33%17%5%7%6%2433312%
2090
16th to endDay
33%16%48%8%35%3339%
2311
April1st to 15thDay
31%14%5%8%5%2445%5%13%
2329
16th to endDay
26%13%5%8%5%245%35%18%
2454
May1st to 15thDay
21%9%37%5%24445%30%
2685
16th to endDay
23%10%47%7%35%5%5%6%20%
2839
June1st to 15thDay
24%10%46%7%3445%5%23%
2742
16th to endDay
16%8%36%5%345%5%7%32%
2925
July1st to 15thDay
9%42342325%6%55%
2837
16th to endDay
8%313423447%56%
2881
August1st to 15thDay
8%5%2432345%7%52%
2494
16th to endDay
8%6%25%423346%51%
2619
September1st to 15thDay
8%5%2442335%6%53%
2340
16th to endDay
16%7%36%6%24446%37%
2139
October1st to 15thDay
22%7%46%5%335%45%30%
1950
16th to endDay
28%9%36%5%23335%27%
2057
November1st to 15thDay
32%11%48%7%35%44412%
1683
16th to endDay
29%12%5%8%5%35%43318%
1680
December1st to 15thDay
25%13%48%5%46%34419%
1680
16th to endDay
34%14%5%7%5%2333314%
1792
January1st to 15thNight
30%12%47%43434419%
2926
16th to endNight
28%11%47%6%33345%22%
2963
February1st to 15thNight
24%13%49%7%35%43418%
2471
16th to endNight
23%13%5%8%425%34423%
2187
March1st to 15thNight
28%12%48%6%34335%18%
2198
16th to endNight
26%13%5%8%7%45%45%5%13%
2265
April1st to 15thNight
24%14%5%8%6%45%345%19%
1949
16th to endNight
20%10%36%5%2346%7%28%
1778
May1st to 15thNight
14%8%36%5%35%45%6%37%
1595
16th to endNight
14%6%25%6%47%5%7%8%32%
1624
June1st to 15thNight
15%8%47%424347%36%
1544
16th to endNight
11%7%25%414347%45%
1365
July1st to 15thNight
421341345%6%62%
1449
16th to endNight
322212248%69%
1640
August1st to 15thNight
311221235%8%67%
1715
16th to endNight
6%313313347%60%
1934
September1st to 15thNight
5%313312345%65%
1950
16th to endNight
10%4245%2445%8%46%
2147
October1st to 15thNight
18%5%245%34346%42%
2340
16th to endNight
23%8%26%5%33346%33%
2519
November1st to 15thNight
30%9%38%6%34445%18%
2834
16th to endNight
26%10%48%6%2444422%
2940
December1st to 15thNight
23%11%47%5%35%45%5%23%
2940
16th to endNight
31%14%48%6%2433315%
3136

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
73%47%8%6%
1672
16th to endDay
67%5%7%9%6%2
1876
February1st to 15thDay
72%6%7%8%3
1711
16th to endDay
74%37%9%5%
1571
March1st to 15thDay
77%47%7%3
2090
16th to endDay
80%5%5%8%
2311
April1st to 15thDay
73%5%10%9%1
2329
16th to endDay
66%6%10%10%5%
2454
May1st to 15thDay
53%413%19%7%
2685
16th to endDay
61%9%12%13%2
2843
June1st to 15thDay
60%6%15%11%5%
2742
16th to endDay
48%8%16%18%6%1
2925
July1st to 15thDay
29%5%13%25%21%4
2684
16th to endDay
22%5%13%27%25%5%
2714
August1st to 15thDay
27%6%15%27%16%5%
2477
16th to endDay
31%6%12%27%18%3
2619
September1st to 15thDay
29%6%12%22%20%8%
2340
16th to endDay
46%6%14%16%13%3
2139
October1st to 15thDay
53%6%10%18%9%2
1950
16th to endDay
60%5%8%14%11%
2057
November1st to 15thDay
74%5%9%6%3
1683
16th to endDay
70%5%7%8%8%
1680
December1st to 15thDay
67%5%6%12%7%
1680
16th to endDay
75%5%8%7%3
1792
January1st to 15thNight
67%6%9%8%6%1
2926
16th to endNight
64%48%10%7%3
2963
February1st to 15thNight
67%7%8%11%4
2483
16th to endNight
62%8%10%12%6%
2187
March1st to 15thNight
68%5%9%13%3
2198
16th to endNight
70%7%11%8%2
2265
April1st to 15thNight
67%5%12%10%4
1949
16th to endNight
53%7%14%15%6%1
1778
May1st to 15thNight
44%5%17%21%9%1
1596
16th to endNight
44%12%18%18%4
1624
June1st to 15thNight
46%6%19%21%5%
1544
16th to endNight
36%6%21%26%7%2
1365
July1st to 15thNight
18%5%18%28%21%7%
1373
16th to endNight
13%314%32%26%10%
1544
August1st to 15thNight
14%5%20%34%19%6%
1707
16th to endNight
21%5%14%33%19%5%
1934
September1st to 15thNight
21%414%27%22%10%
1950
16th to endNight
32%7%16%21%16%5%
2147
October1st to 15thNight
42%411%23%14%3
2340
16th to endNight
52%6%10%16%12%1
2519
November1st to 15thNight
66%6%10%11%4
2834
16th to endNight
62%6%9%9%9%1
2940
December1st to 15thNight
61%6%9%12%8%
2940
16th to endNight
73%5%8%8%3
3136

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
30%5%21%18%20%3
120
16th to endDay
37%9%22%15%13%
236
February1st to 15thDay
41%12%22%14%7%1
281
16th to endDay
42%16%22%12%5%
259
March1st to 15thDay
43%15%21%15%4
330
16th to endDay
39%16%23%13%6%1
352
April1st to 15thDay
38%15%20%13%8%3
329
16th to endDay
33%11%27%16%7%2
318
May1st to 15thDay
23%18%23%21%10%2
348
16th to endDay
24%9%20%25%14%4
394
June1st to 15thDay
24%11%27%22%12%1
387
16th to endDay
12%13%37%26%8%1
570
July1st to 15thDay
10%7%30%36%11%3
468
16th to endDay
45%31%38%14%5%
391
August1st to 15thDay
8%5%25%34%17%8%
359
16th to endDay
6%8%25%33%19%6%
396
September1st to 15thDay
10%7%24%35%17%5%
375
16th to endDay
16%9%24%29%17%1
375
October1st to 15thDay
25%12%25%21%12%2
375
16th to endDay
33%7%21%16%14%7%
377
November1st to 15thDay
33%9%31%19%5%
130
16th to endDay
35%12%21%15%10%5%
120
December1st to 15thDay
35%10%20%22%8%3
120
16th to endDay
41%11%23%12%9%1
128
January1st to 15thNight
35%5%18%23%15%2
840
16th to endNight
30%5%17%25%18%2
881
February1st to 15thNight
29%7%20%25%15%1
764
16th to endNight
26%9%23%26%13%
684
March1st to 15thNight
32%9%18%24%13%1
780
16th to endNight
29%9%21%26%12%1
832
April1st to 15thNight
28%9%23%24%12%1
779
16th to endNight
24%5%19%35%14%
620
May1st to 15thNight
17%6%28%28%18%
426
16th to endNight
16%321%39%18%
407
June1st to 15thNight
15%427%41%10%
390
16th to endNight
13%429%40%12%
390
July1st to 15thNight
4126%52%14%
370
16th to endNight
3227%49%15%
408
August1st to 15thNight
316%45%31%2
561
16th to endNight
7%119%43%26%1
692
September1st to 15thNight
6%218%41%28%3
780
16th to endNight
12%317%40%23%2
776
October1st to 15thNight
19%419%32%21%2
780
16th to endNight
26%417%24%23%3
832
November1st to 15thNight
32%6%21%28%10%
820
16th to endNight
31%6%19%24%15%2
840
December1st to 15thNight
29%6%19%27%15%1
840
16th to endNight
36%9%22%19%10%1
896
Page generated at 2019-01-28 18:54:03. Version ac04

Copyright 2019 A. Danko


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