Bonavista
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bonavista clear sky chart from 2005-11-05 to 2017-10-06.

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
18%
14954
7%
47002
3%
14910
22%
14910
10%
37820

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
7%
750
4%
2679
1%
746
11%
746
5%
2276
January16th to endNight
9%
800
6%
2688
2%
800
14%
800
6%
2205
February1st to 15thNight
8%
733
6%
2341
0%
731
14%
731
7%
1898
February16th to endNight
7%
642
8%
1961
0%
642
13%
642
7%
1615
March1st to 15thNight
16%
651
8%
2091
3%
651
22%
651
10%
1645
March16th to endNight
16%
576
7%
2112
3%
576
22%
576
7%
1747
April1st to 15thNight
18%
539
10%
1712
5%
539
26%
539
10%
1361
April16th to endNight
15%
540
9%
1620
4%
540
21%
540
10%
1305
May1st to 15thNight
23%
540
6%
1541
1%
540
26%
540
11%
1263
May16th to endNight
22%
561
6%
1309
2%
560
24%
560
13%
1108
June1st to 15thNight
21%
540
2%
1260
0%
540
22%
540
11%
1088
June16th to endNight
25%
540
4%
1260
2%
540
26%
540
16%
1020
July1st to 15thNight
34%
510
5%
1190
3%
510
35%
510
22%
923
July16th to endNight
30%
565
6%
1327
2%
532
33%
532
17%
1054
August1st to 15thNight
30%
539
7%
1555
3%
535
32%
535
16%
1178
August16th to endNight
37%
573
10%
1719
8%
573
41%
573
18%
1233
September1st to 15thNight
31%
540
11%
1846
8%
540
38%
540
18%
1280
September16th to endNight
29%
538
13%
1980
11%
538
36%
538
14%
1399
October1st to 15thNight
24%
535
11%
1998
7%
535
31%
535
10%
1521
October16th to endNight
15%
712
7%
2264
3%
712
18%
712
7%
1889
November1st to 15thNight
17%
730
6%
2386
3%
730
20%
730
9%
1926
November16th to endNight
12%
750
7%
2583
1%
750
17%
750
7%
2072
December1st to 15thNight
10%
750
5%
2700
2%
750
13%
750
5%
2288
December16th to endNight
8%
800
2%
2880
0%
800
9%
800
3%
2526

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
22%12%47%6%34446%22%
48215
Night
24%13%5%8%6%34445%18%
47160
TransparencyDay
63%5%11%13%5%
47891
Night
66%411%12%5%
47002
SeeingDay
31%10%28%20%8%1
8308
Night
32%11%28%20%6%
14955

By Month

Percentage Cloud Cover NE (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
21%15%8%9%9%45%435%11%
1257
16th to endDay
20%16%5%13%10%5%5%345%9%
1536
February1st to 15thDay
21%12%310%11%5%5%45%6%13%
1518
16th to endDay
19%15%7%12%8%3424415%
1509
March1st to 15thDay
18%11%6%8%8%44445%21%
1858
16th to endDay
24%16%6%10%6%3423415%
2112
April1st to 15thDay
19%12%47%5%35%5%46%24%
2234
16th to endDay
26%12%46%423345%25%
2340
May1st to 15thDay
25%15%46%424345%22%
2408
16th to endDay
25%11%45%5%34447%22%
2805
June1st to 15thDay
26%14%5%9%5%24445%15%
2700
16th to endDay
22%12%35%5%34445%27%
2700
July1st to 15thDay
19%7%25%435%5%5%7%33%
2700
16th to endDay
20%9%36%7%35%5%6%7%24%
2749
August1st to 15thDay
24%10%35%5%2445%7%26%
2394
16th to endDay
20%10%26%6%3445%8%26%
2483
September1st to 15thDay
23%7%35%42445%7%30%
2113
16th to endDay
20%7%25%5%2345%7%34%
1980
October1st to 15thDay
27%10%36%6%23445%24%
1760
16th to endDay
29%18%36%43334417%
1606
November1st to 15thDay
22%16%5%8%6%3435%5%18%
1472
16th to endDay
23%15%6%8%6%35%335%17%
1377
December1st to 15thDay
21%16%9%8%7%35%5%5%412%
1260
16th to endDay
23%16%7%11%11%343449%
1344
January1st to 15thNight
23%15%6%11%10%44445%9%
2679
16th to endNight
19%14%6%13%9%46%345%12%
2688
February1st to 15thNight
19%14%5%12%10%33445%15%
2341
16th to endNight
22%16%7%10%6%3433416%
1961
March1st to 15thNight
19%11%6%9%7%45%45%7%17%
2079
16th to endNight
26%15%39%6%3433417%
2112
April1st to 15thNight
22%14%6%7%5%24445%21%
1712
16th to endNight
27%15%6%6%5%1322422%
1620
May1st to 15thNight
27%14%6%6%424446%18%
1541
16th to endNight
29%11%46%6%3445%7%17%
1307
June1st to 15thNight
32%13%46%41445%6%15%
1260
16th to endNight
27%11%36%5%23447%23%
1260
July1st to 15thNight
19%8%36%5%346%49%29%
1260
16th to endNight
22%9%45%5%25%5%47%25%
1418
August1st to 15thNight
25%9%36%43435%7%26%
1566
16th to endNight
20%8%35%5%235%5%8%30%
1719
September1st to 15thNight
23%7%25%43335%6%33%
1846
16th to endNight
21%10%35%5%25%45%7%28%
1980
October1st to 15thNight
27%9%37%5%34446%23%
1998
16th to endNight
32%16%36%5%3332417%
2264
November1st to 15thNight
24%18%46%5%35%346%17%
2386
16th to endNight
22%16%6%8%6%35%445%16%
2583
December1st to 15thNight
21%17%9%12%8%3433312%
2700
16th to endNight
23%18%8%11%10%342238%
2880

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
74%49%7%3
1258
16th to endDay
76%37%8%4
1536
February1st to 15thDay
67%5%12%10%3
1522
16th to endDay
72%48%9%5%
1509
March1st to 15thDay
64%49%13%7%
1869
16th to endDay
73%47%9%41
2112
April1st to 15thDay
61%5%9%13%7%
2234
16th to endDay
63%5%8%12%9%1
2340
May1st to 15thDay
65%5%9%14%4
2408
16th to endDay
64%5%10%13%5%
2809
June1st to 15thDay
72%49%9%2
2700
16th to endDay
60%5%11%15%6%
2700
July1st to 15thDay
50%7%14%19%7%
2542
16th to endDay
56%9%14%15%4
2577
August1st to 15thDay
59%7%12%15%4
2380
16th to endDay
55%8%15%16%3
2483
September1st to 15thDay
54%5%11%21%6%
2113
16th to endDay
49%6%18%17%7%
1980
October1st to 15thDay
63%5%11%12%7%
1760
16th to endDay
71%5%6%10%5%
1606
November1st to 15thDay
66%5%12%11%3
1472
16th to endDay
70%410%9%4
1377
December1st to 15thDay
70%6%9%10%3
1260
16th to endDay
76%5%8%6%3
1344
January1st to 15thNight
73%49%7%3
2679
16th to endNight
69%311%10%4
2688
February1st to 15thNight
68%311%10%4
2341
16th to endNight
70%310%11%3
1961
March1st to 15thNight
64%312%11%6%
2091
16th to endNight
71%46%11%5%1
2112
April1st to 15thNight
65%48%15%5%
1712
16th to endNight
67%36%12%8%
1620
May1st to 15thNight
67%410%12%4
1541
16th to endNight
66%5%10%10%5%
1309
June1st to 15thNight
71%49%9%4
1260
16th to endNight
60%6%10%13%7%
1260
July1st to 15thNight
52%6%15%18%5%
1190
16th to endNight
59%6%14%16%3
1327
August1st to 15thNight
57%5%16%15%5%
1555
16th to endNight
52%5%18%18%4
1719
September1st to 15thNight
51%5%16%20%7%
1846
16th to endNight
54%412%18%8%
1980
October1st to 15thNight
61%5%11%13%6%
1998
16th to endNight
72%38%10%4
2264
November1st to 15thNight
67%413%9%4
2386
16th to endNight
68%312%9%4
2583
December1st to 15thNight
74%39%9%2
2700
16th to endNight
79%38%5%2
2880

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
31%19%33%12%2
240
16th to endDay
24%18%37%15%3
256
February1st to 15thDay
28%19%31%15%4
236
16th to endDay
25%21%31%14%5%
212
March1st to 15thDay
25%16%32%17%7%
240
16th to endDay
31%17%28%16%5%
256
April1st to 15thDay
28%11%32%18%6%1
361
16th to endDay
37%9%26%19%5%1
450
May1st to 15thDay
34%8%22%19%11%2
468
16th to endDay
35%6%27%21%7%1
519
June1st to 15thDay
38%6%22%23%7%1
495
16th to endDay
31%430%20%8%4
495
July1st to 15thDay
26%5%27%26%10%2
475
16th to endDay
30%225%28%11%
514
August1st to 15thDay
30%426%25%11%1
493
16th to endDay
29%323%30%12%1
523
September1st to 15thDay
29%5%24%28%11%
352
16th to endDay
26%10%30%24%7%
269
October1st to 15thDay
31%11%30%14%10%1
243
16th to endDay
38%16%25%13%5%
240
November1st to 15thDay
31%14%29%17%6%
235
16th to endDay
37%13%32%13%2
240
December1st to 15thDay
31%16%34%12%5%
240
16th to endDay
29%23%28%12%5%
256
January1st to 15thNight
32%20%31%12%3
750
16th to endNight
27%22%33%13%2
800
February1st to 15thNight
27%19%33%15%3
734
16th to endNight
32%16%32%12%41
642
March1st to 15thNight
26%16%31%18%6%
651
16th to endNight
37%11%25%18%5%
576
April1st to 15thNight
31%7%32%19%6%1
539
16th to endNight
35%6%32%19%5%
540
May1st to 15thNight
36%225%25%7%1
540
16th to endNight
36%427%21%8%
561
June1st to 15thNight
40%322%24%7%1
540
16th to endNight
35%5%23%22%10%2
540
July1st to 15thNight
25%328%30%10%1
510
16th to endNight
27%430%27%9%
565
August1st to 15thNight
33%324%27%9%1
539
16th to endNight
24%326%31%12%1
573
September1st to 15thNight
26%432%27%9%
540
16th to endNight
27%7%30%28%5%
538
October1st to 15thNight
32%9%26%21%8%1
535
16th to endNight
44%10%23%16%4
712
November1st to 15thNight
33%13%28%18%6%
730
16th to endNight
32%16%30%16%4
750
December1st to 15thNight
32%18%30%14%4
750
16th to endNight
32%19%26%17%31
800
Page generated at 2017-10-07 15:37:48. Version ac04

Copyright 2017 A. Danko


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