Emerald Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Emerald Beach clear sky chart from 2005-11-05 to 2017-09-21.

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
49%
15284
23%
47032
15%
15240
57%
15240
27%
28121

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
29%
720
24%
2234
10%
716
43%
716
21%
1363
January16th to endNight
29%
768
25%
2304
12%
768
41%
768
22%
1482
February1st to 15thNight
32%
703
27%
2107
11%
699
46%
699
25%
1272
February16th to endNight
29%
631
23%
1893
9%
631
42%
631
23%
1214
March1st to 15thNight
34%
720
23%
2151
10%
720
45%
720
24%
1298
March16th to endNight
41%
714
25%
2058
14%
714
50%
714
29%
1202
April1st to 15thNight
45%
539
25%
1797
19%
539
54%
539
25%
1021
April16th to endNight
52%
540
30%
1800
22%
540
65%
540
34%
918
May1st to 15thNight
53%
539
23%
1721
17%
539
61%
539
33%
933
May16th to endNight
60%
561
23%
1682
16%
561
68%
561
30%
960
June1st to 15thNight
62%
540
14%
1620
12%
540
64%
540
26%
975
June16th to endNight
68%
540
16%
1620
15%
540
69%
540
30%
970
July1st to 15thNight
73%
510
12%
1530
11%
510
73%
510
28%
962
July16th to endNight
67%
564
10%
1747
12%
531
72%
531
25%
1079
August1st to 15thNight
73%
539
10%
1788
12%
536
74%
536
25%
1102
August16th to endNight
66%
573
14%
1910
17%
573
66%
573
22%
1249
September1st to 15thNight
62%
630
15%
1890
14%
630
64%
630
26%
1222
September16th to endNight
63%
681
25%
1881
16%
681
70%
681
28%
1193
October1st to 15thNight
59%
660
33%
1815
25%
660
66%
660
40%
1013
October16th to endNight
51%
704
33%
2032
24%
704
60%
704
37%
1158
November1st to 15thNight
47%
700
31%
2276
25%
700
59%
700
32%
1198
November16th to endNight
39%
720
28%
2340
17%
720
54%
720
28%
1294
December1st to 15thNight
37%
720
24%
2340
17%
720
47%
720
24%
1412
December16th to endNight
31%
768
19%
2496
11%
768
42%
768
18%
1631

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
8%424435%5%6%9%44%
47801
Night
9%42442446%8%47%
47249
TransparencyDay
34%8%14%19%15%6%
47514
Night
33%7%14%19%17%8%
47040
SeeingDay
10%11%15%22%23%16%
5226
Night
9%18%16%23%23%8%
15288

By Month

Percentage Cloud Cover SE (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
11%5%245%335%5%8%44%
1701
16th to endDay
15%6%25%424345%45%
1920
February1st to 15thDay
12%6%2342345%7%47%
1750
16th to endDay
13%43432335%7%47%
1580
March1st to 15thDay
9%5%2442446%8%47%
1806
16th to endDay
9%424424447%51%
2174
April1st to 15thDay
11%434334347%49%
2151
16th to endDay
5%4233245%5%7%55%
2160
May1st to 15thDay
6%3234245%5%8%53%
2226
16th to endDay
4314425%5%7%10%49%
2431
June1st to 15thDay
6%3245%36%6%8%11%39%
2340
16th to endDay
6%3245%36%7%7%12%39%
2340
July1st to 15thDay
6%325%6%47%7%10%14%29%
2340
16th to endDay
7%425%6%47%9%10%13%28%
2298
August1st to 15thDay
8%5%15%6%36%8%9%13%30%
2160
16th to endDay
10%5%25%5%35%6%7%9%37%
2292
September1st to 15thDay
9%5%15%5%25%5%8%9%39%
2058
16th to endDay
6%3145%36%7%7%10%43%
1872
October1st to 15thDay
5%41332345%8%57%
1815
16th to endDay
9%21432324459%
1837
November1st to 15thDay
8%5%12324447%55%
1582
16th to endDay
7%3235%2445%7%53%
1620
December1st to 15thDay
9%5%35%42345%7%48%
1620
16th to endDay
18%8%45%424346%36%
1728
January1st to 15thNight
11%6%25%32345%6%46%
2234
16th to endNight
16%7%24423445%43%
2304
February1st to 15thNight
12%6%23313345%51%
2103
16th to endNight
14%6%24433345%47%
1893
March1st to 15thNight
10%5%3343445%7%46%
2151
16th to endNight
8%424424347%52%
2058
April1st to 15thNight
9%5%2442446%6%49%
1797
16th to endNight
7%312323448%59%
1800
May1st to 15thNight
7%41432445%9%53%
1721
16th to endNight
5%3134245%6%9%52%
1682
June1st to 15thNight
4325%435%5%9%12%43%
1620
16th to endNight
6%323325%7%9%12%43%
1620
July1st to 15thNight
4224436%7%10%13%40%
1620
16th to endNight
5%2245%36%6%10%13%38%
1866
August1st to 15thNight
5%315%437%6%9%15%37%
1800
16th to endNight
8%5%245%45%5%7%11%38%
1910
September1st to 15thNight
8%4247%35%6%6%12%38%
1890
16th to endNight
6%5%244446%6%9%44%
1881
October1st to 15thNight
441432346%7%56%
1815
16th to endNight
8%5%24323445%55%
2032
November1st to 15thNight
7%414323347%55%
2276
16th to endNight
9%324423346%54%
2340
December1st to 15thNight
11%5%3442445%6%47%
2340
16th to endNight
16%6%26%5%2445%6%38%
2496

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
36%6%9%15%23%8%
1702
16th to endDay
41%5%6%15%22%9%
1920
February1st to 15thDay
37%49%17%21%9%
1752
16th to endDay
36%6%8%18%19%8%
1580
March1st to 15thDay
34%6%11%22%19%7%
1806
16th to endDay
33%6%14%20%17%8%
2175
April1st to 15thDay
35%5%8%21%20%7%
2151
16th to endDay
26%6%14%24%20%7%
2160
May1st to 15thDay
27%7%16%22%18%7%
2226
16th to endDay
28%10%16%24%17%2
2435
June1st to 15thDay
34%12%19%26%6%
2340
16th to endDay
34%11%22%21%8%1
2340
July1st to 15thDay
40%15%25%14%3
2201
16th to endDay
40%16%24%14%3
2154
August1st to 15thDay
39%16%24%15%4
2148
16th to endDay
40%11%23%16%6%2
2292
September1st to 15thDay
40%11%18%16%9%4
2058
16th to endDay
33%11%15%17%17%6%
1872
October1st to 15thDay
24%6%13%19%22%13%
1815
16th to endDay
28%46%14%27%18%
1837
November1st to 15thDay
29%48%19%26%11%
1582
16th to endDay
29%5%9%20%20%15%
1620
December1st to 15thDay
36%6%10%20%18%6%
1620
16th to endDay
48%5%7%20%13%5%
1728
January1st to 15thNight
36%5%9%13%25%8%
2234
16th to endNight
42%37%14%22%8%
2304
February1st to 15thNight
35%36%17%23%12%
2112
16th to endNight
40%48%12%21%12%
1893
March1st to 15thNight
35%5%11%18%21%6%
2151
16th to endNight
31%49%24%18%11%
2058
April1st to 15thNight
33%411%18%21%10%
1797
16th to endNight
24%5%10%30%22%7%
1800
May1st to 15thNight
27%5%14%21%22%8%
1722
16th to endNight
25%9%17%24%18%4
1684
June1st to 15thNight
28%11%23%23%11%
1620
16th to endNight
28%11%26%23%9%1
1620
July1st to 15thNight
28%14%30%19%5%
1530
16th to endNight
30%14%32%18%4
1747
August1st to 15thNight
30%13%33%17%3
1788
16th to endNight
38%11%22%18%6%2
1910
September1st to 15thNight
35%10%21%16%12%3
1890
16th to endNight
33%9%14%19%18%5%
1881
October1st to 15thNight
25%5%9%22%21%15%
1815
16th to endNight
30%36%13%25%20%
2032
November1st to 15thNight
28%37%20%26%14%
2276
16th to endNight
31%48%17%21%16%
2340
December1st to 15thNight
37%410%20%20%6%
2340
16th to endNight
43%6%10%18%14%6%
2496

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
15%15%35%21%11%1
90
16th to endDay
19%21%38%13%6%
96
February1st to 15thDay
10%17%35%22%14%
90
16th to endDay
13%14%38%29%3
81
March1st to 15thDay
13%18%48%13%5%
96
16th to endDay
13%19%23%25%15%3
288
April1st to 15thDay
12%18%23%22%18%3
270
16th to endDay
5%17%25%22%23%5%
270
May1st to 15thDay
9%15%17%26%22%9%
288
16th to endDay
8%12%13%27%18%19%
331
June1st to 15thDay
11%10%6%26%22%22%
315
16th to endDay
10%11%421%24%27%
315
July1st to 15thDay
46%113%33%40%
305
16th to endDay
7%10%319%31%29%
326
August1st to 15thDay
11%6%317%30%31%
313
16th to endDay
9%7%417%32%29%
332
September1st to 15thDay
13%6%8%19%30%21%
315
16th to endDay
10%6%7%30%31%13%
275
October1st to 15thDay
7%10%13%32%25%10%
255
16th to endDay
9%10%22%25%21%11%
209
November1st to 15thDay
23%23%28%21%3
90
16th to endDay
6%8%40%33%6%4
90
December1st to 15thDay
13%16%36%24%7%1
90
16th to endDay
32%9%23%22%11%
96
January1st to 15thNight
13%26%27%24%7%
720
16th to endNight
13%27%25%24%8%
768
February1st to 15thNight
14%25%24%24%9%1
704
16th to endNight
15%23%27%25%7%
631
March1st to 15thNight
12%24%25%25%10%1
720
16th to endNight
9%23%22%27%14%2
714
April1st to 15thNight
11%21%17%30%18%
539
16th to endNight
8%19%16%26%24%4
540
May1st to 15thNight
9%18%14%27%25%4
540
16th to endNight
7%18%7%22%35%9%
563
June1st to 15thNight
5%17%418%39%14%
540
16th to endNight
5%17%111%42%21%
540
July1st to 15thNight
212%110%41%31%
510
16th to endNight
416%111%38%27%
564
August1st to 15thNight
5%9%28%44%30%
539
16th to endNight
9%9%313%39%23%
573
September1st to 15thNight
8%9%6%17%39%19%
630
16th to endNight
10%9%8%27%36%7%
681
October1st to 15thNight
5%10%16%32%30%4
660
16th to endNight
9%12%20%25%27%3
704
November1st to 15thNight
9%18%19%32%18%2
700
16th to endNight
10%21%24%26%16%1
720
December1st to 15thNight
11%22%24%23%16%2
720
16th to endNight
16%23%24%24%11%
768
Page generated at 2017-09-22 07:35:36. Version ac04

Copyright 2017 A. Danko


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