Merced
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Merced clear sky chart from 2005-11-05 to 2018-01-12.

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
69%
15856
31%
48365
27%
15818
74%
15818
49%
24057

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
65%
761
19%
2609
21%
760
66%
760
31%
1498
January16th to endNight
66%
768
24%
2496
28%
768
67%
768
30%
1473
February1st to 15thNight
63%
698
26%
2214
28%
698
66%
698
35%
1260
February16th to endNight
58%
632
26%
1895
25%
632
63%
632
34%
1122
March1st to 15thNight
60%
720
21%
2082
20%
720
64%
720
35%
1242
March16th to endNight
56%
768
24%
2038
17%
768
62%
768
42%
1171
April1st to 15thNight
52%
719
26%
1799
11%
719
59%
719
44%
1056
April16th to endNight
57%
720
29%
1800
11%
720
64%
720
55%
956
May1st to 15thNight
63%
653
31%
1733
17%
653
69%
653
64%
827
May16th to endNight
59%
375
35%
1496
28%
374
74%
374
53%
558
June1st to 15thNight
58%
360
32%
1440
27%
360
74%
360
57%
517
June16th to endNight
73%
360
40%
1440
43%
360
84%
360
77%
430
July1st to 15thNight
82%
340
36%
1360
41%
340
89%
340
75%
420
July16th to endNight
83%
514
38%
1543
34%
481
86%
481
66%
631
August1st to 15thNight
83%
628
39%
1701
24%
625
87%
625
83%
704
August16th to endNight
89%
764
46%
1910
28%
764
90%
764
86%
836
September1st to 15thNight
86%
720
43%
1800
29%
720
90%
720
81%
809
September16th to endNight
80%
716
49%
1925
40%
716
86%
716
79%
826
October1st to 15thNight
73%
720
33%
2157
31%
720
81%
720
60%
962
October16th to endNight
79%
768
42%
2304
45%
768
82%
768
61%
1021
November1st to 15thNight
74%
760
31%
2443
33%
760
77%
760
48%
1179
November16th to endNight
70%
780
28%
2538
29%
780
73%
780
40%
1322
December1st to 15thNight
67%
780
23%
2730
25%
780
71%
780
32%
1526
December16th to endNight
57%
832
23%
2912
23%
832
63%
832
27%
1711

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
6%312212235%67%
48963
Night
7%212212235%65%
48556
TransparencyDay
20%28%20%25%22%
48646
Night
21%39%20%24%20%
48372
SeeingDay
7%416%30%28%13%
6258
Night
8%215%39%28%5%
15866

By Month

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
14%6%26%5%23447%43%
1571
16th to endDay
16%7%35%5%34445%39%
1728
February1st to 15thDay
15%6%33313447%46%
1642
16th to endDay
15%5%24423337%46%
1579
March1st to 15thDay
11%32332446%8%48%
1875
16th to endDay
10%3233235%6%7%50%
2184
April1st to 15thDay
10%42431345%5%54%
2149
16th to endDay
6%213222226%66%
2160
May1st to 15thDay
1112211335%75%
2211
16th to endDay
322212336%70%
2615
June1st to 15thDay
221121122476%
2520
16th to endDay
11111288%
2520
July1st to 15thDay
112387%
2520
16th to endDay
11111112382%
2516
August1st to 15thDay
1112288%
2249
16th to endDay
1112387%
2292
September1st to 15thDay
11112287%
2160
16th to endDay
1111112484%
2034
October1st to 15thDay
311212236%74%
1800
16th to endDay
423222346%67%
1920
November1st to 15thDay
5%313334335%60%
1743
16th to endDay
10%5%2342335%7%50%
1751
December1st to 15thDay
13%5%25%5%24446%45%
1560
16th to endDay
16%7%245%24347%42%
1664
January1st to 15thNight
13%5%1331335%7%49%
2609
16th to endNight
15%413323337%49%
2496
February1st to 15thNight
13%414323347%51%
2209
16th to endNight
16%413323446%50%
1895
March1st to 15thNight
11%414424346%52%
2082
16th to endNight
10%313214347%56%
2038
April1st to 15thNight
9%3133235%5%7%55%
1799
16th to endNight
412313346%68%
1800
May1st to 15thNight
221112235%75%
1733
16th to endNight
4111211235%74%
1496
June1st to 15thNight
211112225%77%
1440
16th to endNight
111289%
1440
July1st to 15thNight
11211287%
1440
16th to endNight
21121212381%
1650
August1st to 15thNight
112288%
1710
16th to endNight
111387%
1910
September1st to 15thNight
11111288%
1800
16th to endNight
111111384%
1925
October1st to 15thNight
32211233473%
2157
16th to endNight
411111235%74%
2304
November1st to 15thNight
7%312212236%64%
2443
16th to endNight
8%32332345%6%57%
2538
December1st to 15thNight
12%423323247%51%
2730
16th to endNight
16%423323446%47%
2912

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
41%5%13%19%16%2
1571
16th to endDay
46%49%20%14%4
1728
February1st to 15thDay
38%412%26%15%3
1642
16th to endDay
39%312%26%17%
1579
March1st to 15thDay
32%5%15%25%18%3
1875
16th to endDay
31%416%24%19%2
2184
April1st to 15thDay
30%411%28%18%6%
2149
16th to endDay
21%311%26%28%8%
2160
May1st to 15thDay
13%27%25%36%13%
2211
16th to endDay
15%37%30%29%13%
2619
June1st to 15thDay
12%27%22%28%26%
2520
16th to endDay
6%111%32%47%
2520
July1st to 15thDay
4116%21%64%
2371
16th to endDay
8%238%21%56%
2360
August1st to 15thDay
5%118%28%54%
2233
16th to endDay
4118%36%47%
2292
September1st to 15thDay
6%1111%32%46%
2160
16th to endDay
7%1222%39%25%
2034
October1st to 15thDay
13%25%24%26%26%
1800
16th to endDay
18%37%25%28%17%
1920
November1st to 15thDay
27%313%29%23%2
1743
16th to endDay
33%314%26%19%2
1751
December1st to 15thDay
40%412%17%20%4
1560
16th to endDay
42%314%21%14%2
1664
January1st to 15thNight
34%413%24%17%4
2609
16th to endNight
35%412%17%18%11%
2496
February1st to 15thNight
33%312%27%18%5%
2220
16th to endNight
35%310%29%19%2
1895
March1st to 15thNight
33%413%21%21%6%
2082
16th to endNight
28%316%24%19%7%
2038
April1st to 15thNight
27%415%28%18%5%
1799
16th to endNight
17%5%15%23%28%10%
1800
May1st to 15thNight
13%27%23%36%16%
1734
16th to endNight
14%18%29%33%11%
1496
June1st to 15thNight
11%38%20%29%26%
1440
16th to endNight
5%210%27%53%
1440
July1st to 15thNight
6%11420%65%
1360
16th to endNight
12%125%20%58%
1543
August1st to 15thNight
6%110%27%54%
1701
16th to endNight
5%19%31%51%
1910
September1st to 15thNight
7%1210%29%49%
1800
16th to endNight
7%1218%41%28%
1925
October1st to 15thNight
14%27%22%24%28%
2157
16th to endNight
14%26%23%31%21%
2304
November1st to 15thNight
22%211%28%27%6%
2443
16th to endNight
26%410%26%26%5%
2538
December1st to 15thNight
33%412%21%20%8%
2730
16th to endNight
37%413%22%16%4
2912

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%315%24%18%11%
133
16th to endDay
17%5%14%22%19%21%
256
February1st to 15thDay
18%416%19%19%20%
248
16th to endDay
18%5%21%26%18%10%
238
March1st to 15thDay
13%5%20%25%21%14%
270
16th to endDay
12%10%20%26%22%8%
288
April1st to 15thDay
15%7%30%23%14%8%
269
16th to endDay
9%10%27%29%16%7%
270
May1st to 15thDay
47%24%33%23%6%
288
16th to endDay
48%17%31%27%10%
330
June1st to 15thDay
4326%35%22%7%
315
16th to endDay
1111%37%35%12%
315
July1st to 15thDay
8%32%41%16%
305
16th to endDay
5%36%41%15%
327
August1st to 15thDay
111%43%33%8%
315
16th to endDay
8%33%40%17%
332
September1st to 15thDay
27%36%39%13%
315
16th to endDay
1214%32%33%15%
315
October1st to 15thDay
2322%32%25%13%
315
16th to endDay
5%5%11%26%30%19%
336
November1st to 15thDay
6%111%22%31%25%
159
16th to endDay
7%417%32%27%10%
133
December1st to 15thDay
12%314%31%22%16%
90
16th to endDay
14%28%25%36%13%
96
January1st to 15thNight
15%19%33%31%8%
764
16th to endNight
17%19%33%28%9%
768
February1st to 15thNight
15%112%33%29%7%
704
16th to endNight
16%315%37%22%4
632
March1st to 15thNight
11%315%36%27%5%
720
16th to endNight
11%223%34%24%1
768
April1st to 15thNight
10%5%26%34%20%1
719
16th to endNight
5%428%35%22%3
720
May1st to 15thNight
3328%42%20%2
654
16th to endNight
5%428%42%18%
375
June1st to 15thNight
2433%47%11%
360
16th to endNight
123%56%17%
360
July1st to 15thNight
15%62%21%
340
16th to endNight
110%49%37%1
514
August1st to 15thNight
112%53%29%2
628
16th to endNight
8%49%38%2
764
September1st to 15thNight
19%44%42%2
720
16th to endNight
215%40%34%6%
716
October1st to 15thNight
5%215%37%32%7%
720
16th to endNight
5%19%32%36%13%
768
November1st to 15thNight
8%19%38%32%8%
760
16th to endNight
10%110%37%30%8%
780
December1st to 15thNight
15%17%41%27%6%
780
16th to endNight
17%213%35%26%4
832
Page generated at 2018-01-12 19:01:32. Version ac04

Copyright 2018 A. Danko


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