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Monrovia
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Monrovia clear sky chart from 2005-11-05 to 2018-02-22.

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
74%
16496
34%
48750
29%
16450
78%
16450
52%
24045

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
62%
776
28%
2687
25%
776
70%
776
40%
1339
January16th to endNight
59%
832
35%
2516
27%
832
69%
832
41%
1344
February1st to 15thNight
68%
757
34%
2285
32%
756
74%
756
47%
1157
February16th to endNight
59%
660
29%
1979
27%
660
66%
660
37%
1122
March1st to 15thNight
64%
720
29%
2160
25%
720
73%
720
46%
1104
March16th to endNight
68%
768
28%
2010
22%
768
72%
768
48%
1114
April1st to 15thNight
63%
719
28%
1799
16%
719
68%
719
47%
1041
April16th to endNight
67%
720
30%
1800
15%
720
71%
720
55%
962
May1st to 15thNight
67%
611
28%
1691
19%
611
70%
611
47%
927
May16th to endNight
71%
561
29%
1685
23%
561
73%
561
51%
846
June1st to 15thNight
82%
482
29%
1562
27%
482
84%
482
55%
714
June16th to endNight
94%
360
38%
1440
46%
360
94%
360
65%
491
July1st to 15thNight
93%
340
34%
1360
41%
340
93%
340
60%
487
July16th to endNight
90%
633
31%
1654
25%
592
91%
592
60%
798
August1st to 15thNight
92%
717
35%
1790
23%
713
92%
713
74%
844
August16th to endNight
93%
764
42%
1910
29%
764
93%
764
76%
882
September1st to 15thNight
91%
720
39%
1833
31%
720
91%
720
69%
880
September16th to endNight
88%
716
45%
1980
43%
716
90%
716
75%
846
October1st to 15thNight
78%
720
35%
1986
32%
720
81%
720
57%
988
October16th to endNight
77%
768
40%
2337
42%
768
81%
768
53%
1117
November1st to 15thNight
74%
760
34%
2470
34%
760
81%
760
52%
1129
November16th to endNight
72%
780
37%
2535
37%
780
77%
780
50%
1196
December1st to 15thNight
64%
780
32%
2535
28%
780
73%
780
40%
1303
December16th to endNight
57%
832
33%
2746
28%
832
67%
832
39%
1414

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
4212213335%68%
49477
Night
4212213335%67%
48950
TransparencyDay
18%37%16%26%26%
49169
Night
19%37%16%25%26%
48758
SeeingDay
6%9%31%37%11%3
6462
Night
5%114%35%34%7%
16510

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
8%313412336%61%
1578
16th to endDay
10%314313345%59%
2054
February1st to 15thDay
7%223212346%63%
1901
16th to endDay
12%5%24323236%53%
1641
March1st to 15thDay
5%313224448%58%
1800
16th to endDay
5%21342446%8%56%
2211
April1st to 15thDay
6%31332435%8%58%
2149
16th to endDay
5%212213235%69%
2160
May1st to 15thDay
3313213346%65%
2258
16th to endDay
423224336%64%
2429
June1st to 15thDay
422214246%66%
2394
16th to endDay
111222284%
2520
July1st to 15thDay
111213335%74%
2520
16th to endDay
1111113346%73%
2393
August1st to 15thDay
111222383%
2160
16th to endDay
11233481%
2292
September1st to 15thDay
1111223481%
2127
16th to endDay
11111223381%
1980
October1st to 15thDay
5%111212235%70%
1971
16th to endDay
321221233472%
1887
November1st to 15thDay
3213313335%68%
1719
16th to endDay
5%312323346%64%
1755
December1st to 15thDay
6%21332335%9%58%
1755
16th to endDay
11%313223247%58%
1823
January1st to 15thNight
7%313223346%60%
2687
16th to endNight
9%323213235%61%
2516
February1st to 15thNight
6%323313235%64%
2281
16th to endNight
12%422323335%55%
1979
March1st to 15thNight
5%312214448%61%
2160
16th to endNight
421332435%7%61%
2010
April1st to 15thNight
6%412325%336%62%
1799
16th to endNight
3211124435%68%
1800
May1st to 15thNight
3212225%347%63%
1691
16th to endNight
2212225%336%67%
1684
June1st to 15thNight
111225%347%69%
1562
16th to endNight
11412482%
1440
July1st to 15thNight
11223235%76%
1440
16th to endNight
21111345%7%69%
1769
August1st to 15thNight
1112235%78%
1800
16th to endNight
1111123382%
1910
September1st to 15thNight
1112223478%
1833
16th to endNight
11223482%
1980
October1st to 15thNight
311332223471%
1986
16th to endNight
32221333471%
2337
November1st to 15thNight
3212313235%70%
2470
16th to endNight
5%21221335%6%65%
2535
December1st to 15thNight
6%214423347%60%
2535
16th to endNight
10%312212236%61%
2746

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
25%46%14%23%25%
1578
16th to endDay
27%47%15%18%26%
2054
February1st to 15thDay
22%36%15%24%27%
1901
16th to endDay
31%37%17%27%12%
1641
March1st to 15thDay
22%411%20%20%20%
1800
16th to endDay
22%6%13%22%20%14%
2211
April1st to 15thDay
23%412%24%23%11%
2149
16th to endDay
17%311%21%28%17%
2160
May1st to 15thDay
20%410%19%27%16%
2258
16th to endDay
21%49%25%28%10%
2432
June1st to 15thDay
21%38%14%30%21%
2394
16th to endDay
9%148%31%44%
2520
July1st to 15thDay
12%35%12%24%41%
2371
16th to endDay
12%48%21%30%23%
2245
August1st to 15thDay
7%2413%34%37%
2146
16th to endDay
8%25%12%38%33%
2292
September1st to 15thDay
9%25%12%32%37%
2127
16th to endDay
8%25%13%33%36%
1980
October1st to 15thDay
16%36%16%26%29%
1971
16th to endDay
15%4411%21%41%
1887
November1st to 15thDay
18%37%16%23%30%
1719
16th to endDay
21%46%12%22%32%
1755
December1st to 15thDay
22%6%9%17%18%26%
1755
16th to endDay
26%48%16%20%22%
1823
January1st to 15thNight
25%47%14%22%26%
2687
16th to endNight
26%47%15%17%28%
2516
February1st to 15thNight
22%38%16%22%26%
2292
16th to endNight
30%49%14%24%16%
1979
March1st to 15thNight
21%5%10%19%23%19%
2160
16th to endNight
22%5%11%22%22%15%
2010
April1st to 15thNight
25%39%24%21%14%
1799
16th to endNight
19%311%22%27%16%
1800
May1st to 15thNight
23%5%9%19%26%15%
1692
16th to endNight
19%410%26%28%11%
1685
June1st to 15thNight
16%311%16%30%20%
1562
16th to endNight
9%26%11%27%42%
1440
July1st to 15thNight
11%25%13%25%41%
1360
16th to endNight
14%39%21%26%23%
1654
August1st to 15thNight
9%2413%37%32%
1790
16th to endNight
7%26%12%36%33%
1910
September1st to 15thNight
11%35%10%32%36%
1833
16th to endNight
9%15%14%33%36%
1980
October1st to 15thNight
17%35%15%31%26%
1986
16th to endNight
18%3410%22%40%
2337
November1st to 15thNight
17%36%15%23%32%
2470
16th to endNight
20%38%15%19%33%
2535
December1st to 15thNight
25%48%14%18%27%
2535
16th to endNight
25%48%14%24%21%
2746

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
16%6%32%27%16%
116
16th to endDay
12%12%31%30%11%1
346
February1st to 15thDay
9%10%30%32%11%5%
326
16th to endDay
15%17%33%23%9%
264
March1st to 15thDay
8%15%33%23%16%1
270
16th to endDay
7%15%39%27%8%1
288
April1st to 15thDay
10%20%39%22%5%2
269
16th to endDay
421%44%23%32
270
May1st to 15thDay
10%15%36%27%6%2
288
16th to endDay
11%10%39%28%9%
330
June1st to 15thDay
6%9%33%38%8%2
315
16th to endDay
2229%47%10%7%
315
July1st to 15thDay
1122%51%16%5%
305
16th to endDay
218%54%14%9%
327
August1st to 15thDay
2123%57%8%5%
315
16th to endDay
22%55%14%6%
332
September1st to 15thDay
1234%48%8%3
315
16th to endDay
36%35%40%10%5%
315
October1st to 15thDay
5%10%36%34%10%2
315
16th to endDay
5%6%30%35%16%4
303
November1st to 15thDay
5%7%19%37%25%5%
135
16th to endDay
5%6%28%34%20%4
135
December1st to 15thDay
25%25%39%22%3
135
16th to endDay
11%9%24%32%18%4
133
January1st to 15thNight
9%220%43%21%3
780
16th to endNight
11%222%36%24%3
832
February1st to 15thNight
8%216%41%26%4
764
16th to endNight
14%219%36%22%3
660
March1st to 15thNight
5%224%39%23%4
720
16th to endNight
5%219%39%28%3
768
April1st to 15thNight
8%220%42%22%3
719
16th to endNight
4323%37%25%5%
720
May1st to 15thNight
6%320%36%28%4
612
16th to endNight
5%217%39%30%4
563
June1st to 15thNight
2112%44%36%3
482
16th to endNight
1235%55%5%
360
July1st to 15thNight
312%70%12%
340
16th to endNight
21223%56%13%
633
August1st to 15thNight
1325%54%14%
717
16th to endNight
1120%57%18%
764
September1st to 15thNight
2428%49%15%
720
16th to endNight
17%32%45%12%
716
October1st to 15thNight
412%39%38%5%
720
16th to endNight
5%112%33%34%12%
768
November1st to 15thNight
414%40%31%8%
760
16th to endNight
6%116%38%30%7%
780
December1st to 15thNight
8%218%40%26%3
780
16th to endNight
11%421%38%19%3
832
Page generated at 2018-02-23 08:21:34. Version ac04

Copyright 2018 A. Danko


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