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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 2019-07-11.

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
73%
18279
33%
54015
28%
18233
78%
18233
51%
26884

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%
836
28%
2895
25%
836
70%
836
38%
1471
January16th to endNight
59%
896
33%
2710
26%
896
69%
896
41%
1462
February1st to 15thNight
66%
817
35%
2465
32%
816
73%
816
45%
1276
February16th to endNight
58%
736
27%
2207
26%
736
65%
736
38%
1245
March1st to 15thNight
61%
840
27%
2520
23%
840
69%
840
41%
1367
March16th to endNight
68%
896
28%
2344
22%
896
72%
896
47%
1315
April1st to 15thNight
64%
839
29%
2099
17%
839
69%
839
46%
1230
April16th to endNight
67%
832
29%
2080
15%
832
72%
832
54%
1122
May1st to 15thNight
66%
713
27%
1973
19%
713
69%
713
44%
1115
May16th to endNight
68%
657
29%
1973
23%
657
70%
657
49%
1014
June1st to 15thNight
84%
562
31%
1822
29%
562
85%
562
57%
813
June16th to endNight
93%
420
36%
1680
44%
420
93%
420
61%
599
July1st to 15thNight
93%
392
36%
1568
43%
392
93%
392
58%
573
July16th to endNight
91%
686
30%
1803
24%
645
91%
645
62%
859
August1st to 15thNight
92%
765
37%
1910
24%
761
92%
761
75%
894
August16th to endNight
93%
828
40%
2070
28%
828
93%
828
75%
962
September1st to 15thNight
90%
780
40%
1986
33%
780
90%
780
69%
953
September16th to endNight
89%
776
44%
2145
42%
776
91%
776
76%
907
October1st to 15thNight
76%
780
36%
2151
33%
780
80%
780
56%
1085
October16th to endNight
78%
832
39%
2532
40%
832
82%
832
54%
1193
November1st to 15thNight
75%
820
37%
2665
37%
820
82%
820
54%
1195
November16th to endNight
72%
840
35%
2730
35%
840
77%
840
48%
1313
December1st to 15thNight
64%
840
33%
2730
29%
840
72%
840
40%
1411
December16th to endNight
58%
896
33%
2957
28%
896
68%
896
39%
1510

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%67%
55159
Night
4212213346%66%
54215
TransparencyDay
18%38%17%26%25%
54851
Night
20%38%16%25%25%
54023
SeeingDay
7%8%30%36%12%4
8351
Night
6%114%35%34%7%
18293

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%314413336%59%
1700
16th to endDay
10%314323335%58%
2212
February1st to 15thDay
9%223212346%60%
2051
16th to endDay
11%5%24323236%54%
1839
March1st to 15thDay
6%314324447%55%
2100
16th to endDay
5%21343446%8%55%
2579
April1st to 15thDay
5%31332335%8%58%
2509
16th to endDay
5%212213335%67%
2485
May1st to 15thDay
5%324313346%61%
2636
16th to endDay
5%314324346%61%
2845
June1st to 15thDay
412214336%68%
2792
16th to endDay
111222381%
2940
July1st to 15thDay
111213345%73%
2874
16th to endDay
1111113346%74%
2595
August1st to 15thDay
111212384%
2293
16th to endDay
11133480%
2484
September1st to 15thDay
111123381%
2304
16th to endDay
1111123381%
2145
October1st to 15thDay
5%212222235%68%
2135
16th to endDay
311221223473%
2044
November1st to 15thDay
3213213335%69%
1854
16th to endDay
5%212323346%63%
1890
December1st to 15thDay
7%21322335%9%58%
1890
16th to endDay
10%313223347%58%
1963
January1st to 15thNight
7%313323346%59%
2895
16th to endNight
9%323213335%60%
2710
February1st to 15thNight
7%323313235%63%
2461
16th to endNight
11%422323335%55%
2207
March1st to 15thNight
6%313324448%56%
2520
16th to endNight
421332435%7%59%
2344
April1st to 15thNight
5%412225%446%59%
2099
16th to endNight
32122245%46%66%
2080
May1st to 15thNight
3323325%347%60%
1973
16th to endNight
2312225%336%65%
1972
June1st to 15thNight
11125%447%70%
1822
16th to endNight
111423478%
1680
July1st to 15thNight
11223335%75%
1648
16th to endNight
21111345%8%69%
1918
August1st to 15thNight
1112235%79%
1920
16th to endNight
11111134480%
2070
September1st to 15thNight
1112233477%
1986
16th to endNight
11223482%
2145
October1st to 15thNight
3113312245%69%
2151
16th to endNight
32221333472%
2532
November1st to 15thNight
3212213235%71%
2665
16th to endNight
5%21221335%6%63%
2730
December1st to 15thNight
6%314423347%59%
2730
16th to endNight
9%313212236%62%
2957

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
27%46%13%22%25%
1700
16th to endDay
28%47%15%19%25%
2212
February1st to 15thDay
25%45%15%24%25%
2051
16th to endDay
30%38%17%27%12%
1839
March1st to 15thDay
26%5%10%19%18%19%
2100
16th to endDay
24%6%12%21%20%14%
2579
April1st to 15thDay
23%5%12%24%22%11%
2509
16th to endDay
19%310%21%28%16%
2485
May1st to 15thDay
24%410%19%26%14%
2636
16th to endDay
23%410%25%27%9%
2848
June1st to 15thDay
19%39%16%31%20%
2792
16th to endDay
10%1410%30%42%
2940
July1st to 15thDay
12%36%13%25%38%
2725
16th to endDay
11%49%22%29%21%
2447
August1st to 15thDay
7%2413%34%38%
2279
16th to endDay
8%25%13%39%30%
2484
September1st to 15thDay
8%25%12%33%37%
2304
16th to endDay
7%15%14%34%35%
2145
October1st to 15thDay
18%36%17%26%27%
2135
16th to endDay
14%4411%23%41%
2044
November1st to 15thDay
17%37%16%23%32%
1854
16th to endDay
21%47%14%21%30%
1890
December1st to 15thDay
23%6%8%18%18%24%
1890
16th to endDay
26%5%8%17%20%21%
1963
January1st to 15thNight
26%47%14%21%25%
2895
16th to endNight
26%47%14%17%28%
2710
February1st to 15thNight
23%38%16%22%25%
2472
16th to endNight
29%48%15%24%16%
2207
March1st to 15thNight
26%5%10%18%21%17%
2520
16th to endNight
23%5%11%21%22%14%
2344
April1st to 15thNight
25%49%24%20%14%
2099
16th to endNight
19%310%22%28%14%
2080
May1st to 15thNight
25%5%9%19%25%14%
1974
16th to endNight
21%410%27%26%10%
1973
June1st to 15thNight
15%312%17%30%20%
1822
16th to endNight
11%16%13%27%39%
1680
July1st to 15thNight
12%25%13%25%39%
1568
16th to endNight
14%311%22%25%22%
1803
August1st to 15thNight
8%2413%36%34%
1910
16th to endNight
8%26%13%37%31%
2070
September1st to 15thNight
11%36%10%32%36%
1986
16th to endNight
8%15%14%33%36%
2145
October1st to 15thNight
18%36%16%30%24%
2151
16th to endNight
17%3411%22%41%
2532
November1st to 15thNight
16%36%15%24%33%
2665
16th to endNight
21%38%17%19%30%
2730
December1st to 15thNight
26%49%15%18%25%
2730
16th to endNight
25%48%14%25%20%
2957

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%7%31%29%14%1
148
16th to endDay
12%11%32%29%12%1
408
February1st to 15thDay
15%10%28%30%10%4
386
16th to endDay
14%16%33%26%9%
342
March1st to 15thDay
13%16%34%22%12%1
390
16th to endDay
9%12%37%28%9%1
416
April1st to 15thDay
8%17%38%25%8%2
389
16th to endDay
6%19%40%23%6%2
378
May1st to 15thDay
14%12%33%27%8%3
408
16th to endDay
13%12%37%26%8%1
458
June1st to 15thDay
5%7%29%40%12%4
435
16th to endDay
3227%48%11%7%
435
July1st to 15thDay
119%49%19%7%
406
16th to endDay
217%51%17%10%
391
August1st to 15thDay
2121%55%11%7%
359
16th to endDay
120%52%17%7%
396
September1st to 15thDay
1233%46%11%4
375
16th to endDay
25%32%41%12%5%
375
October1st to 15thDay
6%12%35%33%10%1
375
16th to endDay
46%28%35%19%4
364
November1st to 15thDay
35%21%41%23%4
180
16th to endDay
5%6%27%35%20%5%
180
December1st to 15thDay
5%5%27%40%19%2
180
16th to endDay
9%9%24%33%19%3
177
January1st to 15thNight
10%219%42%21%3
840
16th to endNight
12%222%36%23%3
896
February1st to 15thNight
9%217%41%25%4
824
16th to endNight
14%220%37%21%3
736
March1st to 15thNight
7%224%39%21%4
840
16th to endNight
6%219%41%27%3
896
April1st to 15thNight
8%320%40%24%2
839
16th to endNight
4321%38%26%5%
832
May1st to 15thNight
8%218%35%29%5%
714
16th to endNight
6%219%39%28%3
659
June1st to 15thNight
111%42%39%3
562
16th to endNight
2233%54%6%
420
July1st to 15thNight
312%69%13%
392
16th to endNight
11224%56%13%
686
August1st to 15thNight
1324%54%15%
765
16th to endNight
1121%56%18%
828
September1st to 15thNight
25%28%48%15%
780
16th to endNight
16%32%46%12%
776
October1st to 15thNight
5%12%40%36%4
780
16th to endNight
5%112%33%35%12%
832
November1st to 15thNight
413%42%31%7%
820
16th to endNight
7%115%37%30%8%
840
December1st to 15thNight
9%218%41%25%3
840
16th to endNight
10%421%39%19%3
896
Page generated at 2019-07-12 04:32:35. Version ac04

Copyright 2019 A. Danko


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