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Prescott
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Prescott clear sky chart from 2005-11-05 to 2017-09-10.

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
71%
15652
35%
46844
29%
15613
77%
15613
52%
22573

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%
719
32%
2327
29%
716
73%
716
46%
1126
January16th to endNight
61%
768
35%
2496
33%
768
70%
768
41%
1288
February1st to 15thNight
65%
698
35%
2172
29%
698
76%
698
50%
1027
February16th to endNight
60%
632
35%
1895
32%
632
68%
632
44%
992
March1st to 15thNight
62%
720
37%
2000
28%
720
71%
720
51%
1010
March16th to endNight
65%
768
35%
2112
25%
768
73%
768
55%
1042
April1st to 15thNight
57%
719
29%
1978
16%
719
67%
719
51%
1021
April16th to endNight
59%
543
44%
1642
27%
543
74%
543
67%
665
May1st to 15thNight
70%
539
36%
1619
28%
539
76%
539
58%
719
May16th to endNight
72%
561
38%
1684
28%
561
78%
561
66%
699
June1st to 15thNight
77%
540
33%
1620
29%
540
78%
540
67%
681
June16th to endNight
84%
540
34%
1620
31%
540
86%
540
72%
659
July1st to 15thNight
85%
510
24%
1530
21%
510
85%
510
47%
782
July16th to endNight
81%
564
22%
1593
18%
531
83%
531
38%
909
August1st to 15thNight
88%
539
30%
1611
26%
536
89%
536
50%
799
August16th to endNight
84%
664
33%
1855
28%
664
84%
664
45%
1014
September1st to 15thNight
81%
700
30%
1925
25%
700
83%
700
50%
1033
September16th to endNight
80%
656
43%
1815
33%
656
86%
656
72%
795
October1st to 15thNight
73%
660
39%
1875
31%
660
79%
660
60%
874
October16th to endNight
79%
704
42%
2112
37%
704
84%
704
62%
936
November1st to 15thNight
74%
700
38%
2187
33%
700
81%
700
56%
981
November16th to endNight
70%
720
39%
2340
36%
720
78%
720
55%
1031
December1st to 15thNight
69%
720
35%
2340
32%
720
76%
720
45%
1146
December16th to endNight
61%
768
33%
2496
30%
768
67%
768
36%
1344

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
3313323446%62%
47781
Night
2213323346%66%
47040
TransparencyDay
22%35%15%27%25%
47476
Night
18%36%16%28%26%
46846
SeeingDay
5%10%22%32%21%8%
5457
Night
3314%33%35%8%
15662

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
3423423345%62%
1611
16th to endDay
6%5%23323346%57%
1728
February1st to 15thDay
36%33324336%59%
1688
16th to endDay
46%25%423447%53%
1579
March1st to 15thDay
2323323445%62%
1959
16th to endDay
331332344464%
2112
April1st to 15thDay
2313423346%63%
1970
16th to endDay
1212212336%70%
2315
May1st to 15thDay
3213223335%68%
2331
16th to endDay
321221333471%
2429
June1st to 15thDay
1111212235%77%
2340
16th to endDay
11111222380%
2340
July1st to 15thDay
3214436%6%6%7%53%
2340
16th to endDay
6%436%7%5%6%7%8%8%35%
2467
August1st to 15thDay
5%4245%36%5%6%8%46%
2340
16th to endDay
5%324425%5%6%7%51%
2343
September1st to 15thDay
5%3145%345%5%6%53%
1922
16th to endDay
211222234472%
1815
October1st to 15thDay
221222333471%
1755
16th to endDay
212212336%71%
1760
November1st to 15thDay
1112324345%69%
1669
16th to endDay
4312212245%69%
1620
December1st to 15thDay
47%23423437%57%
1620
16th to endDay
5%6%35%42346%6%51%
1728
January1st to 15thNight
3324413345%63%
2327
16th to endNight
5%5%24423345%60%
2496
February1st to 15thNight
3413312345%65%
2161
16th to endNight
332442445%7%57%
1895
March1st to 15thNight
341231335%5%64%
2000
16th to endNight
2222223346%66%
2112
April1st to 15thNight
322332334465%
1978
16th to endNight
11221224477%
1642
May1st to 15thNight
222213235%73%
1619
16th to endNight
21121123478%
1684
June1st to 15thNight
111121213478%
1620
16th to endNight
1221212281%
1620
July1st to 15thNight
21134345%6%7%58%
1620
16th to endNight
32145%47%6%8%12%42%
1701
August1st to 15thNight
2123335%6%10%58%
1620
16th to endNight
22134345%7%8%56%
1855
September1st to 15thNight
22144245%6%6%59%
1925
16th to endNight
21111113479%
1815
October1st to 15thNight
2212212345%71%
1875
16th to endNight
1212212225%75%
2112
November1st to 15thNight
2212223335%70%
2187
16th to endNight
3212212235%70%
2340
December1st to 15thNight
331232445%5%60%
2340
16th to endNight
5%5%24424445%55%
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
23%16%15%33%19%
1612
16th to endDay
26%36%18%28%16%
1728
February1st to 15thDay
26%16%18%24%22%
1688
16th to endDay
28%35%18%28%15%
1579
March1st to 15thDay
22%2215%35%20%
1959
16th to endDay
21%3417%35%17%
2112
April1st to 15thDay
20%2418%33%20%
1970
16th to endDay
15%2315%34%28%
2315
May1st to 15thDay
17%2416%31%27%
2331
16th to endDay
16%2411%34%30%
2432
June1st to 15thDay
11%127%26%51%
2340
16th to endDay
10%126%19%60%
2340
July1st to 15thDay
26%7%8%14%16%26%
2201
16th to endDay
38%10%15%14%15%5%
2312
August1st to 15thDay
30%6%9%16%18%18%
2325
16th to endDay
29%6%9%16%24%13%
2343
September1st to 15thDay
27%5%10%15%22%19%
1922
16th to endDay
14%2411%32%34%
1815
October1st to 15thDay
17%2415%28%32%
1755
16th to endDay
14%25%12%34%31%
1760
November1st to 15thDay
16%2418%32%25%
1669
16th to endDay
18%1318%28%28%
1620
December1st to 15thDay
27%28%22%25%14%
1620
16th to endDay
30%28%20%27%10%
1728
January1st to 15thNight
22%26%15%33%18%
2327
16th to endNight
27%2416%29%19%
2496
February1st to 15thNight
19%27%19%27%23%
2172
16th to endNight
24%35%19%29%17%
1895
March1st to 15thNight
19%3413%35%22%
2000
16th to endNight
17%27%18%33%19%
2112
April1st to 15thNight
20%25%14%35%21%
1978
16th to endNight
9%15%13%35%33%
1642
May1st to 15thNight
14%2415%30%32%
1620
16th to endNight
11%1211%39%33%
1685
June1st to 15thNight
12%116%23%55%
1620
16th to endNight
10%11415%65%
1620
July1st to 15thNight
20%6%11%14%18%28%
1530
16th to endNight
26%9%17%21%18%7%
1593
August1st to 15thNight
18%6%12%19%21%21%
1611
16th to endNight
22%6%9%20%24%15%
1855
September1st to 15thNight
21%5%11%18%20%22%
1925
16th to endNight
9%2310%37%36%
1815
October1st to 15thNight
15%2417%26%32%
1875
16th to endNight
13%25%11%26%39%
2112
November1st to 15thNight
16%2416%34%25%
2187
16th to endNight
17%1316%28%32%
2340
December1st to 15thNight
22%36%20%27%19%
2340
16th to endNight
29%37%21%27%11%
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%428%33%15%2
90
16th to endDay
414%18%27%22%12%
96
February1st to 15thDay
415%27%31%14%6%
203
16th to endDay
10%22%31%22%11%2
238
March1st to 15thDay
6%17%27%27%15%5%
270
16th to endDay
5%23%29%24%14%3
288
April1st to 15thDay
7%19%30%25%8%7%
269
16th to endDay
425%36%21%8%4
270
May1st to 15thDay
5%17%32%27%11%5%
288
16th to endDay
411%30%32%17%4
330
June1st to 15thDay
29%34%31%14%6%
315
16th to endDay
119%44%20%13%
315
July1st to 15thDay
2115%42%29%8%
305
16th to endDay
416%34%33%18%
327
August1st to 15thDay
6%8%33%36%13%
315
16th to endDay
5%17%34%34%15%
332
September1st to 15thDay
4217%40%27%7%
294
16th to endDay
5%8%20%36%22%6%
255
October1st to 15thDay
48%26%32%21%6%
195
16th to endDay
2221%33%35%5%
96
November1st to 15thDay
17%14%30%33%13%
90
16th to endDay
411%36%25%20%2
90
December1st to 15thDay
25%16%40%31%4
90
16th to endDay
6%11%20%33%26%2
96
January1st to 15thNight
4416%39%25%10%
720
16th to endNight
7%418%38%25%5%
768
February1st to 15thNight
4417%41%27%4
704
16th to endNight
5%5%23%42%19%4
632
March1st to 15thNight
5%6%20%34%29%4
720
16th to endNight
45%19%37%28%4
768
April1st to 15thNight
46%24%35%25%3
719
16th to endNight
8%28%34%23%5%
543
May1st to 15thNight
25%16%41%29%4
540
16th to endNight
2316%39%32%4
563
June1st to 15thNight
1114%43%32%5%
540
16th to endNight
18%34%47%7%
540
July1st to 15thNight
2224%59%10%
510
16th to endNight
1216%60%18%
564
August1st to 15thNight
3116%60%18%
539
16th to endNight
2215%55%23%
664
September1st to 15thNight
21424%52%15%
700
16th to endNight
2112%29%42%11%
656
October1st to 15thNight
2315%34%36%7%
660
16th to endNight
1210%34%37%13%
704
November1st to 15thNight
3115%36%33%8%
700
16th to endNight
4317%33%31%10%
720
December1st to 15thNight
6%314%39%30%5%
720
16th to endNight
8%6%15%39%24%5%
768
Page generated at 2017-09-11 16:35:26. Version ac04

Copyright 2017 A. Danko


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