Twentynine Palms Airport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Twentynine Palms Airport clear sky chart from 2005-11-05 to 2017-10-31.

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
77%
16247
40%
47465
33%
16206
84%
16206
67%
20334

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
72%
719
35%
2327
30%
716
82%
716
53%
1027
January16th to endNight
66%
768
40%
2380
31%
768
79%
768
53%
1098
February1st to 15thNight
71%
700
39%
2109
33%
699
82%
699
59%
932
February16th to endNight
64%
632
39%
1895
37%
632
74%
632
53%
900
March1st to 15thNight
67%
720
38%
2125
32%
720
79%
720
62%
926
March16th to endNight
69%
768
40%
2099
29%
768
79%
768
63%
962
April1st to 15thNight
60%
719
39%
1799
18%
719
72%
719
66%
860
April16th to endNight
67%
693
45%
1773
22%
693
78%
693
78%
759
May1st to 15thNight
73%
539
43%
1619
30%
539
79%
539
78%
609
May16th to endNight
74%
562
41%
1685
29%
561
81%
561
78%
636
June1st to 15thNight
81%
540
36%
1620
29%
540
84%
540
83%
601
June16th to endNight
85%
540
37%
1620
33%
540
86%
540
82%
608
July1st to 15thNight
92%
510
32%
1530
29%
510
92%
510
69%
638
July16th to endNight
88%
564
36%
1593
31%
531
89%
531
60%
719
August1st to 15thNight
93%
677
38%
1751
26%
674
93%
674
75%
797
August16th to endNight
93%
764
44%
1910
31%
764
94%
764
75%
894
September1st to 15thNight
92%
720
39%
1905
32%
720
93%
720
75%
849
September16th to endNight
89%
716
50%
1980
44%
716
93%
716
85%
791
October1st to 15thNight
79%
720
45%
1980
37%
720
86%
720
76%
845
October16th to endNight
85%
768
48%
2314
46%
768
91%
768
76%
900
November1st to 15thNight
80%
700
40%
2275
37%
700
91%
700
69%
879
November16th to endNight
75%
720
44%
2340
43%
720
84%
720
66%
923
December1st to 15thNight
73%
720
38%
2340
33%
720
82%
720
54%
1030
December16th to endNight
63%
768
38%
2496
32%
768
74%
768
48%
1151

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
111212235%77%
48280
Night
111112235%77%
47663
TransparencyDay
11%2312%26%43%
47975
Night
10%2413%28%41%
47469
SeeingDay
37%18%33%27%9%
5952
Night
2313%35%37%7%
16254

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
1213313346%69%
1611
16th to endDay
2212314436%67%
1842
February1st to 15thDay
112213336%71%
1751
16th to endDay
11222345%6%68%
1579
March1st to 15thDay
11111225%7%76%
1833
16th to endDay
2212336%76%
2122
April1st to 15thDay
111212347%73%
2149
16th to endDay
11112485%
2187
May1st to 15thDay
11112483%
2331
16th to endDay
111112384%
2429
June1st to 15thDay
1112486%
2340
16th to endDay
111288%
2340
July1st to 15thDay
211212347%71%
2340
16th to endDay
221231335%6%67%
2467
August1st to 15thDay
11121234476%
2197
16th to endDay
211212336%74%
2292
September1st to 15thDay
1212345%76%
2055
16th to endDay
11112286%
1980
October1st to 15thDay
121223480%
1980
16th to endDay
111122482%
1903
November1st to 15thDay
1111232478%
1584
16th to endDay
11112236%77%
1620
December1st to 15thDay
2212323348%66%
1620
16th to endDay
3312312446%66%
1728
January1st to 15thNight
1212213446%68%
2327
16th to endNight
2212313345%69%
2380
February1st to 15thNight
1212212336%72%
2101
16th to endNight
2112314347%66%
1895
March1st to 15thNight
111113346%74%
2125
16th to endNight
11212237%75%
2099
April1st to 15thNight
11121223478%
1799
16th to endNight
1125%85%
1773
May1st to 15thNight
1116%85%
1619
16th to endNight
1122486%
1684
June1st to 15thNight
111487%
1620
16th to endNight
111189%
1620
July1st to 15thNight
12112235%78%
1620
16th to endNight
211223345%71%
1701
August1st to 15thNight
11223480%
1760
16th to endNight
1111223480%
1910
September1st to 15thNight
1111335%79%
1905
16th to endNight
111290%
1980
October1st to 15thNight
1111123382%
1980
16th to endNight
111122483%
2314
November1st to 15thNight
113225%80%
2275
16th to endNight
21111113478%
2340
December1st to 15thNight
212222348%68%
2340
16th to endNight
3212322345%68%
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
17%26%18%34%21%
1612
16th to endDay
18%35%19%30%23%
1842
February1st to 15thDay
14%26%17%30%28%
1751
16th to endDay
15%45%18%32%22%
1579
March1st to 15thDay
9%2317%32%34%
1833
16th to endDay
10%3318%36%27%
2122
April1st to 15thDay
12%2312%34%34%
2149
16th to endDay
6%1113%33%43%
2187
May1st to 15thDay
6%129%29%50%
2331
16th to endDay
6%119%27%53%
2432
June1st to 15thDay
5%27%17%67%
2340
16th to endDay
6%29%79%
2340
July1st to 15thDay
12%238%17%54%
2201
16th to endDay
15%46%13%24%36%
2312
August1st to 15thDay
10%239%23%51%
2182
16th to endDay
12%329%22%49%
2292
September1st to 15thDay
9%3411%19%51%
2055
16th to endDay
6%11423%63%
1980
October1st to 15thDay
9%227%27%50%
1980
16th to endDay
8%1310%24%52%
1903
November1st to 15thDay
10%2314%32%36%
1584
16th to endDay
10%1416%32%34%
1620
December1st to 15thDay
17%36%22%27%21%
1620
16th to endDay
18%39%25%25%17%
1728
January1st to 15thNight
15%35%17%31%26%
2327
16th to endNight
17%35%19%25%29%
2380
February1st to 15thNight
14%25%16%30%30%
2112
16th to endNight
17%2417%33%23%
1895
March1st to 15thNight
11%2417%32%31%
2125
16th to endNight
11%2416%34%29%
2099
April1st to 15thNight
10%2414%34%32%
1799
16th to endNight
41312%33%44%
1773
May1st to 15thNight
41212%33%45%
1620
16th to endNight
41211%35%44%
1685
June1st to 15thNight
4118%19%64%
1620
16th to endNight
5%49%78%
1620
July1st to 15thNight
10%227%18%58%
1530
16th to endNight
14%35%12%27%35%
1593
August1st to 15thNight
8%229%23%52%
1751
16th to endNight
8%228%23%53%
1910
September1st to 15thNight
8%2410%20%53%
1905
16th to endNight
415%21%66%
1980
October1st to 15thNight
8%129%30%48%
1980
16th to endNight
6%239%22%55%
2314
November1st to 15thNight
9%2410%33%39%
2275
16th to endNight
10%1214%33%36%
2340
December1st to 15thNight
15%47%17%29%26%
2340
16th to endNight
18%39%20%29%19%
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
10%11%22%35%21%
90
16th to endDay
5%10%28%33%17%5%
210
February1st to 15thDay
410%25%34%19%5%
266
16th to endDay
8%17%24%27%19%2
238
March1st to 15thDay
217%17%31%24%5%
270
16th to endDay
415%22%32%17%7%
288
April1st to 15thDay
8%17%23%25%18%7%
269
16th to endDay
319%29%25%18%4
270
May1st to 15thDay
210%23%36%21%5%
288
16th to endDay
7%24%35%24%7%
330
June1st to 15thDay
1321%37%29%6%
315
16th to endDay
2117%34%28%14%
315
July1st to 15thDay
28%38%32%17%
305
16th to endDay
16%39%34%16%
327
August1st to 15thDay
212%40%34%10%
315
16th to endDay
18%30%37%20%
332
September1st to 15thDay
13%38%36%8%
315
16th to endDay
16%14%33%33%10%
315
October1st to 15thDay
17%20%34%28%7%
315
16th to endDay
412%31%31%18%
213
November1st to 15thDay
5%17%22%36%17%
90
16th to endDay
36%31%21%25%12%
90
December1st to 15thDay
310%11%35%34%5%
90
16th to endDay
7%7%21%38%23%1
96
January1st to 15thNight
2417%42%26%6%
720
16th to endNight
4319%39%27%5%
768
February1st to 15thNight
3416%42%28%6%
704
16th to endNight
36%21%41%21%5%
632
March1st to 15thNight
26%20%37%26%6%
720
16th to endNight
18%17%37%27%7%
768
April1st to 15thNight
19%25%35%22%5%
719
16th to endNight
7%22%38%25%4
693
May1st to 15thNight
1418%34%36%4
540
16th to endNight
5%17%36%34%4
563
June1st to 15thNight
115%43%34%4
540
16th to endNight
111%37%45%3
540
July1st to 15thNight
2130%58%7%
510
16th to endNight
2225%62%7%
564
August1st to 15thNight
2223%60%11%
677
16th to endNight
1116%61%18%
764
September1st to 15thNight
1126%56%13%
720
16th to endNight
7%31%48%10%
716
October1st to 15thNight
115%37%38%5%
720
16th to endNight
128%34%41%12%
768
November1st to 15thNight
114%37%36%9%
700
16th to endNight
3314%33%34%11%
720
December1st to 15thNight
3315%44%26%6%
720
16th to endNight
6%5%19%39%24%5%
768
Page generated at 2017-11-01 14:23:38. Version ac04

Copyright 2017 A. Danko


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