Parkfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Parkfield clear sky chart from 2005-11-05 to 2017-09-21.

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
76%
15583
32%
46941
29%
15547
79%
15547
50%
23100

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
66%
716
22%
2410
23%
716
68%
716
32%
1352
January16th to endNight
66%
768
27%
2496
30%
768
67%
768
34%
1418
February1st to 15thNight
65%
699
27%
2189
27%
699
69%
699
33%
1263
February16th to endNight
63%
632
26%
1895
27%
632
67%
632
35%
1086
March1st to 15thNight
66%
720
22%
2076
21%
720
70%
720
41%
1172
March16th to endNight
66%
768
25%
2040
20%
768
70%
768
43%
1157
April1st to 15thNight
63%
719
30%
1799
18%
719
67%
719
47%
1013
April16th to endNight
68%
720
32%
1800
15%
720
73%
720
59%
920
May1st to 15thNight
76%
698
30%
1778
18%
698
79%
698
64%
871
May16th to endNight
76%
417
36%
1540
35%
417
82%
417
59%
570
June1st to 15thNight
81%
360
35%
1440
41%
360
86%
360
61%
502
June16th to endNight
92%
360
42%
1440
50%
360
96%
360
85%
407
July1st to 15thNight
95%
346
37%
1366
44%
346
96%
346
78%
414
July16th to endNight
92%
564
40%
1593
36%
531
93%
531
72%
650
August1st to 15thNight
94%
660
41%
1734
29%
657
94%
657
84%
730
August16th to endNight
95%
764
46%
1910
30%
764
95%
764
85%
832
September1st to 15thNight
92%
720
44%
1800
33%
720
93%
720
79%
817
September16th to endNight
90%
680
48%
1829
44%
680
93%
680
79%
783
October1st to 15thNight
77%
660
32%
1969
36%
660
79%
660
50%
961
October16th to endNight
81%
704
40%
2112
43%
704
84%
704
57%
976
November1st to 15thNight
78%
700
35%
2226
36%
700
82%
700
52%
1038
November16th to endNight
74%
720
29%
2340
30%
720
77%
720
43%
1174
December1st to 15thNight
65%
720
26%
2471
26%
720
69%
720
29%
1429
December16th to endNight
59%
768
23%
2688
23%
768
64%
768
27%
1565

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
5%312212335%66%
47919
Night
5%212223335%66%
47127
TransparencyDay
20%36%18%28%21%
47603
Night
20%38%19%27%21%
46943
SeeingDay
7%6%19%33%25%7%
6002
Night
6%38%32%37%11%
15594

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
9%5%14424446%52%
1526
16th to endDay
13%6%24423336%48%
1728
February1st to 15thDay
13%7%33223336%50%
1673
16th to endDay
14%7%44414447%42%
1579
March1st to 15thDay
7%4345%35%5%6%8%44%
1881
16th to endDay
9%5%24434446%49%
2184
April1st to 15thDay
9%6%33313347%52%
2149
16th to endDay
5%22332435%5%61%
2160
May1st to 15thDay
2112222247%68%
2169
16th to endDay
3212212236%70%
2570
June1st to 15thDay
1112212235%73%
2520
16th to endDay
111288%
2520
July1st to 15thDay
11112384%
2511
16th to endDay
11111122380%
2468
August1st to 15thDay
11111286%
2214
16th to endDay
111111387%
2292
September1st to 15thDay
111111385%
2160
16th to endDay
1121233478%
1922
October1st to 15thDay
3213323345%66%
1658
16th to endDay
321321335%5%67%
1760
November1st to 15thDay
6%324323346%61%
1631
16th to endDay
5%424424346%57%
1620
December1st to 15thDay
9%5%36%42445%6%45%
1488
16th to endDay
12%6%35%423347%46%
1536
January1st to 15thNight
8%5%25%42345%7%49%
2410
16th to endNight
11%424334346%51%
2496
February1st to 15thNight
9%5%24324446%51%
2179
16th to endNight
9%5%24423347%52%
1895
March1st to 15thNight
7%315%433438%54%
2076
16th to endNight
6%31332445%7%56%
2040
April1st to 15thNight
4423224346%60%
1799
16th to endNight
311213346%71%
1800
May1st to 15thNight
212212347%72%
1778
16th to endNight
211111235%76%
1539
June1st to 15thNight
111111335%78%
1440
16th to endNight
1292%
1440
July1st to 15thNight
11112386%
1446
16th to endNight
111111112381%
1701
August1st to 15thNight
11111288%
1743
16th to endNight
111387%
1910
September1st to 15thNight
111112385%
1800
16th to endNight
11122384%
1829
October1st to 15thNight
4313322235%68%
1969
16th to endNight
3212212346%69%
2112
November1st to 15thNight
3213213235%68%
2226
16th to endNight
5%32432345%8%58%
2340
December1st to 15thNight
8%4345%35%447%48%
2471
16th to endNight
12%5%23424447%48%
2688

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
32%48%22%21%11%
1526
16th to endDay
36%49%14%21%13%
1728
February1st to 15thDay
36%28%21%22%8%
1673
16th to endDay
41%38%24%19%3
1579
March1st to 15thDay
34%5%11%20%18%8%
1881
16th to endDay
35%411%23%19%5%
2184
April1st to 15thDay
31%39%25%20%8%
2149
16th to endDay
23%310%26%26%9%
2160
May1st to 15thDay
16%36%23%36%12%
2169
16th to endDay
15%36%31%33%8%
2574
June1st to 15thDay
13%27%19%33%23%
2520
16th to endDay
5%119%37%43%
2520
July1st to 15thDay
6%118%26%54%
2362
16th to endDay
10%2310%27%45%
2313
August1st to 15thDay
6%111%34%44%
2198
16th to endDay
7%110%40%39%
2292
September1st to 15thDay
7%1215%33%40%
2160
16th to endDay
9%2120%40%24%
1922
October1st to 15thDay
19%35%22%26%22%
1658
16th to endDay
18%36%19%29%22%
1760
November1st to 15thDay
24%39%20%30%11%
1631
16th to endDay
27%38%20%28%11%
1620
December1st to 15thDay
37%48%17%22%8%
1488
16th to endDay
38%410%20%18%8%
1536
January1st to 15thNight
33%410%20%21%10%
2410
16th to endNight
33%310%14%21%15%
2496
February1st to 15thNight
33%47%23%22%8%
2190
16th to endNight
32%310%26%22%4
1895
March1st to 15thNight
28%414%23%20%9%
2076
16th to endNight
25%415%23%21%8%
2040
April1st to 15thNight
24%313%29%22%7%
1799
16th to endNight
15%313%28%27%11%
1800
May1st to 15thNight
13%29%24%33%15%
1779
16th to endNight
11%28%30%36%10%
1540
June1st to 15thNight
10%27%18%33%27%
1440
16th to endNight
319%35%48%
1440
July1st to 15thNight
5%17%27%57%
1366
16th to endNight
9%129%25%51%
1593
August1st to 15thNight
5%18%31%52%
1734
16th to endNight
4118%38%45%
1910
September1st to 15thNight
7%1212%26%49%
1800
16th to endNight
6%1120%38%30%
1829
October1st to 15thNight
20%35%21%27%21%
1969
16th to endNight
17%25%21%34%19%
2112
November1st to 15thNight
19%29%22%32%13%
2226
16th to endNight
24%311%19%27%13%
2340
December1st to 15thNight
34%5%9%17%22%10%
2471
16th to endNight
36%412%19%17%9%
2688

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
22%428%29%12%2
154
16th to endDay
17%5%23%27%21%3
256
February1st to 15thDay
20%7%21%26%19%3
253
16th to endDay
21%13%20%29%13%1
238
March1st to 15thDay
10%11%27%29%19%1
270
16th to endDay
15%14%23%29%15%1
288
April1st to 15thDay
17%17%26%21%13%4
269
16th to endDay
7%16%29%29%14%2
270
May1st to 15thDay
7%10%25%35%15%6%
288
16th to endDay
5%8%22%34%20%8%
330
June1st to 15thDay
37%20%38%21%8%
315
16th to endDay
1115%34%30%15%
315
July1st to 15thDay
111%40%30%15%
305
16th to endDay
19%35%36%17%
327
August1st to 15thDay
113%41%29%12%
315
16th to endDay
5%31%39%21%
332
September1st to 15thDay
1114%33%37%12%
315
16th to endDay
2114%36%38%6%
276
October1st to 15thDay
45%24%38%23%3
255
16th to endDay
9%5%19%34%30%1
272
November1st to 15thDay
5%5%13%24%43%8%
137
16th to endDay
6%11%21%43%17%
90
December1st to 15thDay
10%8%30%33%16%
68
16th to endDay
18%9%17%34%20%
64
January1st to 15thNight
13%27%35%30%10%
720
16th to endNight
14%38%36%27%9%
768
February1st to 15thNight
13%49%33%29%9%
704
16th to endNight
15%5%9%40%22%6%
632
March1st to 15thNight
8%312%38%28%8%
720
16th to endNight
7%6%13%33%31%6%
768
April1st to 15thNight
6%8%15%36%27%4
719
16th to endNight
46%19%31%30%8%
720
May1st to 15thNight
3312%39%31%9%
699
16th to endNight
35%11%36%37%5%
418
June1st to 15thNight
329%39%40%4
360
16th to endNight
5%35%50%7%
360
July1st to 15thNight
1125%60%11%
346
16th to endNight
2116%56%22%
564
August1st to 15thNight
1223%58%14%
660
16th to endNight
1117%60%19%
764
September1st to 15thNight
1220%55%19%
720
16th to endNight
5%25%48%18%
680
October1st to 15thNight
6%35%31%38%15%
660
16th to endNight
6%15%32%36%16%
704
November1st to 15thNight
419%35%38%12%
700
16th to endNight
5%38%37%32%12%
720
December1st to 15thNight
10%47%38%30%7%
720
16th to endNight
14%6%11%37%23%6%
768
Page generated at 2017-09-22 04:35:35. Version ac04

Copyright 2017 A. Danko


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