Gualala
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gualala clear sky chart from 2005-11-05 to 2017-09-20.

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
50%
15325
25%
46961
18%
15287
58%
15287
29%
26810

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
45%
717
16%
2348
12%
716
51%
716
21%
1480
January16th to endNight
45%
768
24%
2496
20%
768
53%
768
21%
1564
February1st to 15thNight
39%
700
21%
2288
18%
700
46%
700
18%
1493
February16th to endNight
37%
632
20%
1935
11%
632
48%
632
19%
1275
March1st to 15thNight
39%
720
13%
1980
10%
720
42%
720
19%
1416
March16th to endNight
34%
768
19%
2112
10%
768
42%
768
22%
1389
April1st to 15thNight
33%
719
21%
1817
8%
719
40%
719
23%
1220
April16th to endNight
38%
694
26%
1774
9%
694
46%
694
32%
1037
May1st to 15thNight
42%
539
27%
1619
12%
539
54%
539
35%
809
May16th to endNight
45%
440
24%
1562
14%
439
58%
439
30%
752
June1st to 15thNight
43%
360
23%
1440
16%
360
58%
360
27%
712
June16th to endNight
55%
360
33%
1440
29%
360
73%
360
45%
532
July1st to 15thNight
69%
426
28%
1446
25%
426
76%
426
54%
565
July16th to endNight
67%
564
31%
1593
24%
531
78%
531
46%
757
August1st to 15thNight
74%
538
33%
1611
25%
535
79%
535
55%
705
August16th to endNight
72%
713
38%
1859
22%
713
78%
713
52%
944
September1st to 15thNight
72%
720
37%
1800
22%
720
77%
720
56%
911
September16th to endNight
67%
675
38%
1882
27%
675
77%
675
52%
907
October1st to 15thNight
59%
660
28%
1980
25%
660
67%
660
38%
1050
October16th to endNight
58%
704
30%
2112
24%
704
69%
704
33%
1184
November1st to 15thNight
51%
700
23%
2139
18%
700
58%
700
28%
1260
November16th to endNight
44%
720
19%
2520
17%
720
50%
720
21%
1481
December1st to 15thNight
41%
720
19%
2520
16%
720
47%
720
18%
1610
December16th to endNight
37%
768
19%
2688
17%
768
44%
768
17%
1757

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
10%313323347%55%
47868
Night
13%413323347%53%
47152
TransparencyDay
30%411%21%21%11%
47560
Night
32%410%19%20%12%
46962
SeeingDay
13%17%23%24%16%4
6081
Night
13%18%12%23%23%8%
15333

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
19%5%35%42335%6%40%
1587
16th to endDay
20%5%25%424347%40%
1728
February1st to 15thDay
23%424423347%37%
1576
16th to endDay
21%4245%3445%7%36%
1535
March1st to 15thDay
22%6%35%424447%33%
1980
16th to endDay
19%5%2442445%7%39%
2112
April1st to 15thDay
16%5%144245%5%8%38%
2131
16th to endDay
9%31233436%9%51%
2184
May1st to 15thDay
6%21211345%9%60%
2331
16th to endDay
7%31331335%9%56%
2547
June1st to 15thDay
6%313323248%58%
2520
16th to endDay
31112235%76%
2520
July1st to 15thDay
12112226%78%
2424
16th to endDay
12223238%70%
2468
August1st to 15thDay
122122237%72%
2340
16th to endDay
1212212338%69%
2342
September1st to 15thDay
2111212338%71%
2160
16th to endDay
5%22211237%70%
1843
October1st to 15thDay
10%312214245%62%
1650
16th to endDay
13%412423349%50%
1760
November1st to 15thDay
10%423425%5%48%47%
1714
16th to endDay
17%5%24424336%45%
1440
December1st to 15thDay
24%7%24423336%37%
1440
16th to endDay
26%6%2432345%7%33%
1536
January1st to 15thNight
18%5%243345%5%8%39%
2348
16th to endNight
21%5%23322347%42%
2496
February1st to 15thNight
22%5%2442345%6%39%
2276
16th to endNight
20%6%1421446%8%38%
1935
March1st to 15thNight
22%5%25%425%45%5%34%
1980
16th to endNight
20%414423446%43%
2112
April1st to 15thNight
14%6%24425%45%6%42%
1817
16th to endNight
9%312324247%58%
1774
May1st to 15thNight
4323213239%63%
1619
16th to endNight
431332335%10%58%
1561
June1st to 15thNight
5%5%23323248%58%
1440
16th to endNight
321112225%77%
1440
July1st to 15thNight
11121222478%
1533
16th to endNight
141312147%70%
1701
August1st to 15thNight
211111237%75%
1620
16th to endNight
1312212236%72%
1859
September1st to 15thNight
1212111337%73%
1800
16th to endNight
4212111226%72%
1882
October1st to 15thNight
7%423322335%62%
1980
16th to endNight
13%313212347%54%
2112
November1st to 15thNight
14%31332346%9%47%
2139
16th to endNight
18%42342345%7%45%
2520
December1st to 15thNight
25%5%14323346%38%
2520
16th to endNight
24%5%24413337%37%
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
44%413%17%11%8%
1587
16th to endDay
42%6%8%14%16%10%
1728
February1st to 15thDay
45%410%18%17%3
1576
16th to endDay
45%412%22%10%3
1535
March1st to 15thDay
49%6%11%14%13%3
1980
16th to endDay
43%6%14%19%14%2
2112
April1st to 15thDay
40%6%15%24%12%1
2131
16th to endDay
28%7%15%25%18%5%
2184
May1st to 15thDay
20%413%29%24%7%
2331
16th to endDay
24%6%16%28%20%4
2551
June1st to 15thDay
23%6%13%22%23%10%
2520
16th to endDay
13%27%18%37%20%
2520
July1st to 15thDay
13%37%19%31%25%
2283
16th to endDay
20%27%16%22%31%
2313
August1st to 15thDay
18%36%22%29%20%
2324
16th to endDay
18%49%18%31%18%
2342
September1st to 15thDay
17%38%20%28%21%
2160
16th to endDay
19%17%28%28%14%
1843
October1st to 15thDay
24%39%22%26%12%
1650
16th to endDay
34%411%21%19%7%
1760
November1st to 15thDay
32%7%14%28%11%5%
1714
16th to endDay
40%5%12%18%17%5%
1440
December1st to 15thDay
49%411%16%15%3
1440
16th to endDay
49%5%8%18%14%4
1536
January1st to 15thNight
41%5%14%18%11%8%
2348
16th to endNight
42%38%16%16%11%
2496
February1st to 15thNight
45%410%17%15%5%
2288
16th to endNight
43%5%11%22%13%3
1935
March1st to 15thNight
48%6%11%14%15%4
1980
16th to endNight
41%413%21%15%3
2112
April1st to 15thNight
40%5%14%23%13%2
1817
16th to endNight
28%410%30%20%6%
1774
May1st to 15thNight
20%5%10%25%29%8%
1620
16th to endNight
22%5%14%31%20%6%
1562
June1st to 15thNight
24%7%10%21%23%12%
1440
16th to endNight
13%26%14%35%27%
1440
July1st to 15thNight
11%2412%32%35%
1446
16th to endNight
18%36%11%19%39%
1593
August1st to 15thNight
14%26%17%30%28%
1611
16th to endNight
16%4415%28%29%
1859
September1st to 15thNight
15%3416%30%30%
1800
16th to endNight
17%15%22%31%22%
1882
October1st to 15thNight
26%38%21%25%15%
1980
16th to endNight
30%39%22%24%10%
2112
November1st to 15thNight
34%5%16%23%13%6%
2139
16th to endNight
37%412%21%17%6%
2520
December1st to 15thNight
46%39%19%16%3
2520
16th to endNight
45%5%10%16%16%4
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
25%23%15%16%16%2
216
16th to endDay
25%19%15%19%17%2
256
February1st to 15thDay
24%21%22%16%13%
236
16th to endDay
21%26%23%17%9%1
226
March1st to 15thDay
28%21%24%13%8%3
270
16th to endDay
22%25%29%15%42
288
April1st to 15thDay
20%27%23%18%8%1
269
16th to endDay
20%29%26%15%5%2
270
May1st to 15thDay
11%26%31%19%11%1
288
16th to endDay
13%19%22%23%15%6%
330
June1st to 15thDay
8%21%30%26%9%3
315
16th to endDay
315%34%26%17%2
315
July1st to 15thDay
11%19%36%24%7%
305
16th to endDay
10%19%37%22%8%
327
August1st to 15thDay
310%21%33%25%5%
315
16th to endDay
7%21%32%29%7%
332
September1st to 15thDay
39%19%33%25%8%
315
16th to endDay
6%11%22%26%23%9%
272
October1st to 15thDay
12%15%22%20%19%9%
255
16th to endDay
16%13%25%25%17%2
272
November1st to 15thDay
11%19%17%24%21%5%
225
16th to endDay
20%10%35%16%11%6%
60
December1st to 15thDay
46%13%18%16%13
60
16th to endDay
26%10%14%18%18%10%
64
January1st to 15thNight
18%19%8%22%23%8%
720
16th to endNight
22%20%6%19%22%8%
768
February1st to 15thNight
21%21%11%20%19%6%
704
16th to endNight
22%21%15%23%13%4
632
March1st to 15thNight
21%22%10%21%18%5%
720
16th to endNight
20%22%18%23%12%3
768
April1st to 15thNight
16%25%18%20%14%5%
719
16th to endNight
11%26%19%21%14%5%
694
May1st to 15thNight
425%23%24%16%6%
540
16th to endNight
6%23%18%25%19%6%
440
June1st to 15thNight
6%23%21%24%23%1
360
16th to endNight
419%19%35%18%1
360
July1st to 15thNight
112%11%27%34%13%
426
16th to endNight
218%5%25%34%14%
564
August1st to 15thNight
110%8%29%35%14%
538
16th to endNight
39%8%25%42%11%
713
September1st to 15thNight
210%9%23%37%15%
720
16th to endNight
6%13%7%26%32%12%
675
October1st to 15thNight
8%14%11%24%28%12%
660
16th to endNight
15%12%7%23%29%11%
704
November1st to 15thNight
13%18%11%19%29%8%
700
16th to endNight
16%21%10%22%21%6%
720
December1st to 15thNight
24%19%10%22%17%5%
720
16th to endNight
21%22%12%20%17%4
768
Page generated at 2017-09-21 04:18:22. Version ac04

Copyright 2017 A. Danko


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