Pescadero
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pescadero clear sky chart from 2005-11-05 to 2017-12-20.

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
49%
15829
24%
48108
18%
15792
56%
15792
26%
28978

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
48%
717
19%
2351
16%
716
55%
716
22%
1433
January16th to endNight
45%
768
24%
2496
19%
768
54%
768
21%
1570
February1st to 15thNight
42%
700
22%
2288
20%
700
49%
700
20%
1472
February16th to endNight
37%
632
21%
1903
12%
632
48%
632
19%
1251
March1st to 15thNight
43%
720
18%
1989
14%
720
48%
720
22%
1339
March16th to endNight
36%
768
19%
2100
10%
768
45%
768
22%
1417
April1st to 15thNight
35%
719
20%
1799
9%
719
40%
719
24%
1237
April16th to endNight
40%
720
24%
1800
9%
720
46%
720
30%
1116
May1st to 15thNight
42%
610
23%
1690
11%
610
48%
610
30%
999
May16th to endNight
38%
426
19%
1549
11%
426
49%
426
17%
954
June1st to 15thNight
47%
360
21%
1440
17%
360
59%
360
21%
807
June16th to endNight
59%
360
31%
1440
30%
360
73%
360
33%
645
July1st to 15thNight
62%
420
25%
1440
23%
420
67%
420
30%
739
July16th to endNight
56%
564
26%
1593
18%
531
65%
531
23%
1001
August1st to 15thNight
54%
550
22%
1623
16%
547
56%
547
23%
1039
August16th to endNight
60%
764
27%
1910
14%
764
64%
764
35%
1219
September1st to 15thNight
68%
720
34%
1800
23%
720
71%
720
43%
1042
September16th to endNight
66%
716
38%
1971
28%
716
75%
716
46%
1009
October1st to 15thNight
62%
720
27%
2160
27%
720
68%
720
39%
1146
October16th to endNight
60%
768
32%
2304
28%
768
69%
768
33%
1306
November1st to 15thNight
55%
760
26%
2342
24%
760
60%
760
32%
1335
November16th to endNight
49%
780
25%
2636
23%
780
55%
780
25%
1498
December1st to 15thNight
42%
780
22%
2730
17%
780
52%
780
20%
1644
December16th to endNight
38%
787
20%
2754
16%
787
47%
787
17%
1760

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%6%2432346%9%46%
48730
Night
10%6%2442445%8%45%
48299
TransparencyDay
33%5%7%18%22%13%
48421
Night
35%5%7%17%19%14%
48109
SeeingDay
11%18%23%28%14%3
6382
Night
12%19%10%23%26%8%
15838

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
17%5%24423347%44%
1584
16th to endDay
16%6%35%324347%43%
1728
February1st to 15thDay
18%7%2442435%6%40%
1576
16th to endDay
19%7%25%424447%36%
1571
March1st to 15thDay
17%7%35%43447%8%33%
1970
16th to endDay
14%6%35%5%45%5%47%35%
2124
April1st to 15thDay
16%7%36%32446%7%39%
2149
16th to endDay
10%7%2431245%9%48%
2160
May1st to 15thDay
7%7%23325%46%9%47%
2258
16th to endDay
13%10%2432245%7%41%
2561
June1st to 15thDay
7%6%2442446%9%45%
2520
16th to endDay
341232336%10%59%
2520
July1st to 15thDay
35%133235%8%12%50%
2430
16th to endDay
242332448%13%50%
2468
August1st to 15thDay
36%244245%8%13%42%
2327
16th to endDay
15%1443346%13%50%
2292
September1st to 15thDay
341421446%11%54%
2160
16th to endDay
6%41222325%7%61%
1986
October1st to 15thDay
8%323222247%60%
1800
16th to endDay
9%425%32335%6%52%
1920
November1st to 15thDay
10%425%3345%5%7%47%
1846
16th to endDay
13%7%25%423445%45%
1652
December1st to 15thDay
17%7%3442445%6%40%
1560
16th to endDay
19%7%34423347%39%
1568
January1st to 15thNight
15%5%243245%47%42%
2351
16th to endNight
16%6%25%423337%43%
2496
February1st to 15thNight
16%8%35%425%446%39%
2276
16th to endNight
17%8%35%32445%9%34%
1903
March1st to 15thNight
17%7%35%423447%40%
1989
16th to endNight
16%8%245%33346%40%
2100
April1st to 15thNight
14%7%34435%448%38%
1799
16th to endNight
10%6%23313448%51%
1800
May1st to 15thNight
48%35%32435%7%50%
1690
16th to endNight
9%12%245%2445%7%41%
1548
June1st to 15thNight
5%8%245%25%5%5%8%45%
1440
16th to endNight
2413424349%59%
1440
July1st to 15thNight
25%14426%5%9%11%45%
1527
16th to endNight
27%37%7%46%7%7%8%37%
1701
August1st to 15thNight
39%39%7%36%6%7%11%32%
1632
16th to endNight
17%26%7%35%5%6%11%41%
1910
September1st to 15thNight
25%1442447%9%52%
1800
16th to endNight
331432235%10%59%
1971
October1st to 15thNight
6%424422347%58%
2160
16th to endNight
8%5%2332445%7%52%
2304
November1st to 15thNight
9%5%2432336%7%50%
2342
16th to endNight
10%5%25%423346%49%
2636
December1st to 15thNight
15%7%24423447%43%
2730
16th to endNight
19%7%24424445%41%
2754

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
38%411%19%15%10%
1584
16th to endDay
41%48%13%18%14%
1728
February1st to 15thDay
44%28%18%20%5%
1576
16th to endDay
47%47%24%11%4
1571
March1st to 15thDay
46%410%19%13%5%
1970
16th to endDay
45%5%12%19%14%2
2124
April1st to 15thDay
43%413%21%16%1
2149
16th to endDay
32%312%24%20%5%
2160
May1st to 15thDay
29%5%6%25%25%6%
2258
16th to endDay
39%5%10%20%20%4
2565
June1st to 15thDay
32%7%8%19%21%10%
2520
16th to endDay
19%5%316%34%20%
2520
July1st to 15thDay
23%5%28%22%36%
2288
16th to endDay
19%6%210%30%29%
2313
August1st to 15thDay
27%7%29%28%24%
2311
16th to endDay
22%6%215%31%21%
2292
September1st to 15thDay
22%4214%27%28%
2160
16th to endDay
21%4324%29%17%
1986
October1st to 15thDay
25%27%21%25%18%
1800
16th to endDay
31%38%20%21%13%
1920
November1st to 15thDay
34%5%11%26%17%5%
1846
16th to endDay
38%39%17%25%5%
1652
December1st to 15thDay
44%39%15%17%10%
1560
16th to endDay
44%412%15%16%6%
1568
January1st to 15thNight
39%310%20%15%9%
2351
16th to endNight
40%5%8%11%17%16%
2496
February1st to 15thNight
44%37%17%17%8%
2288
16th to endNight
44%410%24%12%3
1903
March1st to 15thNight
44%410%19%14%6%
1989
16th to endNight
43%411%17%17%5%
2100
April1st to 15thNight
42%5%12%20%16%2
1799
16th to endNight
31%410%24%19%9%
1800
May1st to 15thNight
31%5%7%19%26%11%
1691
16th to endNight
39%6%8%19%19%6%
1549
June1st to 15thNight
32%8%8%15%22%12%
1440
16th to endNight
19%6%212%31%27%
1440
July1st to 15thNight
24%8%26%19%37%
1440
16th to endNight
32%13%27%16%28%
1593
August1st to 15thNight
35%10%7%21%23%
1623
16th to endNight
30%8%210%21%26%
1910
September1st to 15thNight
23%6%210%23%33%
1800
16th to endNight
19%4221%28%23%
1971
October1st to 15thNight
25%46%19%22%22%
2160
16th to endNight
29%5%5%19%22%17%
2304
November1st to 15thNight
31%411%25%19%7%
2342
16th to endNight
34%38%21%22%9%
2636
December1st to 15thNight
40%37%15%19%13%
2730
16th to endNight
44%5%10%14%17%7%
2754

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%24%20%17%13%2
213
16th to endDay
19%23%18%21%14%2
256
February1st to 15thDay
22%26%19%19%9%2
236
16th to endDay
20%22%30%18%7%1
237
March1st to 15thDay
20%24%21%21%9%2
270
16th to endDay
14%28%32%18%41
288
April1st to 15thDay
15%34%26%16%6%
269
16th to endDay
11%31%31%17%6%1
270
May1st to 15thDay
11%26%29%23%7%1
288
16th to endDay
22%23%17%20%13%2
330
June1st to 15thDay
9%21%30%30%7%1
315
16th to endDay
313%26%38%17%
315
July1st to 15thDay
7%8%19%42%19%2
305
16th to endDay
310%21%41%17%6%
327
August1st to 15thDay
6%8%24%39%18%3
315
16th to endDay
26%21%43%21%4
332
September1st to 15thDay
6%9%19%37%20%6%
315
16th to endDay
5%13%19%32%23%5%
315
October1st to 15thDay
6%14%23%34%16%4
315
16th to endDay
11%11%25%25%19%6%
336
November1st to 15thDay
11%14%19%24%25%3
262
16th to endDay
14%14%22%30%14%3
111
December1st to 15thDay
15%16%22%16%22%6%
90
16th to endDay
11%22%22%18%20%5%
72
January1st to 15thNight
16%20%6%23%26%6%
720
16th to endNight
18%22%7%19%23%8%
768
February1st to 15thNight
17%22%10%22%20%6%
704
16th to endNight
18%24%13%22%15%4
632
March1st to 15thNight
15%23%11%21%23%4
720
16th to endNight
17%21%17%23%17%3
768
April1st to 15thNight
14%26%17%19%18%3
719
16th to endNight
10%27%16%20%18%7%
720
May1st to 15thNight
8%23%18%24%19%6%
611
16th to endNight
16%24%12%20%19%7%
427
June1st to 15thNight
10%22%14%22%25%4
360
16th to endNight
5%19%8%33%29%4
360
July1st to 15thNight
6%13%6%24%34%14%
420
16th to endNight
8%17%122%34%15%
564
August1st to 15thNight
13%10%423%36%12%
550
16th to endNight
6%9%7%24%40%10%
764
September1st to 15thNight
6%9%5%25%38%13%
720
16th to endNight
5%12%8%24%34%14%
716
October1st to 15thNight
7%13%9%26%30%12%
720
16th to endNight
11%11%8%23%29%14%
768
November1st to 15thNight
9%16%11%23%30%9%
760
16th to endNight
11%21%8%26%24%7%
780
December1st to 15thNight
16%20%12%22%22%5%
780
16th to endNight
17%26%11%22%17%4
787
Page generated at 2017-12-21 04:04:47. Version ac04

Copyright 2017 A. Danko


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