Mendocino
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mendocino clear sky chart from 2005-11-06 to 2024-04-10.

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 Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(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

By Month

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 Forecast	Data Points
Cloud Cover	Day	13% 8% 3 5% 4 2 4 4 5% 8% 44%	83356
	Night	16% 9% 3 5% 4 2 3 3 4 6% 43%	85526
Transparency	Day	37% 3 10% 23% 19% 9%	83079
	Night	42% 3 9% 19% 17% 9%	85326
Seeing	Day	15% 11% 24% 28% 17% 5%	14546
	Night	16% 5% 14% 28% 28% 8%	23856

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	22% 10% 3 6% 4 3 4 4 4 6% 34%	2772
	11th to 20th	Day	31% 9% 3 7% 6% 2 3 3 4 5% 26%	2860
	21st to end	Day	30% 9% 3 5% 5% 3 3 3 5% 6% 27%	3146
February	1st to 10th	Day	20% 8% 3 4 5% 2 4 3 4 5% 41%	1710
	11th to 20th	Day	18% 8% 3 5% 5% 3 4 4 6% 8% 35%	1665
	21st to end	Day	20% 7% 3 5% 4 3 4 4 4 7% 40%	1580
March	1st to 10th	Day	27% 13% 3 5% 5% 2 3 3 3 6% 28%	3442
	11th to 20th	Day	14% 6% 3 5% 4 2 4 3 4 8% 46%	3490
	21st to end	Day	21% 10% 3 5% 5% 3 5% 6% 5% 8% 29%	3825
April	1st to 10th	Day	16% 8% 3 5% 5% 3 5% 4 6% 8% 38%	2232
	11th to 20th	Day	13% 8% 3 5% 4 3 5% 4 5% 7% 43%	2129
	21st to end	Day	9% 6% 2 5% 4 2 4 4 7% 10% 48%	2232
May	1st to 10th	Day	10% 6% 2 4 3 2 3 3 5% 9% 53%	2340
	11th to 20th	Day	9% 7% 2 5% 5% 2 4 4 5% 10% 46%	2300
	21st to end	Day	10% 8% 3 4 4 2 4 3 5% 8% 49%	2714
June	1st to 10th	Day	10% 9% 3 5% 4 2 4 4 5% 9% 45%	2520
	11th to 20th	Day	3 5% 2 3 3 2 3 2 4 8% 65%	2520
	21st to end	Day	5% 7% 3 5% 4 2 3 3 3 8% 57%	2520
July	1st to 10th	Day	2 7% 2 5% 3 2 3 3 5% 12% 56%	2482
	11th to 20th	Day	3 5% 2 4 4 3 3 3 5% 11% 58%	2340
	21st to end	Day	2 7% 3 4 4 3 3 4 6% 15% 51%	2546
August	1st to 10th	Day	3 8% 3 5% 4 2 4 3 6% 11% 51%	2328
	11th to 20th	Day	3 7% 2 4 4 2 4 4 5% 12% 54%	2298
	21st to end	Day	3 9% 2 5% 4 2 4 5% 6% 12% 49%	2390
September	1st to 10th	Day	3 6% 2 4 3 2 4 3 4 9% 61%	2160
	11th to 20th	Day	6% 7% 2 3 3 3 4 4 5% 10% 53%	2070
	21st to end	Day	3 4 2 4 3 2 3 3 6% 11% 59%	1944
October	1st to 10th	Day	8% 4 1 3 3 2 3 3 4 7% 62%	1800
	11th to 20th	Day	12% 4 2 4 5% 3 4 5% 6% 10% 46%	1800
	21st to end	Day	12% 6% 2 4 4 2 4 3 5% 9% 48%	1980
November	1st to 10th	Day	14% 7% 3 5% 5% 2 4 4 6% 7% 43%	1859
	11th to 20th	Day	16% 7% 3 5% 5% 2 4 4 5% 9% 41%	1600
	21st to end	Day	12% 6% 2 4 4 2 5% 4 5% 6% 48%	1520
December	1st to 10th	Day	18% 9% 4 5% 5% 3 4 3 4 6% 40%	1520
	11th to 20th	Day	31% 9% 4 6% 5% 2 3 4 5% 5% 26%	1928
	21st to end	Day	25% 10% 3 7% 6% 3 4 4 4 6% 29%	2794
January	1st to 10th	Night	21% 10% 3 5% 5% 3 5% 5% 5% 7% 31%	4177
	11th to 20th	Night	27% 11% 4 7% 7% 3 4 3 4 5% 26%	4110
	21st to end	Night	33% 11% 4 6% 5% 2 3 3 3 5% 23%	4521
February	1st to 10th	Night	19% 7% 3 6% 4 2 3 4 4 6% 41%	2470
	11th to 20th	Night	17% 10% 3 6% 6% 3 4 4 5% 7% 35%	2402
	21st to end	Night	19% 6% 3 4 4 2 3 3 4 6% 45%	1867
March	1st to 10th	Night	26% 15% 4 5% 5% 3 3 3 3 5% 28%	3432
	11th to 20th	Night	17% 11% 4 5% 3 2 3 2 3 5% 45%	3490
	21st to end	Night	18% 15% 3 7% 5% 3 4 5% 5% 5% 30%	3828
April	1st to 10th	Night	16% 9% 3 5% 4 2 4 4 4 7% 40%	1937
	11th to 20th	Night	13% 8% 3 5% 5% 2 3 3 5% 8% 46%	1779
	21st to end	Night	8% 7% 2 3 3 2 4 4 5% 10% 52%	1724
May	1st to 10th	Night	9% 7% 2 4 4 2 3 3 4 7% 55%	1620
	11th to 20th	Night	6% 9% 3 7% 6% 3 4 3 5% 9% 45%	1593
	21st to end	Night	10% 10% 3 5% 4 2 3 3 4 7% 51%	1557
June	1st to 10th	Night	8% 9% 3 6% 4 4 4 4 4 7% 48%	1440
	11th to 20th	Night	5% 3 2 4 3 2 2 2 3 6% 68%	1440
	21st to end	Night	4 10% 2 4 3 2 2 2 3 6% 63%	1440
July	1st to 10th	Night	2 8% 2 4 3 2 2 3 4 6% 64%	1473
	11th to 20th	Night	2 5% 2 3 3 2 3 2 3 9% 67%	1620
	21st to end	Night	1 8% 4 6% 4 2 3 4 5% 8% 57%	1773
August	1st to 10th	Night	2 9% 3 4 4 2 3 4 3 7% 59%	1611
	11th to 20th	Night	3 6% 3 4 5% 2 4 4 4 9% 56%	1602
	21st to end	Night	3 8% 2 4 3 2 3 3 3 7% 61%	1966
September	1st to 10th	Night	2 6% 2 3 2 1 2 2 3 7% 70%	1800
	11th to 20th	Night	7% 9% 3 4 3 2 4 3 4 7% 56%	1887
	21st to end	Night	5% 6% 3 4 3 2 3 4 4 6% 59%	2016
October	1st to 10th	Night	6% 7% 2 4 4 2 2 2 2 4 62%	2160
	11th to 20th	Night	10% 6% 3 5% 4 2 4 3 4 7% 53%	2160
	21st to end	Night	13% 6% 3 4 4 3 3 3 4 7% 51%	2376
November	1st to 10th	Night	13% 9% 3 7% 4 3 4 5% 5% 7% 39%	2220
	11th to 20th	Night	16% 9% 3 5% 4 3 5% 4 5% 7% 39%	2577
	21st to end	Night	14% 6% 3 6% 4 3 3 4 5% 7% 47%	2660
December	1st to 10th	Night	21% 8% 3 5% 4 2 3 4 4 7% 38%	2660
	11th to 20th	Night	34% 9% 3 5% 3 2 3 3 5% 6% 28%	3276
	21st to end	Night	24% 10% 4 6% 5% 3 4 4 3 6% 31%	4862

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	54% 3 15% 20% 5% 3	2772
	11th to 20th	Day	63% 2 12% 9% 8% 7%	2860
	21st to end	Day	60% 2 9% 15% 10% 5%	3146
February	1st to 10th	Day	47% 3 9% 17% 18% 6%	1710
	11th to 20th	Day	48% 3 8% 21% 16% 3	1674
	21st to end	Day	46% 4 13% 20% 12% 3	1580
March	1st to 10th	Day	62% 3 8% 18% 9% 1	3442
	11th to 20th	Day	38% 2 13% 23% 15% 8%	3490
	21st to end	Day	57% 3 13% 19% 6% 1	3825
April	1st to 10th	Day	47% 3 13% 24% 11% 1	2232
	11th to 20th	Day	42% 4 14% 26% 12% 3	2132
	21st to end	Day	32% 4 17% 28% 16% 3	2232
May	1st to 10th	Day	30% 3 13% 32% 17% 5%	2340
	11th to 20th	Day	34% 3 12% 32% 16% 4	2303
	21st to end	Day	36% 4 13% 36% 11% 1	2715
June	1st to 10th	Day	36% 3 11% 28% 18% 3	2520
	11th to 20th	Day	19% 3 10% 28% 33% 8%	2520
	21st to end	Day	22% 2 5% 24% 35% 13%	2520
July	1st to 10th	Day	18% 1 5% 20% 35% 21%	2415
	11th to 20th	Day	16% 2 6% 22% 30% 24%	2271
	21st to end	Day	17% 1 3 18% 35% 26%	2405
August	1st to 10th	Day	21% 1 5% 26% 34% 13%	2312
	11th to 20th	Day	17% 1 4 27% 34% 17%	2298
	21st to end	Day	20% 3 6% 25% 32% 14%	2390
September	1st to 10th	Day	16% 2 4 18% 33% 27%	2160
	11th to 20th	Day	25% 2 7% 32% 28% 5%	2070
	21st to end	Day	17% 2 6% 30% 30% 15%	1944
October	1st to 10th	Day	22% 3 5% 29% 25% 16%	1800
	11th to 20th	Day	30% 2 8% 24% 24% 12%	1800
	21st to end	Day	32% 3 9% 25% 18% 12%	1980
November	1st to 10th	Day	40% 3 10% 25% 14% 7%	1859
	11th to 20th	Day	42% 4 13% 21% 13% 7%	1600
	21st to end	Day	37% 4 12% 20% 18% 9%	1520
December	1st to 10th	Day	47% 3 10% 18% 13% 10%	1520
	11th to 20th	Day	61% 3 8% 14% 11% 3	1928
	21st to end	Day	59% 4 9% 18% 8% 2	2794
January	1st to 10th	Night	53% 4 20% 14% 7% 2	4177
	11th to 20th	Night	64% 3 9% 12% 6% 6%	4110
	21st to end	Night	66% 2 6% 12% 10% 4	4521
February	1st to 10th	Night	45% 3 9% 18% 17% 6%	2470
	11th to 20th	Night	51% 4 7% 20% 13% 4	2404
	21st to end	Night	42% 4 13% 24% 14% 3	1867
March	1st to 10th	Night	62% 3 9% 17% 9% 1	3432
	11th to 20th	Night	45% 1 10% 21% 13% 9%	3490
	21st to end	Night	58% 2 13% 19% 7% 1	3828
April	1st to 10th	Night	45% 5% 13% 23% 11% 2	1937
	11th to 20th	Night	40% 4 14% 26% 14% 3	1779
	21st to end	Night	30% 4 16% 32% 16% 3	1724
May	1st to 10th	Night	31% 3 7% 31% 24% 5%	1620
	11th to 20th	Night	38% 3 10% 28% 16% 5%	1594
	21st to end	Night	37% 3 12% 33% 15% 1	1557
June	1st to 10th	Night	35% 3 10% 28% 20% 4	1440
	11th to 20th	Night	19% 2 7% 27% 36% 8%	1440
	21st to end	Night	24% 2 4 16% 36% 17%	1440
July	1st to 10th	Night	18% 2 3 17% 32% 27%	1432
	11th to 20th	Night	14% 2 4 16% 34% 30%	1566
	21st to end	Night	22% 2 2 10% 33% 32%	1674
August	1st to 10th	Night	23% 3 2 22% 32% 17%	1602
	11th to 20th	Night	20% 1 3 19% 31% 26%	1602
	21st to end	Night	19% 2 4 18% 31% 25%	1966
September	1st to 10th	Night	14% 3 1 18% 30% 34%	1800
	11th to 20th	Night	29% 3 4 25% 32% 7%	1887
	21st to end	Night	24% 2 6% 22% 26% 20%	2016
October	1st to 10th	Night	26% 2 5% 24% 24% 19%	2160
	11th to 20th	Night	32% 3 5% 19% 29% 11%	2160
	21st to end	Night	34% 3 8% 22% 18% 14%	2376
November	1st to 10th	Night	45% 4 12% 17% 15% 7%	2220
	11th to 20th	Night	45% 4 13% 19% 14% 5%	2577
	21st to end	Night	39% 3 11% 19% 17% 10%	2660
December	1st to 10th	Night	47% 4 9% 18% 14% 7%	2660
	11th to 20th	Night	59% 3 7% 15% 13% 3	3276
	21st to end	Night	57% 2 13% 19% 7% 2	4862

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	37% 12% 23% 16% 11% 2	322
	11th to 20th	Day	30% 10% 23% 22% 11% 5%	370
	21st to end	Day	26% 11% 22% 22% 15% 4	407
February	1st to 10th	Day	23% 15% 21% 23% 14% 4	370
	11th to 20th	Day	26% 17% 24% 20% 12% 1	365
	21st to end	Day	22% 17% 25% 23% 10% 2	362
March	1st to 10th	Day	33% 16% 25% 18% 7% 1	460
	11th to 20th	Day	26% 13% 30% 19% 9% 2	460
	21st to end	Day	25% 18% 30% 18% 7% 2	506
April	1st to 10th	Day	22% 17% 30% 19% 9% 2	457
	11th to 20th	Day	22% 18% 28% 21% 9% 3	412
	21st to end	Day	12% 22% 31% 19% 10% 4	420
May	1st to 10th	Day	18% 12% 30% 27% 10% 3	423
	11th to 20th	Day	17% 17% 29% 23% 12% 3	448
	21st to end	Day	17% 15% 26% 26% 13% 4	485
June	1st to 10th	Day	12% 15% 26% 29% 14% 3	450
	11th to 20th	Day	8% 15% 33% 30% 12% 3	450
	21st to end	Day	6% 5% 27% 37% 20% 5%	450
July	1st to 10th	Day	6% 4 24% 45% 15% 5%	446
	11th to 20th	Day	2 2 22% 42% 25% 6%	444
	21st to end	Day	3 1 17% 42% 30% 7%	487
August	1st to 10th	Day	5% 4 25% 39% 21% 7%	447
	11th to 20th	Day	5% 3 21% 38% 27% 7%	437
	21st to end	Day	7% 2 20% 38% 24% 8%	495
September	1st to 10th	Day	6% 5% 22% 36% 23% 8%	450
	11th to 20th	Day	7% 6% 23% 37% 22% 5%	450
	21st to end	Day	6% 10% 21% 32% 24% 8%	450
October	1st to 10th	Day	8% 10% 23% 28% 24% 7%	450
	11th to 20th	Day	12% 9% 15% 26% 26% 11%	450
	21st to end	Day	16% 6% 20% 30% 20% 7%	495
November	1st to 10th	Day	16% 11% 21% 25% 21% 6%	455
	11th to 20th	Day	13% 8% 19% 29% 23% 8%	235
	21st to end	Day	16% 6% 23% 24% 23% 9%	180
December	1st to 10th	Day	25% 11% 20% 21% 13% 10%	180
	11th to 20th	Day	28% 12% 19% 22% 11% 8%	180
	21st to end	Day	26% 13% 19% 21% 17% 5%	198
January	1st to 10th	Night	26% 7% 18% 26% 19% 5%	760
	11th to 20th	Night	27% 5% 15% 27% 18% 8%	760
	21st to end	Night	26% 5% 14% 28% 22% 6%	836
February	1st to 10th	Night	22% 8% 14% 32% 20% 4	760
	11th to 20th	Night	22% 9% 18% 28% 19% 5%	744
	21st to end	Night	22% 8% 20% 32% 16% 2	628
March	1st to 10th	Night	29% 11% 15% 28% 14% 4	760
	11th to 20th	Night	28% 7% 11% 29% 21% 4	760
	21st to end	Night	24% 9% 19% 27% 17% 3	836
April	1st to 10th	Night	20% 7% 23% 27% 19% 4	760
	11th to 20th	Night	15% 13% 18% 29% 19% 5%	711
	21st to end	Night	12% 9% 18% 32% 23% 6%	644
May	1st to 10th	Night	11% 7% 21% 28% 25% 7%	540
	11th to 20th	Night	9% 5% 17% 31% 31% 8%	531
	21st to end	Night	12% 8% 19% 28% 27% 5%	394
June	1st to 10th	Night	12% 5% 16% 31% 30% 5%	360
	11th to 20th	Night	4 6% 20% 38% 30% 3	360
	21st to end	Night	7% 1 8% 36% 42% 6%	360
July	1st to 10th	Night	3 1 10% 31% 46% 9%	382
	11th to 20th	Night	3 4 29% 48% 16%	522
	21st to end	Night	1 3 23% 51% 22%	591
August	1st to 10th	Night	4 1 4 28% 48% 15%	537
	11th to 20th	Night	5% 1 4 25% 50% 16%	534
	21st to end	Night	6% 1 5% 26% 47% 14%	778
September	1st to 10th	Night	4 1 7% 26% 45% 16%	720
	11th to 20th	Night	9% 3 9% 28% 38% 12%	720
	21st to end	Night	7% 4 10% 28% 35% 17%	720
October	1st to 10th	Night	8% 4 14% 28% 33% 13%	720
	11th to 20th	Night	13% 3 10% 24% 36% 14%	720
	21st to end	Night	15% 4 10% 27% 32% 12%	792
November	1st to 10th	Night	17% 5% 14% 25% 30% 8%	740
	11th to 20th	Night	20% 5% 13% 30% 26% 6%	760
	21st to end	Night	16% 6% 15% 32% 24% 6%	760
December	1st to 10th	Night	24% 6% 15% 27% 21% 8%	760
	11th to 20th	Night	31% 8% 14% 27% 17% 4	760
	21st to end	Night	30% 8% 18% 24% 16% 4	836

Page generated at 2024-04-07 06:28:12. Version ac07

Copyright © 2024 Attilla Danko.