Montebello
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Montebello clear sky chart from 2005-11-06 to 2024-03-28.

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	7% 5% 2 4 4 2 4 4 5% 7% 56%	78931
	Night	7% 6% 2 5% 5% 3 4 4 5% 7% 51%	81097
Transparency	Day	28% 4 10% 20% 23% 15%	78652
	Night	31% 4 11% 20% 20% 14%	80898
Seeing	Day	8% 12% 27% 31% 18% 5%	14579
	Night	9% 7% 17% 31% 29% 7%	24070

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	13% 8% 3 7% 6% 4 5% 5% 5% 6% 38%	2740
	11th to 20th	Day	12% 8% 5% 10% 8% 4 6% 4 5% 6% 32%	2860
	21st to end	Day	14% 11% 4 8% 7% 3 5% 6% 6% 8% 29%	3146
February	1st to 10th	Day	12% 7% 3 6% 5% 3 4 5% 6% 6% 44%	1710
	11th to 20th	Day	11% 8% 3 6% 5% 3 4 5% 5% 7% 43%	1755
	21st to end	Day	11% 7% 3 7% 6% 3 3 4 5% 6% 46%	1570
March	1st to 10th	Day	12% 9% 3 7% 7% 3 5% 5% 6% 8% 33%	2057
	11th to 20th	Day	10% 7% 3 7% 8% 4 4 5% 6% 8% 37%	2090
	21st to end	Day	11% 5% 3 6% 6% 4 5% 5% 6% 7% 43%	2282
April	1st to 10th	Day	12% 7% 3 6% 5% 3 4 4 5% 8% 44%	2160
	11th to 20th	Day	9% 5% 2 4 4 2 3 5% 5% 7% 53%	2129
	21st to end	Day	6% 4 2 4 4 3 3 4 5% 9% 56%	2160
May	1st to 10th	Day	4 4 2 4 3 2 3 4 5% 8% 60%	2216
	11th to 20th	Day	5% 4 2 4 3 2 3 4 4 10% 60%	2326
	21st to end	Day	5% 5% 2 4 4 3 4 6% 5% 8% 55%	2723
June	1st to 10th	Day	5% 4 2 3 3 2 4 5% 5% 7% 61%	2520
	11th to 20th	Day	2 1 1 2 1 1 2 3 5% 7% 74%	2520
	21st to end	Day	1 2 1 2 2 1 2 3 3 5% 77%	2520
July	1st to 10th	Day	1 1 1 2 2 1 2 3 4 7% 77%	2505
	11th to 20th	Day	2 2 1 2 2 2 3 3 4 7% 73%	2340
	21st to end	Day	1 1 1 1 1 1 2 3 4 6% 79%	2546
August	1st to 10th	Day	2 2 1 2 2 2 3 3 5% 8% 70%	2328
	11th to 20th	Day	1 1 1 2 1 1 2 3 4 7% 78%	2179
	21st to end	Day	1 1 1 2 1 3 3 4 9% 75%	2376
September	1st to 10th	Day	1 1 1 2 1 1 2 2 3 6% 79%	2160
	11th to 20th	Day	2 3 1 3 3 2 3 4 5% 9% 65%	2160
	21st to end	Day	2 3 1 2 2 1 2 2 3 6% 75%	1908
October	1st to 10th	Day	4 3 2 3 3 1 3 3 3 7% 68%	1800
	11th to 20th	Day	5% 3 1 3 4 2 3 4 5% 9% 62%	1800
	21st to end	Day	5% 4 2 3 4 2 4 4 5% 6% 61%	1980
November	1st to 10th	Day	7% 4 2 5% 5% 3 5% 4 4 8% 53%	1840
	11th to 20th	Day	7% 5% 3 5% 5% 3 5% 5% 5% 6% 50%	1710
	21st to end	Day	8% 5% 3 4 4 3 4 4 5% 8% 53%	1573
December	1st to 10th	Day	8% 6% 4 6% 7% 3 5% 6% 6% 8% 42%	1520
	11th to 20th	Day	16% 10% 4 8% 7% 3 6% 5% 6% 6% 30%	1928
	21st to end	Day	11% 10% 4 8% 7% 4 5% 5% 5% 7% 34%	2794
January	1st to 10th	Night	12% 9% 3 6% 5% 3 4 4 6% 6% 41%	4207
	11th to 20th	Night	12% 9% 4 10% 8% 5% 6% 5% 5% 5% 30%	4110
	21st to end	Night	14% 12% 4 8% 8% 4 6% 4 4 6% 30%	4521
February	1st to 10th	Night	10% 8% 4 4 6% 3 4 4 4 5% 47%	2470
	11th to 20th	Night	11% 6% 2 6% 5% 4 4 5% 5% 8% 42%	2309
	21st to end	Night	10% 6% 3 5% 5% 3 4 4 6% 6% 48%	1884
March	1st to 10th	Night	12% 8% 3 7% 6% 4 5% 6% 5% 6% 38%	2119
	11th to 20th	Night	11% 7% 3 5% 5% 4 4 5% 5% 8% 42%	2090
	21st to end	Night	9% 8% 3 5% 5% 3 6% 5% 3 6% 46%	2227
April	1st to 10th	Night	10% 6% 4 6% 5% 3 5% 6% 6% 7% 44%	1800
	11th to 20th	Night	8% 6% 2 5% 4 2 4 5% 4 8% 51%	1779
	21st to end	Night	5% 3 1 3 3 3 4 5% 6% 10% 58%	1800
May	1st to 10th	Night	3 5% 2 4 4 2 3 4 7% 9% 56%	1741
	11th to 20th	Night	2 4 2 4 4 3 5% 5% 7% 10% 54%	1563
	21st to end	Night	3 2 2 3 3 3 7% 7% 8% 10% 51%	1552
June	1st to 10th	Night	3 4 1 5% 4 1 4 4 6% 9% 60%	1440
	11th to 20th	Night	1 1 1 2 3 2 2 4 6% 8% 72%	1440
	21st to end	Night	1 2 1 3 2 2 2 2 3 7% 74%	1440
July	1st to 10th	Night	2 1 1 1 1 3 3 5% 9% 74%	1449
	11th to 20th	Night	1 2 1 2 2 2 3 4 6% 8% 72%	1620
	21st to end	Night	1 1 2 3 2 4 5% 9% 10% 64%	1773
August	1st to 10th	Night	1 3 1 3 3 3 3 6% 7% 11% 58%	1611
	11th to 20th	Night	1 1 2 3 1 3 4 7% 10% 68%	1719
	21st to end	Night	1 2 1 1 2 2 3 4 6% 9% 69%	1980
September	1st to 10th	Night	1 2 1 1 2 1 2 3 5% 9% 73%	1800
	11th to 20th	Night	3 3 1 4 3 3 4 5% 5% 9% 62%	1800
	21st to end	Night	2 2 1 2 2 1 2 2 4 7% 74%	2048
October	1st to 10th	Night	4 3 1 2 3 2 4 4 5% 6% 67%	2160
	11th to 20th	Night	4 3 2 4 4 2 4 4 5% 6% 61%	2160
	21st to end	Night	4 3 2 4 3 2 2 4 5% 7% 63%	2376
November	1st to 10th	Night	6% 5% 2 5% 4 2 4 3 5% 9% 55%	2237
	11th to 20th	Night	7% 6% 2 5% 4 3 4 5% 6% 8% 50%	2470
	21st to end	Night	7% 4 3 4 4 3 4 4 4 7% 56%	2604
December	1st to 10th	Night	9% 6% 3 6% 5% 4 5% 4 5% 7% 46%	2660
	11th to 20th	Night	16% 9% 4 8% 7% 4 4 5% 5% 7% 30%	3276
	21st to end	Night	12% 8% 3 8% 8% 4 6% 6% 6% 6% 34%	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	43% 8% 12% 25% 8% 3	2740
	11th to 20th	Day	51% 6% 11% 14% 10% 8%	2860
	21st to end	Day	52% 6% 9% 14% 13% 5%	3146
February	1st to 10th	Day	40% 4 8% 20% 17% 11%	1710
	11th to 20th	Day	39% 4 10% 18% 21% 7%	1764
	21st to end	Day	40% 4 8% 23% 18% 7%	1570
March	1st to 10th	Day	46% 5% 11% 19% 15% 4	2057
	11th to 20th	Day	43% 5% 11% 18% 18% 4	2090
	21st to end	Day	39% 6% 13% 20% 17% 4	2282
April	1st to 10th	Day	40% 3 13% 19% 19% 5%	2160
	11th to 20th	Day	30% 4 15% 24% 21% 5%	2132
	21st to end	Day	25% 4 15% 28% 23% 5%	2160
May	1st to 10th	Day	23% 5% 13% 25% 29% 6%	2216
	11th to 20th	Day	20% 3 16% 27% 26% 8%	2329
	21st to end	Day	25% 5% 20% 25% 21% 4	2724
June	1st to 10th	Day	21% 5% 14% 26% 25% 9%	2520
	11th to 20th	Day	10% 3 12% 26% 33% 17%	2520
	21st to end	Day	11% 2 6% 19% 31% 32%	2520
July	1st to 10th	Day	8% 2 5% 16% 27% 42%	2436
	11th to 20th	Day	10% 2 7% 19% 26% 37%	2271
	21st to end	Day	7% 2 3 17% 33% 37%	2405
August	1st to 10th	Day	13% 2 5% 21% 31% 27%	2312
	11th to 20th	Day	8% 2 5% 19% 33% 34%	2179
	21st to end	Day	9% 1 5% 23% 33% 29%	2376
September	1st to 10th	Day	8% 2 4 14% 30% 42%	2160
	11th to 20th	Day	16% 4 9% 25% 28% 18%	2160
	21st to end	Day	13% 2 8% 22% 34% 22%	1908
October	1st to 10th	Day	19% 3 7% 18% 28% 25%	1800
	11th to 20th	Day	20% 4 10% 19% 23% 24%	1800
	21st to end	Day	24% 2 10% 20% 24% 20%	1980
November	1st to 10th	Day	31% 5% 8% 22% 22% 12%	1840
	11th to 20th	Day	32% 6% 10% 22% 22% 8%	1710
	21st to end	Day	31% 4 8% 17% 29% 10%	1573
December	1st to 10th	Day	39% 5% 11% 18% 16% 11%	1520
	11th to 20th	Day	54% 5% 9% 13% 13% 5%	1928
	21st to end	Day	48% 6% 12% 19% 11% 3	2794
January	1st to 10th	Night	40% 7% 18% 22% 10% 3	4207
	11th to 20th	Night	52% 6% 14% 11% 9% 8%	4110
	21st to end	Night	54% 6% 10% 11% 12% 7%	4521
February	1st to 10th	Night	38% 3 9% 19% 19% 12%	2470
	11th to 20th	Night	37% 4 11% 19% 22% 7%	2311
	21st to end	Night	35% 5% 11% 29% 16% 5%	1884
March	1st to 10th	Night	46% 5% 13% 18% 14% 5%	2119
	11th to 20th	Night	39% 5% 9% 21% 18% 7%	2090
	21st to end	Night	39% 5% 15% 20% 17% 5%	2227
April	1st to 10th	Night	37% 5% 16% 21% 16% 5%	1800
	11th to 20th	Night	31% 4 13% 25% 19% 7%	1779
	21st to end	Night	21% 5% 16% 29% 23% 7%	1800
May	1st to 10th	Night	24% 3 13% 23% 25% 12%	1741
	11th to 20th	Night	21% 4 17% 26% 25% 8%	1564
	21st to end	Night	22% 5% 24% 22% 22% 4	1552
June	1st to 10th	Night	18% 5% 15% 26% 25% 10%	1440
	11th to 20th	Night	10% 3 10% 25% 30% 22%	1440
	21st to end	Night	13% 1 6% 19% 31% 29%	1440
July	1st to 10th	Night	7% 1 5% 17% 31% 39%	1409
	11th to 20th	Night	9% 2 5% 25% 23% 35%	1566
	21st to end	Night	12% 2 6% 26% 25% 30%	1674
August	1st to 10th	Night	18% 2 5% 26% 26% 24%	1602
	11th to 20th	Night	11% 2 4 21% 31% 31%	1719
	21st to end	Night	11% 2 5% 25% 29% 28%	1980
September	1st to 10th	Night	9% 2 5% 17% 24% 43%	1800
	11th to 20th	Night	17% 4 7% 25% 29% 18%	1800
	21st to end	Night	13% 2 8% 19% 32% 26%	2048
October	1st to 10th	Night	18% 3 9% 18% 25% 27%	2160
	11th to 20th	Night	22% 5% 7% 21% 21% 24%	2160
	21st to end	Night	22% 4 8% 20% 26% 21%	2376
November	1st to 10th	Night	27% 4 10% 24% 19% 15%	2237
	11th to 20th	Night	30% 5% 10% 24% 22% 9%	2470
	21st to end	Night	28% 4 10% 20% 24% 14%	2604
December	1st to 10th	Night	37% 6% 9% 18% 17% 13%	2660
	11th to 20th	Night	53% 4 10% 14% 15% 5%	3276
	21st to end	Night	48% 7% 15% 15% 11% 4	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	24% 18% 23% 21% 12% 2	303
	11th to 20th	Day	16% 16% 25% 29% 12% 3	370
	21st to end	Day	15% 13% 28% 25% 16% 3	407
February	1st to 10th	Day	17% 18% 23% 24% 13% 4	370
	11th to 20th	Day	17% 22% 26% 24% 9% 1	408
	21st to end	Day	13% 19% 31% 25% 10% 1	382
March	1st to 10th	Day	18% 21% 31% 22% 7% 1	460
	11th to 20th	Day	17% 20% 28% 19% 13% 3	460
	21st to end	Day	14% 21% 34% 22% 7% 1	491
April	1st to 10th	Day	15% 19% 34% 21% 10% 2	420
	11th to 20th	Day	13% 20% 32% 23% 8% 3	412
	21st to end	Day	7% 22% 29% 26% 10% 5%	420
May	1st to 10th	Day	7% 15% 35% 28% 13% 2	423
	11th to 20th	Day	10% 15% 37% 24% 11% 2	448
	21st to end	Day	7% 14% 33% 28% 13% 4	485
June	1st to 10th	Day	6% 12% 32% 30% 16% 4	450
	11th to 20th	Day	2 12% 31% 37% 15% 3	450
	21st to end	Day	1 4 31% 38% 22% 4	450
July	1st to 10th	Day	2 4 22% 47% 22% 3	446
	11th to 20th	Day	1 1 18% 47% 29% 5%	444
	21st to end	Day	1 18% 46% 26% 8%	487
August	1st to 10th	Day	3 2 27% 43% 19% 6%	447
	11th to 20th	Day	1 1 23% 40% 27% 8%	437
	21st to end	Day	1 1 21% 43% 26% 7%	495
September	1st to 10th	Day	2 5% 17% 42% 27% 7%	450
	11th to 20th	Day	3 8% 26% 37% 20% 6%	450
	21st to end	Day	3 10% 21% 34% 27% 6%	450
October	1st to 10th	Day	2 10% 24% 34% 21% 8%	450
	11th to 20th	Day	6% 9% 21% 29% 26% 9%	450
	21st to end	Day	7% 9% 25% 30% 22% 7%	495
November	1st to 10th	Day	9% 12% 22% 26% 23% 7%	436
	11th to 20th	Day	5% 10% 20% 30% 26% 10%	270
	21st to end	Day	7% 9% 26% 29% 25% 4	205
December	1st to 10th	Day	8% 19% 21% 23% 24% 6%	180
	11th to 20th	Day	14% 17% 24% 21% 18% 7%	180
	21st to end	Day	19% 20% 25% 20% 14% 3	198
January	1st to 10th	Night	19% 8% 16% 29% 22% 6%	760
	11th to 20th	Night	15% 8% 15% 31% 23% 7%	760
	21st to end	Night	17% 7% 15% 32% 23% 5%	836
February	1st to 10th	Night	14% 9% 18% 32% 22% 4	760
	11th to 20th	Night	14% 11% 19% 31% 21% 5%	744
	21st to end	Night	14% 11% 22% 32% 18% 3	628
March	1st to 10th	Night	17% 11% 20% 28% 20% 3	760
	11th to 20th	Night	15% 11% 17% 30% 22% 5%	760
	21st to end	Night	13% 11% 25% 32% 17% 2	820
April	1st to 10th	Night	13% 9% 26% 30% 19% 3	720
	11th to 20th	Night	11% 14% 22% 29% 19% 5%	711
	21st to end	Night	6% 9% 29% 26% 22% 7%	720
May	1st to 10th	Night	6% 7% 26% 32% 24% 5%	661
	11th to 20th	Night	6% 5% 23% 32% 29% 6%	501
	21st to end	Night	5% 10% 23% 32% 26% 4	389
June	1st to 10th	Night	5% 4 24% 34% 28% 4	360
	11th to 20th	Night	1 4 18% 44% 31% 1	360
	21st to end	Night	2 3 13% 39% 38% 6%	360
July	1st to 10th	Night	1 2 12% 35% 46% 4	359
	11th to 20th	Night	1 5% 34% 46% 13%	522
	21st to end	Night	1 7% 30% 51% 11%	591
August	1st to 10th	Night	4 2 11% 32% 42% 9%	537
	11th to 20th	Night	1 1 12% 34% 45% 8%	651
	21st to end	Night	2 1 10% 32% 46% 10%	792
September	1st to 10th	Night	2 2 9% 33% 43% 11%	720
	11th to 20th	Night	4 3 13% 36% 37% 8%	720
	21st to end	Night	2 4 13% 28% 41% 12%	720
October	1st to 10th	Night	5% 3 14% 32% 36% 10%	720
	11th to 20th	Night	6% 4 12% 28% 40% 9%	720
	21st to end	Night	6% 6% 11% 31% 32% 14%	792
November	1st to 10th	Night	7% 5% 17% 27% 34% 9%	740
	11th to 20th	Night	9% 4 14% 33% 32% 7%	760
	21st to end	Night	10% 5% 15% 38% 26% 7%	760
December	1st to 10th	Night	13% 8% 19% 31% 24% 6%	760
	11th to 20th	Night	18% 9% 18% 30% 21% 4	760
	21st to end	Night	17% 14% 20% 29% 18% 3	836

Page generated at 2024-03-24 20:37:04. Version ac07

Copyright © 2024 Attilla Danko.