Tunnel Ridge Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tunnel Ridge Road clear sky chart from 2005-11-06 to 2024-11-12.

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	15% 9% 3 7% 4 4 4 4 5% 7% 36%	101153
	Night	15% 9% 3 7% 4 4 4 3 5% 7% 39%	98006
Transparency	Day	44% 6% 11% 22% 14% 2	104897
	Night	43% 6% 10% 22% 16% 3	102400
Seeing	Day	20% 12% 25% 22% 15% 6%	14845
	Night	19% 10% 24% 29% 17% 2	24890

By Month

Percentage Cloud Cover SE (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	15% 18% 6% 10% 4 4 4 3 4 7% 23%	2836
	11th to 20th	Day	19% 15% 7% 14% 4 6% 3 2 3 3 23%	2840
	21st to end	Day	24% 18% 7% 7% 3 3 3 2 4 5% 24%	3124
February	1st to 10th	Day	19% 13% 5% 11% 4 4 4 3 4 5% 29%	1801
	11th to 20th	Day	22% 10% 5% 7% 5% 4 4 3 4 6% 31%	1848
	21st to end	Day	21% 14% 4 7% 5% 4 4 3 4 4 31%	1570
March	1st to 10th	Day	23% 14% 3 7% 3 3 3 3 4 6% 30%	3234
	11th to 20th	Day	15% 7% 2 6% 3 3 4 3 6% 6% 44%	3480
	21st to end	Day	17% 8% 2 7% 4 4 4 4 6% 6% 38%	3815
April	1st to 10th	Day	14% 9% 3 7% 4 4 4 4 5% 6% 38%	2156
	11th to 20th	Day	16% 8% 3 6% 4 5% 4 3 4 6% 40%	2323
	21st to end	Day	17% 7% 3 7% 5% 5% 5% 4 5% 7% 36%	2470
May	1st to 10th	Day	21% 9% 3 8% 5% 5% 5% 5% 5% 7% 28%	4082
	11th to 20th	Day	19% 8% 3 7% 5% 4 4 3 5% 6% 35%	4081
	21st to end	Day	11% 6% 2 6% 5% 6% 7% 5% 8% 9% 35%	4476
June	1st to 10th	Day	12% 6% 3 6% 5% 6% 5% 5% 6% 9% 39%	2470
	11th to 20th	Day	8% 5% 2 7% 5% 4 5% 7% 7% 9% 41%	2470
	21st to end	Day	10% 5% 2 6% 5% 6% 5% 5% 6% 9% 39%	2470
July	1st to 10th	Day	9% 6% 2 8% 5% 5% 5% 4 7% 9% 39%	4120
	11th to 20th	Day	9% 5% 3 6% 5% 5% 6% 5% 7% 11% 39%	4120
	21st to end	Day	19% 10% 4 9% 6% 6% 6% 4 6% 7% 22%	4466
August	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 4 7% 10% 41%	4104
	11th to 20th	Day	10% 7% 2 6% 5% 5% 5% 5% 7% 11% 37%	4044
	21st to end	Day	6% 4 2 4 4 5% 5% 4 6% 8% 53%	4251
September	1st to 10th	Day	13% 6% 3 6% 4 4 5% 3 5% 8% 44%	2109
	11th to 20th	Day	13% 5% 2 7% 4 4 4 3 6% 8% 44%	2090
	21st to end	Day	19% 5% 2 6% 4 3 4 4 4 7% 43%	2090
October	1st to 10th	Day	11% 5% 2 5% 4 3 3 3 5% 7% 51%	2090
	11th to 20th	Day	14% 7% 2 6% 3 4 3 3 4 6% 49%	1905
	21st to end	Day	19% 8% 2 5% 3 3 3 2 4 7% 43%	2040
November	1st to 10th	Day	13% 5% 2 5% 4 4 3 3 4 5% 52%	1762
	11th to 20th	Day	16% 10% 3 6% 3 4 3 3 4 6% 42%	1719
	21st to end	Day	16% 10% 3 6% 4 4 4 3 5% 5% 39%	1710
December	1st to 10th	Day	23% 14% 3 6% 5% 4 4 3 5% 5% 28%	1710
	11th to 20th	Day	17% 14% 4 7% 4 4 4 3 5% 5% 32%	2153
	21st to end	Day	18% 17% 4 9% 6% 5% 5% 4 5% 7% 22%	3124
January	1st to 10th	Night	16% 18% 6% 9% 5% 5% 5% 3 5% 5% 24%	4109
	11th to 20th	Night	20% 14% 5% 10% 6% 4 3 2 3 4 29%	4120
	21st to end	Night	23% 15% 6% 7% 4 3 3 3 3 5% 29%	4532
February	1st to 10th	Night	19% 12% 4 9% 4 4 4 4 4 5% 30%	2375
	11th to 20th	Night	22% 11% 4 8% 4 4 4 3 5% 5% 32%	2218
	21st to end	Night	23% 13% 3 8% 5% 4 3 3 5% 4 29%	1884
March	1st to 10th	Night	22% 14% 2 6% 4 4 4 3 4 6% 32%	3619
	11th to 20th	Night	13% 8% 2 5% 4 3 4 3 5% 6% 47%	3480
	21st to end	Night	13% 7% 3 6% 5% 5% 5% 4 6% 7% 39%	3817
April	1st to 10th	Night	13% 7% 2 7% 4 4 4 3 5% 8% 43%	2038
	11th to 20th	Night	14% 7% 2 6% 4 4 4 3 5% 7% 45%	1806
	21st to end	Night	16% 8% 3 6% 4 4 3 4 5% 6% 41%	1710
May	1st to 10th	Night	21% 11% 3 8% 5% 5% 4 4 5% 6% 28%	2813
	11th to 20th	Night	19% 7% 3 5% 4 3 4 4 6% 8% 38%	2812
	21st to end	Night	10% 5% 2 6% 5% 5% 5% 4 6% 9% 43%	3079
June	1st to 10th	Night	8% 5% 2 6% 4 4 4 5% 8% 10% 43%	1710
	11th to 20th	Night	5% 4 2 6% 4 5% 5% 5% 9% 11% 45%	1710
	21st to end	Night	11% 4 1 5% 4 5% 5% 6% 8% 11% 40%	1710
July	1st to 10th	Night	6% 4 3 8% 4 6% 5% 4 8% 10% 42%	2840
	11th to 20th	Night	6% 5% 2 5% 4 4 5% 4 7% 10% 48%	2840
	21st to end	Night	14% 9% 3 8% 6% 5% 5% 4 6% 9% 31%	3087
August	1st to 10th	Night	8% 5% 2 8% 5% 4 4 4 7% 9% 45%	2825
	11th to 20th	Night	9% 6% 3 7% 4 5% 5% 4 6% 9% 43%	2785
	21st to end	Night	5% 2 1 4 3 3 4 3 6% 8% 61%	3402
September	1st to 10th	Night	12% 4 2 5% 5% 4 5% 4 5% 8% 48%	2052
	11th to 20th	Night	10% 6% 2 6% 4 4 4 3 5% 7% 50%	2090
	21st to end	Night	12% 7% 2 6% 3 4 3 3 4 6% 49%	2090
October	1st to 10th	Night	11% 5% 1 5% 4 3 4 3 4 8% 53%	2090
	11th to 20th	Night	14% 6% 2 5% 4 3 3 3 3 7% 49%	2274
	21st to end	Night	17% 8% 2 5% 4 3 3 3 5% 6% 44%	2555
November	1st to 10th	Night	12% 7% 2 6% 3 3 3 4 4 6% 50%	2536
	11th to 20th	Night	15% 9% 3 5% 4 3 3 3 5% 5% 44%	2484
	21st to end	Night	17% 11% 2 5% 4 3 4 4 4 5% 41%	2470
December	1st to 10th	Night	21% 13% 4 8% 4 4 3 3 4 5% 30%	2470
	11th to 20th	Night	18% 12% 5% 10% 4 3 3 3 4 6% 33%	3042
	21st to end	Night	18% 16% 4 9% 6% 5% 5% 4 5% 6% 20%	4532

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	59% 6% 10% 16% 9% 1	2837
	11th to 20th	Day	66% 4 6% 17% 6%	2840
	21st to end	Day	63% 4 7% 21% 5% 1	3124
February	1st to 10th	Day	57% 5% 7% 19% 11% 1	1801
	11th to 20th	Day	56% 3 8% 20% 10% 2	1858
	21st to end	Day	57% 4 8% 17% 11% 3	1570
March	1st to 10th	Day	55% 4 9% 17% 11% 4	3234
	11th to 20th	Day	39% 6% 11% 24% 18% 2	3480
	21st to end	Day	44% 7% 10% 27% 11% 1	3815
April	1st to 10th	Day	44% 6% 11% 22% 13% 3	2156
	11th to 20th	Day	44% 5% 8% 21% 17% 5%	2323
	21st to end	Day	46% 7% 11% 23% 11% 2	2470
May	1st to 10th	Day	53% 8% 10% 20% 8% 1	4120
	11th to 20th	Day	49% 8% 10% 22% 11%	4085
	21st to end	Day	38% 11% 14% 19% 16% 2	4489
June	1st to 10th	Day	40% 9% 11% 24% 15% 1	2470
	11th to 20th	Day	35% 11% 14% 20% 17% 2	2470
	21st to end	Day	38% 9% 14% 18% 16% 3	2470
July	1st to 10th	Day	40% 8% 17% 22% 13% 1	4055
	11th to 20th	Day	36% 8% 12% 33% 9% 2	4051
	21st to end	Day	58% 7% 10% 14% 9% 1	4324
August	1st to 10th	Day	36% 8% 14% 30% 11% 1	4091
	11th to 20th	Day	38% 8% 11% 28% 12% 2	4083
	21st to end	Day	28% 7% 14% 32% 17% 2	4250
September	1st to 10th	Day	38% 7% 11% 21% 18% 5%	2109
	11th to 20th	Day	37% 6% 12% 22% 19% 3	2090
	21st to end	Day	40% 6% 10% 22% 20% 2	2090
October	1st to 10th	Day	24% 5% 8% 22% 38% 3	3480
	11th to 20th	Day	26% 3 9% 27% 32% 2	3145
	21st to end	Day	31% 3 9% 29% 19% 8%	3342
November	1st to 10th	Day	35% 5% 8% 25% 23% 4	1762
	11th to 20th	Day	44% 3 8% 23% 19% 4	1719
	21st to end	Day	46% 5% 8% 21% 17% 3	1710
December	1st to 10th	Day	57% 5% 9% 20% 7% 1	1710
	11th to 20th	Day	52% 6% 10% 17% 15% 1	2150
	21st to end	Day	60% 7% 11% 17% 5% 1	3124
January	1st to 10th	Night	61% 6% 8% 16% 8% 1	4109
	11th to 20th	Night	60% 4 7% 19% 9% 2	4120
	21st to end	Night	59% 4 8% 19% 9% 1	4532
February	1st to 10th	Night	56% 4 11% 19% 9% 1	2375
	11th to 20th	Night	55% 4 7% 19% 12% 2	2219
	21st to end	Night	58% 5% 9% 14% 11% 3	1884
March	1st to 10th	Night	54% 5% 7% 20% 12% 2	3619
	11th to 20th	Night	37% 5% 10% 29% 16% 4	3480
	21st to end	Night	41% 7% 11% 23% 16% 1	3817
April	1st to 10th	Night	39% 6% 12% 22% 18% 3	2038
	11th to 20th	Night	38% 7% 9% 21% 18% 7%	1806
	21st to end	Night	44% 6% 12% 23% 14% 2	1710
May	1st to 10th	Night	53% 9% 10% 19% 8% 2	2840
	11th to 20th	Night	44% 8% 14% 24% 9% 1	2813
	21st to end	Night	33% 10% 14% 23% 17% 3	3087
June	1st to 10th	Night	31% 10% 16% 23% 17% 3	1710
	11th to 20th	Night	29% 10% 18% 22% 19% 3	1710
	21st to end	Night	34% 10% 15% 21% 15% 5%	1710
July	1st to 10th	Night	35% 9% 14% 25% 15% 2	2795
	11th to 20th	Night	30% 8% 15% 29% 16% 3	2786
	21st to end	Night	50% 8% 10% 20% 12% 1	2988
August	1st to 10th	Night	34% 7% 15% 27% 15% 1	2814
	11th to 20th	Night	37% 7% 13% 29% 14% 1	2812
	21st to end	Night	21% 6% 15% 33% 21% 4	3402
September	1st to 10th	Night	33% 8% 12% 21% 19% 7%	2052
	11th to 20th	Night	34% 7% 11% 22% 24% 3	2090
	21st to end	Night	36% 5% 10% 22% 24% 2	2090
October	1st to 10th	Night	26% 5% 8% 22% 36% 3	3480
	11th to 20th	Night	25% 3 7% 25% 33% 6%	3773
	21st to end	Night	29% 4 8% 23% 28% 8%	4203
November	1st to 10th	Night	36% 4 8% 25% 23% 4	2536
	11th to 20th	Night	42% 4 8% 18% 22% 5%	2484
	21st to end	Night	45% 4 9% 25% 16% 2	2470
December	1st to 10th	Night	56% 6% 9% 18% 10% 1	2470
	11th to 20th	Night	53% 4 8% 21% 13% 1	3044
	21st to end	Night	60% 8% 10% 14% 7%	4532

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	30% 22% 30% 14% 4 1	270
	11th to 20th	Day	36% 24% 27% 11% 2	270
	21st to end	Day	31% 24% 30% 12% 2	297
February	1st to 10th	Day	31% 23% 29% 12% 4	270
	11th to 20th	Day	41% 22% 28% 6% 1 1	270
	21st to end	Day	37% 23% 31% 8%	225
March	1st to 10th	Day	31% 21% 32% 11% 5%	332
	11th to 20th	Day	26% 23% 29% 17% 4	460
	21st to end	Day	31% 19% 28% 16% 6%	506
April	1st to 10th	Day	25% 19% 28% 19% 9% 1	460
	11th to 20th	Day	23% 16% 30% 17% 11% 2	452
	21st to end	Day	23% 17% 32% 19% 8% 3	460
May	1st to 10th	Day	25% 14% 30% 17% 10% 4	463
	11th to 20th	Day	18% 12% 25% 25% 13% 6%	487
	21st to end	Day	15% 8% 24% 25% 18% 11%	529
June	1st to 10th	Day	14% 6% 23% 27% 19% 10%	490
	11th to 20th	Day	10% 7% 21% 33% 21% 8%	490
	21st to end	Day	11% 6% 26% 28% 18% 11%	490
July	1st to 10th	Day	15% 5% 18% 22% 23% 18%	485
	11th to 20th	Day	10% 4 18% 31% 23% 14%	484
	21st to end	Day	16% 4 17% 28% 22% 12%	532
August	1st to 10th	Day	14% 3 17% 27% 25% 14%	486
	11th to 20th	Day	15% 5% 19% 27% 22% 12%	479
	21st to end	Day	9% 4 12% 31% 26% 18%	539
September	1st to 10th	Day	13% 4 17% 22% 31% 13%	490
	11th to 20th	Day	14% 5% 12% 28% 29% 13%	490
	21st to end	Day	22% 9% 18% 24% 22% 6%	490
October	1st to 10th	Day	12% 6% 21% 31% 23% 7%	490
	11th to 20th	Day	15% 13% 28% 24% 15% 5%	490
	21st to end	Day	23% 11% 31% 24% 10% 1	489
November	1st to 10th	Day	18% 12% 33% 26% 8% 2	300
	11th to 20th	Day	24% 16% 33% 21% 6% 1	273
	21st to end	Day	23% 15% 37% 19% 6% 1	270
December	1st to 10th	Day	29% 21% 28% 17% 4	270
	11th to 20th	Day	23% 22% 34% 13% 8%	270
	21st to end	Day	30% 22% 35% 9% 4	297
January	1st to 10th	Night	25% 19% 31% 21% 4	760
	11th to 20th	Night	33% 15% 30% 19% 4	760
	21st to end	Night	23% 18% 35% 22% 2	836
February	1st to 10th	Night	27% 14% 33% 23% 3	760
	11th to 20th	Night	30% 17% 33% 19% 2	743
	21st to end	Night	31% 15% 34% 18% 1	628
March	1st to 10th	Night	26% 14% 30% 26% 4	760
	11th to 20th	Night	25% 16% 31% 22% 7%	760
	21st to end	Night	20% 14% 32% 26% 7%	836
April	1st to 10th	Night	17% 16% 30% 29% 8%	708
	11th to 20th	Night	17% 14% 27% 29% 12% 1	563
	21st to end	Night	20% 8% 35% 27% 9% 1	570
May	1st to 10th	Night	20% 9% 27% 27% 15% 2	570
	11th to 20th	Night	17% 7% 20% 35% 18% 2	561
	21st to end	Night	9% 4 18% 35% 29% 5%	617
June	1st to 10th	Night	9% 4 19% 40% 26% 3	570
	11th to 20th	Night	6% 2 15% 41% 31% 5%	570
	21st to end	Night	11% 3 17% 36% 30% 3	570
July	1st to 10th	Night	10% 2 12% 31% 35% 10%	555
	11th to 20th	Night	7% 1 12% 33% 43% 5%	552
	21st to end	Night	12% 4 10% 32% 39% 5%	624
August	1st to 10th	Night	10% 2 9% 34% 38% 7%	567
	11th to 20th	Night	9% 3 9% 36% 34% 9%	564
	21st to end	Night	7% 3 8% 33% 41% 8%	627
September	1st to 10th	Night	12% 2 10% 33% 38% 5%	722
	11th to 20th	Night	11% 3 14% 28% 39% 5%	760
	21st to end	Night	16% 4 18% 32% 28% 3	760
October	1st to 10th	Night	12% 5% 18% 31% 29% 4	760
	11th to 20th	Night	18% 8% 24% 32% 17% 2	760
	21st to end	Night	20% 10% 26% 29% 14% 1	836
November	1st to 10th	Night	17% 8% 25% 33% 16% 2	780
	11th to 20th	Night	20% 13% 26% 31% 9% 1	765
	21st to end	Night	23% 11% 24% 32% 10% 1	760
December	1st to 10th	Night	29% 14% 27% 26% 4	760
	11th to 20th	Night	23% 13% 30% 27% 6% 1	760
	21st to end	Night	30% 13% 28% 25% 3	836

Page generated at 2024-11-08 22:45:39. Version ac07

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