Columbia Scientific Balloon Facility
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Columbia Scientific Balloon Facility clear sky chart from 2005-11-06 to 2024-12-24.

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	12% 6% 2 6% 4 4 4 4 5% 7% 45%	101619
	Night	12% 6% 2 5% 3 3 3 3 5% 7% 51%	98586
Transparency	Day	35% 6% 11% 22% 19% 7%	105323
	Night	32% 5% 11% 21% 21% 10%	103009
Seeing	Day	13% 6% 20% 27% 25% 9%	15199
	Night	14% 6% 24% 35% 19% 2	25105

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	14% 9% 3 6% 3 3 3 2 4 6% 48%	2847
	11th to 20th	Day	18% 6% 2 4 2 3 2 3 4 6% 50%	2850
	21st to end	Day	24% 10% 3 6% 3 2 2 2 3 4 42%	3135
February	1st to 10th	Day	22% 10% 3 5% 4 3 3 2 3 6% 40%	1767
	11th to 20th	Day	22% 8% 2 5% 3 4 4 3 4 5% 41%	1849
	21st to end	Day	23% 6% 2 5% 3 3 3 2 4 4 46%	1687
March	1st to 10th	Day	18% 10% 3 7% 4 4 4 3 5% 7% 35%	3436
	11th to 20th	Day	19% 8% 3 6% 5% 5% 5% 3 6% 6% 36%	3480
	21st to end	Day	17% 9% 3 7% 4 4 4 3 5% 6% 38%	3814
April	1st to 10th	Day	15% 7% 2 6% 5% 4 4 3 6% 8% 40%	2090
	11th to 20th	Day	15% 7% 2 6% 5% 4 4 4 6% 7% 39%	2218
	21st to end	Day	12% 7% 2 6% 5% 4 4 3 6% 7% 45%	2280
May	1st to 10th	Day	20% 9% 3 8% 5% 5% 5% 4 6% 7% 30%	4042
	11th to 20th	Day	15% 6% 2 6% 4 4 4 3 4 6% 44%	4082
	21st to end	Day	13% 6% 2 7% 5% 5% 6% 5% 7% 9% 34%	4477
June	1st to 10th	Day	6% 5% 2 6% 5% 5% 6% 5% 7% 11% 43%	2470
	11th to 20th	Day	5% 5% 1 5% 4 5% 5% 5% 7% 11% 47%	2470
	21st to end	Day	5% 4 2 5% 6% 6% 6% 5% 7% 9% 45%	2470
July	1st to 10th	Day	8% 4 2 6% 4 5% 5% 5% 7% 11% 42%	4120
	11th to 20th	Day	4 4 2 4 5% 5% 5% 5% 6% 9% 52%	4120
	21st to end	Day	12% 8% 3 7% 6% 5% 5% 5% 6% 8% 35%	4465
August	1st to 10th	Day	2 1 1 2 2 2 2 3 5% 9% 71%	4104
	11th to 20th	Day	4 2 1 3 3 3 4 4 6% 10% 60%	3989
	21st to end	Day	5% 3 2 5% 5% 5% 6% 6% 8% 11% 45%	4125
September	1st to 10th	Day	8% 6% 2 6% 5% 5% 5% 3 5% 7% 48%	2090
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 4 6% 6% 46%	2090
	21st to end	Day	7% 5% 1 4 4 3 3 4 6% 8% 56%	2090
October	1st to 10th	Day	6% 3 1 4 3 3 3 4 4 6% 63%	1981
	11th to 20th	Day	12% 5% 1 4 3 3 3 2 4 5% 58%	1900
	21st to end	Day	14% 5% 2 4 3 3 3 2 3 4 58%	2090
November	1st to 10th	Day	14% 6% 2 5% 4 3 3 3 5% 7% 50%	1958
	11th to 20th	Day	12% 5% 2 4 4 3 4 3 4 5% 54%	2000
	21st to end	Day	17% 7% 3 5% 4 3 3 3 4 5% 46%	1820
December	1st to 10th	Day	16% 7% 2 6% 3 3 3 3 5% 5% 47%	1800
	11th to 20th	Day	18% 8% 3 5% 3 4 3 3 5% 5% 43%	2251
	21st to end	Day	15% 9% 3 8% 4 3 3 3 4 5% 43%	3162
January	1st to 10th	Night	15% 6% 2 4 2 2 2 2 4 6% 54%	4108
	11th to 20th	Night	17% 7% 1 3 2 2 3 2 3 4 57%	4120
	21st to end	Night	21% 10% 3 5% 3 2 3 2 3 5% 43%	4532
February	1st to 10th	Night	18% 7% 2 5% 3 3 3 3 4 4 47%	2428
	11th to 20th	Night	21% 7% 3 5% 3 3 2 2 4 5% 46%	2218
	21st to end	Night	20% 6% 2 5% 3 3 3 3 4 5% 46%	1765
March	1st to 10th	Night	20% 10% 3 6% 4 3 4 3 5% 5% 37%	3419
	11th to 20th	Night	17% 8% 3 6% 4 4 3 3 6% 7% 39%	3480
	21st to end	Night	14% 6% 3 6% 4 3 4 4 5% 6% 45%	3817
April	1st to 10th	Night	12% 5% 2 5% 4 4 5% 3 5% 7% 50%	2090
	11th to 20th	Night	13% 6% 2 5% 3 4 4 4 6% 7% 47%	1909
	21st to end	Night	11% 6% 2 5% 4 3 3 3 5% 6% 53%	1900
May	1st to 10th	Night	16% 9% 3 7% 3 4 3 3 5% 8% 38%	2856
	11th to 20th	Night	11% 7% 2 7% 4 4 4 4 5% 7% 46%	2823
	21st to end	Night	9% 6% 2 5% 4 5% 5% 4 6% 9% 45%	3090
June	1st to 10th	Night	5% 2 1 3 3 3 4 4 7% 9% 57%	1710
	11th to 20th	Night	4 2 1 3 2 3 3 3 5% 11% 63%	1710
	21st to end	Night	6% 3 1 4 4 3 4 5% 6% 10% 54%	1710
July	1st to 10th	Night	5% 3 2 5% 4 4 5% 4 8% 12% 48%	2850
	11th to 20th	Night	2 2 1 4 3 3 3 4 6% 10% 61%	2850
	21st to end	Night	9% 8% 2 7% 5% 4 5% 4 7% 10% 40%	3098
August	1st to 10th	Night	1 1 2 1 1 2 2 4 8% 77%	2836
	11th to 20th	Night	3 3 1 3 2 3 3 4 5% 11% 62%	2846
	21st to end	Night	4 3 1 4 3 4 5% 4 7% 11% 54%	3526
September	1st to 10th	Night	7% 5% 1 4 5% 4 4 4 6% 8% 51%	2090
	11th to 20th	Night	9% 5% 2 5% 4 4 3 3 5% 7% 53%	2090
	21st to end	Night	6% 4 1 5% 3 2 3 3 4 7% 62%	2090
October	1st to 10th	Night	5% 3 1 4 2 2 3 3 4 7% 65%	2178
	11th to 20th	Night	12% 4 1 3 3 2 3 3 4 5% 61%	2280
	21st to end	Night	13% 4 1 4 3 2 2 2 3 4 61%	2508
November	1st to 10th	Night	12% 5% 2 5% 3 4 2 2 4 5% 56%	2340
	11th to 20th	Night	9% 5% 2 5% 4 4 4 3 5% 5% 56%	2400
	21st to end	Night	16% 6% 2 5% 4 3 3 2 5% 4 50%	2575
December	1st to 10th	Night	16% 6% 2 5% 4 3 2 3 4 5% 49%	2600
	11th to 20th	Night	15% 8% 3 7% 4 4 3 2 3 5% 46%	3166
	21st to end	Night	16% 8% 2 4 3 3 2 3 3 4 51%	4578

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	37% 3 7% 20% 28% 5%	2848
	11th to 20th	Day	36% 4 6% 24% 25% 5%	2850
	21st to end	Day	47% 3 4 16% 20% 10%	3135
February	1st to 10th	Day	48% 2 6% 15% 20% 9%	1767
	11th to 20th	Day	47% 4 6% 15% 18% 9%	1859
	21st to end	Day	43% 5% 6% 15% 18% 13%	1687
March	1st to 10th	Day	47% 7% 9% 14% 19% 5%	3436
	11th to 20th	Day	48% 6% 8% 18% 16% 4	3480
	21st to end	Day	45% 6% 10% 16% 20% 3	3814
April	1st to 10th	Day	41% 6% 10% 19% 15% 9%	2090
	11th to 20th	Day	43% 7% 11% 13% 19% 8%	2218
	21st to end	Day	37% 6% 9% 19% 23% 5%	2280
May	1st to 10th	Day	50% 9% 12% 16% 10% 3	4080
	11th to 20th	Day	40% 6% 10% 19% 24% 1	4086
	21st to end	Day	40% 11% 15% 20% 12% 2	4489
June	1st to 10th	Day	32% 9% 17% 28% 13% 2	2470
	11th to 20th	Day	28% 9% 16% 28% 16% 4	2470
	21st to end	Day	31% 10% 14% 28% 15% 2	2470
July	1st to 10th	Day	32% 10% 25% 26% 7%	4056
	11th to 20th	Day	26% 8% 17% 33% 15% 1	4051
	21st to end	Day	44% 10% 15% 23% 8%	4325
August	1st to 10th	Day	12% 5% 13% 38% 30% 2	4090
	11th to 20th	Day	19% 7% 19% 42% 12% 1	4028
	21st to end	Day	29% 11% 21% 25% 13% 1	4124
September	1st to 10th	Day	35% 6% 13% 20% 17% 9%	2090
	11th to 20th	Day	36% 8% 14% 17% 16% 9%	2090
	21st to end	Day	26% 7% 10% 22% 22% 13%	2090
October	1st to 10th	Day	14% 3 6% 13% 22% 41%	3293
	11th to 20th	Day	19% 2 4 22% 30% 23%	3140
	21st to end	Day	25% 4 5% 22% 34% 10%	3428
November	1st to 10th	Day	35% 5% 9% 19% 23% 9%	1958
	11th to 20th	Day	33% 4 7% 18% 24% 13%	2000
	21st to end	Day	42% 5% 6% 18% 21% 9%	1820
December	1st to 10th	Day	39% 5% 10% 19% 21% 8%	1800
	11th to 20th	Day	42% 4 8% 15% 22% 9%	2249
	21st to end	Day	44% 4 6% 16% 22% 8%	3162
January	1st to 10th	Night	32% 4 6% 18% 30% 9%	4108
	11th to 20th	Night	33% 4 7% 16% 30% 11%	4120
	21st to end	Night	45% 4 5% 15% 21% 10%	4532
February	1st to 10th	Night	41% 4 7% 15% 18% 15%	2428
	11th to 20th	Night	43% 3 7% 14% 21% 11%	2218
	21st to end	Night	42% 4 8% 14% 17% 16%	1765
March	1st to 10th	Night	48% 5% 7% 14% 18% 7%	3419
	11th to 20th	Night	44% 7% 9% 16% 19% 5%	3480
	21st to end	Night	38% 6% 10% 16% 23% 7%	3817
April	1st to 10th	Night	34% 6% 10% 19% 18% 12%	2090
	11th to 20th	Night	35% 6% 12% 18% 17% 12%	1909
	21st to end	Night	33% 5% 11% 19% 26% 7%	1900
May	1st to 10th	Night	43% 8% 11% 21% 12% 4	2883
	11th to 20th	Night	37% 7% 11% 19% 23% 3	2824
	21st to end	Night	33% 10% 16% 26% 11% 3	3099
June	1st to 10th	Night	21% 9% 17% 33% 19% 2	1710
	11th to 20th	Night	16% 7% 18% 34% 20% 5%	1710
	21st to end	Night	24% 8% 15% 28% 22% 3	1710
July	1st to 10th	Night	27% 8% 27% 32% 6% 1	2805
	11th to 20th	Night	18% 8% 23% 35% 16% 1	2796
	21st to end	Night	38% 9% 19% 25% 8%	2999
August	1st to 10th	Night	8% 4 15% 33% 35% 5%	2826
	11th to 20th	Night	17% 6% 20% 44% 11% 3	2873
	21st to end	Night	24% 8% 22% 28% 16% 2	3526
September	1st to 10th	Night	30% 7% 15% 22% 17% 10%	2090
	11th to 20th	Night	32% 7% 15% 19% 19% 9%	2090
	21st to end	Night	23% 5% 12% 21% 27% 13%	2090
October	1st to 10th	Night	13% 2 7% 15% 18% 45%	3633
	11th to 20th	Night	16% 2 4 19% 33% 26%	3779
	21st to end	Night	23% 4 4 18% 34% 17%	4120
November	1st to 10th	Night	31% 4 9% 18% 25% 12%	2340
	11th to 20th	Night	31% 5% 8% 18% 24% 15%	2400
	21st to end	Night	38% 4 8% 17% 23% 11%	2575
December	1st to 10th	Night	37% 5% 8% 19% 22% 9%	2600
	11th to 20th	Night	41% 4 6% 14% 22% 13%	3167
	21st to end	Night	38% 4 6% 14% 28% 11%	4578

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	21% 14% 33% 23% 8% 1	270
	11th to 20th	Day	21% 16% 33% 20% 9%	270
	21st to end	Day	23% 11% 42% 18% 7%	297
February	1st to 10th	Day	26% 15% 32% 21% 6%	270
	11th to 20th	Day	32% 17% 31% 15% 4	270
	21st to end	Day	30% 16% 41% 11% 3	225
March	1st to 10th	Day	23% 13% 39% 17% 8%	270
	11th to 20th	Day	20% 16% 39% 20% 5% 1	270
	21st to end	Day	20% 14% 42% 17% 6% 1	297
April	1st to 10th	Day	23% 11% 41% 20% 4	270
	11th to 20th	Day	22% 14% 28% 25% 11% 1	416
	21st to end	Day	15% 9% 34% 30% 10% 2	460
May	1st to 10th	Day	15% 11% 32% 32% 9% 1	626
	11th to 20th	Day	13% 5% 25% 34% 19% 4	675
	21st to end	Day	13% 5% 22% 33% 22% 5%	734
June	1st to 10th	Day	7% 3 10% 37% 30% 13%	680
	11th to 20th	Day	5% 2 13% 38% 32% 10%	680
	21st to end	Day	5% 2 12% 30% 34% 16%	680
July	1st to 10th	Day	8% 2 6% 30% 35% 19%	671
	11th to 20th	Day	4 1 5% 28% 46% 16%	668
	21st to end	Day	6% 1 5% 28% 44% 16%	739
August	1st to 10th	Day	4 3 23% 52% 18%	676
	11th to 20th	Day	6% 2 3 23% 51% 15%	639
	21st to end	Day	7% 1 4 16% 42% 30%	510
September	1st to 10th	Day	6% 7% 24% 35% 27%	300
	11th to 20th	Day	6% 2 8% 28% 34% 22%	300
	21st to end	Day	12% 2 10% 26% 32% 18%	300
October	1st to 10th	Day	3 1 17% 33% 35% 11%	300
	11th to 20th	Day	10% 4 27% 32% 21% 6%	300
	21st to end	Day	20% 10% 24% 25% 17% 5%	330
November	1st to 10th	Day	18% 6% 24% 33% 16% 3	300
	11th to 20th	Day	17% 9% 26% 31% 14% 3	300
	21st to end	Day	21% 11% 33% 21% 13% 1	300
December	1st to 10th	Day	20% 9% 36% 19% 13% 3	300
	11th to 20th	Day	28% 14% 27% 24% 6% 1	300
	21st to end	Day	19% 12% 39% 20% 8% 1	306
January	1st to 10th	Night	19% 9% 31% 32% 8%	950
	11th to 20th	Night	23% 10% 32% 28% 7%	950
	21st to end	Night	20% 9% 34% 32% 5%	1045
February	1st to 10th	Night	22% 10% 33% 30% 5%	908
	11th to 20th	Night	25% 11% 36% 25% 3	744
	21st to end	Night	23% 13% 39% 22% 3	509
March	1st to 10th	Night	21% 11% 34% 28% 6%	570
	11th to 20th	Night	18% 10% 37% 28% 7%	570
	21st to end	Night	14% 11% 40% 29% 6%	627
April	1st to 10th	Night	13% 9% 42% 29% 7%	570
	11th to 20th	Night	15% 11% 37% 27% 10%	563
	21st to end	Night	14% 8% 40% 27% 10% 1	570
May	1st to 10th	Night	11% 7% 39% 33% 9% 1	570
	11th to 20th	Night	13% 5% 28% 37% 15% 1	561
	21st to end	Night	8% 4 25% 41% 20% 2	617
June	1st to 10th	Night	6% 1 13% 42% 34% 4	570
	11th to 20th	Night	4 2 16% 51% 24% 3	570
	21st to end	Night	6% 1 12% 36% 38% 6%	570
July	1st to 10th	Night	3 2 8% 42% 38% 7%	555
	11th to 20th	Night	3 1 5% 40% 45% 6%	552
	21st to end	Night	5% 1 5% 41% 44% 4	624
August	1st to 10th	Night	2 4 40% 47% 7%	567
	11th to 20th	Night	8% 2 5% 39% 40% 7%	564
	21st to end	Night	5% 1 5% 35% 47% 7%	627
September	1st to 10th	Night	9% 1 6% 36% 42% 7%	570
	11th to 20th	Night	11% 1 5% 35% 43% 5%	570
	21st to end	Night	8% 1 9% 37% 39% 5%	570
October	1st to 10th	Night	6% 3 12% 46% 29% 5%	658
	11th to 20th	Night	14% 3 22% 40% 19% 3	760
	21st to end	Night	15% 6% 25% 33% 17% 2	836
November	1st to 10th	Night	14% 3 25% 37% 19% 1	780
	11th to 20th	Night	11% 9% 27% 40% 14%	800
	21st to end	Night	19% 9% 27% 30% 13% 1	975
December	1st to 10th	Night	19% 8% 28% 36% 9% 1	1000
	11th to 20th	Night	22% 8% 28% 36% 6%	1000
	21st to end	Night	22% 8% 31% 32% 8%	1063

Page generated at 2024-12-21 03:13:52. Version ac07

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