Kennedy Meadows
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kennedy Meadows clear sky chart from 2005-11-05 to 2008-11-27.

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% 69%	12282
	Night	7% 71%	12146
Transparency	Day	11% 20% 28% 29%	10949
	Night	12% 22% 30% 24%	10917
Seeing	Day	26% 42% 26%	774
	Night	10% 26% 31% 23% 6%	3893

By Month

Percentage Cloud Cover
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month		Occurrence of each Forecast	Data Points
January	Day	6% 10% 61%	796
	Night	5% 7% 64%	1239
February	Day	6% 5% 8% 13% 51%	809
	Night	5% 6% 10% 59%	970
March	Day	5% 8% 6% 10% 57%	1000
	Night	6% 5% 5% 8% 60%	1040
April	Day	7% 65%	1077
	Night	7% 70%	899
May	Day	7% 70%	1200
	Night	8% 73%	846
June	Day	6% 79%	1258
	Night	7% 79%	721
July	Day	5% 5% 6% 63%	1274
	Night	6% 70%	767
August	Day	83%	1108
	Night	87%	929
September	Day	82%	1025
	Night	86%	950
October	Day	77%	941
	Night	80%	1090
November	Day	7% 69%	1003
	Night	9% 69%	1443
December	Day	6% 6% 13% 60%	791
	Night	5% 5% 5% 11% 61%	1252

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	6% 21% 30% 26% 5%	716
	Night	5% 19% 19% 34% 10%	1151
February	Day	6% 21% 37% 19% 5%	696
	Night	6% 23% 31% 23% 8%	846
March	Day	10% 22% 28% 23% 11%	859
	Night	6% 19% 30% 26% 12%	881
April	Day	18% 30% 30% 12%	913
	Night	7% 14% 30% 35% 10%	773
May	Day	7% 24% 40% 16%	1102
	Night	10% 28% 40% 13%	785
June	Day	11% 30% 51%	1188
	Night	15% 29% 48%	670
July	Day	5% 7% 9% 16% 52%	848
	Night	7% 12% 17% 53%	515
August	Day	23% 63%	1094
	Night	7% 24% 60%	913
September	Day	8% 31% 50%	1013
	Night	9% 35% 47%	933
October	Day	16% 38% 32%	897
	Night	18% 38% 31%	1035
November	Day	5% 13% 29% 27% 15%	937
	Night	5% 15% 26% 30% 15%	1346
December	Day	11% 22% 30% 23% 8%	686
	Night	11% 22% 29% 23% 7%	1069

Seeing (when cloud cover <= 80%)
Color Meanings: Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month		Occurrence of each Forecast	Data Points
January	Day	40% 32% 13%	37
	Night	18% 28% 30% 14%	359
February	Day	27% 36% 26%	73
	Night	11% 28% 28% 19% 8%	311
March	Day	38% 44% 11%	84
	Night	19% 37% 26% 11% 5%	362
April	Day	49% 34% 12%	75
	Night	17% 39% 23% 15%	347
May	Day	30% 42% 22%	88
	Night	14% 25% 37% 17%	282
June	Day	20% 51% 25%	87
	Night	25% 43% 22%	169
July	Day	10% 41% 46%	79
	Night	10% 48% 34% 6%	187
August	Day	10% 60% 29%	88
	Night	13% 37% 38% 9%	356
September	Day	17% 32% 45%	86
	Night	15% 23% 40% 15%	350
October	Day	28% 42% 22%	77
	Night	9% 25% 28% 25% 9%	364
November	Night	8% 22% 33% 24% 8%	441
December	Night	13% 35% 27% 18% 5%	365

Page generated at 2008-11-27 10:47:44. Version ab11