Tulsa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tulsa clear sky chart from 2003-08-01 to 2005-11-07.

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	16% 6% 5% 7% 42%	8707
	Night	14% 5% 7% 45%	8467
Transparency	Day	15% 15% 38% 26%	5202
	Night	14% 13% 36% 28% 7%	5393
Seeing	Day	9% 23% 31% 30% 5%	551
	Night	10% 30% 36% 21%	2629

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	26% 8% 5% 38%	550
	Night	22% 5% 5% 5% 37%	803
February	Day	27% 5% 5% 8% 32%	549
	Night	24% 6% 5% 5% 5% 7% 31%	707
March	Day	15% 6% 45%	682
	Night	13% 5% 7% 47%	682
April	Day	20% 5% 5% 5% 40%	718
	Night	15% 5% 5% 46%	601
May	Day	12% 5% 6% 5% 7% 43%	803
	Night	8% 5% 6% 10% 49%	550
June	Day	14% 5% 8% 5% 6% 8% 37%	780
	Night	5% 6% 6% 8% 15% 44%	537
July	Day	11% 7% 5% 5% 10% 43%	801
	Night	5% 6% 5% 9% 53%	558
August	Day	11% 8% 6% 7% 10% 39%	1187
	Night	7% 9% 5% 7% 11% 42%	855
September	Day	9% 6% 53%	977
	Night	10% 7% 56%	968
October	Day	20% 5% 7% 40%	624
	Night	18% 5% 6% 6% 40%	735
November	Day	27% 5% 40%	488
	Night	28% 42%	680
December	Day	12% 5% 5% 54%	548
	Night	11% 5% 59%	791

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	13% 20% 51% 14%	250
	Night	18% 17% 46% 17%	393
February	Day	12% 14% 52% 17%	256
	Night	16% 12% 44% 20% 5%	322
March	Day	13% 17% 41% 26%	393
	Night	12% 12% 38% 34%	383
April	Day	15% 7% 38% 37%	386
	Night	12% 14% 31% 35% 6%	345
May	Day	21% 15% 37% 22%	455
	Night	18% 25% 39% 14%	374
June	Day	20% 13% 34% 29%	415
	Night	31% 10% 25% 28%	365
July	Day	14% 15% 43% 22%	482
	Night	11% 12% 37% 28% 9%	379
August	Day	24% 23% 34% 14%	711
	Night	16% 21% 40% 18%	565
September	Day	9% 15% 32% 33% 8%	667
	Night	9% 10% 27% 39% 13%	699
October	Day	10% 15% 30% 37% 6%	540
	Night	11% 11% 29% 34% 12%	629
November	Day	14% 6% 28% 36% 14%	278
	Night	14% 8% 30% 35% 10%	397
December	Day	8% 12% 47% 25% 5%	369
	Night	6% 10% 48% 25% 8%	542

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	Night	18% 39% 34% 7%	250
February	Night	19% 37% 33% 9%	203
March	Night	16% 48% 30%	166
April	Day	19% 42% 29% 8%	47
	Night	13% 39% 35% 10%	158
May	Day	12% 37% 40% 7%	115
	Night	33% 54% 7%	172
June	Day	11% 27% 29% 27%	113
	Night	33% 32% 29%	174
July	Day	6% 15% 28% 43% 6%	115
	Night	16% 38% 40%	177
August	Day	12% 29% 45% 8%	156
	Night	10% 39% 41% 5%	265
September	Day	20% 20% 40% 20%	5
	Night	5% 13% 34% 42%	249
October	Night	10% 27% 34% 25%	315
November	Night	18% 38% 32% 11%	222
December	Night	12% 41% 33% 12%	278

Page generated at 2008-06-05 22:07:37. Version ab11