Jacksonville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jacksonville 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	15% 5% 5% 5% 5% 8% 5% 7% 8% 30%	8688
	Night	15% 7% 5% 5% 8% 35%	8484
Transparency	Day	25% 17% 25% 23% 8%	4194
	Night	20% 16% 27% 25% 9%	4565
Seeing	Day	5% 15% 20% 34% 24%	579
	Night	7% 21% 31% 31% 7%	2718

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	14% 6% 5% 5% 5% 7% 38%	551
	Night	13% 5% 5% 6% 7% 42%	802
February	Day	28% 5% 5% 6% 8% 8% 6% 19%	577
	Night	32% 5% 5% 6% 5% 28%	676
March	Day	16% 6% 6% 46%	682
	Night	13% 6% 5% 6% 6% 43%	682
April	Day	9% 5% 5% 5% 54%	692
	Night	7% 8% 59%	629
May	Day	10% 6% 6% 8% 10% 40%	802
	Night	8% 5% 5% 7% 9% 48%	551
June	Day	19% 6% 5% 7% 9% 5% 11% 6% 7% 9% 12%	780
	Night	21% 6% 7% 12% 9% 6% 8% 15%	537
July	Day	10% 6% 8% 6% 12% 8% 9% 13% 16%	801
	Night	5% 7% 5% 7% 12% 8% 6% 10% 25%	558
August	Day	14% 8% 6% 8% 6% 10% 8% 8% 8% 15%	1143
	Night	16% 5% 8% 6% 6% 7% 5% 8% 10% 18%	896
September	Day	23% 6% 6% 5% 8% 5% 6% 8% 20%	971
	Night	22% 5% 5% 6% 7% 5% 8% 25%	975
October	Day	14% 5% 6% 6% 7% 6% 6% 8% 30%	634
	Night	13% 6% 8% 6% 8% 36%	728
November	Day	8% 6% 11% 46%	508
	Night	10% 7% 6% 5% 8% 46%	659
December	Day	12% 5% 6% 5% 6% 5% 42%	547
	Night	10% 6% 6% 7% 46%	791

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	20% 17% 28% 31%	281
	Night	13% 20% 28% 28% 9%	474
February	Day	16% 14% 30% 34%	205
	Night	21% 12% 20% 40%	254
March	Day	14% 9% 24% 36% 15%	388
	Night	23% 7% 29% 31% 8%	389
April	Day	11% 10% 22% 38% 16%	471
	Night	7% 8% 23% 40% 19%	453
May	Day	27% 16% 34% 17%	487
	Night	23% 20% 31% 21%	388
June	Day	71% 18% 8%	199
	Night	59% 19% 19%	149
July	Day	47% 25% 25%	300
	Night	28% 34% 28% 8%	235
August	Day	45% 33% 16% 5%	337
	Night	48% 22% 27%	295
September	Day	30% 21% 22% 17% 6%	373
	Night	25% 18% 29% 21% 5%	396
October	Day	12% 20% 24% 28% 14%	462
	Night	16% 20% 21% 24% 17%	569
November	Day	17% 11% 28% 34% 9%	388
	Night	12% 9% 33% 34% 9%	475
December	Day	13% 11% 30% 21% 23%	303
	Night	10% 12% 28% 29% 19%	488

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	13% 32% 34% 17%	223
February	Day	50% 50%	4
	Night	19% 41% 29% 9%	163
March	Day	10% 27% 34% 23%	55
	Night	9% 33% 42% 13%	218
April	Day	5% 28% 19% 35% 10%	56
	Night	9% 33% 38% 17%	227
May	Day	13% 18% 34% 32%	58
	Night	11% 40% 42%	176
June	Day	5% 9% 22% 35% 27%	54
	Night	8% 31% 42% 14%	151
July	Day	9% 8% 36% 44%	61
	Night	7% 15% 55% 20%	180
August	Day	5% 12% 31% 45%	88
	Night	7% 15% 45% 28%	283
September	Day	5% 16% 27% 32% 18%	80
	Night	7% 18% 30% 37% 5%	303
October	Day	18% 22% 39% 14%	83
	Night	6% 14% 39% 35%	328
November	Day	12% 7% 20% 45% 15%	40
	Night	9% 19% 26% 39% 6%	241
December	Night	9% 31% 34% 23%	225

Page generated at 2008-09-30 05:40:53. Version ab11