Tampa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tampa 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	8% 5% 6% 8% 6% 7% 10% 35%	12258
	Night	8% 5% 6% 5% 6% 9% 42%	12173
Transparency	Day	11% 16% 21% 18% 7%	9011
	Night	9% 18% 24% 18% 7%	9320
Seeing	Day	10% 23% 30% 28%	764
	Night	17% 38% 27% 8%	3848

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	11% 6% 5% 7% 5% 6% 5% 9% 35%	856
	Night	11% 6% 5% 6% 5% 6% 9% 36%	1183
February	Day	9% 5% 5% 5% 9% 45%	816
	Night	11% 7% 51%	963
March	Day	6% 8% 8% 51%	1022
	Night	5% 8% 55%	1020
April	Day	6% 6% 5% 7% 12% 49%	1015
	Night	6% 5% 5% 9% 54%	962
May	Day	5% 5% 9% 6% 7% 10% 43%	1208
	Night	5% 5% 8% 10% 54%	837
June	Day	10% 7% 7% 10% 7% 8% 12% 21%	1170
	Night	8% 6% 6% 7% 6% 15% 34%	810
July	Day	8% 6% 5% 8% 10% 6% 14% 8% 7% 10% 14%	1209
	Night	8% 6% 6% 6% 5% 9% 8% 9% 13% 22%	834
August	Day	8% 5% 7% 7% 7% 10% 10% 9% 11% 18%	1097
	Night	7% 6% 7% 6% 7% 9% 10% 31%	931
September	Day	5% 5% 7% 7% 5% 9% 10% 8% 11% 23%	987
	Night	5% 5% 7% 5% 7% 7% 8% 11% 31%	990
October	Day	11% 5% 6% 5% 7% 6% 5% 9% 34%	959
	Night	12% 8% 5% 6% 5% 5% 8% 38%	1074
November	Day	6% 5% 5% 7% 51%	1082
	Night	5% 5% 6% 5% 5% 8% 49%	1361
December	Day	10% 5% 5% 5% 6% 5% 6% 8% 37%	837
	Night	13% 5% 6% 6% 5% 8% 39%	1208

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	8% 11% 27% 21% 8%	596
	Night	6% 19% 24% 20% 5%	839
February	Day	12% 22% 22% 18%	626
	Night	5% 13% 20% 28% 17%	743
March	Day	6% 16% 29% 25% 8%	830
	Night	7% 16% 35% 19% 6%	838
April	Day	7% 20% 22% 27% 11%	811
	Night	20% 24% 27% 10%	789
May	Day	10% 16% 27% 29%	900
	Night	10% 18% 34% 25%	700
June	Day	18% 28% 20%	715
	Night	17% 37% 20% 9%	560
July	Day	22% 21% 7%	558
	Night	20% 30% 8%	423
August	Day	17% 22% 14%	888
	Night	14% 26% 19%	761
September	Day	14% 16% 15% 12%	788
	Night	15% 17% 20% 9%	819
October	Day	9% 9% 13% 19% 9%	852
	Night	5% 10% 15% 25% 5%	953
November	Day	5% 9% 26% 29% 14%	887
	Night	6% 10% 31% 20% 17%	1082
December	Day	8% 20% 26% 21% 8%	560
	Night	8% 19% 24% 24% 6%	813

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	7% 27% 41% 15%	348
February	Day	42% 14% 28%	7
	Night	5% 32% 43% 14%	289
March	Day	19% 51% 21%	92
	Night	32% 50% 10%	363
April	Day	11% 29% 37% 11%	87
	Night	20% 51% 22%	343
May	Day	10% 26% 37% 24%	87
	Night	10% 53% 29%	267
June	Day	7% 5% 20% 62%	77
	Night	18% 53% 21%	241
July	Day	23% 67%	76
	Night	6% 42% 41%	238
August	Day	27% 58%	86
	Night	9% 47% 33%	289
September	Day	7% 20% 27% 36%	84
	Night	7% 28% 41% 16%	337
October	Day	5% 6% 25% 43% 6%	90
	Night	14% 35% 29%	364
November	Day	24% 41% 28%	78
	Night	22% 49% 22%	431
December	Night	24% 47% 19%	338

Page generated at 2008-11-27 13:47:40. Version ab11