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Miami
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Miami 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	12% 5% 6% 6% 6% 10% 6% 7% 10% 24%	8672
	Night	13% 5% 7% 6% 6% 8% 6% 6% 10% 26%	8500
Transparency	Day	32% 17% 31% 16%	4219
	Night	30% 19% 31% 16%	4337
Seeing	Day	5% 14% 23% 27% 29%	642
	Night	5% 18% 26% 33% 16%	2865

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% 7% 5% 6% 8% 5% 8% 35%	554
	Night	11% 5% 5% 6% 5% 7% 5% 5% 7% 35%	799
February	Day	10% 5% 5% 6% 9% 5% 8% 11% 28%	602
	Night	11% 6% 5% 7% 5% 10% 38%	652
March	Day	11% 7% 11% 7% 6% 7% 31%	682
	Night	14% 6% 5% 5% 7% 7% 6% 6% 32%	682
April	Day	11% 5% 5% 9% 44%	690
	Night	13% 5% 5% 8% 46%	630
May	Day	8% 5% 5% 6% 5% 8% 6% 7% 9% 32%	760
	Night	9% 7% 6% 6% 13% 5% 5% 9% 30%	594
June	Day	14% 7% 6% 6% 6% 14% 8% 9% 8% 14%	780
	Night	16% 6% 6% 5% 7% 7% 5% 8% 10% 23%	537
July	Day	7% 6% 14% 9% 8% 14% 22%	801
	Night	13% 8% 12% 19% 25%	558
August	Day	11% 5% 5% 7% 13% 7% 11% 12% 14%	1109
	Night	13% 7% 7% 7% 6% 8% 8% 6% 12% 17%	929
September	Day	17% 5% 6% 5% 6% 12% 8% 8% 8% 14%	971
	Night	16% 6% 9% 6% 7% 5% 10% 5% 7% 9% 14%	975
October	Day	12% 7% 8% 6% 6% 11% 8% 7% 8% 16%	627
	Night	13% 8% 9% 7% 7% 10% 5% 6% 10% 16%	734
November	Day	12% 5% 6% 7% 6% 9% 6% 8% 11% 23%	528
	Night	16% 7% 9% 6% 7% 5% 8% 5% 5% 8% 19%	640
December	Day	13% 5% 8% 6% 7% 8% 5% 5% 8% 25%	568
	Night	15% 7% 8% 5% 7% 7% 5% 8% 24%	770

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	21% 17% 39% 21%	327
	Night	27% 9% 42% 18%	464
February	Day	18% 13% 43% 23%	322
	Night	19% 12% 37% 28%	408
March	Day	19% 10% 34% 27% 8%	355
	Night	24% 16% 26% 31%	331
April	Day	15% 13% 35% 27% 8%	440
	Night	14% 10% 33% 29% 11%	409
May	Day	22% 9% 46% 21%	436
	Night	21% 15% 49% 13%	320
June	Day	62% 14% 23%	211
	Night	51% 10% 35%	221
July	Day	46% 24% 26%	345
	Night	41% 26% 31%	285
August	Day	69% 20% 9%	418
	Night	56% 34% 8%	337
September	Day	47% 37% 14%	308
	Night	40% 43% 14%	368
October	Day	32% 20% 31% 14%	422
	Night	30% 20% 32% 15%	471
November	Day	20% 17% 33% 28%	339
	Night	27% 19% 31% 22%	342
December	Day	19% 12% 38% 24%	296
	Night	24% 17% 34% 18% 5%	381

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	6% 26% 35% 27%	228
February	Day	10% 17% 46% 21%	28
	Night	7% 25% 42% 25%	208
March	Day	7% 30% 45% 15%	53
	Night	7% 30% 48% 13%	228
April	Day	8% 24% 33% 22% 10%	57
	Night	5% 35% 29% 26%	225
May	Day	14% 17% 45% 19%	57
	Night	11% 42% 41%	214
June	Day	7% 7% 26% 54%	53
	Night	18% 39% 34%	161
July	Day	9% 9% 72%	61
	Night	37% 54%	182
August	Day	8% 28% 58%	85
	Night	9% 7% 35% 44%	324
September	Day	8% 10% 12% 39% 28%	83
	Night	14% 14% 43% 24%	318
October	Day	15% 30% 31% 20%	86
	Night	5% 13% 27% 42% 11%	333
November	Day	22% 39% 20% 13%	58
	Night	7% 24% 23% 36% 8%	228
December	Day	38% 33% 23%	21
	Night	10% 26% 35% 25%	216

Page generated at 2008-09-02 02:07:23. Version ab11