Holmdel
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Holmdel clear sky chart from 2005-11-06 to 2024-03-23.

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% 7% 3 5% 5% 3 5% 5% 5% 7% 41%	78649
	Night	16% 7% 2 5% 5% 3 4 4 5% 7% 43%	81226
Transparency	Day	41% 7% 12% 22% 15% 2	78354
	Night	41% 6% 11% 23% 16% 3	81055
Seeing	Day	18% 10% 29% 27% 13% 3	14149
	Night	19% 9% 31% 29% 11% 1	23480

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	15% 9% 2 4 5% 3 4 4 3 5% 47%	2517
	11th to 20th	Day	16% 9% 4 6% 5% 3 4 4 5% 6% 39%	2520
	21st to end	Day	23% 13% 4 6% 5% 2 3 3 3 4 34%	3060
February	1st to 10th	Day	16% 9% 3 5% 5% 3 5% 3 4 6% 41%	1725
	11th to 20th	Day	16% 8% 3 6% 4 3 4 4 4 5% 43%	1848
	21st to end	Day	18% 8% 3 6% 4 3 4 4 4 6% 38%	1570
March	1st to 10th	Day	17% 6% 2 5% 4 2 4 4 4 7% 44%	1897
	11th to 20th	Day	14% 6% 2 6% 5% 3 5% 4 6% 7% 42%	2011
	21st to end	Day	19% 7% 3 5% 5% 3 4 4 4 5% 42%	2373
April	1st to 10th	Day	17% 8% 3 4 5% 3 3 4 5% 7% 41%	2160
	11th to 20th	Day	15% 6% 3 5% 4 3 5% 5% 6% 8% 41%	2134
	21st to end	Day	19% 5% 2 5% 4 3 5% 5% 6% 7% 39%	2160
May	1st to 10th	Day	20% 8% 3 5% 5% 3 5% 5% 5% 7% 34%	2340
	11th to 20th	Day	21% 6% 2 4 5% 3 4 5% 6% 6% 37%	2446
	21st to end	Day	16% 6% 3 5% 5% 2 4 5% 6% 9% 40%	2725
June	1st to 10th	Day	15% 5% 3 5% 5% 3 5% 6% 6% 10% 37%	2520
	11th to 20th	Day	14% 7% 2 5% 6% 3 5% 5% 6% 9% 37%	2520
	21st to end	Day	10% 4 3 5% 6% 4 6% 6% 7% 9% 40%	2520
July	1st to 10th	Day	10% 5% 3 5% 6% 4 6% 5% 8% 9% 38%	2520
	11th to 20th	Day	9% 5% 2 4 5% 4 6% 7% 7% 10% 41%	2520
	21st to end	Day	10% 6% 3 7% 7% 3 6% 6% 7% 9% 35%	2744
August	1st to 10th	Day	9% 5% 2 5% 7% 3 5% 6% 8% 10% 40%	2333
	11th to 20th	Day	12% 5% 2 5% 6% 3 5% 7% 6% 9% 40%	2126
	21st to end	Day	14% 6% 2 5% 5% 3 5% 4 6% 10% 40%	2376
September	1st to 10th	Day	14% 6% 2 5% 4 3 5% 5% 4 7% 45%	2160
	11th to 20th	Day	13% 5% 2 4 5% 2 4 4 5% 7% 49%	2086
	21st to end	Day	17% 6% 3 6% 5% 2 4 5% 5% 6% 40%	1980
October	1st to 10th	Day	21% 6% 2 4 4 2 4 4 5% 6% 42%	1877
	11th to 20th	Day	16% 5% 3 3 5% 2 5% 4 4 6% 48%	1800
	21st to end	Day	19% 6% 3 4 3 2 4 5% 4 6% 43%	1853
November	1st to 10th	Day	14% 6% 2 4 4 2 4 3 4 6% 51%	1671
	11th to 20th	Day	16% 5% 3 5% 4 2 3 4 4 5% 48%	1710
	21st to end	Day	15% 6% 3 4 4 3 4 4 4 6% 46%	1649
December	1st to 10th	Day	18% 7% 3 6% 4 2 4 4 5% 7% 40%	1520
	11th to 20th	Day	20% 7% 3 4 3 2 3 5% 4 5% 45%	1906
	21st to end	Day	18% 6% 3 5% 7% 4 5% 5% 5% 7% 35%	2772
January	1st to 10th	Night	17% 7% 2 4 4 2 3 4 4 6% 47%	4429
	11th to 20th	Night	17% 9% 2 5% 5% 2 3 4 4 5% 44%	4440
	21st to end	Night	24% 10% 3 6% 4 2 4 3 4 5% 35%	4593
February	1st to 10th	Night	16% 10% 3 5% 4 2 3 4 4 6% 42%	2453
	11th to 20th	Night	18% 8% 3 6% 5% 2 3 4 5% 5% 41%	2218
	21st to end	Night	19% 8% 2 4 4 3 4 4 5% 6% 43%	1884
March	1st to 10th	Night	17% 6% 2 5% 4 2 3 3 4 8% 46%	2270
	11th to 20th	Night	17% 7% 3 5% 5% 3 4 3 5% 6% 43%	2165
	21st to end	Night	18% 6% 4 5% 5% 2 4 4 5% 5% 42%	2027
April	1st to 10th	Night	17% 8% 3 5% 4 3 5% 4 5% 6% 40%	1800
	11th to 20th	Night	16% 7% 3 7% 4 3 4 4 5% 7% 41%	1775
	21st to end	Night	18% 6% 3 4 4 3 4 4 5% 7% 42%	1798
May	1st to 10th	Night	20% 9% 4 6% 5% 3 5% 4 4 7% 35%	1620
	11th to 20th	Night	19% 8% 2 5% 4 3 5% 4 5% 6% 38%	1462
	21st to end	Night	16% 5% 3 6% 6% 3 4 5% 6% 8% 39%	1550
June	1st to 10th	Night	15% 6% 2 6% 5% 2 5% 4 5% 8% 41%	1440
	11th to 20th	Night	15% 6% 3 5% 6% 3 5% 4 6% 9% 40%	1440
	21st to end	Night	8% 6% 2 5% 6% 4 5% 6% 7% 10% 42%	1440
July	1st to 10th	Night	9% 5% 3 6% 6% 3 5% 5% 7% 10% 40%	1440
	11th to 20th	Night	8% 6% 2 6% 5% 3 5% 7% 6% 9% 42%	1440
	21st to end	Night	8% 5% 2 6% 4 3 6% 6% 7% 10% 43%	1574
August	1st to 10th	Night	7% 6% 2 5% 7% 3 6% 6% 6% 10% 43%	1585
	11th to 20th	Night	11% 5% 3 6% 6% 4 6% 5% 7% 8% 39%	1774
	21st to end	Night	12% 6% 3 6% 5% 3 5% 4 6% 8% 42%	1980
September	1st to 10th	Night	14% 6% 3 5% 6% 4 4 4 5% 7% 44%	1800
	11th to 20th	Night	13% 5% 2 4 4 3 3 4 5% 6% 52%	1872
	21st to end	Night	18% 6% 3 6% 4 2 4 3 4 6% 43%	1980
October	1st to 10th	Night	20% 5% 2 5% 3 3 3 4 5% 6% 42%	2079
	11th to 20th	Night	15% 4 2 5% 4 3 4 4 4 6% 50%	2160
	21st to end	Night	20% 7% 3 5% 3 2 3 3 4 6% 44%	2502
November	1st to 10th	Night	13% 4 2 4 4 3 4 3 4 6% 52%	2407
	11th to 20th	Night	17% 7% 3 5% 4 2 3 3 3 5% 48%	2470
	21st to end	Night	14% 4 2 5% 4 4 4 4 5% 7% 47%	2527
December	1st to 10th	Night	20% 7% 2 6% 5% 2 4 4 5% 6% 40%	2660
	11th to 20th	Night	19% 5% 2 5% 4 2 4 5% 4 7% 43%	3288
	21st to end	Night	17% 9% 3 5% 5% 3 5% 4 5% 6% 38%	4884

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	39% 5% 11% 27% 14% 3	2518
	11th to 20th	Day	45% 5% 12% 22% 14% 2	2520
	21st to end	Day	54% 6% 8% 20% 10% 2	3060
February	1st to 10th	Day	45% 5% 14% 23% 13% 2	1725
	11th to 20th	Day	43% 6% 9% 24% 16% 3	1857
	21st to end	Day	46% 5% 11% 20% 13% 5%	1570
March	1st to 10th	Day	40% 6% 13% 24% 14% 3	1900
	11th to 20th	Day	41% 5% 12% 24% 14% 3	2011
	21st to end	Day	46% 5% 8% 20% 16% 5%	2373
April	1st to 10th	Day	43% 5% 11% 20% 16% 5%	2160
	11th to 20th	Day	39% 7% 12% 22% 17% 3	2134
	21st to end	Day	42% 7% 12% 18% 17% 4	2160
May	1st to 10th	Day	47% 8% 10% 18% 15% 2	2340
	11th to 20th	Day	45% 8% 11% 19% 15% 2	2450
	21st to end	Day	40% 8% 15% 21% 13% 2	2725
June	1st to 10th	Day	40% 10% 15% 21% 13% 2	2520
	11th to 20th	Day	42% 10% 14% 21% 12% 2	2520
	21st to end	Day	37% 10% 14% 22% 15% 1	2520
July	1st to 10th	Day	39% 10% 14% 19% 16% 1	2450
	11th to 20th	Day	34% 9% 16% 25% 13% 2	2445
	21st to end	Day	41% 8% 13% 21% 14% 2	2591
August	1st to 10th	Day	36% 10% 16% 24% 13% 1	2319
	11th to 20th	Day	38% 10% 15% 21% 14% 1	2126
	21st to end	Day	38% 8% 12% 22% 17% 3	2376
September	1st to 10th	Day	38% 8% 13% 20% 19% 2	2160
	11th to 20th	Day	34% 5% 13% 22% 23% 2	2086
	21st to end	Day	43% 6% 10% 17% 21% 2	1980
October	1st to 10th	Day	42% 7% 13% 19% 17% 2	1877
	11th to 20th	Day	36% 6% 11% 24% 22% 2	1800
	21st to end	Day	41% 5% 11% 22% 19% 2	1853
November	1st to 10th	Day	36% 3 14% 26% 19% 2	1671
	11th to 20th	Day	39% 5% 10% 22% 22% 3	1710
	21st to end	Day	39% 4 13% 29% 12% 2	1649
December	1st to 10th	Day	44% 5% 15% 21% 14% 1	1520
	11th to 20th	Day	41% 5% 13% 25% 14% 2	1906
	21st to end	Day	45% 9% 12% 24% 10% 1	2772
January	1st to 10th	Night	38% 4 10% 31% 12% 4	4429
	11th to 20th	Night	44% 4 12% 25% 13% 3	4440
	21st to end	Night	51% 5% 8% 22% 13% 1	4593
February	1st to 10th	Night	43% 5% 14% 23% 13% 2	2453
	11th to 20th	Night	44% 5% 9% 19% 18% 5%	2220
	21st to end	Night	41% 5% 9% 24% 17% 4	1884
March	1st to 10th	Night	39% 4 12% 25% 16% 5%	2280
	11th to 20th	Night	43% 5% 9% 21% 17% 4	2166
	21st to end	Night	43% 5% 9% 18% 18% 6%	2027
April	1st to 10th	Night	44% 5% 10% 18% 18% 4	1800
	11th to 20th	Night	42% 6% 10% 18% 21% 2	1775
	21st to end	Night	42% 6% 9% 20% 18% 5%	1798
May	1st to 10th	Night	49% 7% 10% 17% 16% 2	1620
	11th to 20th	Night	46% 6% 12% 16% 17% 3	1463
	21st to end	Night	43% 10% 13% 19% 13% 2	1551
June	1st to 10th	Night	41% 8% 11% 20% 18% 1	1440
	11th to 20th	Night	41% 8% 14% 23% 12% 1	1440
	21st to end	Night	35% 10% 16% 23% 15% 2	1440
July	1st to 10th	Night	39% 10% 14% 21% 13% 2	1400
	11th to 20th	Night	36% 8% 14% 25% 14% 2	1392
	21st to end	Night	33% 12% 15% 24% 14% 3	1486
August	1st to 10th	Night	34% 11% 18% 22% 14% 2	1575
	11th to 20th	Night	39% 10% 15% 22% 13% 1	1774
	21st to end	Night	38% 8% 13% 19% 18% 3	1980
September	1st to 10th	Night	41% 8% 11% 22% 17% 2	1800
	11th to 20th	Night	33% 5% 12% 22% 24% 4	1872
	21st to end	Night	43% 5% 7% 22% 20% 2	1980
October	1st to 10th	Night	43% 7% 11% 22% 15% 2	2079
	11th to 20th	Night	35% 6% 13% 27% 17% 2	2160
	21st to end	Night	42% 5% 10% 24% 18% 1	2502
November	1st to 10th	Night	35% 4 12% 24% 21% 4	2407
	11th to 20th	Night	40% 5% 8% 23% 19% 5%	2470
	21st to end	Night	37% 5% 13% 27% 16% 1	2527
December	1st to 10th	Night	45% 6% 11% 23% 14% 2	2660
	11th to 20th	Night	40% 5% 13% 20% 17% 4	3288
	21st to end	Night	45% 6% 13% 23% 12% 1	4884

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	17% 19% 38% 19% 6% 1	180
	11th to 20th	Day	21% 31% 31% 14% 3	180
	21st to end	Day	21% 16% 36% 20% 6% 1	279
February	1st to 10th	Day	24% 16% 38% 18% 3 1	285
	11th to 20th	Day	23% 20% 37% 19% 1	456
	21st to end	Day	22% 20% 34% 21% 4	382
March	1st to 10th	Day	19% 17% 39% 20% 5%	460
	11th to 20th	Day	17% 17% 43% 18% 5% 1	460
	21st to end	Day	26% 17% 33% 20% 5%	470
April	1st to 10th	Day	21% 15% 36% 20% 6% 1	420
	11th to 20th	Day	17% 13% 35% 23% 10% 2	412
	21st to end	Day	26% 12% 35% 21% 6% 1	420
May	1st to 10th	Day	26% 9% 34% 20% 9% 2	423
	11th to 20th	Day	22% 4 36% 27% 10% 2	447
	21st to end	Day	22% 4 20% 28% 23% 4	485
June	1st to 10th	Day	15% 6% 26% 33% 18% 3	450
	11th to 20th	Day	14% 6% 30% 32% 14% 3	450
	21st to end	Day	12% 4 23% 40% 19% 4	450
July	1st to 10th	Day	11% 4 19% 35% 25% 7%	445
	11th to 20th	Day	10% 2 15% 37% 28% 8%	444
	21st to end	Day	13% 3 22% 39% 20% 4	488
August	1st to 10th	Day	11% 2 16% 40% 24% 8%	446
	11th to 20th	Day	14% 3 15% 34% 28% 6%	439
	21st to end	Day	12% 3 20% 35% 20% 9%	495
September	1st to 10th	Day	17% 5% 20% 28% 21% 9%	450
	11th to 20th	Day	14% 3 23% 33% 19% 9%	450
	21st to end	Day	24% 6% 24% 28% 15% 4	450
October	1st to 10th	Day	25% 6% 20% 24% 19% 6%	450
	11th to 20th	Day	16% 10% 28% 28% 14% 3	450
	21st to end	Day	21% 11% 32% 24% 10% 2	431
November	1st to 10th	Day	16% 9% 34% 25% 14% 2	365
	11th to 20th	Day	19% 18% 33% 22% 9%	370
	21st to end	Day	17% 14% 33% 26% 9% 1	309
December	1st to 10th	Day	18% 21% 39% 13% 8% 1	180
	11th to 20th	Day	28% 18% 29% 18% 7%	180
	21st to end	Day	22% 13% 37% 19% 8%	198
January	1st to 10th	Night	20% 15% 42% 20% 4	760
	11th to 20th	Night	23% 15% 36% 22% 4	760
	21st to end	Night	19% 15% 43% 22% 2	836
February	1st to 10th	Night	21% 13% 40% 24% 2	760
	11th to 20th	Night	22% 19% 42% 15% 1	743
	21st to end	Night	23% 17% 35% 22% 3	628
March	1st to 10th	Night	20% 13% 38% 24% 4	760
	11th to 20th	Night	21% 13% 40% 20% 5% 1	760
	21st to end	Night	20% 10% 40% 24% 6%	801
April	1st to 10th	Night	21% 12% 38% 24% 5%	720
	11th to 20th	Night	18% 9% 34% 32% 6%	711
	21st to end	Night	21% 7% 35% 31% 6% 1	718
May	1st to 10th	Night	24% 9% 30% 28% 9%	540
	11th to 20th	Night	22% 6% 34% 30% 6%	401
	21st to end	Night	17% 3 21% 37% 19% 3	389
June	1st to 10th	Night	17% 6% 23% 37% 17% 1	360
	11th to 20th	Night	15% 4 22% 41% 18%	360
	21st to end	Night	8% 3 18% 51% 19% 1	360
July	1st to 10th	Night	12% 3 20% 40% 23% 2	350
	11th to 20th	Night	10% 3 15% 43% 26% 2	348
	21st to end	Night	10% 2 19% 48% 21%	394
August	1st to 10th	Night	9% 3 16% 46% 23% 3	511
	11th to 20th	Night	13% 3 15% 39% 28% 3	710
	21st to end	Night	14% 3 13% 40% 26% 3	792
September	1st to 10th	Night	15% 3 21% 37% 20% 4	720
	11th to 20th	Night	16% 3 20% 34% 21% 6%	720
	21st to end	Night	20% 5% 22% 33% 17% 3	720
October	1st to 10th	Night	23% 6% 24% 26% 17% 3	720
	11th to 20th	Night	17% 8% 28% 35% 11% 1	720
	21st to end	Night	23% 8% 36% 24% 9% 1	792
November	1st to 10th	Night	16% 7% 36% 27% 12% 1	740
	11th to 20th	Night	19% 14% 33% 25% 9% 1	760
	21st to end	Night	15% 14% 39% 24% 7% 1	760
December	1st to 10th	Night	23% 16% 34% 19% 7% 1	760
	11th to 20th	Night	21% 11% 41% 24% 4	760
	21st to end	Night	21% 11% 41% 24% 3	836

Page generated at 2024-03-19 23:31:08. Version ac07

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