Wachapreague
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wachapreague clear sky chart from 2005-11-06 to 2024-12-02.

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% 6% 2 6% 4 4 4 4 6% 8% 42%	101307
	Night	14% 7% 3 7% 4 4 4 4 5% 7% 41%	98272
Transparency	Day	38% 5% 14% 25% 16% 3	104940
	Night	41% 5% 11% 24% 16% 3	102778
Seeing	Day	15% 5% 17% 31% 25% 8%	15317
	Night	16% 6% 23% 32% 19% 4	24793

By Month

Percentage Cloud Cover SE (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% 7% 3 6% 4 3 3 3 4 6% 46%	2517
	11th to 20th	Day	12% 8% 3 8% 5% 4 3 2 5% 6% 44%	2840
	21st to end	Day	13% 9% 4 10% 5% 4 4 3 5% 6% 38%	3124
February	1st to 10th	Day	12% 8% 2 7% 5% 4 5% 4 7% 8% 38%	1710
	11th to 20th	Day	19% 8% 2 5% 4 2 3 3 5% 6% 43%	1839
	21st to end	Day	17% 9% 2 6% 6% 4 4 4 5% 5% 38%	1570
March	1st to 10th	Day	22% 8% 2 7% 4 4 4 3 5% 6% 35%	3212
	11th to 20th	Day	9% 4 2 4 3 3 3 4 5% 8% 55%	3480
	21st to end	Day	17% 9% 3 6% 4 3 3 3 5% 6% 43%	3996
April	1st to 10th	Day	11% 6% 2 6% 3 4 4 4 6% 7% 48%	2280
	11th to 20th	Day	10% 5% 2 5% 3 4 4 3 5% 8% 50%	2254
	21st to end	Day	12% 6% 2 5% 4 4 4 3 5% 7% 48%	2280
May	1st to 10th	Day	14% 8% 3 8% 5% 5% 5% 5% 7% 10% 31%	3765
	11th to 20th	Day	16% 8% 3 8% 5% 5% 4 4 6% 8% 33%	4321
	21st to end	Day	9% 5% 2 6% 4 4 5% 5% 7% 10% 42%	4823
June	1st to 10th	Day	9% 5% 2 5% 3 4 4 4 9% 10% 45%	2660
	11th to 20th	Day	9% 5% 2 4 4 4 4 4 7% 11% 46%	2660
	21st to end	Day	6% 4 2 5% 5% 4 5% 4 6% 12% 45%	2660
July	1st to 10th	Day	6% 4 2 5% 4 4 5% 5% 8% 13% 45%	4440
	11th to 20th	Day	10% 6% 3 7% 5% 5% 4 4 7% 11% 38%	4409
	21st to end	Day	8% 6% 2 7% 6% 6% 5% 5% 8% 10% 37%	4466
August	1st to 10th	Day	13% 8% 3 7% 5% 5% 4 4 6% 11% 34%	4024
	11th to 20th	Day	8% 6% 2 6% 5% 6% 6% 4 7% 9% 42%	3730
	21st to end	Day	8% 4 1 5% 3 4 5% 4 6% 11% 48%	4180
September	1st to 10th	Day	14% 6% 2 5% 3 4 5% 4 6% 8% 45%	2280
	11th to 20th	Day	10% 5% 3 7% 5% 4 4 3 6% 8% 45%	2266
	21st to end	Day	19% 7% 2 7% 4 4 4 4 4 7% 39%	2071
October	1st to 10th	Day	14% 6% 1 6% 5% 4 5% 3 4 6% 47%	1900
	11th to 20th	Day	14% 5% 2 5% 4 3 3 3 4 5% 51%	1900
	21st to end	Day	13% 5% 2 6% 4 4 4 3 4 6% 47%	2090
November	1st to 10th	Day	12% 6% 2 6% 5% 3 4 3 5% 8% 47%	1790
	11th to 20th	Day	11% 8% 2 5% 4 4 4 4 5% 8% 47%	1800
	21st to end	Day	15% 5% 2 5% 3 3 5% 3 5% 7% 48%	1760
December	1st to 10th	Day	17% 8% 2 6% 4 4 3 5% 6% 6% 39%	1528
	11th to 20th	Day	15% 8% 3 6% 3 3 3 2 4 6% 47%	1910
	21st to end	Day	15% 8% 2 5% 3 4 4 3 5% 7% 42%	2772
January	1st to 10th	Night	13% 7% 3 7% 5% 4 4 4 6% 6% 41%	4425
	11th to 20th	Night	15% 8% 4 9% 5% 4 4 3 4 5% 39%	4120
	21st to end	Night	16% 9% 3 10% 5% 5% 4 3 4 5% 37%	4532
February	1st to 10th	Night	16% 8% 3 6% 4 3 3 3 5% 6% 43%	2470
	11th to 20th	Night	19% 8% 2 5% 4 3 4 3 5% 7% 40%	2224
	21st to end	Night	17% 8% 2 6% 4 3 4 3 4 5% 45%	1884
March	1st to 10th	Night	22% 9% 3 8% 3 3 4 3 5% 6% 35%	3638
	11th to 20th	Night	14% 6% 2 5% 4 4 4 3 4 7% 48%	3480
	21st to end	Night	17% 10% 2 5% 3 3 3 2 4 4 46%	3636
April	1st to 10th	Night	13% 8% 3 7% 4 4 4 4 7% 7% 38%	1900
	11th to 20th	Night	11% 5% 2 5% 4 4 4 3 5% 7% 50%	1875
	21st to end	Night	13% 7% 1 6% 4 4 4 4 5% 8% 43%	1900
May	1st to 10th	Night	17% 7% 3 9% 5% 5% 5% 4 7% 7% 31%	3130
	11th to 20th	Night	19% 9% 3 6% 4 4 4 4 6% 8% 33%	2585
	21st to end	Night	10% 7% 4 8% 4 4 5% 4 7% 9% 38%	2732
June	1st to 10th	Night	12% 7% 2 7% 5% 5% 4 5% 6% 10% 38%	1520
	11th to 20th	Night	7% 5% 2 8% 4 6% 6% 6% 6% 10% 40%	1520
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 4 6% 11% 44%	1520
July	1st to 10th	Night	8% 5% 2 8% 5% 6% 6% 5% 7% 10% 38%	2520
	11th to 20th	Night	8% 7% 3 6% 6% 5% 6% 4 7% 12% 37%	2546
	21st to end	Night	12% 8% 3 8% 5% 5% 6% 5% 7% 8% 32%	3087
August	1st to 10th	Night	13% 9% 4 9% 5% 5% 5% 4 6% 9% 31%	2873
	11th to 20th	Night	10% 5% 3 8% 5% 5% 5% 4 5% 9% 40%	3097
	21st to end	Night	9% 5% 2 6% 4 4 4 3 6% 10% 47%	3476
September	1st to 10th	Night	11% 5% 3 6% 5% 4 5% 4 5% 7% 46%	1900
	11th to 20th	Night	10% 7% 2 7% 4 5% 4 4 6% 7% 45%	1913
	21st to end	Night	19% 7% 3 8% 4 5% 4 4 6% 7% 34%	2104
October	1st to 10th	Night	14% 6% 3 5% 4 3 4 3 6% 7% 46%	2280
	11th to 20th	Night	15% 6% 2 5% 4 3 4 3 4 5% 48%	2280
	21st to end	Night	15% 6% 2 5% 4 4 3 3 4 6% 48%	2508
November	1st to 10th	Night	14% 7% 2 6% 4 3 4 3 5% 6% 47%	2507
	11th to 20th	Night	14% 7% 3 6% 4 4 4 4 5% 7% 44%	2600
	21st to end	Night	11% 5% 2 5% 4 4 4 3 6% 7% 49%	2635
December	1st to 10th	Night	17% 8% 3 7% 5% 4 4 4 5% 6% 36%	2686
	11th to 20th	Night	17% 8% 3 7% 4 3 3 3 5% 7% 40%	3285
	21st to end	Night	13% 8% 3 6% 4 3 4 4 5% 8% 42%	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	40% 3 8% 30% 16% 2	2518
	11th to 20th	Day	42% 3 9% 22% 21% 4	2840
	21st to end	Day	48% 4 9% 24% 13% 2	3124
February	1st to 10th	Day	42% 5% 12% 26% 12% 3	1710
	11th to 20th	Day	43% 3 9% 23% 17% 5%	1848
	21st to end	Day	47% 5% 11% 19% 14% 5%	1570
March	1st to 10th	Day	50% 4 9% 19% 15% 3	3212
	11th to 20th	Day	28% 3 10% 29% 24% 5%	3480
	21st to end	Day	44% 4 11% 19% 18% 4	3996
April	1st to 10th	Day	36% 5% 11% 23% 20% 5%	2280
	11th to 20th	Day	33% 4 12% 27% 20% 5%	2254
	21st to end	Day	36% 5% 12% 26% 17% 4	2280
May	1st to 10th	Day	49% 8% 13% 20% 8% 2	3800
	11th to 20th	Day	48% 6% 14% 24% 7% 1	4325
	21st to end	Day	36% 7% 15% 25% 15% 3	4837
June	1st to 10th	Day	32% 7% 17% 28% 14% 1	2660
	11th to 20th	Day	31% 7% 17% 29% 14% 2	2660
	21st to end	Day	31% 7% 17% 27% 16% 1	2660
July	1st to 10th	Day	29% 10% 27% 21% 11% 2	4370
	11th to 20th	Day	39% 7% 25% 23% 6% 1	4334
	21st to end	Day	40% 9% 17% 20% 13% 1	4324
August	1st to 10th	Day	42% 7% 20% 24% 6%	4011
	11th to 20th	Day	35% 7% 17% 30% 10%	3766
	21st to end	Day	29% 6% 16% 30% 18% 2	4180
September	1st to 10th	Day	37% 5% 17% 20% 18% 3	2280
	11th to 20th	Day	38% 4 11% 27% 19% 2	2266
	21st to end	Day	46% 5% 10% 21% 17% 2	2071
October	1st to 10th	Day	31% 6% 9% 27% 23% 5%	3160
	11th to 20th	Day	26% 3 8% 23% 33% 8%	3140
	21st to end	Day	25% 4 9% 29% 24% 9%	3428
November	1st to 10th	Day	37% 4 10% 27% 18% 4	1790
	11th to 20th	Day	38% 4 13% 21% 21% 5%	1800
	21st to end	Day	37% 4 11% 27% 19% 3	1760
December	1st to 10th	Day	46% 4 13% 22% 13% 2	1528
	11th to 20th	Day	40% 4 9% 29% 15% 4	1906
	21st to end	Day	41% 5% 13% 27% 13% 1	2772
January	1st to 10th	Night	42% 3 8% 27% 17% 3	4425
	11th to 20th	Night	46% 6% 8% 23% 16% 1	4120
	21st to end	Night	50% 5% 7% 24% 13% 2	4532
February	1st to 10th	Night	43% 3 11% 25% 16% 2	2470
	11th to 20th	Night	45% 3 7% 24% 17% 4	2226
	21st to end	Night	44% 3 8% 22% 18% 5%	1884
March	1st to 10th	Night	51% 4 8% 22% 14% 2	3638
	11th to 20th	Night	37% 4 7% 25% 22% 5%	3480
	21st to end	Night	43% 3 7% 25% 17% 6%	3636
April	1st to 10th	Night	43% 5% 10% 19% 20% 4	1900
	11th to 20th	Night	35% 4 10% 24% 22% 5%	1875
	21st to end	Night	39% 5% 12% 24% 17% 4	1900
May	1st to 10th	Night	51% 6% 12% 21% 9% 2	3160
	11th to 20th	Night	50% 5% 12% 25% 7% 1	2586
	21st to end	Night	42% 7% 13% 23% 15% 1	2739
June	1st to 10th	Night	42% 6% 13% 24% 15% 1	1520
	11th to 20th	Night	37% 6% 17% 24% 15% 1	1520
	21st to end	Night	33% 7% 18% 24% 16% 2	1520
July	1st to 10th	Night	39% 10% 19% 20% 10% 2	2480
	11th to 20th	Night	38% 8% 23% 24% 7% 1	2498
	21st to end	Night	47% 8% 14% 18% 12%	2988
August	1st to 10th	Night	48% 6% 18% 21% 6%	2862
	11th to 20th	Night	39% 6% 17% 27% 11%	3127
	21st to end	Night	32% 6% 11% 27% 24% 1	3476
September	1st to 10th	Night	37% 6% 16% 20% 17% 4	1900
	11th to 20th	Night	37% 5% 9% 27% 19% 2	1913
	21st to end	Night	48% 5% 10% 18% 15% 2	2104
October	1st to 10th	Night	35% 5% 11% 25% 22% 3	3800
	11th to 20th	Night	28% 3 7% 24% 29% 9%	3779
	21st to end	Night	24% 3 7% 32% 24% 11%	4120
November	1st to 10th	Night	38% 4 9% 26% 18% 4	2507
	11th to 20th	Night	41% 4 10% 21% 18% 5%	2600
	21st to end	Night	35% 3 10% 28% 20% 3	2635
December	1st to 10th	Night	48% 5% 10% 22% 13% 2	2686
	11th to 20th	Night	44% 4 9% 23% 18% 3	3288
	21st to end	Night	40% 4 14% 28% 13% 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	19% 8% 28% 34% 10%	180
	11th to 20th	Day	16% 11% 33% 29% 10%	270
	21st to end	Day	20% 5% 27% 38% 9% 1	297
February	1st to 10th	Day	14% 9% 23% 41% 14%	270
	11th to 20th	Day	26% 9% 31% 27% 6%	447
	21st to end	Day	23% 6% 29% 32% 8% 1	382
March	1st to 10th	Day	18% 7% 28% 37% 9% 1	460
	11th to 20th	Day	17% 7% 27% 36% 12% 2	460
	21st to end	Day	16% 5% 28% 37% 12% 1	506
April	1st to 10th	Day	14% 7% 29% 35% 14% 2	460
	11th to 20th	Day	11% 3 23% 42% 18% 3	452
	21st to end	Day	16% 5% 20% 37% 19% 4	460
May	1st to 10th	Day	16% 6% 17% 37% 22% 4	463
	11th to 20th	Day	18% 3 15% 35% 25% 5%	487
	21st to end	Day	17% 3 9% 29% 31% 12%	529
June	1st to 10th	Day	11% 2 7% 31% 38% 11%	490
	11th to 20th	Day	9% 2 9% 32% 36% 12%	490
	21st to end	Day	8% 2 10% 31% 38% 11%	490
July	1st to 10th	Day	12% 1 4 24% 43% 17%	485
	11th to 20th	Day	7% 2 2 23% 49% 17%	484
	21st to end	Day	10% 2 3 26% 48% 10%	532
August	1st to 10th	Day	11% 1 5% 28% 40% 14%	486
	11th to 20th	Day	10% 2 4 26% 38% 19%	479
	21st to end	Day	10% 2 6% 26% 39% 17%	539
September	1st to 10th	Day	15% 2 7% 25% 32% 18%	490
	11th to 20th	Day	13% 3 11% 27% 33% 14%	490
	21st to end	Day	25% 4 12% 28% 25% 7%	490
October	1st to 10th	Day	17% 4 10% 29% 29% 11%	490
	11th to 20th	Day	16% 5% 18% 31% 23% 7%	490
	21st to end	Day	16% 6% 21% 29% 21% 7%	539
November	1st to 10th	Day	15% 6% 25% 28% 20% 6%	410
	11th to 20th	Day	14% 11% 31% 29% 14% 2	400
	21st to end	Day	17% 12% 26% 23% 19% 2	360
December	1st to 10th	Day	23% 7% 24% 32% 13% 2	182
	11th to 20th	Day	19% 7% 28% 27% 18% 1	180
	21st to end	Day	20% 7% 25% 33% 14% 2	198
January	1st to 10th	Night	17% 14% 34% 28% 7%	760
	11th to 20th	Night	19% 13% 32% 27% 9%	760
	21st to end	Night	20% 12% 33% 31% 5%	836
February	1st to 10th	Night	20% 8% 35% 32% 6% 1	760
	11th to 20th	Night	24% 12% 38% 23% 4	743
	21st to end	Night	22% 9% 30% 32% 5% 1	628
March	1st to 10th	Night	17% 8% 34% 32% 9%	760
	11th to 20th	Night	20% 8% 32% 30% 8% 2	760
	21st to end	Night	20% 6% 30% 35% 9%	836
April	1st to 10th	Night	17% 6% 35% 33% 8% 1	760
	11th to 20th	Night	13% 5% 26% 41% 15% 1	751
	21st to end	Night	15% 4 25% 39% 14% 1	760
May	1st to 10th	Night	18% 6% 22% 37% 15% 2	760
	11th to 20th	Night	17% 5% 18% 37% 21% 2	438
	21st to end	Night	14% 2 10% 34% 32% 8%	411
June	1st to 10th	Night	15% 3 11% 37% 32% 4	380
	11th to 20th	Night	7% 1 10% 44% 32% 6%	380
	21st to end	Night	8% 2 10% 40% 35% 5%	380
July	1st to 10th	Night	8% 1 6% 37% 39% 8%	370
	11th to 20th	Night	7% 3 3 27% 50% 10%	381
	21st to end	Night	9% 3 7% 35% 39% 7%	624
August	1st to 10th	Night	10% 2 4 37% 39% 8%	589
	11th to 20th	Night	13% 2 5% 32% 39% 9%	750
	21st to end	Night	10% 1 7% 30% 41% 12%	836
September	1st to 10th	Night	14% 2 7% 29% 36% 11%	760
	11th to 20th	Night	13% 2 9% 28% 38% 10%	760
	21st to end	Night	22% 4 12% 30% 28% 4	760
October	1st to 10th	Night	18% 4 15% 28% 28% 7%	760
	11th to 20th	Night	18% 5% 22% 31% 21% 3	760
	21st to end	Night	18% 8% 22% 31% 17% 5%	836
November	1st to 10th	Night	17% 7% 22% 31% 17% 6%	780
	11th to 20th	Night	18% 10% 28% 30% 13% 2	800
	21st to end	Night	14% 12% 28% 29% 16% 2	800
December	1st to 10th	Night	21% 9% 35% 23% 11% 1	768
	11th to 20th	Night	19% 10% 36% 27% 9%	760
	21st to end	Night	17% 10% 30% 32% 11%	836

Page generated at 2024-11-29 10:43:11. Version ac07

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