Morrow
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morrow clear sky chart from 2005-11-06 to 2024-01-13.

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% 9% 4 6% 6% 3 5% 5% 5% 7% 36%	75316
	Night	15% 9% 4 6% 5% 3 4 4 5% 7% 38%	74369
Transparency	Day	46% 6% 12% 21% 13% 2	75031
	Night	46% 6% 11% 21% 14% 2	74174
Seeing	Day	18% 10% 25% 24% 16% 7%	14148
	Night	18% 7% 26% 31% 15% 2	23788

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	17% 14% 5% 10% 6% 3 4 5% 4 5% 25%	1585
	11th to 20th	Day	21% 14% 7% 9% 7% 3 3 4 4 5% 24%	1644
	21st to end	Day	17% 16% 5% 10% 7% 4 4 4 5% 6% 23%	1782
February	1st to 10th	Day	20% 14% 5% 9% 6% 3 4 4 4 4 26%	1692
	11th to 20th	Day	18% 11% 5% 10% 8% 4 4 4 5% 6% 27%	1748
	21st to end	Day	19% 14% 5% 8% 6% 3 4 3 3 6% 30%	1480
March	1st to 10th	Day	17% 11% 4 6% 6% 4 4 4 4 6% 33%	1825
	11th to 20th	Day	19% 10% 4 7% 6% 3 4 5% 5% 6% 31%	1980
	21st to end	Day	22% 9% 5% 7% 5% 3 5% 4 5% 6% 29%	2178
April	1st to 10th	Day	15% 8% 4 6% 5% 3 5% 5% 5% 7% 36%	2101
	11th to 20th	Day	17% 8% 3 6% 5% 3 4 3 5% 6% 39%	2199
	21st to end	Day	19% 7% 4 6% 5% 3 6% 4 5% 7% 35%	2340
May	1st to 10th	Day	20% 8% 3 6% 6% 3 5% 5% 4 6% 34%	2340
	11th to 20th	Day	20% 8% 3 6% 6% 3 5% 5% 5% 8% 32%	2301
	21st to end	Day	9% 6% 2 6% 7% 4 6% 6% 7% 9% 37%	2531
June	1st to 10th	Day	12% 6% 3 5% 5% 4 5% 6% 7% 8% 40%	2340
	11th to 20th	Day	10% 5% 3 5% 5% 4 5% 5% 6% 9% 43%	2480
	21st to end	Day	9% 6% 3 5% 6% 4 6% 6% 6% 10% 40%	2520
July	1st to 10th	Day	12% 6% 3 5% 6% 4 5% 6% 5% 9% 38%	2520
	11th to 20th	Day	8% 6% 2 5% 6% 4 6% 6% 6% 10% 42%	2399
	21st to end	Day	10% 5% 2 5% 5% 4 6% 6% 7% 9% 41%	2547
August	1st to 10th	Day	9% 4 2 5% 5% 4 5% 7% 7% 10% 43%	2327
	11th to 20th	Day	9% 5% 3 6% 6% 3 6% 7% 6% 10% 39%	2303
	21st to end	Day	8% 5% 2 5% 5% 3 5% 4 6% 8% 48%	2424
September	1st to 10th	Day	13% 5% 2 5% 5% 3 4 4 5% 8% 47%	2034
	11th to 20th	Day	10% 5% 2 4 5% 3 4 4 6% 9% 48%	1980
	21st to end	Day	15% 5% 3 5% 5% 2 3 3 4 6% 48%	1980
October	1st to 10th	Day	11% 5% 2 5% 4 4 5% 4 5% 7% 47%	1980
	11th to 20th	Day	15% 7% 3 5% 4 3 4 4 5% 6% 45%	1813
	21st to end	Day	21% 9% 3 6% 4 3 3 3 5% 6% 37%	1864
November	1st to 10th	Day	9% 6% 3 5% 4 3 4 4 4 6% 52%	1672
	11th to 20th	Day	13% 11% 4 8% 6% 3 4 4 5% 6% 37%	1710
	21st to end	Day	18% 11% 3 7% 5% 3 4 3 4 6% 36%	1710
December	1st to 10th	Day	21% 12% 7% 9% 7% 3 5% 4 3 5% 24%	1710
	11th to 20th	Day	16% 14% 5% 9% 6% 3 5% 4 4 5% 27%	2153
	21st to end	Day	20% 21% 6% 9% 6% 4 4 4 4 5% 17%	3124
January	1st to 10th	Night	16% 13% 7% 10% 8% 4 4 4 4 4 25%	2517
	11th to 20th	Night	19% 14% 6% 9% 7% 3 5% 4 4 6% 24%	2378
	21st to end	Night	16% 14% 6% 9% 7% 3 4 4 4 5% 28%	2574
February	1st to 10th	Night	23% 12% 5% 8% 5% 3 5% 4 4 5% 27%	2265
	11th to 20th	Night	18% 10% 4 7% 7% 3 5% 5% 6% 6% 30%	2098
	21st to end	Night	22% 14% 5% 7% 4 3 3 4 3 5% 29%	1776
March	1st to 10th	Night	18% 8% 3 6% 6% 3 4 4 5% 5% 38%	2134
	11th to 20th	Night	17% 9% 4 6% 5% 3 5% 4 5% 6% 35%	1980
	21st to end	Night	21% 8% 4 6% 5% 3 5% 4 4 7% 33%	2178
April	1st to 10th	Night	15% 7% 2 5% 5% 3 5% 5% 6% 6% 40%	1873
	11th to 20th	Night	14% 7% 3 5% 5% 2 4 6% 6% 8% 41%	1708
	21st to end	Night	17% 7% 3 6% 5% 3 4 4 6% 8% 37%	1620
May	1st to 10th	Night	18% 8% 4 7% 6% 3 4 5% 5% 8% 33%	1620
	11th to 20th	Night	16% 6% 3 6% 5% 3 5% 4 6% 7% 38%	1592
	21st to end	Night	6% 5% 2 4 5% 3 6% 6% 8% 11% 43%	1744
June	1st to 10th	Night	8% 4 2 5% 5% 3 5% 5% 5% 9% 50%	1620
	11th to 20th	Night	9% 4 2 4 5% 3 4 6% 7% 10% 47%	1474
	21st to end	Night	7% 3 2 4 5% 4 6% 6% 7% 10% 46%	1440
July	1st to 10th	Night	9% 6% 2 5% 5% 3 4 4 6% 8% 48%	1440
	11th to 20th	Night	7% 4 3 4 4 3 4 6% 6% 10% 49%	1556
	21st to end	Night	8% 4 2 6% 5% 3 4 5% 6% 8% 48%	1771
August	1st to 10th	Night	7% 4 2 5% 5% 3 4 6% 7% 9% 48%	1611
	11th to 20th	Night	7% 5% 3 5% 5% 3 5% 4 6% 9% 47%	1598
	21st to end	Night	6% 4 1 4 3 3 4 4 5% 8% 55%	1929
September	1st to 10th	Night	11% 5% 2 4 4 3 4 4 5% 7% 50%	1906
	11th to 20th	Night	8% 4 2 5% 4 3 4 4 5% 7% 55%	1980
	21st to end	Night	13% 5% 2 5% 4 2 4 4 4 6% 52%	1980
October	1st to 10th	Night	9% 4 2 5% 4 4 4 4 4 7% 53%	1980
	11th to 20th	Night	14% 7% 2 6% 5% 3 4 5% 5% 7% 43%	2146
	21st to end	Night	20% 7% 3 6% 5% 3 4 4 5% 6% 40%	2491
November	1st to 10th	Night	14% 7% 3 5% 4 3 4 3 5% 6% 47%	2406
	11th to 20th	Night	16% 8% 3 6% 5% 3 4 4 4 7% 40%	2470
	21st to end	Night	19% 11% 4 6% 6% 3 4 4 5% 7% 32%	2470
December	1st to 10th	Night	21% 11% 5% 8% 5% 3 4 4 5% 6% 28%	2470
	11th to 20th	Night	19% 12% 7% 8% 6% 3 4 4 4 7% 28%	3042
	21st to end	Night	19% 19% 7% 9% 7% 4 5% 4 4 5% 17%	4532

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	60% 6% 8% 16% 10%	1586
	11th to 20th	Day	64% 5% 11% 14% 5%	1644
	21st to end	Day	62% 5% 10% 16% 5% 1	1782
February	1st to 10th	Day	61% 5% 9% 15% 8% 2	1692
	11th to 20th	Day	59% 4 10% 17% 9% 1	1758
	21st to end	Day	58% 4 8% 20% 8% 2	1480
March	1st to 10th	Day	51% 6% 10% 23% 10% 1	1825
	11th to 20th	Day	53% 6% 11% 19% 10% 1	1980
	21st to end	Day	56% 5% 11% 20% 8% 1	2178
April	1st to 10th	Day	47% 6% 11% 23% 12% 1	2101
	11th to 20th	Day	46% 5% 10% 21% 14% 3	2199
	21st to end	Day	49% 5% 11% 21% 11% 2	2340
May	1st to 10th	Day	51% 6% 12% 21% 9% 1	2340
	11th to 20th	Day	50% 6% 13% 18% 12% 1	2305
	21st to end	Day	40% 10% 17% 21% 11% 1	2531
June	1st to 10th	Day	40% 7% 11% 24% 16% 2	2340
	11th to 20th	Day	35% 8% 14% 24% 17% 2	2480
	21st to end	Day	39% 8% 15% 21% 14% 3	2520
July	1st to 10th	Day	41% 8% 13% 20% 16% 2	2451
	11th to 20th	Day	36% 8% 13% 25% 16% 1	2326
	21st to end	Day	37% 9% 15% 24% 13% 3	2405
August	1st to 10th	Day	33% 9% 16% 27% 14% 2	2314
	11th to 20th	Day	37% 8% 14% 26% 15% 1	2303
	21st to end	Day	33% 7% 14% 24% 17% 5%	2424
September	1st to 10th	Day	36% 5% 12% 24% 18% 6%	2034
	11th to 20th	Day	32% 6% 13% 26% 21% 2	1980
	21st to end	Day	38% 5% 9% 24% 22% 2	1980
October	1st to 10th	Day	36% 6% 12% 24% 20% 2	1980
	11th to 20th	Day	40% 4 9% 26% 19% 3	1813
	21st to end	Day	48% 4 12% 20% 15% 2	1864
November	1st to 10th	Day	33% 5% 10% 29% 21% 3	1672
	11th to 20th	Day	49% 4 8% 21% 15% 3	1710
	21st to end	Day	51% 4 9% 23% 13% 1	1710
December	1st to 10th	Day	63% 4 11% 16% 5%	1710
	11th to 20th	Day	59% 5% 9% 18% 10%	2150
	21st to end	Day	69% 5% 9% 10% 6% 1	3124
January	1st to 10th	Night	62% 6% 6% 17% 9%	2517
	11th to 20th	Night	62% 5% 11% 16% 6% 1	2378
	21st to end	Night	59% 5% 8% 19% 7% 1	2574
February	1st to 10th	Night	60% 4 10% 18% 6% 1	2265
	11th to 20th	Night	54% 4 10% 20% 10% 1	2099
	21st to end	Night	58% 5% 10% 16% 9% 2	1776
March	1st to 10th	Night	49% 5% 8% 23% 14% 2	2134
	11th to 20th	Night	49% 5% 12% 21% 10% 2	1980
	21st to end	Night	52% 5% 9% 22% 9% 2	2178
April	1st to 10th	Night	43% 6% 11% 25% 12% 2	1873
	11th to 20th	Night	41% 5% 12% 17% 20% 5%	1708
	21st to end	Night	46% 5% 11% 22% 13% 3	1620
May	1st to 10th	Night	50% 7% 11% 20% 10% 3	1620
	11th to 20th	Night	46% 7% 13% 19% 13% 2	1593
	21st to end	Night	31% 10% 18% 24% 14% 3	1745
June	1st to 10th	Night	30% 8% 11% 28% 20% 3	1620
	11th to 20th	Night	30% 9% 16% 23% 19% 4	1474
	21st to end	Night	31% 10% 16% 22% 17% 5%	1440
July	1st to 10th	Night	34% 8% 13% 22% 19% 4	1400
	11th to 20th	Night	28% 8% 15% 27% 18% 3	1506
	21st to end	Night	31% 8% 13% 30% 16% 2	1672
August	1st to 10th	Night	30% 10% 15% 28% 16% 2	1600
	11th to 20th	Night	32% 8% 15% 28% 17% 1	1598
	21st to end	Night	25% 7% 15% 26% 21% 5%	1929
September	1st to 10th	Night	32% 5% 14% 25% 18% 6%	1906
	11th to 20th	Night	29% 6% 11% 26% 27% 3	1980
	21st to end	Night	35% 4 9% 23% 26% 3	1980
October	1st to 10th	Night	31% 5% 10% 27% 23% 3	1980
	11th to 20th	Night	40% 5% 10% 24% 20% 2	2146
	21st to end	Night	46% 4 9% 22% 16% 3	2491
November	1st to 10th	Night	38% 4 11% 21% 22% 4	2406
	11th to 20th	Night	45% 4 9% 22% 18% 3	2470
	21st to end	Night	52% 4 11% 21% 11% 1	2470
December	1st to 10th	Night	57% 5% 10% 19% 8% 1	2470
	11th to 20th	Night	56% 4 10% 20% 9% 1	3044
	21st to end	Night	70% 4 8% 13% 4	4532

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	25% 19% 36% 14% 5%	270
	11th to 20th	Day	27% 16% 40% 14% 3	248
	21st to end	Day	29% 20% 33% 16% 2	264
February	1st to 10th	Day	32% 20% 34% 12% 3	240
	11th to 20th	Day	30% 23% 33% 12% 1	240
	21st to end	Day	29% 18% 43% 9% 1	198
March	1st to 10th	Day	22% 25% 39% 13% 2	265
	11th to 20th	Day	25% 14% 35% 20% 6%	420
	21st to end	Day	30% 15% 30% 19% 5%	462
April	1st to 10th	Day	19% 16% 28% 24% 11% 1	420
	11th to 20th	Day	22% 16% 25% 22% 12% 4	412
	21st to end	Day	23% 13% 33% 19% 10% 2	420
May	1st to 10th	Day	24% 10% 33% 20% 8% 5%	423
	11th to 20th	Day	21% 6% 29% 24% 15% 6%	447
	21st to end	Day	14% 4 23% 27% 21% 12%	485
June	1st to 10th	Day	12% 5% 20% 30% 24% 9%	450
	11th to 20th	Day	13% 4 20% 31% 25% 7%	590
	21st to end	Day	10% 5% 23% 31% 22% 9%	630
July	1st to 10th	Day	13% 4 13% 25% 23% 21%	621
	11th to 20th	Day	9% 3 17% 30% 26% 15%	499
	21st to end	Day	11% 2 15% 28% 27% 16%	488
August	1st to 10th	Day	11% 3 11% 27% 30% 18%	446
	11th to 20th	Day	11% 4 15% 30% 25% 14%	439
	21st to end	Day	9% 4 12% 29% 30% 16%	495
September	1st to 10th	Day	12% 3 15% 28% 30% 12%	450
	11th to 20th	Day	11% 3 13% 25% 33% 15%	450
	21st to end	Day	15% 8% 21% 25% 22% 9%	450
October	1st to 10th	Day	10% 6% 23% 34% 19% 8%	450
	11th to 20th	Day	16% 12% 31% 24% 13% 4	450
	21st to end	Day	27% 8% 36% 23% 6% 1	379
November	1st to 10th	Day	14% 11% 34% 26% 11% 4	270
	11th to 20th	Day	23% 17% 29% 21% 8% 2	270
	21st to end	Day	24% 12% 37% 22% 4	270
December	1st to 10th	Day	23% 18% 35% 17% 6% 1	270
	11th to 20th	Day	22% 19% 37% 17% 6%	270
	21st to end	Day	32% 15% 33% 16% 3	297
January	1st to 10th	Night	23% 16% 33% 22% 5%	819
	11th to 20th	Night	28% 14% 32% 23% 3	732
	21st to end	Night	21% 14% 37% 25% 3	792
February	1st to 10th	Night	29% 10% 34% 25% 2	720
	11th to 20th	Night	24% 13% 37% 24% 2	703
	21st to end	Night	30% 10% 37% 22% 2	592
March	1st to 10th	Night	22% 12% 35% 25% 6%	720
	11th to 20th	Night	23% 11% 35% 25% 6% 1	720
	21st to end	Night	23% 8% 33% 28% 7%	792
April	1st to 10th	Night	19% 10% 35% 28% 8%	613
	11th to 20th	Night	19% 8% 32% 29% 11% 2	533
	21st to end	Night	19% 6% 36% 29% 8% 1	540
May	1st to 10th	Night	22% 5% 31% 29% 12% 1	540
	11th to 20th	Night	19% 4 22% 35% 18% 2	531
	21st to end	Night	9% 2 19% 39% 26% 5%	584
June	1st to 10th	Night	9% 2 18% 45% 24% 2	540
	11th to 20th	Night	10% 4 13% 43% 28% 3	540
	21st to end	Night	6% 2 18% 45% 27% 2	540
July	1st to 10th	Night	12% 2 9% 33% 33% 10%	525
	11th to 20th	Night	8% 2 11% 39% 36% 5%	522
	21st to end	Night	10% 2 10% 41% 34% 4	591
August	1st to 10th	Night	9% 2 6% 42% 36% 4	537
	11th to 20th	Night	9% 2 10% 44% 30% 5%	534
	21st to end	Night	7% 1 12% 37% 36% 7%	594
September	1st to 10th	Night	13% 2 13% 32% 36% 5%	646
	11th to 20th	Night	9% 3 15% 34% 34% 6%	720
	21st to end	Night	15% 5% 21% 32% 25% 2	720
October	1st to 10th	Night	12% 4 22% 36% 23% 4	720
	11th to 20th	Night	17% 7% 28% 33% 13% 1	720
	21st to end	Night	23% 7% 33% 26% 11%	792
November	1st to 10th	Night	17% 6% 31% 30% 15% 1	740
	11th to 20th	Night	20% 12% 31% 26% 10% 1	760
	21st to end	Night	24% 11% 27% 30% 8% 1	760
December	1st to 10th	Night	27% 10% 33% 24% 6%	760
	11th to 20th	Night	25% 9% 33% 26% 6% 1	760
	21st to end	Night	29% 11% 32% 25% 3	836

Page generated at 2024-01-10 19:35:24. Version ac07

Copyright 2024 Attilla Danko