Tatlayoko Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tatlayoko Lake clear sky chart from 2005-11-06 to 2024-02-05.

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	5% 9% 4 9% 7% 4 6% 6% 7% 9% 32%	77597
	Night	4 8% 4 8% 7% 5% 7% 7% 8% 10% 33%	81213
Transparency	Day	43% 10% 16% 20% 9% 1	77298
	Night	41% 11% 18% 20% 9% 1	81092
Seeing	Day	14% 22% 32% 21% 9% 2	14565
	Night	9% 16% 39% 25% 10% 1	22674

By Month

Percentage Cloud Cover NW (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	1 8% 5% 10% 8% 6% 8% 8% 10% 10% 25%	2219
	11th to 20th	Day	1 7% 4 9% 9% 5% 6% 7% 9% 9% 33%	2199
	21st to end	Day	1 7% 4 8% 8% 5% 8% 8% 9% 13% 27%	2442
February	1st to 10th	Day	2 7% 4 11% 11% 5% 9% 8% 8% 10% 24%	1635
	11th to 20th	Day	2 7% 5% 11% 8% 5% 7% 8% 8% 8% 31%	1575
	21st to end	Day	2 7% 5% 14% 9% 5% 9% 7% 8% 7% 28%	1332
March	1st to 10th	Day	1 6% 4 12% 9% 5% 8% 8% 9% 11% 27%	1834
	11th to 20th	Day	1 7% 6% 9% 9% 5% 9% 8% 10% 10% 27%	1980
	21st to end	Day	3 11% 7% 12% 10% 5% 7% 6% 8% 8% 23%	2200
April	1st to 10th	Day	3 12% 6% 12% 10% 5% 7% 7% 7% 9% 21%	2180
	11th to 20th	Day	3 13% 7% 11% 7% 4 6% 6% 7% 10% 25%	2308
	21st to end	Day	3 13% 6% 8% 8% 5% 6% 8% 8% 9% 25%	2399
May	1st to 10th	Day	5% 13% 6% 9% 8% 4 7% 6% 7% 8% 27%	2520
	11th to 20th	Day	7% 15% 5% 8% 7% 5% 7% 7% 6% 8% 26%	2553
	21st to end	Day	15% 12% 5% 9% 6% 4 6% 5% 6% 7% 24%	2917
June	1st to 10th	Day	12% 11% 5% 9% 7% 3 6% 6% 6% 8% 28%	2700
	11th to 20th	Day	13% 13% 5% 8% 7% 4 6% 6% 7% 8% 23%	2700
	21st to end	Day	9% 9% 4 10% 8% 4 5% 6% 6% 7% 30%	2700
July	1st to 10th	Day	9% 8% 4 7% 6% 4 5% 5% 6% 7% 39%	2700
	11th to 20th	Day	10% 7% 3 6% 6% 4 6% 5% 6% 7% 40%	2700
	21st to end	Day	6% 7% 4 6% 6% 4 5% 5% 6% 8% 43%	2938
August	1st to 10th	Day	9% 7% 3 6% 5% 4 5% 5% 6% 7% 44%	2550
	11th to 20th	Day	5% 6% 3 5% 6% 3 6% 6% 6% 8% 46%	2298
	21st to end	Day	9% 10% 4 7% 7% 4 6% 6% 7% 8% 32%	2574
September	1st to 10th	Day	7% 8% 2 6% 7% 3 6% 4 7% 8% 42%	2186
	11th to 20th	Day	9% 13% 4 6% 5% 4 4 6% 5% 7% 37%	2100
	21st to end	Day	7% 9% 3 7% 6% 3 4 7% 8% 9% 37%	1936
October	1st to 10th	Day	6% 12% 4 9% 8% 4 5% 5% 7% 8% 32%	1800
	11th to 20th	Day	4 10% 3 8% 7% 4 6% 7% 7% 11% 33%	1800
	21st to end	Day	2 8% 5% 9% 7% 4 5% 7% 8% 9% 37%	1717
November	1st to 10th	Day	4 10% 3 8% 7% 4 6% 8% 8% 12% 29%	1488
	11th to 20th	Day	2 6% 4 9% 7% 6% 6% 7% 10% 12% 32%	1520
	21st to end	Day	2 9% 5% 7% 7% 6% 7% 6% 9% 9% 34%	1440
December	1st to 10th	Day	2 3 4 9% 10% 4 6% 7% 9% 10% 36%	1330
	11th to 20th	Day	1 10% 6% 10% 8% 4 7% 6% 9% 8% 31%	1685
	21st to end	Day	1 4 4 8% 7% 4 7% 8% 12% 13% 34%	2442
January	1st to 10th	Night	2 9% 5% 13% 11% 6% 8% 7% 8% 10% 23%	4726
	11th to 20th	Night	2 7% 4 8% 7% 6% 9% 8% 9% 13% 27%	4699
	21st to end	Night	2 8% 4 9% 8% 5% 7% 8% 8% 11% 29%	5214
February	1st to 10th	Night	2 8% 4 9% 9% 5% 8% 8% 8% 10% 28%	2415
	11th to 20th	Night	2 8% 5% 9% 9% 4 7% 6% 8% 10% 33%	2272
	21st to end	Night	1 6% 5% 12% 11% 6% 6% 7% 8% 7% 30%	1924
March	1st to 10th	Night	1 6% 6% 10% 8% 5% 7% 7% 8% 12% 29%	2122
	11th to 20th	Night	4 2 6% 8% 5% 7% 8% 9% 14% 37%	1979
	21st to end	Night	2 8% 5% 10% 7% 5% 6% 8% 9% 10% 30%	2156
April	1st to 10th	Night	2 8% 6% 12% 9% 4 7% 7% 7% 10% 28%	1778
	11th to 20th	Night	2 10% 6% 9% 7% 4 6% 6% 8% 10% 31%	1601
	21st to end	Night	2 11% 5% 7% 8% 4 5% 6% 7% 9% 35%	1560
May	1st to 10th	Night	5% 10% 4 7% 7% 4 5% 6% 7% 10% 34%	1440
	11th to 20th	Night	7% 11% 2 6% 7% 5% 6% 6% 8% 11% 31%	1340
	21st to end	Night	15% 9% 3 10% 7% 4 7% 7% 6% 8% 24%	1358
June	1st to 10th	Night	11% 9% 2 7% 7% 5% 6% 6% 6% 9% 31%	1260
	11th to 20th	Night	13% 8% 4 6% 6% 5% 5% 5% 7% 10% 33%	1260
	21st to end	Night	11% 8% 3 6% 6% 3 6% 5% 6% 8% 38%	1260
July	1st to 10th	Night	9% 7% 3 5% 5% 4 6% 5% 6% 8% 41%	1260
	11th to 20th	Night	7% 6% 2 3 4 3 6% 7% 7% 11% 44%	1260
	21st to end	Night	5% 5% 2 4 4 3 5% 5% 7% 10% 49%	1379
August	1st to 10th	Night	8% 5% 3 5% 5% 3 4 4 5% 8% 49%	1387
	11th to 20th	Night	5% 5% 2 4 5% 3 6% 7% 6% 8% 51%	1600
	21st to end	Night	8% 8% 3 6% 6% 4 6% 5% 7% 8% 39%	1782
September	1st to 10th	Night	8% 7% 2 5% 5% 3 3 5% 6% 7% 49%	1773
	11th to 20th	Night	10% 9% 3 5% 5% 3 6% 5% 6% 6% 42%	1858
	21st to end	Night	8% 9% 4 6% 5% 4 6% 6% 8% 9% 36%	2024
October	1st to 10th	Night	8% 12% 4 7% 6% 3 5% 5% 5% 8% 37%	2160
	11th to 20th	Night	4 12% 3 6% 6% 4 6% 8% 8% 10% 33%	2160
	21st to end	Night	3 8% 4 7% 7% 5% 5% 7% 7% 10% 35%	2636
November	1st to 10th	Night	2 9% 5% 10% 9% 5% 7% 7% 8% 11% 28%	2590
	11th to 20th	Night	2 8% 4 6% 8% 4 6% 7% 9% 11% 34%	2660
	21st to end	Night	2 7% 4 8% 7% 5% 7% 7% 9% 10% 34%	2736
December	1st to 10th	Night	2 6% 4 9% 7% 4 7% 7% 9% 11% 34%	2850
	11th to 20th	Night	2 10% 5% 11% 9% 4 7% 8% 8% 9% 28%	3520
	21st to end	Night	1 5% 4 9% 8% 5% 8% 8% 11% 12% 30%	5214

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	47% 14% 15% 18% 5% 1	2219
	11th to 20th	Day	42% 9% 17% 15% 8% 9%	2220
	21st to end	Day	44% 15% 16% 17% 8% 1	2442
February	1st to 10th	Day	48% 13% 14% 15% 9% 1	1635
	11th to 20th	Day	44% 12% 14% 19% 11%	1584
	21st to end	Day	46% 9% 16% 19% 9% 1	1332
March	1st to 10th	Day	41% 13% 15% 20% 10% 1	1834
	11th to 20th	Day	40% 11% 17% 23% 8% 1	1980
	21st to end	Day	49% 12% 16% 19% 5%	2200
April	1st to 10th	Day	53% 11% 15% 13% 8%	2180
	11th to 20th	Day	49% 11% 12% 16% 12%	2308
	21st to end	Day	49% 10% 14% 19% 6% 1	2399
May	1st to 10th	Day	49% 10% 16% 16% 8%	2520
	11th to 20th	Day	50% 11% 15% 17% 6% 1	2556
	21st to end	Day	54% 8% 12% 18% 7% 1	2918
June	1st to 10th	Day	49% 8% 14% 15% 11% 3	2700
	11th to 20th	Day	52% 8% 15% 17% 7%	2700
	21st to end	Day	45% 10% 14% 20% 9% 2	2700
July	1st to 10th	Day	40% 8% 15% 21% 13% 2	2626
	11th to 20th	Day	38% 8% 16% 23% 13% 1	2619
	21st to end	Day	33% 8% 16% 25% 15% 3	2775
August	1st to 10th	Day	34% 8% 18% 29% 10% 2	2532
	11th to 20th	Day	30% 9% 17% 28% 13% 3	2298
	21st to end	Day	43% 11% 18% 21% 7% 1	2574
September	1st to 10th	Day	34% 8% 19% 27% 10% 2	2186
	11th to 20th	Day	41% 8% 13% 25% 10% 3	2100
	21st to end	Day	37% 11% 18% 22% 12% 1	1936
October	1st to 10th	Day	47% 9% 17% 20% 9%	1800
	11th to 20th	Day	40% 9% 19% 22% 9% 1	1800
	21st to end	Day	40% 10% 15% 21% 12% 1	1717
November	1st to 10th	Day	43% 12% 18% 22% 5% 1	1488
	11th to 20th	Day	40% 14% 18% 18% 10%	1520
	21st to end	Day	40% 10% 19% 20% 7% 3	1440
December	1st to 10th	Day	38% 13% 18% 21% 9% 1	1330
	11th to 20th	Day	44% 12% 22% 15% 7% 1	1688
	21st to end	Day	35% 13% 20% 22% 9% 1	2442
January	1st to 10th	Night	51% 12% 14% 16% 5% 1	4726
	11th to 20th	Night	43% 12% 17% 13% 7% 8%	4740
	21st to end	Night	41% 16% 21% 14% 8% 1	5214
February	1st to 10th	Night	44% 12% 18% 13% 12% 1	2415
	11th to 20th	Night	42% 10% 15% 20% 12% 1	2274
	21st to end	Night	46% 9% 15% 21% 9%	1924
March	1st to 10th	Night	40% 11% 19% 18% 12%	2122
	11th to 20th	Night	31% 11% 20% 28% 9% 1	1980
	21st to end	Night	41% 14% 19% 20% 6%	2156
April	1st to 10th	Night	44% 10% 19% 20% 6%	1778
	11th to 20th	Night	43% 9% 17% 20% 11%	1601
	21st to end	Night	42% 9% 18% 22% 9%	1560
May	1st to 10th	Night	41% 9% 21% 20% 9%	1440
	11th to 20th	Night	41% 11% 22% 21% 5% 1	1340
	21st to end	Night	52% 11% 16% 15% 6%	1358
June	1st to 10th	Night	44% 10% 16% 19% 9% 2	1260
	11th to 20th	Night	45% 9% 19% 20% 7%	1260
	21st to end	Night	40% 10% 15% 24% 9% 2	1260
July	1st to 10th	Night	36% 10% 15% 24% 12% 2	1225
	11th to 20th	Night	30% 13% 19% 27% 11%	1218
	21st to end	Night	25% 8% 21% 28% 16% 2	1302
August	1st to 10th	Night	32% 9% 17% 31% 9% 2	1380
	11th to 20th	Night	28% 9% 21% 28% 12% 3	1600
	21st to end	Night	39% 10% 21% 25% 4 1	1782
September	1st to 10th	Night	33% 7% 18% 30% 9% 2	1773
	11th to 20th	Night	38% 8% 16% 24% 12% 3	1858
	21st to end	Night	40% 8% 20% 24% 7% 1	2024
October	1st to 10th	Night	42% 10% 16% 25% 7%	2160
	11th to 20th	Night	40% 11% 18% 21% 10%	2160
	21st to end	Night	39% 12% 16% 23% 10% 1	2636
November	1st to 10th	Night	48% 12% 18% 15% 6% 1	2590
	11th to 20th	Night	39% 12% 20% 18% 10%	2660
	21st to end	Night	40% 14% 20% 16% 7% 4	2736
December	1st to 10th	Night	40% 13% 19% 18% 9% 1	2850
	11th to 20th	Night	49% 14% 17% 14% 6%	3516
	21st to end	Night	38% 13% 17% 18% 13% 1	5214

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	8% 19% 39% 22% 7% 4	180
	11th to 20th	Day	10% 23% 35% 22% 9% 2	180
	21st to end	Day	5% 22% 40% 18% 15%	198
February	1st to 10th	Day	15% 29% 36% 16% 3	348
	11th to 20th	Day	8% 29% 39% 18% 5% 1	335
	21st to end	Day	11% 30% 38% 14% 6% 1	280
March	1st to 10th	Day	13% 27% 28% 19% 10% 2	394
	11th to 20th	Day	12% 30% 34% 16% 6% 2	420
	21st to end	Day	17% 26% 32% 17% 7% 1	462
April	1st to 10th	Day	18% 29% 31% 16% 5% 1	420
	11th to 20th	Day	17% 24% 30% 17% 8% 2	412
	21st to end	Day	20% 25% 27% 19% 7% 2	420
May	1st to 10th	Day	14% 22% 33% 24% 7% 1	423
	11th to 20th	Day	17% 18% 29% 23% 11% 2	522
	21st to end	Day	19% 21% 29% 21% 8% 2	680
June	1st to 10th	Day	16% 27% 35% 16% 6% 1	630
	11th to 20th	Day	18% 25% 30% 18% 8% 1	630
	21st to end	Day	13% 20% 33% 23% 9% 3	630
July	1st to 10th	Day	12% 20% 33% 21% 11% 3	621
	11th to 20th	Day	12% 19% 32% 24% 10% 2	618
	21st to end	Day	8% 16% 33% 28% 10% 5%	684
August	1st to 10th	Day	12% 12% 26% 29% 16% 4	490
	11th to 20th	Day	8% 15% 29% 31% 14% 3	437
	21st to end	Day	13% 19% 32% 25% 9% 2	495
September	1st to 10th	Day	11% 22% 33% 22% 10% 2	450
	11th to 20th	Day	19% 20% 24% 24% 10% 3	450
	21st to end	Day	21% 24% 29% 18% 6% 1	450
October	1st to 10th	Day	20% 22% 26% 18% 11% 3	450
	11th to 20th	Day	16% 27% 27% 20% 8% 2	450
	21st to end	Day	17% 27% 31% 15% 8% 2	308
November	1st to 10th	Day	16% 28% 32% 17% 6%	180
	11th to 20th	Day	8% 24% 30% 25% 10% 2	180
	21st to end	Day	17% 21% 31% 18% 7% 6%	180
December	1st to 10th	Day	7% 22% 28% 28% 9% 6%	180
	11th to 20th	Day	9% 21% 43% 14% 9% 4	180
	21st to end	Day	9% 19% 39% 25% 7% 1	198
January	1st to 10th	Night	8% 23% 43% 19% 5% 2	850
	11th to 20th	Night	8% 20% 44% 23% 5% 1	850
	21st to end	Night	7% 21% 43% 19% 8% 1	935
February	1st to 10th	Night	9% 22% 40% 21% 7% 1	745
	11th to 20th	Night	6% 20% 41% 26% 8%	704
	21st to end	Night	5% 19% 45% 24% 6% 1	592
March	1st to 10th	Night	6% 19% 44% 21% 9%	720
	11th to 20th	Night	3 21% 45% 21% 9%	720
	21st to end	Night	8% 17% 38% 26% 10% 1	792
April	1st to 10th	Night	8% 14% 40% 29% 9% 1	698
	11th to 20th	Night	7% 15% 45% 24% 10%	533
	21st to end	Night	9% 14% 42% 28% 6% 1	480
May	1st to 10th	Night	10% 11% 36% 29% 13%	360
	11th to 20th	Night	11% 10% 33% 36% 9% 1	354
	21st to end	Night	17% 9% 33% 32% 8% 1	389
June	1st to 10th	Night	15% 10% 37% 31% 8%	360
	11th to 20th	Night	13% 8% 39% 30% 9%	360
	21st to end	Night	13% 6% 33% 39% 10%	360
July	1st to 10th	Night	10% 6% 32% 37% 15%	350
	11th to 20th	Night	10% 8% 32% 33% 16%	348
	21st to end	Night	5% 4 30% 37% 23% 2	394
August	1st to 10th	Night	10% 3 22% 36% 28% 2	358
	11th to 20th	Night	6% 3 26% 37% 27% 2	532
	21st to end	Night	12% 9% 31% 33% 15% 1	594
September	1st to 10th	Night	12% 10% 29% 31% 17% 1	693
	11th to 20th	Night	14% 12% 24% 26% 22% 3	720
	21st to end	Night	15% 18% 34% 22% 10%	720
October	1st to 10th	Night	18% 17% 28% 24% 12% 1	720
	11th to 20th	Night	11% 19% 38% 20% 12%	720
	21st to end	Night	11% 20% 41% 20% 7% 2	792
November	1st to 10th	Night	11% 22% 44% 18% 6%	740
	11th to 20th	Night	8% 22% 45% 20% 5% 1	760
	21st to end	Night	9% 21% 44% 18% 6% 1	796
December	1st to 10th	Night	6% 17% 42% 24% 9% 2	850
	11th to 20th	Night	8% 19% 44% 22% 5% 2	850
	21st to end	Night	7% 17% 51% 20% 5%	935

Page generated at 2024-02-02 02:20:27. Version ac07

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