Slidell
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Slidell clear sky chart from 2005-11-05 to 2017-04-26.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
61%
14515
23%
45549
20%
14473
66%
14473
31%
27125

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
45%
719
26%
2148
14%
716
55%
716
30%
1308
January16th to endNight
41%
768
26%
2304
15%
768
49%
768
28%
1456
February1st to 15thNight
46%
704
26%
2112
15%
701
54%
701
32%
1282
February16th to endNight
41%
631
23%
1893
12%
631
49%
631
28%
1207
March1st to 15thNight
46%
642
24%
2082
15%
642
54%
642
26%
1285
March16th to endNight
60%
576
25%
2025
22%
576
65%
576
32%
1101
April1st to 15thNight
55%
539
25%
1797
21%
539
63%
539
31%
1027
April16th to endNight
60%
528
27%
1760
26%
528
66%
528
37%
922
May1st to 15thNight
69%
494
22%
1649
24%
494
72%
494
31%
943
May16th to endNight
77%
513
21%
1710
23%
513
78%
513
34%
958
June1st to 15thNight
82%
495
15%
1521
18%
495
82%
495
34%
911
June16th to endNight
76%
495
15%
1495
17%
495
76%
495
31%
926
July1st to 15thNight
80%
465
14%
1418
16%
465
80%
465
30%
890
July16th to endNight
77%
522
9%
1632
12%
489
76%
489
24%
1053
August1st to 15thNight
85%
494
13%
1638
17%
491
86%
491
32%
952
August16th to endNight
76%
525
13%
1750
16%
525
76%
525
25%
1115
September1st to 15thNight
72%
495
21%
1650
24%
495
73%
495
25%
1047
September16th to endNight
73%
638
27%
1796
24%
638
73%
638
34%
1108
October1st to 15thNight
76%
660
33%
1884
28%
660
78%
660
51%
973
October16th to endNight
62%
704
34%
2112
29%
704
67%
704
41%
1153
November1st to 15thNight
64%
700
33%
2121
30%
700
68%
700
38%
1198
November16th to endNight
56%
720
30%
2340
26%
720
64%
720
36%
1275
December1st to 15thNight
51%
720
24%
2340
20%
720
57%
720
27%
1427
December16th to endNight
42%
768
19%
2372
15%
768
46%
768
21%
1608

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 ForecastData
Points
Cloud CoverDay
10%5%25%5%35%5%6%8%40%
46051
Night
10%42442445%8%47%
45763
TransparencyDay
36%8%14%19%16%6%
45768
Night
33%7%13%20%17%8%
45551
SeeingDay
11%210%23%32%20%
4599
Night
11%315%29%30%10%
14519

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
13%5%245%35%45%5%42%
1790
16th to endDay
18%5%2433343445%
1920
February1st to 15thDay
13%5%2442335%7%47%
1750
16th to endDay
15%6%45%42336%6%41%
1580
March1st to 15thDay
15%5%34324447%43%
1887
16th to endDay
10%5%35%5%2445%7%46%
2195
April1st to 15thDay
11%425%5%25%5%7%9%41%
2151
16th to endDay
11%5%25%4145%6%9%44%
2111
May1st to 15thDay
10%425%435%5%6%10%40%
1971
16th to endDay
8%4145%35%5%6%10%43%
2052
June1st to 15thDay
5%425%6%49%8%8%12%31%
2098
16th to endDay
45%36%7%48%8%10%13%28%
2116
July1st to 15thDay
7%5%37%7%5%8%8%9%9%26%
2115
16th to endDay
8%5%37%6%5%7%7%9%12%24%
2108
August1st to 15thDay
8%426%6%48%8%9%12%28%
1980
16th to endDay
10%5%36%7%46%7%8%10%26%
2100
September1st to 15thDay
10%6%35%5%36%6%8%10%31%
1980
16th to endDay
8%5%245%45%6%6%9%39%
1821
October1st to 15thDay
5%31432445%7%57%
1744
16th to endDay
7%213423347%58%
1760
November1st to 15thDay
8%423424347%54%
1734
16th to endDay
8%313423445%57%
1620
December1st to 15thDay
14%7%2432435%5%44%
1620
16th to endDay
19%7%25%6%34437%35%
1848
January1st to 15thNight
13%5%2442435%7%47%
2148
16th to endNight
18%6%14323345%45%
2304
February1st to 15thNight
13%5%14423447%48%
2103
16th to endNight
17%7%23323346%44%
1893
March1st to 15thNight
14%4244245%5%6%43%
2082
16th to endNight
11%424224438%52%
2025
April1st to 15thNight
10%5%244335%46%49%
1797
16th to endNight
8%3133235%6%8%53%
1760
May1st to 15thNight
8%324435%46%10%46%
1649
16th to endNight
5%223435%5%5%9%51%
1709
June1st to 15thNight
33145%35%5%8%11%45%
1521
16th to endNight
43245%36%6%6%10%44%
1495
July1st to 15thNight
3325%5%35%6%7%14%42%
1510
16th to endNight
4325%7%36%6%9%14%34%
1752
August1st to 15thNight
2313435%7%9%14%44%
1650
16th to endNight
7%415%5%35%6%8%13%38%
1750
September1st to 15thNight
8%415%5%36%6%6%11%39%
1650
16th to endNight
7%5%235%35%45%9%47%
1796
October1st to 15thNight
4313323337%63%
1884
16th to endNight
9%313322336%59%
2112
November1st to 15thNight
8%5%13423336%55%
2121
16th to endNight
8%42332443457%
2340
December1st to 15thNight
12%5%35%5%24447%45%
2340
16th to endNight
18%7%35%5%24446%37%
2372

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
40%5%7%16%20%10%
1791
16th to endDay
42%45%17%20%9%
1920
February1st to 15thDay
35%410%16%22%10%
1752
16th to endDay
41%5%8%17%19%7%
1580
March1st to 15thDay
39%5%9%21%17%5%
1887
16th to endDay
35%5%12%19%21%6%
2197
April1st to 15thDay
35%7%12%19%18%7%
2151
16th to endDay
32%5%14%24%17%4
2111
May1st to 15thDay
33%8%15%23%12%6%
1971
16th to endDay
31%7%17%25%16%1
2056
June1st to 15thDay
34%11%20%21%10%1
2098
16th to endDay
37%11%21%20%8%
2116
July1st to 15thDay
41%13%22%16%4
1978
16th to endDay
42%13%24%15%2
1965
August1st to 15thDay
37%15%24%17%5%
1968
16th to endDay
42%14%19%14%6%2
2100
September1st to 15thDay
38%11%20%17%9%2
1980
16th to endDay
33%9%14%18%17%6%
1821
October1st to 15thDay
22%412%20%23%15%
1744
16th to endDay
25%37%17%28%17%
1760
November1st to 15thDay
27%5%8%20%29%8%
1734
16th to endDay
27%5%7%18%25%15%
1620
December1st to 15thDay
39%410%21%17%5%
1620
16th to endDay
47%410%17%15%4
1848
January1st to 15thNight
36%49%16%21%11%
2148
16th to endNight
41%36%14%22%11%
2304
February1st to 15thNight
36%37%19%20%11%
2112
16th to endNight
40%46%17%18%12%
1893
March1st to 15thNight
38%6%9%17%21%6%
2082
16th to endNight
31%5%12%20%22%7%
2025
April1st to 15thNight
33%5%11%22%15%10%
1797
16th to endNight
26%5%12%26%20%7%
1760
May1st to 15thNight
30%8%14%25%16%4
1650
16th to endNight
27%8%16%28%16%2
1711
June1st to 15thNight
29%9%20%27%12%
1521
16th to endNight
31%11%23%23%10%
1495
July1st to 15thNight
29%13%30%21%4
1418
16th to endNight
35%13%30%18%2
1632
August1st to 15thNight
24%14%32%21%6%
1638
16th to endNight
35%12%26%15%7%3
1750
September1st to 15thNight
37%10%18%17%12%4
1650
16th to endNight
32%8%14%20%17%7%
1796
October1st to 15thNight
21%312%21%22%17%
1884
16th to endNight
27%45%15%27%20%
2112
November1st to 15thNight
30%47%19%28%11%
2121
16th to endNight
29%46%17%22%18%
2340
December1st to 15thNight
38%5%9%21%18%6%
2340
16th to endNight
47%5%7%18%14%6%
2372

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
21%5%24%35%11%2
90
16th to endDay
21%9%32%30%6%
96
February1st to 15thDay
11%10%20%45%11%2
90
16th to endDay
11%333%38%13%
81
March1st to 15thDay
21%131%44%2
90
16th to endDay
13%423%32%24%1
181
April1st to 15thDay
12%421%36%22%
270
16th to endDay
11%314%36%29%5%
254
May1st to 15thDay
12%113%37%31%3
228
16th to endDay
10%15%23%38%21%
267
June1st to 15thDay
9%320%39%27%
255
16th to endDay
5%213%43%34%
379
July1st to 15thDay
6%112%42%35%
372
16th to endDay
9%35%31%50%
270
August1st to 15thDay
9%17%35%44%
253
16th to endDay
7%28%40%39%
268
September1st to 15thDay
14%213%41%27%
255
16th to endDay
10%1422%40%20%
254
October1st to 15thDay
29%30%43%13%
184
16th to endDay
9%28%38%32%9%
96
November1st to 15thDay
15%11%37%27%7%
90
16th to endDay
6%424%41%16%6%
90
December1st to 15thDay
25%417%35%14%2
90
16th to endDay
33%5%26%20%14%
96
January1st to 15thNight
16%5%25%40%10%1
720
16th to endNight
19%6%27%34%11%
768
February1st to 15thNight
14%329%36%14%
704
16th to endNight
18%5%29%35%11%
631
March1st to 15thNight
15%427%35%16%
642
16th to endNight
13%416%36%26%1
576
April1st to 15thNight
13%420%34%25%1
539
16th to endNight
9%119%37%28%3
528
May1st to 15thNight
8%112%43%31%3
495
16th to endNight
5%16%26%47%11%
515
June1st to 15thNight
5%321%55%14%
495
16th to endNight
5%1311%49%28%
495
July1st to 15thNight
5%18%50%32%
465
16th to endNight
418%46%38%
522
August1st to 15thNight
317%49%37%
494
16th to endNight
9%211%40%35%
525
September1st to 15thNight
9%1411%42%30%
495
16th to endNight
10%1427%47%10%
638
October1st to 15thNight
6%18%32%42%9%
660
16th to endNight
10%415%29%31%7%
704
November1st to 15thNight
9%315%40%24%7%
700
16th to endNight
9%422%38%22%2
720
December1st to 15thNight
15%6%21%34%20%2
720
16th to endNight
20%6%23%33%14%1
768
Page generated at 2017-04-27 16:48:48. Version ac04

Copyright 2017 A. Danko


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