Dauphin Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dauphin Island clear sky chart from 2005-11-05 to 2017-12-04.

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
62%
15436
23%
47960
19%
15392
66%
15392
31%
28501

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
44%
720
23%
2151
12%
716
54%
716
27%
1348
January16th to endNight
39%
768
25%
2304
13%
768
49%
768
26%
1485
February1st to 15thNight
45%
703
28%
2108
16%
699
54%
699
32%
1261
February16th to endNight
44%
631
22%
1893
12%
631
52%
631
27%
1217
March1st to 15thNight
50%
720
22%
2160
13%
720
57%
720
30%
1334
March16th to endNight
63%
618
26%
2004
22%
618
68%
618
35%
1107
April1st to 15thNight
58%
539
25%
1797
23%
539
64%
539
33%
1012
April16th to endNight
69%
540
29%
1800
30%
540
73%
540
42%
903
May1st to 15thNight
70%
539
21%
1799
22%
539
73%
539
36%
979
May16th to endNight
74%
561
23%
1699
23%
561
75%
561
36%
986
June1st to 15thNight
79%
540
14%
1620
16%
540
79%
540
34%
953
June16th to endNight
79%
540
15%
1620
16%
540
79%
540
33%
973
July1st to 15thNight
81%
510
12%
1620
13%
510
81%
510
29%
988
July16th to endNight
78%
564
10%
1772
13%
531
78%
531
26%
1116
August1st to 15thNight
82%
539
12%
1788
15%
536
82%
536
29%
1077
August16th to endNight
69%
573
14%
1910
17%
573
69%
573
23%
1226
September1st to 15thNight
71%
582
17%
1842
17%
582
72%
582
26%
1158
September16th to endNight
74%
717
26%
1980
22%
717
76%
717
36%
1217
October1st to 15thNight
73%
720
30%
1980
25%
720
75%
720
43%
1125
October16th to endNight
62%
768
33%
2259
29%
768
66%
768
39%
1270
November1st to 15thNight
63%
760
30%
2432
29%
760
68%
760
37%
1331
November16th to endNight
56%
780
30%
2535
25%
780
65%
780
37%
1360
December1st to 15thNight
51%
736
24%
2391
20%
736
58%
736
27%
1445
December16th to endNight
45%
768
19%
2496
16%
768
51%
768
23%
1630

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
9%4244245%6%9%45%
48497
Night
9%42442445%8%47%
48185
TransparencyDay
33%8%15%20%16%5%
48219
Night
32%7%14%20%17%7%
47967
SeeingDay
11%110%19%34%22%
5354
Night
11%315%25%30%14%
15440

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
10%5%25%5%3445%8%44%
1784
16th to endDay
17%6%3332433445%
1920
February1st to 15thDay
11%5%2442325%7%49%
1750
16th to endDay
12%6%24334347%46%
1580
March1st to 15thDay
11%5%25%424447%47%
1800
16th to endDay
8%425%42435%7%49%
2228
April1st to 15thDay
10%42442445%7%49%
2151
16th to endDay
7%42331445%7%55%
2160
May1st to 15thDay
6%323425%5%6%10%49%
2151
16th to endDay
5%2245%245%6%9%50%
2412
June1st to 15thDay
6%324435%6%9%13%40%
2340
16th to endDay
7%325%5%35%6%8%13%38%
2340
July1st to 15thDay
6%326%7%47%7%8%13%30%
2238
16th to endDay
7%435%5%37%7%9%14%31%
2276
August1st to 15thDay
7%425%437%8%11%14%30%
2160
16th to endDay
12%415%5%35%6%7%10%37%
2292
September1st to 15thDay
9%426%5%35%6%7%9%40%
2106
16th to endDay
7%3144345%6%9%49%
1980
October1st to 15thDay
6%21231345%9%58%
1980
16th to endDay
7%314423435%59%
1962
November1st to 15thDay
9%313313446%58%
1753
16th to endDay
6%31442435%7%57%
1755
December1st to 15thDay
10%5%26%5%24447%46%
1651
16th to endDay
17%8%47%5%24346%35%
1728
January1st to 15thNight
10%5%25%335%5%5%7%45%
2151
16th to endNight
16%8%24423345%44%
2304
February1st to 15thNight
13%423323346%50%
2103
16th to endNight
14%6%24424435%46%
1893
March1st to 15thNight
11%5%25%42335%8%45%
2160
16th to endNight
9%41342435%7%53%
2004
April1st to 15thNight
8%5%24325%446%52%
1797
16th to endNight
6%313413448%59%
1800
May1st to 15thNight
7%32442445%10%51%
1799
16th to endNight
6%2244345%6%10%50%
1699
June1st to 15thNight
5%415%335%5%5%14%44%
1620
16th to endNight
5%3244345%9%14%42%
1620
July1st to 15thNight
5%313436%6%8%14%41%
1718
16th to endNight
4325%5%36%6%9%15%36%
1892
August1st to 15thNight
5%23436%8%10%14%39%
1800
16th to endNight
9%5%25%5%346%6%10%41%
1910
September1st to 15thNight
6%425%435%7%7%12%39%
1842
16th to endNight
8%4243345%6%9%46%
1980
October1st to 15thNight
5%4135%2335%7%57%
1980
16th to endNight
9%423323335%58%
2259
November1st to 15thNight
8%414423347%54%
2432
16th to endNight
8%324323446%55%
2535
December1st to 15thNight
11%5%25%5%25%446%46%
2391
16th to endNight
15%7%35%5%3446%6%38%
2496

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
36%5%10%17%21%7%
1785
16th to endDay
42%5%6%15%21%8%
1920
February1st to 15thDay
34%410%17%23%8%
1752
16th to endDay
36%5%10%18%21%7%
1580
March1st to 15thDay
35%6%10%22%19%5%
1800
16th to endDay
33%7%14%20%18%6%
2229
April1st to 15thDay
34%410%23%19%6%
2151
16th to endDay
27%5%15%27%19%5%
2160
May1st to 15thDay
28%7%16%23%16%7%
2151
16th to endDay
27%8%17%28%16%2
2416
June1st to 15thDay
31%10%21%26%9%
2340
16th to endDay
34%11%22%20%9%
2340
July1st to 15thDay
40%16%23%16%3
2107
16th to endDay
39%15%23%18%3
2133
August1st to 15thDay
35%16%26%15%5%
2148
16th to endDay
38%13%21%17%6%1
2292
September1st to 15thDay
37%10%21%16%11%3
2106
16th to endDay
30%10%14%22%17%4
1980
October1st to 15thDay
22%5%13%23%21%12%
1980
16th to endDay
28%46%16%27%17%
1962
November1st to 15thDay
26%5%10%22%26%8%
1753
16th to endDay
26%6%10%19%23%12%
1755
December1st to 15thDay
37%5%12%21%18%3
1651
16th to endDay
50%5%8%18%12%4
1728
January1st to 15thNight
38%5%9%15%23%8%
2151
16th to endNight
42%47%14%23%8%
2304
February1st to 15thNight
33%5%6%19%22%11%
2112
16th to endNight
40%47%14%21%10%
1893
March1st to 15thNight
36%6%12%17%22%5%
2160
16th to endNight
30%412%22%21%8%
2004
April1st to 15thNight
31%5%12%18%22%8%
1797
16th to endNight
23%413%31%20%7%
1800
May1st to 15thNight
27%6%15%23%19%6%
1800
16th to endNight
28%8%16%23%20%1
1701
June1st to 15thNight
28%10%24%24%11%
1620
16th to endNight
29%10%26%22%10%
1620
July1st to 15thNight
28%14%31%20%5%
1620
16th to endNight
31%15%30%20%2
1772
August1st to 15thNight
27%15%33%20%3
1788
16th to endNight
36%12%24%18%5%2
1910
September1st to 15thNight
33%12%21%16%12%4
1842
16th to endNight
30%8%18%19%16%5%
1980
October1st to 15thNight
25%6%10%22%20%14%
1980
16th to endNight
29%36%14%26%19%
2259
November1st to 15thNight
29%37%21%28%8%
2432
16th to endNight
28%49%19%22%14%
2535
December1st to 15thNight
37%5%10%23%18%5%
2391
16th to endNight
43%5%9%20%14%5%
2496

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
12%6%25%28%18%7%
90
16th to endDay
22%6%22%35%11%1
96
February1st to 15thDay
6%6%31%22%30%3
90
16th to endDay
9%219%44%23%
81
March1st to 15thDay
16%124%43%14%
90
16th to endDay
14%220%33%25%4
246
April1st to 15thDay
17%315%32%27%3
270
16th to endDay
7%117%27%37%8%
270
May1st to 15thDay
5%215%28%39%8%
288
16th to endDay
9%8%22%42%16%
331
June1st to 15thDay
13%214%46%21%
315
16th to endDay
11%310%37%36%
315
July1st to 15thDay
8%15%29%54%
305
16th to endDay
9%26%36%45%
326
August1st to 15thDay
11%36%36%42%
313
16th to endDay
12%38%31%43%
332
September1st to 15thDay
13%16%11%32%34%
315
16th to endDay
11%5%17%41%23%
314
October1st to 15thDay
8%8%28%36%16%
315
16th to endDay
11%210%28%31%16%
186
November1st to 15thDay
18%5%24%40%10%
135
16th to endDay
5%122%23%35%11%
135
December1st to 15thDay
11%318%35%28%5%
100
16th to endDay
27%5%19%16%28%3
96
January1st to 15thNight
13%8%27%34%13%2
720
16th to endNight
19%9%26%27%15%1
768
February1st to 15thNight
15%5%28%30%17%2
704
16th to endNight
16%7%25%31%18%
631
March1st to 15thNight
13%5%23%34%20%2
720
16th to endNight
11%415%33%30%5%
618
April1st to 15thNight
10%318%38%25%3
539
16th to endNight
8%215%33%34%5%
540
May1st to 15thNight
9%13%30%38%7%
540
16th to endNight
7%7%20%47%16%
563
June1st to 15thNight
7%315%49%24%
540
16th to endNight
6%18%47%34%
540
July1st to 15thNight
5%5%39%48%
510
16th to endNight
5%25%40%45%
564
August1st to 15thNight
6%1437%49%
539
16th to endNight
12%310%37%35%
573
September1st to 15thNight
8%16%12%36%34%
582
16th to endNight
9%422%46%15%
717
October1st to 15thNight
9%9%31%36%11%
720
16th to endNight
13%415%27%30%9%
768
November1st to 15thNight
10%316%32%28%8%
760
16th to endNight
9%422%32%24%5%
780
December1st to 15thNight
13%5%22%28%23%5%
736
16th to endNight
17%5%24%30%18%2
768
Page generated at 2017-12-05 09:19:01. Version ac04

Copyright 2017 A. Danko


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