Guana River Dam
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Guana River Dam clear sky chart from 2005-11-05 to 2017-08-12.

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
56%
15788
20%
46532
15%
15750
61%
15750
28%
29788

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
38%
717
20%
2327
13%
716
49%
716
23%
1461
January16th to endNight
40%
768
22%
2496
15%
768
50%
768
25%
1544
February1st to 15thNight
39%
701
22%
2119
14%
700
49%
700
28%
1297
February16th to endNight
39%
631
23%
1827
12%
631
50%
631
29%
1139
March1st to 15thNight
48%
720
28%
1980
16%
720
59%
720
38%
1166
March16th to endNight
52%
768
23%
2112
16%
768
58%
768
38%
1246
April1st to 15thNight
55%
718
22%
1976
15%
718
60%
718
37%
1183
April16th to endNight
60%
720
26%
1806
16%
720
65%
720
40%
1106
May1st to 15thNight
68%
557
25%
1637
19%
557
71%
557
40%
919
May16th to endNight
73%
561
21%
1682
16%
561
74%
561
33%
1018
June1st to 15thNight
69%
540
14%
1620
12%
540
69%
540
26%
1061
June16th to endNight
72%
540
10%
1620
9%
540
72%
540
24%
1115
July1st to 15thNight
71%
510
10%
1530
10%
510
71%
510
22%
1058
July16th to endNight
77%
564
10%
1595
10%
531
78%
531
24%
1087
August1st to 15thNight
72%
527
9%
1575
9%
524
73%
524
23%
1100
August16th to endNight
65%
657
11%
1799
11%
657
65%
657
21%
1322
September1st to 15thNight
64%
660
9%
1815
8%
660
64%
660
19%
1350
September16th to endNight
55%
657
12%
1815
11%
657
56%
657
17%
1400
October1st to 15thNight
61%
660
24%
1902
23%
660
63%
660
28%
1237
October16th to endNight
59%
704
26%
2112
24%
704
65%
704
29%
1303
November1st to 15thNight
53%
700
24%
2101
20%
700
60%
700
30%
1285
November16th to endNight
48%
720
25%
2250
18%
720
59%
720
29%
1365
December1st to 15thNight
46%
720
24%
2340
19%
720
53%
720
25%
1465
December16th to endNight
50%
768
23%
2496
19%
768
56%
768
23%
1561

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%5%25%6%35%5%6%9%39%
47424
Night
9%425%5%345%6%9%43%
46737
TransparencyDay
38%9%15%18%12%4
47125
Night
36%8%15%19%13%6%
46540
SeeingDay
10%315%25%28%16%
5628
Night
11%5%18%30%28%6%
15797

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
12%7%36%5%3345%6%40%
1611
16th to endDay
11%7%35%5%23447%42%
1728
February1st to 15thDay
13%6%35%5%34345%46%
1735
16th to endDay
10%5%25%425%5%5%6%47%
1643
March1st to 15thDay
8%32322345%8%54%
1980
16th to endDay
8%5%25%5%33348%49%
2111
April1st to 15thDay
7%325%425%448%48%
1972
16th to endDay
6%32443446%8%51%
2154
May1st to 15thDay
8%32342447%8%50%
2322
16th to endDay
8%324446%6%7%10%41%
2431
June1st to 15thDay
9%426%7%5%6%7%8%10%32%
2340
16th to endDay
7%437%7%46%6%8%13%30%
2340
July1st to 15thDay
7%5%26%7%37%7%8%11%32%
2340
16th to endDay
7%5%36%7%49%7%7%9%30%
2465
August1st to 15thDay
6%5%48%8%5%8%7%9%12%24%
2288
16th to endDay
11%6%25%8%47%7%8%10%25%
2034
September1st to 15thDay
7%6%37%7%5%7%7%9%10%27%
1815
16th to endDay
16%8%37%7%5%6%5%6%8%23%
1815
October1st to 15thDay
11%5%36%7%45%5%5%8%36%
1727
16th to endDay
9%5%35%5%3445%6%46%
1760
November1st to 15thDay
8%5%25%5%345%5%8%44%
1757
16th to endDay
10%5%35%5%35%5%46%42%
1708
December1st to 15thDay
10%6%35%5%345%6%8%40%
1620
16th to endDay
9%5%24435%6%5%9%42%
1728
January1st to 15thNight
12%6%35%42435%8%41%
2327
16th to endNight
14%5%35%32445%6%44%
2496
February1st to 15thNight
13%4245%2235%5%50%
2115
16th to endNight
9%5%25%5%34346%48%
1827
March1st to 15thNight
8%32342345%8%52%
1980
16th to endNight
7%324423346%55%
2112
April1st to 15thNight
7%3243245%5%8%52%
1976
16th to endNight
7%3133245%6%10%51%
1806
May1st to 15thNight
5%3133245%6%8%55%
1637
16th to endNight
6%414435%5%7%11%46%
1682
June1st to 15thNight
9%3245%35%6%9%12%35%
1620
16th to endNight
7%426%6%46%5%7%13%36%
1620
July1st to 15thNight
7%5%25%6%46%6%7%12%36%
1620
16th to endNight
5%335%5%47%6%7%11%38%
1703
August1st to 15thNight
5%427%6%35%8%10%12%33%
1586
16th to endNight
9%5%26%7%46%6%7%12%29%
1799
September1st to 15thNight
9%6%37%6%46%7%7%11%28%
1815
16th to endNight
15%7%37%7%46%6%8%10%22%
1815
October1st to 15thNight
12%6%2443446%8%42%
1902
16th to endNight
9%425%6%335%6%8%45%
2112
November1st to 15thNight
8%425%5%35%5%5%7%45%
2101
16th to endNight
8%425%5%35%45%7%46%
2250
December1st to 15thNight
12%6%26%43335%6%44%
2340
16th to endNight
9%5%36%6%3445%8%42%
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
43%5%10%16%17%7%
1612
16th to endDay
41%49%17%18%9%
1728
February1st to 15thDay
40%46%14%19%13%
1737
16th to endDay
34%7%13%15%19%10%
1643
March1st to 15thDay
27%5%14%24%20%7%
1980
16th to endDay
33%6%12%20%19%7%
2112
April1st to 15thDay
30%7%12%21%21%6%
1972
16th to endDay
28%6%13%24%21%6%
2154
May1st to 15thDay
30%7%13%23%19%6%
2322
16th to endDay
33%10%18%21%13%3
2435
June1st to 15thDay
40%14%19%19%5%
2340
16th to endDay
40%14%23%15%5%
2340
July1st to 15thDay
38%16%26%16%2
2201
16th to endDay
42%14%24%16%2
2310
August1st to 15thDay
45%17%24%11%1
2275
16th to endDay
48%15%19%14%1
2034
September1st to 15thDay
44%16%19%14%5%
1815
16th to endDay
55%11%14%11%5%1
1815
October1st to 15thDay
42%7%11%15%15%7%
1727
16th to endDay
36%5%8%17%21%10%
1760
November1st to 15thDay
36%5%11%19%18%7%
1757
16th to endDay
40%5%9%15%18%9%
1708
December1st to 15thDay
39%7%12%21%13%4
1620
16th to endDay
37%6%14%22%11%7%
1728
January1st to 15thNight
40%5%9%21%15%6%
2327
16th to endNight
39%5%9%15%20%9%
2496
February1st to 15thNight
35%5%9%16%18%14%
2124
16th to endNight
36%6%11%17%18%9%
1827
March1st to 15thNight
29%5%14%25%17%8%
1980
16th to endNight
28%6%13%21%19%10%
2112
April1st to 15thNight
29%7%12%22%19%9%
1976
16th to endNight
27%7%14%24%19%5%
1806
May1st to 15thNight
25%7%16%23%19%6%
1638
16th to endNight
30%9%18%25%13%2
1684
June1st to 15thNight
36%10%23%23%5%
1620
16th to endNight
38%14%22%18%5%
1620
July1st to 15thNight
38%15%26%18%2
1530
16th to endNight
34%16%27%18%1
1595
August1st to 15thNight
34%18%29%14%2
1575
16th to endNight
44%13%22%18%1
1799
September1st to 15thNight
46%13%19%13%5%
1815
16th to endNight
51%12%13%13%6%1
1815
October1st to 15thNight
38%8%10%16%18%7%
1902
16th to endNight
35%7%9%16%19%11%
2112
November1st to 15thNight
35%6%12%19%18%7%
2101
16th to endNight
35%6%11%17%16%11%
2250
December1st to 15thNight
39%5%12%23%13%5%
2340
16th to endNight
39%6%13%21%11%8%
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
24%10%28%22%10%4
90
16th to endDay
16%12%34%25%10%1
96
February1st to 15thDay
10%23%26%24%14%1
90
16th to endDay
10%7%43%31%6%1
144
March1st to 15thDay
8%9%30%32%16%2
270
16th to endDay
11%327%28%25%3
288
April1st to 15thDay
11%6%26%30%17%6%
270
16th to endDay
7%320%32%24%11%
270
May1st to 15thDay
7%420%31%22%13%
288
16th to endDay
7%8%26%37%19%
331
June1st to 15thDay
11%8%23%30%25%
315
16th to endDay
6%1221%38%28%
315
July1st to 15thDay
5%212%42%36%
305
16th to endDay
8%314%42%30%
326
August1st to 15thDay
7%8%18%38%26%
297
16th to endDay
13%5%13%35%31%
268
September1st to 15thDay
12%1415%37%28%
255
16th to endDay
21%1419%33%20%
254
October1st to 15thDay
13%114%32%30%7%
255
16th to endDay
9%317%37%24%7%
272
November1st to 15thDay
11%424%32%20%6%
265
16th to endDay
10%7%32%28%17%5%
178
December1st to 15thDay
11%12%25%43%6%1
90
16th to endDay
9%5%20%46%13%4
96
January1st to 15thNight
17%10%28%27%13%1
720
16th to endNight
15%11%28%32%11%
768
February1st to 15thNight
14%7%33%32%10%1
704
16th to endNight
11%10%32%36%8%
631
March1st to 15thNight
9%7%30%40%12%
720
16th to endNight
8%6%26%36%20%2
768
April1st to 15thNight
9%426%38%19%1
718
16th to endNight
10%320%39%23%1
720
May1st to 15thNight
5%219%38%30%3
558
16th to endNight
7%17%31%41%10%
563
June1st to 15thNight
11%17%26%41%11%
540
16th to endNight
8%321%47%17%
540
July1st to 15thNight
9%1318%45%22%
510
16th to endNight
6%320%51%18%
564
August1st to 15thNight
6%418%52%17%
527
16th to endNight
12%6%19%42%18%
657
September1st to 15thNight
11%16%20%45%14%
660
16th to endNight
19%17%21%37%12%
657
October1st to 15thNight
14%113%32%33%5%
660
16th to endNight
11%5%13%35%29%4
704
November1st to 15thNight
9%5%24%33%24%2
700
16th to endNight
10%6%28%32%19%3
720
December1st to 15thNight
13%9%24%28%21%1
720
16th to endNight
13%9%19%35%20%1
768
Page generated at 2017-08-13 14:16:32. Version ac04

Copyright 2017 A. Danko


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