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 2018-02-14.

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%
16528
20%
48769
15%
16490
61%
16490
28%
31166

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
37%
777
20%
2522
12%
776
48%
776
22%
1592
January16th to endNight
40%
832
23%
2704
16%
832
50%
832
25%
1661
February1st to 15thNight
39%
757
21%
2288
13%
756
48%
756
27%
1417
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
73%
539
9%
1609
9%
536
73%
536
23%
1121
August16th to endNight
65%
717
11%
1964
11%
717
65%
717
22%
1436
September1st to 15thNight
62%
720
9%
1980
8%
720
63%
720
18%
1481
September16th to endNight
58%
717
14%
1980
14%
717
59%
717
18%
1495
October1st to 15thNight
60%
720
23%
2075
23%
720
63%
720
27%
1357
October16th to endNight
58%
768
27%
2304
24%
768
65%
768
29%
1414
November1st to 15thNight
55%
760
23%
2281
19%
760
61%
760
31%
1382
November16th to endNight
49%
780
26%
2438
19%
780
60%
780
29%
1473
December1st to 15thNight
46%
780
24%
2535
19%
780
55%
780
26%
1566
December16th to endNight
50%
832
23%
2704
20%
832
57%
832
24%
1673

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%5%35%5%6%9%39%
49291
Night
9%425%5%345%6%8%43%
48974
TransparencyDay
38%9%15%18%12%4
48992
Night
36%8%15%19%13%6%
48777
SeeingDay
11%316%26%27%15%
6290
Night
11%418%30%28%6%
16537

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%7%36%5%33446%40%
1746
16th to endDay
11%7%35%5%23447%43%
1872
February1st to 15thDay
13%6%35%5%34345%45%
1867
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%8%12%25%
2340
16th to endDay
11%6%25%8%47%7%8%10%26%
2220
September1st to 15thDay
9%6%37%7%5%7%6%9%10%27%
1980
16th to endDay
15%8%37%7%5%6%5%6%8%25%
1980
October1st to 15thDay
11%6%36%7%45%5%5%8%35%
1884
16th to endDay
10%5%25%5%3445%6%46%
1920
November1st to 15thDay
8%5%25%5%345%5%8%44%
1907
16th to endDay
10%5%35%5%35%5%46%44%
1850
December1st to 15thDay
10%6%35%4345%6%8%41%
1755
16th to endDay
9%5%244346%5%9%43%
1872
January1st to 15thNight
13%6%35%42446%8%41%
2522
16th to endNight
14%5%35%324446%45%
2704
February1st to 15thNight
13%4245%2335%5%49%
2284
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%
1620
16th to endNight
9%5%26%7%45%6%7%11%30%
1964
September1st to 15thNight
10%6%37%6%46%7%7%10%28%
1980
16th to endNight
14%6%36%6%46%6%8%10%25%
1980
October1st to 15thNight
12%6%2443446%8%41%
2075
16th to endNight
9%425%6%3446%8%45%
2304
November1st to 15thNight
8%425%5%35%45%7%46%
2281
16th to endNight
8%425%5%25%45%7%47%
2438
December1st to 15thNight
12%5%25%43335%6%45%
2535
16th to endNight
10%5%25%5%3445%7%43%
2704

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
44%5%9%15%17%7%
1747
16th to endDay
41%48%17%18%9%
1872
February1st to 15thDay
41%5%7%13%19%12%
1869
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
44%17%24%11%1
2327
16th to endDay
47%16%20%14%1
2220
September1st to 15thDay
45%16%18%13%5%
1980
16th to endDay
52%11%14%13%6%1
1980
October1st to 15thDay
43%7%11%15%14%6%
1884
16th to endDay
35%5%8%17%21%11%
1920
November1st to 15thDay
36%6%12%19%18%7%
1907
16th to endDay
40%5%9%16%20%8%
1850
December1st to 15thDay
39%7%12%20%13%5%
1755
16th to endDay
36%6%14%24%11%6%
1872
January1st to 15thNight
41%5%9%21%16%6%
2522
16th to endNight
39%49%15%20%10%
2704
February1st to 15thNight
36%6%9%15%18%13%
2293
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
1609
16th to endNight
43%13%23%17%1
1964
September1st to 15thNight
47%13%18%14%5%
1980
16th to endNight
48%12%14%15%7%1
1980
October1st to 15thNight
38%8%10%17%17%7%
2075
16th to endNight
35%6%9%16%20%11%
2304
November1st to 15thNight
34%6%12%21%18%6%
2281
16th to endNight
35%6%11%18%18%10%
2438
December1st to 15thNight
38%5%13%22%13%6%
2535
16th to endNight
38%6%13%22%11%7%
2704

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
25%11%35%17%6%2
135
16th to endDay
15%11%37%26%8%
144
February1st to 15thDay
12%16%32%26%12%
130
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%39%26%
313
16th to endDay
13%6%12%34%32%
332
September1st to 15thDay
15%1418%35%24%
315
16th to endDay
19%422%33%19%
314
October1st to 15thDay
14%116%29%30%7%
315
16th to endDay
11%418%37%21%6%
336
November1st to 15thDay
10%322%35%21%6%
325
16th to endDay
10%6%27%32%18%4
230
December1st to 15thDay
10%12%25%40%10%1
135
16th to endDay
10%322%49%11%2
144
January1st to 15thNight
18%10%28%27%12%1
780
16th to endNight
15%11%28%32%11%
832
February1st to 15thNight
14%7%33%32%10%1
760
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%53%17%
539
16th to endNight
11%6%19%42%19%
717
September1st to 15thNight
13%17%20%44%13%
720
16th to endNight
17%17%21%39%11%
717
October1st to 15thNight
15%113%30%33%5%
720
16th to endNight
11%5%15%34%28%4
768
November1st to 15thNight
8%5%23%33%25%3
760
16th to endNight
10%5%27%32%19%3
780
December1st to 15thNight
13%9%24%28%22%1
780
16th to endNight
13%9%19%35%21%1
832
Page generated at 2018-02-15 10:58:40. Version ac04

Copyright 2018 A. Danko


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