Porterville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Porterville clear sky chart from 2005-11-05 to 2017-12-02.

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
78%
15840
31%
47787
30%
15805
79%
15805
50%
23612

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
69%
717
22%
2488
25%
716
70%
716
32%
1375
January16th to endNight
67%
768
26%
2496
29%
768
68%
768
32%
1440
February1st to 15thNight
68%
699
27%
2115
28%
699
70%
699
36%
1223
February16th to endNight
65%
632
24%
1895
27%
632
67%
632
35%
1116
March1st to 15thNight
72%
720
20%
2154
24%
720
72%
720
41%
1168
March16th to endNight
72%
768
25%
1992
22%
768
74%
768
47%
1129
April1st to 15thNight
67%
719
28%
1799
18%
719
69%
719
46%
1056
April16th to endNight
71%
720
29%
1800
15%
720
74%
720
56%
961
May1st to 15thNight
79%
617
32%
1697
23%
617
80%
617
64%
795
May16th to endNight
69%
498
31%
1622
26%
498
74%
498
52%
729
June1st to 15thNight
79%
360
35%
1440
40%
360
84%
360
61%
498
June16th to endNight
94%
360
41%
1440
51%
360
95%
360
86%
402
July1st to 15thNight
95%
340
36%
1360
45%
340
95%
340
73%
429
July16th to endNight
92%
481
41%
1513
40%
451
93%
451
70%
573
August1st to 15thNight
93%
717
38%
1790
25%
713
93%
713
84%
782
August16th to endNight
95%
764
46%
1910
31%
764
96%
764
86%
839
September1st to 15thNight
95%
720
44%
1800
34%
720
95%
720
80%
811
September16th to endNight
93%
716
47%
1974
46%
716
94%
716
80%
818
October1st to 15thNight
85%
720
34%
2067
35%
720
86%
720
59%
978
October16th to endNight
83%
768
42%
2322
47%
768
85%
768
58%
1070
November1st to 15thNight
80%
760
30%
2470
35%
760
81%
760
49%
1183
November16th to endNight
74%
780
28%
2535
31%
780
75%
780
41%
1295
December1st to 15thNight
71%
728
25%
2420
28%
728
73%
728
35%
1338
December16th to endNight
63%
768
23%
2688
26%
768
65%
768
27%
1604

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
5%312212235%67%
48665
Night
7%312212235%66%
47969
TransparencyDay
20%28%20%27%20%
48347
Night
21%29%22%26%16%
47788
SeeingDay
7%316%36%28%8%
6140
Night
8%15%35%39%8%
15851

By Month

Percentage Cloud Cover SW (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%6%2442345%9%45%
1447
16th to endDay
13%7%24424446%46%
1728
February1st to 15thDay
14%7%23313346%48%
1746
16th to endDay
14%6%25%32335%6%46%
1579
March1st to 15thDay
9%6%1331346%9%48%
1803
16th to endDay
9%323413446%53%
2232
April1st to 15thDay
9%423323345%57%
2149
16th to endDay
7%212313347%63%
2160
May1st to 15thDay
2111212236%74%
2252
16th to endDay
422112346%70%
2489
June1st to 15thDay
21111123478%
2520
16th to endDay
112288%
2520
July1st to 15thDay
11123481%
2520
16th to endDay
11121222479%
2546
August1st to 15thDay
1112387%
2160
16th to endDay
11112386%
2292
September1st to 15thDay
111122285%
2160
16th to endDay
11122385%
1986
October1st to 15thDay
422212335%71%
1890
16th to endDay
4213213335%68%
1902
November1st to 15thDay
5%424223346%61%
1719
16th to endDay
9%5%24323346%54%
1755
December1st to 15thDay
11%5%23323448%49%
1574
16th to endDay
14%7%35%41335%7%43%
1536
January1st to 15thNight
12%5%24312346%52%
2488
16th to endNight
12%5%24413336%51%
2496
February1st to 15thNight
12%424323347%51%
2104
16th to endNight
18%422312336%51%
1895
March1st to 15thNight
7%323323447%56%
2154
16th to endNight
10%31221335%8%57%
1992
April1st to 15thNight
10%413213246%59%
1799
16th to endNight
7%21131222469%
1800
May1st to 15thNight
411111236%73%
1697
16th to endNight
5%21212235%70%
1621
June1st to 15thNight
32121125%78%
1440
16th to endNight
12291%
1440
July1st to 15thNight
11123482%
1440
16th to endNight
1111111482%
1617
August1st to 15thNight
111289%
1800
16th to endNight
1112287%
1910
September1st to 15thNight
111122385%
1800
16th to endNight
111122484%
1974
October1st to 15thNight
412212235%72%
2067
16th to endNight
3213211235%71%
2322
November1st to 15thNight
6%212212336%65%
2470
16th to endNight
8%413313337%58%
2535
December1st to 15thNight
10%5%14223346%53%
2420
16th to endNight
15%6%24314346%47%
2688

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
35%210%23%20%6%
1447
16th to endDay
40%49%18%17%9%
1728
February1st to 15thDay
36%312%23%17%6%
1746
16th to endDay
40%212%30%12%1
1579
March1st to 15thDay
31%416%24%18%4
1803
16th to endDay
30%415%26%19%3
2232
April1st to 15thDay
29%211%30%20%5%
2149
16th to endDay
21%214%27%26%7%
2160
May1st to 15thDay
13%110%27%35%10%
2252
16th to endDay
15%28%31%33%8%
2492
June1st to 15thDay
11%18%21%31%25%
2520
16th to endDay
5%127%35%47%
2520
July1st to 15thDay
8%1210%24%52%
2371
16th to endDay
11%1312%28%43%
2388
August1st to 15thDay
6%28%34%47%
2146
16th to endDay
6%18%42%39%
2292
September1st to 15thDay
7%1313%34%40%
2160
16th to endDay
7%1119%45%24%
1986
October1st to 15thDay
16%16%23%28%22%
1890
16th to endDay
19%27%24%26%20%
1902
November1st to 15thDay
25%111%24%29%6%
1719
16th to endDay
31%39%23%23%9%
1755
December1st to 15thDay
34%312%21%22%6%
1574
16th to endDay
41%413%22%13%4
1536
January1st to 15thNight
34%310%24%21%5%
2488
16th to endNight
35%312%19%18%11%
2496
February1st to 15thNight
33%212%26%19%5%
2115
16th to endNight
34%314%29%15%2
1895
March1st to 15thNight
28%316%26%20%4
2154
16th to endNight
26%318%31%17%3
1992
April1st to 15thNight
28%212%32%17%6%
1799
16th to endNight
20%215%28%27%6%
1800
May1st to 15thNight
14%18%26%37%11%
1698
16th to endNight
18%26%23%39%10%
1622
June1st to 15thNight
12%6%22%32%25%
1440
16th to endNight
328%36%48%
1440
July1st to 15thNight
7%1311%22%54%
1360
16th to endNight
10%412%24%47%
1513
August1st to 15thNight
5%211%33%45%
1790
16th to endNight
5%11%45%35%
1910
September1st to 15thNight
7%1314%34%39%
1800
16th to endNight
6%1222%43%23%
1974
October1st to 15thNight
17%26%23%30%20%
2067
16th to endNight
17%16%27%28%19%
2322
November1st to 15thNight
22%113%26%27%9%
2470
16th to endNight
27%211%22%27%8%
2535
December1st to 15thNight
32%312%25%21%5%
2420
16th to endNight
38%412%22%17%3
2688

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
34%441%10%9%
75
16th to endDay
17%310%35%24%7%
256
February1st to 15thDay
18%313%34%20%10%
265
16th to endDay
17%418%35%20%4
238
March1st to 15thDay
11%6%17%31%24%8%
270
16th to endDay
9%6%26%32%19%4
288
April1st to 15thDay
14%10%24%29%17%3
269
16th to endDay
5%12%31%29%16%4
270
May1st to 15thDay
6%426%31%23%6%
288
16th to endDay
6%425%31%25%6%
330
June1st to 15thDay
1320%37%29%6%
315
16th to endDay
1112%34%36%13%
315
July1st to 15thDay
18%33%41%13%
305
16th to endDay
1335%44%13%
327
August1st to 15thDay
112%48%27%9%
315
16th to endDay
6%43%35%12%
332
September1st to 15thDay
39%47%28%10%
315
16th to endDay
1216%42%31%5%
315
October1st to 15thDay
3324%37%26%4
315
16th to endDay
5%410%35%34%9%
318
November1st to 15thDay
7%11%26%31%23%
135
16th to endDay
15%9%27%34%13%
135
December1st to 15thDay
21%28%44%23%
85
16th to endDay
23%1432%26%10%
64
January1st to 15thNight
14%2435%32%10%
720
16th to endNight
16%1438%31%7%
768
February1st to 15thNight
14%3439%28%9%
704
16th to endNight
20%26%37%27%6%
632
March1st to 15thNight
8%27%43%30%6%
720
16th to endNight
12%27%39%33%4
768
April1st to 15thNight
12%312%39%29%3
719
16th to endNight
8%311%35%34%5%
720
May1st to 15thNight
5%210%41%36%3
618
16th to endNight
7%414%36%34%4
500
June1st to 15thNight
429%43%36%2
360
16th to endNight
344%46%3
360
July1st to 15thNight
123%65%8%
340
16th to endNight
117%66%13%
481
August1st to 15thNight
1228%59%7%
717
16th to endNight
117%64%14%
764
September1st to 15thNight
1125%57%14%
720
16th to endNight
1334%49%11%
716
October1st to 15thNight
41439%39%11%
720
16th to endNight
5%1332%39%17%
768
November1st to 15thNight
7%1436%37%12%
760
16th to endNight
12%1334%36%12%
780
December1st to 15thNight
12%2441%30%8%
728
16th to endNight
18%15%42%26%5%
768
Page generated at 2017-12-03 08:16:36. Version ac04

Copyright 2017 A. Danko


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