tag:blogger.com,1999:blog-4572286363399496963.post2387025695216920653..comments2019-08-22T01:52:16.612-08:00Comments on Deep Cold: Alaska Weather & Climate: Temperature PercentilesRickhttp://www.blogger.com/profile/03946704894714514716noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-4572286363399496963.post-59981058873615275112015-04-23T09:53:31.862-08:002015-04-23T09:53:31.862-08:00Eric, Good question but I handled the counts to pr...Eric, Good question but I handled the counts to produce the true daily percentiles, so just read off the probability for any given day. The 1st percentile reflects a 1 percent chance of being exceeded (below) on that day. Conversely, the 99th percentile is exceeded 1 percent of the time on any given day.<br /><br />For example, -40 was reached 8 times on Jan 12th, 6 times on the 13th, 4 times on the 14th, and twice on the 15th. If we proceed like this for every day and then take averages over a 21-day window, we get an average of (e.g.) 4.48 times for Jan 5-25, or 11.8 percent of 38 years. Thus -40 is reached 11.8 percent of the time or once every 8.5 years on average.<br /><br />It would be easy to produce an equivalent return-period chart, but it would only be a return period for that day of the year; the true return period is always much less because we have all the other days to consider too. So I think that would be too confusing.<br />Richard Jameshttps://www.blogger.com/profile/08313902028896263276noreply@blogger.comtag:blogger.com,1999:blog-4572286363399496963.post-48382731512204230722015-04-23T08:50:47.421-08:002015-04-23T08:50:47.421-08:00How does the sliding date window effect how to rea...How does the sliding date window effect how to read the percentiles? For instance, in January there is a 10% chance of being colder than -40. Would that be 10% of 38 years (about once every 4 years)? Or would that be 10% of 38*21 (about once every 80 years)? The stats here aren't do clear. And experience would say once every four years or so.Eric Lundellhttps://www.blogger.com/profile/17914784378747801359noreply@blogger.com