On average, there are 24 days during this 66-day window with measurable precipitation. In 2014, there have been 29 days between June 1 and August 5 with measurable precipitation (range: 10 to 53). If you include Trace amounts, the long-term average is 38 days and the 2014 value is 47 (range: 14 to 58). In both instances, 2014 is above the long-term average but quite far from the largest values. However, 2014 does lead in several important categories – days with >= 0.25", >=0.33", >=0.50", and >=1.00".
Figure 1. Number of days with A) any precipitation, B) measurable precipitation, C) over 0.10" precipitation, and D) over 0.50" precipitation for all years during the June 1 to Aug 5 time period.
This leads to the conclusion that when it rains, it pours. Figure 2 shows the June 1 to August 5 total precipitation (green line) and the per rainfall event amount (purple line). As you can see, 2014 has reported approximately 0.37" of rain per day with measurable rainfall. Only one other year (1962) even comes close to this year's per rainy day average. That year had 10 fewer days with measurable precipitation through August 5.
Nine times since June 1st the Fairbanks daily precipitation has exceeded the 95th percentile for the date. In theory, during any 66-day period, the 95th percentile should be exceeded 3.3 times. Figure 3 shows the Fairbanks precipitation exceedance probabilities with 2014 precipitation events overlaid.
Figure 3. Daily precipitation exceedance probabilities with 2014 precipitation events overlaid. Note: The probability lines only take into account days with 0.01" or greater.
It's interesting that the rainy season is not Tanana fair time but mid-July. Then why does it always seem to rain during the first week of August?ReplyDelete
Another research idea that would be interesting is to see whether easterly or westerly rains produce more rain. Maybe you could look at 500mb and 800mb wind directions. The '67 flood had westerly storms (I believe) but this summer has been a mixture.
This is an interesting analysis. Thanks Brian.ReplyDelete
I was at the FAI/PAFA float pond today with the dog and the pond water (and water table) is high enough to flow water up the drainage channels that feed the inlet culverts. There are reports in our neighborhood near Noyes Slough (trib of the Chena) of homes with water in their basements from ground water. If that stays there's going to be some frozen plumbing this winter in Fairbanks.