Sunday, October 27, 2013

Most and Least Difficult Temperature Records to Break

Several of tomorrow's temperature records in Fairbanks are relatively easy to break. The low minimum record of -17 is only 1.97 standard deviations below the normal low of 6.3 degrees. Only two calendar days have record low temperature that are closer to their respective daily normal temperatures than October 28th. Therefore, the low minimum record for tomorrow is statistically, the third easiest low minimum record to break. Conversely, the record low minimum temperature for May 9th is pretty safe. It is 6.33 standard deviations below the 1981-2010 daily normal of 35.1 degrees.

The low maximum record for tomorrow is 4 degrees. That is only 1.61 standard deviations below the daily normal maximum of 21.4 degrees. No other low maximum record is closer to its respective daily normal temperature for any day of the year. Therefore, the October 28th low maximum record is the least difficult daily low maximum record to break during the course of the year. For reference, the coldest October 27 maximum is -1 and the coldest October 29 maximum is -6. Those records are more difficult to break.

The chart (graphic) below shows the most difficult daily records to break (left side) and least difficult daily records to break (right side) over the course of the year. There is a noticeable, and interesting, seasonality to the chart.

Four types of records are shown.

1) High maximum (a.k.a. record high)  --> shown in pink
2) Low maximum (a.k.a record coldest high temperature)  --> shown in yellow
3) Low minimum (a.k.a. record low)   --> shown in blue
4) High minimum (a.k.a. record warmest low temperature)   --> shown in green

Note 1: the standard deviations from normal are all based on the 1981-2010 climate normal period. The relative ease or difficulty to break a record should be compared to the current climate regime.

Note 2: The May 9 (1964) record was 5.32 SD below the mean for the 1931-1960 climate normal period.

1 comment:

  1. Brian, the seasonality of the dates is indeed interesting. Some of it can be explained by the long-term trend, e.g. Fairbanks has gotten cooler in October so the records for cold are likely to be closer to the recent mean and therefore easier to break (e.g. least difficult low max and min). Conversely the long-term trend is strongly up in spring, so warm records will be easier to break (least difficult high max and min) and cold records more difficult (most difficult low max and min).