Fun with Stats

2011-10-05 22:45:58.000 – Mike Carmon,  Weather Observer/Meteorologist

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The all-time record low for the month of October on the summit is a chilly -5F.

The all-time record high for the month of October on the summit is a balmy 62F.

That’s a spread of 67 degrees F for the month. Does that sound extreme to you?

The following may surprise you (perhaps not, if you are aware in any way about the abruption with which weather shifts course on Mt. Washington): this spread, when compared with the other 12 months of the year, is actually quite average. In fact, it is the 5th narrowest monthly record temperature spread out of all 12 months. The complete list follows, with the record monthly highs first, record monthly lows second, and the spread between in parentheses:

1. Jan: 47F, -47F; (94F)
2. Dec: 47F, -46F; (93F)
3. Mar: 54F, -38F; (92F)
4. Feb: 43F, -46F; (89F)
5. Apr: 60F, -20F; (80F)
6. Nov: 52F, -20F; (72F)
7. May: 66F, -2F; (68F)
8. Oct: 62F, -5F; (67F)
9. Jun: 72F, 8F; (64F)
10. Sep: 69F, 9F; (60F)
11. Aug: 72F, 20F; (52F)
12. Jul: 71F, 24F; (47F)

How does this list compare to the spread between normal daily maximum and minimum temperatures for each month? Again, normal daily maximum high temperatures are first, normal daily minimum temperatures are second, and the spread in parentheses. Let’s check it out:

1. Jan: 14.0F, -3.7F;(17.7F)
2. Dec: 18.5F, 1.7F;(16.8F)
3. Feb: 14.8F, -1.7F;(16.5F)
4. Mar: 21.3F, 5.9F;(15.4F)
5. Nov: 27.6F, 13.6F;(14.0F)
6. Apr: 29.4F, 16.4F;(13.0F)
7. Oct: 36.4F, 24.0F;(12.4F)
8. May: 41.6F, 29.5F;(12.1F)
9. Jun: 50.3F, 38.5F;(11.8F)
10. Sep: 46.1F, 34.6F;(11.5F)
11. Aug: 53.0F, 42.1F;(10.9F)
12. Jul: 54.1F, 43.3F;(10.8F)

You’ll notice that the list is generally the same, although the middle bunch of months do some swapping around. The reason for this lies in the difference among the statistics that are being compared. Daily records can be thought of as instantaneous figures, and all it takes is one anomalous event to produce an outlier of a statistic and skew the data for a month.

Averages, on the other hand, weed out the outliers and produce data that is a bit more reasonable to compare and contrast. You’ll notice the list comparing averages follows the expected seasonal pattern more closely: winter months are more extreme, while the summer months are more temperate, and the transition months of May (spring) and October (fall) near the middle.

 

Mike Carmon,  Weather Observer/Meteorologist