Warm Days, Chilly Nights Go Hand in Hand in Late Summer

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Fairbankskans and others in the Alaskan Interior have been enjoying plenty of sun and warm afternoons for the past week. The NWS office there even put out a statement about it, as if to rub it in to the rest of us who have been layering on the sweaters, if not rain coats, lately.

PUBLIC INFORMATION STATEMENT…CORRECTED
NATIONAL WEATHER SERVICE FAIRBANKS AK
316 AM AKDT TUE AUG 30 2011

CORRECTED THE HIGH TEMPERATURE AT FAIRBANKS

…THE UNSEASONABLY WARM WEATHER CONTINUES IN THE INTERIOR…

A RIDGE OF HIGH PRESSURE ALOFT HAS BEEN RESPONSIBLE FOR THE
WARM WEATHER DURING THE LAST SEVERAL DAYS ACROSS MUCH OF THE
INTERIOR. MONDAY WAS THE WARMEST DAY OF THE BUNCH IN MANY AREAS.
HERE ARE SOME HIGH TEMPERATURES THAT WERE OBSERVED MONDAY AFTERNOON:

DENALI NP HEADQUARTERS….74
FAIRBANKS INTERNATIONAL…72
NORTHWAY………………71
FORT WAINWRIGHT………..70
NENANA………………..70
TANANA………………..69
EIELSON AFB……………69
EAGLE…………………69
DELTA JUNCTION…………68
FORT YUKON…………….68

Only the southern end of the SE Panhandle could get near the interior’s highs today. Nothing record breaking, but very nice nonetheless. What is not mentioned in the statement is the low temperatures, which are getting downright chilly. This is no surprise, as the same weather pattern which allows the solar heating to warm the afternoons also allows the radiational cooling to cool the nights and early mornings. I covered this topic more thoroughly in this post. So it is also no surprise that the state’s high for today and low for last night are only a stone’s throw apart (Alaskan speaking) at Northway (68 F/20 C) and Eagle (31 F/-1 C). Eagle was 70 F/21 C yesterday.

Now take a look at the Fairbanks Airport temperature trace for August (shy a few hours):
(click for larger version)

graph

The small magenta spikes near the bottom of the chart show precipitation (rain) which is a good indicator of the kind of heavy cloud cover which moderates the temperatures, keeping the diurnal range low. Most of the middle of the month was in this mode, with a few days of relief interspersed. The first five days and the last week were dry and more clear, allowing the large swings in temperature. This is nothing new to many, and as I mentioned, nothing new to this blog (here’s the other article).

What you might not have thought about, however, is how the daily average temperature records can mask the differences between these two regimes. I’m talking about the human experience…how nice it is or was for outdoor activities. To get this story from the weather records, the  daily average temperature downplays what you and I experience as the day’s weather. The recent interior warmth is a good example. During the past week it was so nice that the NWS folks made official acknowledgement. Sunny, warm, pleasant weather with the highs about 6-9 degrees F warmer than the climatological average. However, since the lows dropped lower with the clear weather (they were fairly close to the climatological average or “normal” in NWS lingo), the daily average [(high+low)/2)] was only 3-6 degrees warmer than usual. So when considering how the weather affects daily life, looking at high temperatures makes more sense to me than the day’s average temperature so commonly given in climatological reports. However, in the midst of the winter, I think low temperatures are the more important factor for the human experience. I’ll save that explanation for another post. What do you think…of which measure to use and whether those Fairbankskans deserve this good weather?

One thought on “Warm Days, Chilly Nights Go Hand in Hand in Late Summer

  1. “The Human Experience.” Yup, you pegged it. The average seems great for reading overall trends, but keying on highs in the summer, and lows in the winter is what we, as humans, do. When to fire up the bar-b-que, or overstock woodbox for a bitter cold night. Preparation.
    As for whether the Fairbankskans deserved that chunk of good weather?..well, I guess they’re on borrowed time and preparing for several months of staring at the “low” end of the temperature spectrum, so sure, let ’em bask in the glory

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