Our summer has turned somewhat cool lately. Following a relatively warm July, August has brought little in the way of heat. However, the temperatures have been nowhere near as cold as they were in August of 2004. Aug. 9 of that year was one of those rare summer days in which the high temperature (of only 61 degrees) of the day actually occurred at midnight. For most of the day, it was in the 50s. The following day, the high temperature was 59. Morning temperatures were in the 40s five consecutive days.
Evapotranspiration is the water evaporated from the ground back to the atmosphere, both as transpiration from the leaves of plants and also as direct evaporation from open water and soil. The amount of water evaporated changes from day to day based on cloud cover, wind, relative humidity, temperature and other influences. On a sunny day this time of year, an average of approximately one-third of an inch of moisture is evaporated in a day. On a cloudy day, that amount may be a tenth of an inch or less while on a hot, sunny day it could be more than half an inch.
The dry conditions this summer are likely to get worse rather than better. There have been fewer storms this year. It rains here and there, but general rainfall has been rare. Many people have remarked that "the storms always go around us," and some have asked why this is. Actually, it isn't. At least, there is nothing peculiar about any location that is causing storms to go elsewhere. Storms have a natural tendency to change direction and to change intensity. They can even merge and split.
The shrinking of the summertime Arctic icecap in recent decades has left me wondering when the last time the Arctic was ice-free. It turns out this is a hard question to answer due to the fact that Arctic sea ice undergoes a little melting every summer from top (weather) and bottom (unfrozen ocean), which leaves a poor record. The most accepted theory is that the North Pole has been capped in ice continuously or nearly continuously for 2.7 million years since the beginning of the present Wisconsonian ice age.
Apart from the wind damage, Tuesday's rain was nice. However, this rain was not an end-all rain by any means. The 1-2 inches most areas got will green the grass a bit and stave off major concern about a summer drought. But unless it rains substantially again in the next week or two, our region will be wanting for rain again. Since the rainy period began in 1993, most of us have become accustomed to heavy rainfall during May, June and July. It rains an inch or two and then, a couple of days later, another inch or two.
There is probably no weather element so poorly understood as humidity. Actually, we understand humidity when we feel sticky. But most people do not understand how humidity is quantified. Humidity is actually "relative humidity," which means it is relative to temperature. What we quantify as "humidity" is not actually the percentage of water vapor in the atmosphere (absolute humidity) because that number is always so ridiculously low (.01%) so as to be useless to the general public.
Have you ever noticed that thunderstorms often appear to weaken or change direction just before hitting your area? This illusion is common everywhere, but in most cases, it is just an illusion. One reason for this is parallax. This is the illusion that something is coming straight for you when it is actually moving almost, but not quite, straight toward you. It appears to change direction to one side or another as it passes by when, in reality, it was never headed right at you to begin with.
There is a jet stream pattern setting up that may have lasting impacts on our weather. The polar jet stream is in the process of forming into a high-amplitude, very wavy pattern around the world. These patterns are most likely in spring and usually result in stagnant weather. It appears there will be about six main lobes in which the jet stream will go rather far south, delivering cold and wet weather to these areas. In between, there will be six areas in which the jet will go far to the north, allowing for sunny, warm conditions.
The temperature sensor at the official gauge for Fargo-Moorhead at Hector International Airport malfunctioned late last week, indicating a temperature of 50 degrees late Thursday night. The temperature was actually 35 degrees at the time. Temperatures in the 50s in Fargo-Moorhead during January are rare, obviously, but not entirely unknown. Ten of the 31 days in January sport a record high temperature in the 50s, so it does happen occasionally. The years 2012, 2002, 1981, 1942, 1931, 1908 and 1900 all have at least one daily record in the 50s.
Whenever we get a spell of snow-melting weather in January, a few people always ask if this is "The January Thaw." There is no such thing as "The January Thaw." There are, however, usually at least a couple of days of thawing temperatures at some point in any winter month in our region. This is due to the natural up-and-down, highly variable nature of our climate, particularly in winter.