- Sep 22, 2020

AND THEN IT WAS FALL

We all were taught at a tender age that the Earth makes a complete revolution around the sun once every 365 days, following an orbit that is elliptical in shape. This means that the distance between the Earth and Sun, which is 93 million miles on average, varies throughout the year. During the first week in January, the Earth is about 1.6 million miles closer to the sun. This is referred to as the perihelion. The aphelion, or the point at which the Earth is about 1.6 million miles farther away from the sun, occurs during the first week in July. So why is it hottest when the sun is the farthest way it gets from our planet? Simply put, it's all a matter of tilt. Our seasons are caused by the fact that the Earth is tilted on its axis by 23.5°. The tilt's orientation with respect to space does not change during the year; thus, the Northern Hemisphere is tilted toward the sun in June and away from the sun in December. It adds up to shorter days and less direct energy in the winter, allowing the colder temperatures that go along with those important changes.

There are only two times of the year when the Earth's axis is tilted neither toward nor away from the sun, resulting in a "nearly" equal amount of daylight and darkness at all latitudes. These events are referred to as Equinoxes. The word equinox is derived from two Latin words - aequus (equal) and nox (night). At the equator, the sun is directly overhead at noon on these two equinoxes. Today in the northern hemisphere we experience the autumnal equinox signaling that at 8:31 am Tuesday, fall officially begins.

So, another summer is in the books and we now begin the journey that leads us to winter. Fall 2020 starts off in a spectacular way today with near perfect weather conditions. Highs will reach the upper 70s to near 80 accompanied by light winds and sunny skies. The only negative will be some haze due once again to the relentless fires out west.

This is part of a fine stretch of weather that makes today the 10th consecutive day with no rain over much of the central Midwest. You can see the reversal coming after many of us had heavy rain for 7 straight days September 6-12th. Below you can see the daily precipitation report for the Quad Cities for the last 18 days.

This splendid pattern will be with us the rest of the week and perhaps the first part of next week before a significant change to cooler weather is anticipated. Here's the 7 day temperature departure showing mild air prevailing out to September 28th.

Days 8-15 are a far different story if trends hold as a strong trough delivers a healthy punch of cool air days 8-15 (September 29-October 6th).

A key consideration for rainfall is that the overall flow aloft is northwest limiting moisture. The16 day precipitation departures point heavily at a continuation of the dry pattern we have reverted to the past 10 days. As you can see, many parts of the nation are looking at below normal rainfall the next 2 weeks.

As boring as that looks, something that does excite me is the fact snow is beginning to show up over parts of Canada. I'm all about that, especially since I'm only about 3.5 hours from the border.