The Weather Wire
September 2006 Volume 14 Number 9
Avg High 87.2
Avg Low 58.4
Snow - 0.0"
Season Snow - 0.0"
Precipitation - 1.13"
Avg High 77.4
Avg Low 47.3
Avg Snow - 2.1"
Avg Precip - 1.14"
The Forest Through the Trees
September is a month of transition from summer into fall which rapidly turns into winter. Snows are possible along the Front Range anytime during the month of September and in October we see at least one or two episodes of winter weather. All this, the change of seasons is due to the tilt out planet has toward the sun. If it werenít for this tilt in the axis of earth of 23 Ĺ degrees we would not have any seasonal changes. Our weather would be constant that is to say instead of 4 seasons, we would have only one.
Now I have written more than a few articles on global warming or should I say the lack of it. And some times we get a bit too close to a subject and have too narrow of a view. Better know as ďcanít see the forest through the treesĒ. So Iím going to take a wider view on seasons and climate.
The planet earth though has been around for billions of years. Mansí stay on this planet is measured in thousands of years. So we have not been here all that long. During these billions of years earth has seen its climate change drastically many, many times. Obviously we were not here to cause these climate changes so there had to be other reasons. During the age of the dinosaurs the climate was for the most part was warm and tropical across much of the planet. Recently by geological standards just 300 to 400 thousand years ago much of North America and Europe were cover in thick sheets of ice. The mountains to our west here in Colorado had large glaciers hundreds of feet think that fill todayís mountain valleys with ice.
So what would be the causes for the huge climate changes, that over earthís lifespan of some 4 billion years has happened not once of twice but hundreds of times?
Lets start narrow and then expand the possibilities and by narrow I mean lets start with local effects. Earth over its history has seen large volcanic periods and the periods of relative quiet. Volcanoes emit huge volumes of CO2 and water vapor when they erupt. Both of these gasses are greenhouse gasses, which means during large eruptive periods our climate should be warmer. I say should, because volcanoes also put enormous amounts of particles in the atmosphere which would cut down on the amount of sunshine we get and thereby make us cooler. See, not as easy as one would think! Same with putting large amounts of water vapor in the air. More water vapor, more clouds, less sunshine, cooler temperatures.
Ok letís widen the view a bit. Over the course of billion of years the each has been hit by meteors, comets and cosmic debris. Some of these have had very little impact on our climate, but the larger meteors and comets have had drastic effects on earthís climate. Some may ask how do you know we have been hit by all these meteors?? All you have to do is look at our moon, with its thousands and thousand of craters. So where are all the craters on earth?? We have them, you just have to look harder! Why?? Because of plate tectonics and weather. The moon has neither. Our continents drift on plates that moves the continents a few inches per year, but over billions of years we are talking thousands of miles. This drifting of the continents erases many of the craters on earth over time. The second major factor is the weather. Rain, snow, wind all change the shape of mountains and craters alike and over millions and billions of years literally remake the surface of the earth every couple of million of years. But there are craters we can see today so we know we have been hit many times. So how would this change our climate. One of the theories out there now for the extinction of the dinosaurs is that a comet or large meteor hit the earth, putting tons of particles into the atmosphere that lingered for thousands of years, cooling the planet to the planet to the point the dinosaurs could not survive. Now lets do that a few thousand times over the 4 billion years and we have more than a few climate changes.
Ok, letís go wider still. During our short stay on this planet our position or orbit around the sun has been fairly constant. Does that mean it has always been that way? Of course not! Over the millions and billions of years the earths orbit has changed, either a bit closer to the sun, or a bit further away. Any of those changes would have a dramatic effect on the climate of this planet. The reason for these orbit changes we would find I the history of the sun. Yes during our short period on this planet the sun has remained fairly constant, but that has not always been so. Any changes in the sunsí mass would change the amount of attraction or gravitational pull on not only the earth, but all the planets in our solar system. A bit less pull, earth would be farther from the sun and cooler, a bit more pull and we would be closer to the sun and warmer. Has this actually happened?? Hard to say, we were not here to witness it, but it certainly possible.
I guess the point Iím trying to make is that the earth has seen climate change throughout its history. It will continue to see climate change while we are here and long after we are gone from this planet.
So I guess Iím just asking that the next time you hear on the news or read in the paper about the impending threat of global warming, that you take a wider view of the situation, we are not only ones that can possibly change earths climate, there are many other bigger factors to consider!
Considerable improvement in drought conditions across Colorado occurred in August.
The map below shows forecasted temperature deviances for September 2006. As can be seen, normal temperatures are expected for f Colorado for September 2006.
The map below shows forecasted precipitation deviances for September 2006. Normal to above normal precipitation is expected for all of Colorado for September 2006.
As can be seen in the below map, with the drought improvement is forecast for all of Colorado through November.
The last time Denver had a month with above normal precipitation in recent times was October 2005. (Lets just say DIA had a below normal month much of the Front Range saw 2-3 inches of rain for the month with some of the heaviest rains in Douglas County. So bear that in mind as you read the stats for DIA.).
August 2006 continued the below normal precipitation streak with 10 months in a row. The total of 1.13 inches for the month was 0.69 inch below the normal of 1.82 inches. Maximum 24 hour precipitation occurred on the last two days of the month with 0.35 inch reported at DIA. Through August 31st, the annual total is 5.22 inches, or 6.85 inches below normal of 12.07 inches. With 2002 having been recorded as the driest ever in Denver since 1872, DIA is 0.90 inch below what was recorded through August of that year.
There were twelve 90 degree days recorded during August 2006 which is 3 above the normal of nine. No 100 degree days were record for August. Seasonal total for 90 degree days is at 54 which puts 2006 in 5th place. The normal through August is only 31. Sixty one 90 degree days is the current record recorded in the year 2000. Temperatures ranged from a high of 96 degrees to a low of 43 degrees. All in all temperatures were pretty much normal for the month with an average of 72.8 degrees, just 1.1 degrees above the normal of 71.7 degrees.
September is normally a sunny, pleasant month in Denver with the highest monthly percentage of sunshine for the year. The general weather pattern features fall-like weather consisting of bright sunny days and clear cool nights.
Summer can linger as late as the end of the month. On September 30th 1980 a record was set when the temperatures reached a high of 90 degrees. In fact, the first 20 days of September all have record highs in the 90s. 97 degrees stands as the hottest temperature ever recorded during September and that occurred 4 different times, with the last 2 occurrences recorded on September 1st and 4th in 1995. Thunderstorms are still around in September, however, they are less frequent and severe storms are rare.
Winter can also sneak in during September. The earliest measurable snowfall on record occurred on September 3rd in 1961 when 4 inches of snow fell at the old Stapleton Airport and the temperature dropped to 33 degrees. The earliest freeze in Denver was September 8th in 1962 with a record low of 31 degrees. A real taste of early winter came in 1985 when on the 29th, 9 inches of snow fell on the city and the mercury dropped to a low of 17 degrees after only reaching a high for the day of 29 degrees. Both of those temperatures were records for the date. Although we can see snow during the month of September there have been 79 Septembersí since 1882 that have reported no snow.
Sunrise/Sunset (Denver area)
May 2006 to September 2006