Each spring, there are usually many inquires as to when our first 60 or 70 degree reading can be expected. Our long term average first 70 degree reading of the spring occurs on April 18. Each spring, of course, we are guaranteed to eventually record that first 70 of the season. In the autumn on the other hand, it is difficult to know when we have experienced our last such day of the year.
This past Wednesday, the official high temperature was 71 degrees and the question has been asked of me several times if that was the last 70 of the year. The average last 70 degree day of the year is October 18. We have recorded a 70 degree day after that average only twice in the past decade.
Although we will be experiencing cool weather over the next several days, the over all pattern may yet give us one last warm day before the cold of winter settles in permanently.
The first half of autumn is nearly complete and the past 6 weeks have been one of the warmest starts of fall since 1881. This year continues the trend of milder autumns that this area has recorded in recent years. This trend of warmer temperatures this time of year has increased the average temperature for September, October and November by 1 degree. The average autumn temperature from 1971-2000 was 43.5 degrees and our current 30-year average from 1981-2010 is 44.5 degrees.
Some of you may take this as a sure sign of global warming, except, the average fall temperatures from 1931 through 1970 was also 44.5 degrees. You see, a series of cool falls in the 1970s and 1980s caused an over decrease in the average and our recent stretch of mild autumns has help increase our autumn temperatures closer to the long-term average after a brief period of cooler conditions.
This is yet another example of how climatic conditions subtly change over time.
A nice pileus cloud was seen topping a small thundershower north of Fargo yesterday afternoon. Rapid rise in the cumulus cloud cause the mid-level wind to rise and fall over the building cumulus creating the pileus cloud. This photo is from one of our viewers, I didn’t have a camera handy when I saw it yesterday (I need a cell phone).
This month marks the beginning of what hydrologists refer to as the new water year. October is used as the beginning of the water year because across much of the United States this is the time of year when water inputs begin to exceed loss to evaporation. Although our current wet phase has on several occasions allowed for summer precipitation to exceed evaporation, historically, late fall and winter precipitation was an important recharge time for area soils.
Our just completed water year brought 26.85 inches of rain officially to Fargo Moorhead. The WDAY studios recorded 25.49 inches during the same period. The main difference between those two reports occurred with the heavy rain event on August 1 that hit the airport much harder than other parts of town. The 2010-11 water year was the 23rd wettest on record, and fortunately, significantly drier than the 2009-2010 water year that was the wettest such period on record when 32.79 inches of rain and melted snow was recorded.
When you see a report that the wind speed at the airport is, for example, 15 miles per hour, it would be unusual for the wind speed to actually be steady at that speed. Officially, the so-called sustained wind is actually the averaged wind speed over a period of 2 minutes. It is only when there is a brief and sudden increase of the wind of at least 10 mph over that averaged wind that a gust is reported.
Therefore on most occasions the wind does not blow at a steady pace, but instead blows constantly at slightly differing speeds and often blows in a series of gusts of differing magnitudes.
There are many reasons the air motion in the atmosphere is not steady, but the most common are, differential heating, which creates thermals and uneven mixing of the air and that the terrain is not uniform and therefore the wind movement is not allowed to flow evenly over the surface of the earth.
The warm weather this week has prompted several individuals to ask me if temperatures in the 80s this time of year is unusual. Including this month, 64 of the 131 Octobers on record have recorded at least one day with a high temperature at or above 80 degrees, Although recording a high in the 80s happens in about one-half of all Octobers, what is more usual are years with multiple 80 degree days.
There have been only 22 Octobers with three or more 80 degree days with a maximum of seven set back in October 1910. Last year, Fargo Moorhead recorded three 80 degree days, all consecutively from October 8-10. The longest 80 degree consecutive streak in October occurred in 2003 when for 5 straight days, October 6-10, the high reached 80 degrees or higher.
That record may be in jeopardy of being broken this week if the clouds can stay away the next couple of days.
Since my blog post last week about the Red River being so high, it has dropped quite a bit, still high, but a much lower flow: Here was that drop last week:
Here is the latest chart:
The Red River is now according to our weekend Meteorologist Rob Kupec at the lowest level in two years. He did a story about the river and why it dropped in the past week. You can find it online here:
Preliminary numbers indicate that the average temperature in September was 59.9 degrees, which is 0.8 degrees above the current 30-year average. If you are thinking that last month felt warmer than just one degree above average you are not alone as I also thought the same thing.
Part of the illusion of last month being warmer than it really was can be attributed to the average high temperature being nearly 4 degree above average. Most individuals notice the high temperature more than the low temperature during the warm season, with the opposite being true during the winter. Those afternoon temperatures were likely enhanced by the dry soils and the overall low humidity levels that dominated much of the month.
Those same conditions that lead to warmer afternoon temperatures also are the same ingredients that make for cool morning lows. It was the low temperatures finishing nearly 3 degree below normal that kept the overall average temperature last month cooler than what many of us would have guessed.
As September started, Fargo Moorhead had already received 22.16 inches of rain and melted snow since the beginning of the year. This was nearly as much as our current average yearly precipitation of 22.58 inches with four months left in the year. As we start October, the total precipitation for the year now stands at 22.39 inches, which means only 0.23 inches of rain was recorded during September.
Last month was the 4th driest September on record and it was also the first time since 1993 that less than one inch of rain was measured during the month of September. The dry weather in September was a continuation of the pattern that started in August. In the past 55 days, only 0.65 inches of rain has fallen in Fargo Moorhead which has made for some very brown yards.
Recent autumns have been exceptionally wet locally, but historically, this time of year would be a timeframe with a high fire risk as the vegetation dried and at least for now, the area has the appearance of past autumns