Number 4

Today is the last day of meteorological autumn meaning that tomorrow will be the beginning of winter for climate purposes.  This past autumn finished above average for both temperatures and precipitation and this brings up the question as to what we can expect this upcoming winter.

The past three winters have been colder than average in Fargo Moorhead and there are strong indications this the winter of 2010-2011 will be our fourth.  Many of you have likely heard that La Nina conditions are currently occurring in the Pacific Ocean which often leads to colder than average winter temperatures for our area.  Although this is true, that is only one of many factors in a complex array of atmospheric and oceanic interactions that influence weather patterns across the northern hemisphere.

Several of these other factors also suggest a high probability for colder than average temps for this entire region.  We will experience our normal weather fluctuations this winter, but in the end the odds favor more cold days than mild ones.

Negativeville

This past Tuesday, November 23, the official low in Fargo Moorhead was -8 degrees.  That was the first below zero reading of the season and the earliest such occurrence since 2003.  In eight of the past ten years the first below zero reading of the season was recorded later than average.  The average first negative reading during the second half of the year falls on November 28.

One of those two years in the past decade with an early below zero reading was back in 2003 when we dropped to -2 degrees on November 8 which is the 7th earliest on record. The earliest below zero reading occurred on October 26, 1919 and the latest such occurrence was on December 31, 1987. Therefore, since 1881 we have never made it into the new year without recording at least one day with a below zero temperature.

Fargo Moorhead averages 48 sub-zero winter days, with ten of those days having both the high and the low temperature remain below zero.

How Much Fell?

After most snow events there are always questions about how snow is measured.  These questions usually come from the point of view that the official measurement was different from what they measured.

The official snowfall in Fargo Moorhead is measured in north Moorhead.  To properly estimate the accumulating snow, snow is measured on a white board which lessens the amount of possible melting.  Plus, measurements are taken approximately every 6 hours and then the white board is cleared of snow.  This process helps eliminate the settling of the snow as it falls.

The clearing of the snow in combination of the use of a white board are the two principle reasons why the official snow total is often times higher than what is shoveled off your driveway.  This past Monday was an example of this as the 12.6 inches of snow officially measured settled to as little as 8 or 9 inches by the end of the day, yet the official measurement more accurately reflected what actually fell.

November Snow Records

Snow events and speaking engagements have kept me away from writing much this week, but the 12.6″ from Monday’s snow was the 2nd highest daily total of snow for the month of November.  Here is the list:

14.0?  11/14/1909

12.6″  11/22/2010

12.4?  11/10/1919

12.0?  11/20/1977

10.9?  11/28/1960

10.5?  11/21/1893

9.0?   11/26/1896

8.6?   11/16/1996

Cold Mirage

Every Thursday morning at 11:30 AM during the ?Christopher Gabriel Show? on WDAY AM-970, I participate in a segment where we talk about and answer questions about the weather.  Last week, a caller asked about what causes the distortion of objects during the winter.

During most of our cold season, the temperatures aloft are frequently warmer than those found near the surface, especially when there is snow on the ground.  Because the air in this cold surface layer is denser, light from distant objects entering it bend in such a way that these objects can appear shifted upwards.  This is referred to as a superior mirage.  What this can do is make distant objects appear larger; for example; make a small rise appear to be a large hill or mountains appear to be even higher.

It can also make things beyond the horizon visible giving the illusion that those objects are much closer and sometimes larger than they actually are.

Thundersnow!

The 8 inches of snow officially measured this past weekend at the Minneapolis/St. Paul Int?l Airport, was the highest pre-Thanksgiving snow event since the Halloween Blizzard of 1991 in the Twin Cities.  Plus, it was only the 3rd snow event in meteorological autumn (September through November) to exceed 6 inches since 1997 for that area.

The event was probably even more note-worthy because it occurred just three days after a record high of 68 degrees was observed.   The heaviest snow from that event fell in a narrow band from northwestern Iowa, to Mankato, through the Twin Cities up to Duluth.  In that narrow band, snowfall rates of 2 inches per hour were observed at times, plus several locations reported cloud to ground lightning strikes during the heaviest snow bursts.

Thundersnow is always a sign of strong convective currents in the atmosphere that lead to heavy snow.  It is likely that the areas with the heaviest snowfall will see a continuous snow cover through next spring.

Sub Milestones

There are many milestones we reach as this area moves from season to season.  Two upcoming temperature milestones will be our first day with a subfreezing high temperature and the other will be our first below zero low of the season.

Our average first day with a high temperature below 32 degrees is November 5.  Not only have we not recorded such an event this season, we have only experienced one day with a high in the 30s.  Our coldest high temperature this autumn was a 37 degree high on October 28.  Last year we did not record a low below freezing until December 2, the latest on record.  Although, just a few days after that we observed a low temperature below zero, so it did turn cold quickly thereafter.

It appears we will be experiencing a sub-freezing high temperature next week for the first time since March 19.  As for our first sub-zero morning, the average date is November 28, meaning we are likely not too far away from that observance as well.

Weather Talk

The weather tends to always be the most talked about subject in this area, but the great start to November made this even more noticeable.  Once we reach November the general expectation is for winter to quickly settle in with cold and snowy weather.  Historically, that has definitely happened, but most years, the first half of November is still reasonably pleasant.

Granted, not every year has November started out as nice as this one, as the first 10 days of the month was the 3rd warmest such period on record.  Yet, as recently as last year we experienced the 2nd warmest November on record, although it did start off a bit cooler than this year.

Many recent Novembers, especially the first half, have treated us fairly well temperature wise as 7 of the top 25 warmest starts of November have occurred since 1999, with a majority of those years maintaining that above average warmth through the entire month.

Late Sunrises

When it comes to the amount of daylight observed over the course of the year, it is common knowledge that the days around the Winter Solstice provide every one in the northern hemisphere the shortest amount of day length of the year.  It is also well known that the latest and earliest sunrises and sunsets also occur near the winter solstice, or do they?

Because of the recent extension of daylight saving time to the first Sunday in November, plus, this changeover occurred as late as possible this year, Saturday, November 6 will end up having our latest sunrise of the year.   This past Saturday morning the sun rose at 8:17 AM, likely several minutes later than it will near the Winter Solstice.  It varies slightly from year to year, but our latest sunrise coming up will be around 8:12 AM in another 7 weeks.

Granted this is all just a trick of when and how daylight saving time is observed, but it was certainly staying dark very late in the morning before the time change.

Is the Weather Freaky?

I was recently reading the blog ?Wildwings?, found within areavoices.com, written by our company pilot, Keith Corliss.  Keith is an avid birder and in a recent blog post was pondering the different definitions of the term rare.

When dealing with birds, a very common bird elsewhere could be considered rare in an area where it is not usually seen.  Some birds like Whooping Cranes, would be considered rare just because of their very limited numbers.

Many of these analogies can be transferred to the world of weather.  Snow storms are certainly not rare locally, but in Florida it would be rare to see a snow storm.  Too frequently, weather events are classified as freaky, extraordinary or even crazy.   Some weather events are certainly rare, as they occur infrequently in certain areas.

Yet, just as a birder seeing an uncommon bird would not garner talk of a freak, but instead, just a rare observance, weather phenomenon should also not be considered freaky just because it is experienced rarely.