Halloween Weather

With an average high of only 46 degrees and an average low of 27 degrees it takes a day well above average to make trick-or-treating an event where a jacket and mittens are not a requirement in our area. Today looks to be another typical chilly Halloween, but not as cold as some.

This decade has recorded three years (2002, 2003, 2006) with high temperatures only in the low 30s, all of those years rank in the top 15 coldest since 1881. In 2006 there were even snow flurries in the air during the evening hours. The last year with measurable snow on Halloween was back in 1995 when one inch of snow fell. But Halloween has also had its share of mild days. Back in 1999 it hit 74 degrees and that was followed by two more nice Halloweens in 2000 (when a thunderstorm moved through during the evening) and 2001 when we hit 60 degrees.

Cold High

The warmest high temperature this month has only been 62 degrees recorded on October 18. Since 1881 only one other October, 1925, has recorded a cooler monthly maximum when the warmest temperature that October was only 60 degrees.

We have experienced some seasonally cold mornings this month, including a record low of 17 degrees on the 13th and a 21 degrees low on the 12th, but our average daily minimum so far this month has been 34 degrees which is right at the long-term October average. Instead, it has been our daily maximums that have made this month one of the top ten coldest on record. Our average daily high temperature so far this month has been 47 degrees which is 11 degrees below the October average of 58 degrees.

It is likely we will finish this month approximately six degrees below normal with that entire anomaly being attributed to our cold daily maximums.

The End of Platform Shoes

The latest seventy degree day ever recorded in Fargo Moorhead was on November 17, 1953, so you can never say never in our climate, but the odds are quite high that we have recorded our last seventy degree temperature for the year. Our last seventy occurred back on September 26 when we recorded a high of 77 degrees.

If that holds, this would be only the 8th time since 1881 Fargo Moorhead did not record at least one 70 degree day in the month of October or November. Four out of the previous seven Octobers without a 70 occurred in the late 1970s and early 1980s, including 1979, 1981, 1982, and in 1985. 1985 also holds the distinction of having the earliest last 70 degree day which occurred on September 18 that year.

The other years without a 70 degree high in October were in 1881, 1883 and 1925.

 

Gloomy

Back in September there seemed to be a bounce in everyone’s step and genuine excitement over the great weather that dominated almost the entire month. Almost daily in emails, phone calls or personal conversations someone would ask if we were going to break the record for the warmest September since 1881.

This month all of that has changed and there is no glee in the persistent clouds, rain and cool weather that has dominated our weather for the past three weeks. Although the first half of October was the coldest on record, the phone and email inboxes are not full of messages asking if this will be the coldest on record, or because of the rain, the wettest on record. If you must know, the answer to both is likely no, but we will finished the month in the top ten in both categories.

The weather pattern will change eventually, but probably not until sometime next month.

Not a lot of Aces

Not only has tropical activity in the Atlantic Basin been slow this year, but also in all tropical areas around the globe. Although the number of named storms usually gets the most attention, it is only one factor in the determination of tropical activity. The National Oceanic and Atmospheric Administration (NOAA) also uses the strength and duration of each tropical storm to calculate what they call the Accumulated Cyclone Energy (ACE) index.

The combining of the number, strength and duration of tropical systems into a set mathematical equation can give a much better insight into the differences between tropical seasons rather than just counting the number of storms alone. Since good satellite records started in 1979, the year 2009 has the distinction of the having the lowest ACE index measured. In fact, there has been a noticeable decrease in tropical energy worldwide in the past few years.

Wet and Dry

With a week left, this October already ranks as one of the top ten wettest since records began in 1881. At least a trace of rain has fallen on 17 of the first 23 days this month. Through Friday, 4.00 inches of rain has been measured officially in Fargo Moorhead already ranking this month the 7th wettest on record.

Although the past three weeks have been much wetter than average, since April 1, the airport is actually running nearly 2 inches below normal. In fact, 2009 has been quite dry with the exception of March and October. March finished as the wettest recorded with a rain surplus of 3.45 inches and this month currently is running 2.47 inches above normal. But because the rest of the year was exceptionally dry, our yearly rain surplus from average is currently around 2 inches.

In comparison at this point last year we had a rain surplus of over 8 inches.

Persistence

The record breaking cold weather so far this month has only produced two daily records. On October 10 a new low maximum record was set when the high temperature only managed to hit 35 degrees. The old record was a high of 36 degrees set back in 1935. The other record was a low of 17 degrees on October 13 which tied the record for that date last recorded in 1979.

It has not been the extremes of temperature that has made this month so cold, but instead it has been a persistent upper-level wind flow that has kept the upper-Midwest locked in cool Canadian air. Plus, the storm track has also been locked in place for the past three weeks bringing numerous storms to the area. That combination has made almost the entire month cloudy, keeping the low temperatures near normal, but making the daily highs ten to twenty degrees below seasonal averages.

Record Cold October

The first 15 days of October was a remarkable contrast to the warmth of September. You may remember that September was the 2nd warmest since 1881 but now the first half of October was the coldest such stretch since records began.

Although the past few days have brought warmer temperatures, before this weekend, the average temperature in October was a remarkable 10 degrees below average, a full one degree colder than any other recorded start of October. Also, whereas September was our 6th straight month with below average rainfall, October has been quite wet. Through the 15th this has been the 6th wettest October with 3.31 inches measured. Plus, it has been the 7th snowiest to that point with 0.7 inches recorded.

Does this mean a cold winter? Every year has unique weather, but none of the other years that started this cold and wet in October finished as a top ten coldest or wettest winter.

 

Our State Climatologist Dr. Adnan Akyuz sent this email to me with some more stats:

 

Daryl,

You are right. October 1 through 14 happens to be:

 

· the 10th coldest in terms of lowest minimum temperatures (see below):

 

Fargo Extremes
Lowest Average Minimum Temperature degrees F
Days: 10/1 – 10/14
Length of period: 14 days
Years: 1850-2009

Rank Value Ending Date
1 29.0 10/14/1935
2 30.9 10/14/1952
3 31.0 10/14/1989
4 31.3 10/14/1979
5 31.6 10/14/1993
6 31.9 10/14/1917, 10/14/1985
8 32.0 10/14/1885
9 32.6 10/14/1902
10 32.9 10/14/2009, 10/14/1883, 10/14/1987

· the coldest in terms of lowest average temperatures (see below):


Fargo Extremes
Lowest Average Average Temperature degrees F
Days: 10/1 – 10/14
Length of period: 14 days
Years: 1850-2009

Rank Value Ending Date
1 39.7 10/14/2009
2 40.7 10/14/1925
3 42.4 10/14/1935, 10/14/1917
5 42.5 10/14/1985
6 42.9 10/14/1894
7 43.0 10/14/1959
8 43.1 10/14/1979, 10/14/1881
10 43.3 10/14/1983, 10/14/1883

· the coldest in terms of lowest maximum temperatures (see below):


Fargo Extremes
Lowest Average Maximum Temperature degrees F
Days: 10/1 – 10/14
Length of period: 14 days
Years: 1850-2009

Rank Value Ending Date
1 46.5 10/14/2009
2 48.1 10/14/1925
3 51.3 10/14/1894
4 51.4 10/14/1983
5 51.9 10/14/1959
6 52.4 10/14/1927
7 52.7 10/14/1946
8 52.8 10/14/1932
9 52.9 10/14/1881
10 53.0 10/14/1985, 10/14/1969, 10/14/1917

So it was the lack of daytime heating as opposed to nighttime cooling that made it happen. Interestingly, it came just after the warmest September on record in terms of the minimum temperatures. Who said persistence is a good measure of forecast?

 

Adnan
 

October Blizzard

On October 15-16, 1880 one of the earliest blizzards ever recorded struck eastern South Dakota, southwestern Minnesota and northwestern Iowa with wind gusts over 60 mph, heavy snow and drifts over 15 feet high. That storm was made famous by Laura Ingalls Wilder in her book “The Long Winter” as the October Blizzard.

Since that storm nearly 130 years ago, significant October snows have been rare. There was the Halloween Blizzard of 1991 covering much of Minnesota, perhaps being the one exception, although more fell on November 1 than on Halloween. In our area the last significant October snow was on October 24, 2001 when 5.4 inches was recorded. That one storm also placed October 2001 as the second snowiest October on record.

The snowiest October on record was back in 1951 when 8.1 inches fell during a storm on October 29-30. So although snow in October is common significant snowfall is not.
 

Early Snow

The accumulating snow this week in the Twin Cities was the first time since 1977 that greater than one inch of snow was recorded this early in the season. Plus, it was only the 9th time in the last 60 years that an accumulation of any size has occurred during the first half of October. It was also the first accumulation of snow officially in the Twin Cities during any part of October since 2002.

Significant snow in October is rare in Fargo Moorhead, let alone in areas to our south like the Twin Cities. The last time a significant October snow fell in Fargo Moorhead was on October 24, 2001 when 5.4 inches of snow fell. That one storm also placed October 2001 as the 2nd snowiest on record. In the Twin Cities the last significant October snow was the Halloween Blizzard of 1991 when 8.2 inches fell with nearly 20 additional inches falling on November 1 and 2 of that year.