Monthly Archives: September 2009

The End of 70?

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With the cooler weather that has been in the area the past few days I have been asked numerous times if that means we won’t be seeing anymore 70 degree weather this year. Fargo Moorhead has officially hit 70 degrees or higher at least once in all but seven Octobers since 1881.

The last time we did not hit 70 degrees in October was back in 1985. In fact, four out of the seven years no 70s were recorded this month occurred during years between 1979 through 1985 when a series of cool falls occurred. The most 70 degree plus days this month occurred back in 1963 when a remarkable 19 days that month were at or above 70 degrees.

I would not expect anywhere near that many this year, but if history is our guide at least a few more days this month will probably be in the 70s.

 

Streaking

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Through yesterday every day this month the mean average temperature had been at or above the average. Only one day had been right on the average, which was September 1, which means we had a stretch of 26 straight days with above average temperatures. That was by far the longest above average stretch of temperatures in 2009.

This is not surprising considering how cool the rest of the year has been. Back in July and August there was a period with 31 out of 33 days recording temperatures below average and through August 31, 64% of the days this year finished below normal. Unless we finish the year remarkably warm, 2009 will finish with a below average temperature, but the extreme warmth of September may have saved us from experiencing our second straight year with a yearly average temperature below 40 degrees.

This is something we have not seen since the 1970s.

Quiet Storm Season

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Although the southern portion of the United States does have a second severe storm season in October and November, in most of the country, the summer storm season is winding down. As of this writing, 850 tornadoes have been reported in the United States so far this year, whereas in 2008, 1691 tornadoes developed.

This has been a significant drop over not only last year, but the past several years when the seasonal average has been around 1300. The overall cool spring and summer seasons over the eastern half of the United States were not as conducive to severe weather this year as it is in a more average year. Although you can never blame one factor for changes in weather, the transition from the La Nina conditions in the Pacific Ocean the past few years to our current weak El Nino probably played at least a small role in the quieter storm season experienced this year.

Increasing Ice

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The annual melt cycle of the Arctic Ocean appears to have ended on September 12 as the ice cover has been quickly expanding the past two weeks. The Arctic Ocean usually records it’s maximum sea ice extent in early March and it’s minimal extent in early to mid-September each year.

The total sea ice coverage area on September 12 was measured at 5.1 million square kilometers (2 million square miles) which was 13 percent more than last year and 23 percent higher than in 2007. You may remember that 2007 was the year that the sea ice coverage was the lowest recorded since satellite records began in 1979. Although warmer temperatures generally get the blame for lower sea ice coverage over the Arctic Ocean during some of the recent summers, research has shown that oceanic circulations around the arctic have played a larger role.

Recent climatic shifts could continue the trend of increasing ice in the arctic over the next several years.

 

Streaking 80s

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Last week from September 13-20, the official high temperature in Fargo Moorhead hit 80 degrees or higher each day. That stretch of eight consecutive days with a high temperature at or above 80 degrees was the third longest such streak since 1881 in the month of September.

The longest stretch of 80 degree high temperatures in September occurred in 1908 when 13 straight days were recorded from September 10-22, with two of those days recording a high in the 90s. That was also the year with the most days at or above 80 degrees in the month of September when 19 such days were recorded. With so many warm days in September, 1908, you would think that would be listed as the warmest September on record.

Instead, it currently ranks as the 10th warmest as 4 out of the last 5 days that month recorded a high only in the 40s significantly lowering the monthly average that year.

80s September

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Last week’s stretch of eight straight days at or above 80 degrees brought our monthly total of 80 degree days to twelve. Since 1881 this is the fourth highest number of 80s observed during the month of September. The long-term average for 80 degree days this month is six.

This is the most 80s Fargo Moorhead has recorded in September since 12 such days were observed during September, 2002. Plus, this month is only the 5th time since 1980 we have recorded 10 or more days in the 80s during the month of September, so indeed, it has been a very warm month to this point. In fact, this past summer was so cool, that this month has recorded more 80 degree days then either June or August did which both only had ten 80 degree days each.

The last time September had the 2nd most 80s in a year was in 2004.

60s

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The average high temperature in Fargo Moorhead is now in the upper 60s. The last day with an average high of 70 degrees was on September 16. An average daily maximum of 70 degrees will not occur again until May 16, a stretch of 242 days. If that depresses you a bit, the earliest 70 degree day in a year occurred on March 17, 1968 and our average first 70 degree day of spring occurs on April 18, so we rarely go that long between 70 degree days.

Plus, in most years an occasional high at or above 70 degrees will continue through the middle of October and on rare occasions even into the very early part of November. But sadly for most people, our average high temperature drops approximately one degree every other day and by Halloween the average high is 46 degrees which means our last 70 of the year will soon be a memory.

Cool Summer for Many

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The National Climatic Data Center (NCDC) released their statistic for the summer of 2009 last week. As a whole the United States experienced a cooler than average summer with most states east of the Rocky Mountains experiencing a cool summer with the exception of the gulf coast region.

The coolest readings were in the Great Lakes states and surrounding areas. Michigan had their 5th coolest summer with Minnesota, South Dakota and Wisconsin all recorded their 7th coolest summer since 1895. Taken as a whole, North Dakota had the 12th coolest summer on record with Fargo Moorhead locally having the 16th coolest since 1881, but the 13th coolest since NCDC has kept such statistics in 1895.

 

Precipitation-wise, the United States seemed to fall into two categories, either well above or well below average rainfall. Both Minnesota and North Dakota fell into the dry side of that equation with Minnesota having the 23rd driest summer and North Dakota the 24th.

 

First Frost

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Our average first frost date is September 24 and officially a temperature at or below 32 degrees has not occurred before that average date since 1995. The official thermometer of course, is located at the airport and there have been years that other parts of the metro experienced earlier frost dates then the average, but the general trend in recent years has been for later than normal first frosts.

In fact, Fargo Moorhead’s official first frost date has been in October for the past five years, including in 2004, the last year with a cooler summer than 2009. To answer the question, of course no one knows for sure, but based on current trends in the Northern Hemisphere, it appears frosty weather will stay away from Fargo Moorhead until around September 24 or perhaps later again this year. But, keep an eye on our extended forecast as it only takes one chilly morning.

Record High Minimum?

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On Tuesday morning the temperature was 70 degrees as we all started the new work week. That very mild morning prompted someone to ask me if that was a record for the warmest low temperature for that date. The record high minimum temperature for this past Tuesday, September 8 is 69 degrees. Although the temperature was indeed around 70 degrees in the morning, the rain that day cooled us off to 66 degrees at times in the afternoon, plus by midnight the temperature dropped to 64 degrees for the official low that day.

So the record high minimum of 69 degrees set back in 1897 was not broken. The all-time highest low temperature in the month of September is 73 degrees set back on both September 5, 1996 and on September 7, 1931. Since September 1996, we have recorded only one other 70 degree plus low during this month and that was a 71 degree morning on September 10, 2005.