September was the 10th cooler than normal month out of the last 12 and, on average, the last 12 months have been the coldest yet in the last (almost) 9 years.
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In Harpswell, temperatures were very close to normal during 2018, after two warm years in 2016 and 2017, as shown in the first graph below. Here, and in the second graph, normal is defined by the average during 1981-2010, the 30-year period currently used by NOAA. The second graph shows results by season, which do not line up exactly with years, since the meteorological seasons run from December to November. Fall 2018 was the coldest season, relative to normal, and the coldest since the very cold winter of 2014-15. December 2018 was just about normal, while December 2017 was much colder than normal, tipping the annual results to the warm side despite the four seasons averaging slightly on the cool side.
Worldwide temperature anomalies, which were recently release by NOAA, are shown in the third graph, relative to the pre-industrial period 1880-1920. As reported by NOAA, 2018 was the 4th warmest period since global records have been kept, only surpassed by 2015-17. The graph also projects future temperature anomalies if current trends continue. The blue dots follow the annual trend since 1970 and the red dots follow the trend in 10-year averages since 1980. The projections go out to 2050 and the scale shows the key numbers from the Paris Agreement: plus 2.7 and 3.6 degrees Fahrenheit over the pre-industrial period. Specifically, the goals of the Paris agreement were: "Holding the increase in the global average temperature to well below 2°C (3.6°F) above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C (2.7°F) above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change." On current trends, which have been quite steady for 40-50 years, we will hit +2.7°F between 2045 and 2050. Nothing too surprising last year globally, third warmest on record, consistent trend in the 10-year average red line continues. The Portland 10-year average hits 2.5 degrees above the 1951-1980 reference period, more than double the global anomaly.
After a very warm October, we finally had our first frost on November 8th. The remainder of November and the first week of December brought fairly normal temperatures, before we had some increasingly wintery weather through year end. The second graph shows 5-day average temperatures for the 4th quarter of the last three years. The 5-day average in 2017 fell from an above normal 40 degrees on December 9th to a frigid 3 degrees at the end of the year. That was the lowest 5 day average in the 7 years I have had my weather station here in Harpswell.
The 3rd and 4th graphs show the monthly and seasonal temperature anomalies for those seven years. If we consider a month or season outside the range of +-2 degrees from normal unusually warm or cold, we have had 32 unusually warm months (and 9 unusually warm seasons) and only 7 unusually cold months (and only unusually 1 cold season) during these years. Yes, April was warm and May only slightly cooler than normal, but the average temperature for March-May was below average, the first cooler than normal season since the summer of 2015. After hitting 70 degrees four times in April, we did not reach 70 again until May 16th. We had 17 days with measurable rain in April and 19 in May. Summer always takes its time arriving in Maine!
After a cold start with 4" of snow on the 1st, it was a mostly normal month of April with the exception of four significantly warmer than normal days, which pushed the average temperature for the month to just over 2 degrees above normal. Since July 2011, we have now had 32 months with temperatures at least 2 degrees above normal and only 6 with temperatures more than 2 degrees below normal. Total snow for the winter (we hope) came in at 87.5", a surprisingly high number given the well-above normal temperatures that generally ruled in January and February.
So much for warmer than normal weather! March was the coldest month relative to normal temperatures in two years and only the third colder-than-normal month in the last 17 months. In addition, the average temperature was lower in March than both January and February, a rare occurrence in these parts. As you can see on the second graph, this had not happened in the 7 years I have had my weather station; in fact, March had never been colder than either January or February during this period.
We are now up to 8 consecutive months with above normal temperatures here in Harpswell and 6 consecutive seasons above normal. February tried to break the streak but could only maintain colder than normal temperatures from the 7th to the 14th. We did manage to get 42" of snow during the cold spell, but the remainder of the month was much warmer than normal and the snow is now gone except for the dwindling piles left by the plows.
The graphs below show historical annual temperature anomalies, i.e., differences compared to the reference-period average from 1951-1980, for Portland (ME), US and global. The red lines are five-year average anomalies. The last year cooler than the reference-period average was 1982 in Portland, 1993 in the US and 1976 globally. Some skeptics have pointed to the relatively flat global temperatures from 1998 to 2011, but each of the last three years have set records and the ten-year averages clearly show the steady upward trend since the mid 1970s.
Sorry, Harpswell weather fans, it has been a busy summer but here is a brief update on the weather since May. The chart shows that our summer (meteorologically: June, July and August) was warmer than normal, making it the 4th consecutive above normal season. It has seemed like it was more than just 1 degree above normal, perhaps because as of today we have only had 3 cooler than normal days since August 14th, and we haven't had a low temperature below 53 since June 17th.
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SOURCEWeather statistics are based on 5-minute readings at an Ambient Weather station near Mill Cove off of upper Harpswell Sound. Archives
December 2015
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