Oregon Chapter
American Meteorological Society

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December 7, 2011

All-Time Weather Record To Be Broken

 

Did it feel chilly this year in the Pacific Northwest? If you answered yes, you would be correct. With less than 25 days remaining in 2011 and no significantly warmer weather on the way, the Portland International Airport is very likely to set a new all-time record for the least number of 60 degree or higher days in a calendar year. So far in 2011, the Portland International Airport has reached 60 degrees or higher just 169 times which eclipses every other year on record at that location. Records date back to 1940 at the airport. The next closest year to 2011 is 1950 and 1955 which each recorded 172 days at or above 60 degrees. Looking even further back, the last time Portland recorded fewer days at or above 60 degrees was in 1909 (102 years ago) with 160. Records were taken in downtown Portland prior to 1940. The average number of days that Portland reaches 60 degrees or higher in a given year is approximately 200. The lowest was set in 1893 with just 145 days, while the highest was set in 1885 at 244 days. When analyzing the complete set of data dating back to 1875 (136 years) including both the airport and downtown, 2011 is the only year in the past 102 years to break the 170 day threshold.

Below is a list of the top 20 years where Portland reached 60 degrees or higher the fewest number of times. A chart is also included showing every year from 1875-2011 with a 10 year average trend line in red. There appears to be a signal in the trend line data which suggests a cycle somewhat similar in duration to that of the PDO (Pacific Decadal Oscillation) which recently returned to the long term cold phase. After peaking in the 1980's and 1990's there is a notable decline in the number of 60 degree days in Portland over the past decade, with an even sharper drop in just the last few years. Portland now appears to be returning to a decadal average typical of what we saw in the 1950's through the 1970's.

Here are the top 20 years where Portland reached 60 degrees or higher the fewest number of times ---

Year

Number of 60 Degree+ Days

1893

145

1880

147

1899

151

1903

159

1901

160

1909

160

1886

164

2011

169

1894

170

1902

170

1920

171

1898

172

1905

172

1950

172

1955

172

1963

174

1882

175

1964

176

1933

177

1948

177

Here are Portland's highest, lowest and average number of 60 degree or higher occurrences in a given year and decade ---

Portland Complete Period of Record (1875-2011)

Average = 195

Lowest = 145 in 1893

Highest = 244 in 1885

 

Downtown Portland (1875-1947)

Downtown Average = 194

Downtown Lowest = 145 in 1893

Downtown Highest = 244 in 1885

 

Portland Airport (1948-2011)

Airport Average = 199

Airport Lowest = 169 in 2011

Airport Highest = 228 in 1992

 

Portland Decadal Averages

1875-1880 = 187

1881-1890 = 201

1891-1900 = 174

1901-1910 = 181

1911-1920 = 188

1921-1930 = 199

1931-1940 = 203

1941-1950 = 194

1951-1960 = 187

1961-1970 = 193

1971-1980 = 197

1981-1990 = 207

1991-2000 = 201

2001-2010 = 196

Steve Pierce
President, Oregon Chapter of the American Meteorological Society
Phone: 503-504-2075
E-mail: stevejpierce@comcast.net
Oregon AMS web site: http://www.ametsoc.org/chapters/oregon/