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Fall 2009 - Maine’s Weather – 2009

The early part of 2009 was unusually cold throughout the Northeast. On January 16, an instrument at the Big Black River USGS station in northwestern Maine recorded a temperature of -50 F, immediately a candidate for the coldest reading ever in the state (at least during the period of modern instrumental measurements). This reading triggered the convening of the Records Verification Committee for Maine, and the committee met twice (by phone) to discuss the relevant issues. The Committee consisted of representatives of the NWS Caribou office, the USGS office in Augusta, the Maine State Climatologist, the NOAA Northeast Regional Climate Center in Ithaca, and the NCDC in North Carolina. After appropriate challenges, including testing of several pieces of equipment, the group voted unanimously to approve the record as official. That reading now stands as the coldest for Maine, replacing the previous record of -48 F from nearby Van Buren in 1925. The -50 F record for Maine also equals the all-time record cold temperature for any New England state (Vermont having that same value).

Then, in April, we had unusually warm temperatures for several days. Many stations recorded temperatures that were 8-11 degrees warmer than the previous record high for the date at those locations. On April 28, the Portland reached 92 F, the first time that temperatures had ever exceeded 90F in April and 11 degrees more than the record for the date. Daily records for several stations were also set on April 26. April temperatures in Portland were three degrees above the 30-year average.

Of course, the big news for summer involved precipitation. After relatively dry months of April and May, the rains began in June and continued through most of July. When the patterns of regular rains finally ended, the months of August and most of September have been beautifully dry and clear, with almost no precipitation over most of the state.

These patterns of long stretches of similar weather are notable when they happen, but are really quite normal. Generally these patterns result from rather stable positions of the jet-stream winds that circle the northern hemisphere in a wave-like pattern centered on the North Pole. When those patterns are configured so that low-pressure systems pass through Maine, we usually see one rain event after another.

These kinds of weather patterns are not unusual, but they bring up an interesting contrast with the long-term climate patterns for Maine. For example, the average precipitation for Maine is quite even, with slightly less that one inch per week throughout the year. (This lack of seasonal variability is actually quite unusual globally; most places have large differences in average precipitation from one season to another.) Of course this nicely illustrates the difference between weather and climate (average weather).

 


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