May 2012 Alaska Weather Summary

June 22, 2012



May 2012 weather graphic for Juneau, AKIn contrast to April, a month that recorded above normal temperatures, May 2012 was seasonably too cold. Nineteen of the 20 first order meteorological stations in Alaska reported negative deviations. A mean deviation of all 20 stations from the long-term mean could be calculated as minus 2.7 degrees Fahrenheit. Barrow was the only station with a positive deviation, but only slightly so with 0.5 degrees Fahrenheit. Arctic Alaska has shown the greatest warming over the last decades and this trend appears to continue. The stations with the largest negative deviation were found in western Alaska: Kotzebue with minus 5.4 degrees and St. Paul Island with minus 5.2 degrees. This might be an effect of the lingering sea ice in the Bering Sea, which in March reached the greatest extent seen since 1979. That year is the point when continuous satellite coverage in the microwave wavelength bands became available. Microwave instruments have the ability to look through clouds and darkness, necessary for collecting imagery in winter.


The monthly flip-flop in temperatures continued on into May. November had temperatures far below the expected values, while December was much above normal and, for most stations, substantially warmer than those of November. January was much colder and many new low temperature records were observed. Then, in February, temperatures for most of Alaska were above normal, with only the first and last days of the month being seasonably below normal. March was colder than normal, and most stations recorded lower temperatures than those in February. April was above normal, followed by a seasonable cold May. Further, May is the first month of 2012 when Anchorage’s monthly temperature was lower than that of Fairbanks. The maritime climate of the coastal areas normally experience warmer temperatures in winter and lower temperatures in summer as compared to the climate of Interior Alaska. 

Persistently cool daily maximum temperatures at the start of May allowed Juneau to set a new record cold month in terms of the average daily maximum temperature of just 48.9 degrees Fahrenheit; 7.7 degrees below the previous record from 1955. Nevertheless, the extensive cloud cover meant the average daily low was near normal. The monthly mean temperature, 44.7 degrees, made this the eighth coldest May on record for Juneau for that statistic. On May 18, the temperature reached up to 63 degrees in Nome, a new daily record, topping the 1980 record of 62 degrees. All other daily extreme records for May were record low temperatures.


Precipitation was above normal for eleven of the 20 stations. The greatest positive deviations above normal were found for Barrow (178 percent), Annette (83 percent), Gulkana (82 percent) and Juneau (77 percent). At the other end of the spectrum were Talkeetna, with only 23 percent of the expected value or 0.38 inches of the normal of 1.62 inches and Bethel with 42 percent or 0.48 inches of the normal of 1.14 inches. As the positive deviations were larger in magnitude, the mean of the 20 stations ended up positive with 15 percent or differently expressed, about one-seventh more precipitation fell in Alaska in May than normal. The precipitation deviations for the different stations are in the table below:


On May 16, 0.84 inches of rain fell in Nome, more than double the 1990 record of 0.4 inches for this day and made up nearly all of the rain for the month’s total of 0.88 inches. In addition, it was the wettest day ever record in May; the historical record dates back to 1907. 

According to the National Weather Service, “"Greenup”' day for Fairbanks was May 10. The average day is about May 8.  Low precipitation for the Interior for the first third of the month resulted in low humidity. The humidity combined with high winds on the 11th resulted in red flag warnings. A number of small wild fires erupted around Fairbanks and Delta Junction, but were contained quickly. 


A new precipitation record occurred in Fairbanks on May 25. On that date, 0.52 inches of rain fell, just above the 1973 record of 0.5 inches. This record rain combined with last season snowmelt generated rapidly rising river levels in the Interior and flood advisories were issued for Chena, Salcha and Goodpaster rivers. This heavy precipitation terminated the wild fire concerns from earlier in the month. A late winter storm with strong winds and drifting snow on May 27 resulted in a travel advisory being issued for the Chandalar region of the Dalton Highway.


It was an extreme winter for sea ice in the Bering Sea. As noted before a record extent was observed in March. On May 3, St. Paul Island was engulfed in ice, and had been for 103 days. At that point, the ice had yet to retreat north of the island. The previous record was 100 days reached in 2010. St. George Island also set a record of 79 days, topping the old record of 60 days, also from 2010.


This information consists of preliminary climatological data compiled by the Alaska Climate Research Center, Geophysical Institute, University of Alaska Fairbanks. This summary is based on the 20 first order stations in Alaska operated by the National Weather Service. Extreme events of other stations are also mentioned. It should be noted that the new climate normals for the time period of 1981-2010 are applied for the calculations of the deviations, and they can be slightly different from the old normals (1971-2000), which were in use up until end of July 2011.