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Storms usher in first week of May

Storms this week:

After a relatively quiet first three months of the year, the NOAA Storm Prediction Center in Oklahoma reported 185 tornadoes across the nation in April and in the first week of May another 69, including 51 on May 6th, mostly in OK, KS, and NE.  In Minnesota there has been an increase in convective thunderstorm activity as well this month with over 25 reports of large hail, including 1.75 inch diameter stones near Stillwater on May 3rd.  There were also 7 reports of strong winds in Minnesota with gusts up to 60 mph near Mahtomedi. A summary of the hail storm over May 3rd is posted on the State Climatology Office web site

Unfortunately these storms have failed to produce widespread significant rainfall, which is much needed around the state.  Most observers report less than a third of an inch so far, with a few exceptions.  Albert Lea. Lakefield, Lester Prairie, Red Wing, Rochester, and Forest Lake reported over 1 inch of rainfall this week, while in the northeast Two Harbors, Grand Marais, and Grand Portage reported over an inch as well.  The US Drought Monitor this week increased the area of Minnesota designated to be in severe drought (D2) to nearly 40 percent of the landscape, mostly concentrated in northwestern and north-central counties.  Drought also expanded in coverage across the Dakotas and in Wisconsin as well. 

With the dry weather pattern of 2015 so far the MN-DNR reports that about half the state's watershed districts (36) are reporting abnormally low flow volume, and about half are reporting near normal flows.  Many lakes are at low levels as well for this time of year, including Schaeffer Lake and Island Lake Reservoir in St Louis County.  In some areas of the state 6 to 9 inches of rainfall is needed to remove the current drought classification.

Weekly Weather Potpourri:

Severe weather struck portions of OK, KS, and NE on Wednesday, May 6th.  In Oklahoma alone there were at least six reports of tornadoes, along with 2.75 inch diameter hail with straight line wind gusts to 82 mph, and record-setting rainfall amounts.   Some of the rainfall amounts included 8.82 inches at Oklahoma City and 7.64 inches at Union.  Widespread flash flooding was reported with many closed roads.  To add insult to injury, the central portion of the state reported a 2.9 scale earthquake.

Tropical Cyclone Noul was spinning in the Western Pacific Ocean east of Manilla in the Philippines this week.  It was expected to strengthen, with winds well over 120 mph and sea wave heights of 35-40 feet.  Landfall in the northern Philippines was expected by Saturday.

NOAA scientists reported this week through the "climate.gov" web site that the average monthly atmospheric carbon dioxide in the month of March exceeded 400 ppm for the first time this year.  This is estimated to be the highest level of carbon dioxide in at least 800,000 years.

The United Kingdom Meteorological Office reported this week that April of 2015 was the sunniest in history across the UK, surpassing a record set in 1942.  Some communities in the UK reported double the normal hours of sunshine during the month of April.

The GLOBE Program (co-sponsored through NOAA, NASA, and NSF) has a classroom curriculum built around vegetation green-up and green-down cycles associated with seasonality and climate.  It is available online and can be adapted for classroom use.  You can find it at "global-patterns-green-and green-down."

MPR listener question:

With the recent 50th Anniversary of the terrible Twin Cities tornado outbreak of May 6, 1965, my husband and I wondered if 1965 was a year with high tornado frequency across the region.  Was that the case?


According to the NOAA Storm Prediction Center in Norman, OK, 1965 brought 30 tornadoes to Minnesota (897 to the nation), a low number in the modern context because since 1991 we have averaged 45 tornadoes per year in the state.  However for early climatology of tornadoes (since (1950), 1965 with a total of 30 set a new record number for Minnesota, later surpassed in the same decade by 34 tornadoes in 1968.  Over the last ten years, the year to year variation in Minnesota tornado numbers has been very large, with a peak number of 113 recorded in 2010, and just 15 in 2013.

Twin Cities Almanac for May 8th:

Twin Cities Almanac for May 8th:

The average MSP high temperature for this date is 65 degrees F (plus or minus 11 degrees F standard deviation), while the average low is 45 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for May 8th:

MSP weather records for this date include: highest daily maximum temperature of 90 degrees F in 1874; lowest daily maximum temperature of 41 degrees F in 1924: lowest daily minimum temperature is 28 degrees F in 1960; highest daily minimum temperature of 67 F in 1896; record precipitation of 1.73 inches 1872; and record snowfall is 0.5 inches in 1923.

Average dew point for May 8th is 38 degrees F, with a maximum of 67 degrees F in 1965 and a minimum of 6 degrees F in 1947.

All-time state records for May 8th:

The state record high temperature for this date is 102 degrees F at Beardsley (Big Stone County) in 1934. The state record low temperature for this date is 10 degrees F at Pine River (Cass County) in 1907.  State record precipitation for this date is 4.85 inches at Santiago (Sherburne County) in 2014; and the state record snowfall for this date is 12.0 inches at Windom (Cottonwood County) in 1938.

Past Weather Features:

The first week of May in 1907 brought cold weather, along with snow.  Many observers reported overnight low temperatures in the teens, with daytime highs in the 40s F.  On May 8, 1907 at least 15 northern communities saw the thermometer fall to just 20F or colder.  Frost and snow returned later in May pushing back the planting season for farmers all the way to the last week of May and first week of June.

By far the warmest May 8th in state history occurred during the Heat Wave of May 6-9, 1934.  Over 20 Minnesota communities reported daytime highs of 90F or greater, and three stations (Milan, Beardsley, and Artichoke Lake) reached the century mark on the thermometer.  The cool spot in the state was Grand Marais with a high of only 48F along the Lake Superior water front.

Widespread snowfall with cold temperatures prevailed over May 7-9, 1938.  Seventeen climate stations from Grand Meadow in the south to Bemidji in the north, reported measurable snowfall amounts.  Windom (Cottonwood County) reported a record amount of snowfall for May with 12 inches falling on May 8th.

May 8, 1993 was the wettest in Minnesota history.  Over 20 climate stations reported rainfall over 1.50 inches, and six reported rainfall over 3 inches, mostly in southwestern Minnesota.  The rainfall over May 7-10 was remarkable for many areas, as it rained significantly and heavily each day.  Many western communities reported over 4 inches, while Gaylord, Tyler, and Pipestone reported over 5 inches.  The rains produced many flooded fields across the agricultural landscape.


Mostly sunny and dry Saturday with near normal temperatures.  Increasing cloudiness and wind on Sunday with a chance for showers and thunderstorms.  Chance for showers will carry over into Monday and Tuesday as well, with cooler temperatures prevailing.  Slight chance of snow showers in far northern counties.  Warmer towards the end of next week.



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