Welcome rains arrive:After starting the month with 8 consecutive dry days, interspersed with some record-setting high daily temperatures (90s F in many areas), and low relative humidity (7-15 percent range) some widespread welcome rains blanketed the state this week. Total amounts were generally less than an inch in many northern and central counties, but many southern Minnesota observers reported over 2 inches, including Pipestone, Worthington, Albert Lea, Fairmont, New Ulm, St James, and Caledonia. A handful of observers reported over three inches for the week including Windom, Lakefield, and Sherburn (3.93”).
Prior to these rains there were 58 new daily high temperature records broken or tied around the state over May 6th and 7th. Some of these included:
May 6th: 90°F at Moose Lake; 91°F at Grand Rapids and Red Lake Falls; 92°F at Duluth, MSP, and Redwood Falls; 93°F at Milan.
May 7th: 90°F at Brainerd and St Peter; 91°F at Waseca, Gaylord, Morris, and Sandy Lake Dam; 92°F at Forest Lake, Browns Valley, and Lake Wilson; 93°F at Madison; and 94F at Marshall.
In addition many areas of the state reported relative humidity readings ranging from just 7 to 19 percent, a condition that provoked a "Red Flag" Warning by the National Weather Service and a warning of high fire danger.
A couple of other weather features that were unusual over the May 6 to 7 period: smoke from northern Minnesota fires was carried on northwesterly winds into the Twin Cities Metro Area Friday night and into Saturday morning causing an air quality advisory to be issued. Many residents closed their windows to keep out the smell of burning wood. The cold front that brought the smoke also brought much cooler air across the state. Temperatures fell from the 90s F to the upper 30s F and low 40s F at places like Duluth, Wolf Ridge, Ely, and Floodwood. At Lake Kabetogama the temperature fell from 85°F to 30°F producing widespread frost in the area; while at Duluth the temperature fell from 92°F to the low 40s F with snow flurries!
First balloon meteorological observations:This past Monday (May 9th) marked the 154th anniversary of the famous balloon ascents of British scientists James Glaisher and Henry Coxwell. They made 18 ascents in a gas filled balloon, the first of which was on May 9, 1862. They were the first to carry meteorological instruments aloft to make measurements of the character of the atmosphere. They established that nocturnal inversions were common and that lapse rate (change in temperature with altitude) can vary dramatically. They read their instruments on night ascents by wearing miner's lamps (the balloon was filled with highly combustible hydrogen!). In one famous ascent to an altitude of 30,000 ft, Glaisher lost consciousness and Coxwell, who was groggy and had numb, frozen hands, still found a way to pull the valve-cord hard enough with his teeth so that enough gas was released to allow them to descend back to Earth.
Weekly weather potpourri:If you are interested in the network of State Climatologists across the USA, NOAA has provided a web site to find them and their contact information. The American Association of State Climatologists (AASC) will have their annual meeting in Sante Fe, NM starting on June 28th next month. This organization provides data and pragmatic climate services to every state in the USA.
A study this week from the Geophysical Research Letters explains why the 2015-2016 El Nino in the equatorial Pacific Ocean was so strong and long-lived. It was connected to sea surface temperature behavior in the Central Pacific Ocean as well.
According to NOAA-NCEP Alaska has started the year 2016 with the warmest ever January through April period, averaging over 11°F above normal. So far this year over 550 new daily high temperature records have been tied or broken within the Alaska climate network. In the month of April alone 17 days brought new record high temperatures to Anchorage.
MPR Listener Question:Last year at least 24 dates brought significant hail to some parts of Minnesota. When is the peak of the hail season in our state and how many dates per year bring hail?
Answer:The date with the highest frequency of hail varies around the state, but in general historical data show the peak period for hail to occur is the last week of May and first full week of June for most locations in the state. Overall on a statewide basis there are typically 10-20 dates with reports of hail each year, with 3-7 dates showing reports of large hail (three quarters inch diameter or larger). Observers around Mora, MN reported 1 inch diameter hail earlier this month on May 6th.
Twin Cities Almanac for May 13th:The average MSP high temperature for this date is 69 degrees F (plus or minus 11 degrees F standard deviation), while the average low is 48 degrees F (plus or minus 8 degrees F standard deviation).
MSP Local Records for May 13th:
MSP weather records for this date include: highest daily maximum temperature of 94 degrees F in 2001; lowest daily maximum temperature of 39 degrees F in 1907: lowest daily minimum temperature is 31 degrees F in 1907 and 1980; highest daily minimum temperature of 70 degrees F in 2001; record precipitation of 1.95 inches in 1911; and record snowfall is a trace in 1902 and 1935.
Average dew point for May 13th is 44 degrees F, with a maximum of 70 degrees F in 1998 and a minimum of 20 degrees F in 2011.
All-time state records for May 13th:The state record high temperature for this date is 95 degrees F at Beardsley (Big Stone County) in 1894, at Rothsay (Wilkin County) in 1977, and at Granite Falls in 2007. The state record low temperature for this date is 10 degrees F at Tower (St Louis County) in 1997. State record precipitation for this date is 4.63 inches at St Francis (Anoka County) in 1999; and record snowfall is 3.0 inches at Argyle (Marshall County) in 1924.
Past Weather Features:Snow fall across portions of the Red River Valley and north-central Minnesota over May 12-14, 1907 bringing a halt to planting of small grains and potatoes. The snow was short lived as temperatures soon warmed into the 50s and 60s F.
Widespread hard frost on May 13, 1918 caused many farmers to have to replant crops. Temperatures fell into the teens and twenties F from the Iowa border north to Canada. At some locations the daytime temperature never rose out of the 40s F.
On a statewide basis perhaps 1977 brought the hottest May 13th in history with over 25 communities reporting afternoon temperatures in the 90s F. It reached 90°F as far north as Walker, Thorhult, and Hibbing. May of 1977 was the warmest in state history, so there were many more days of 90°F temperatures.
Over May 11-13, 1997 a cold front brought snowfall to many parts of the state. Observers in northeastern Minnesota reported up to 3.5 inches of snow. This was followed by February-like temperatures with lows in the teens and twenties F. On May 13th Tower reported a high of 35°F and a low of just 10°F.