More heavy rain and flooding:Thunderstorms, some severe, brought heavy rainfall again to portions of central and southern Minnesota over September 21-22 (Wed-Thu) this week. Many observers reported from 1 to 2 inches, and several places reported new record daily amounts up to 5 to 8 inches. Dew points spiked in the low 70s F at a number of locations just ahead of the storm indicating that there was a very high water vapor content. Preliminary data suggest that a new statewide record daily rainfall occurred on September 22nd (old record 4.84 inches at Cambridge in 1968), but the final say on the new record will come from the Minnesota State Climatology Office. Many communities reported flash flooding, including washed out roads and culverts, and some flooded basements.
Some of the new record daily amounts of rainfall included:
7.64" at Waseca
5.15" at Wells
4.11" at Rochester
4.06" at Bricelyn
3.81" at Preston
3.74" at Spring Grove
3.70" at Zumbrota, Grand Meadow, and Spring Valley
3.09" at Winnebago
3.08" at Theilman
2.75" at La Crescent
2.15" at Stillwater
2.10" at Winona Dam
2.06" at Kimball
Many other communities with shorter climate records reported even greater amounts of rainfall, including 5.34" at Lanesboro, 5.11" at Eau Claire, WI; 4.65" at Champlin; 4.15" at Owatonna; 8.11" at Maple Grove; and 5.12" at Byron.
The added rainfall this week pushed the total for the month of September to near record or new record values for a number of climate stations in southern Minnesota, including:
13.69" at Mabel (Fillmore County)
13.89" at Spring Grove (Houston County)
10.37" at Spring Valley (Fillmore County) 10.56” at Rushford (Fillmore County)
11.40" at Hokah (Houston County)
13.03" at Caledonia (Houston County)
14.56" at Waseca (Waseca County)
This wet September continues a trend toward above normal precipitation. Some climate stations in Minnesota have already received over 40 inches of precipitation for the year. Further at least ten climate stations are on a pace to set a new record wet year, including St James with 40.59 inches (2nd wettest year in history), and Waseca with 48.68 inches (2nd wettest year in history), and over three months to go in 2016! It is also likely that the all-time state record wettest single year, 53.52 inches at St Francis (Anoka County) in 1991 will be broken before the end of this year.
Weekly Weather Potpourri:Earlier this week NOAA scientists reported that the Northwest Passage was ice-free again at the end of the summer, allowing for ship traffic to pass from the North Pacific to the North Atlantic passing through Arctic Canada. For the first time a luxury cruise ship, Crystal Serenity, was making the journey this autumn from Alaska to New York City via the Northwest Passage.
The U.S. Climate Resilience Toolkit, available online, now has a procedure to help communities assess their vulnerabilities to climate change, and select from optional strategies to make themselves more resilient. Even local schools and businesses might want to consider looking at this toolkit.
The United Kingdom Met Office announced this week that for the second consecutive year they will consult the public to name storms during the coming winter season. This will apply only to storms which bring a serious threat of precipitation or strong winds. They have found that weather warnings are better received by the public if the storms are given names.
The World Meteorological Organization published for the first time this week a study of lightning around the world. Two of the extreme events which they noted were the longest stroke of lightning every detected, nearly 200 miles across the sky of Oklahoma in 2007; and the longest continuous flash of lightning, 7.74 seconds which occurred over southern France in 2012.
MPR listener question:It has certainly been a turbulent month of September. The tornado reported at Camp Ripley in central Minnesota on September 7th, made some of us wonder how often do tornadoes visit Minnesota during the month of September? It seems pretty rare.
Answer:Indeed, historically less than 5 percent of our annual tornadoes in Minnesota occur during the month of September. In 1894 8 tornadoes were reported during September, and more recently in 2005 6 tornadoes were reported during September. In 2012 there were 4 tornadoes reported as late as November 10th, exceptionally rare for our climate. In Minnesota history there have been no tornadoes reported in the months of December, January, and February.
Twin Cities Almanac for September 23rd:The average MSP high temperature for this date is 69 degrees F (plus or minus 10 degrees F standard deviation), while the average low is 49 degrees F (plus or minus 8 degrees F standard deviation).
MSP Local Records for September 23rd:
MSP weather records for this date include: highest daily maximum temperature of 90 degrees F in 1891 and 1937; lowest daily maximum temperature of 46 degrees F in 1965; lowest daily minimum temperature is 30 degrees F in 1983; highest daily minimum temperature of 71 degrees F in 1930; record precipitation of 1.98 inches in 2010; and a trace of snow fell on this date in 1928.
Average dew point for September 23rd is 43 degrees F, with a maximum of 73 degrees F in 1945 and a minimum of 20 degrees F in 1928.
All-time state records for September 23rd:The state record high temperature for this date is 99 degrees F at Granite Falls (Chippewa County) in 1892. The state record low temperature for this date is 14 degrees F at Goodridge (Pennington County) in 2012. State record precipitation for this date is 9.48 inches at Amboy (Blue Earth County) in 2010; and record snowfall is 2.0 inches at Bigfork (Itasca County) in 1942.
Past Weather Features:A short-lived Heat Wave brought temperatures of 90 degrees F or higher to many communities around the state on September 23, 1892. Two days later some areas reported frost.
Traces of snow were reported in northern Minnesota on this date in 1985.
Widespread freezing temperatures prevailed around Minnesota on September 23, 1995. Many observers reported morning lows in the 20s F. Tower fell as low as 16 degrees F. As far south as Preston it was 29 degrees F.
Thunderstorms brought widespread flash flooding to portions of southern Minnesota over September 22-23, 2010. Many observers reported all-time rainfall records in the range of 8 to 11 inches. There were widespread reports of flooded highways and basements. The Mississippi River rose above flood stage at St Paul a week later, and exceptionally rare occurrence for the month of September.