Drought Continues to Worsen

Drought Continues to Worsen:

Temperatures continue to run warmer than normal so far this month, typically ranging from 2 to 4 degrees F above normal in most places. Though rainfall has been significant in some areas, many parts of the state geography have seen little or only sparce rains. Drought in Central Counties, North-Central Counties, and Northeastern Counties has worsened. According to the recent update from the State Drought Task Force “the Mississippi River Headwaters watershed, the Rainy River watershed and the Red River watershed are experiencing extreme to exceptional drought that necessitates further restrictions on water use to protect drinking water supplies.” In those watersheds more conservation measures will be mandated or encouraged by the DNR for public water suppliers and for irrigators who use surface waters as a source.

A look at year-to-date (January 1 to August 18) precipitation on a statewide basis shows the average amount of precipitation for the year 2021 so far is under 12 inches. This is an exceptionally low number in a historical context. Some areas of the state have reported year-to-date precipitation deficits that are 9-12 inches below normal (only about half of average). Even if we accept the probability that more rainfall will occur before the end of this month, the total precipitation deficit across the state for the first 8 months of the year, will rival some of the driest years in state history…..like those of 1910, 1929, 1934, 1936, 1976, and even likely be lower than 1988.

Of the 7 seasonal outlook models used by the NOAA-CPC-NNME system, only one (GFDL-SPEAR), favors above normal precipitation in Minnesota for the Sep-Nov period, while four of the remaining six outlook models favor below normal precipitation for Minnesota over the same time period......not a good sign. In addition, all seven models favor continued above normal temperature pattern for Minnesota through November. From my perspective it is beginning to look more probable that this drought will linger into 2022, matching up better with the duration of the 1988 drought, rather than the 1976 or 2012 droughts in Minnesota.

New Season Outlook Models from NOAA:

The NOAA-Climate Prediction Center released some new seasonal outlook models on Thursday this week. The outlook for September to November favors above normal temperatures, while also favoring below normal precipitation at least for the western half of the state. The CPC official Drought Outlook released on August 19th this week suggests that the present drought will persist at least through November 30th. Looking at this outlook suggests that soil freezing dates may be pushed back later this year, allowing the soil a longer period of time to absorb autumn precipitation and be recharged to a higher degree. Hopefully this will happen and provide our soils with some recharge, but it is not likely enough to break the grip of the drought.

Weekly Weather Potpourri:

Tropical Grace moved across the Yucatan Peninsula this week and was expected to pass into Mexico over Veracruz this weekend. It has the potential to bring 10-15 inches of rainfall along with very strong winds according to the NOAA National Hurricane Center.


With the continuing drought in the Western USA, the BBC reports that “for the first time ever, the US government has declared a water shortage on the Colorado River, a life source to millions in the southwest.” Lake Mead behind the Hoover Dam is at its lowest level since it was formed in the 1930s. Water supplies will be cut by the federal government as Lake Mead is projected to only be at 34 percent capacity by the end of the year.


CNN reported this week on a rare heavy rainfall that occurred over the Greenland Ice Sheet. Nearly 100 percent of the time the precipitation that occurs along the top of the Ice Sheet (at roughly two miles above sea level) is snow. But in this case it was rain which rapidly melted the ice and ran off. This indeed is another indicator of accelerated climate change patterns going on at higher latitude positions in the Northern Hemisphere.


This week’s AGU-EOS Bulletin features an interesting article about the effects of wildfires on municipal water supplies, something that few people think about. It is critical to better understand this in western USA landscapes where surface transport and storage of water is relatively more important. “Climate change is driving an increase in catastrophic wildfires; consumers see, smell, and taste the effects in their water. Water utilities must prepare for worse times ahead.”

MPR listener question:

You have spoken many times about how dew points above 60°F can make the outside air temperature in the summer feel warmer (e.g. produce a Heat Index Value that is greater than the air temperature). And this is especially true when the summertime dew points go above 70°F. But what about low dew points and their effect on making the temperature outside feel cooler?

Answer:

This is difficult because the relationship between air temperature and dew point temperature in terms of the change in Heat Index Value is a non-linear one. But in general terms for our climate, when the summer dew point temperature is 55°F or less it makes the outside air temperature feel cooler by a few degrees. In fact when the dew point is 45°F or lower it can make the outside air temperature fee several degrees cooler and even give you a chill when you come out of the water from a swimming pool or lake.

Twin Cities Almanac for August 20th:

The average MSP high temperature for this date is 80 degrees F (plus or minus 7 degrees F standard deviation), while the average low is 62 degrees F (plus or minus 6 degrees F standard deviation).

MSP Local Records for August 20th:

MSP records for this date: highest daily maximum temperature of 97 degrees F in 1972; lowest daily maximum temperature of 62 degrees F in 1966; lowest daily minimum temperature of 40 degrees F in 1950; highest daily minimum temperature of 74 degrees F in 2010; record precipitation of 2.23 inches in 1891. No snowfall has occurred on this date.

Average dew point for August 20th is 58°F; the maximum dew point on this date is 78°F in 1959; and the minimum dew point on this date is 28 degrees F in 2004.

All-time state records for August 20th:

The state record high temperature for this date is 105 degrees F at Campbell (Wilkin County) in 1976. The state record low temperature for this date is 25 degrees F at Alborn (St Louis County) in 1934. The state record precipitation for this date is 8.00 inches at Worthington (Nobles County) in 1913. No snowfall on this date.

Past Weather Features:

In the midst of the Drought of 1934 August 20th brought a chilly morning to many parts of northern Minnesota, where widespread frosts were reported. In fact, climate observers in Koochiching and St Louis Counties reported morning low temperatures in the mid to upper 20s F. At Big Falls, after starting out the day at 28°F the afternoon high temperature climbed to 73°F, a 45°F rise.

In the midst of the 1976 Drought, August 19-24 brought a Heat Wave to Minnesota. Temperatures on August 20th soared into the 90s F across most of the state, while in 10 western and northern counties the afternoon temperatures exceeded 100°F. The cool spot in the state was Grand Marais with a reading of 80°F.

August 18-20, 2007 brought some of the worst flash flooding ever witnessed in the state, especially to southeastern Minnesota, where rainfall totals of 10 to 17 inches were reported. There were widespread mudslides and road closures. Whitewater State Park had to be closed, while the city of Rushford had to use boats to get around its downtown.

Outlook:

Much cooler over the weekend as temperatures fall below normal. Increasing cloudiness later on Sunday with a chance for widely scattered showers and thunderstorms. Temperatures will warm closer to normal for Monday through Wednesday of next week with chances for widely scattered showers and thunderstorms each day.