Update on drought conditions and the 3-month fall outlook
The most recent week saw the rainfall shift to the central portions of the state. The Central Division had the greatest surplus, with an average of 1.33 inches or a surplus of 0.47 inches. That translates to 156 percent of normal. The Northwest Division averaged just 0.02 inches, which was a deficit of 0.6 inches or 8 percent of normal. The Northeast Division was the only eastern division with below-normal precipitation for the week ending on August 14. The divisional average was 0.38 inches, a deficit of 0.51 inches or 42 percent of normal. The largest weekly total for a NWS COOP station was reported at Ashland, in Clark County, at 3.77 inches.
Figure 1. Departures of weekly precipitation from normal for Kansas during the week of August 8 – August 14, 2018 via Cooperative Observer (COOP), Community Collaborative Rain Hail Snow Network (CoCoRaHS) and Kansas Mesonet.
Temperatures continued to be cooler-than-normal. The statewide average temperature was 76.6 degrees F, which is 1.5 degrees cooler-than-normal. Eastern Kansas continued to be an exception to the cooler-than-normal temperatures. The Northeast and East Central divisions both had above average temperatures. The average temperature in the Northeastern Division was 78.3 degrees F, with a departure of 1.5 degrees. For the East Central Division, the average temperature was 78.7 degrees F, and the departure was 0.6 degrees. The highest maximum temperature was 101 degrees F at Ft. Scott, Bourbon County, on August 8. The lowest minimum temperature was 51 degrees F at Brewster 4W, Sherman, on August 12.
Figure 2. Departures of weekly mean temperatures for Kansas during the week of August 8 – August 14, 2018 via Cooperative Observer (COOP) and Kansas Mesonet.
Continued rainfall in the west resulted in continued improvement in drought conditions in that region. The low precipitation in the east has resulted in continued deterioration and expansion of the extreme drought in the East Central Division. (Figure 3). The change in drought categories map (Figure 4) shows where changes occurred during the week.
Figure 3. Current drought from the Drought Monitor.
Figure 4. Difference in drought categories from August 7 to August 14, 2018 (US Drought Monitor).
The quantitative precipitation forecast for the next 7-day period, ending on August 23 shows the heaviest rainfall will be in southern areas of the state (Figure 5). The areas with heaviest amounts may see as much as three inches of precipitation. Most of the state is expected to see up to an inch. With warmer-than-normal temperatures expected, this would do little to improve drought conditions in areas most severely affected. The 8 to 14-day precipitation outlook (Figure 6) indicates near normal precipitation across much of the state. The temperature outlook favors a pattern of warmer-than-normal temperatures for the period.
Figure 5. Quantitative Precipitation Forecast the 7-day period ending August 23, 2018 (NCEP)
Figure 6. 8-14 day Precipitation Outlook for period ending August 22, 2018 (CPC)
Fall Outlook (September – November)
The Climate Prediction Center has released the Fall Outlook. In general, the outlook has a slightly increased chance of warmer-than-normal temperatures for the period of September through November. That is an average of the 3-month period, so a warm start does not eliminate a cool end to the season, or vice versa. Cooler-than-normal temperatures are expected to remain through the end of August. The Climate Prediction Center’s one-month outlook for September calls for equal chances of above- or below-normal temperatures in Kansas.
Figure 7. Fall temperature outlook (top, CPC); Kansas normal temperatures (bottom, Weather Data Library
Normal highs in the middle of October (middle of the season) range from 67 degrees F at Concordia, to 71 degrees F at Elkhart. Highs in the 80s in September would be below average but those same highs would be warmer-than-normal in October.
The precipitation outlook is less clear. There are equal chances for above- or below-normal precipitation. In western Kansas, that amount ranges from 2.52 to 4.65 inches, while in eastern Kansas, the amount ranges from 6.20 inches to over 13 inches. Below average precipitation would mean little improvement in drought conditions in the east.
Figure 8. Fall precipitation outlook (top, CPC); Kansas normal precipitation (bottom, Weather Data Library)
The El Niño Southern Oscillation (ENSO) has an increased chance of switching to El Niño conditions during the period. El Niño conditions frequently favor higher-than-normal precipitation in the Plains, but delayed onset may result in less impact during the fall.
The warmer-than-normal temperature outlook is driven mainly by decadal patterns. This is the average of the three-month period, and does not eliminate the possibility of colder-than-normal conditions during fall. The precipitation outlook is driven mainly by the sea-surface temperature and constructed analog models. Keep in mind, the skill with both outlook products is weakest with neutral ocean temperatures, and does not account for individual events such as a heavy rainfall event. Warmer-than-normal temperatures would increase the opportunity for late-planted spring crops to mature before the first frost, but could increase the evaporative demand and have flowering/grain-fill occur under less favorable conditions.
Additional information can be found in the latest Agronomy eUpdate at https://webapp.agron.ksu.edu/agr_social/eu.throck or on the Kansas Climate website under weekly maps or drought reports:
http://climate.k-state.edu/maps/weekly and http://climate.k-state.edu/reports/weekly/2018/
Mary Knapp, Weather Data Library
Christopher “Chip” Redmond, Kansas Mesonet Manager