Early June 2020 heat wave compared to past years
The heat is on and the forecast into the weekend is not very promising. Many times, the first thing that comes to mind is a comparison to previous events/years. While this pleases our way of thinking, every event is different. From the period of May 30 to June 15, the warmest five day periods (what we are using as a definition of heat wave) occurred in 1952, 1953, and 2011. June monthly average temperatures range in the 70s across the state (Figure 1). Of the previously mentioned three years, great attention is paid to 2011, one of the worst droughts in recent memory. Average temperatures for the month were up to six degrees warmer than average (Figure 2). June 1953 takes the cake however with some monthly departures over eight degrees (Figure 3).
Figure 1. County based temperature averages for June via the Weather Data Library (climate.ksu.edu/temp/county).
Figure 2. County based temperature anomalies for June 2011 via the Weather Data Library (climate.ksu.edu/temp/county).
Figure 3. County based temperature anomalies for June 1953 via the Weather Data Library (climate.ksu.edu/temp/county).
When considering previous starts to June, thus far in 2020, there have been only been three stations which have set their warmest start (out of about 160 weather stations in the state). This is tied for 10th most with a few other years. 1953 holds the record with 63 stations holding their warmest heat wave for early June. Many of these averaged a heat wave (five or more days) with high temperatures above 100! The year 2011 had 25 weather stations holding their warmest start to the month for second most. During that heat wave to start June 2011, average maximum temperatures during the five-day period were 98 or higher.
Note: the forecast calls for persistent 90s to 100s through early next week (June 7-8, 2020). If that holds true, 2020 will move up in the ranks quickly as one of the hottest heat waves to start June on record.
Preceding drought conditions
Drought exists across much of the west, especially the southwest. Substantial impacts have been observed to winter crops, especially wheat. Dry soils tend to develop negative feedback effects to the atmosphere. They can warm up much faster than wet soils, lack moisture to help develop thunderstorms, and can become hydrophobic - preventing water penetration and soil saturation during a rain event. Despite dry conditions thus far in 2020, it was much drier to start the year in 2011. Precipitation over a wider area was observed in 2020 for east and central Kansas. Therefore, only western parts of the state reside in extreme drought thus far in 2020.
Figure 4. Drought conditions to begin June 2020 compared to that of 2011 (droughtmonitor.unl.edu).
Looking Forward
While conditions haven’t been as bad this year as in 2011 (yet), the forecast for warm and dry conditions persisting into mid-month is concerning. A brief pattern change is forecasted around June 10 which should provide a brief reprieve from the hot weather. Some precipitation is possible during that period with highest confidence in the eastern part of the state. Some cooler-than-normal temperatures are also possible - once again though, only the east. Shortly after the pattern break, forecast models are hinting at a return of the large area of high pressure across the south-central portions of the US. That suggests a return of the hot/dry conditions for the last week (Figure 5). Overall the entire month is forecasted for a high probability of below normal precipitation and warmer than normal temperatures for the entire state.
Figure 5. Climate Prediction Center probability for temperature anomalies (left) and precipitation anomalies (right) for June 12-19th 2020 (www.cpc.ncep.noaa.gov).
Precipitation deficits in the west are accumulating fast and spreading east each day without widespread moisture. June is one of the wettest months, averaging between 2.7 – 5.8 inches statewide. Should we see the below-normal precipitation forecasted, it will become very difficult for much of the southwest to recover this year to its normal amounts - requiring a significant wet pattern. Unfortunately, the early precipitation deficits have already taken their toll, ruining some wheat crops and making early establishment of summer dryland crops very difficult. Other trickle down impacts will consist of increased irrigation and more difficulty in reaching water conservation goals across the region, as well as some water supply concerns. In the eastern third of the state, rapid drying would have its own problems, as summer crops planted into saturated soils may not have developed sufficient roots to follow the retreating soil moisture.
Figure 6. Averaged precipitation by county for the month of June (climate.ksu.edu/precip/county).
Are you impacted?
As conditions rapidly change due to wet/dry conditions, we are always looking for in-field reports. Whether it is flooding, dry grass, dry rivers, or agricultural impacts, we want to hear about them! Please don’t hesitate to email us about it. Contact information is listed below. These reports help us provide input into such things as the drought monitor and other resources.
Summary
- Current early June heat wave is uncommon but not unprecedented (yet).
- Preceding drought conditions to the current heat wave differ spatially and in intensity compared to 2011.
- Should dry/hot conditions persist beyond early next week (around June 7), 2020 will rapidly climb the charts for the longest/hottest heat wave to start June.
- The current weather has little implication for the remainder of the summer but growing precipitation deficits will make it difficult to overcome drought in the west.
Christopher “Chip” Redmond - Weather Data Library Manager
christopherredmond@ksu.edu
Mary Knapp - Assistant State Climatologist
mknapp@ksu.edu