A Glimpse at June Wind Climatology
June is historically one of the lighter wind months of the year for Kansas. This is usually a result of the summer high pressure building in, pushing the Jetstream further north. As a result, there are fewer storm systems traversing the state and winds are calmer - even more so later in the summer of July/August. No surprise, regardless of the time of year, western Kansas still averages stronger winds in part to less obstacles than that of central/eastern portions of the state (Figure 1). The average wind speeds for June are 13.8 mph (out of the south) and 11.1 (south) for Dodge City and Emporia, respectively. One point to mention is these are sustained winds averaged over the entire day. Typically, winds are strongest during the day and much lighter overnight - this averages over all of that and does not consider wind gusts.
Figure 1. Average wind speed and direction for Dodge City (upper panel) and Emporia (lower panel) by month (https://mesonet.agron.iastate.edu).
How Strong were the Winds?
Several periods of sustained strong winds were observed in June, especially for western Kansas. Dodge City only saw six days with winds below average (13.8 mph). That means that the remaining observed sustained winds exceeding that through the entire day with gusts (not included) always higher (Figure 2). Of note was the June 6-9 period where sustained winds were observed exceeding 20 mph. That is very impressive and correlates with a very warm period of the month coming to an end with a wind shift associated with a cold front (Figure 2) and one of the only few temperature drops of June afterwards (Figure 3). Winds typically increase out of the south in advance of a cold front and can be quite gusty post-frontal.
Figure 2. Average wind speed and direction by day for June at Dodge City in 2020 (https://mesonet.agron.iastate.edu).
Figure 3. State-wide temperature anomaly from normal for the month of June (mesonet.ksu.edu).
Another period of interest was June 11-18 where the winds averaged over 15 mph each day (Figure 2). This also correlated with another warm period (Figure 3). This was a time of great concern with increasing drought and evaporative surface moisture loss. Hot and dry winds create significant agriculture and water stress as top soil moisture is lost much faster with strong winds. A week of those conditions can rapidly degrade drought conditions. The only exception in the state was north-central where several rain events eased these stresses. Emporia also observed similar winds (above the average of 11.1 mph) during this period (Figure 4) but at a lesser magnitude that those further west. Also of note, winds were much lighter at both Dodge City and Emporia during the brief cool down June 20-25.
Figure 4. Emporia wind speed averages through the month, the historical average is 11.1mph from the south for June (https://mesonet.agron.iastate.edu).
Large Scale Pattern
So, what was the driving factor behind these endless hot/breezy days? As always with meteorology, we need to look above the surface at 500mb (17,000 - 20,000 feet). Upper level winds drive storm systems and the general pattern. During June 2020, we saw a “trough” of low pressure at 500mb over the western US (Figure 5). This places Kansas in southwesterly winds aloft, developing a strong surface pressure gradient between high pressure further east. As a pressure gradient increases across an area, winds increase. This south/southwesterly flow pushes downslope off higher terrain to our southwest. As a result, the air sinks and warms. The area most favorable for these hot winds under this pattern is highlighted as a light pink shaded box in Figure 5.
Figure 5. Upper weather pattern anomaly for June 2020. Low pressure (L) and high pressure (H) are marked accordingly. The black arrow represents the jet stream pattern across the west/central US. The pink arrow is the surface wind pattern. Shaded pink region is an area favorable for hot, dry, windy conditions under this pattern. (Source: Physical Science Laboratory, https://psl.noaa.gov).
The really interesting aspect about these winds is they were surface driven between the pressure differences of the high/low pressure. Many times during strong wind events, winds above the surface are stronger than those close to the surface. During the afternoon, vertical mixing in an unstable atmosphere (typical for the daylight hours) will mix these stronger winds down to the surface. In this case however, the winds with height actually decreased (Figure 6, pink highlighted box). In addition, any surface air that wanted to mix vertically would run into a “cap” (Figure 6, green highlighted box). Most known for its ability to prevent afternoon thunderstorm development, it also prohibits winds at higher altitudes from mixing to the ground.
Figure 6. Atmospheric sounding showing winds with height at Dodge City (7pm) from Storm Prediction Center (www.spc.noaa.gov). Highlighted area shows four to five “flags” representative of 40+ knots of surface winds at the bottom. Note how winds decrease with height.
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 one or both of us about it. These reports help us provide input into such things as the drought monitor, etc.
Christopher “Chip” Redmond - Weather Data Library Manager
Mary Knapp - Assistant State Climatologist