The severe weather season is well underway – or at least climatologically speaking. In terms of tornadoes, April features an average of 187 tornadoes (based on 1997-2016 data), making it the third most active month of the year. That’s followed by 215 in June and 275 in May, which is the most active month of the year for severe weather in general.
There have still been tornadoes this year, however they haven’t happened in the usual areas. This includes several tornadoes as far west as California and as far north as Pennsylvania. According to the Storm Prediction Center, there have been a total of 259 preliminary tornadoes based on storm reports so far this year, well below the year-to-date average of 402. The main reason for this deficit is the somewhat unfavorable pattern for tornadoes. A trough has dominated over the Eastern US while a ridge has remained in place over the Western US. This trough has allowed for near-average severe weather reports in the Southeast. In order for severe weather to occur in the climatologically-favored areas, you want a digging trough coming in from the West. Typically, as we transition from winter to eventually summer, the highest risk for severe weather shifts from the Southeast to the Southern Plains and eventually to the Central and Northern Plains.
What’s most remarkable about this tornado deficit is the fact that there haven’t been any tornadoes reported in either Oklahoma or Kansas, two of the most notorious states for severe weather, especially in the spring. Oklahoma typically averages 12 tornadoes in the month of April, however with none so far this month the state is currently far below this count. If no tornadoes occur in the state past April 26th, which is likely to occur, it would break the current record for the latest start to the tornado season set back in 1962. There has also never been a year where no tornadoes have been reported in Oklahoma from the January through April time period. Similarly to Oklahoma, Kansas typically averages 12 tornadoes in the month of April, but again there have been none so far. However, this will not break any records, unless none occur in early-May as well.
Tornadoes aren’t the only severe weather risk that has been below average. Hail and wind reports have also been down this year compared to the past. There have been 665 reports of hail so far this year, compared to the 2005-15 average of 1400. That is over 700 hail reports below average. In addition, 1274 wind reports have been recorded in 2018 as of April 22nd, which is below the year-to-date average of 1842, according to the Storm Prediction Center. Let’s hope this severe weather season remains on the quiet side, but the odds are not in our favor as May tends to feature some nasty storms.