Climate Watch

Nome Airport has already reported thunderstorms on two days since late May, the first since the summer of 2015. Since weather and climate observations began in Nome, thunder has been reported on a total of 67 days. There has been nearly twice as many days with thunder in the past 30 years as the previous 80 years put together. With the Weather Bureau and then the National Weather Service taking observations from 1930 until 2016, and observations 24 hours a day since World War II, it’s likely that the increase in thunderstorms is real. But what about when thunderstorms happen during the course of the summer? As unusual as thunderstorms are in Nome, it seems even more unusual to have two days with thunder (and even more inland) before summer solstice. When we group the occurrences of all thunderstorms by date, it turns out that thunder increases in frequency during June and early July to a strong peak in the second half of July. Thereafter, thunder is very infrequent anytime August or September. All of this makes good climate sense. Warm air near the ground and moisture in the atmosphere are the two obvious ingredients to help create thunderstorms. The unseen but critical ingredient is that the temperature in the mid-levels of the atmosphere, say, between two and five miles up, needs to decrease rapidly for thunderstorms to form and persist.

All three of these pieces have the best chance of coming together over the Seward Peninsula in July. By August, heating from the sun is declining fast and large-scale Bering Sea storms become more common, and the middle levels of the atmosphere typically reach the warmest levels of the year, which decreases the spread in temperature. Overall, while there are no guarantees, it would not be at all surprising if another thunderstorm or two is in the cards for Nome for later this summer.