June is here! That means the start of meteorological/climo summer. What that means for our area...
Before looking ahead to June, we take a quick look back at May's rainfall stats for the area by looking at measurements from the Northwest Alabama Regional Airport in Muscle Shoals. That is our area's primary NWS climate reporting station. We saw 3.64" of rain officially measured at the airport in May, putting us just shy of an inch below average for the month. Despite being 4.35" above normal in rainfall for the year so far, the Tennessee Valley has been drier than usual for the past few weeks, but recent rains have definitely helped out a good deal in that regard.
June has arrived, and we now look ahead to a new month and what that expects in terms of weather across the Tennessee Valley. June is also the start of meteorological and climatological summer. This simply means that, in order to make things more simple, official weather records for the "summer" start at the beginning of the month since astronomical (official) summer can vary by a couple of days on the date on which it falls. Our average high for the month is 88 degrees, but that starts around 85 at the beginning of the month, and we are averaging 90 degrees as we wrap up June and head into July. We can definitely get very hot this time of year though. The record monthly high for our area is 108 degrees, set in 1914. While cool spells happen much less frequently, our monthly record low is 42 degrees! That record was set back in 1894.
June can often be a somewhat wet month across the Tennessee Valley as we still have occasional cool fronts bring showers and thunderstorms, we can occasionally get a tropical depression or tropical storm in the Gulf, and June and early July are the heart of "thunderstorm complex season" here in the Tennessee Valley. Our average rainfall amount for the month comes in at 4.76 inches.
The good news is that the tornado season backs off a great deal as we head into June and the summer months overall. The jet stream does its annual shift northward into the northern states, and this means that setups with favorable wind shear for significant tornado events shift northward as well. Tornadoes can and DO still happen this time of year though, but they are most often either small, spin-up tornadoes within lines of storms or as storms merge with each other, or they are found in the outer rain bands of landfalling tropical systems either. Those are usually the smaller, short-lived variety as well, but not always. Most tornadoes from tropical systems are in the EF0-EF1 range, but EF2 and even the occasional EF3 intensity tornado from a tropical system happen frequently enough that the idea is an important thing to consider. While tornado threats in our area this time of year are infrequent and usually lower end, there can occasionally still be a supercell event and the rare significant (EF2+) tornado in our area in June. 2018 and 1994 are two good examples. A supercell produced an EF2 tornado in northwestern Cullman County, AL in June 2018; and a somewhat unusual late-season tornado outbreak in late June 1994 produced long-tracked supercells with multiple F3 tornadoes across southern middle Tennessee and north Alabama, including Wayne County in Tennessee and Lauderdale and Limestone Counties in Alabama. Those events show that we must ALWAYS be prepared for severe weather threats in our area, but tornado threats of that magnitude this time of year are very rare.
Our primary severe weather in June comes in two primary forms: short-lived pop-up "pulse" thunderstorms that produce hail or damaging straight-line downburst and microburst wind gusts... and lines or complexes of thunderstorms that produce widespread damaging straight-line winds. Our friend Jason Simpson, former WHNT chief meteorologist, said it best on social media earlier this morning... these storms can be some of the worst weather you will experience all year, with intense wind gusts, torrential rain, and enough lightning to make you think Marvel is filming a Thor movie in your neighborhood!
As we shift into June, our attention also shifts to the tropics. June 1st is the official start of the Atlantic hurricane season that runs through the end of November. Tropical storm formation in June is most likely to happen in the Gulf of Mexico, northwest Caribbean, or immediately off the East Coast of the United States. This often means that when these systems do form, they are landfall threats. However, because of wind shear usually still being a bit strong this early in the season, tropical systems in June usually aren't that intense. They are usually more in the way of rain-makers than intense wind producers. However, an occasional hurricane can happen in June, and climatologically speaking, those would typically be most likely in the eastern Gulf of Mexico.
The Tennessee Valley does have to pay attention to the tropics as well. We are well removed from the coast; so, we don't have to worry about the intense eyewall wind damage or storm surge from systems, but we see our fair share of weather threats from these systems as well. Flooding rains, gusty to damaging winds, and spin-up tornadoes are all threats we sometimes face in the Tennessee Valley when tropical storms and hurricanes make landfall along the Gulf Coast to our south and southwest.