Last night, thunderstorms developed along the Minnesota – Iowa border and lifted north through the Twin Cities. One cell in particular tracked from the south metro to the northeast metro. The cell videoed above was part of the tornadic cell, but was not within the tornado warning.

The cells was ultimately responsible for a smattering of weak tornadoes on the southeast side of the Twin Cities metro, with tree damage in some targeted locations on the storm’s path. Eventually, the storm reached the Minnesota State Fair, going on in Falcon Heights, near St. Paul.

Not only did these storms produce quite a bit of strong wind (as seen above), they dumped a quick burst of rain, that left the Fair submerged.

Another line of storms is poised to roll through the Twin Cities in the next hour or so, and though there are some stronger cells, they are mostly non-severe. Just another quick shot of rain — this time focused on the north metro — and a cooler work week ahead.

We are approaching the end of August, and the peak of hurricane season is a little more than two weeks away, and we haven’t had a named feature since Tropical Storm Colin graced the Georgia coast at the beginning of July. The way it looks, we will make it until at least September until we have our “D” storm, given the current NHC outlook.

Each of those two yellow x’s represent a wave that ultimately could become a named tropical feature, but the NHC outlook suspects that formation chance is merely 20% through the next 5 days, which takes us to the end of the month with a day to spare. If these storms fail to materialize, and nothing else crops up in the intervening days, it would be the first time since 1997 that we went through August without a named storm in the Atlantic basin, and only the 2nd time since 1961. The fact that one of those x’s lies off the coast of Africa suggests that there is little time for another feature to arrive behind it, and a surprise is even less likely than usual.

The long range GFS model is pretty consistent with a tropical feature showing up at the beginning of September, and that wouldn’t really be a surprise. There is no causation of a quiet September simply because there is a quiet August. Colorado State hasn’t revised their predictions for the season yet. A quiet season in 1992 didn’t have a named storm until August — Hurricane Andrew. That 1961 season didn’t have any August storms, but did have two Category 5 hurricanes later in the season.

I haven’t found a season that hadn’t had a hurricane by September, though, and that would certainly be unusual, if not historic. We’ve also had the first season in 8 years without a named storm before the hurricane season officially starts on June 1st. It’s been a slow start, and it continues to remain slow for the coming days. We should appreciate that while it lasts.

The remnants of a weak tropical feature came ashore in Texas over the weekend, noted only in reference to how quiet the Tropics have been this season. This weak, nameless blob was about all that had troubled North America this summer so far. It gathered a lot more attention overnight into this morning by dumping torrents of rain on the Dallas metro, leading to flash flooding throughout the Big D and Fort Worth.

At least 2 inches of rain have fallen in broad swaths of North Texas and up to 8 were estimated in some spots, making city streets waterlogged and impassable in some places. Radar shows that more rain is coming, though fortunately, Fort Worth should be drying out.

Flash flooding is different than river flooding, in that the onset is much more rapid and isn’t necessarily confined to existing waterways. River flooding can be planned a bit better for evacuations and bracing for the impacts of rising rivers, but flash flooding, like the rain in Dallas, can happen with a lot of rain coming in just a few hours, and is not as easy to anticipate.

There are two particular amplifiers of flash flooding. One of them is the increasingly paved surfaces we find in urban areas. Water pools, unable to drain from roadways, and can cause vehicles to hydroplane or even float. If the water is moving, for example if a nearby waterway has spilled out of its banks, or if the inundated roadway slopes, just a few inches of water are enough to move a vehicle. If water is deep enough, it can cause engines to stall.

The worst case scenario for flash flooding is usually found in hilly or mountainous terrain, such as what happened in eastern Kentucky this summer. Rainwater is channeled into valleys, causing existing rivers and creeks to rise quickly, and sweep away mud, trees and edifices in the water’s path downward. Unlike normal river flooding, which arises from water coming downstream after snow melts or a long, wet season, flash flooding happens in an instant as water flows downhill. Some of the deadliest flash flooding instances in the US occurred in Oregon and Colorado.

Heavier rains are a response to slow moving storms with higher dew points, and are possible even when severe weather hasn’t occurred. It’s always important to stay aware of your surroundings, and not pass through standing water, because you never know what lies beneath.