Early this Wednesday morning conditions were just favorable enough to warrant keeping an eye out for potential waterspouts across the Great Lakes, and some either formed, or tried their very best. The waterspouts that did end up popping were mainly across Lake Erie, and some did yesterday too.
One even tried forming over Lake Ontario this morning near Oswego, NY, but only a tiny funnel cloud ended up showing its face instead.
The potential for any waterspout development has decreased since this morning as the temperature difference between the lake and the air above it has decreased with the heating of the day, but there is still a slight chance this evening as temperatures aloft become just cool enough, and a possible lake breeze boundary tries its best to produce some sort of noteworthy convection along the lakeshore. The chance is small, but it’s there.
So what exactly is a waterspout?
NOAA defines a waterspout as “a funnel which contains an intense vortex, sometimes destructive, of small horizontal extent and which occurs over a body of water.” To put it simply, they are essentially known as “tornadoes over water.” There are two types of waterspouts, and which one you get depends on how they form and the environment they’re in.
- Fair Weather
Tornadic waterspouts are produced by supercell thunderstorms, or storms that rotate. These types of spouts are much more uncommon over the Great Lakes as 5% of storms that occur actually end up rotating enough to form them. When they do form, they come from the base of the thunderstorm when the source of rotation extends down to the surface of the water. These waterspouts can be very destructive and long lived due to the nature of the storm it’s associated with.
Fair weather waterspouts are the most common type as they happen in seemingly, “fair weather” conditions. All you need are just the right ingredients in place, and they don’t even require a strong, rotating, parent thunderstorm for them to occur.
These differ from tornadic waterspouts in that they form from the surface upward, as the associated growing cumulus cloud produces enough upward motion to essentially stretch the water into a spinning funnel. These spouts are typically weaker than their counterparts, but they are still dangerous to boaters and other small craft. These water twisters are known to produce winds up to 60 knots (70 mph), and are a hazard to those over water.
What environmental conditions do we look for?
When looking at the formation of fair weather waterspouts, the conditions needed to produce them are heavily driven by temperature differences between the warm, moist water and the drier, cooler air above. A temperature difference of around 12°C or greater up to 5,000 feet in the air, which is right around 850 millibars, is enough to warrant strong updrafts. Meteorologists use 850 millibar temperatures to determine whether the temperatures aloft will be great enough to produce one of these water twisters.
Having enough low level convergence and lift from an existing front, or lake breeze boundary is also crucial and helps the updraft to stretch and spin to form your water funnel. When enough spin gets pulled into the updraft, the already present upward motion further strengthens the vorticity, or spin within the system as it gets pulled in and upward even more.
Analogy: Think of a figure skater that’s spinning on their skate. As the skater begins to pull its arms inward it causes them to spin even faster thanks to the laws of physics. One they gain enough momentum and spin they increase that spin even more, and this is what helps skaters hold their signature spin move for so long!
Forecasting for waterspouts remains an intricate process, but we do know that the most common time for waterspouts to occur begins… right now!
Sitting in the month of August, we are right around the peak for both the warmest air and warmest lake temperatures. As soon as we escape August the lake stays warm due to the process of specific heat, and the air gets cooler as we transition from summer to fall. As the cooler air moves over the warm lake, that is when you get temperature differences enough to produce waterspouts.
Waterspouts generally do better without a large amount of wind in both speed and differing direction, as well as cold air near the surface that would tear away the instability.
The information above can be found at: https://www.lakeeriewx.com/CaseStudies/WaterspoutPrediction/Waterspouts.html
Have any cool pictures of waterspouts you want to share? Send them my way or tag me on social media!