The GOES16 weather satellite is back in action and provides a very detailed look at some cool meteorological features…let’s dive in to what we can see:
1) LAKE EFFECT! Every large lake in the image (even Lake St. Clair) is producing lake effect clouds and snow. Note how cloud cover increases as air moves across the lakes, gradually picking up moisture and heat as it goes. There are several intricacies to lake effect evident here:
a) shoreline convergence and divergence. Note how when clouds hit the western and northern shores of Lake Erie, they actually tend to weaken as they initially hit the water. This is due to winds over water being faster than on land. This causes “diverging” winds in the lower levels, which actually causes downward motion as air first hits the lake. Note how clouds are typically puffier just downwind of the lake, due to the opposite effect; faster-moving air over the lake runs into slower moving air on land, causing the air to literally pile up and resulting in upward motion.
b) heat and moisture are still transported through ice! essentially all of western Lake Erie is frozen, but lake effect clouds are clearly bubbling up over the ice. Thin ice in particular still transports a good amount of heat and moisture through to the air, which is why lake effect can occur off of a rather icy lake.
c) other sources of moisture greatly aid our lake effect. Note how at the end of the loop, more robust clouds from over Michigan hit the western basin of Lake Erie, causing the lake effect clouds to expand and become puffier looking (taller).
d) converging winds cause more organized bands; note the band of more puffy looking clouds coming onshore east of Cleveland, with the clouds north and south of the band clearly converging on the band. Convergence, either down the middle of the lake or due to an interaction with the shoreline, is one of the main causes for intense bands of lake effect that produce the most prolific snowfall. Winds often converge near the shoreline due to friction causing slower and more southerly (or backed) winds on land and colder air over land causing the air to be denser inland from the lake.
2) WINDEX or Wintertime INstability inDEX: WINDEX snow showers occur as a result of a very cold air mass moving over warmer ground, causing the low-levels of the atmosphere to become unstable. Note the rows of clouds that develop during the day across a lot of areas well away from any lake effect; these are the result of WINDEX! What’s cool is that areas that have a deeper snow cover (such as a swath of NW Ohio) and hence have less heat transferred from the ground see no cloud development, while areas of less snow cover (such as near Detroit and much of inland NE Ohio) see cloud development. There’s even cloud development over Toledo as the result of an urban heat island creating locally warmer ground-level temperatures! This phenominon is often why snow showers and squalls often develop even well away from the Great Lakes the day after a strong cold front moves through during the fall or early winter. In this case, since much of the area has some snow cover and because the airmass is very dry, only flurries fell out of these clouds.
3) A source of large-scale lift acting on low-level cloud development. A “vorticity maximum” is moving across southern Michigan this afternoon, with lift ahead of the feature. Note how the WINDEX and lake effect clouds gradually get puffier looking or taller from west to east during the second half of the loop, hitting Lake Erie just as the sun starts going down. This is why subtle features that cause even weak large scale lift are important to lake effect snow forecasting.