It was a very active and damaging Wednesday afternoon. Each of the snapped tree icons below represent a wind damage report. A lot of these were snapped trees, but there were a few structures that were damaged by the intense storms as well.
Another round of severe weather is possible today (Thursday) as our atmosphere “reloads” from yesterday’s storms. Everyone is under the gun for severe weather this afternoon, but the best chance will be in the yellow shaded areas…which is just about our entire viewing area.
The main threats like the last couple of days will be frequent lightning, very heavy rainfall, and the potential for damaging winds. While the tornado threat is low it is not zero this afternoon.
Thunderstorms look to increase after the lunch hour and will likely ramp up in intensity toward the middle and latter portion of the afternoon. A few storms could still be with us overnight, but there severe threat should subside after 10pm.
The intense wind damage observed in Salem and Martinsville Wednesday afternoon and evening was likely the result of a microburst. A microburst is a rapidly descending “blob” of air from a thunderstorm that creates very intense damage where it strikes. There are indications that we could see more of these intense downdrafts Thursday afternoon. The picture below illustrates how a microburst develops.
We are about to nerd out big time. If you’re interested you’re welcome to join the ride…
Some of those same ingredients needed to generate a microburst that were present Wednesday are also back this afternoon. If storms can take advantage of sunshine and daytime heating we could be in for another active and potentially damaging day. Below is something we definitely don’t show on air, but something vital to the forecast process. A skew-T as it’s called shows us the vertical profile of our atmosphere so meteorologists can get a sense of whats going on with the weather from the surface to where jet aircraft fly. We can quickly determine wind direction and speed along with temperature and dew point. Many many more things can be found by using this very important tool, but today we are focused on the red and green lines.
The red line indicates the temperature. The green line represents the dew point. This is a screen shot from last nights computer forecast run based off of the 8:00pm weather balloon launch. The skew-T below is showing us what the atmosphere could like this afternoon. To get a microburst you need to have dry air in the mid-levels of the atmosphere. Why? Because when rain starts falling initially into that dry air the rain will evaporate. Evaporation is a cooling process and therefore the air around the evaporation cools as a result. At the same pressure cooler air is more dense than warm air. As a result of this scientific fact the cooler air will sink to the ground. Since there is no place for the air to go once it reaches the ground it spreads out as very strong winds at the surface. The drier the air in the mid-levels of our atmosphere the more downward momentum that “blob” of air will have and therefore the stronger the winds at the surface will be.
Ok…back to those red and green lines. When they are far apart the air is dry. When they are close together the air is more saturated. Notice how far the red and green lines are away from each other at about 18,000 feet above the surface of the Earth. Also note we have a ton of moisture at the surface as the humidity is cranked up. By looking at this chart if we do in fact get intense thunderstorms to develop this afternoon for sure a main threat will be damaging wind.
Hope you enjoyed this meteorology lesson! Make sure you download the WSLS 10 weather app…if watches and warnings are issued this afternoon you will get them on your smart phone.