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Last Thursday on my weekly 3:30 p.m. appearance on Sirius Speedway (channel 128), Dave Moody asked me about how thunderstorms form. I briefly explained why thunderstorms can form on hot, humid afternoons, but I thought I'd use today's blog to go more in depth.
Thunderstorms occur in a few different ways: they can be a single cell (isolated), in a cluster, or part of a line. Thunderstorms are convective, which means they form due to humid, rising air. A couple of things cause air to rise, including unequal heating of the Earth's surface, terrain such as mountains, frontal zones, and upper level wind patterns interacting with surface wind patterns.
A thunderstorm goes through a few different stages. The first stage is the cumulus stage. Normally, cumulus clouds are associated with fair weather. But given the right conditions, the cumulus cloud can grow vertically through the atmosphere. It can grow because of constant rising air below it due to instability. The next stage is mature, which means the storm has a downdraft. During the cumulus stage, a storm grows above the freezing level in the atmosphere. The cloud particles get bigger and bigger, and they also get heavier. The rising air beneath the cloud is no longer able to keep the particles suspended, so they begin to fall. Cooler air is drawn into the storm, and since cooler air is heavier than warm air, it falls creating the downdraft. A thunderstorm is strongest during the mature stage. It can be identified by the anvil shape of the cloud top, which can reach to 40,000 ft. high in the atmosphere. Lightning and thunder occur during the mature stage, along with a strong gust of wind (downdraft) when it starts raining. This is why it often times gets windy right before a storm hits. After about 15 - 30 minutes, the storm enters the dissipating stage. Downdrafts make up most of the storm, preventing warm air from rising back in and creating cloud droplets. The rain falling beings to lighten up, and the storm gradually dies. I've left out a bunch of complicated technical stuff, but severe storms tend to last longer than an ordinary storm described above. When a storms lasts longer, it has the potential to create hail, very strong winds, and tornadoes. The following image is a picture of the thunderstorm stages from www.boqueteweather.com.
Now on to racing news. Congrats to Ryan Hunter-Reay on his first win in the IndyCar Series last weekend in Watkins Glen! Kyle Busch took the checkered flag at the Sprint Cup race in Daytona after a crazy green/white/checkered (sort of) finish. This weekend's races are sure to be exciting - weather providing of course! Here are this weekend's race forecasts.
IndyCar Series - Nashville Superspeedway on Saturday (7/12) at 8 p.m. ET on ESPN. Qualifying is Friday at 5:30 p.m. Indy Lights race Saturday at 3:30 p.m. A cold front dropping in from the north will stall and wash out in the region between Thursday and Saturday. Friday will be a mix of sun and clouds with a slight chance of a shower or storm in the afternoon. Temperatures will be near 90 degrees. Saturday will be the same - partly cloudy, warm, and humid. Fortunately the race is in the evening, so the afternoon high near 91 degrees will drop slightly to around 86 degrees for the race. Winds from the southwest at 5-10 mph. There is once again a chance of a shower or thunderstorm.
NASCAR Nationwide Series - Chicagoland Speedway on Friday (7/11) at 7:30 p.m. ET on ESPN. A low pressure system will start making its way toward the Midwest on Friday. Ahead of the low, it will be hot and breezy with temperatures in the lower 90's. Southwest winds 15-20 mph. There is a slight chance of thunderstorms Friday evening. The temperature at the start of the race will be around 89.
NASCAR Sprint Cup - Chicagoland Speedway on Saturday (7/12) at 6:30 p.m. ET on TNT. Qualifying is Thursday at 8:30 p.m. ET. As I type this (Thursday afternoon), there is a severe thunderstorm watch in effect for Joliet until 10 p.m. CT. A line of storms is moving east, and there is another area of storms behind that. This bears watching because it could effect qualifying this evening. Temperatures are in the lower 80's. On Saturday, a low pressure system will advance through the region along with a cold front. Expect increasing clouds with scattered showers and thunderstorms likely. Temperatures will be a little cooler on Saturday in the mid 80's. When (if) the race starts, the temperature will be around 83 with a southwest wind 10-15 mph.
American Le Mans Series - Lime Rock Park on Saturday (7/12) at 2:05 p.m. ET. The race will be televised Sunday (7/13) at Noon ET on SPEED. The ALMS returns this weekend after an extended break! High pressure will build into the area Saturday with southerly flow. Expect sunshine, but it will be rather warm and humid. Afternoon temperatures will top out near 87 degrees.
Winchester Speedway - Saturday (7/12), gates open at 4:30 p.m., racing starts at 7 p.m. High pressure over the Atlantic will bring southerly flow into the Shenandoah Valley. Skies will be mostly sunny on Saturday with afternoon temperatures warming into the upper 80's. By race time, expect a temperature near 84 degrees.
I went to Chicagoland Speedway last year... here is a photo. On this particular day, the weather was beautiful!
Here are some photos from the IndyCar race at Watkins Glen from Theresa.
Ryan Hunter-Reay Wins!
And don't forget to listen to Sirius Satellite Radio - Sirius Speedway, channel 128 every Thursday at 3:30 p.m. to hear me give the NASCAR forecast! Next weekend I'm going to Mid-Ohio Sports Car Course for the ALMS/IndyCar weekend!!
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