This week's heatwave: cause, effects, more to come?
The heat in the central and eastern U.S. has finally begun to subside with a (relatively weak) cold front pushing south. Yesterday, 24 states were under some kind of heat advisory. Heat indices (which combines temperature and humidity, and is sometimes described as "feels like" temperature) were pushing 120°F this week. Today, only a handful of advisory areas are left, but the parent ridge for this event is still there, and global models aren't suggesting it's going to move out any time soon. It looks like the heat is going to build back up in the northern states and stay parked in the southern states. We might be looking at another episode of extreme heat next week, particularly in the upper Midwest.
Heat advisories (in pink) as of 7:30 ET on Wednesday, July 13, 2011. Image taken from Wundermap.
The Christian Science Monitor called today to ask about the heat wave, whether it was normal, and what kind of effects an event like this has (CSM article: "Heat wave: Four things that will rise with temperature")
Yes, this heat wave can be described as normal. We often see heat waves that last a few days during the summer months. It's July, and it's expected. Although, as I remember all too well from living in the southeast U.S., when you're the one in the heat wave, you can't help but feel like it's totally bizarre and why isn't this heat ending already?! What is abnormal is when we see repeated or extended heatwaves throughout the summer and into the fall, like we saw in 2010. Jeff wrote a great blog on 2010's extreme weather events, and if you haven't read it already I recommend it. The deadliest heat wave in human history struck Moscow last year. Their all-time high record was tied or broken five times in two weeks. That's extreme. But it's also not totally unexpected—2010 tied 2005 for the warmest year on record. 2011 is shaping up to be a pretty extreme year as well (e.g. tornadoes, floods, droughts, wildfires...), so don't be completely surprised if we see quite a few heat waves this summer.
When I read that they wanted to ask me about the effects of the heat wave, the first thing that came to mind (obviously) were health impacts. Heat waves are incredibly taxing on the elderly and people with asthma. Low temperatures have only been getting down to the lower 80s (F) in some areas, and air quality is poor. But an effect we don't immediately think of is more long-term. We're using much more energy during extreme weather events, which not only pumps up our utility bills, but also pumps more and more carbon and particulate matter into the atmosphere, which only exacerbates the problem (albeit on different time scales). Studies have been done to understand our behavior during heat waves and bad air quality, and while a lot of people stay home and turn on the A/C, many, many people get in their cars and drive to the mall or the movie theater, or some other place where they don't have to foot the energy bill.
In the meantime, we're drowning in fog in San Francisco, so I don't know who has it worse. Although we do have one thing in common with the southeast today: extreme humidity. You can tell the air is saturated when it's 60°F and you can see your breath.