Meteorological Twitter has been pretty quiet of late. In fact, the only real “hot-topic” cooking up is about heat—no surprise in the summer months. This subject is revisited every summer and it often has to do with criteria. What constitutes a heat advisory? How about an excessive heat warning? As the weather wise know, answers to those questions vary based on location. But there are some broader points to the heat narrative that inspire further discussion. Scientists always seem to want hard and fast rules—or certain thresholds. Does a certain ambient temperature need to be reached? Should it simply focus on heat index? How does time factor into the equation?
Josh: I believe (and this is only my opinion) that dew point and low temperature should be noted in official, National Weather Service (NWS) criteria. But that is me. To really raise the bar on talk of rising temperatures, I got in touch with fellow thewxsocial.com blogger Gary Szatkowski who has forecast his share of high heat events in the Philadelphia Metropolitan Area. Joining us is guest blogger Alek Krautmann of NWS New Orleans. Alek’s Master’s thesis focused on summer heat events in the Midwest.
Alek: Somewhat surprisingly, heat waves lack a uniform meteorological definition. Heat is known as a creeping hazard and starts with subtle impacts that do not result in structural damage like other meteorological events. Components to consider that comprise a heat wave include: duration, daytime high and overnight low temperatures, atmospheric moisture, human impacts, and location. Even with these deterministic factors, identifying when they come together to have significant impact can be difficult. Onset differs for population, climate, activity, and health.
Josh: Is a heat advisory really needed? Maybe not for you or me… we know the drill… more water than usual, less outdoor exertion, lighter clothing. But there are outdoor workers in industries such as construction, landscaping and roofing. Owners and managers of these companies don’t slow down business just because the weather folks said it might be a good idea. The hard laborers in these forces may not readily receive weather message or even speak the language in which those messages are offered (see lightning fatalities). For those workers and others, the body can breakdown quickly in hot temperatures and the symptoms of heat related illness can appear suddenly. Annual and often repetitive advisories may serve as a reminder, a review of heat related illness every year, especially for those most susceptible. In addition to outdoor workers these messages must be reinforced to the elderly, the infirm, kids (their parents), pets and of course those without access to air conditioning.
Alek: Elevated heat stress can aggravate one’s preexisting cardiovascular and respiratory conditions. The urban heat island, socioeconomic factors, and ozone pollution come together to result in a unique geographic vulnerability for urban residents.
A common criterion for identifying especially hot weather is the heat index since it accounts for both moisture and temperature. Certain heat index thresholds can be effective as a quick catch all for some of the most uncomfortable conditions but, because of all the factors listed above, flexibility needs to be the name of the game when it comes to heat. It’s important for heat safety and awareness messaging to be constant reminders throughout the summer.
Another challenge is that temperature is measured in the shade. Out in the sun, one can experience temperatures much hotter! Some groups like the Oklahoma Mesonet are working to promote usage of the Wet Bulb Globe Temperature to better account for these conditions. Visit this webpage for more information and to see a live map of the index.
Even though most homes have air conditioning, it’s not always working or in use. A particular concern would be a heat wave affecting a large city right after widespread power outages. In July 2006, a storm with severe winds knocked out power for most of St. Louis during a heat wave. We saw it again from hot temperatures in the days immediately after the June 2012 derecho that tracked from the Midwest to the Mid Atlantic. As folks along the Gulf Coast know all too well, some of the hottest weather of the year can come from the strong subsidence following a tropical cyclone landfall when power is often out.
Josh: For those fortunate enough to have a pool, cooling off is achievable, and with air conditioning, this is especially true at night while sleeping. There was recently a run of 7-straight days in New Orleans without the air temperature falling below 80 degrees. The NWS (wisely, in my opinion) extended heat advisories, despite borderline criteria, because of continuously warm nights. Studies have proven that the body cools while sleeping, specifically in REM sleep. After an extremely hot day, without completing that thermoregulation cycle at night, the body is at greater risk for heat illness the following day.
Gary: When the heat gets worse and moves into warning territory, we know that things can get very bad in a short period of time (several days). As we saw in Chicago/Milwaukee back in 1995 and in Europe in 2003, the death toll from excessive heat can be staggeringly high. How do these high impact excessive heat events happen? In the subsequent reviews of these events, one of the words you see used multiple times is ‘unimaginable’. For both these events, the weather forecasts ranged from good to excellent. The high temperatures and heat index values were discussed and forecast prior to the events. The ‘unimaginable’ part was not the weather, but the weather impacts.
Josh: Eric Klinenberg performed a “social autopsy” on the infamous Chicago Heat Wave to which Gary alluded. 1995 wasn’t that long ago. 20 years later, imagine a staggering 739 heat related deaths. From July 13-20, there were several days where the mercury eclipsed 100 derees and the heat indices were into the 120s. Many meteorologists attributed the deaths to purely natural disaster. However, Klinenberg uncovered much more of a societal pattern in the deaths. Most victims died alone and more than 75 percent were over the age of 65. African Americans were one and half times more likely to die than whites and 30 and half times more likely to die than Latinos. More men died than women. While epidemiological study alone provided valuable if not unsurprising demographic data on the deaths, the “social autopsy” revealed more. Specific neighborhoods were at risk. Former city manufacturing centers in decline, crime-ridden and desolate, had and were provided fewer government and private sector resources—in some cases this was as simple as help unwilling to travel to these more dangerous neighborhoods. Media coverage even played a role due to the fact the heat does not have the same “dread factor” as a tornado or flood and thus received less attention.
Other cities can learn that location is of utmost importance in long duration episodes of heat. As Klinenberg found, elderly residents of more violent neighborhoods are fearful of venturing out and thus less likely to seek out or receive resources to stay cool. Leaders need to be proactive in identifying these at-risk communities, spreading awareness and making options known before and available during dangerous heat. Media meteorology practitioners need to be wary not to lessen the threat of heat. We spoke honestly early, let’s continue to do that. Think about everything uncovered in the social autopsy. You and I are not as at risk to heat as others. In the end, we are all sacks of flesh and water, and dehydration and exhaustion follow similar progressions. But we’re talking about predisposition here. You and I may be fortunate enough to have air conditioning, shelter, or heck, accessible drinking water. There are many others that do not have these modern amenities. Consider that, and zero in on those communities in the next heat forecast.
Gary: Prior to a heat event, how do you know if your community is vulnerable to dealing with a high impact excessive heat event? Has your community planned for it? Is the event considered ‘unimaginable’? Or is it accepted as a low probability but imaginable event? Has your community identified those portions of the population more vulnerable to excessive heat as part of their planning?
Are your public health officials and emergency management officials on the same page? Heat was viewed solely as a public health issue, not an emergency management issue in the City of Chicago prior to the 1995 event. Afterwards, they changed their approach to extreme heat as a lesson learned. Has your community learned that lesson from others’ experience?
As the event approaches, the role of the TV meteorologists is critical. Media in the City of Philadelphia have taken excessive heat very seriously since the 1993 Philadelphia heat wave. As a heat event begins to develop, warnings and preparedness information are communicated, often as the lead story.
When the heat event arrives, besides continuing the communication of warning and preparedness information, what else should media do? To figure out just how big a problem is out there, you should be in close communication with your public health officials. Monitor reports of emergency room activity. As soon as you hear about one or more hospitals going into ‘bypass’ status (ERs turning away patients due to capacity issues), you’ve got a very serious problem developing. At the height of the event in Chicago, over 25 hospitals were in bypass.
Josh: To bring us full circle, is heat safety more about local awareness than criteria? Is it fair to say that if a certain threshold isn’t met we shouldn’t push aside the typical hot weather tips? What about when the map shows a heat advisory cutting off from one county to the next? Sometimes there is a hole within a circle of heat advisories. Heat presents a unique communication challenge—one we need to address and take seriously. I would encourage public and private sector meteorologists to continue evaluating their communities. Identify the most vulnerable population segments and where those residents are located. Tailor messages for them, reach out to emergency officials, or dare I say, speak with leaders in those communities. Heat has been referred to as a silent killer. Let’s not allow that to be because WE were silent.