The Nature and Impacts of the July 1999 Heat Wave in the Midwestern United States: Learning from the Lessons of 1995

Abstract

The July 1999 heat wave in the Midwest was an event of relatively long duration punctuated by extreme conditions during its last 2 days. The intensity of the heat wave on 29 and 30 July rivaled that of the 1995 heat wave that killed more than 1000 people in the central United States. In 1999, however, the death toll was about one-fourth of this amount in the same region. The 1999 heat wave 2-day maximum apparent temperature was slightly less than during the 1995 heat wave at most Midwestern first-order stations. In addition, the 2-day peak was preceded by several hot days that allowed some short-term acclimatization to occur prior to the intense final days. In Chicago, conditions during the peak of the 1999 heat wave were very similar to those during the 1995 heat wave peak, especially the extreme nocturnal conditions of temperatures and humidity. Therefore, it seems unlikely that the reduction in the heat wave death toll in Chicago from about 700 in 1995 to 114 in 1999 is due solely to meteorological differences between the two heat waves. In St. Louis, the 1999 heat wave was intense for a much longer duration than the 1995 heat wave, thus partially explaining the increase in heat-related deaths there from the 1995 event to the 1999 event. An examination of heat wave response efforts in both Chicago and St. Louis leads to the conclusion that both cities were quite effective at mitigating their respective heat wave mortality rates, which in the 1999 event were almost exactly the same in both metropolitan areas. This represents a great improvement for the city of Chicago compared to the 1995 heat wave. Suggestions are made for further improving municipal heat wave response efforts based on the 1999 experience.

North American extreme temperature events and related large scale meteorological patterns: a review of statistical methods, dynamics, modeling, and trends

“…Midwest events Heat waves affecting the Midwest have anticyclonic flow at mid-levels, either as a closed anticyclone or as a strong ridge (Klein 1952;Karl and Quayle 1981;Namias 1982;Chang and Wallace 1987;Lyon and Dole 1995;Kunkel et al 1996;Livezey and Tinker 1996;Palecki et al 2001;Meehl and Tebaldi 2004;Lau and Nath 2012;Loikith and Broccoli 2012;Teng et al 2013), with associated clear skies allowing maximum solar heating of the surface as well as adiabatic warming from subsidence.…”

“…The regional-scale flow also interacts with local mechanisms, particularly the Urban Heat Island (UHI) effect (Kunkel et al 1996;Palecki et al 2001). Another common element identified in several studies is the presence of drought (Chang and Wallace 1987;Karl and Quayle 1981;Namias 1982;Lyon and Dole 1995) as well as simultaneous precipitation deficits (Lau and Nath 2012).…”

Synoptic Conditions Generating Heat Waves and Warm Spells in Romania

“…In addition, there is no exact definition of HWs in terms of type of datasets used. Thus, many definitions could apply to HWs that quantify the duration and/or intensity of either nighttime minimum or daytime maximum temperatures as well as both of them or mean daily temperature [1,3,35,37,38,67,68]. Most papers referring to HWs use the aforementioned definitions, but some of them consider data sets only for a few months of the year (usually June-August or April-September).…”

Identifying extreme hottest days from large scale upper air data: a pilot scheme to find California Central Valley summertime maximum surface temperatures

“…From that comparison, Schär et al gain confidence in their simulations of how the mean and variability might increase by the end of this century. Palecki et al (2001) use apparent temperature values both maximum and daily averages to compare the severe 1995 and 1999 heat events that afflicted the Chicago, USA, area. They do not use a threshold or any other criterion to define the heat wave specifically.…”