The record-breaking central California heat wave of July 2006

A record-breaking heat wave affected much of the state of California during the period 16-26 July 2006. Although numerous daily maximum temperature records were set, other aspects of the event were even more remarkable. Of particular note were both the elevated overnight minimum temperatures and the number of consecutive days the hot weather persisted. Many inland locations set their all-time high minimum temperature records, in some cases exceeding the previous record by a wide margin, as well as established new records for 3-, 5- , 7- and 10-day average temperatures. Also of note were the uncommonly high dew points, reflective of an influx of subtropical moisture that occurred during the event, and which further increased the heat indices and thus the impact of the hot weather.

This heat wave occurred in association with the development and subsequent persistence of an extraordinarily robust large-scale upper-level high, centered over the Great Basin and with a ridge axis extending westward through central California. Even in the 11-day average, the 500 mb height center reached almost 600 dm.

The prolonged nature of this extreme high temperature event resulted in significant adverse impacts on California's economy and energy supply, as well as on the health of its population. The all-time state record for energy consumption was set on 24 July 2006 with 50,270 Megawatts used, while more then a million customers ultimately lost power. In excess of 140 deaths were directly attributable to this heat wave.

In this paper we will examine both the associated synoptic scale meteorological evolution and the locally significant mesoscale influences in the vicinity of the central coast of California. Its magnitude in an historical context will be assessed, and we will compare it to other extreme heat wave events. The wide-ranging significant health and economic impacts of this heat wave will also be considered.