The synoptic-based Heat/Health System (developed at the University of Delaware) has been running in Phoenix for four summers. Use of the System continues to be a growing experience, partly because of the extreme summer climate, but also because of complexities caused by intense “dry heat” episodes contrasted with periods of modestly high temperatures combined with high dew points. For these reasons, several modifications, unique to Phoenix, have been made to the System. One of these involves the inclusion and fine tuning of a record high temperature curve which is frequently approached; if temperatures are near that curve, the Phoenix WFO issues a Heat Advisory regardless of the system guidance. Other modifications have been made or are under consideration and will be discussed in this paper.

One system enhancement that is being investigated involves the possibility of issuance of "Evaporative Cooler Alerts." Concurrent with this is the expansion of the System to Yuma, Arizona – where temperatures in excess of 100 degrees combined with dew points in the mid 70s are frequent occurrences. The Phoenix WFO is considering issuing special advisories when conditions are such that the ubiquitous evaporative coolers in the area are inefficient in providing any relief in Phoenix, or when the combination temperatures above 100 with mid 70s dew points are forecast and the System does not generate the need for an advisory. The complexities of dealing with extraordinarily high temperatures and low humidity followed by modestly high temperatures and high dew points will be explored.