An Assessment of National Weather Service Warning Procedures for Ice Storms

104 WEATHER AND FORECASTING VOLUME 24 An Assessment of National Weather Service Warning Procedures for Ice Storms DAVID A. CALL Ball State University, Muncie, Indiana (Manuscript received 14 January 2008, in final form 15 August 2008) ABSTRACT Ice storms cause substantial damage to the United States every winter season, and the costs have increased in recent years. Accurate prediction and timely dissemination of warnings are effective ways to reduce the effects, because institutions and individuals can take actions to reduce the impacts. The National Weather Service (NWS) is the U.S. government agency charged with issuing warnings of impending ice storms. A survey of NWS warning coordination meteorologists was conducted to assess their awareness of the ice storm hazard, procedures followed to warn for ice storms, and level of contact with members of the community. Several warnings issued in advance of a recent ice storm were also examined. The findings of this research are twofold. First, most meteorologists with the NWS perceive the ice storm hazard with a level of seriousness consistent with climatology. Most follow established procedure and actively engage in warning specific groups before a storm. The second finding was that individual offices maintain a high level of autonomy. While this offers valuable flexibility and the opportunity to try new approaches, there is significant variation in the length and tone of ice storm warnings themselves. Additionally, several offices do not contact outsiders or offer general educational products, which may underserve constituents in their forecast areas. To solve these problems, it is suggested that NWS management encourage and support proactive communication policies. The NWS should also analyze the audience of their warning products and consider guidelines regarding intended audience, tone, and length. 1. Introduction and background same manner as freezing rain. Nonetheless, both sleet and freezing rain are hazardous. Furthermore, an ice Ice storms are a serious hazard that cause millions of storm’s disruption may be extended if cold air follows dollars in damage each year, and catastrophic events are the storm, which limits melting and forces people becoming more common (Changnon 2003). One way to without electricity to use generators (which can cause reduce the costs associated with ice storms is to improve carbon monoxide poisoning) or to travel to shelters. warning procedures, which aids community leaders, first responders, and individual citizens in preparing. Through an analysis of data collected from a question- a. Climatology of freezing rain and ice storm naire and from observation of recent ice storm warn- catastrophes ings, this paper will offer insights into National Weather While there is some disagreement about the exact Service (NWS) ice storm warning procedures and sug- frequency of freezing rain [cf. maps in Bennett (1959) gestions for improvement. with those in Changnon (2003)], there is general An ice storm produces freezing liquid precipitation agreement that most of New England, New York, and (ice) in the form of freezing rain that creates a glaze of Pennsylvania annually experience $4 days of freezing ice on objects such as trees, roads, and utility lines precipitation, on average. Areas that typically experi- (Glickman 2000). Generally, a storm with sleet is less ence 3 days of freezing rain annually include the upper catastrophic than one with freezing rain because sleet Midwest, Appalachians, and Columbia and Snake River provides some traction for motorists (Kocin and Uccellini valleys (see also Cortinas et al. 2004). 2004, p. 151) and does not coat terrestrial objects in the In an analysis of property insurance loss data for the period 1949–2000, Changnon (2003) found that the Corresponding author address: David A. Call, Dept. of Geog- overwhelming majority of ‘‘catastrophic’’ storms affected raphy, Ball State University, Muncie, IN 47306. states from Texas to Maine, as shown in Fig. 1. States E-mail: [email protected] with 19 or more catastrophic storms during that time DOI: 10.1175/2008WAF2007111.1 Ó 2009 American Meteorological Society Unauthenticated | Downloaded 10/02/21 01:19 PM UTC FEBRUARY 2009 C A L L 105 FIG. 1. Map of the number of times each state experienced losses from ice storm catastrophes from 1949 through 2000. Neither AK nor HI had any losses during this time. Map based on data published by Changnon (2003). include North Carolina, Virginia, Maryland, Pennsylvania, freezing rain is expected (NWS 2005a). The NWS is New York, New Jersey, and all of New England. divided into six regions (Fig. 2), and several of these Two regions show a discontinuity between the risk of have issued supplemental directives regarding ice freezing rain and the occurrence of ice storm catastro- storms. For example, in the northern portion of the phe: the northern Midwest and the Deep South. While Eastern Region, warnings should not be issued unless at most of Minnesota, for example, averages 4 or 5 days of least 1.27 cm (0.50 in.) of freezing rain is forecast (NWS freezing rain per year (Bennett 1959; Changnon 2003; 2007). Some regions and individual forecast offices also Cortinas et al. 2004), only two ice storm catastrophes incorporate nonmeteorological criteria, such as time of occurred there between 1949 and 2000, which is fewer day, in deciding whether to issue warnings (see NWS than in Florida (see Fig. 1 again). Louisiana, Mississippi, 2007 for some examples). Alabama, and Georgia, which typically experience To make accurate forecasts and decide whether or not 1 day of freezing rain per year, registered an average of to issue warnings, forecasters must understand the 15 disasters for the same 52-yr period. Rauber et al. hazards that affect their area and the risks of each (2001) suggested two reasons for this: first, storms in the (Alexander 1993, p. 405; Lopez et al. 1993; Smith 2004, South have a higher moisture content than those in the p. 69). Their understanding is influenced by prior expe- upper Midwest, and, second, their durations are often rience with risks (Halpern-Felsher et al. 2001; Peacock longer. Thus, ice storms in the South, while less common et al. 2005), but expert and lay perceptions of risk often than those elsewhere, are more likely to cause ice ac- vary (Slovic 1987; Peacock et al. 2005; Siegrist and cumulations sufficient for severe damage. Sociological Gutscher 2006). More specifically, if an NWS employee and other environmental factors may also contribute, has little experience with a hazard, warning for the such as variations in the amount of equipment available hazard will be more challenging. Thus, individual em- for mitigation, population density, and forest cover. ployees may overwarn or underwarn, affecting the ability of the larger society to prepare and respond. b. Role of the National Weather Service While much research has shown the importance of The National Weather Service is the primary source accurately understanding risk, the process used to make for disaster warning information in the United States. the decision to warn is less well understood (Mileti and Its employees issue tens of thousands of warnings in any Sorensen 1990, 2–8). But, assuming that a local fore- given year; a small fraction of these are for ice storms. caster makes the decision to warn, it is important that According to NWS regulations, an ice storm warning the warning not only be accurate, clear, and confident, should be issued when more than 0.64 cm (0.25 in.) of but also that it offer guidance about what to do (Mileti Unauthenticated | Downloaded 10/02/21 01:19 PM UTC 106 WEATHER AND FORECASTING VOLUME 24 FIG. 2. Map showing NWS regions within the continental United States. and Sorensen 1990, 2–9). Alexander (1993, p. 401) has the ice storm hazard and how they warn both the gen- argued that a warning should include information about eral public and specific audiences, such as emergency how long a potential disaster will last and the expected managers. To focus the research, a series of specific impacts. It follows, then, that a study of NWS warnings questions were devised as listed here: should examine both the decision-making process be- d How seriously do NWS warning coordination mete- hind the warnings and the warning statements themselves. orologists (WCMs) perceive the hazardousness of ice Timely dissemination of warning information has re- storms on both absolute and relative scales? duced the impact of hazards such as severe convective d What products do they, or other members of their storms and snow (Corfidi 1999; Call 2005). Parker and respective offices, issue to warn people in advance of Neal (1990) note that, in general, accurate warnings are a storm? almost always issued, but warning dissemination is the d How much contact do they have with others in need more problematic aspect. In other words, an accurate of information regarding ice storms, such as emer- warning that is not heard or acted upon is of limited gency managers? value. While NWS warnings are available through Na- d Finally, what educational products and programs do tional Oceanic and Atmospheric Administration they provide to prepare people well in advance of a (NOAA) Weather Radio, previous research has shown storm situation? dismally low awareness of this system (Redmond 1995; Hammer and Schmidlin 2002), with many more people getting warnings through mass media and directly from 2. Methodology friends and family (Hammer and Schmidlin 2002). Thus, some offices have become active in communicating with To answer the research questions, documents about constituents (see Morris et al. 2002; Troutman et al. NWS warning guidelines and procedures were obtained 2001), and the NWS itself has pushed for improved from the NOAA Central Library and various NWS communication with emergency management officials Web sites, and a survey was mailed to 54 NWS WCMs in (NWS 1998).

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