An Evaluation of the Severity of the
January 1998 Ice Storm in Northern New England
Report for FEMA Region 1
KATHLEEN F. JONES
NATHAN D. MULHERIN
1. INTRODUCTION
A severe freezing-rain storm hit Canada and the northeastern United States the week of
January 5, 1998. Warm moist air from the Gulf of Mexico encountered cold Arctic air, initially
in northern New York and southern Quebec. The cold front moved south and east from there into
Vermont, New Hampshire, and Maine. This set up the classic scenario for freezing rain, as the
less dense, warm Gulf air was forced up over the Arctic air. The liquid precipitation cooled as it
fell through the cold air. When the still-liquid rain and drizzle drops struck a tree or a structure
they froze as the latent heat of fusion was removed by convective and evaporative cooling. Ice
freezing to trees and overhead lines caused hundreds of millions of dollars of damage in both
countries and left hundreds of thousands of people without power for periods ranging from hours
to more than three weeks. In the United States the President declared disasters in New York five
counties, six Vermont counties, and all New Hampshire and Maine counties except the coast.
This ice storm was the worst ever in the experience of many people in upstate New York and
northern New England, both in the amount of ice that accreted on trees and structures, and the
extent of the storm. The storm footprint extended from Watertown in upstate New York and Dub-
lin in southwestern New Hampshire to Calais in eastern Maine, as well as into the Canadian
provinces of Ontario, Quebec, and New Brunswick. (Fig. 1).
The magnitude of the storm inspired superlatives. It has been called a freak storm, the ice
storm of the century, and the worst ice storm in 500 years. The damage to trees in the state and
national forests has been compared to the 1938 hurricane. The purpose of this report is determine
how rare an ice storm like this really is in northern New England. If severe ice storms occur
frequently enough, the power and communication infrastructure must be designed to withstand
the loads imposed by those storms.
In the next section, publications that specify design ice loads for overhead lines and commu-
nication towers are reviewed. The uniform ice thickness that is used to quantify these design
loads is defined and described in the third section, along with procedures for determining the uni-
form thickness from samples of accreted ice. As this is difficult to do, ice loads have rarely been
measured in the United States. We have, however, developed ice accretion models that use hourly
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