• Cortinas, J., 2000: A climatology of freezing rain in the Great Lakes region of North America. Mon. Wea. Rev, 128 , 35743588.

  • DeGaetano, A. T., 2000: Climatic perspective and impacts of the 1998 northern New York and New England ice storm. Bull. Amer. Meteor. Soc, 81 , 237254.

    • Search Google Scholar
    • Export Citation
  • Dudhia, J., 1989: Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model. J. Atmos. Sci, 46 , 30773107.

    • Search Google Scholar
    • Export Citation
  • Jones, K. F., and N. D. Mulherin, 1998: An evaluation of the severity of the January 1998 ice storm in northern New England. U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory Report, 67 pp. [Available from CRREL, 72 Lyme Road, Hanover, NH 03755.].

    • Search Google Scholar
    • Export Citation
  • Kain, J. S., and J. M. Fritsch, 1993: Convective parameterization for mesoscale models: The Kain–Fritsch scheme. The Representation of Cumulus Convection in Numerical Models, Meteor. Monogr., No. 46, Amer. Meteor. Soc., 165–170.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc, 77 , 437471.

  • NCDC, cited 1998: Service assessment: The ice storm and flood of January 1998. [Available online at http://www.nws.noaa.gov/om/iceflood.pdf.].

    • Search Google Scholar
    • Export Citation
  • NCDC, 1999: Billion dollar U.S. weather disasters 1980–1998. National Climatic Data Center World Wide Web document. [Available online at http://www.ncdc.noaa.gov/ol/reports/billionz.html.].

    • Search Google Scholar
    • Export Citation
  • Reisner, J., R. M. Rasmussen, and R. T. Bruintjes, 1998: Explicit forecasting of supercooled liquid water in winter storms using the MM5 mesoscale model. Quart. J. Roy. Meteor. Soc, 124B , 10711108.

    • Search Google Scholar
    • Export Citation
  • Roebber, P. J., and L. F. Bosart, 1998: The sensitivity of precipitation to circulation details. Part I: An analysis of regional analogs. Mon. Wea. Rev, 126 , 437455.

    • Search Google Scholar
    • Export Citation
  • Stauffer, D. R., and N. L. Seaman, 1990: Use of four-dimensional data assimilation in a limited-area mesoscale model. Part I: Experiments with synoptic-scale data. Mon. Wea. Rev, 118 , 12501277.

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., and C. J. Guillemot, 1995: Evaluation of the global atmospheric moisture budget as seen from analyses. J. Climate, 8 , 22552272.

    • Search Google Scholar
    • Export Citation
  • Zhang, D-L., and R. A. Anthes, 1982: A high-resolution model of the planetary boundary layer—Sensitivity tests and comparisons with SESAME-79 data. J. Appl. Meteor, 21 , 15941609.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 17 17 17
PDF Downloads 14 14 14

The 1998 Ice Storm—Analysis of a Planetary-Scale Event

View More View Less
  • 1 Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, Canada
  • | 2 Atmospheric Science Group, Department of Mathematical Sciences, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin
Restricted access

Abstract

The ice storm of 5–9 January 1998, affecting the northeastern United States and the eastern Canadian provinces, was characterized by freezing rain amounts greater than 100 mm in some areas. The event was associated with a 1000–500-hPa positive (warm) thickness anomaly, whose 5-day mean exceeded +30 dam (+15°C) over much of New York and Pennsylvania. The region of maximum precipitation occurred in a deformation zone between an anomalously cold surface anticyclone to the north and a surface trough axis extending from the Gulf of Mexico into the Great Lakes. The thermodynamic impact of this unprecedented event was studied with the use of a four-dimensional data assimilation spanning an 18-day period ending at 0000 UTC 9 January 1998. A moisture budget for the precipitation region reveals the bulk of the precipitation to be associated with the convergence of water vapor transport throughout the precipitation period. The ice storm consisted of two primary synoptic-scale cyclonic events. The first event was characterized by trajectories arriving in the precipitation zone that had been warmed and moistened by fluxes over the Gulf Stream Current and the Gulf of Mexico. The second and more significant event was associated with air parcels arriving in the precipitation zone that had been warmed and moistened for a period of several days in the planetary boundary layer (PBL) of the subtropical Atlantic Ocean. These parcels had equivalent potential temperatures of approximately 330 K at 800 hPa as they traveled into the ice storm's precipitation zone.

Analogs to this unprecedented meteorological event were sought by examining anomaly correlations (ACs) of sea level pressure, and 1000–925 and 1000–500-hPa thicknesses. Five analogs to the ice storm were found, four of which are characterized by extensive freezing rain. The best analog, that of 22–27 January 1967, is characterized by freezing rain extending from the northeastern United States into central Ontario. However, the maximum amounts are less than 50% of the 1998 case. An examination of air parcel trajectories for the 1967 case reveals a similar-appearing horizontal spatial structure of trajectories, with several traveling anticyclonically from the subtropical regions of the eastern Atlantic. However, a crucial distinguishing characteristic of these trajectories in the 1967 case is that the air parcels arriving in the precipitation zone had equivalent potential temperature values of only 310 K, as compared with 330 K for the 1998 ice storm trajectories. It was found that these air parcels had traveled above the PBL and, therefore, had not been warmed and moistened by fluxes from the subtropical oceans.

Corresponding author address: Dr. John R. Gyakum, Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montreal, QC H3A 2K6, Canada. Email: gyakum@zephyr.meteo.mcgill.ca

Abstract

The ice storm of 5–9 January 1998, affecting the northeastern United States and the eastern Canadian provinces, was characterized by freezing rain amounts greater than 100 mm in some areas. The event was associated with a 1000–500-hPa positive (warm) thickness anomaly, whose 5-day mean exceeded +30 dam (+15°C) over much of New York and Pennsylvania. The region of maximum precipitation occurred in a deformation zone between an anomalously cold surface anticyclone to the north and a surface trough axis extending from the Gulf of Mexico into the Great Lakes. The thermodynamic impact of this unprecedented event was studied with the use of a four-dimensional data assimilation spanning an 18-day period ending at 0000 UTC 9 January 1998. A moisture budget for the precipitation region reveals the bulk of the precipitation to be associated with the convergence of water vapor transport throughout the precipitation period. The ice storm consisted of two primary synoptic-scale cyclonic events. The first event was characterized by trajectories arriving in the precipitation zone that had been warmed and moistened by fluxes over the Gulf Stream Current and the Gulf of Mexico. The second and more significant event was associated with air parcels arriving in the precipitation zone that had been warmed and moistened for a period of several days in the planetary boundary layer (PBL) of the subtropical Atlantic Ocean. These parcels had equivalent potential temperatures of approximately 330 K at 800 hPa as they traveled into the ice storm's precipitation zone.

Analogs to this unprecedented meteorological event were sought by examining anomaly correlations (ACs) of sea level pressure, and 1000–925 and 1000–500-hPa thicknesses. Five analogs to the ice storm were found, four of which are characterized by extensive freezing rain. The best analog, that of 22–27 January 1967, is characterized by freezing rain extending from the northeastern United States into central Ontario. However, the maximum amounts are less than 50% of the 1998 case. An examination of air parcel trajectories for the 1967 case reveals a similar-appearing horizontal spatial structure of trajectories, with several traveling anticyclonically from the subtropical regions of the eastern Atlantic. However, a crucial distinguishing characteristic of these trajectories in the 1967 case is that the air parcels arriving in the precipitation zone had equivalent potential temperature values of only 310 K, as compared with 330 K for the 1998 ice storm trajectories. It was found that these air parcels had traveled above the PBL and, therefore, had not been warmed and moistened by fluxes from the subtropical oceans.

Corresponding author address: Dr. John R. Gyakum, Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montreal, QC H3A 2K6, Canada. Email: gyakum@zephyr.meteo.mcgill.ca

Save