Comparisons between this storm and major ice storms on 1/1/03 and 4/4/03.

  • High pressure and low-level cold air were retreating in this case. In the other two cases, the cold air was advancing south at low-levels.

  • Strong (20-40 kt) ageostrophic northerly flow was forecast below 900 mb in all cases, associated with strong low-level frontogenesis.

  • Negative EPV was diagnosed above a sloping frontal zone, indicating the potential for slantwise convection, as was the case on April 4, 2003.

  • By far, the heaviest icing occurred at higher elevations, as was the case with the other two events.

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