20th Conference on Weather Analysis and Forecasting/16th Conference on Numerical Weather Prediction


A reanalysis of Hurricane Hazel (1954)

Scott R. Weese, McGill University, Montreal, QC, Canada; and R. McTaggart-Cowan and J. R. Gyakum

Hurricane Hazel struck North America on 15-16 October 1954, leaving a pattern of heavy rainfall and flooding in its wake. A complete analysis of the synoptic-scale conditions associated with this extratropical transition was first undertaken to discern the dynamic and thermodynamic elements crucial to the intensification of this storm.

An analogue search was then conducted for Hazel, with cases being found in 1985, 1995 and 1999. A comparison of these analogues to Hazel yielded the conclusion that Hazel is a unique event in recent meteorological history, as none of the analogues produces the extreme precipitation values in Hazel. The lack of significant hurricane circulations in all of the analogues is the important difference, as Hazel provides important moisture and latent heating that are absent in the analogues.

Finally a mesoscale modeling study was carried out to test the sensitivity of Hazel to improved vortex structure and increased horizontal resolution. Specification of the vortex led to a dramatic improvement in the simulation results, as precipitation and track closely mimicked the observed values. Enhancing the horizontal resolution to 12 km did not improve upon the 36 km specified vortex simulation. Tracking of the storm slowed considerably as the development of an upper tropospheric cutoff circulation was diminished in the 12 km run. The parameterizations governing the interaction between the diabatic outflow from Hazel and dynamics of the midlatitude trough are poorly modeled in this situation, and lead to the severe time lag in the path of Hazel.

Poster Session 1, Monday Posters
Monday, 12 January 2004, 2:30 PM-4:00 PM, Room 4AB

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