A Reanalysis of Hurricane Hazel 1954 Scott Weese

A Reanalysis of Hurricane Hazel (1954) Scott Weese, Ron Mc. Taggart-Cowan and John R. Gyakum Department of Atmospheric and Oceanic Sciences Mc. Gill University Montreal, Quebec, Canada June 4 th, 2003

Talk Outline 1 2 3 4 . . Background Synoptic Overview MC 2 Simulation Results Conclusions

Purpose: to study thermodynamic and dynamic properties of one of the most deadly and costly weather disasters to strike southern Ontario • Hazel struck Ontario on 15 -16 October 1954 • rains led to flooding in Humber, Credit and Don River valleys situated near Toronto, and in the Holland Marsh north of Toronto • over 80 fatalities, and $175 million damage was done by Hurricane Hazel in Ontario

Track of Hurricane Hazel Reference: Mason, A. H. , M. K. Thomas and D. W. Boyd. 1955. The October 15 -16, 1954 Storm, “Hurricane Hazel” in Ontario.

Synoptic Overview • Considering the time between October 15 th at 00 z to October 16 th at 12 z as this is the period of the most intense rainfall in southern Ontario • Using the NCEP reanalysis data (Kalnay et al. 1996) to generate fields of interest

Figs. (a)-(d): SLP (h. Pa) and Thickness (dam) 00 UTC 15 to 12 UTC 16 October

Dynamic Tropopause Maps • The dynamic tropopause is defined as the 1. 5 PVU surface • 1 PVU = 10 -6 m 2 s-1 K kg-1 • Ertel’s Potential Vorticity (PV) (Ertel 1942):

Figs. (a)-(d): DT Winds and q, and 850 h. Pa q 00 UTC 15 to 12 UTC 16 October

Coupling Index, Equivalent Potential Temperature and Precipitable Water • Coupling Index (CI) is a measure of bulk atmospheric stability (Bosart and Lackmann 1995) • Values of CI < 10 suggest convective instability • Precipitable water is the column integrated water vapour

Figs. (a)-(d): Coupling Index and Precip. Water (mm) 00 UTC 15 October to 12 UTC 16 October

MC 2 Simulation • Using MC 2 (Mesoscale Compressible Community Model) to simulate Hazel • NCEP Reanalysis data utilized for the initial and boundary conditions • following the work of Palmen (1958) and Anthes (1990) • test sensitivity of Hazel to improved vortex structure using model by Kurihara (1993), and increased spatial resolution (36 km)

Tracks of Hurricane Hazel

SLP Comparison 15 UTC 15 October top: Palmen’s analysis lower left: MC 2 lower right: Anthes

SLP Comparison 3 UTC 16 October top: Palmen’s analysis lower left: MC 2 lower right: Anthes

Knox’s Jump SLP for 21 UTC 15 October to 03 UTC 16 October

Precipitation Comparison, 15 October

Conclusions • Successfully reproduced transformation of Hazel with accompanying frontogenesis and heavy precipitation over U. S. • Improved vortex structure and increased spatial resolution necessary for successful mesoscale modeling of Hazel