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

2. Talk Outline 1. Background 2. Synoptic Overview 3. MC2 Simulation Results 4. Conclusions

3. Purpose: to study the 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

4. 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.

5. Synoptic Overview Considering the time between October 15th at 00z to October 16th at 12z 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

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

7. 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):

8. Figs. (a)-(d): DT Winds and  and 850 hPa  00 UTC 15 to 12 UTC 16 October

9. 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

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

11. MC2 Simulation Using MC2 (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)

12. Tracks of Hurricane Hazel

13. SLP Comparison 15 UTC 15 October top: Palmen’s analysis lower left: MC2 lower right: Anthes

14. SLP Comparison 3 UTC 16 October top: Palmen’s analysis lower left: MC2 lower right: Anthes

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

16. Precipitation Comparison, 15 October

17. 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