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
Talk Outline 1. Background 2. Synoptic Overview 3. MC2 Simulation Results 4. Conclusions
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 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 The October 15-16, 1954 Storm, “Hurricane Hazel” in Ontario.
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
Figs. (a)-(d): SLP (hPa) 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 = m 2 s -1 K kg -1 Ertel’s Potential Vorticity (PV) (Ertel 1942):
Figs. (a)-(d): DT Winds and and 850 hPa 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
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)
Tracks of Hurricane Hazel
SLP Comparison 15 UTC 15 October top: Palmen’s analysis lower left: MC2 lower right: Anthes
SLP Comparison 3 UTC 16 October top: Palmen’s analysis lower left: MC2 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