Former Hurricane Earl reintensified rapidly while traveling through Canadian waters in September 1998. Its central pressure decreased 40 hPa over a 36-h period, and it produced heavy rain on Cape Breton Island, Nova Scotia, and over Newfoundland. A diagnostic study is conducted from a potential vorticity (PV) perspective using Canadian Meteorological Centre (CMC) regional analysis data. Former Hurricane Earl's rapid redevelopment was related to the interaction between two preexisting positive PV anomalies: a diabatically generated low-level anomaly and an upper-level anomaly. This process was accompanied by a cold air intrusion and warm air “wrapping up” process. As well, the behavior of the operational CMC numerical weather prediction models is examined using output from the ensemble forecast system (giving 10-day forecasts, with eight members and one control run) integrated from three different initial times (0000 UTC on each of 3, 4, and 5 September 1998). Some members failed to maintain forme... Abstract Former Hurricane Earl reintensified rapidly while traveling through Canadian waters in September 1998. Its central pressure decreased 40 hPa over a 36-h period, and it produced heavy rain on Cape Breton Island, Nova Scotia, and over Newfoundland. A diagnostic study is conducted from a potential vorticity (PV) perspective using Canadian Meteorological Centre (CMC) regional analysis data. Former Hurricane Earl's rapid redevelopment was related to the interaction between two preexisting positive PV anomalies: a diabatically generated low-level anomaly and an upper-level anomaly. This process was accompanied by a cold air intrusion and warm air “wrapping up” process. As well, the behavior of the operational CMC numerical weather prediction models is examined using output from the ensemble forecast system (giving 10-day forecasts, with eight members and one control run) integrated from three different initial times (0000 UTC on each of 3, 4, and 5 September 1998). Some members failed to maintain forme...

This is a review article invited by Atmosphere-Ocean to document the contributions of Recherche en Prévision Numérique (RPN) to Numerical Weather Prediction (NWP). It is structured as a historical review and documents RPN’s contributions to numerical methods, numerical modelling, data assimilation, and ensemble systems, with a look ahead to potential future systems. Through this review, we highlight the evolution of RPN’s contributions. We begin with early NWP efforts and continue through to environmental predictions with a broad range of applications. This synthesis is intended to be a helpful reference, consolidating developments and generating broader interest for future work on NWP in Canada.

A three-dimensional shelf circulation model is used to simulate the seasonal variability of circulation and hydrography on the Scotian Shelf over the eastern Canadian seaboard. The model is a modified form of an operational forecast system known as DalCoast3. The model is forced by forecast winds and atmospheric pressure produced by GEM, a Canadian numerical weather prediction model. Climatological temperature and salinity are used to initialize the model, and as lateral open boundary inputs. The monthly mean currents from a baroclinic circulation model of the northwest Atlantic Ocean are used as inputs to represent remotely forced flows. A new data assimilation method developed by Thompson et al. (2006b) is used to constrain model temperature and salinity to their respective climatologies, while allowing short-term (O(days)) variations to evolve prognostically. The model produces southwestward flows along the Nova Scotian coast and along the shelf break, which have been observed in the past. The pattern of simulated volume transport over the Scotian Shelf is qualitatively similar to those from past model studies, and the transport across a section on the inner shelf is also comparable to values calculated from observations.

A three-dimensional numerical shelf circulation model is used to examine the effect of the seasonal variation in water column stratification on the tidal circulation over the Scotian Shelf and the Gulf of St. Lawrence. The model is driven at its lateral open boundaries by tidal forcing expressed in terms of sea surface elevations and depth-averaged currents for five tidal constituents (M₂, N₂, S₂, K₁, and O₁). Three numerical experiments are conducted: the control run (including the full suite of forcings and dynamics), a barotropic run, and one that is similar to the control run but without the baroclinic pressure gradients. Each model run lasts one year and is preceded by a spin-up period of four months that is initialized with climatological hydrographic states. The focus of this study is on the semi-diurnal tide M₂, which is one of the dominant tidal constituents in this region. Comparison of model results in the three experiments suggests that the seasonal variation in stratification affects the M₂ tidal circulation along the shelf break and over the deep waters off the Scotian Shelf through its influence on the baroclinic pressure gradient, and affects the M₂ tidal circulation in Northumberland Strait (in the Gulf of St. Lawrence) through its influence on vertical mixing and bottom stress.

Dr. Keith Thompson was a highly influential scientist in marine prediction and environmental statistics in Canada and abroad. He was also exceptionally successful for providing high-quality mentorship to graduate students and early-career scientists. In this article, we provide an overview of Dr. Thompson’s career contributions to marine science programs and training for graduate students and other highly qualified personnel.