We receive two types of model output from ECCC: reverse trajectories (RT) and forward trajectories (FT):
(i) ‘Reverse trajectories’ (RT) refer to air currents that are tracked back in time from specified Canadian locations over a five-day period prior to their arrival date.
(ii) ‘Forward trajectories’ (FT) have a similar purpose; however, the modelling process begins at sites in USA and Mexico. The model output predicts the pathway of a trajectory. Again, of interest are the winds that eventually end up passing over the Prairies.
Since April 1. 2018, the majority of Pacific Northwest (PNW) air currents have crossed over southern AB (Fig. 1). The cumulative number of wind dispersal events for June 1 - 11, 2018 (181) is greater than the long term (2007 - 2017) average (98).
|Figure 1. Total reverse trajectories (originating from US - PNW) April 1 - June 11, 2018.|
Since April 1, the majority of air currents from southwest USA and Mexico have crossed over eastern SK and western MB (Fig. 2). So far there have been 18 RT’s (June 1 - 11, 2018) and compares with 2017 (3) and the long term average (24).
|Figure 2. Total number of reverse trajectories (originating from southern USA) April 1 - June 11, 2018.|
Weather forecasts (7 day):
Grande Prairie: https://weather.gc.ca/city/pages/ab-31_metric_e.html