‘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. Of particular interest are those trajectories that, prior to their arrival in Canada, originated over northwestern and southern USA and Mexico, anywhere diamondback moth populations overwinter and adults are actively migrating. If diamondback adults are present in the air currents that originate from these southern locations, the moths may be deposited on the Prairies at sites along the trajectory, depending on the local weather conditions at the time that the trajectories pass over our area (e.g. rain showers, etc.). Reverse trajectories are the best available estimate of the ''true'' 3D wind fields at a specific point. They are based on observations, satellite and radiosonde data.
‘Forward trajectories’ (FT) have a similar purpose; however, the modelling process begins at sites in USA & Mexico. The model output predicts the pathway of a trajectory. Again, of interest to us are the winds that eventually end up passing over the Prairies.
Ross Weiss (AAFC), Meghan Vankosky (AAFC) and Serge Trudel (ECCC)
DATE: APRIL 8, 2019
1. Reverse trajectories (RT):
a. Pacific Northwest (PNW) – For the period of April 2-8 there have been 69 RT’s (originating over the PNW) that have crossed over prairie locations. Since March 23rd Lethbridge has reported the highest number of PNW RT’s (n=9), followed by Olds AB, Beiseker AB and Dauphin MB (n=6).
List of PNW Reverse trajectories that have crossed the prairies (Since March 23, 2019):
The following maps present two examples of April 7, 2019 RT’s. The first map indicates that the RT crossing Tisdale originated across southern TX. The second map shows that two RT’s crossed over Regina. The red line indicates that this RT originated over southern TX. A second RT originated across central CA.
Tisdale SK, April 7, 2019
Regina SK, April 7, 2019
2. Forward trajectories (FT) –
The following table reports the origin of forward trajectories predicted to cross the prairies over the next five days. Forward trajectories, originating over Santa Maria, CA are predicted to pass over SK and MB in the next five days.