NTDA Algorithms Struggling in Terrain

Posted in News on by Brandon Smith.

We noticed several instances this morning in the PIH forecast area where the NTDA algorithm would detect possible TOR’s over mountain and or hill peaks.  This is common with the TVS algorithm and I wonder if there was some sort of rate of change filter that could be passed along to the RF model. It’s something that as a forecaster if you know your CWA well is easy to ignore but if there’s a way to filter those out it would be helpful.  In the two examples shown below, the ridgetops in eastern/central Bingham county are easily shown to be the source of the NTDA at least in the 0.5 degree slice.

Example: Number NTDA objects being displayed over mountain tops.
Example: Number NTDA objects being displayed over mountain tops with reflectivity. The NTDA objects in NW Bingham county appear valid however the objects to the south over central and eastern Bingham are related to terrain and not actual meteorological features.

– Spaceman Spiff