TORP Assessment in a Western US Case

When examining a TORP case in the western US, there were many detections that occurred along the mountain ranges. However, when “aggressive auto filtering” was turned on, all of these “bad” detections were removed:

Velocity plot with TORP objections. A 20% prob filter was applied to TORP objects, but without aggressive auto filtering there were many detections along the mountain range.
The same velocity plot with TORP objections using a 20% prob filter and aggressive auto filtering. All of the seemingly bad TORP detections were removed.

In AWIPS, one thing that I found useful, at least as someone unfamiliar with the area and its terrain, was loading the HiRes Topo map beneath the TORP detections. I had to increase the line width of the TORP objections, but they displayed well on top of the HiRes Topo map:

TORP objections overlaid on a HiRes Topo map in AWIPS

Here is a signature that caught my eye, a bit of an elongated area of increasing convergence/divergence along a line segment in the northern part of the CWA:

A four panel display with TORP/HiResTopo (upper left), Reflectivity (upper right), DivShear (bottom left), and AzShear (bottom right).

Here is an example of how an AWIPS display looked around the time of a possible tornado. Velocity shows only a weak couplet. TORP had a weak track, but the current probability at the time of the tornado was just 30%.

A velocity plot with a TORP detection and track at the time of a possible tornado report.

I did not have a warning out at the time of the possible tornado (pictured above). But later at 2140z I decided to hoist a warning despite no TORP objection showing up. The same storm was producing weak rotation in velocity further south, and AzShear had a decent signal in those same locations:

Weak rotation in the velocity field at 2140z
AzShear showing weak couplets at 2140z.

In a subsequent scan at 2144z (not pictured) the velocity and AzShear signatures appeared to increase slightly, but TORP still did not have a detection for this area (this even after turning off any QC filters and reducing the probability filter to 10%).

-Orange Lightning

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