EWP Blog

A line of enhanced reflectivity moving toward the LWX radar likely tapping into stronger low level wind fields with strong base velocity values prompting me to issue a severe warning but Torp identifying an object with some interesting AZShear data couplets. Given the environment and this QLCS event the Torp value and its trend increasing adds confidence to add a tor possible tag.

Flash

Noting a few spurious maxes seen in Az and Div Shear. It’s good to see that TORP correctly ignores these areas.

-Nimbus

DivShear showing increasing convergence along the line, particularly through Loudoun County. This also coincides with a number of low TORP probability objects that have also popped up here. -Sidney Crosby

An initial Torp object was detected with a 31% probability northwest of LWX with a slightly enhanced AzShear. However, the reflectivity data was unimpressive as we might expect in this environment with weak instability and velocity was also unimpressive. The next scan it was not there anymore (using a 30% filter for Torp). Not sure what it may have been pinging on and appears to be of little concern ultimately.

Flash

Noticing a DivShear couplet in central Fauquier county indicating convergence. A TORP object with 34% probability also was created in the same area. These products coincide with a surge in the line seen on reflectivity. -Sidney Crosby

Noticing several AzShear and DivShear couplets behind the reflectivity line that aren’t seemingly associated with any areas of interest so far. -Sidney Crosby

Here are some example images from our first archived case, showing 0.3 base velocity, the AzShear and DivShear displays in AWIPS, and an MRMS four panel:

Here is an image of the same storm using the PHI Tool:

Here are a few more images from much later in the event. The first shows the MRMS 4 Panel with a strong low-level rotation track. The second shows the TORP values have remained right around 100% for the main object. A second object is being detected (pictured below), however on the next update these are merged into just the main object (not pictured).

Finally, here is a look at a supercell in the eastern part of the JAN CWA. It is almost 95 miles from the DGX radar, but has a supercellular appearance and given the environment may be a candidate for a tornado warning. However, both ProbTOR (2%) and TORP (26%) are generally low values. TORP has largely been below 30% for the last 20-30 minutes, although this is near the edge of the typical TORP range.

-Orange Lightning

Excellent example of AzShear highlighting an area of rotation (western circle) before legacy velocity data indicated a significant threat. Subsequent velocity scans after the inserted example continued to indicate strengthening. If I was the warning forecaster, knowing the given atmospheric setup and mesoscale conditions, the AzShear would have resulted in me issuing a tornado warning 1 to 3 minutes earlier than I would have if basing the decision purely on the velocity data.

-Oppenheimer

ProbSevere sometimes combines two areas of the storm into one overlay. This hides relevant info for one of the circulations. It’s nice to see Torp specifically highlight both of these regions separately.

-Nimbus

A look at AzShear for the downstream tornado warning shows a signal but doesn’t appear quite as defined as it did previously. Notably, the storm behind it is starting to show a better signature. Torp probabilities remain very high (>90%). -Sidney Crosby