Feb28-Mar1 HSLC event

CAE certainly appeared to be affected by an HSLC event Monday evening.  A line of convection developed to our west and pushed into our forecast area just prior to 00z/0301 with what looked like a classic broken-S signature along the line as it pushed across Newberry County, SC.  The environment over our forecast area based on SPC mesoanalysis showed SBCAPE values less than 200 J/kg, MLCAPE around 250 J/kg, MUCAPE around 500 J/kg, with 0-6km Shear values of 60-80 knots and 0-1km Shear around 40 knots.

We received numerous reports of wind damage across the forecast area and a couple of reports of a tornado in the Silverstreet area.  A storm survey revealed EF1 damage just north of Silverstreet with classic microburst damage in the town of Silverstreet.  I was working the radar during the event and it was very interesting to see that there were two main broken-S signatures along the line, the one in Newberry and another that developed later to the north across our northern counties, which did not produce any tornado damage.  The signature that moved through Newberry and “broke” then became linear again as it went through Columbia and then again became a broken-S as it moved through Sumter County which also did not produce any tornado damage and not even any wind damage reports that we could find.  I have attached a few radar images from GR2 Analyst.

The office writeup of this event can be found here.

Hunter Coleman
WFO CAE

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5 Responses to Feb28-Mar1 HSLC event

  1. Chris Wamsley says:

    Hunter,

    Interesting second and fourth image…notice the high reflectivity on the northern flank of the broken area of the line. Are these two images where the tornado or microburst developed (since I am not familiar with the counties) ?

    -Chris

  2. Hunter Coleman @ WFO CAE says:

    Chris,

    Sorry, I guess it is not that clear is it! In the second image, the circulation couplet was associated with the high reflectivity area north of the apex where the S is “breaking”. The forth image is a different broken S along the line, further north, about 30 minutes later. No tornado associated with this one, only wind damage reports.

    Hunter

  3. Chris Wamsley says:

    I think having the area of higher reflectivity (more than Gail’s earlier post) leads to when we should warn and when we should use more caution. This high reflectivity on the northern flank is what I usually look for when to warn (esp tornado) in our area just to the south of it.

  4. nws-pat moore says:

    Hunter…

    Thanks for sharing those interesting images. My impression is that more is going on here than in your typical “broken-S” event. This is more like some kind of “super-broken-S” because there is more than one inflow notch ahead of the QLCS and more than one weak echo channel behind it. It almost looks to me like a broken-S with a supercell embedded in the northern segment of the line. Either way, the SRM image was very interesting with its two cyclonic couplets and one anticyclonic couplet. Very funky.

    Did you have a tornado warning out for this part of the line? What did you use for the basis of the warning?

    We issued a tornado warning for Greenwood County, but could not find any tornado damage. Our survey reached the conclusion of straight line winds in Greenwood County.

    -pat

  5. Hunter Coleman @ WFO CAE says:

    Pat –

    Yes, it was a very interesting event working the radar. Your comment about “looks to me like a broken-S with a supercell embedded in the northern segment of the line” was interesting. I agree with you that there were some unique things occurring within this line and feature. I went with our WCM and did a survey of damage reports in Newberry county and we found EF1 damage on the northern end of the segment where you suggest a supercell may have been, and then very strong straight line wind damage southeast of the EF1 damage just north of where the “S” broke. Another interesting note is that the strongest cyclonic couplet actually occurred in northern Saluda County south of the “break in the S” and when we drove all around down there, we could not find anything at all other than just twigs in the road, but no trees down or other damage indicating anything occurred down there.

    I did have a little larger than I would normally issue tornado warning for the southern part of Newberry and northern Saluda (encompassing both couplets) as there was some uncertainty as to what was really going on.

    Hunter

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