Minutes from first HSLC Conference Call

Minutes for 13 December Conference Call…

1. Call began at 1 PM. Attendees are…
GSP…Pat Moore, Justin Lane, Larry Lee
CAE…Mike Cammarata, Hunter Coleman, Shawn Smith
FFC…Trisha Palmer
CHS…Frank Alsheimer
RAH…Mike Strickler, Jonathan Blaes
RNK…Steve Keighton
AKQ…Chris Wamsley
LWX…Steve Zubrick
NCSU…Matt Parker

[Please let me know if you were on the call but are not on this list. -pat]

2. Reflection upon the 30 November-1 December event and other recent events generated much discussion among the attendees with several excellent insights and opinions shared. One common theme running through the discussion included a need for a better understanding of the near-storm environment around HSLC storms. NWS forecasters have situational awareness of the HSLC environment in general, although sometimes the onset of the event could be anticipated better, which is a concern because of the impact on staffing. NWS forecasters more often lack enough understanding of the near storm environment to differentiate between which storms will produce severe weather (tornadoes) and which will not. Another common theme was the need for better conceptual models of HSLC storms that forecasters could consistently use when evaluating radar signatures during HSLC storm events.

During the discussion, Steve Zubrick indicated that HSLC storms are receiving some attention up in the highest levels of NWS management because of the 17 November Baltimore tornado. He will be making a presentation at NWSHQ concerning the event. He has been in contact with Steve Weiss about the event and indicated that Steve W. might have some interesting severe weather-tornado climatology to share with the group.

3. There was some discussion about Dr. Parker’s vision for CI participation and how that might relate to the work that a Master’s Degree student would perform. The long-range goal of the case studies is to provide a more granular view of what is happening in events and nulls, in order to complement a more longitudinal study of gross statistics that will be undertaken by a M.S. student at NCSU. The longitudinal study will include a large database of environments and a large database of convective modes, but will not address the messy details that are obviously present in individual cases. In a sense, the case studies represent the bridge between the “ingredients-based” forecasting/nowcasting perspective and the “boots on the ground reality” of how these cases unfold and are treated from a WFO perspective.

The case studies should focus on the 0-3 hr time frame from the mesoscale (near storm environment, boundaries, convective parameters) down to the convective scale (radar signatures and warning/no warning decisions), including verification. As such, the case studies would be observationally oriented.

4. Most of the discussion specifically about case studies revolved around what constituted an event vs. what was a “null.” It was generally agreed that null events are difficult to quantify and that on a particular day, one office might experience an event while a neighboring office might not have any events, so an event for one office might be a null for another. [Additional post-call discussion will be conducted as a reply to this blog entry. –pat]

A consensus was reached that thresholds for HSLC environments would be a CAPE of less than roughly 500 J kg-1, and 0-6km shear of at least 35 kt (it was noted that 0-3km shear of at least 30 kt might be better, but this is not routinely available in SPC mesoanalyses). [Brief discussion post-call indicated the threshold should be on SBCAPE as a starting point. –pat]

Important things to include in a case study would include a representative sounding and appropriate radar data. SPC mesoscale analysis graphics for sector 17 are archived at NWS Raleigh.

5. As for how we get started, case selection is job one. It was agreed that the easiest way to get started would be to identify severe weather events from Storm Data, in spite of its inherent biases, and then to determine which of those events were produced in HSLC environments. [post-call discussion reminded the note-taker that CIs should not limit their search only to tornadic activity. We should also look for significant wind damage as well. –pat] This strategy will not be able to identify nulls. However, as a first cut it is too labor-intensive to interrogate archived radar data to find nulls. The work of the NCSU M.S. student may provide an objective way to churn through the data sometime down the road.

It was decided we should plan for another call after the Holidays. Matt Parker indicated that mornings would be better for him, but he had no preference for day of month or day of week.
We would like to set up a routine monthly call. Matt will start another poll on Doodle after the New Year to identify a time and day of the week/month to have the routine call.

In the mean time, CIs at the offices can begin the process of identifying events. The main investigators at each office are…
Sterling… Matthew Kramar
Wakefield… Andrew Zimmerman
Blacksburg… Steve Keighton
Raleigh… Mike Strickler
Charleston… Frank Alsheimer
Columbia… Hunter Coleman
Peachtree City…Steve Nelson, Trisha Palmer
Greenville-Spartanburg…Pat Moore, Justin Lane

We are not sure of the involvement of the Morehead City or Wilmington NWS offices, or if there are other offices that want to participate. Jonathan Blaes will contact MHX and ILM to find out if they are going to participate.

Action items…
Matt Parker…send out Doodle poll after 1 January to determine best time for next call
Jonathan Blaes…contact NWS Morehead City and Wilmington to identify participants, if any
Steve Zubrick…contact Steve Weiss to find out if he could make a presentation (Webinar) for the group about some of his recent work.
Pat Moore…post minutes of call to blog.

About nws-pat moore

B.S. Meteorology, State Univ. of New York - College at Oneonta (1987) M.S. Meteorology, The Florida State University (1996) National Weather Service (12/3/90 to present), stationed at GSP since 8/16/98.
This entry was posted in CSTAR, General Information, High Shear Low Cape Severe Wx. Bookmark the permalink.

4 Responses to Minutes from first HSLC Conference Call

  1. mdparker says:

    Hi All,

    There has been some offline discussion about the specifics of the case selection procedure. Here are some responses, culled from a handful of e-mails that I’ve sent since the teleconference.

    *If a case was a hit in some sense for your CWA, log it, regardless of whether or not it might have been a miss for other CWAs. There will probably be duplicates among CWAs, which are easily sorted out. And, obviously, the actual case studies will span the entire area where HSLC ingredients and/or reports were present (not just one CWA). I’m trying to encourage people to do the digging and list-building first and not get too worried about details of what we keep/discard (or what we call it) just yet.

    *I would say for now that we should hold on to all interesting HSLC cases, regardless of whether they were tornadic or not. For example, down the road it may be useful to separate the tornadic (or significantly tornadic) cases from the others and compare. If we decide down the road that we want to chuck the non-tornadic cases, we have that option. It’s probably easier to find them now and toss them out later than it is to redo the search again trying to find some good non-tor cases.

    *Steve Weiss’s SPC “HSLC” climo plots used MLCAPE to identify “low CAPE”. When we’re talking about tornadoes and penetrative downdrafts, it has to be SBCAPE and/or MLCAPE that matter most. So, I would use that for your first filter. If SBCAPE=400 and MUCAPE=2000 J/kg, I guess we can decide whether we want to include such a case at a later date.

    *Justin Lane has gone through an archive of all their October-May Hazardous Weather Outlooks from 2006-09 and has managed to identify a few potential “true nulls.” (These were situations in which a severe weather potential was mentioned in the Day 1 outlook, but no severe weather was reported anywhere over the Southeast/mid-Atlantic the day of or the day after the HWO was issued.) These events would require further scrutiny before being labeled as “true nulls.” That said, good science really requires having some nulls, and it’s great to have folks digging up a few good candidates to get us started. This will be *very* useful.

    Thanks again to everyone for a very productive call. I will monitor the comments section of this thread so we can use it as a “one stop shop” when it comes to details/concerns about the case identification process.

    Best regards,

  2. Hunter Coleman @ WFO CAE says:

    Thanks for the clarifications and further insights!

  3. justingsp says:

    Just a couple of points I wanted to add, since work interfered with my attendance of the conference call…

    I know we’re in “potential case” identification mode at this point, and don’t want to get bogged down in what a case “is,” but just some food for thought: is it really necessary to define a null event as a situation in which no severe weather occurred? If we defined an “event” as a situation in which widespread severe weather and/or at least one significant event occurred within the area of study, then a null could be defined as a situation in which severe weather did occur, but was marginal and isolated. This would make it easier to identify nulls.

    I think we need to address more than tornadoes in this study. Any “high impact” event should be fair game, whether it be tornadoes, “high end” downbursts, or an event that results in widespread severe weather (of course, that means we’ll have to define “widespread!”)

    As far as the “event in one CWA,” vs. “null in another CWA” topic: although case identification needs to occur on a CWA-by-CWA basis, once we’ve identified the potential case studies and begun the filtering process, us NWS folks are going to have to pretend that these arbitrary boundaries do not exist. If a severe weather episode meeting our criteria occurs anywhere within the Southeast/mid-Atlantic region, it’s an event, whether it occurred in one or all of the participating CWAs. As I believe Matt alluded to in the call, one of our goals should be to define a set of atmospheric ingredients resulting in an HSLC event. If an event is confined to a relatively small portion of our study area, it is presumed that all of the necessary ingredients existed only in that area.

  4. Jeff Waldstreicher says:

    Just a heads up…There are some very active discussions going on between SPC and EMC regarding how CAPE (all flavors) is being calculated. There is a very strong push to change all of the calculations to use virtual temperature (Tv) rather that regular temperature (T). See Doswell and Rasmussen December 1994 Weather & Forecasting for details. There may come a time – maybe as early as next severe wx season, that this change is made for the SPC mesoanalysis page and/or NCEP model output (the preference is to do everything together – keep things uniform). This Tv change could have important ramifications for any CAPE thresholds you might set for this endeavor. Steve Weiss can provide additional info/details.


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