HSLC Idealized Hodograph Sensitivity Studies: Overview of all 12 Simulations

During the July conference call, I presented preliminary work from a matrix of 12 simulations geared towards exploring the sensitivity of HSLC convection to low-level hodograph shape and the wind profile’s orientation relative to an initiating cold pool. As I focused on only four of the 12 simulations, one of the requests stemming from discussion during the call was to see simulated reflectivity, cold pool, vertical vorticity, and vertical velocity animations in addition to rotation track Hovmoller plots for all 12. These are attached as a set of powerpoint slides at the end of this post, along with a refresher of the hodographs used in this study.

12pan_overview

Snapshot of all 12 simulations at t = 100 min. Animations are available in the attached powerpoint.

Ultimately, the four “core” simulations discussed during the July conference call (control L-shaped, CCW ball cap, control quarter turn, and control spatula) exhibit the most realistic and representative HSLC convection. However, interesting features are shown in the other simulations, including situations with overrunning convection and shear-parallel bands of convection. Some of the simulations not included in the core set still produce strong near-surface rotation and may be worth future investigation.

Further analysis and discussion, particularly on the four core simulations, is provided in an extended abstract associated with a recent presentation of this work at the AMS Mesoscale Conference. A link to this document will be provided in an upcoming blog.

Powerpoint: hodo_12pans

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2 Responses to HSLC Idealized Hodograph Sensitivity Studies: Overview of all 12 Simulations

  1. Jonathan Blaes @ WFO RAH says:

    Keith,

    Thanks for sharing the animation on slide 2 in your power point. The loops are intoxicating!

    Can you comment on the differences between convective evolution when looking at wind profiles relative to the initiating cold pool or bulk wind shear vectors relative to the convection as noted in some of the Schaumann and Przybylinski work. How are these similar and different?

    JB

    • Keith Sherburn says:

      Hi JB,

      The two certainly aren’t independent of one another.

      Perhaps the primary difference is that the initiating cold pool and the initial wind profile relative to it are somewhat static in nature. In other words, the initial cold pool in these simulations is a relatively uniform block of cold air oriented due north-south. Early in the simulations, the cold pool can still be approximated in this fashion; therefore, we can speculate based upon the relative wind profile what the resulting convection’s organization will be or what is its potential to move off of this initiating boundary. Provided convection remains tied to the initial boundary (or even a separate, system-generated cold pool), the “wind profile relative to the cold pool” or “bulk wind shear vectors relative to the convection” arguments are really one and the same, at least until the system begins to develop more of a 3D structure with embedded bowing features, embedded supercells, etc.

      If convection can move off of the initial boundary, or once 3D structure emerges, the relationship gets a little more fuzzy. In this situation, the wind profile relative to the initial cold pool may have a lower priority than the bulk wind shear vectors relative to the convection, especially if the convection has its own distinct cold pool that may or may not be oriented in the same fashion as the initiating boundary.

      Depending on the situation, I think the general arguments such as RKW theory, potential for discrete cells or cell interactions given bulk shear vector orientation, ingestion of streamwise vorticity based upon the hodograph, and the like can be addressed in one or the other framework. However, in general, I don’t believe either can be used independently, particularly before the event begins.

      One of the ideas I hope to hit home after additional work is that although shear vector magnitude and orientation are often used when attempting to forecast the potential of severe convection, the hodograph (especially in the low levels) should also be interrogated to determine the potential for rotating updrafts.

      Thanks for the comments,
      -Keith

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