Data and code from: Variability in high-shear, low-CAPE QLCS environments in the southeastern United States
Data files
Sep 16, 2026 version files 10.44 GB
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All_Cases.zip
10.43 GB
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Composite_Soundings.zip
4.38 MB
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Convective_Line_Point_Data_CSVs.zip
123.63 KB
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Other_Files.zip
26.45 KB
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README.md
33.94 KB
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Scripts.zip
1.65 MB
Abstract
High-shear, low-CAPE (HSLC) quasi-linear convective systems (QLCSs) in the Southeastern United States pose a challenge to operational forecasters. Prior studies have investigated bulk environmental ingredients associated with the severe weather produced by these systems; however, there is spatial and temporal variability in HSLC severe weather from QLCSs that has yet to be explained. This study sought to improve the conceptual model for HSLC QLCSs by characterizing heterogeneities in their environments. In pursuit of this goal, QLCS-relative analyses that incorporate hourly data spanning the full duration of 79 HSLC QLCS events occurring across the Southeastern U.S. were created using archived operational High-Resolution Rapid Refresh (HRRR) model data. 'All case' composites reveal that HSLC environments are not uniformly "low-CAPE", and HSLC QLCSs may be partially fed by elevated "most unstable" parcels. Additionally, comparisons of different QLCS regimes show greater bulk shear magnitudes along the poleward portions of the QLCS convective lines during tornadic hours, which may explain the poleward bias of QLCS tornado reports noted by prior studies. A strong correlation was also identified between low-level nocturnal stabilization and the enhancement of both the low-level jet and low-level vertical wind shear. These enhancements could account for the prevalence of nocturnal tornadoes produced by these systems. Finally, the potential response to diabatic heating (i.e., low-level flow enhancements) may contribute to increased bulk shear magnitudes during the mature phase of these systems, which could help address the noted time lag between system formation and the occurrence of the first tornado reports.
Dataset DOI: 10.5061/dryad.cfxpnvxnk
Description of the data and file structure
This dataset contains the data and samples of code utilized for AMS Weather and Forecasting publication “Variability in High-Shear, Low-CAPE QLCS Environments in the Southeastern United States” (Chalmers and Parker 2026). The study investigated environmental variability within the pre-line environment of 79 cool season high-shear, low-CAPE (HSLC) quasi-linear convective system (QLCS) events occurring within the southeastern United States. Data were collected from the archive of the operational High-Resolution Rapid Refresh (HRRR) convection-allowing model. Data points that are contained within this dataset were collected along a manually drawn convective line for every hour of every case at several known, set distances ahead of the QLCS in order to construct a line-relative coordinate system (including both line-parallel and line-perpendicular coordinates). The provided spreadsheets also contain information on each QLCS and QLCS hour, including characteristics such as tornadic vs. non-tornadic, time of day, etc. Data points were also used to generate composite soundings, which are also provided within the dataset. Lastly, a sample of calculation and plotting scripts are provided.
Please contact the corresponding author with any questions or comments.
Article DOI: https://doi.org/10.1175/WAF-D-25-0137.1
Corresponding author contact: zachary.chalmers@noaa.gov
Files and variables
File: Other_Files.zip
Description: Contains several database spreadsheets (.csv files) that provide additional hourly and case information for each QLCS. All times are in UTC. Duration is reported in hours, and line length is reported in meters (m). A list of other columns that utilize numerical identifiers is provided below:
Tornado Reports: Signifies if a QLCS case or case hour was (1) or was not (0) associated with at least 1 tornado report. For case hours, a tornado report must have occurred any time during the following hour (i.e., a QLCS case hour at 11 UTC would be considered tornadic if a tornado report occurred any time between 11-12 UTC). A full case was considered tornadic if at least one tornado report occurred during the entire duration of the case (i.e., at least one case hour during the case was tornadic).
Stage: Represents the stage of formation of the QLCS, including Forming (1), Mature (2), and Dissipating (3) hours. Forming hours were defined as convective lines that were increasing in line length; mature hours included those where the line length was relatively steady, and dissipating hours included hours where the line length was a) decreasing or b) exhibiting weakening wherein the reflectivity values within the convective line decreased below 40 dBZ over a majority of the convective line regardless of the line length tendency.
Included Files:
QLCS_Cases_Case_Data (CSV): CSV file containing data for each of the cases that were used for final analysis. This file is needed when creating subset comparison scripts within the Main Plotting Script.
QLCS_Cases_Hourly_Data (CSV): CSV file containing data for each of the case hours that were used for final analysis. This file is needed when creating subset comparison scripts within the Main Plotting Script.
QLCS_Cases_Case_Data_Unfiltered (CSV): CSV file containing data for all of the cases, including those not used for final analysis. The entry "*Removed" is included in Column L to indicate which cases were removed and not included in the final analysis.
QLCS_Cases_Hourly_Data_Unfiltered (CSV): CSV file containing data for all case hours, including those not used for final analysis.
File: Convective_Line_Point_Data_CSVs.zip
Description: This folder includes individual .csv files (one per case) that consist of the original, manually plotted points drawn using the Convective Line GUI (including info on the case number, year, month, day, hour (UTC), latitude, and longitude for each point). These points were later connected linearly to construct a representation of the leading edge of the convective line at each hour.
File: Composite_Soundings.zip
Description: Contains the composite sounding data calculated using the original 50 hybrid model levels from the HRRR in netCDF format, with individual files for each data subset (e.g., All Hours, Tornadic Hours, Nighttime Hours, etc.). All variables (e.g., pressure, temperature, etc.) are split into two variables: mean and median. Variables are also divided based on the grid cell that each composite sounding represents (e.g., 0-10% LLP at 50 km ahead of the convective line). A sample of the available variables within the Composite Sounding netCDF files is provided below.
| Variable Name | Unit |
|---|---|
| Hybrid Level | unitless |
| Mean Pressure_0-10_0km | hPa |
| Median Pressure_0-10_0km | hPa |
| Mean Theta_0-10_0km | K |
| Median Theta_0-10_0km | K |
| Mean Qv_0-10_0km | kg/kg |
| Median Qv_0-10_0km | kg/kg |
| Mean Height_0-10_0km | m AGL |
| Median Height_0-10_0km | m AGL |
| Mean U_0-10_0km | m/s |
| Median U_0-10_0km | m/s |
| Mean V_0-10_0km | m/s |
| Median V_0-10_0km | m/s |
| Mean Temperature_0-10_0km | deg C |
| Median Temperature_0-10_0km | deg C |
| Mean Dewpoint_0-10_0km | deg C |
| Median Dewpoint_0-10_0km | deg C |
***Note that the other available fields can be accessed by adjusting the numbers within the variable field name. For example:
“Mean Pressure_0-10_0km” is the array of mean pressure values for all 50 hybrid levels for the 0-10% LLP grid cell at 0 km ahead of the convective line. Adjust ‘0-10’ within the variable name to access other LLP ranges (0-10, 10-20, 20-30, 30-40, 40-50, 50-60, 60-70, 70-80, 80-90, 90-101) and adjust ‘0km’ within the variable name to access other distances ahead of the convective line (0, 10, 20, 30, 40, 50, 75, 100, 125, 150, 175, 200).
File: All_Cases.zip
Description: Contains the point data (in netCDF file format) utilized for the grid cell plots from all case hours (one file per each case hour) that were incorporated in the final analysis. The following tables list the dimensions, available variables, and units. Note: see additional information provided below the tables regarding variables with an asterisk (*) next to their name.
Dimensions:
| Dimension Name | Size |
|---|---|
| Hybrid Levels | 50 |
| DateTime | 1 |
| Distances | 12 |
| Points | Varies by file |
Variables:
| Variable Name | Dimensions | Units |
|---|---|---|
| Time | DateTime | YYYY-MM-DD HH:MM UTC |
| Distances | Distances | km |
| Points | Points | unitless |
| Hybrid Level | Hybrid Levels | unitless |
| Pressure | DateTime, Points, Distances, Hybrid Levels | hPa |
| Temperature | DateTime, Points, Distances, Hybrid Levels | K |
| Specific Humidity | DateTime, Points, Distances, Hybrid Levels | kg/kg |
| Geopotential Height | DateTime, Points, Distances, Hybrid Levels | gpm |
| U | DateTime, Points, Distances, Hybrid Levels | m/s |
| V | DateTime, Points, Distances, Hybrid Levels | m/s |
| *W | DateTime, Points, Distances, Hybrid Levels | Pa/s |
| Total Hydrometeor Mixing Ratio | DateTime, Points, Distances, Hybrid Levels | kg/kg |
| Turbulent Kinetic Energy | DateTime, Points, Distances, Hybrid Levels | J/kg |
| Surface Temperature | DateTime, Points, Distances | K |
| Surface Pressure | DateTime, Points, Distances | hPa |
| Orography | DateTime, Points, Distances | gpm |
| Freezing Level Height | DateTime, Points, Distances | gpm |
| Composite Reflectivity | DateTime, Points, Distances | dBZ |
| Total Cloud Cover | DateTime, Points, Distances | % |
| MSLP | DateTime, Points, Distances | Pa |
| Latitude | DateTime, Points, Distances | Degrees |
| Longitude | DateTime, Points, Distances | Degrees |
| Boundary Layer Height | DateTime, Points, Distances | m |
| Wind Speed | DateTime, Points, Distances, Hybrid Levels | m/s |
| Wind Direction | DateTime, Points, Distances, Hybrid Levels | Degrees |
| Relative Humidity | DateTime, Points, Distances, Hybrid Levels | % |
| Dewpoint | DateTime, Points, Distances, Hybrid Levels | K |
| Mixing Ratio | DateTime, Points, Distances, Hybrid Levels | kg/kg |
| Potential Temperature | DateTime, Points, Distances, Hybrid Levels | K |
| Virtual Potential Temperature | DateTime, Points, Distances, Hybrid Levels | K |
| *Vertical Velocity | DateTime, Points, Distances, Hybrid Levels | m/s |
| Wet Bulb Temperature | DateTime, Points, Distances, Hybrid Levels | K |
| Equivalent Potential Temperature | DateTime, Points, Distances, Hybrid Levels | K |
| 1000-700 mb Theta-e Gradient | DateTime, Points, Distances | K/km |
| 1000-500 mb Theta-e Gradient | DateTime, Points, Distances | K/km |
| 700-500 mb Theta-e Gradient | DateTime, Points, Distances | K/km |
| 1000 mb Geopotential Height | DateTime, Points, Distances | m |
| 925 mb Geopotential Height | DateTime, Points, Distances | m |
| 850 mb Geopotential Height | DateTime, Points, Distances | m |
| 700 mb Geopotential Height | DateTime, Points, Distances | m |
| 600 mb Geopotential Height | DateTime, Points, Distances | m |
| 500 mb Geopotential Height | DateTime, Points, Distances | m |
| 400 mb Geopotential Height | DateTime, Points, Distances | m |
| 300 mb Geopotential Height | DateTime, Points, Distances | m |
| 200 mb Geopotential Height | DateTime, Points, Distances | m |
| Line Length Percentile | DateTime, Points, Distances | % |
| Raw Distance from Gulf | DateTime, Points, Distances | km |
| 20 m Temperature | DateTime, Points, Distances | K |
| 500 m Temperature | DateTime, Points, Distances | K |
| 1 km Temperature | DateTime, Points, Distances | K |
| 1.5 km Temperature | DateTime, Points, Distances | K |
| 3 km Temperature | DateTime, Points, Distances | K |
| 5 km Temperature | DateTime, Points, Distances | K |
| 6 km Temperature | DateTime, Points, Distances | K |
| 850 mb Temperature | DateTime, Points, Distances | K |
| 700 mb Temperature | DateTime, Points, Distances | K |
| 500 mb Temperature | DateTime, Points, Distances | K |
| 20 m Mixing Ratio | DateTime, Points, Distances | g/kg |
| 500 m Mixing Ratio | DateTime, Points, Distances | g/kg |
| 1 km Mixing Ratio | DateTime, Points, Distances | g/kg |
| 1.5 km Mixing Ratio | DateTime, Points, Distances | g/kg |
| 3 km Mixing Ratio | DateTime, Points, Distances | g/kg |
| 5 km Mixing Ratio | DateTime, Points, Distances | g/kg |
| 6 km Mixing Ratio | DateTime, Points, Distances | g/kg |
| 850 mb Mixing Ratio | DateTime, Points, Distances | g/kg |
| 700 mb Mixing Ratio | DateTime, Points, Distances | g/kg |
| 500 mb Mixing Ratio | DateTime, Points, Distances | g/kg |
| 20 m Theta | DateTime, Points, Distances | K |
| 500 m Theta | DateTime, Points, Distances | K |
| 1 km Theta | DateTime, Points, Distances | K |
| 1.5 km Theta | DateTime, Points, Distances | K |
| 3 km Theta | DateTime, Points, Distances | K |
| 5 km Theta | DateTime, Points, Distances | K |
| 6 km Theta | DateTime, Points, Distances | K |
| 850 mb Theta | DateTime, Points, Distances | K |
| 700 mb Theta | DateTime, Points, Distances | K |
| 500 mb Theta | DateTime, Points, Distances | K |
| 20 m Theta-e | DateTime, Points, Distances | K |
| 500 m Theta-e | DateTime, Points, Distances | K |
| 1 km Theta-e | DateTime, Points, Distances | K |
| 1.5 km Theta-e | DateTime, Points, Distances | K |
| 3 km Theta-e | DateTime, Points, Distances | K |
| 5 km Theta-e | DateTime, Points, Distances | K |
| 6 km Theta-e | DateTime, Points, Distances | K |
| 850 mb Theta-e | DateTime, Points, Distances | K |
| 700 mb Theta-e | DateTime, Points, Distances | K |
| 500 mb Theta-e | DateTime, Points, Distances | K |
| 20 m U | DateTime, Points, Distances | m/s |
| 500 m U | DateTime, Points, Distances | m/s |
| 1 km U | DateTime, Points, Distances | m/s |
| 1.5 km U | DateTime, Points, Distances | m/s |
| 3 km U | DateTime, Points, Distances | m/s |
| 5 km U | DateTime, Points, Distances | m/s |
| 6 km U | DateTime, Points, Distances | m/s |
| 850 mb U | DateTime, Points, Distances | m/s |
| 700 mb U | DateTime, Points, Distances | m/s |
| 500 mb U | DateTime, Points, Distances | m/s |
| 20 m V | DateTime, Points, Distances | m/s |
| 500 m V | DateTime, Points, Distances | m/s |
| 1 km V | DateTime, Points, Distances | m/s |
| 1.5 km V | DateTime, Points, Distances | m/s |
| 3 km V | DateTime, Points, Distances | m/s |
| 5 km V | DateTime, Points, Distances | m/s |
| 6 km V | DateTime, Points, Distances | m/s |
| 850 mb V | DateTime, Points, Distances | m/s |
| 700 mb V | DateTime, Points, Distances | m/s |
| 500 mb V | DateTime, Points, Distances | m/s |
| 20 m Line-Parallel Wind | DateTime, Points, Distances | m/s |
| 500 m Line-Parallel Wind | DateTime, Points, Distances | m/s |
| 1 km Line-Parallel Wind | DateTime, Points, Distances | m/s |
| 1.5 km Line-Parallel Wind | DateTime, Points, Distances | m/s |
| 3 km Line-Parallel Wind | DateTime, Points, Distances | m/s |
| 5 km Line-Parallel Wind | DateTime, Points, Distances | m/s |
| 6 km Line-Parallel Wind | DateTime, Points, Distances | m/s |
| 850 mb Line-Parallel Wind | DateTime, Points, Distances | m/s |
| 700 mb Line-Parallel Wind | DateTime, Points, Distances | m/s |
| 500 mb Line-Parallel Wind | DateTime, Points, Distances | m/s |
| 20 m Line-Perpendicular Wind | DateTime, Points, Distances | m/s |
| 500 m Line-Perpendicular Wind | DateTime, Points, Distances | m/s |
| 1 km Line-Perpendicular Wind | DateTime, Points, Distances | m/s |
| 1.5 km Line-Perpendicular Wind | DateTime, Points, Distances | m/s |
| 3 km Line-Perpendicular Wind | DateTime, Points, Distances | m/s |
| 5 km Line-Perpendicular Wind | DateTime, Points, Distances | m/s |
| 6 km Line-Perpendicular Wind | DateTime, Points, Distances | m/s |
| 850 mb Line-Perpendicular Wind | DateTime, Points, Distances | m/s |
| 700 mb Line-Perpendicular Wind | DateTime, Points, Distances | m/s |
| 500 mb Line-Perpendicular Wind | DateTime, Points, Distances | m/s |
| SBCAPE | DateTime, Points, Distances | J/kg |
| 0-3 km SBCAPE | DateTime, Points, Distances | J/kg |
| SBCIN | DateTime, Points, Distances | J/kg |
| SBLCL | DateTime, Points, Distances | m |
| SBLFC | DateTime, Points, Distances | m |
| SBEL | DateTime, Points, Distances | m |
| MLCAPE | DateTime, Points, Distances | J/kg |
| 0-3 km MLCAPE | DateTime, Points, Distances | J/kg |
| MLCIN | DateTime, Points, Distances | J/kg |
| MLLCL | DateTime, Points, Distances | m |
| MLLFC | DateTime, Points, Distances | m |
| MLEL | DateTime, Points, Distances | m |
| MUCAPE | DateTime, Points, Distances | J/kg |
| 0-3 km MUCAPE | DateTime, Points, Distances | J/kg |
| MUCIN | DateTime, Points, Distances | J/kg |
| MULCL | DateTime, Points, Distances | m |
| MULFC | DateTime, Points, Distances | m |
| MU Parcel Height | DateTime, Points, Distances | m |
| MUEL | DateTime, Points, Distances | m |
| 0-500 m Lapse Rate | DateTime, Points, Distances | K/km |
| 0-1 km Lapse Rate | DateTime, Points, Distances | K/km |
| 0-1.5 km Lapse Rate | DateTime, Points, Distances | K/km |
| 0-3 km Lapse Rate | DateTime, Points, Distances | K/km |
| 3-5 km Lapse Rate | DateTime, Points, Distances | K/km |
| 700-500 mb Lapse Rate | DateTime, Points, Distances | K/km |
| DCAPE | DateTime, Points, Distances | J/kg |
| 0-500 m Bulk Shear U | DateTime, Points, Distances | m/s |
| 0-1 km Bulk Shear U | DateTime, Points, Distances | m/s |
| 0-1.5 km Bulk Shear U | DateTime, Points, Distances | m/s |
| 0-3 km Bulk Shear U | DateTime, Points, Distances | m/s |
| 0-6 km Bulk Shear U | DateTime, Points, Distances | m/s |
| 0-500 m Bulk Shear V | DateTime, Points, Distances | m/s |
| 0-1 km Bulk Shear V | DateTime, Points, Distances | m/s |
| 0-1.5 km Bulk Shear V | DateTime, Points, Distances | m/s |
| 0-3 km Bulk Shear V | DateTime, Points, Distances | m/s |
| 0-6 km Bulk Shear V | DateTime, Points, Distances | m/s |
| 0-500 m Bulk Shear | DateTime, Points, Distances | m/s |
| 0-1 km Bulk Shear | DateTime, Points, Distances | m/s |
| 0-1.5 km Bulk Shear | DateTime, Points, Distances | m/s |
| 0-3 km Bulk Shear | DateTime, Points, Distances | m/s |
| 0-6 km Bulk Shear | DateTime, Points, Distances | m/s |
| 0-500 m Line-Parallel Shear | DateTime, Points, Distances | m/s |
| 0-1 km Bulk Shear Line-Parallel Shear | DateTime, Points, Distances | m/s |
| 0-1.5 km Bulk Shear Line-Parallel Shear | DateTime, Points, Distances | m/s |
| 0-3 km Bulk Shear Line-Parallel Shear | DateTime, Points, Distances | m/s |
| 0-6 km Bulk Shear Line-Parallel Shear | DateTime, Points, Distances | m/s |
| 0-500 m Bulk Shear Line-Perpendicular Shear | DateTime, Points, Distances | m/s |
| 0-1 km Bulk Shear Line-Perpendicular Shear | DateTime, Points, Distances | m/s |
| 0-1.5 km Bulk Shear Line-Perpendicular Shear | DateTime, Points, Distances | m/s |
| 0-3 km Bulk Shear Line-Perpendicular Shear | DateTime, Points, Distances | m/s |
| 0-6 km Bulk Shear Line-Perpendicular Shear | DateTime, Points, Distances | m/s |
| *Point Filter | DateTime, Points, Distances | unitless |
| Bottom Model Level Line-Parallel Wind | DateTime, Points, Distances | m/s |
| Bottom Model Level Line-Perpendicular Wind | DateTime, Points, Distances | m/s |
| Bottom Model Level Relative Humidity | DateTime, Points, Distances | % |
| 500 m Relative Humidity | DateTime, Points, Distances | % |
| 1 km Relative Humidity | DateTime, Points, Distances | % |
| 1.5 km Relative Humidity | DateTime, Points, Distances | % |
| 3 km Relative Humidity | DateTime, Points, Distances | % |
| 5 km Relative Humidity | DateTime, Points, Distances | % |
| 6 km Relative Humidity | DateTime, Points, Distances | % |
| 850 mb Relative Humidity | DateTime, Points, Distances | % |
| 700 mb Relative Humidity | DateTime, Points, Distances | % |
| 500 mb Relative Humidity | DateTime, Points, Distances | % |
| 900-700 mb PV | DateTime, Points, Distances | m2 s^-1^ K kg^-1^ |
| 900-800 mb PV | DateTime, Points, Distances | m2 s^-1^ K kg^-1^ |
Asterisk (*) Notes:
- W and Vertical Velocity: The omega and vertical velocity values (stored as variables "W" and "Vertical Velocity") appeared to be unphysically small and thus likely unreliable. This may be due to the data coming from the HRRR analysis hour (FH00) rather than a forecast hour (FH01 or greater). These values were not used for final analysis but have been included within this dataset. Please exercise caution when using these values.
- Point Filter: This field contains values of "0" or "1" and is used to identify points that were filtered out of final analysis (see linked publication for additional information regarding point filtering). A value of "1" represents points that were filtered from (i.e., not included) in the final analysis.
File: Scripts.zip
Description: Contains a sample of plotting and calculation scripts, including:
Convective Line Drawing Tool (Python Script): This is the drawing tool GUI that was used to manually plot a series of points that would later be linearly connected to create a representation of the convective line for every hour of all QLCSs. Before using, the GUI must be edited to manually specify the start date (year/month/day) of the desired case. An array of hours is then specified by the user (starting at the first desired hour). The case number is also manually specified, and the plot bounds can be adjusted (if needed). Once this info is entered, the script can be run. Upon running, the script will download HRRR data files for the first hour and open a GUI that contains a plot of simulated reflectivity from the HRRR analysis hour where user-plotted points can be added by clicking on the GUI. Once all desired points are drawn for an hour, clicking save will store the points in an array and advance the plot to the next hour. This is repeated until the script reaches the end of the hours array that was specified by the user. The points for all hours are then stored within one CSV file per case.
Composite Sounding Generator (Jupyter Notebook): Copy of the script that was used to generate the composite sounding NetCDF files. This copy specifically shows an example of the creation of the composite soundings for tornadic hours.
Composite Sounding Plotter (Jupyter Notebook): Copy of the script used to plot the composite soundings.
Main_Plotting_Script (Jupyter Notebook): Commented script that was used to create a majority of plots. Instructions can be found within the Notebook. Must also download the All Cases folder and the two QLCS CSVs (hourly and case data) to use with this script.
Native_Levels_Data_Collector (Jupyter Notebook): Copy of the script that was used to identify, select, and save the original HRRR data for each identified grid point for every QLCS case hour.
Variable_Calculations (Jupyter Notebook): Example script demonstrating how some variables/parameters were calculated and stored.
Code/software
Python 3.9.13
Individual packages used are listed at the top of each script (provided mainly via Jupyter Notebook files).
Access information
Data was derived from the following sources:
- The NOAA High-Resolution Rapid Refresh (HRRR) model was accessed on 1 June 2023 from https://registry.opendata.aws/noaa-hrrr-pds.