🌀 Hodograph Options

SounderPy’s standalone hodograph can be displayed in ground-relative or storm-relative coordinates and can use an automatically calculated or user-defined storm motion.

This tutorial covers:

• ground-relative hodographs;

• storm-relative hodographs;

• right-moving, left-moving, and mean-wind storm motions;

• user-defined storm motion;

• hodograph boundary overlays;

• dark mode and saved figures.

---

Retrieve the Example Profile

import sounderpy as spy

data = spy.get_obs_data(
    "OAX",
    "2014", "06", "16", "18",
    hush=True,
)

---

Ground-Relative Hodograph

The default hodograph is ground relative:

spy.build_hodograph(
    data,
    sr_hodo=False,
    radar=None,
    map_zoom=0,
)

---

Storm-Relative Hodograph

Set sr_hodo=True to subtract the selected storm-motion vector from the winds:

spy.build_hodograph(
    data,
    sr_hodo=True,
    radar=None,
    map_zoom=0,
)

Storm-relative plotting requires a valid storm-motion vector. If SounderPy cannot determine one from the profile, the plot falls back to a ground-relative hodograph.

---

Selecting Storm Motion

The default storm motion is:

storm_motion="right_moving"

Common supported string forms include:

storm_motion="right_moving"
storm_motion="left_moving"
storm_motion="mean_wind"

These select the right-moving Bunkers motion, left-moving Bunkers motion, or mean-wind motion used by SounderPy calculations.

---

User-Defined Storm Motion

A custom storm motion can be supplied as:

[direction_degrees, speed_knots]

For example:

spy.build_hodograph(
    data,
    storm_motion=[250.0, 45.0],
    radar=None,
    map_zoom=0,
)

The same custom motion can be used for a storm-relative hodograph:

spy.build_hodograph(
    data,
    storm_motion=[250.0, 45.0],
    sr_hodo=True,
    radar=None,
    map_zoom=0,
)

---

Hodograph Boundaries

A straight boundary axis can be added using hodo_boundary.

The argument is a dictionary containing matching lists of angles and colors:

boundary = {
    "angle": [45],
    "color": ["tab:purple"],
}

spy.build_hodograph(
    data,
    hodo_boundary=boundary,
    radar=None,
    map_zoom=0,
)

Multiple boundaries can be supplied:

boundary = {
    "angle": [45, 120],
    "color": ["tab:purple", "tab:blue"],
}

---

Theme and Output Options

Dark mode:

spy.build_hodograph(
    data,
    dark_mode=True,
    radar=None,
    map_zoom=0,
)

Save at higher resolution:

spy.build_hodograph(
    data,
    radar=None,
    map_zoom=0,
    dpi=200,
    save=True,
    filename="oax_hodograph.png",
)

---

CLI Examples

Save a ground-relative hodograph:

sounderpy obs OAX 2014-06-16 18 \
    --plot hodograph \
    --map-zoom 0 \
    --plot-file oax_hodograph.png

Save a storm-relative hodograph:

sounderpy obs OAX 2014-06-16 18 \
    --plot hodograph \
    --storm-relative \
    --map-zoom 0 \
    --plot-file oax_sr_hodograph.png

Save a dark storm-relative hodograph:

sounderpy obs OAX 2014-06-16 18 \
    --plot hodograph \
    --storm-relative \
    --dark-mode \
    --map-zoom 0 \
    --plot-file oax_sr_dark.png

Next Steps

Continue to Working with Data Sources to see how different profile sources feed the same SounderPy plotting workflow.

See also:

• Plotting Data