Chris Parmer — home

A Field Guide to Quiver

Ocean surface currents along the US West Coast measured by HF radar, arrows colored by speed Surface wind arrows at 1,586 airports across North America from one METAR snapshot Hurricane Ian's cyclonic wind field over Florida at landfall, from ASOS stations Jensen-model wake field over the 80-turbine Horns Rev 1 layout: pale ambient wind arrows slowing to violet and pink streaks behind each turbine column GPS-measured crustal motion in the western US, with coastal California sliding northwest Electric dipole field drawn as a direction field between a positive and negative charge Potential flow over a Joukowski airfoil with arrows accelerating over the upper surface Lid-driven cavity flow at Reynolds number 1000: unit arrows circling a central primary vortex inside a square box, fading to grey in the corner eddies, with faint streamline contours Principal stress directions around a circular hole in a plate under horizontal tension, arrows flowing around the hole and turning violet where stress concentrates at the flanks Negative gradient field on Himmelblau's function with two optimizer trajectories Phase portrait of a damped pendulum: direction field with trajectories spiraling into wells Direction field of effective gravity in the rotating Earth-Moon frame with the five Lagrange points marked as diamonds, arrows fading where the pull vanishes Every Lionel Messi pass in the 2022 World Cup final drawn as arrows on a pitch County-level arrows leaning red-right or blue-left showing how each county's presidential vote shifted between 2020 and 2024, most of the map leaning right Worldwide compass-needle arrows from IGRF-14 colored by magnetic declination

Ocean Surface Currents (Oceanography)

NOAA HFRNet coastal HF radar · 6 km mosaic · 2026-08-13 21:00Z · Code

Ocean surface currents along the US West Coast from HF radar: thousands of small arrows colored by speed, showing the California Current flowing south and a mesoscale eddy off Cape Mendocino

Surface Winds, One Moment (Meteorology)

NOAA METAR cache · 1,586 stations · snapshot 2026-08-14 ~20:55Z · Code

Wind arrows at 1,586 airports across North America from a single METAR cache snapshot, colored by wind speed in knots, over muted state outlines

Hurricane Ian at Landfall (Tropical Meteorology)

Iowa Mesonet ASOS · Florida network · 2022-09-28 18:40–19:10Z · Code

Hurricane Ian's wind field over Florida at landfall: arrows from 62 ASOS stations curling counterclockwise around an eye marker at Cayo Costa, the strongest stations colored violet and pink

Wind Farm Wakes (Wind Energy)

Horns Rev 1 layout via PyWake · Jensen wake model, 8 m/s · Code

Jensen-model wake field over the 80-turbine Horns Rev 1 layout: pale ambient wind arrows slowing to violet and pink streaks behind each turbine column

The San Andreas, in Millimeters (Geodesy)

UNR Nevada Geodetic Laboratory · MIDAS velocities · North-America-fixed frame · 1,015 stations · Code

GPS station velocities in the western US relative to stable North America: pink and violet arrows along coastal California pointing northwest at tens of millimeters per year, fading to nearly motionless teal dots inland

The Electric Dipole (Electromagnetism)

Computed — Coulomb's law, two point charges · Code

Electric dipole direction field: equal-length arrows flowing out of a pink positive charge and into a teal negative charge, colored by the log of field strength

Lift, Visualized (Aerodynamics)

Computed — Joukowski conformal map, Kutta condition, 8° angle of attack · Code

Flow field around a dark Joukowski airfoil at 8 degrees angle of attack: arrows accelerate and turn pink over the upper surface, slow and pale below, converging smoothly at the trailing edge

The Lid-Driven Cavity (Computational Fluid Dynamics)

Computed — vorticity–streamfunction solve, Re = 1000 · Code

Lid-driven cavity flow at Reynolds number 1000: unit arrows circling a central primary vortex inside a square box, fading to grey in the corner eddies, with faint streamline contours

Stress Around a Hole (Structural Engineering)

Computed — Kirsch solution, uniaxial tension · Code

Principal stress directions around a circular hole in a plate under horizontal tension, arrows flowing around the hole and turning violet where stress concentrates at the flanks

Why Momentum Overshoots (Machine Learning)

Computed — Himmelblau's function, 220 steps per optimizer · Code

Negative-gradient direction field over grey contours of Himmelblau's function, with a violet gradient-descent path settling in the nearest minimum and an orange momentum path overshooting into a different one

The Pendulum's Phase Portrait (Dynamical Systems)

Computed — damped pendulum, RK4 trajectories · Code

Phase portrait of a damped pendulum: grey direction-field arrows swirling around stable wells at 0 and ±2π, with violet, teal, and pink trajectories spiraling in, and open dots marking the unstable balance points at ±π

The Lagrange Points (Astrodynamics)

Computed — Earth–Moon rotating frame, μ = 0.01215 · Code

Direction field of effective gravity in the rotating Earth-Moon frame with the five Lagrange points marked as diamonds, arrows fading where the pull vanishes

Sixty Passes by Messi (Sports Analytics)

StatsBomb Open Data · Argentina–France, 2022 World Cup final · Code

Messi's sixty passes in the 2022 World Cup final drawn on a football pitch: solid violet arrows for completed passes concentrated on the right half-space, dotted pink arrows for the eleven incomplete ones

County Swing Arrows (Election Cartography)

County presidential returns · 2020 → 2024 · after the classic New York Times county swing map · Code

County-level arrows leaning red-right or blue-left showing how each county's presidential vote shifted between 2020 and 2024, most of the map leaning right

Where Compasses Point (Geomagnetism)

IGRF-14 · epoch 2026.0 · computed on a 6° grid · Code

World map of unit-length compass-needle arrows from IGRF-14, colored pink where declination is east and teal where west, with pale agonic lines between and strong shearing near the south magnetic pole