The local expansion field is not isotropic: directional variation of H0 explains ~50% of the Hubble tension

The Hubble tension -- a 5-sigma discrepancy between local (H₀ = 73. 04 +/- 1. 04 km/s/Mpc) and CMB-inferred (H₀ = 67. 36 +/- 0. 54 km/s/Mpc) values -- remains one of the most pressing problems in cosmology. Using 2, 098 Type Ia supernovae from the Zwicky Transient Facility Data Release 2 and 38, 053 peculiar velocities from Cosmicflows-4, we decompose the local H₀ field into real spherical harmonics up to lₘax = 5 and detect directional variation at p = 1. 7 x 10^-19 via a line-of-sight transfer function model. The shell model beats a simple dipole void by Delta chi² = 55 (p = 10^-13) and the isotropic null by Delta chi² = 94 (p = 10^-19), with a characteristic scale of ~222 Mpc consistent with the Keenan-Barger-Comerford (KBC) void. The quadrupole amplitude exceeds the dipole (A₂/A₁ = 1. 02), confirming the kinematic backreaction prediction of Heinesen 95% CI: 37%, 63%), reducing the discrepancy from 5. 0 sigma to approximately 2. 2-2. 8 sigma. No new physics is required for this reduction.