Yama-arashi (山嵐), the mountain storm.

Nage-waza (throwing techniques), Te-waza (hand techniques).
Required for: 4th Dan (black belt, British Judo Association); 5th Dan (black belt, British Judo Association).

About
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The mountain storm, made famous by Saigo Shiro: from a same-side grip on lapel and sleeve, tori sweeps like harai-goshi while the hands wrench like a hand throw. The Kodokan classifies it among the hand techniques; its exact classical form is much debated, so treat any single description as one reading.

Step by step (standard right-handed form)
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1. Take the characteristic same-side grip: your right hand high on their RIGHT lapel, palm out at the collar, your left hand on their right sleeve, so both of your hands control one side of their body.
2. Draw them strongly forward and up onto their toes with both grips, their weight loading over their right foot.
3. Pivot in on your left foot and sweep your right leg along the outside of their right leg, as in the sweeping hip throw.
4. As the leg sweeps, wrench both hands over to your left like turning a great wheel: the hand action, not the hip, is the heart of this throw.
5. They are carried over the sweeping leg and the turning hands and land on their back in front of you. Keep the sleeve; the same-side grip means their fall arrives across your body.

Key points
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1. Same-side grips: right hand high on their right lapel, left on their right sleeve
2. The hands wrench over like a wheel while the leg sweeps
3. Balance entirely on the supporting leg through the sweep

Receiving it
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Both grips land on your right side and everything happens on that one line: drawn up over your right foot, the sweep and the wrench arrive together and you are turned in the air. Tuck your chin, go with the big rotation, and slap with your free left arm. The one-sided grip makes this feel less predictable than harai-goshi, so take it from experienced partners while learning.

Reference pages elsewhere
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Yama-arashi on the IJF technique reference (International Judo Federation): https://judo.ijf.org/techniques/Yama-arashi

From Waza Book: https://wazabook.com/techniques/yama-arashi/