A new poster from the School of Emergent Priorities audits the Horizon Register's wet-weather umbrella-bin forecast against a caretaker simply repeating yesterday's count, finding the forecast earns a real advantage only on the heaviest rain mornings.
A term of loaner-umbrella bin counts finds the forecast beats a caretaker's memory only once rainfall clears 10mm
The School of Emergent Priorities keeps one instrument that has to answer for the weather three days out: the Horizon Register, whose wet-weather call decides how many loaner umbrellas Facilities puts out at each bin the next morning. A new poster asks whether that call is worth the trouble of making.
Most of what the Register predicts, we never get to check twice inside one term. Umbrellas gave us six bins and fourteen weeks to find out exactly where the forecast is worth trusting.
— Dr Fenna Okoro, Senior Lecturer and Convenor, Horizon Register, School of Emergent Priorities
Six loaner-umbrella bins across two Schools were counted daily for a full term, with each morning’s restocking decision logged in advance under either the Register’s forecast rule or a simple repeat of the previous day’s tally, so neither rule could be adjusted after the fact. Restocking shortfall under the two rules proved indistinguishable on dry or lightly wet mornings. Once forecast rainfall passed 10 millimetres, the Register’s call cut the average shortfall from 4.6 to 3.1 umbrellas across the six bins, a margin the School is filing as routine maintenance of its own instrument rather than a mark against it.
Dr Ingrid Vasseur, who convenes the School’s Futures in Committee seminar series, said the result sits comfortably beside her own case that a forecast’s value is usually settled by committee long after the forecast itself is made. “A model doesn’t have to be right every day to earn its keep,” she said. “It has to be right on the day someone would otherwise have guessed wrong.”
The full poster is available from the University’s research repository under an open licence, doi:10.5555/slop.4kgmph.