Hawaii Moved A Hurricane 22 Miles. It Pays By The Mile.
A storm due to cross the Big Island will pass south of it. Four aircraft flew 31 hours into its outer bands, on a state order that pays $184,000 a nautical mile.
The Sky Desk
Weather, aviation, and atmospheric dispersal. Forecasts twice daily; error rate published weekly.
The dispersal index
The dispersal index is a nine-point scale devised by this newspaper in 2011 and maintained by Ray Pell. It combines four observations, all made from the roof of this building at 06:00 and 12:00 local:
- Persistence. How long a contrail remains visible, in minutes, averaged over the first ten aircraft observed.
- Spread. The ratio of a trail's width at ten minutes to its width at one minute.
- Grid density. Crossings per square degree of visible sky.
- Overflight count. Aircraft observed above 25,000 feet in the six-hour window.
An index of 0 means no persistence. An index of 9 means the observer could not distinguish trail from cloud at any point in the window.
The error record
Ray Pell has issued 5,214 forecasts and been wrong 3,388 times. That figure is updated every Friday and is published whether or not it is embarrassing. The desk's view is that a forecaster who does not publish their error rate is not forecasting, but guessing in public.
From the desk
A Village Lost 300 Homes. Forty-One Generators Were Burning Silver Iodide Upwind.
Southern France runs a hail-suppression network in public. This newspaper obtained the private contract behind it: Clause 9 pays a bonus for convective redirection. Eleven of the forty-one burns that night are missing from the published log.
Solveig Marchetti-Rand Randomised Her Own Rain Programme. The Result Closed It.
She insisted on sealed envelopes and a table of random numbers against her board's advice. Six seasons returned four per cent, with an interval from minus five to plus thirteen. She published all of it. Thirty-one people lost their jobs.
8,600 Tonnes Of Sulphur Reach The Stratosphere Each Year. Nobody Aimed Any.
A mass balance, not an argument. The covert fleet would need 8,000 sorties a year and shows up in no excise return. The accidental version needs no fleet, and the one deliberate intervention on the books was aimed at lungs.
The Null ResultThe Sky Desk
We Tested The Heater Against Forty Years Of Storms. It Was Switched Off.
Three hypotheses, pre-registered in March before we asked for anything: severe weather, earthquakes within 900 kilometres, reader sky-sound reports. The facility's transmission log for 1981 to 2025 arrived in June. All three tests return nothing, and the log says why.
Nine Per Cent, Plus Or Minus Eleven. The Insurers Renewed Anyway.
Two statisticians who have never met were paid to test thirty-nine seasons of hail suppression over the same prairie. They agree on the number. The consortium's own actuaries reached it in 2011 and filed it under vehicle routing.
The Contrail Fix Works. It Travels In Item 18, As Free Text.
Fourteen months, 3,114 requests to climb or descend around ice-supersaturated air. The diverted flights formed fewer lasting trails for 0.11 per cent more fuel. There is no box on the flight plan for asking.
‘They Bought Our Rain.’ The Gauges Upwind Fell Just As Far.
The tribunal never reached the physics. It dismissed on standing: the growers pay a levy that part-funds the seeding contract they were suing. What actually changed in 2017 was the lead claimant's water allocation.
The County Insured Itself Against Rainmaking. Clause 7 Excludes Rainmaking.
Haverly County has paid $125,400 over eleven years for cover against weather-modification claims. The policy's pollution exclusion names silver iodide, the substance its own generators burn. No claim was ever made, so nobody found out.
InvestigationThe Sky Desk
The Spiral Was Explained In Twenty-Six Hours. It Is Still Cited.
On 9 December 2009 a blue beam and an enormous grey spiral stood over northern Norway. A submarine had fired a missile whose third stage failed. The spiral was sunlight on leaking fuel, spinning.
InvestigationThe Sky Desk
The Black Helicopters Are On A Chart You Can Buy For £14
Military low-level training routes are published, numbered and mapped. We plotted eleven months of reader sighting reports against them. Eighty-one per cent fell within two kilometres of a published route, and the rest are the interesting part.
ExplainerThe Sky Desk
For Two Centuries It Was Folklore. It Turned Out To Be Dirt.
Sailors and farmers reported it for two hundred years and were told they had imagined it. In July 2012 a spectrograph on a plateau was pointed at ordinary lightning when a ball appeared 900 metres away.
They Do Modify The Weather. Nobody Can Prove By How Much.
Fifty-odd countries seed clouds and the physics is not in dispute. The arithmetic is: you cannot measure the rain that would have fallen anyway. Seventy-five years on, nobody has solved that, and the honest operators say so.
ExplainerThe Sky Desk
The Week Ahead, And Why I Am Probably Wrong About Thursday
Seven days from the Sky Desk, with the confidence I actually have rather than the confidence a forecast box implies.
ExplainerThe Sky Desk
I Have Been Wrong 3,388 Times. Here Is The Breakdown.
The Sky Desk publishes its error rate every Friday. This is the annual version: the months I am worst at, the spring I was wrong nine times in ten, and the one change a reader in Binghamton made me make.
Eleven Years Of Watching The Sky. It Was The Humidity.
The Sky Desk has logged every trail here twice a day since 2015: 44,102 observations. We paid a physicist who had never heard of us to find what predicts persistence. Humidity explains 71 per cent. Day of the week, 0.2.
