NASA's Weather Confidence Level

Atlantis no longer seeks shelter and returning to pad, SpaceflightNow

“Atlantis’ rollback began at 10:04 a.m. after a long debate about the forecast and whether to ride out the storm at the pad. In the end, Leinbach decided predictions of 65-knot gusts were too much and the slow move began.”

Editor’s note: The Tuesday 29 Aug weather weekly outlook from the 45th Weather Squadron at Patrick AFB calls for sustained winds at 50 knots with gusts up to 60 knots on Wednesday evening. That forecast has a differential of 5 knots from the number Leinbach determined was unacceptable – and warranted a rollback to the VAB. Comparing 60 with 65 knots, a 5 knot differential is around 7%. Is NASA that confident that their forecast is that accurate – in terms of storm track and expected conditions on the pad? It would seem so. It will be interesting to see how they assure that nothing hit the ET so as to cause underlying foam damage – especially given the ease with which ET workers – and woodpeckers – have been shown to damage it.

Reader note: “The forecast you referred to was posted at 8am using the 5am NHC bulletin… As I think you are aware, NHC downgraded the threat at 11am and even further at 2pm, which was one of the last tidbits they used to stop the rollback and return to pad. The number Mike gave was 70kts as the cutoff for being on the pad, not 65kts.”

Editor’s note: I stand corrected – alas, portions of the audio we had on the phone bridge – especially the beginning – were unintelligible due to overlapping echoes. None the less, my point remains: is the difference between the wind speeds comensurate with the accuracy with which NASA has been assured that the weather predictions are correct?