Here we go again. This devastating storm, which rapidly intensified yesterday before striking Port Hedland in northwestern Australia, was estimated to have 110 knot sustained winds by the Joint Typhoon Warning Center. 115 knot winds are the cutoff for a Category 4 storm on the Saffir-Simpson Scale. By these lights, George was a strong Category 3 storm.
But at least according to the advisory preserved here, the Australian Bureau of Meteorology’s tropical cyclone warning center in Perth was saying at one point that the storm had a minimum central pressure of 910 hectopascals (or millibars). For comparison, that’s also the minimum central pressure given for Category 5 Hurricane Ivan in the Atlantic in 2004, when the storm had 145 knot winds. And at least according to Wikipedia, it would be the lowest pressure in any storm so far this year. Does something sound amiss here?
It certainly does to me. Using the so-called Atkinson/Holiday wind pressure relationship employed by the Joint Typhoon Warning Center–see e.g., here–a storm with 110 knot winds should have an estimated minimum pressure of 933 millibars/hectopascals. Every storm is different and the Atkinson/Holiday formula is just a rough guide. Nevertheless, if that 910 mb/hPa measurement reported by Perth is right, this storm might have been much stronger than a Category 3.
My guess is that with this hurricane, as with so many others, we’re going to wind up with a lot of uncertainty about how strong it actually was.
P.S.: I’m not sure what the basis for the 910 mb/hPa measurement was….