HI
I’ve been scouring articles on Hurricane Harvey but I have’t been able to find which scale is being used to measure the record rainfall produced it. I look forward to your feedback.
It’s not the Saffir–Simpson hurricane wind scale (SSHW) which excludes flood ranges, storm surge estimations, rainfall.
How many different rainfall scales are there? I thought you measured rainfall by saying how much rainfall there was.
I guess you can measure it either by depth or by total volume, but the units given in any given article should make it clear which one they’re using.
Rain gaugesare rain gauges. All the reports I’ve seen have used inches, which is - well, not the worldwide standard, but at least it’s depth, rather than hogsheads per square ell, so on the right track.
The rest of us use millimeters, which is exactly the same as l/m[sup]2[/sup]
Sorry, Chronos I was referring to ranking scales. I haven’t been able to find any scales that ranks rain intensity and level of danger. I have found things like synoptic scale and Scale Dependence of Radar-Rainfall Rates, point-scale rainfall rate R(x, t) etc. but no scales that rank torrential rainfall intensity and danger. Perhaps there isn’t one.
I don’t think there is one for rainfall … rather we use river level gauges … one location can take 10 inches of rain with no negative effects whereas another location will be destroyed with the same amount of rain …
The Advanced Hydrological Prediction Service has a nice interactive mapping program … click on Houston to see all the gory details …
Thanks watchwolf49. When the National Weather Service uses words like ‘catastrophic’, it that an actual level above ’ Major Flooding’ according to the “River Level Gauges” format? I have not seen any format for rain measurement using the term ‘catastrophic’.
“Catastrophic flooding in the Houston metropolitan area is expected to worsen,” the National Weather Service said Sunday. It added: “This event is unprecedented and all impacts are unknown and beyond anything experienced.”
Exactly as ww49 says.
The NHC is belatedly coming to the realization that what attracts headlines is hurricane wind speed and the Saffir-Simpson scale.
But what costs the big money is torrential rains.
And what kills people is storm surge.
So the severity scale that everybody in the public and media knows about is not talking about the important parts of the threat we actually face with hurricanes.
They have made great progress just in the last year upgrading their written messaging and graphics to address expected total rainfall and possible storm surge levels as two of the three relevant hazard factors (along with wind).
What they don’t have, and don’t expect to have any time soon, is some kind of overall weighted severity-o-meter for the total blended hazard. For reasons of both scientific validity and PR practicality.
Thanks LSL Guy for that clarification. Thank you all.
AFAIK, they’re using it in the rhetoric sense. The actual category above “Major Flooding” is “Record Flooding” according to NOAA.
The only (somewhat) scientific way of rating floods I know is the recurrence interval method (the “1-in-X years” rating), which is *kind of *linked to actual human-effect severity, but only if you squint.
The important detail is the NWS says “Catastrophic flooding in the Houston metropolitan area is expected to worsen” (emphasis mine) … and indeed all the river gauges are above record levels and spilling over the banks …
The Saffir-Simpson scale has well known shortcomings … as is true with any simple measure of complex things, much information has to be removed … just remember that even Tropical Depressions can cause major and destructive flood events … I’m guessing in the weeks and months to come, we find that Harvey-as-Hurricane did some damage right on the coast, but it will be Harvey-as-Tropical Storm that laid waste to Houston …
Great points Mr Dibble … thanks for including that here …
Thanks MrDibble.
I wouldn’t say that it’s related at all. A hundred-year storm in the Atacama Desert might mean less than an inch of rainfall, for instance. A five-year storm in Florida is going to be much worse than that. And the impact on humans will also of course depend on how many humans are present.
And here I thought I loaded my statement with enough qualifiers 
I wouldn’t say “not related at all” - obviously it’s tied to place, but that doesn’t mean we can’t say a 1-in-1000 isn’t worse than 1-in-10.
From National Geographic “The Driest Place on Earth”:
Well, some parts are dry. others: