Why the current hurricane rating system needs to be scrapped

Posted: October 11, 2018 by oldbrew in Critique, predictions, research

Image credit: sanibelrealestateguide.com

A rating system that may lead people to misunderstand the likely impact of an approaching storm is obviously not satisfactory. So is there a better approach?

For decades, hurricanes have been rated on a scale of 1 to 5 based solely on a storm’s wind speeds.

But as recent hurricanes show, a tropical cyclone’s winds often tell us little about its real threats — coastal storm surge and precipitation-driven flooding, say Yale researchers.

Modern meteorological data collection gives us an unprecedented view into the real-time growth, track, and death of tropical cyclones.

Recently, we watched as Hurricane Florence started as a tropical wave off the west coast of Africa, grew into a storm with Category 4 winds, and then made landfall on September 14 near Wrightsville Beach, North Carolina. At that point, with sustained winds down to 90 miles-per-hour, Florence was classified as merely a Category 1 storm. But after moving rapidly across the Atlantic, Hurricane Florence had slowed to a crawl before hitting the Carolina coast, turning the storm into a rain bomb that dropped more precipitation — 36 inches in one town — than all previous U.S. tropical cyclones save one, last year’s Hurricane Harvey. Fears of coastal flooding were rapidly replaced by the reality of prolonged, inland flooding.

Hurricane Harvey, which devastated the Houston, Texas area in August 2017, came ashore as a Category 4 storm under the classic hurricane threat scale, which is based solely on wind speeds. But it was not wind damage or storm surge that made Harvey the second-most damaging hurricane in U.S. history (behind 2005’s Katrina) — it was the 60 inches of rain that fell for days in and around Houston, causing catastrophic flooding. As with Florence, Hurricane Harvey caused far more death and destruction from inland precipitation than from coastal storm surge and erosion.

And then there’s Hurricane Sandy, whose winds weren’t even strong enough to warrant classifying the storm as a hurricane when it made landfall in the U.S. mid-Atlantic states in 2012. Still, this massive storm generated significant storm surge — around 14 feet — that had dramatic coastal impacts, ripping barrier islands in half, causing significant oceanfront property damage, and bringing severe flooding to New York City.

All of these storms have one thing in common: The hazards they unleashed were not adequately described by the traditional hurricane classification system — the Saffir-Simpson Scale.

Continued here.

  1. A C Osborn says:

    Yes let’s change the system, so that we can’t compare it to historical Hurricanes.
    The statement that ” But it was not wind damage or storm surge that made Harvey the second-most damaging hurricane in U.S. history (behind 2005’s Katrina)” is also total bullshit as they left off the word Modern.
    Previous Hurricanes were far more devestating.

  2. oldbrew says:

    One of several ways of measuring hurricane strength is by the lowest barometric pressure.


    Wind speeds for older hurricanes have the limitation that measuring gauges probably couldn’t withstand really high winds e.g. Wikipedia says:
    The original measurements of Camille [1969] are suspect since wind speed instrumentation used at the time would likely be damaged by winds of such intensity.
    – – –
    Dodgy stats for Hurricane Michael?

    The NOAA wind gauge at Panama City didn’t back up any of the claims. It showed a peak sustained wind speed of 62 knots before the eyewall arrived, and minimum pressure of 937.5 mb. Neither remotely close to the hype.


  3. Hifast says:

    Reblogged this on Climate Collections and commented:
    Meteorologically, Saffir-Simpson is fine. The Yale researchers are focused on damage brought not only by wind but by storm surge and heavy rainfall.

    They cite storm track angle of attack with the coastline and topography as key factors.

    Looks like they want to bring the economic impact into play to demonstrate tropical cyclones are getting worse over time.

    If they want to make that play, perhaps they should include the density and value of infrastructure present in each storm’s path. Using infrastructure as a denominator in their proposed new system would certainly be meaningful.

  4. Ron Clutz says:

    Storm expert David Nolan gave his views on this issue.
    Q: The National Hurricane Center today upgraded Florence to a Category 4 storm. What exactly does that mean?
    A: It means that, by their best estimate, there are wind speeds somewhere at the surface of 130 miles per hour or greater. This estimate comes from a combination of satellite images, and, in this case, from NOAA [National Oceanic and Atmospheric Administration] aircraft that have been flying in Florence this morning.

    Q: How many categories are there?
    A: The categories go from 1 to 5.

    Q: Could there ever be a Category 6?

    A: No. Fives themselves are very rare. And reaching higher speeds — like 170 or 180 mph — is extremely rare. So it doesn’t make sense to make a category for something that will still be extremely rare, even if it happens a little more, like once every five years instead of once every 10 years.


  5. oldbrew says:

    Not a peep on BBC TV news tonight about the supposed monster storm Michael.
    Strange that 😐

    Wasn’t it supposed to be ‘record-breaking’? Not quite in the Galveston 1900 league, fortunately.

    6000 dead…approximately 30,000 people in the city were left homeless, out of a total population of nearly 38,000.

  6. oldbrew says:

    Storm Surge
    Posted on October 11, 2018 by tonyheller

    Arial photography shows that most of the damage was done by the storm surge, rather than by wind. Roof damage is caused by wind, but houses getting washed away is caused by water. Category four winds would have removed just about all the roofs, and knocked down most of the trees.


    Commenter NavarreAggie says:
    I think the fallacy (and this is mostly NOAA’s fault) is equating maximum wind speed with storm damage potential.
    – – –
    Wind speeds 18 h before landfall correlated best with surge heights.

  7. Gamecock says:

    I’m on board. After they abandoned Saffir-Simpson with Superstorm (sic) Sandy, I too thought 1 to 5 was too simplistic.

    Above Superstorm, we have Boaty McBadass.

    “Seriously Badass” next. Then:

    “Place your head between your knees and kiss your sweet ass goodbye.”

    Other ratings are still available, and will go to the highest bidder. The Weather Channel will be talking about Kellogg’s Storm Baker for decades.

    Saffir-Simpson was invented to STOP all the BS. The BSers want back in.