New Hurricane Rating Scale?

[Ara Pacis]

It seemed to some that Katrina was merely a Catagory 4 hurricane on the Saffir-Simpson scale and many compared that to Camile that was a Cat-5 storm. However, Katrina was a very powerful Cat-5 (but Cat-4 at eye-landfall) and was very wide as well. So I ask: Should we construct a new hurricane rating scale that reveals more information?

The current Saffir-Simpson Hurricane Scale rates the storms 1 through 5 by wind:
Tropical Depression up to 38 mph
Tropical Storm 39-73 mph
Cat 1 = 74- 95 mph (21 mph range)
Cat 2 = 96-110 mph (14 mph range)
Cat 3 = 111-130 mph (19 mph range)
Cat 4 = 131-155 mph (24 mph range)
Cat 5 = 155+ mph (undefined range)

The NOAA site does list some other technical information related to the rating, such as the Storm Surge, yet it is not made clear if this is simply a result of the primary measurment (wind) or if it is actually included in the calculus. However, this Wikipedia article does claim that the NHC added Storm Surge effects.

It is my suggestion that perhaps we should include an extra dimension of measurement such as the size of the storm, the millibar measurment, or perhaps use a arithmetic or logarithmic metric, similar to the Richter Earthquake Scale.

I was thinking that perhaps a point metric based on the radius of either maximum sustained winds or just cat-1 sustained winds might be added. It might use a 1-5 (or 0-4, 0-9?) range that the meteorlogists could later define with 1 being a narrow storm and 5 being a wide storm. So a small weak storm might be a 1.1 while a storm that is both moderately strong and wide would be 3.3 and an extremely strong storm that is really wide would be 5.5. Katrina (2005) might be a 4.5 or a 5.5 and Charley (2004) would be a 4.1 or 4.2. Or would a Alphabetic appendage (4A for Katrina, 4E for Charley) be preferable?

[piersdad]

definately need a rating larger than 155mph as theses will become common soon

[crosscountry]

definately need a rating larger than 155mph as theses will become common soon

Is that a prediction?


Where do you get your information? I'd like to read that article.

[CalabashCorolla]

Recently a new scale to rate snowstorms in the Northeast US was developed by meteorologists Paul Kocin and Louis Uccellini. In addition to total snowfall and wind speed, the area of coverage of a snowstorm and the total population affected are taken into account when a storm is rated. This means that a storm that hits a place like Northern Maine would be ranked lower than a storm of the same size and strength that hits the Megalopolis.

However, the Kocin-Uccellini scale, like the Fujita scale of tornado intensity, are used to posthumously rank storms, while the Saffir-Simpson scale is a damage-potential scale that is used to give people the idea of what kind of damage a storm of a certain intensity would produce if it were to make landfall. And probably any scale that invites post-storm revision of ratings would cause some trouble. The upper end of the Saffir-Simpson scale is probably appropriate, however, since so very few storms ever exceed 155 mph for winds or undercut 920 mb for pressure (the lowest pressure for the Atlantic basin is 888 mb in Hurricane Gilbert in 1988).

[George]

You could be right in thinking we should adopt a more appliable scale. Wind speed energy increases as the cube, IIRC, so there is a much bigger difference in energy within the higher ranges.

Couldn't the total kinetic energy of the system be the main element along with surge and eye speed?

[Ara Pacis]

I found the Inland Wind Model at the National Hurrican Center and wondered if it would be useful to my idea. My scale adaptation is not meant to be a post impact evaluation but a real-time measurement that can be applied for use by governments for evacuation orders and preparedness levels. I know that hurricane watches and warnings do perform much of this role, as it relates the swath of destructiveness along the coast. More to the point, the coastal warnings could be tailored to the category level of wind, if it is not done so already. However, the point metric might help psychologically by giving people a better mental picture of the scope of the danger. Since it is a real metric it would serve more than just a mental function as it could help with federal disaster preparations and speed up response times by serving as an additional trigger for federal assisstance.

I could not find good information on the NHC site that would help me craft a base profile for rating the radial extent of hurricane winds. I am thinking that perhaps there should be a .0-.5 scale with .0 as either a base hurricane or a "normal" hurricane of that category. The point metric may be based either on physical measurement (e.g. a 50, 75, 100 etc mile radius) or on a geometric factor extrapolated from a normal storm for that category. The metric might even be a compilation of additional factors such as footprint symmetry of the actual storm verses an "normal" circular storm, but I want to keep it simple.

Comments?

[NEOWatcher]

It seemed to some that Katrina was merely a Catagory 4 hurricane on the Saffir-Simpson scale and many compared that to Camile that was a Cat-5 storm. However, Katrina was a very powerful Cat-5 (but Cat-4 at eye-landfall) and was very wide as well. So I ask: Should we construct a new hurricane rating scale that reveals more information?

Do you think that Katrina was more powerful than Camile? Until the levees broke, I didn't see much more damage than from Camile. Here's a sat-pic of Camile before landfall, it's huge (no, not hugo).
Maybe I'm not understanding why you think that there's a problem with the current scale. I thought that the scale was intended to convey severity by "potential" damage, therefore any specific differences are not as important as an overal measurement.

The current Saffir-Simpson Hurricane Scale rates the storms 1 through 5 by wind:
Tropical Depression up to 38 mph
Tropical Storm 39-73 mph
Cat 1 = 74- 95 mph (21 mph range)
Cat 2 = 96-110 mph (14 mph range)
Cat 3 = 111-130 mph (19 mph range)
Cat 4 = 131-155 mph (24 mph range)
Cat 5 = 155+ mph (undefined range)

How about one related to news coverage?
Cat 1: Hits Puerto Rico or Cuba
Cat 2: Hits Bermuda
Cat 3: Hits US in a non-populated area
Cat 4: Hits Florida
Cat 5: Hits a major city

The NOAA site does list some other technical information related to the rating, such as the Storm Surge, yet it is not made clear if this is simply a result of the primary measurment (wind) or if it is actually included in the calculus. However, this Wikipedia article does claim that the NHC added Storm Surge effects.

It is my suggestion that perhaps we should include an extra dimension of measurement such as the size of the storm, the millibar measurment, or perhaps use a arithmetic or logarithmic metric, similar to the Richter Earthquake Scale.

Storm surge is related to the pressure readings. (maybe not directly, but close enough for a rating)

I was thinking that perhaps a point metric based on the radius of either maximum sustained winds or just cat-1 sustained winds might be added. It might use a 1-5 (or 0-4, 0-9?) range that the meteorlogists could later define with 1 being a narrow storm and 5 being a wide storm. So a small weak storm might be a 1.1 while a storm that is both moderately strong and wide would be 3.3 and an extremely strong storm that is really wide would be 5.5. Katrina (2005) might be a 4.5 or a 5.5 and Charley (2004) would be a 4.1 or 4.2. Or would a Alphabetic appendage (4A for Katrina, 4E for Charley) be preferable?

I would think that you would just increase the warning area, since the people that are being hit won't be affected by the radius, but only the fact that that severity has reached them.

[Ara Pacis]

Interesting post, neowatcher.

1a: no, I was not meaning to necessarily compare it to Camile, only that others have done so.
1b: No problem with SSHS, but SSHS is an intensity rating. I think it could be improved by including breadth information.
2: Funny, send that one to the Daily Show.
3: I know.
4: Yes, they could increase the warning area (as mentioned in my last post) but the people being hit will be affected by the radius. If two storms strike the same location the people that live near them will be affected more severely by a wider storm with stronger winds at their range than a smaller storm. The measure of the width or breadth is not manufactured, its a simple datum and its inclusion in the metric would not be superfluous.

[Launch window]

they should have used the terror alert levels



Powell criticizes response to hurricane

Ex-secretary of state sees 'a lot of failures'

http://www.msnbc.msn.com/id/9268656/

[jfribrg]

I forget which one, but a few years ago a hurricane stalled off the east coast of Mexico for several days and dumped several feet of rain, causing massive flooding and mudslides, and killed IIRC several thousand Mexicans. This was "only" a cat 1 or maybe a cat 2, but because it just sat stationary (like Ophelia), it caused tremendous damage. The problem with the category system, is that it is just one number. Camile wasn't as damaging because the hurricane force winds didn't extend too far. Of course the US press only paid attention to to
Instead of a single category, I propose a 3 part designation:

Part 1 would indicate maximum sustained winds, using the current category designation, although I would like to see a cat 6 for winds over 180

Part 2 would be based on a double integral of the hurricane force area, using the wind speed as the two dimensional function to integrate over. It would be a kind of total wind metric. I'm not sure what units to use, but a logarithmic scale would be useful.

Part 3 would indicate maximum rainfall expected over a point that is about to experience the storm. Since the other two metrics are based on a point in time, this one would also need to be based on a point in time, so this doesn't indicate the most rain that did fall on some point, but the most rain that would fall on a point if the storm momentum, size, and strength doesn't change.

For instance, that might make Camile a category 5-2-4 while Katrina would be a 4-5-2 and Ophelia 1-1-4. I don't think it would be long before the public would learn the designations and how to interpret them.

One final note: the worst possible storm under this classification would coincidentally be 6-6-6.

[Argos]

Some argue that the rising ocean temperatures could trigger more powerful cyclones. But I think that a key parameter for cyclone formation and development is the atmospheric pressure. A hypothetical Cat 6 would have to develop from very low pressure systems, in the range of 880 milibar. Is that possible? So I´m guessing that the warming oceans can only have a quantitative impact on hurricane formation.

[publiusr]

Tropical Cyclones run into a wall beyond CAT 5. Katrina chured up the ocean as a Kat 5 and the swell remained after the dry punch weakened it a bit.
It would take astroid strikes or subsea volcanism to have the hypercanes that Kerry Emmanuel predicted.

[aurora]

Is that a prediction?


Where do you get your information? I'd like to read that article.

Don't know what the other poster was referring to, but try this article that just came out today:

Large Hurricanes becoming more common

[ElWampa]

Is that a prediction?


Where do you get your information? I'd like to read that article.

He could be referring to this story.

[Chip]

Tropical Cyclones run into a wall beyond CAT 5. Katrina chured up the ocean as a Kat 5 and the swell remained after the dry punch weakened it a bit. It would take astroid strikes or subsea volcanism to have the hypercanes that Kerry Emmanuel predicted.

Perhaps, but there have been more powerful hurricanes. The "Florida Keys Hurricane" of September 2, 1935 (also known as the "Labor Day Hurricane") had winds of between 200* to 250** mph in the eye wall, and a storm surge of 18 feet wiping out a railroad of escaping workers.

* http://thefloridakeys.com/history.htm
**History Channel

[Ara Pacis]

So, I am thinking Rita might be a 5.4 or even a 5.5 right now. Agree, Disagree?

[CalabashCorolla]

Some argue that the rising ocean temperatures could trigger more powerful cyclones. But I think that a key parameter for cyclone formation and development is the atmospheric pressure. A hypothetical Cat 6 would have to develop from very low pressure systems, in the range of 880 milibar. Is that possible? So I´m guessing that the warming oceans can only have a quantitative impact on hurricane formation.

Pressure is indeed a critical parameter to look at, especially when trying to determine whether a storm is weakening or strengthening. Meteorologists give credence to a storm's pressure over estimated winds in almost every forecast exercise. However, there may be a practical limit to how low sea level pressure can go, and I think we've seen that limit grazed already: Supertyphoon Tip set the worldwide low record at 870 mb in, I believe, 1979.

Hurricanes, once they get to a certain point in their development, face an uphill struggle to even maintain their strength, much less add to it. The Gulf storms this year have had the extremely fortuitous (though not unprecedented) advantage of the combination of a massive ridge over most of the US, almost no steering/shearing currents aloft, and bathwater-temperature sea surface temps due to there being pretty stagnant (and thus non-upwelling) air near the surface. Rita especially had an intensity roller-coaster ride, as she started to hit areas of slight shear northeast of the Yucatan peninsula which started her on her downward slump. Typhoons over the Pacific have the advantage of larger stretches of water over which to intensify, but even they are slaves to upper atmosphere conditions and phenomena such as cold eddies, upwelling, and the like.

It is common to assume that warmer ocean temps will lead to stronger storms, but this is not the whole story. Warmer seas do help storms to intensify, but there are many other factors which can make or break storms; and, the strongest storms may seem to "ignore" some bad influences while completely changing character at others which seem almost negligible. We are just now starting to understand the roles of atmospheric oscillations such as El Nino-La Nina in tropical storm development, and talk abounds of 20 to 30-year cycles of peak hurricane activity, which would make any of the "intensity of storms has increased since 1970" arguments moot. Perhaps the best way to determine the role of climate change in hurricane formation will be to wait and see how it actually plays out; we may be in for some surprises down the road.