Topic: Worldwide Cyclone Category Ratings Comparision

[Jeff Brislane]

Hi Eveyone,

I thought I would start this new thread for discussion so I don't end up hi-jacking another thread allthough I would have liked to have posted some information there. In regards to this comment made on another tropical thread.

Basically our system (cyclone catagory's) is a reflection of the relative occurence of cyclonic strength: In the US they see alot more strong Hurricanes(>Cat3)

This is not how the BoM devised our cyclone rating system. Every region in the world actually rates cyclones differently for example in the north west pacific they don't even use catagory numbers and yet they get the most powerfull cyclones on Earth! They rate their Typhoons by name from Tropical Depression to Tropical Storm to Severe Tropical Strom to Typhoon. The BoM's rating system is based on different factors to the Saffir/Simpson Scale. The most notable being that our system is based on estimated maximum wind gust's where as the Saffir/Simpson scale is based on 1 minute average sustained wind. Note also that we measure our sutained cyclone wind speeds on 10 minute averages not 1 minute like they do in the U.S.

Also our rating takes in the fact that Cat 1 and 2 cyclones are still cyclones. With the saffir/simpson scale you can have a cyclone that's rotating but it's not yet a hurricane.

Note also that the Saffir/Simpson scale has narrow confines for the Cat 2 rating compared to Cat 1 and Cat 3. I think it's fair to say that each system is simply different. I personally prefer the non-numbered catagory system as it promotes an easier understanding of the potential threat to life and property than a number does.

Jeff. 

[Jeff Brislane]

Actually Super Typhoon is only used by the American JTWC. I was refering to the other North West Pacific Typhoon Rating scale, but i do prefer to use Super Typhoon for the strongest storms.

Our system also bears the most scientific accuracy as the term Tropical Cyclone is the proper scientific term for such a storm and as i've already stated our system allows us to name weaker storms as Tropical Cyclones than the S/S scale thus allowing us to recognise the characteristics of a proper cyclone earlier on. To say that a storm is not a hurricane but only a tropical depression when it has all the active ingredients of a "Cyclone" is flawed imho.

I would also like to see how strong some of the sustained winds were in North Atlantic Hurricanes if one was to use a 10 minute average instead of only 1 minute.

[orage]

This is a table I found on Wikipedia comparing worldwide Tropical Cyclone ratings...

[Mike]

Hi all.  I agree with your rating scale - you'd think there'd be some uniformity to all these storms considering the ingredients are the same except for NH circulation! As for 10 minute wind gusts - yes to that - but if the gusts was prolonged for over a minute would the equipment fail?  That's been the bane for many years - measuring systems failing. 

I guess they use one minute increments due to the winds not actually being sustained as such for long periods - i think what their after is short, sharp, intense wind indicators to reflect whats happening within and around the system.  We all know that wind does not sustain a constant velocity continuously - hence the gusts.  This get's into the realms of science to which I'm not all that skilled! - but would certainly welcome scientific viewpoints from those that are in the subject of wind.

Mike