Cat 5 TC Narelle

[Ken Kato]

Cat 5 TC Narelle which is currently barrelling towards the Far North QLD coast with a pinhole eye and has now become even stronger than TC Yasi in 2011 in terms of currently estimated average and peak gust speeds (220km/hr average, 315km/hr gusts, and central pressure down to 926hpa per the 5pm analysis this afternoon).

It's likely up there with some of the strongest tropical cyclones ever recorded in the Australian region, despite the greater uncertainty with estimating the intensity of TCs in remote or oceanic areas in the pre-satellite era. TC Mahina back in 1899 would likely be only one of few that would beat Narelle.

Narelle went from Cat 1 to Cat 5 in only two days.

Not sure if we'll see much near realtime footage and on the ground reports coming out of that  given how sparsely populated the part of Cape York Peninsula that Narelle's forecast to affect, is.

Might be some a bit later, together with some post-damage aerial footage.

If Narelle doesn't weaken substantially before landfall, I'd be expecting to see complete defoliation of trees on the eastern coastal side of the Cape (and some of the islands) near where it makes landfall.

Narelle is far from done yet as a system and it's forecast to continue on a long path across the Gulf of Carpentaria, the NT Top End, and to northern WA or surrounding waters, though with varying levels of intensity. After that, the potential solutions diverge a lot with some taking it way off the northwest WA coast and others trying to curve it down towards southwest WA.

Below is the latest colour-enhanced infrared satellite image of the Narelle.

Ken.

[Gavin O'Brien]

Hi Ken,

Certainly, looks very impressive, thank heavens it is crossing a relatively remote area. I dread to think what would happen had it hit Townsville or Cairns.

Gavin

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[Blair Trewin]

OFFICIAL

Probably the best way to assess this is the Dvorak number (the satellite-based scale used to assess tropical cyclone intensity) – in general (unless there are other observations to alter the assessment), 6.5 is the lower cutoff for category 5 in the Australian system, 7.0 in the Saffir-Simpson system.

 

In the operational track Narelle's peaked at 7.0 (may change on post-event assessment). These occur a few times a decade in the Australian region (Yasi was a 6.5). The last 7.5 in the Australian region was Monica in 2006.

 

Blair

 

OFFICIAL

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[Ken Kato]

I've always liked the Dvorak technique, including the fact that it's been providing the same skilful baseline for TC intensity estimates for decades before all the various objective satellite aids such as ADT came onto the scene to lend an extra helping hand.

But it's a shame it can't go back into the pre-satellite era for some of the historic TCs, even if the pre-Dvorak intensity estimates back then weren't anywhere near as good as now and had to rely on a consensus of damage and anecdotal evidence, later modelling, and any available wind-measuring weather stations that a TC happened to pass close to.

The other issues in my view are that even though many of the basic principles behind the Dvorak technique to derive a CI number haven't changed for decades (hence, the advantage of consistency for recent historical comparisons), it's pretty subjective for certain "difficult" types of tropical cyclones over the ocean without the extra help these days from objective aids. It also often has an overestimating bias with weaker systems, and its constraints struggle with rapidly intensifying storms.

Nevertheless, still a very handy technique overall.

Ken.

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From: aust...@googlegroups.com <aust...@googlegroups.com> on behalf of Blair Trewin <blair....@bom.gov.au>
Sent: Friday, March 20, 2026 8:54 AM
To: aust...@googlegroups.com <aust...@googlegroups.com>
Subject: [austpacwx] RE: Cat 5 TC Narelle

To view this discussion visit https://groups.google.com/d/msgid/austpacwx/ME3P282MB2516533E4FB8F337A42AEFFAB94FA%40ME3P282MB2516.AUSP282.PROD.OUTLOOK.COM.