SPAC: NARELLE - Post-Tropical

[cycloneye]

 https://x.com/VortixWx/status/2035179162881642789

[cycloneye]

[sasha_B]

The latest JTWC forecast calls for intensification to 115 kt off Australia's west coast by 18z Thursday, with remarkable RI of 65 kt in 48 hours, and 40 kt in 24 hours, anticipated in the leadup to that forecast point. There's a lot of time between now and then, though, and a lot could change - despite dramatically overperforming the forecast on its approach to Queensland, Narelle seems to have underperformed slightly in the Gulf of Carpentaria - but it seems like the JTWC, at least, expects a "repeat performance".

If Narelle DOES pull off that kind of intensification, it could challenge its own MSLP record; because it's anticipated to reach SSHWS Category 4 near 21S, with (much) wider forecast gale radii, it could plausibly reach a ΔP close to that of its pre-landfall peak even with weaker sustained winds. So I'm planning to come back and track this one once it's back over the water.

[Cargill]

If Narelle DOES pull off that kind of intensification, it could challenge its own MSLP record; because it's anticipated to reach SSHWS Category 4 near 21S, with (much) wider forecast gale radii, it could plausibly reach a ΔP close to that of its pre-landfall peak even with weaker sustained winds. So I'm planning to come back and track this one once it's back over the water.

Thanks for that ... interesting! I should re-emphasise how incredibly unpopulated the whole northern half of the Australian continent is - and the presence of regular cyclones is one very serious reason why this is the case. Along with the outrageously hot-humid weather, and terrible soil.

[cycloneye]

The new forecast track from JTWC has a closer path to the coast and that is why it now peaks at 100kts.

[Hurricane2022]

 https://x.com/i/status/2035734236448063571

[cycloneye]

Time over water is limited on the latest forecast from JTWC.

[cycloneye]

At 15z, peak is 95 kt.

[Hurricane2022]

C5 Severe Tropical Cyclone Narelle at peak intensity

[cycloneye]

The time over water is more and more short.

[sasha_B]

On the other hand, Narelle seems to be intensifying at a decent pace this morning. Let's see how far it gets.

[cycloneye]

The JTWC new peak goes up to 100 kt.

[sasha_B]

I'd place Narelle's current intensity around 55 kt and 986 hPa; subjective and objective satellite estimates both suggest a T# around 3.5. The CDO is a little lacking in symmetry, but there's very deep convection popping up near the center, and all signs point to a general strengthening trend.

The JTWC's forecast seems spot-on; I think a peak between 95 and 100 kt is the most likely outcome. But, if it intensifies rapidly from now through 18z on the 26th, it still stands a chance of peaking as a high-end SSHWS Category 3, imo. SSTs won't be much of a limiting factor over the next 48h, and the JTWC's prognostic reasoning doesn't consider frictional land interaction to be a limiting factor either (just a contributing factor to weakening after its anticipated peak).

The posts in this forum are NOT official forecasts and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or STORM2K. For official information, please refer to products from the NHC and NWS.

[cycloneye]

 https://x.com/GlobalCyclones/status/2036612612490699003

[cycloneye]

A faint eye trying to pop.

[sasha_B]

A faint eye trying to pop.

https://i.imgur.com/J1XUtrx.gif

Almost certainly 60～70 kt right now. Even if the eye isn't entirely well-defined, just applying the "curved band" pattern yields T4.0 (3.5 for 0.8～1.0+ banding on a log10 spiral + 0.5 for W or colder). If you apply the eye pattern, a ragged/elongated DG eye embedded in LG/MG yields T4.0～4.5.

[sasha_B]

Narelle was officially at 90 kt as of 12z, but may already be close to 100 kt (based on subjective T#s between 5.0～5.5, and ADT CI between 5.5～6.0). The JTWC is once again calling for a 115 kt peak at 12z tomorrow, which at this rate, I suspect Narelle could easily meet or exceed.

[cycloneye]

New peak is 115 kt.

[sasha_B]

....and now the forecast peak is up to 125 kt:

12 HRS, VALID AT:
260600Z --- 19.5S 115.5E
MAX SUSTAINED WINDS - 125 KT, GUSTS 150 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 050 NM NORTHEAST QUADRANT
060 NM SOUTHEAST QUADRANT
050 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 080 NM NORTHEAST QUADRANT
110 NM SOUTHEAST QUADRANT
080 NM SOUTHWEST QUADRANT
060 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 170 NM NORTHEAST QUADRANT
170 NM SOUTHEAST QUADRANT
120 NM SOUTHWEST QUADRANT
110 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 210 DEG/ 11 KTS

...which would nearly match its first peak for sustained winds. Narelle has made quite a comeback. Current intensity is 105 kt (per JTWC), based in part on the most recent subjective DT of 5.5. ADT CI is 6.3.

[sasha_B]

Subjective DT 5.5～6.5 (not clear to me at all where JTWC is getting 5.0 for the past two fixes; there are very few recent BD-enhanced IR frames that would support a fix that low). Objective DT has been between 5.9～6.5 over the past several hours, with CI resting near the middle at 6.3 (after discounting fixes that obviously missed the eye). A reasonable Vmax estimate for 26/0000～0100Z would be 115～120 kt, for which CKZ would yield 931～940 hPa, depending on how you assess the outermost closed isobar and average gale radius, given a fixed forward velocity of 10 kt and fixed latitude c. 18.8S. That's well short of Narelle's first peak by either metric, but still dramatically outperforming yesterday's expectations.