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WPAC, Indian Ocean, and Southern Hemisphere Tropical Cyclones

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It has been a somewhat slow Western Pacific Typhoon Season so far this year. The season started late in July, only four or five (depending on your choice in agency) typhoons have been observed so far, and ACE still remains a fair bit below 100*10^4 kt^2. Things may be changing though, especially with La Nina struggling to develop. At the time of this original post, Tropical Storm Meranti has just developed, and it may go on to be a very powerful typhoon.

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WV loop above will continue to update and stay current. (Edit: or not)

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Tropical Storm Meranti, now at 45kt, is expected to be 115 kt (category 4 on Saffir-Simpson) in 72 hrs. The GFS full resolution Meranti (see TropicalTidbits) has 915 mb, 115kt at 90 hours!! It will be near Taiwan. I suppose some uncertainty exists with respect to track.

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There seems to be a lot of consensus concerning Typhoon Meranti. It has strengthened from 45kt to 100kt since the last time I posted. The GFS ensembles and HWRF predict Meranti to approach Taiwan from the southeast and track through Taiwan. The JTWC now has a max intensity forecast of 135kt at Sep 13, 06z, a few hundred miles from Taiwan. Note: Category 5 Saffir-Simpson is 137kt and greater. Typhoons are not usually given Saffir-Simpson categories.

satellite image is from 0320z, which is from last night...18 hours old, it is 2134z right now. I have no idea why I can't find an updated satellite image.

 

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On 9/10/2016 at 0:44 PM, Chinook said:

Tropical Storm Meranti, now at 45kt, is expected to be 115 kt (category 4 on Saffir-Simpson) in 72 hrs.

Meranti just accomplished this in only 24 hours.  It's always very impressive to watch cyclones explode like this.

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Now I found satellite imagery that is up to date. This one is from 0120z September 12 (9:20 Eastern). I think the yellow areas are -80C, so that is some very cold -70C areas in a CDO wrapping around a narrow eye. Obviously the satellite based T-number must be very good and there is good outflow to the east and north.

BLwyCgd.jpg

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JTWC now forecasts Meranti to be 160 kt in 6 hrs (2:00AM Eastern). Isn't that close to Haiyan's peak intensity?



Haiyan was at a much lower latitude and had better upper tropospheric forcing. Probably the most incredible structure and symmetry we've ever seen in a tropical cyclone. I don't think Meranti can eclipse that. Inevitably, it is going to go through an internal structural change. It may have even peaked. As has been repeated, I wish they had recon over there.

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New JTWC forecasts take it south of Taiwan, meaning that there could be a greater wind speed when it reaches China (perhaps 105kt) near Chaozhou-Jieyang-Shantou metro. Shantou harbor is next to the sea, urban population 5.3 million.

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Yeah, looks like model consensus has shifted south as has JTWC's official forecast. Looks like the core will miss Taiwan and China's mainland will be dealing with a stronger intensity at landfall than previously forecast. This could end up the worst direct wind impacts at landfall for China for many years. The core will likely weaken and drop down to upper Category Three status due to internal reorganization and an expansion of pressure gradient /wind field, but Meranti may have a much larger core by then, affecting a larger area of shoreline with typhoon force winds.


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Not sure I fully buy into JTWC's 00Z intensity estimate of 160 kt. They're putting a lot of weight on SATCON for that estimate, which a notable deviation of standard policy for them. It could be correct for all I know, but the Dvorak Technique is the one with the proven track record. I know next to nothing about SATCON's verification.

201616W_wind_ssmis.gif

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Very close call for the southern tip of Taiwan. The cyclone will probably have a larger core by the time it is at closest proximity there. Even if the inner eyewall doesn't make landfall, it's very likely a concentric outer wall will impact land and they will experience typhoon force winds.

For later today, the 06 HWRF has the northern Batanes nearly in the southern eyewall. The town of Banco is in the NW inlet of Batan proper. They will likely experience typhoon force winds even if the eyewall misses the island to the north.




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Think I'm buying that 160 kts now. May be even higher. Very symmetrical and expansive cold ring and the eye has further warmed. Really impressive system. In reference to the comparison to Haiyan earlier, Haiyan had a slightly colder ring, but it may have been low-balled on its peak intensity estimates anyway.



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The last report from the airport in Banco, which looks like it positioned just under the southern and southeastern edge of the intense eyewall, reported sustained SW winds of 96 mph and gusts to 116.

https://www.wunderground.com/ph//basco/zmw:00000.1.98135

No reports out of the island of Itbayat.

EDIT: Whooooa there... Banco airport last report is S wind @ 122 mph, 150 mph gust. I don't think it was under the worst of the backside eyewall either.

Also looks like they're getting raked with a nasty intensifying outer eyewall.




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Itbayat, the island right in the eye, was last reporting N winds at 112mph with SLP at 933hPa...

Data equipment and communications obviously failed at the airport on Itbayat.

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