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Somerset Squall

Super Typhoon Choi-Wan

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Invest 93W continued to rapidly organise oevernight and became a tropical depression. It has since been upgraded to a 35kt tropical storm named Choi-wan. Choi-wan has an impressive circulation with good banding features and building central convection. Shear is set to remain low and waters warm, so further intensification is likely and I would be surprised if Choi-wan didn't become a typhoon. This storm has the potential to be a biggie.

Choi-wan is currently moving westwards a long way east of the Philippines, along the southern periphery of a subtropical steering ridge. It is unclear whether Choi-wan will effect land as yet, though the small island of Saipan look in for a bumpy ride int he next day or so.

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this has the hallmarks of a monster

its right slap bang in the heart of the HOT HOT waters.

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Indeed Cookie, that Wunderground sea surface temperature chart shows Choi-wan is over waters of at least 30C with some pockets extending to 32C. In addition, ocean heat content (this warm water extends down below the surface) is high, which should support an intense system,

Choi-wan is entering a period of rapid intensification it seems. Intensity has increased by 20kts overnight to 55kts. A central dense overcast feature has developed along with spiral banding fully wapping around the LLC. Choi-wan, as discussed above, is over very warm waters, and the upper level environment is also very favourable, with low shear and the prescence of dual outflow channels as evidenced on satellite imagery. These factors support continued intensification, perhaps rapid. Could we see the season's first super typhoon? We'll have to wait and see but JTWC forecast Choi-wan to be a cat 3 in 120hrs, though this could be conservative.

Tracking for Choi-wan has been fairly simple so far. The storm is moving generally west-northwest along the southern peripery of a subtropical steering ridge to the north. A weakness is showing in the ridge further west which may allow Choi-wan to eventually turn more northwestwards or even northwards in a few days time. The timing is uncertain, but this MAY take Choi-wan away from the Philippines/Taiwan and more towards China/Japan. We'll once again have to wait and see.

Cookie's image above shows the current organisation of the system well. Expect an eye to perhaps develop later today.

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Choi-wan has continued to intensify and is now a 65kt, cat 1 typhoon. Choi-wan is a large typhoon with a tightly wound inner core. The typhoon is located over hot waters and is still under a very favourable upper level environment. Therfore, further intensification is likely, and JTWC show Choi-wan peaking at 115kts in about 5 days time. Choi-wan does have the potantial to become stronger than this. The weakeness in the ridge to the north is still expected to produce a northwestward then northward turn, though the timing of this is still uncertain.

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what are those islands in it path are the inhabited?

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JMA Upgrades to Typhoon

TY 0914 (Choi-wan)

Issued at 00:45 UTC, 14 September 2009

<Analyses at 14/00 UTC>

Scale -

Intensity Strong

Center position N15°35'(15.6°)

E148°20'(148.3°)

Direction and speed of movement W Slowly

Central pressure 965hPa

Maximum wind speed near the center 35m/s(70kt)

Maximum wind gust speed 50m/s(100kt)

Area of 50kt winds or more Wide 130km(70NM)

Area of 30kt winds or more E440km(240NM)

W330km(180NM)

2009WP15_1KMSRVIS_200909140057.GIF

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Choi-wan looks more and more impressive. A small, very well defined eye is clear to see, embedded in the circular central dense overcast. Current intensity is 90kts (cat 2), but I expect this will increase rapidly this evening based on satellite loops. Saipan is being lashed by flooding rains and high winds. The small islands of Iwo-To and Chichi Jima look to be in the firing line next as Choi-wan begins to curve northwards into the weakness in the subtropical ridge to the north. Japan could be impacted thereafter, but Choi-wan may well head northeastwards and miss the country entirely whilst becoming extratropical. This will not occur for at least another 3 days and Choi-wan has until then to continue to intensify.

post-1820-12529529834937_thumb.jpg

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Choi-wan has indeed strengthened rapidly over the last 6hrs, and it is now a 120kt, cat 4 typhoon. Choi-wan is over hot waters and low shear, and also is benifitting from impressive radial outflow which is facilitating the rapid development. Cat 5 is certainly not out of the question, and the JTWC even forecast it to occur with intensity expected to peak at 140kts. It's not that often you'll get an agency forecasting a cat 5- they are usually more conservative. The again, Choi-wan is already an intense storm in a nearest to perfect environment you can get!

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Choi-wan is on the verge of becoming a cat 5, with intensity now at 135kts, making the cyclone a super typhoon. Conditions will remain favourable for the next 48-60hrs, so intensity changes will be governed by eye wall replacement cycles. As Cookie's images show, this super typhoon looks very impressive!

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Unsurprisingly, Choi-wan has been upgraded to legendary cat 5 status, with intensity now a whopping 140kts. This is the first cat 5 worldwide this year (though may be second if Jimena gets upgraded post season). Choi-wan could get stronger, the conditions certainly support it. Pressure is estimated to be 918mb, and the maximum potential intensity (MPI) from CIMSS indicates a possible low pressure of 894mb. It's not common for tropical cyclones to reach their MPI, but Choi-wan certainly has the chance to give it a good go!

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Wow what a monster! Are there any islands that could be at risk or is it just staying out to sea?

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What a storm! Jeez I hope that stays well away form any land!

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Wow what a monster! Are there any islands that could be at risk or is it just staying out to sea?

Iwo To and Chichi Jima still look at risk James. Choi-wan could still be a cat 5 as he grazes past them too. At the moment it looks like Choi-wan will move northeastwards to the south of Japan, but if it does shift further west, it should be greatly weakened by then.

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Can someone explain to me what the "CloudSat Reflectivity Zw" is / what it means etc...I dont know I've never seen it before =\

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