western pacific Super Typhoon Champi

[Somerset Squall]

Another tropical depression has formed, in the east of the basin, north-northeast of Pohnpei. 25W has winds of 25kts. Strengthening is forecast as the system heads west-northwestwards along the south side of a ridge to the north. In a few days time, as 25W passes north of Guam, sea surface temperatures will be lower and shear is expected to rise, which will likely stop or slow any further intensification.

[Somerset Squall]

25W became Tropical Storm Champi, and now has winds of 45kts. Shear is still displacing convection to the west of the LLCC, but hasn't been enough to stop the circulation of Champi becoming better defined over the last day. Shear is soon expected to ease, allowing for some more robust intensification. JTWC now expect a peak of 110kts before recurving northeastwards.

[Somerset Squall]

Shear has eased, and Champi has rapidly intensified, and now has winds of 90kts, cat 2 on the SS scale. Further rapid intensification is expected as the typhoon now has dual outflow channels and continues to move over very warm water. Champi is expected to recurve soon as it reaches the western extent of the steering ridge to the north. As Champi recurves, it will eventually run into higher shear and cooler water, initiating weakening then extratropical transition.

[Somerset Squall]

Champi's eye has cleared out nicely this morning. Winds are now at 105kts. Champi has slowed and is now moving northwards. Further intensification is expected, with a peak of 125kts being forecast by JTWC. Champi will continue to slowly move north then northeast towards Iwo To.

[Somerset Squall]

Champi is rapidly intensifying, with winds now at 130kts, a category 4 Super Typhoon. Champi is now expected to become a 145kt cat 5 before weakening. Koppu to the west failed to achieve this as it was so near land but Champi has another day or so of favourable conditions, so cat 5 is looking likely.

[Somerset Squall]

Champi has demonstrated just how hard intensity forecasting is with tropical cyclones. The typhoon has not strengthened, and has instead weakened by 25kts since yesterday, with winds now at 105kts. The reason for this is a trough to the northwest of Champi has gotten closer to the typhoon than expected, and it is causing subsidence and dry air in this quadrant of the typhoon. Shear is still low, and waters warm, but because of the subsidence and lack of poleward outflow, further weakening is expected, albeit slow. The northeast turn should materialise soon, and a few days later Champi will begin extratropical transition.

Edited October 19, 2015 by Somerset Squall

[Somerset Squall]

Champi weakened to 70kts for the reasons stated in my last post. The typhoon has only very slowly moved northwards over the last couple of days. As Champi has approached the mid-lattitude westerlies poleward outflow has vastly improved, and Champi has started to re-intensify. Convection is much deeper around the increasinly well defined eye. JTWC expect restrengthening up to 85kts, cat 2, before Champi accelerates northeastwards over cooler waters and increased shear, initiating extratropical transition.

[Somerset Squall]

Champi has strengthened considerably and now has winds of 100kts, cat 3 on the SS scale. The system has developed a huge, clear eye, surrounded by a doughnut-like ring of convection. Champi will probably keep this intensity for the next 12hrs or so before stronger shear affects the system.

Edited October 22, 2015 by Somerset Squall