western pacific Typhoon Goni

[Somerset Squall]

The active 2015 Western Pacific season continues with the formation of the sixteenth tropical depression of the season, located about 300 miles east-southeast of Guam. Deep convection is persisting over and to the west of the LLCC. The environment is moderately favourable with low shear, warm sea temperatures but suppressed poleward outflow due to troughing to the northwest. Therefore, steady strengthening is expected at first. As the trough pulls away in a day or so, poleward outflow will increase, perhaps allowing a period of rapid intensification as the other parameters remain favourable. JTWC expect 16W to be a 120kt typhoon by day 5.

The steering environment is fairly complex. A west-northwest track is expected initially, followed by a slow turn to the north-northwest as some steering influence transfers to a building ridge to the southeast. The track should then flatten back out to the west as ridging to the north becomes more dominant. This kink in the track should ensure 16W passes north of Guam.

Edited August 14, 2015 by Somerset Squall

[Recretos]

Goni also looks nicely organised by HWRF.

Edited August 15, 2015 by Recretos

[Somerset Squall]

16W became Tropical Storm Goni yesterday, and has since gradually strengthened to 50kts. Outflow is gradually improving in a poleward direction, which should allow some faster intensification to begin soon.

[Somerset Squall]

Goni has continued to strengthen, and now has winds of 60kts. Further strengthening, perhaps rapid, is expected. Ridging to the north is expected to become strong, so a faster westward motion is expected to begin soon, and then persist. By the end of JTWC's forecast, Goni is expected to be threatening Taiwan, which is concerning so soon after Typhoon Soudelor's impact.

[Somerset Squall]

Goni has become a typhoon, and at the 9pm JTWC update, had winds of 80kts. However, the typhoon has now developed the dreaded pinhole eye, embedded within the symmetrical central dense overcast, which itself is flanked by strong, spiral banding. Goni is clearly undergoing some pretty rapid intensification right now.

Edited August 17, 2015 by Somerset Squall

[Somerset Squall]

Goni became a category 4 on the SS scale this morning, with winds of 115kts. The typhoon has since stopped strengthening due to renewed subsidence to the north of the system, suppressing outflow in this direction. This subsidence is now forecast to produce some weakening of Goni in the near term. As outflow improves again in a day or so, intensification is expected to resume.

[Somerset Squall]

Goni has weakened to 100kts, cat 3. Poleward outflow continues to be impeded, but the environment is forecast to improve again, and Goni is expected to regain cat 4 status. Track favours a continued westwars track along the south side of ridging to the north, followed by a turn to the north just east of Taiwan as a trough creates a weakness in the ridge. At this point, weakening will occur again as shear increases.

[Somerset Squall]

Goni has reached category 4 status again, with winds of 115kts. The eye has become much better defined, and the convection more symmetrical as the poleward outflow has expanded as the subsidence has decreased to the north. Goni is expected to reach a new peak of 130kts (super typhoon strength), before raking eastern Taiwan. The typhoon is then forecast to recurve northeastwards towards Okinawa.

[Somerset Squall]

Goni did not strengthen beyond 115kts. The typhoon has grazed northern Luzon and has consequently weakened due to land interaction. Winds are down to 90kts. Goni is turning to the north, away from Luzon. Some slight reintensification is possible as land interaction becomes less of an issue, before weakening then occurs as shear increases and waters cool as Goni accelerates to the northeast.

The current track forecast points to a landfalling typhoon in southwestern Japan. Although Goni will be weakening at this point, if this track verifies, the impact will be quite severe.

[Somerset Squall]

Goni weakened to 80kts last night but has since restrengthened to 90kts. The eye has become better defined and has renewed, deep convection surrounding it. Dual outflow channels have developed, in a poleward and equatorward direction. Shear is also low and waters warm through the Japanese Islands. JTWC therefore forecast restrengthening to 100kts (cat 3). The track forecast is still largely the same with an impact to SW Japan likely after moving through the islands. Goni is then expected to turn northwards, grazing the east coast of South Korea before making a final landfall in a very weakened state in the mountains of North Korea.

Imagery showing a much healthier Goni:

Edited August 23, 2015 by Somerset Squall

[Somerset Squall]

Goni has reached a 115kt intensity (cat 4), for the 3rd time. The eye remains very well defined embedded in a symmetrical central dense overcast. Goni is raking the islands to the east of Taiwan hard, with the eye passing over the Yaeyama Islands this afternoon.

[Somerset Squall]

Goni made landfall in SW mainland Japan as a 110kt vat 3 typhoon last night. It is now weakening, with winds at 80kts as it swings north into the Sea Of Japan. Extratropical transition is imminent as the storm moves over cold water.

[Somerset Squall]

Goni has become extratropical, just before landfalling near Vladivostok, Russia.