Tropical Storm Goni

[Somerset Squall]

Invest 93W has become Tropical Depression 08W just to the west of the the Philippines in the South China Sea. The depression isn't very well organised at the moment with deep convection shrinking over the last 12hrs and banding features being non-existant. However, there is a closed circulation which extends down to the surface with sustained winds of 30kts, hence the decision to upgrade the system was made by the JTWC.

The precursor to 08W has been moving generally west over the last few days. However, this motion is not expected to continue. A building anticyclone to the east of the depression is expected to force 08W northwards towards the south coast of China, with landfall east of Hong Kong currently looking most likely. If the ridge fails to fully build, landfall could occur nearer Hong Kong. This kind of set up has happened many times before; a north to northeast track is forecast yet the system heads northwestwards. We shall see.

As 08W isn't looking overly impressive at the moment, further intensification will probably be slow as the depression is in it's formative stages. In addition, 08W doesn't have all that long over water. Therefore, I think the JTWC's forecast of a 35kt peak is pretty reasonable. I wouln't be entirely surprised if the system failed to make storm status at all. The primary concern from 08W will be rain.

[Cookie]

PASAGA - have named it jolina

thanks for the updates SS

[Somerset Squall]

08W has not become any better organised today. This morning, shear increased and exposed the LLC, but now convection has re-built nearer the centre as shear is relaxing again. However, 08W looks no better than last night with a lack of defined banding and little convection on the northern side of the circulation. The system is not likely to strengthen prior to landfall near Hong Kong.

[Somerset Squall]

Although convection is still lacking to the north of the LLC, the coverage has expanded over the last few hours with signs of banding to the southeast. This has prompted JMA to upgrade 08W to Tropical Storm Goni, with intensity now at 35kts. As shear has eased and Goni is becoming more organised, the storm has potential for a little more strengthening prior to landfall late tomorrow or early Wednesday. Fickle things tropical cyclones!

[Ross B]

Keep getting an error so i cant seem to edit the title, will have a go in the morning if it works...

[Cookie]

very fickle

[Somerset Squall]

Keep getting an error so i cant seem to edit the title, will have a go in the morning if it works...

Cheers Ross

Thanks for posting that tracking chart Cookie. Clealry shows the ridge to the east didn't build as strongly as forecast, and as I mentioned might happen, Goni is drifting west-northwestward. I think landfall will occur just north of Hainan Island now. A big shift as ti was initially forecast to make landfall to the east of Hong Kong!

[Cookie]

it always amazing me how many twists and turns these things have and how much affects them.

[Somerset Squall]

Goni is now making landfall west of Hong Kong as a 45kt tropical storm. Goni strengthened more than predicted as waters remained warm right up to the coast and shear was lower than progged which allowed the storm to get it's act together. High winds and torrential rains are now spreading inland, but rain will still be more of a concern that wind with this one. Goni will rapidly dissipate over land as shear increases, the air becomes increasingly dry and land interaction takes it's toll.

[Cookie]

weakend over land

[Somerset Squall]

The remains of Goni are still prviding heavy rains for the western half of Hainan Island and are slowly spreading westwards into northeastern Vietnam. The ill defined remnant low is only providing sustained winds of 20kts (too weak to classify as a tropical cyclone), but a concentrated area of convection lingers midway between Hainan Island and Vietnam. This low pressure area doesn't look like it's going to move anywhere fast, and is likely to cause some flooding in both areas. Just goes to show even when a TC degenerates into a weak tropical low it can still cause severe weather.

Whilst the system that became Goni was still an invest, it killed 8 people and left a further 5 missing in the Philippines due to flooding.

[Cookie]

that's not good at all

[Somerset Squall]

The circulation of Goni has become much better defined over the warm waters between Hainan Island and northeast Vietnam, and convection has continued to expand. As a result, Goni has been re-upgraded to a 35kt tropical storm. Goni is currently moving southwestwards, but a westerly steering flow should turn Goni to the southeast or east. Then, a steering ridge is forecast to build southeast of Goni, which will force the storm northeastwards. The ridge is then forecast to build northwards and re-orientate itself to the east of Goni, forcing the storm northwards back towards China again. A very strange track forecast indeed, with the net result being Goni rotating ant-clockwise to make landfall at around the same place as it did initially. If this forecast verifies, then the situation is looking grave indeed as Hainan Island and surrounding areas will receive yet another dose of torrential rains.

Track of Goni:

Goni is expected to re-intensify to a strong tropical storm, perhaps stronger than it's first life. JTWC currently forecasting a secondary peak of 50kts. Goni's "first life" peaked at 45kts.

What a turnaround! Literally. Really wasn't expecting this!

[Cookie]

wow, never fails to suprise us do they!

[Somerset Squall]

Goni has been downgraded to a 30kt tropical depression this morning. It appears the system is suffering at the hand of 20-30kts of wind shear, displacing convection west of the LLC. This shear is shown on the CIMSS shear product:

(Goni is located between Hainan Island and Vietnam, the small, sheared blob to the left of the image.)

However, the shear tendancy charts show shear slowly easing in the area:

(Goni is the left "L" in the image)

This means Goni still has the oppurtunity to recover into a tropical storm, though JTWC have revised the intensity forecast downwards in line with the current weakening.

Track forecast is largely the same as before. Goni is currently heading southwards as forecast and is still predicted to execute a large anti-clockwise loop around Hainan Island. It is important not to directly focus on the landfall point on the coast of China however, as this is likely to shift and change.

[Cookie]

thanks for posting those charts mate

[Cookie]

has been proudcing a lot of rain fall and caused flooding.

[Somerset Squall]

Goni has degenerated into a remnant low again. High shear in the range of 30kts has persisted against expectations and has decoupled the low and mid level circulations of Goni and significantly reduced convection. As a result, Goni no longer qualifies as a tropical cyclone. Shear is still expected to ease but it may be a little too late. There is a small chance of Goni re-developing so it needs watching.

[Cookie]

some of the rainfall totals from Goni

[Somerset Squall]

Some seriously impressive totals there, especially for such a small storm! Just proves that a storm doesn't have to be big or intense to cause damage/flooding.

[Cookie]

I know Hong Kong has very good set up for dealing with flooding and heavy rainfall with underground tunnels etc.

are the other countries as good as deal with the amounts of rainfall and flooding?