Tropical Cyclone Dongo

[Somerset Squall]

Invest 98S (which absorbed the remnants of TC Billy) has continued to become better organised today and has been upgraded to Tropical Cyclone Dongo, the first tropical cyclone worldwide of 2009. Dongo's intensity is currently at 30kts but further intensification is expected as shear continues to ease, sea temps are high and poleward outflow is expected to remain good. Dongo is currently moving southwestwards and is expected to turn south soon as a subtropical steering ridge builds stronger to the east. On this track, Dongo shouldn't be a significant threat to land. The track will also eventually take Dongo into colder waters but this is a few days away yet.

Forecast track for Dongo:

The image below clearly shows the improved organisation of the system with excellent banding features and convection slowly increasing near the well defined centre:

[Cookie]

thanks for the update mate, have you ever know anything like this before?

found a good image

[Somerset Squall]

thanks for the update mate, have you ever know anything like this before?

found a good image

Nice image there Cookie- thanks for posting.

Well, Hondo last year was a remnant low for 8 days before redeveloping, that's a recent example of a long lasting remnant low I can think of. Of course, Billy didn't redevelop but the fact that the low survived all the way across the Indian Ocean is very unusual. I guess it helps that it is a large expanse of ocean with very little land to interrupt circulations.

I really thought Billy would redevelop. Convection fired really well around the centre but the larger low (now Dongo) absorbed it. Remember the Fujiwhara interaction between Fame and Gula last January? I guess the same thing happened here except both systems were below tropical cyclone strength. The new low was much larger so it had influence over the remnant low of Billy. I expect if the new low wasn't there Billy may well have redeveloped- then that would truly be a very rare event!

As for Dongo now, structure remains impressive, as clearly shown on your image. Dongo has had problems maintaining convection near the centre but in the latest satellite images it seems that this is no longer such a problem. This probably means Dongo can now start intensifying proper- MeteoFrance are particularly keen on forecasting some rapid intensification, may make cat 1 on the SS scale before reaching colder waters in a few days time.

Also worth noting is that really long feeder band stretching all the way round the east and to the north of the storm. This is no doubt feeding the renewed convection near the centre. Looks magnificent on that image, stretches for hundreds of miles!

[Cookie]

thanks for that somerset. very intresting to know,

can't understand why more weather nutters like us are intrested in this!

its so intresting!

[Somerset Squall]

Dongo has slowly intensified today and intensity has reached 40kts. The storm is heading southwards on the western side of a steering ridge anchored to the east. This track will continue for the next day or so before Dongo weakens and gets caught in the jet stream to the south which will induce extratropical transition in around 48hrs time. The weakened storm will then drift eastwards in the jet flow. Before this occurs, some further modest intensity gains may occur as shear remains low and outflow remains good. Sea temps are sufficient for now but nothing amazing and will quickly cool in a day or so as Dongo moves briskly south.

[Cookie]

thanks for the update, I want bealive this system is over untill its really gone and has no chance of a come back

[Somerset Squall]

thanks for the update, I want bealive this system is over untill its really gone and has no chance of a come back

Indeed!

Dongo is finally keeping some real convection near the centre. As I said yesterday, Dongo was having a little issue doing this but he finally looks more impressive on latest satellite imagery (there were even small hints of a partial eyewall earlier):

[Cookie]

yup he is starting to look good,

you mentioned a possbie threat to land a few posts back, is that still the case?

[Somerset Squall]

yup he is starting to look good,

you mentioned a possbie threat to land a few posts back, is that still the case?

I think this one won't effect land at all. On the southward track there is just ocean, a refreshing change to know this one won't cause any damage (unless there's a dramatic shift in track!).

[Cookie]

never mind, no idea why I thought it might affect land, strange :lol:

[Somerset Squall]

Intensity has increased to 55kts overnight, and there is potential for a little more strengthening in the next 12 hours before shear increases and sea temps cool. Dongo maintains some deep convection over the centre and some impressive banding features. Convection will begin to decrease as Dongo continues heading southwards or southeastwards and begins extratropical transition. Dongo could become quite a powerful extratropical storm in the Southern Oceans next week.

[Somerset Squall]

Dongo is falling apart now under heavy wind shear and over increasingly cold waters. Dongo has accelerated significantly southeestwards today, track speeds were at 18kts earlier which has meant Dongo has met the unfavourable conditions much sooner than anticipated. I expect Dongo to make extratropical transition very soon.

[Somerset Squall]

Dongo has been racing southeastwards out of the tropics. The storm is now fully extratropical with no deep convection near the now cold cored centre.

[Cookie]

thanks as always for the great updates