southern indian ocean Intense Tropical Cyclone Emeraude

[Somerset Squall]

Finally, another tropical storm forms in this record breakingly quiet southern indian ocean season. Emeraude is located in the central/eastern portion of the basin, well west of Cocos Island. The storm has well developed banding features surrounding a fairly intense core of convection. This is a sign of a healthy and maturing storm. JTWC initiated advisories on ther system at 9pm past night, with winds of 40kts. I suspect this will rise at the next update (9am). Some fairly rapid intensification seems likely given the structure of Emeraude and the low shear and good outflow it is experiencing. The storm is expected to drift east, then south, then back to the west in the coming days as the steering environment shifts between ridges to the north and south. Emeraude is not expected to affect land, which is just as well as it is expected to become quite intense.

Edited March 18, 2016 by Somerset Squall

[Somerset Squall]

Emeraude has rapidly intensified and now as winds of 90kts, a cat 2 on the SS scale. The cyclone has developed a pinhole eye, embedded in cold cloud tops with strong banding features surrounding the inner core. Further rapid strengthening is expected, with a peak of cat 4 on the SS scale forecast.

[Somerset Squall]

Emeraude has continued to rapidly intensify and now has winds of 125kts according to JTWC, a solid category 4 on the SS scale. Further intensification is possible over the next 24hrs, before environmental conditions worsen as Emeraude picks up speed on a southeasterly track.

 

[Vorticity0123]

It is quite amazing to me how Emeraude has gone in 2 á 3 days from a tropical depression all the way up to a severe hurricane, and back down to a dishelved tropical cyclone! A satellite image from this morning shows there is not much left of the once-powerful tropical cyclone Emeraude.

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Satellite image of TC Emeraude as of 18-03 04:30 UTC.

In fact, judging from this satellite image, one could argue that the low level circulation center (denoted by an x, visible by the low level clouds) is about to become exposed to the northeast of the remaining convection. One could doubt whether this is really still a hurricane Over the past few hours, though, convection has rebuilt a little over the center again, so maybe Emeraude will slowly start to reorganize again.

CIMSS satellite intensity trends nicely capture the rapid strengthening followed by almost just-as-rapid weakening.

CIMSS ADT satellite intensity estimates for Emeraude.

What about the reasons for this weakening? The cloud pattern does not look like shear has been the main inhibiting factor, though there seems to be some northeasterly shear over the system (explaining why the convection is blown to the southwest of the system). The main reason to me appears that upwelling of cold ocean water has led to the weakening of the cyclone. This is because Emeraude has been sitting over the same ocean waters for about 24 hours now. Once it moves away to the southeast from its own cooled waters, it should be able to restrengthen again. Nevertheless, interesting to witness how quickly a cyclone can spin up, and spin down just as fast!

 

[Somerset Squall]

Indeed Vorticity, I think upwelling is a factor as Emeraude is now tracking back southeastwards over it's previous track. Winds are down to 85kts according to JTWC, but I agree, this could be a generous assessment. It does look like Emeraude could restrengthen in a day or two as it moves back over warmer water and into a temporary period of lower shear.

[Somerset Squall]

Looped track:

 

 

Edited March 18, 2016 by Somerset Squall

[Somerset Squall]

Emeraude weakened to 60kts but has since re-intensified to 70kts. The storm is under low shear and warm sea temperatures, but is struggling with dry air. Nonetheless, Emeraude should intensify some over the next day or two as the track shifts to the west as a ridge to the south begins to dominate. Emeraude is currently forecast to have a second peak of 80kts, then weaken as outflow becomes choked once more. Currently, by day 5, Emeraude is forecast to turn south as an approaching trough weakens the ridge. This trough could increase poleward outflow which could provide a third round of intensification at this time. Due to the complex steering environment and varying upper level conditions, the forecast is subject to change and is of low confidence.

 

[Somerset Squall]

Emeraude has weakened, not strengthened. Upwelling of cooler waters is a factor that combined with increased shear to weaken the system to 30kts. JTWC have ceased warnings on the system, stating that there is a chance of regeneration as the remains of Emeraude travel west into a potentially more favourable environment (certainly over warmer water anyway). For now, Emeraude is no more.

 

Certainly a very odd track. Emeraude has actually completed a full loop and has degenerated into a remnant low pretty much where it formed a week ago.