southern indian ocean Tropical Cyclone Joalane

[Somerset Squall]

Another tropical cyclone has formed in the South Indian Ocean, this time about 400 miles northeast of Mauritius. 22S has winds of 35kts according to JTWC, but has yet to be named by MeteoFrance, though I suspect this will happen soon. Deep convection is expanding over the LLCC, and conditions ahead look favourable for further strengthening.

22S is being steered west-northwestwards along the north side of the subtropical ridge to the south. This ridge is expected to weaken, and a new ridge is expected to develop to the northeast in a few days. This is expected to drive 22S southwards then southeastwards in a couple days time. This track puts Rodrigues in the path of 22S later down the line, though, as ever, the track forecast is subject to change this far out.

Edited April 10, 2015 by Somerset Squall

[Somerset Squall]

22S has become Severe Tropical Storm Joalane. Winds are at 55kts (1-min sustained). Joalane appears to be rapidly strengthening, with an eye already popping out from the central dense overcast, and excellent spiral banding features now evident. Conditions appear highly favourable for further significant intensification. Rodrigues need to pay close attention to Joalane.

[Somerset Squall]

Rapid intensification is continuing, with winds now at 80kts according to JTWC. JTWC expect Joalane to become a cat 5 on the SS scale, which would make it the 3rd of the season (the others were Bansi and Eunice). This would a pretty unusual occurence if Joalane does indeed make cat 5.

[Somerset Squall]

Joalane strengthened to 90kts last night, but has not since intensified any further, with winds still at 90kts. Joalane has injested dry air, which really affected the convection around the eye this morning. There has since been a little recovery in that regard, but Joalane certainly doesn't have a solid central dense overcast anymore. JTWC have backed off the cat 5 forecast, but still expect a cat 4 peak of 120kts.

[Somerset Squall]

Dry air has continued to plague Joalane, providing quite a bust forecast for JTWC, and indeed MeteoFrance, who were also forecasting much more intensification than has actually occured. Instead of strengthening beyond 90kts, Joalane has weakened to 75kts overnight. Joalane is now forecast to further weaken as shear gradually increases and waters cool on the southwards track. The other bit of good news is that Joalane has taken a track much further east than originally anticipated, meaning Joalane is staying well east of Rodrigues.

[Somerset Squall]

Joalane has unexpectedly restrengthened to 90kts. Convection has deepened around a large eye. Excellent outflow has allowed Joalane to mix out the dry air and intensify. Shear will soon rise, and waters cool along track, so this intensification trend should be brief.

[Somerset Squall]

Joalane's winds have fallen to 55kts, and the cyclone has commenced extratropical transition, as evidenced by the convection free centre and broadening wind field. JTWC have issued their last advisory.