By PDC’s Senior Weather
Specialist Glenn James
Tropical cyclone 14S (Vernon), is located approximately 973 NM southeast of Diego Garcia in the South Indian Ocean, and has tracked southwest at 08 knots over the past six hours.
According to the JTWC Warning number 12, sustained winds were 50 knots with gusts to near 65 knots.
Satellite imagery depicts a ragged and rather ill-defined ball of convection displaced to the southwest of an obscured low level circulation center (llcc). Over the past 12 hours, the convection has cycled continuously and at present cloud tops are in a warming phase. A microwave image showed the ragged llcc with the bulk of convective activity in a broad swath to the south, and only weak low level banding features to the north side of the circulation
Beyond than the vertical wind shear and dry air, the environment is otherwise favorable, with warm sea surface temperatures and robust poleward outflow.
TC 14S will continue tracking south-southwest for the next 48 hours, along the western periphery of the steering ridge to the east, and towards a weakness in the ridge pattern induced by the approach of a mid-latitude trough. The system will turn more southward by the end of the forecast as it begins to slow down slightly.
No significant environmental changes are expected in the first 36 hours of the forecast, with supportive sea surface temperatures and robust outflow competing with persistent northerly shear and dry air encroachment from the north.
The system is forecast to briefly intensity to 55 knots in the next 12 to 24 hours, but then begin a steady weakening trend as the shear comes to dominate over the outflow and sea surface temperatures begin to drop off.
The system will move into significantly cooler waters around 48 hours, and begin subtropical transition. As the system is enveloped by dry air, moves under a 200mb jet streak and moves into a region of cooler sea surface temperatures, it will complete transition into a strong gale-force subtropical low no later than 72 hours, and likely as early as 60 hours.