By PDC’s Senior Weather
Specialist Glenn James
Current Tropical Cyclones:
Tropical Cyclone 17S (Herman)…is located approximately 441 NM west-northwest of Learmonth, Australia
South Indian Ocean
Tropical Cyclone 17S (Herman)
According to JTWC Warning number 16, sustained winds were 65 knots, with gusts to 80 knots.
Animated enhanced infrared satellite imagery depicts a partially exposed low-level circulation center (llcc), with deep convection sheared over the western quadrant of the llcc. Another image reveals an area of deep convection over the eastern semicircle.
Environmental conditions are marginally unfavorable with moderate (15-20 knot) vertical wind shear, moderate eastward outflow, relatively cool sea surface temperatures and dry air entrainment.
Over the past six hours, TC 17S has been tracking south-southwestward on the western periphery of a ridge positioned to the east with a deep mid-latitude trough positioned to the south-southwest. the system is forecast to gradually turn toward the west-southwest briefly before turning sharply west-northwestward after 24 hours.
After 24 hours, the mid-latitude trough will track eastward and a strong low to mid level ridge is expected to become the dominate steering feature to the south, which will steer the system west-northwestward through the forecast period.
TC 17S should rapidly weaken over the next 24 hours, as environmental conditions degrade steadily with significant dry air entrainment, increasing vertical wind shear and marginally-favorable sea surface temperatures values. TC 17S will, therefore…dissipate by 72 hours.