By PDC’s Senior Weather
Specialist Glenn James
Current Tropical Cyclones:
Tropical Cyclone 11S (Freddy)…is located approximately 748 NM southeast of Diego Garcia
Tropical Cyclone 13S (Dingani)…is located approximately 1187 NM south of Diego Garcia
South Indian Ocean
Tropical Cyclone 11S (Freddy)
According to JTWC Warning number 27, sustained winds were 135 knots, with gusts to 165 knots.
Animated multi-spectral satellite imagery depict a very well organized system with a 13 NM diameter eye. There is evidence of pressure on the eastern periphery as the system is tracking under an area of westward upper-level wind flow estimated at 35-40 knots.
Environmental analysis indicates TC 11S to be in marginally favorable conditions for continual tropical development. These conditions are characterized by the aforementioned outflow aloft, moderate (15-20 knot) vertical wind shear, and warm sea surface temperatures.
TC Freddy continues its westward track as it transits the northern periphery of the ridge to the south. The system will continue this trajectory until approximately 36 hours when it will experience a slight dip west-southwestward due to the supporting ridge migrating to the east.
There is copious amounts of dry air surrounding the system, however, TC Freddy will stay cocooned in its own moisture pocket during its forecast track. TC 11S is forecast to slowly but surely decrease in intensity throughout the forecast period, conversely, the system has undergone three peak intensity events and the possibility of a fourth event should not be ruled out.
Tropical Cyclone 13S (Dingani)
According to JTWC Warning number 13, sustained winds were 50 knots, with gusts to 65 knots.
Animated multi-spectral satellite imagery depicts an exposed low level circulation center (llcc) with fragmented feeder bands wrapping into the core. The system has become decoupled from the main bulk of convection which is now completely displaced poleward.
Environmental analysis reveals TC Dingani is in an unfavorable environment for further tropical development characterized by very little outflow aloft, strong (30-35 knot) vertical wind shear,
and relatively cooler sea surface temperatures.
TC Dingani continues its south-southwestward track as it is now approaching cooler waters. The system will continue this trajectory as it decreases in intensity due to increasing vertical wind shear, continual dry air entrainment, and declining sea surface temperatures.
By 24 hours TC Dingani will begin to fall under the influence of the subtropical jet stream and turn to a southeastward track, all the while continuing to decrease in intensity and completely dissipate by 48 hours.
Northwest Pacific Ocean
>>> There’s an area of disturbed weather being referred to as Invest 99W…which is located approximately 80 NM south of Palau
Animated enhanced infrared satellite imagery and a microwave pass depicts a broad circulation with deep convection in the northwestern semicircle.
Environmental analysis reveals the area to be unfavorable for 99W to develop due to very high (30-40 knot) vertical wind shear and minimal upper level exhaust, offset only by warm sea surface temperatures
Global models are in agreement that 99W will continue on a
north-northwesterly track over the next few days with little intensification.
Maximum sustained surface winds are estimated at 15 to 20 knots.
The potential for transition into a significant tropical cyclone within the next 24 hours is low.
>>> There’s a second area of disturbed weather being referred to as Invest 91P…which is located approximately 105 NM north-northeast of Mornington Island, Australia
Animated enhanced infrared satellite imagery and a microwave
pass depict a weak and elongated low-level circulation (llc) with a
relatively small area of convection in the southeastern portion of the Gulf of Carpentaria…while Mornington Island winds are from the southeast at 14 knots.
Environmental analysis reveals that Invest 91P is in a marginally favorable environment for intensification due low to moderate (15-20 knot) vertical wind shear, moderate poleward outflow aloft, and very warm sea surface temperatures.
Global models generally agree that Invest 91P will track southeastward before recurving southwest, and making landfall over Northern Australia within the next 36 hours.
Maximum sustained surface winds are estimated at 20 to 25 knots.
The potential for transition into a significant tropical cyclone within the next 24 hours is downgraded to low.