By PDC’s Senior Weather
Specialist Glenn James
Current Tropical Cyclones:
Tropical Cyclone 05S (Darian)…is located approximately 1304 NM west-northwest of Learmonth, Australia
Northwest and Southwest Pacific Ocean, North and South Indian Oceans, and Arabian Sea:
South Indian Ocean
Tropical Cyclone 05S (Darian)
According to JTWC Warning number 5, sustained winds were 75 knots, with gusts to 90 knots.
Animated infrared imagery shows tops warming slightly and some erosion of the moisture fields over the southeast quadrant. Overall however, the system remains well organized and vigorous. A microwave series verifies a robust storm with a symmetrical microwave eye with deep convection extending from the southern portion of the eyewall up into the northwestern quadrant. The due southward movement also confirms that the system is leaving the influence of the near equatorial ridge and beginning the arc into a lazy turn to the west as it comes under the influence of the subtropical ridge.
TC Darian is tracking through a favorable environment characterized by well developed poleward outflow and low vertical wind shear. Sea surface temperature and ocean heat content are decent but nothing special, hence the expectation that Darian will not intensify much further. The environment along the expected track is expected to remain steady through the next 4-days.
Tropical cyclone 05S will cruise along at a steady state in a remarkably consistent environment for the next 96 hours. Vertical wind shear remains below 15 knots and will not be a factor. The storm is leaving the influence of the near equatorial ridge and will drift poleward until it begins to feel a push from the subtropical ridge. It will gradually bend to a westward track along the 14th latitude by December 20th morning.
There is a brief window for mild intensification due to one degree warmer sea surface temperatures beginning near 72 hours. Dry air entrainment will provide an additional nuance to the intensity trend. Mid-level moisture progs show dry air wrapping over the top side of the system and completely cutting off the core from the surrounding environment during the next 48 hours, but they also indicate that the core will be able to maintain its integrity and never quite be eroded by the dry air.
Long range models are consistent in showing a poleward bend after 96 hours but the ambiguity in the track forecast increases sharply as the system nears the 15th latitude ( 96-120 hours).