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Tropical Cyclone Narelle (08S) Current Intensity 75 Knots

15.5S 119.7E

January 10th, 2013 Category: Tropical Storms

Tropical Storm 08S – January 8th, 2013

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Track of Tropical Storm 08S - January 9th, 2013 © Univ. of Wisconsin

Track of TS 08S

Tropical Cyclone Narelle (08S) located approximately 500 nm north-northeast of Learmonth, Australia, has tracked south- southwestward at 06 knots over the past six hours. Maximum significant wave height is 28 feet.

The current intensity of 75 knots is based on a consensus of Dvorak satellite intensity estimates from the same reporting agencies. Recent animated infrared satellite imagery shows deep convection flaring over a well-defined low-level circulation center (LLCC), particularly along the northwestern quadrant.

The system is tracking south-southwestward along the northwestern periphery of a subtropical ridge that extends across central Australia. This ridge is expected to remain the dominant steering mechanism throughout much of the forecast period. As the system tracks closer to the ridge axis over the next 12 to 24 hours, it is expected to track a bit further westward before making a poleward turn after TAU 48.

Passage over very warm water, low vertical wind shear, and strong outflow aloft will allow the system to intensify significantly over the next 48 hours. After TAU 72, passage over cooler water and entrainment of drier and cooler air during the extended forecast period will result in steady weakening.

The dynamic models are in good general agreement through TAU 36, but continue to diverge beyond that point. NOGAPS and the UKMET model show a steady turn around the ridge axis and track the system inland as it undergoes extra-tropical transition in the extended period. GFS and GFDN depict a nearly straight poleward track with steady weakening and extra-tropical transition of a remnant low after TAU 120. The ECMWF model, which has been very consistent over the past several runs, shows the system tracking more slowly and farther westward than the other models, with a rapidly dissipating circulation following the lower level flow.

The current forecast is consistent with the GFS and GFDN scenarios, given expectations that the cyclone will remain very strong through TAU 96. However, if the system dissipates more quickly during the extended period than currently forecast, TC 08S may follow a slower and more westward track similar to the ECMWF forecast. Due to the continued spread in dynamic guidance after TAU 48, there is low confidence in the JTWC forecast track.

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