ZCZC HFOTCDCP1 ALL TTAA00 PHFO DDHHMM Tropical Storm Walaka Discussion Number 24 NWS Central Pacific Hurricane Center Honolulu HI CP012018 500 AM HST Fri Oct 05 2018 The satellite appearance of Walaka has deteriorated overnight, with the low level circulation center now becoming exposed. The latest satellite intensity estimates were 3.5 (55 knots) from PHFO, 2.5 (35 knots) from SAB, while the ADT came in at 2.9 (43 knots). A 0755Z ASCAT pass caught a portion of the western edge of the circulation and showed a 43 knot wind barb. Given the data from the ASCAT only sampling the weaker western side of the circulation along with support from the PHFO intensity estimate, the initial intensity of Walaka was lowered to 55 knots for this advisory. The initial motion was set at 010/07 knots. Walaka continues to interact with a deep mid-upper level low in the vicinity of 27/28N 167W. This mid-upper low is forecast to fill today as a broad north Pacific upper trough moves in from the northwest. This should pick Walaka up and accelerate the cyclone off to the northeast through Saturday night, with Walaka expected to undergo the extra-tropical transition late Saturday or Saturday night. The official forecast track is very close to that of the previous advisory and is very close to the TVCE, GFEX, and HCCA consensus guidance. Walaka will be over cool sea surface temperatures below 25C throughout the duration of its journey across the north Pacific, with vertical wind shear expected to increase substantially tonight and Saturday. Although conditions will become increasingly hostile, the transition over to an extra-tropical low will likely keep the intensity from dropping off too much during the next couple of days. As a result, the official intensity forecast calls for slow and steady weakening and closely follows a blend of the dynamical guidance. Walaka is expected to become an extra-tropical low late Saturday or Saturday night, with dissipation by forecast hour 72. FORECAST POSITIONS AND MAX WINDS INIT 05/1500Z 31.5N 168.3W 55 KT 65 MPH 12H 06/0000Z 32.8N 167.2W 50 KT 60 MPH 24H 06/1200Z 36.2N 164.5W 50 KT 60 MPH 36H 07/0000Z 42.2N 160.0W 45 KT 50 MPH 48H 07/1200Z 49.1N 153.6W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 08/1200Z...DISSIPATED $$ Forecaster Jelsema NNNN
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