ZCZC HFOTCDCP1 ALL TTAA00 PHFO DDHHMM Tropical Storm Walaka Discussion Number 26 NWS Central Pacific Hurricane Center Honolulu HI CP012018 500 PM HST Fri Oct 05 2018 Walaka's satellite presentation has changed little since this morning, with an exposed low level circulation center (LLCC) embedded within low cloud swirls and occasionally open to the west. Cooler-topped layered clouds, along with a single sputtering cumulonimbus, mark the southeast flank. A 2120Z ASCAT pass showed two small patches of 45 kt winds beneath the layered clouds, while the entire western semicircle had winds of 30 kt or less. Latest Dvorak current intensity estimates range from 1.5/25 kt from JTWC to 2.5/35 kt from PHFO. SAB considered this system too weak to classify while ADT from UW-CIMSS was 43 kt. Using a mix of these estimates and an assumption of continued weakening from this morning's ASCAT pass, we will assign an initial intensity of 40 kt for this advisory. This weakening system is tracking northeastward, with initial motion of 040/12 kt. After moving northward over the past few days along the western fringe of the subtropical ridge, Walaka has begun to respond to southwesterly steering ahead of a broad north Pacific upper trough moving in from the northwest. This will pick Walaka up and accelerate it off to the northeast through Sunday. Walaka is expected to begin extra-tropical transition Saturday. The official forecast track lies along the right side of the very tight guidance envelope, following an arc just to the left of CTCI. This track, adjusted slightly to the right to account for initial motion, terminates at 48 hours as Walaka becomes absorbed by a mid-latitude low. Walaka will move over increasingly cooler water along its truncated track, while vertical wind shear dramatically ramps up, reaching 36 kt at 36 hours and 52 kt by 48 hours. Global models show Walaka will be absorbed by a mid-latitude low by 48 hours, with weakening and extratropical transition occurring simultaneously from 24 hours through system dissipation at 48 hours. Our forecast follows the previous curve, closely tracing ICON. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 32.9N 166.6W 40 KT 45 MPH 12H 06/1200Z 35.4N 164.1W 35 KT 40 MPH 24H 07/0000Z 40.9N 159.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 36H 07/1200Z 46.9N 154.4W 25 KT 30 MPH...POST-TROP/EXTRATROP 48H 08/0000Z...DISSIPATED $$ Forecaster Powell NNNN
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Page last modified: Monday, 13-May-2019 15:53:17 UTC