ZCZC HFOTCDCP1 ALL TTAA00 PHFO DDHHMM Hurricane Walaka Discussion Number 16...Corrected NWS Central Pacific Hurricane Center Honolulu HI CP012018 500 AM HST Wed Oct 03 2018 Walaka's eye became much more distinct overnight. In addition, the cloud tops cooled significantly in the eyewall. Note that in the last couple of hours, the northwestern eyewall is beginning to show some signs of becoming more narrow. This may be due to increasing vertical wind shear, as well interaction with an upper-level trough located to the northwest of Walaka. Prior to this, some of the satellite fix agencies showed intensification occurred early this morning. The most recent subjective Dvorak current intensity estimates were 6.5/127 kt from JTWC, 6.0/115 kt from PHFO, and 5.5/102 kt from SAB. The latest UW-CIMSS ADT estimate was 7.0/140 kt. Based on a blend of these estimates, we have increased Walaka's initial intensity to 120 kt for this advisory. Walaka has been accelerating toward the north-northeast overnight, and the initial motion for this advisory is 015/15 kt. The primary steering mechanism is the circulation around a vertically-stacked low pressure area near 32N 170W. Therefore, Walaka is expected to continue accelerating toward the north-northeast into tonight. Once the hurricane gets closer to this extratropical feature, the track guidance indicates its forward motion will slow during the 24 to 48 hour time period. The latest track forecast continues to show a brief bend in the track toward the north-northwest, followed by rapid acceleration toward the northeast between 48 and 96 hours. The track guidance remains in remarkably good agreement considering the rather complex interaction between Walaka and the extratropical low. This latest track forecast is very close to the previous advisory package through 36 hours, except for some minor increase in forward motion. The track was adjusted to the left around 48 hours to more closely follow the consensus guidance, which appears to be in general agreement in regards to the interaction with the low. There was little change in the track from the previous advisory during the 72 to 120 hour time periods. As the vertical wind shear near Walaka becomes increasingly hostile during the next 24 to 36 hours, steady weakening is forecast. Although the shear diminishes somewhat by 36 hours, the tropical cyclone will begin moving over increasingly cool sea surface temperatures and reduced ocean heat content. There is some uncertainty about how Walaka's interaction with the extratropical low will affect its intensity. The global models seem to be in good agreement that some semblance of a warm core system will remain after Walaka interaction with the extratropical low. Therefore, the current forecast maintains Walaka as a tropical cyclone through 72 hours. However, it would not be surprising if the system becomes extratropical sooner. The latest intensity forecast shows a slower rate of weakening than most of the dynamical models. It is in best agreement with the ECMWF and GFS output. The current intensity forecast is showing a somewhat faster weakening trend beyond 36 hours compared with the previous advisory package. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 19.6N 169.4W 120 KT 140 MPH 12H 04/0000Z 22.2N 168.4W 110 KT 125 MPH 24H 04/1200Z 25.9N 167.3W 100 KT 115 MPH 36H 05/0000Z 29.0N 167.4W 85 KT 100 MPH 48H 05/1200Z 30.7N 167.5W 75 KT 85 MPH 72H 06/1200Z 35.0N 163.5W 55 KT 65 MPH 96H 07/1200Z 44.5N 155.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 08/1200Z 53.0N 143.0W 30 KT 35 MPH...POST-TROP/EXTRATROP $$ Forecaster Houston NNNN
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