ZCZC HFOTCDCP1 ALL TTAA00 PHFO DDHHMM Hurricane Walaka Discussion Number 9 NWS Central Pacific Hurricane Center Honolulu HI CP012018 1100 AM HST Mon Oct 01 2018 Hurricane Walaka is an impressive tropical cyclone. A 20 nm wide clear eye is surrounded by a large ring of -70 to -76C cloud tops with excellent upper level outflow in all quadrants. Banding features are also present though not as well-formed as early this morning. Intensity estimates came in at 6.0/115 kt from PHFO and JTWC, and 6.5/127 kt from SAB. ADT was 6.7/132 kt at 1800 UTC. Given the overall appearance and intensification trend, the initial intensity for this advisory leans on the higher end of the estimates at 130 kt. Walaka is moving at 305/9 kt as it rounds the southwestern flank of a subtropical ridge. A developing low pressure system is expected to produce a break in the ridge to the north of the hurricane and cause a turn toward the north on Tuesday. The numerical models are in agreement with the scenario and the track guidance is tightly packed, especially through 72 hours. Walaka is expected to accelerate toward the north under the influence of the low on Wednesday and into Thursday. The forecast track for this advisory is essentially a refresh of the previous forecast and is close to the HCCA consensus, especially through 72 hours. Rapid intensification has been occurring since last night. With sea surface temperatures under Walaka expected to remain near 30C through tonight, high ocean heat content, and low vertical wind shear, there is no reason to believe that peak intensity has been reached. SHIPS forecasts 147 kt from 18 to 24 hours so the forecast calls for a peak intensity of 145 kt tonight before starting a weakening trend. This will put Walaka in Category 5 territory on the Saffir-Simpson scale and exceeds the maximum intensity achieved by Hurricane Ioke in 2006. The forecast track will take Walaka near Johnston Island on Tuesday and the Hurricane Warning remains in effect for this location. The northeastward track after Tuesday is also expected to take the hurricane across the Papahanaumokuakea Marine National Monument between French Frigate Shoals and Laysan Island on Thursday, and a Hurricane Watch may be needed for these locations later today or tonight. FORECAST POSITIONS AND MAX WINDS INIT 01/2100Z 12.9N 169.3W 130 KT 150 MPH 12H 02/0600Z 14.0N 170.1W 140 KT 160 MPH 24H 02/1800Z 15.6N 170.7W 145 KT 165 MPH 36H 03/0600Z 17.7N 170.5W 140 KT 160 MPH 48H 03/1800Z 20.7N 169.5W 125 KT 145 MPH 72H 04/1800Z 27.1N 167.3W 100 KT 115 MPH 96H 05/1800Z 31.0N 167.0W 75 KT 85 MPH 120H 06/1800Z 35.0N 163.0W 65 KT 75 MPH $$ Forecaster Kodama NNNN
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