ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM Hurricane Calvin Discussion Number 15 NWS National Hurricane Center Miami FL EP032023 1100 PM HST Fri Jul 14 2023 This evening's satellite and microwave presentation reveals a significantly degraded cloud pattern. A recent SSMI/S image indicated inner core erosion in the southeast quadrant and no apparent outer ring development. Calvin's eye has become obscured and has cooled (-27C), and the GFS model sounding indicated that there could be some southeasterly shear undercutting the upper-level diffluent flow. The subjective intensity estimates from both TAFB and SAB yield 90 kt, the UW-CMISS objective ADT and AiDT intensity estimates are 87 and 88 kt, respectively. Additionally, a RADARSAT (RCM 2) SAR overpass estimated maximum sustained winds of 88-93 kt. Based on these data, the initial intensity is lowered to 90 kt for this advisory. Even though minor intensity fluctuations are possible in the short term, Calvin should continue to spin down as the cyclone traverses cooler waters Saturday while moving into a more stable drier air mass. The statistical-dynamical SHIPS models agree that increasing southwesterly vertical shear should also be an inhibiting factor by 96 hours. Global model simulated infrared satellite imagery continues to show Calvin losing its organized convection early next week and the NHC forecast calls for the cyclone to degenerate to a post-tropical remnant low by day 5, if not sooner. The intensity forecast indicates a faster rate of weakening through day 3 than the previous forecast, and closely follows the HCCA, IVCN, and LGEM intensity models, and is just below the Decay SHIPS. The initial motion is estimated to be west-northwestward, or 285/14 kt. There is no change to the forecast philosophy. The hurricane is expected to move within the deep east-southeasterly steering flow produced by a subtropical ridge stretching across the eastern Pacific through the period. There continues to be quite a bit of uncertainty, with Calvin either passing near or over the Hawaiian Islands. The global models have been trending poleward, either over or just to the north of the Big Island while along-track inconsistencies remain. The most reasonable forecast approach is to hedge toward the best performing consensus aids HCCA and TVCE, and the official track forecast is based on this reliable method. Calvin is still expected to cross 140W and move into the central Pacific basin by early Monday morning, then approach the Hawaiian Islands on Tuesday and Wednesday. Calvin's wind radii have been adjusted based on a RADARSAT (RCM 2) 15Jul 0245 UTC overpass. KEY MESSAGES: 1. Calvin is forecast to move across the central Pacific Ocean and approach the Hawaiian Islands early next week. It is too early to determine the exact location and magnitude of potential impacts given uncertainties in the track, intensity, and structure of Calvin as it approaches the islands. Interests in Hawaii should closely monitor the latest forecast updates. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 14.5N 127.5W 90 KT 105 MPH 12H 15/1800Z 15.0N 129.7W 80 KT 90 MPH 24H 16/0600Z 15.7N 132.6W 70 KT 80 MPH 36H 16/1800Z 16.4N 135.5W 60 KT 70 MPH 48H 17/0600Z 17.0N 138.6W 55 KT 65 MPH 60H 17/1800Z 17.5N 142.0W 45 KT 50 MPH 72H 18/0600Z 18.1N 145.5W 40 KT 45 MPH 96H 19/0600Z 19.1N 152.7W 35 KT 40 MPH 120H 20/0600Z 20.5N 159.6W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Roberts NNNN