ZCZC HFOTCDCP3 ALL TTAA00 PHFO DDHHMM Hurricane Miriam Discussion Number 17 NWS Central Pacific Hurricane Center Honolulu HI EP152018 1100 PM HST Wed Aug 29 2018 The satellite presentation of Miriam has improved slightly since the previous advisory, with deep convection remaining over the difficult to locate low level circulation center. The latest subjective Dvorak intensity estimates from PHFO, SAB and JTWC ranged from 4.0 (65 knots) to 4.5 (77 knots) while the Advanced Dvorak Technique from UW-CIMSS came in at 3.5 (55 knots). Since the satellite presentation has improved slightly since the previous advisory, the initial intensity will be increased to 70 knots with this advisory, which correlates well with a blend of the intensity estimates. The initial motion is set at 300/07 knots. Miriam is being steered by a large subtropical ridge to the northeast of the system and a deep mid-upper level trough to the north-northwest. Miriam is expected to track off to the northwest tonight then make a turn toward the north Thursday through Friday night. The increasing west-southwesterly shear should result in a decoupling of the system by early Saturday, and this is expected to result in a turn toward the northwest and eventually west Saturday through Monday as Miriam becomes influenced primarily by the low level trade wind flow. The official forecast for this advisory is nearly identical to the previous advisory and closely follows the consensus guidance. The environment will be conducive for additional intensification of Miriam over the next 24 hours, with shear values remaining low, sea surface temperatures holding around 28C, while the system moves over a region of higher Ocean Heat Content. As a result the official forecast calls for slight intensification over the next 24 hours, followed by slow and steady weakening between 24 and 36 hours as Miriam begins to feel the effects of strengthening west- southwesterly shear. Beyond 36 hours the intensity forecast will show fairly rapid weakening as shear values increase into the 30 to 45 knot range, while the system moves over marginal sea surface temperatures of 26C or below. FORECAST POSITIONS AND MAX WINDS INIT 30/0900Z 14.7N 141.1W 70 KT 80 MPH 12H 30/1800Z 15.4N 141.6W 75 KT 85 MPH 24H 31/0600Z 16.8N 141.6W 80 KT 90 MPH 36H 31/1800Z 18.4N 141.5W 70 KT 80 MPH 48H 01/0600Z 19.9N 141.9W 55 KT 65 MPH 72H 02/0600Z 23.0N 144.0W 40 KT 45 MPH 96H 03/0600Z 25.5N 147.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 04/0600Z 27.0N 152.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Jelsema NNNN
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