350 WTPZ45 KNHC 121448 TCDEP5 Hurricane Darby Discussion Number 13 NWS National Hurricane Center Miami FL EP052022 500 AM HST Tue Jul 12 2022 While Darby remains an impressively compact hurricane, there has been a bit of erosion in the inner-core convective structure this morning. The eye in particular has become less distinct and has cooled relative to yesterday afternoon, though the eyewall convection remains strong and quite circular. While an AMSR2 microwave pass at 1042 UTC still showed a closed eyewall, the convection on the northwestern side has eroded some compared to yesterday. Darby remains a very small tropical cyclone, with overnight scatterometer wind data indicating tropical-storm-force winds extend out to 40 n mi to the northeast of the center. While the latest TAFB/SAB Dvorak classifications were a consensus CI 6.0/115 kt, the objective ADT and SATCON data is quite a bit lower. The initial intensity on this advisory is set at 110 kt, blending the guidance, but favoring the somewhat higher subjective Dvorak estimates. While the current vertical wind shear (VWS) over Darby remains very low, sea-surface temperatures underneath the hurricane are gradually decreasing, now currently just under 27 C. It seems likely that Darby is now post-peak intensity and should begin to gradually weaken in the short-term under the less favorable thermodynamic environment. After 24 hours, a combination of an increasingly stable and dry airmass, plus an increase in southwesterly VWS from a broad upper-level trough to the northwest of Darby, is expected to lead to a more rapid weakening trend later this week. The latest NHC intensity forecast is still on the high side of the guidance envelope early on, but then shows a faster rate of weakening as the small cyclone encounters a more hostile environment. Darby is still expected to become post-tropical by 96 hours as deep convection is completely removed from the center and dissipates as suggested by the GFS and ECMWF models at that period. Darby continues to move on a due westward heading at 270/14 kt. There is not much new to report with the track philosophy, as a mid-level ridge currently north of Darby will be eroded some by the aforementioned upper-level trough. This should result in a bit more west-northwest bend in Darby's track between 24-60 hours. After that period, Darby is expected to become an increasingly shallow vortex, and its track should turn back westward following the trade-wind flow around a large low-level subtropical ridge poleward of Hawaii. The latest track forecast is little changed from the prior advisory, and remains close to the tightly clustered consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 12/1500Z 14.7N 129.7W 110 KT 125 MPH 12H 13/0000Z 14.8N 131.7W 105 KT 120 MPH 24H 13/1200Z 15.2N 134.4W 100 KT 115 MPH 36H 14/0000Z 15.8N 137.0W 85 KT 100 MPH 48H 14/1200Z 16.4N 139.5W 75 KT 85 MPH 60H 15/0000Z 16.9N 142.0W 60 KT 70 MPH 72H 15/1200Z 17.2N 144.6W 45 KT 50 MPH 96H 16/1200Z 17.1N 150.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 17/1200Z...DISSIPATED $$ Forecaster Papin