Hurricane John Discussion Number 11

Wiki-Hurricanes Forecast Center

2:00 AM PDT Wed Aug 8 2018

John is weakening quite quickly this morning. After passing Socorro Island, the eye became less defined and even dissipated in recent images before temporarily clearing now. Dry air that wrapped around the central dense overcast of the hurricane has eroded most convection north of the center. Recent satellite intensity estimates were T4.0/65kt from SAB and T4.9/87.4kt from UW-CIMSS ADT. It is worth noting that ADT's weakening is tampered by constraints, with raw values near minimal tropical storm strength. Assuming John's winds haven't completely collapsed, the initial intensity is lowered to 85kt, but this may be generous.

Despite modest wind shear and warm ocean temperatures, the massive circulation of John is pulling in continuous streams of environmental dry air, preventing the hurricane from developing sturdy deep convection in its eyewall and a solid inner core. This is unlikely to change for the foreseeable future, and although upper-level winds will remain light over the next 5 days, ocean temperatures are expected to fall below 26C within 24 hours while the environment becomes even drier. Therefore, John is expected to weaken from here on out, and the rate of weakening has been accelerated given this morning's trends. Degeneration is now expected within 72 hours.

John continues to move towards the northwest in response to a nearby weakness in the ridge over the Baja California, and not much has changed with the track forecast. Models are in good agreement on an eventual westerly curve as the weakness withers off towards the end of the forecast and John becomes a shallower cyclone.


INIT 08/0900Z 85 KT 100 MPH

12H 08/1800Z 75 KT 85 MPH

24H 09/0600Z 60 KT 70 MPH

36H 09/1800Z 50 KT 60 MPH

48H 10/0600Z 40 KT 45 MPH

72H 11/0600Z 30 KT 35 MPH...POST-TROP/REMNT LOW

96H 12/0600Z 25 KT 30 MPH...POST-TROP/REMNT LOW

120H 13/0600Z 20 KT 25 MPH...POST-TROP/REMNT LOW

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