Tropical Storm John Discussion Number 17
Wiki-Hurricanes Forecast Center
2:00 PM PDT Thu Aug 9 2018
John continues to spin down over cold water, though not at a rapid rate. The system continues to maintain a small ball of convection over the center of its sprawling low-level circulation, and this convection is well organized with numerous spiral bands. Satellite intensity estimates were T2.5/35kt from SAB and T3.5/55kt from TAFB, with T2.8/41kt from UW-CIMSS ADT. A blend of these data support 45kt, but the initial intensity has been more generously set to 50kt given a gradual weakening.
Water temperatures have fallen to 24C and will continue to cool over coming days, and mid-level relative humidity values will decrease alongside them. So, even though wind shear remains low, weakening is expected and John should become a remnant low in about 2 days before dissipating around day 5. The system is moving west-northwest thanks to a mid-level ridge to its north and east, and this motion should continue for the next 96 hours. By day 5, a collapse in the steering regime should cause John to meander, or perhaps drift toward the northeast.
MAXIMUM WINDS FORECAST
INIT 09/2100Z 50 KT 60 MPH
12H 10/0600Z 45 KT 50 MPH
24H 10/1800Z 40 KT 45 MPH
36H 11/0600Z 35 KT 40 MPH
48H 11/1800Z 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 12/1800Z 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 13/1800Z 20 KT 25 MPH...POST-TROP/REMNT LOW