Tropical Storm Seven-E Discussion Number 4
Wiki-Hurricanes Forecast Center
10:00 PM CDT Sat Jun 30 2018
High-resolution visible satellite imagery from before the sun set indicated that the low-level circulation of Seven-E remains somewhat elongated northwest to southeast. However, the overall cloud pattern has continued to improve, with more central convection and the development of a new spiral band to the south. The upper-level environment also continues to improve, with expanding outflow especially to the northeast. The initial intensity has been left at a potentially conservative 35kt in the absence of scatterometer data and an unchanged satellite estimate of T2.0/30kt from SAB.
The track forecast remains of high confidence. Seven-E is being steered west-northwest by expansive mid-level ridging to its north, and an overwhelming majority of models are in excellent agreement that this motion should continue through day 5. The one exception is the UKMET, which forecasts a substantially more southern track; however, it is known to over-amplify ridging and has not been given much consideration for now.
The environment the system finds itself in is excellent. Upper-level winds have decreased below 10kt as anticyclonic flow becomes established aloft, and little change in wind shear is expected for the next five days. Ocean temperatures are expected to remain above 28°C for at least the next 48 hours, ultimately decreasing below 26°C after 96 hours. Mid-level relative humidity values are expected to remain near or above 60 percent for the next 72 hours. The combination of these factors yields high confidence in significant strengthening over the next 4 days, especially once the Seven-E develops an inner core, and the system is expected to reach hurricane strength in about 36 hours. Intensity models are in reasonably good agreement, with the HMON, GFS, and SHIPS making the system a Category 4 hurricane at peak. The LGEM is just shy of that intensity, while the HWRF indicates a strong Category 2 hurricane. The intensity forecast has been adjusted upward in the first 72 hours since the previous discussion. Weakening is expected to begin on days 4 and 5.
FORECAST POSITIONS AND MAX WINDS
INIT 01/0300Z 35 KT 40 MPH
12H 01/1200Z 45 KT 50 MPH
24H 02/0000Z 55 KT 65 MPH
36H 02/1200Z 70 KT 80 MPH
48H 03/0000Z 90 KT 105 MPH
72H 04/0000Z 110 KT 125 MPH
96H 05/0000Z 95 KT 110 MPH
120H 06/0000Z 60 KT 70 MPH