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Tropical Storm  Seven-E Discussion Number 3

Wiki-Hurricanes Forecast Center

2:00 PM PDT Sat Jun 30 2018

Seven-E is developing a curved band structure this afternoon, with an area of centralized convection to the center's west and a dominant band north of the center. The curved band is detailed quite impressively in the the GMI microwave pass from 1716Z and shows more structural organization developing at the center. SAB and TAFB have both assessed T2.0/30 kt with Seven-E. However, a ScatSat pass at 1519Z suggested a swath of non-flagged 35 kt winds in the area of convection north of the center of circulation. On this basis, Seven-E has been upgraded to a 35 kt tropical storm.

Seven-E is on a fairly straight beeline trajectory towards the west-northwest, steered by a large subtropical ridge located south of Louisiana that will be building with heights across the United States during the next five days. Seven-E will be carried west-northwest with ridging over the southwestern United States, perhaps bending right of track as it rounds the western periphery of this continental ridging later around day 4-5.

Although the system is coming together gradually, the system's potentially problematic broad nature may be presenting a bit of an inhibition as the northern curved band is robbing some energy away from convection that could be developing of the center. Still, environmental conditions are favorable for development, and Seven-E has a high ceiling given these factors. Shear, sea surface temperatures, and humidity values are all very positive for intensification out to 60 hours, with slightly favorable conditions continuing to about 96 hours after which Seven-E should enter the stable subtropical latitudes. Models all show steady intensification this period, with the storm peaking to varying degrees -- the system's broad nature should keep the odds of a major rapid intensification event slightly subdued. SHIPS statistical guidance shows a 100 kt peak with LGEM depicting a similar 95 kt peak. Dynamical hurricane intensity guidance is in some disagreement with HWRF showing a Category 1 hurricane and HMON having a major hurricane. Global guidance shows a mix of solutions between Category 1 and Category 3 intensity. Much will be dependent on how well Seven-E addresses its core configuration over the next few days. For now, the forecast philosophy from the last advisory remains generally the same, with strengthening to day 4 before weakening commences at day 5.


FORECAST POSITIONS AND MAX WINDS

INIT 30/2100Z 35 KT 40 MPH

12H 01/0600Z 40 KT 45 MPH

24H 01/1800Z 45 KT 50 MPH

36H 02/0600Z 55 KT 65 MPH

48H 02/1800Z 70 KT 80 MPH

72H 03/1800Z 100 KT 115 MPH

96H 04/1800Z 100 KT 115 MPH

120H 05/1800Z 85 KT 100 MPH