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Tropical Storm Hector Discussion Number 6

Wiki-Hurricanes Forecast Center

8:00 PM PDT Wed Aug 1 2018

Hector has become better organized this evening. An eye-like feature was evident on geostationary imagery around 22z, but since that time the cloud pattern has transitioned to a compact central dense overcast, with tops cooler than -80C. A blend of satellite intensity estimates supports an intensity of 45kt; however, given the increased organization since the previous advisory, the initial strength has instead been set to 50kt.

Water vapor imagery shows upper-level outflow invading from the northeast. and this is likely the start of a period of increased wind shear that has been discussed in previous advisories. While these upper-level winds on the order of 15kt are unlikely to kill Hector, they should at the least arrest development tomorrow. In fact, both the GFS and HWRF show pressure increases of 6mb and 15mb, respectively, so some weakening would not be surprising. By late Friday, wind shear is expected to become light throughout the entire atmospheric column; in conjunction with warm ocean temperatures and a moist environment, Hector should intensify. There continues to be a discrepancy in modelling, with the ECMWF keeping the storm below hurricane strength through five days. The SHIPS and HWRF continue to make Hector a strong Category 1 hurricane, while the GFS and especially HWRF/HMON are more bullish. Upper-air maps from the ECMWF appear to show an unrealistic amount of wind shear through the period, and so its depiction of a weaker storm has generally been discounted. The SHIPS/LGEM models appear to be underselling intensification as a result of parameters not related to the environment. All considered, the updated forecast is slightly lower than the previous one through 24 hours, but increased slightly on days four and five. This may be conservative if the HWRF/HMON forecasts come to fruition.

Hector turned toward the west earlier today, a sign that the mid-level trough southwest of California is losing influence. As subtropical ridging builds north of the storm, it should continue on the westward path or even lose latitude after 48 hours. On its current course, Hector should enter the Central Pacific by day five.

FORECAST POSITIONS AND MAX WINDS

INIT 02/0300Z 50 KT 50 MPH

12H 02/1200Z 50 KT 60 MPH

24H 03/0000Z 50 KT 60 MPH

36H 03/1200Z 65 KT 75 MPH

48H 04/0000Z 75 KT 85 MPH

72H 05/0000Z 85 KT 100 MPH

96H 06/0000Z 95 KT 110 MPH

120H 07/0000Z 95 KT 110 MPH