Tropical Storm Hector Discussion Number 3

Wiki-Hurricanes Forecast Center

2:00 AM PDT Wed Aug 1 2018

Hector is steady state this morning, with the center embedded within a rather misshapen mass of deep convection. Outflow is excellent to the west, but restricted to the east thanks to about 15kt of easterly mid- to upper-level shear; this is likely injecting some dry air and aiding in the disorganization of Hector's cloud pattern at the current time. Satellite intensity estimates are largely unchanged, and ASCAT unsurprisingly missed, so the initial intensity is held at a potentially generous 40kt.

The system continues to move swiftly west-northwest. A stout subtropical ridge exists over the open Pacific to the north of Hector, but a sharp mid-level trough to the southwest of California is allowing the cyclone to gain a little bit of latitude in the short term. By 36 hours, however, this low is expected to become less prominent, allowing the ridge to become the dominant steering feature for the remainder of the period. In fact, the 594dm area of high pressure may be strong enough to promote a west-southwest track around days two to three. Hector should approach the Central Pacific around day five.

Confidence in the intensity forecast has increased since Hector was initiated, although there are still wrinkles to work out. The mid-level shear plaguing the storm should abate over the next 24 to 36 hours, providing a low shear environment throughout the entire atmospheric column. Water temperatures are expected to remain near or above 27C for the five-day period, and mid-level relative humidity values should hover around 60 percent. These factors should favor gradual to steady strengthening, and such a scenario is reflected in modelling. The HWRF, GFS, and 12z ECMWF all make Hector a major hurricane within 120 hours, while the 0z ECMWF and GFS parallel are more conservative with a strong Category 1 hurricane. Given the current structure, the updated forecast continues to show only a gradual rate of strengthening over the next 36 hours, although it is possible this could be conservative if the hurricane models are accurate. Thereafter, owing to expectations of an ideal environment, the forecast has been adjusted upward a little above model consensus, bringing Hector to 90kt by day 5.


INIT 01/0900Z 40 KT 45 MPH

12H 01/1800Z 45 KT 50 MPH

24H 02/0600Z 50 KT 60 MPH

36H 02/1800Z 55 KT 65 MPH

48H 03/0600Z 65 KT 75 MPH

72H 04/0600Z 75 KT 85 MPH

96H 05/0600Z 85 KT 100 MPH

120H 06/0600Z 90 KT 105 MPH

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