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Tropical Storm Hector Discussion Number 5

Wiki-Hurricanes Forecast Center

2:00 PM PDT Wed Aug 1 2018

Hector is dealing with some residual subsident air entrained within its circulation this afternoon, with core convection attempting to fire to siphon off dry air in the northern semicircle. The mid-level eye that was apparent on microwave imagery this morning has degraded since then, and low-resolution AMSU microwave imagery from 1708Z suggests that the internal structure has been somewhat lopsided with a partial eyewall occuring only in the southern semicircle. Infrared imagery shows that the core continues to support cold cloud tops, and a solid attempt at reorganization appears to be in progress, though a subsident area remains within the central dense overcast. UW-CIMSS ADT still shows T3.0/45kt, with SAB and TAFB in agreement in their 18Z estimates of T3.0/45kt. SATCON member consensus yields 48 kt. An ASCAT and OSCAT at 1708Z and 1723Z respectively supported 35 kt as the intensity for Hector, with no immediately evident signs of higher winds. For now, an intensity of 45 kt is maintained for this advisory, which may be a bit aggressive.

There is not much new to say about the future steering for Hector with strong mid-level ridging directing the current westerly track. Some deviations slightly north or south of west are anticipated as the ridge waxes and wanes, but it should remain the dominant steering feature throughout the next five days, suppressing northerly beta drift which would typically occur for an intensifying system. Intensity modeling for Hector has become slightly more complicated this afternoon, and solutions continue to diverge over Hector's intensification potential. Much of the statistical guidance in fact shows slow strengthening throughout the entirety of the next five days, with rates averaging around a very pedestrian 5 kt/day. Much of the disagreement arises from handling of upper-level wind flow associated with an upper-level potential vorticity feature now approaching Hector from the east. SHIPS shows 15 kt or so of shear over supportive albeit lackluster waters over the next day or two, but eventually allow for a Category 1 hurricane to materialize towards the end of the forecast window. Global model guidance has scaled back somewhat but still suggest anything between a tropical storm to a borderline Category 1/2 hurricane. Dynamical models remain aggressive still with their depictions of a major hurricane within four days. Have chosen to scale back the forecast peak intensity slightly, but given rather stable support from ensemble guidance, have chosen to keep the intensity forecast nearly in line with previous advisories.

FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 45 KT 50 MPH

12H 02/0600Z 50 KT 60 MPH

24H 02/1800Z 55 KT 65 MPH

36H 03/0600Z 60 KT 70 MPH

48H 03/1800Z 70 KT 80 MPH

72H 04/1800Z 80 KT 90 MPH

96H 05/1800Z 85 KT 100 MPH

120H 06/1800Z 85 KT 100 MPH