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Tropical Storm Hector Discussion Number   7
NWS National Hurricane Center Miami FL       EP102018
200 AM PDT Thu Aug 02 2018

Hector's satellite presentation has quickly improved over the past
few hours. Recent microwave and scatterometer data indicate that
the low-level center is now well embedded within the expanding
convective canopy, and a tiny mid-level eye has formed. In fact, a
late-arriving WindSat pass from around 0230 UTC showed that Hector
had a mid-level structure that has been associated with rapidly
intensifying tropical cyclones, when present in low-shear
environments. The initial intensity has been raised to 60 kt based
on a timely ASCAT-B overpass around 0556 UTC.  Although the maximum
winds measured by the ASCAT were only around 55 kt, at least some
undersampling seems likely given the small size of the inner-core of
the cyclone.

The northeasterly shear that has been affecting Hector does not
appear to be significantly affecting the inner-core of the cyclone
at this time. However, it is uncertain whether this is only a
short-term trend, or if the inner core will remain protected from
the higher shear going forward.  While the GFS and ECMWF indicate
that the shear should decrease through today, the HWRF and HMON
models forecast that Hector will become strongly sheared by tomorrow
and temporarily weaken as a result. The small size of the tropical
cyclone further complicates the intensity forecast since small
cyclones can quickly intensify or weaken, especially in moderate
shear environments, and these short-term fluctuations are very
difficult to predict. As a course of least regret, the NHC forecast
does not show significant strengthening or weakening for the first
48 h of the forecast and instead shows steady strengthening,
similar to the DSHP and LGEM models, and is higher than the previous
advisory.  For days 3-5, there is a better consensus among the
models that Hector will strengthen, and the official forecast is
still close to the multi-model consensus and the previous forecast.

The initial motion estimate is now 285/10 kt.  There is more
confidence in the track forecast.  A strong subtropical ridge
extending from the eastern Pacific into the central Pacific should
keep Hector on a general west heading through the entire forecast
period.  The main source of uncertainty is still the speed of the
tropical cyclone at days 3-5.  Since the main difference between the
models appears to be subtle differences in the strength of the
ridge, the NHC forecast is still based on the multi-model consensus
and little change has been made from the previous advisory.


FORECAST POSITIONS AND MAX WINDS

INIT  02/0900Z 14.3N 123.4W   60 KT  70 MPH
 12H  02/1800Z 14.5N 125.1W   65 KT  75 MPH
 24H  03/0600Z 14.6N 127.4W   70 KT  80 MPH
 36H  03/1800Z 14.5N 129.7W   75 KT  85 MPH
 48H  04/0600Z 14.4N 132.0W   80 KT  90 MPH
 72H  05/0600Z 14.0N 136.6W   85 KT 100 MPH
 96H  06/0600Z 14.0N 141.5W   95 KT 110 MPH
120H  07/0600Z 14.5N 146.5W   95 KT 110 MPH

$$
Forecaster Zelinsky

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