Issued at 500 AM HST Mon Jul 19 2021

000
WTPZ42 KNHC 191437
TCDEP2
 
Tropical Storm Guillermo Discussion Number   9
NWS National Hurricane Center Miami FL       EP072021
500 AM HST Mon Jul 19 2021
 
Guillermo's satellite presentation has continued to deteriorate
over the past several hours, although a new, small deep convective
burst has developed just to the southeast of the circulation
center.  An earlier AMSR2 microwave overpass revealed a rather
elongated (west to east) and ill-defined circulation with
fragmented bands in the southeast quadrant.  The initial intensity
is lowered to 35 kt and is based on a blend of the TAFB and SAB
Dvorak satellite intensity estimates.
 
Guillermo is moving over cooler (about 25C) water and into a
progressively more stable and drier surrounding environment.
The statistical-dynamical SHIPS models (GFS/ECMWF) indicate that
moderate west-northwesterly shear should also contribute to the
cyclone's degeneration to a remnant low on Wednesday night.  The 
intensity forecast now shows Guillermo becoming a remnant low 
sooner than the previous advisory and conforms with a consensus of 
the large-scale models and the SHIPS forecasts.
 
The initial motion is estimated to be westward, or 275/13 kt.  A
subtropical ridge anchored to the north of the cyclone should
influence a generally westward motion through dissipation at day 5.
A few of the global models are now showing the lower levels
of the ridge building some to the east-northeast of the Hawaiian
Islands which could induce a west-southwestward motion, or slightly
left of due west, around mid-period.  The NHC forecast is once
again adjusted a bit to the left of the previous one and is based on
the various consensus aids.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  19/1500Z 19.1N 117.8W   35 KT  40 MPH
 12H  20/0000Z 19.0N 119.9W   35 KT  40 MPH
 24H  20/1200Z 18.9N 123.0W   30 KT  35 MPH
 36H  21/0000Z 18.6N 126.1W   30 KT  35 MPH
 48H  21/1200Z 18.3N 128.9W   30 KT  35 MPH
 60H  22/0000Z 18.1N 131.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  22/1200Z 17.9N 134.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  23/1200Z 17.9N 139.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  24/1200Z 17.9N 145.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Roberts
 

Source: Tropical Storm Guillermo Forecast Discussion Number 9