Official Discussion issued by the National Hurricane Center

Gonzalo (AL072020) DATA RELEASED: 7/22/2020 9:00:00 PM UTC

Copy of official data

Tropical Storm Gonzalo Discussion Number   5
NWS National Hurricane Center Miami FL       AL072020
500 PM AST Wed Jul 22 2020

Satellite imagery suggests that Gonzalo's intensification has 
paused since the last advisory.  The cyclone continues to show a 
central dense overcast, and microwave imagery indicates a small 
convective ring present under the overcast.  However, the CDO has 
become a bit ragged, and the other banding seen earlier has 
dissipated.  Subjective and objective satellite intensity estimates 
are in the 45-55 kt range, the the initial intensity remains a 
possibly conservative 45 kt.

The initial motion is now 270/12.  There is no change to the 
track forecast philosophy.  Gonzalo is on the south side of a low- 
to mid-level subtropical ridge, and this feature should steer the 
storm generally westward at a faster forward speed for the next 60 
h or so.  After that time, a motion toward the west-northwest is 
expected.  The new NHC forecast track is again little changed from 
the previous track, and it lies very close to the consensus models.

The intensity forecast remains very problematic and of low
confidence. On one side, the cyclone structure, light shear 
environment,and warm sea surface temperatures suggest strengthening,
possibly even rapidly, should occur.  In addition, the SHIPS-based 
guidance and the HWRF still make the system a hurricane.  On the 
other side, the GFS, UKMET, and ECMWF models continue to forecast 
the system to weaken to an open wave by 120 h, possibly due to dry 
air entrainment and large-scale subsidence, and microwave imagery 
suggests that a tongue of drier air is present west and southwest 
of the cyclone.  The NHC intensity forecast again compromises 
between these extremes, showing Gonzalo peaking as a hurricane in 
36-48 h, followed by weakening in deference to the GFS/UKMET/ECMWF. 
The new intensity forecast is unchanged from the previous forecast. 
As noted before, the small size of this system makes it 
susceptible to significant fluctuations in intensity, both upward 
and downward.

Interests in the Windward Islands should monitor the progress of 
this system, as watches could be issued sometime on Thursday.


Key Messages

1. Gonzalo is expected to move near or over the southern Windward
Islands this weekend, and could bring direct impacts from winds and
heavy rainfall. While it is too soon to determine the magnitude and
timing of those impacts, interests in the southern Windward Islands
should monitor the progress of Gonzalo.


FORECAST POSITIONS AND MAX WINDS

INIT  22/2100Z  9.9N  45.0W   45 KT  50 MPH
12H  23/0600Z 10.0N  46.8W   55 KT  65 MPH
24H  23/1800Z 10.1N  49.2W   65 KT  75 MPH
36H  24/0600Z 10.3N  51.8W   70 KT  80 MPH
48H  24/1800Z 10.8N  54.6W   70 KT  80 MPH
60H  25/0600Z 11.3N  57.6W   65 KT  75 MPH
72H  25/1800Z 12.1N  60.8W   60 KT  70 MPH
96H  26/1800Z 14.0N  67.5W   50 KT  60 MPH
120H  27/1800Z 15.0N  72.5W   40 KT  45 MPH

$$
Forecaster Beven