Official Discussion issued by the National Hurricane Center

Gonzalo (AL072020) DATA RELEASED: 7/24/2020 9:00:00 AM UTC

Copy of official data

Tropical Storm Gonzalo Discussion Number  11
NWS National Hurricane Center Miami FL       AL072020
500 AM AST Fri Jul 24 2020

Conventional satellite imagery indicates that Gonzalo's cloud
pattern has changed little during the past several hours.  The
cyclone continues to produce an area of deep convection, although 
quite shapeless, with very cold cloud tops.  A compromise of the
subjective T-numbers from TAFB and SAB along with an earlier SATCON
estimate of 55 kt yields an initial intensity of 50 kt for this
advisory.  An Air Force Reserve reconnaissance aircraft scheduled to
investigate the storm later this afternoon will provide a more
precise intensity estimate.

The statistical-dynamical intensity guidance as well as the 
deterministic models all show Gonzalo strengthening as it 
approaches the southern Windward Islands. The HWRF, Decay 
SHIPS and the LGEM are the only guidance indicating a 
hurricane around the 36 hour period.  Afterward, Gonzalo is 
forecast to move into a more inhibiting thermodynamic
environment over the weekend.  Accordingly, the intensity forecast
calls for weakening on Sunday as Gonzalo enters the eastern
Caribbean sea and dissipation in 96 hours, or sooner as a couple of
the large-scale models suggest.  The intensity forecast is
basically an update of the previous advisory through 36 hours, 
indicating a hurricane approaching and moving over the southern 
Windward Islands, and a faster weakening trend afterward, 
out of respect to the global model's prediction.

The initial motion is estimated to be westward, or 275/12 kt
and Gonzalo is being steered by a building subtropical ridge to the 
system's north.  The cyclone is expected to increase in forward 
speed toward the west and west-northwest through the entire period. 
The NHC official forecast is an update of the previous advisory and 
is based on the various consensus aids.

Key Messages

1. The risk of wind and rain impacts from Gonzalo in portions of
the southern Windward Islands this weekend continues to increase,
however there is significant uncertainty in how strong Gonzalo will
be when it moves across the islands.

2. Despite the uncertainty in Gonzalo's future intensity, hurricane
or tropical storm conditions are possible across portions of the
southern Windward Islands Saturday and Saturday night.  Hurricane
and Tropical Storm Warning and Watches are currently in effect for 
some of the islands.  Interests in the southern Windward Islands
should monitor the progress of Gonzalo and follow any advice given
by local officials.


INIT  24/0900Z 10.0N  51.8W   50 KT  60 MPH
12H  24/1800Z 10.3N  53.9W   55 KT  65 MPH
24H  25/0600Z 11.0N  56.7W   60 KT  70 MPH
36H  25/1800Z 12.0N  59.9W   65 KT  75 MPH
48H  26/0600Z 13.0N  63.3W   55 KT  65 MPH
60H  26/1800Z 13.7N  66.6W   40 KT  45 MPH
72H  27/0600Z 14.0N  69.9W   35 KT  40 MPH
96H  28/0600Z...DISSIPATED

Forecaster Roberts