Official Discussion issued by the National Hurricane Center

Gonzalo (AL072020) DATA RELEASED: 7/23/2020 3:00:00 AM UTC

Copy of official data

Tropical Storm Gonzalo Discussion Number   6
NWS National Hurricane Center Miami FL       AL072020
1100 PM AST Wed Jul 22 2020

A series of earlier microwave passes over Gonzalo reveal a small 
eye feature beneath a relatively ragged, Central Dense Overcast 
with associated -75.5C cloud tops.  Based on the evidence 
of the small eye and a blend of the subjective and objective 
satellite intensity estimates, the initial intensity is raised to 50 
kt for advisory.

The intensity forecast philosophy remains the same as the previous
advisory with a higher than normal degree of uncertainty in the 
latter half of the period as the cyclone moves through the 
Caribbean.  Gonzalo should remain in an environment of relatively 
low shear, although the impacts of dry, stable air and large-scale
subsidence could hamper further intensification in a few days.  It's
worth noting that the ECMWF Ensemble model is showing a pretty 
significant low- to mid-level easterly surge that spreads
just to the north of the cyclone's forecast track and over the
northeastern Caribbean in a couple of days.  This predicted event
could possibly curtail strengthening at that time.  On the 
other hand, with the exception of the ECMWF, the global models now 
show the cyclone maintaining tropical storm strength while moving 
into the eastern Caribbean.  The official intensity forecast is 
adjusted slightly above the previous forecast, hedging toward the 
HFIP HCCA consensus and the IVCN multi-model intensity aid 
solutions.  It should also be noted that the small size of this 
system makes it susceptible to significant fluctuations in 
intensity, both upward and downward.

The initial motion is estimated to be due west, or 270/10 kt.  
There is no change to the track forecast philosophy.  Gonzalo is on 
the south side of a low- to mid-level tropospheric ridge, and this 
feature should steer the storm generally westward at a faster 
forward speed for the next few days.  After that time, a motion 
toward  the west-northwest is expected.  The NHC track forecast is 
nudged a bit to the north of the previous one and is close to the 
various consensus aids.

Interests in the Windward Islands should continue to monitor the 
progress of this system.  A Hurricane Watch is now issued for 
Barbados.


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  23/0300Z  9.9N  45.9W   50 KT  60 MPH
12H  23/1200Z 10.0N  47.6W   60 KT  70 MPH
24H  24/0000Z 10.2N  50.0W   65 KT  75 MPH
36H  24/1200Z 10.6N  52.7W   70 KT  80 MPH
48H  25/0000Z 11.2N  55.5W   75 KT  85 MPH
60H  25/1200Z 11.8N  58.6W   70 KT  80 MPH
72H  26/0000Z 12.6N  61.8W   60 KT  70 MPH
96H  27/0000Z 14.3N  67.6W   50 KT  60 MPH
120H  28/0000Z 15.6N  73.1W   40 KT  45 MPH

$$
Forecaster Roberts