Official Discussion issued by the National Hurricane Center

Don (AL052023) DATA RELEASED: 7/19/2023 9:00:00 PM UTC

Copy of official data

Tropical Storm Don Discussion Number  23
NWS National Hurricane Center Miami FL       AL052023
900 PM GMT Wed Jul 19 2023

Don has continued to become better organized during the day, with a 
deep convective band now curving more than halfway around the 
center, and an expanding outflow pattern especially southeast of 
the storm.  While the western side of the circulation still has a 
lot of dry air lurking, it seems like the lack of shear is allowing 
the core of the cyclone to develop.  Dvorak estimates have 
increased, and a blend of the latest data gives an initial wind 
speed of 40 kt.  Scatterometer has missed the core for about the 
past day, so hopefully tonight's passes will validate the improving 
satellite presentation.

Further intensification is likely for the next day or so while Don 
moves over a local maximum in sea-surface temperatures (SSTs) with 
light shear.  Thereafter, the environment becomes less conducive 
with cooling SSTs, drier environmental air, and perhaps an increase 
in shear.  The forecast is kept steady through the end of the work 
week, then some weakening while Don crosses its own cool wake.  The 
NHC wind speed prediction is bumped up from the last one, consistent 
with the latest model consensus, and most of the guidance is in 
pretty good agreement on this scenario.  The storm should lose all 
of its deep convection and become post-tropical late Sunday or on 
Monday after it crosses north of the Gulf Stream.

Don has turned westward, now moving a bit faster at 7 kt.  The 
system should turn west-northwestward tomorrow as it moves beneath a 
large blocking ridge over the north-central Atlantic, with no 
changes to the forecast in the short term.  However, there has been 
a pretty significant synoptic pattern shift in the models by Friday 
with the blocking ridge much slower to depart, resulting in Don 
moving more to the northwest and not accelerating as quickly 
northeastward.  The new forecast follows the guidance trend, but for 
continuity concerns, the forecast is still faster than most of the 
guidance, and further changes will likely be required on the next 


INIT  19/2100Z 33.8N  40.3W   40 KT  45 MPH
12H  20/0600Z 33.7N  41.3W   45 KT  50 MPH
24H  20/1800Z 34.1N  42.7W   50 KT  60 MPH
36H  21/0600Z 34.8N  44.3W   50 KT  60 MPH
48H  21/1800Z 35.9N  46.1W   50 KT  60 MPH
60H  22/0600Z 37.2N  47.6W   45 KT  50 MPH
72H  22/1800Z 39.0N  48.6W   45 KT  50 MPH
96H  23/1800Z 43.0N  48.0W   45 KT  50 MPH
120H  24/1800Z 45.5N  44.0W   35 KT  40 MPH...POST-TROPICAL

Forecaster Blake