ATL: DON - Advisories

[cycloneye]

Tropical Storm Don Discussion Number 41
NWS National Hurricane Center Miami FL AL052023
900 AM GMT Mon Jul 24 2023

Deep convection has evaporated near Don, though it hasn't been free
of convection long enough to declare it post-tropical yet. The
initial wind speed is lowered to 40 kt, in concert with the Dvorak
estimates that are decreasing as fast as the rules allow. Don
should become post-tropical soon and continue to weaken due to
persistent cold waters and shear.

The storm is moving east-northeastward at about 16 kt, and that
general motion is likely to persist until the system dissipates
in about a day. All of the global models show Don opening up into
a trough in 18-24 hours, so the dissipation phase is moved to that
time. No other significant changes were made to the forecast.

Don has been a very long-lasting tropical cyclone (including
subtropical stages) for the month of July. Preliminary data
indicate that the storm is the 5th longest-lasting system on
record for the month, just behind Emily of 2005.


FORECAST POSITIONS AND MAX WINDS

INIT 24/0900Z 47.0N 43.0W 40 KT 45 MPH
12H 24/1800Z 47.9N 39.7W 35 KT 40 MPH...POST-TROPICAL
24H 25/0600Z...DISSIPATED

$$
Forecaster Blake

[cycloneye]

Post-Tropical Cyclone Don Discussion Number 42
NWS National Hurricane Center Miami FL AL052023
300 PM GMT Mon Jul 24 2023

Satellite imagery shows that Don lacks sufficient deep convection to
classify the system as a tropical cyclone, and it is now post
tropical. The initial wind speed remains at 40 kt for this
advisory, based on a recent ASCAT-B scatterometer pass. Don should
slowly weaken over the next day or so while moving over cold waters
and within high vertical wind shear.

The system is moving east-northeastward at about 17 kt, and this
general motion will likely to continue until Don dissipates in
about a day. Most of the global guidance has post-tropical Don
opening up into a trough and becoming absorbed by a larger
extratropical low over the north Atlantic tomorrow. Very few changes
were made to the previous NHC forecast.

Don has been a very long-lasting tropical cyclone (including
subtropical stages) for the month of July. Preliminary data
indicate that the storm is the 5th longest-lasting system on record
for the month, just behind Emily of 2005.

This is the last advisory on Don. Additional information on this
system can be found in High Seas Forecasts issued by the National
Weather Service...under AWIPS header NFDHSFAT1 and WMO header
FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSDAT1.php


FORECAST POSITIONS AND MAX WINDS

INIT 24/1500Z 47.6N 40.7W 40 KT 45 MPH...POST-TROPICAL
12H 25/0000Z 48.1N 36.9W 35 KT 40 MPH...POST-TROPICAL
24H 25/1200Z...DISSIPATED

$$
Forecaster Kelly/Pasch