Issued at 500 AM AST Sat Sep 20 2025 000
WTNT42 KNHC 200837
TCDAT2
Tropical Storm Gabrielle Discussion Number 13
NWS National Hurricane Center Miami FL AL072025
500 AM AST Sat Sep 20 2025
Although Gabrielle’s low-level center is obscured by high cirrus
clouds, an 0555 UTC AMSR2 microwave pass confirms that it is still
located to the west of the deep convective mass due to continued
moderate westerly shear. The convection itself has been quite
intense, with a high density of lightning co-located with cloud-top
temperatures as cold as -85 to -90 degrees Celsius. The latest
satellite intensity estimates, as well as ASCAT data from yesterday
evening, still support an intensity of 45 kt. The ASCAT data also
showed that there are currently no tropical-storm-force winds on
Gabrielle’s western side.
Mid-tropospheric high pressure over the central Atlantic is
steering Gabrielle northwestward, or 315 degrees at 11 kt. The
storm is expected to recurve between the western periphery of the
high and a trough located over the southeastern United States over
the next several days. Mostly because of an adjustment of
Gabrielle’s initial position, the new NHC track forecast has been
adjusted a bit west of the previous prediction during the first 3
days of the forecast. That said, all of the reliable track models
continue to keep the core of Gabrielle well east of Bermuda Sunday
night and Monday during the recurvature. By Tuesday, global model
fields indicate that Gabrielle will become embedded in fast zonal
mid-latitude flow, and there has been a significant southward shift
in the track models on days 4 and 5. The NHC track forecast has
also been adjusted southward at those times, close to the HCCA and
Google DeepMind ensemble but not as far south as the GFS and many
of the multi-model consensus aids.
Vertical shear is expected to decrease over the next day or two,
which should allow Gabrielle’s circulation to become more
vertically aligned, leading to strengthening. The intensity models
are generally split into two camps. The statistical-dynamical
models (SHIPS and LGEM) and global models (GFS and ECMWF) are more
subdued on the amount of strengthening that Gabrielle might
experience. The regional hurricane models, as well as the HCCA and
Florida State Superensemble, are more aggressive, with the HAFS
models in particular bringing Gabrielle to major hurricane strength
in about 2 days. While not going that high, the NHC intensity
forecast is close to the other models in that camp and continues to
show a possible peak of 90 kt in 60-72 hours. With the southward
shift in the track forecast at days 4 and 5, Gabrielle’s
extratropical transition has likely been delayed, and the official
forecast continues to depict a tropical cyclone through the next 5
days.
KEY MESSAGES:
1. Gabrielle is forecast to become a hurricane by Sunday and pass
east of Bermuda Sunday night and Monday. Interests on Bermuda
should continue to monitor Gabrielle’s forecasts since some wind
and rainfall impacts are still possible.
2. Swells generated by Gabrielle are beginning to reach Bermuda
and will build through the weekend. These swells are likely
to cause life-threatening surf and rip current conditions.
FORECAST POSITIONS AND MAX WINDS
INIT 20/0900Z 24.3N 58.1W 45 KT 50 MPH
12H 20/1800Z 25.4N 59.3W 50 KT 60 MPH
24H 21/0600Z 27.0N 60.5W 60 KT 70 MPH
36H 21/1800Z 28.6N 61.6W 70 KT 80 MPH
48H 22/0600Z 30.3N 62.1W 80 KT 90 MPH
60H 22/1800Z 32.1N 61.3W 90 KT 105 MPH
72H 23/0600Z 34.0N 59.1W 90 KT 105 MPH
96H 24/0600Z 37.0N 50.6W 80 KT 90 MPH
120H 25/0600Z 38.7N 38.5W 65 KT 75 MPH
$$
Forecaster Berg
