Issued at 500 AM AST Sun Sep 21 2025 000
WTNT42 KNHC 210842
TCDAT2
Tropical Storm Gabrielle Discussion Number 17
NWS National Hurricane Center Miami FL AL072025
500 AM AST Sun Sep 21 2025
Gabrielle has become slightly better organized overnight. The large
convective band over the eastern side of the system has persisted,
and within the last few hours deep convection has been bursting over
the low-level center. There have been no microwave passes since the
previous advisory, to determine if the inner core has been able to
close off on the southwestern side. Satellite intensity estimates
from TAFB and SAB were both T/3.5 or 55 kts. Latest objective AiDT,
DPRINT, and DMINT intensity estimates from UW-CIMSS range from 52 to
58 kt. Using these estimates, the intensity is held at 55 kt for
this advisory, although that could be conservative given recent
convective burst. An Air Force Reserve Hurricane Hunter aircraft is
en route to investigate the storm and will provide important details
on the intensity and structure of the system.
The storm is moving north-northwestward at an estimated motion of
335/8 kt. The system continues to be steered by a subtropical ridge
over the Central Atlantic. Over the next few days, Gabrielle will
begin to recurve to the north and eventually northeast between the
western periphery of the ridge and a trough moving offshore the east
coast of the United States. Track models remain tightly clustered
and keep Gabrielle well east of Bermuda on Monday. As Gabrielle
becomes steered within the west-southwesterly wind flow, the system
will accelerate across the Atlantic. By day 3 of the forecast
period, there is some along track model spread with differences in
the forward speed of the system. The NHC track forecast is near the
previous in the short term, but some minor adjustments to slow down
the previous forecast towards the consensus aids were made between
day 3-5.
The environment surrounding the system is favorable for
strengthening over the next couple of days, with light to moderate
wind shear, warm sea surface temperatures, and slightly better
mid-level relative humidity values. As Gabrielle looks to be
establishing an inner core, it should begin to strengthen. The NHC
intensity forecast follows these trends although the intensity
guidance has continued to trend not as aggressive due to how long
the system has taken to establish an inner core, and the peak
intensity forecast has been lowered to 85 kt, which remains near the
higher end of the guidance envelope. In about 48 h, westerly shear
will begin to increase and sea surface temperatures will begin to
cool along the forecast track, thus a weakening trend is forecast.
The long-range forecast along track uncertainty makes it difficult
to assess whether Gabrielle will fully complete extratropical
transition by the end of the period.
KEY MESSAGES:
1. Gabrielle is forecast to become a hurricane later today and pass
east of Bermuda on Monday. While the chances of impacts are
decreasing, interests on Bermuda should continue to monitor forecast
updates since some wind and rainfall impacts are still possible.
2. Swells generated by Gabrielle will continue to affect Bermuda
during the next few days. These swells are expected to reach the
east coast of the United States from North Carolina northward, as
well as Atlantic Canada, beginning later today and continuing
through early this week. These swells are likely to cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.
FORECAST POSITIONS AND MAX WINDS
INIT 21/0900Z 27.2N 60.0W 55 KT 65 MPH
12H 21/1800Z 28.3N 60.9W 65 KT 75 MPH
24H 22/0600Z 29.9N 61.6W 75 KT 85 MPH
36H 22/1800Z 31.5N 61.3W 80 KT 90 MPH
48H 23/0600Z 33.1N 59.7W 85 KT 100 MPH
60H 23/1800Z 34.5N 56.8W 80 KT 90 MPH
72H 24/0600Z 35.4N 52.9W 70 KT 80 MPH
96H 25/0600Z 36.9N 41.7W 60 KT 70 MPH
120H 26/0600Z 40.0N 29.0W 55 KT 65 MPH
$$
Forecaster Kelly
