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Tropical Storm Gabrielle Discussion Number  11
NWS National Hurricane Center Miami FL       AL072025
500 PM AST Fri Sep 19 2025

Gabrielle's cloud pattern has changed significantly since the last 
advisory. The previously noted shear pattern has changed to a curved 
convective band pattern, and the previously exposed low-level center 
has become at least partly covered by cirrus clouds spreading 
westward from the convection.  This change suggests that the storm 
is starting to encounter the forecast decrease in vertical shear.  
At this time, this change has not led to an increase in the various 
satellite intensity estimates, so the initial intensity remains 45 
kt.

The initial motion is 300/10 kt.  Gabrielle is on the southwest side 
of the subtropical ridge, and during the next 2-3 days it is 
expected to turn northward between the ridge to the east and and a 
mid-latitude trough over the eastern United States and the far 
western Atlantic.  The track guidance remains fairly tightly 
clustered during this time, although the consensus models have 
shifted a little to the left since the last advisory. This part of 
the new forecast track is nudged a little to the left, but still 
lies east of the consensus models.  After 3 days, Gabrielle is 
expected to recurve into the westerlies and accelerate 
northeastward. The guidance shows more spread during this time, with 
the GFS being to the left/north and faster than most of the 
guidance, while the ECMWF is to the right/south and slower. Despite 
the spread, the consensus models and the center of the guidance 
envelope are have changed little since the last advisory for this 
part of the forecast. Thus, the new forecast is similar to, but 
slightly slower than, the previous forecast. The reliable track 
models still show Gabrielle's center passing at least 130 n mi east 
of Bermuda in 60-72 h. However, interests on the island should 
continue to monitor Gabrielle's progress since NHC's average track 
error at 72 h is about 90 n mi, and hazards can extend well away 
from the center. There remains a 20-25 percent chance of 
tropical-storm-force winds occurring on Bermuda.
 
Gabrielle is now forecast to be in a light-to-moderate shear 
environment for the next 72 h, which should allow strengthening 
that would be tempered mainly by occasional entrainment of dry air. 
The new intensity forecast has been tweaked a bit to show a peak 
intensity of 90 kt at 72 h.  Extratropical transition should be 
underway by 120 h, and could be complete by that time if the 
cyclone takes a more northward track similar to the GFS. However, a 
more southward track similar to the ECMWF would delay transition, 
and based on the uncertainty the new intensity forecast keeps the 
system as a tropical cyclone at 120 h.
 
 
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 monitor Gabrielle's forecasts since it is too soon to
specify the magnitude of potential wind and rainfall impacts.
 
2.  Swells generated by Gabrielle are expected to reach Bermuda
tonight and build through the weekend.  These swells are likely
to cause life-threatening surf and rip current conditions.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  19/2100Z 22.4N  56.6W   45 KT  50 MPH
 12H  20/0600Z 23.5N  58.0W   45 KT  50 MPH
 24H  20/1800Z 25.0N  59.4W   55 KT  65 MPH
 36H  21/0600Z 26.8N  60.6W   65 KT  75 MPH
 48H  21/1800Z 28.6N  61.4W   75 KT  85 MPH
 60H  22/0600Z 30.6N  61.6W   85 KT 100 MPH
 72H  22/1800Z 33.0N  59.9W   90 KT 105 MPH
 96H  23/1800Z 38.1N  51.3W   90 KT 105 MPH
120H  24/1800Z 42.1N  38.4W   70 KT  80 MPH
 
$$
Forecaster Beven
 
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