Tropical Storm Gabrielle
Public Storm Discussion
000
WTNT42 KNHC 180252
TCDAT2
Tropical Storm Gabrielle Discussion Number 4
NWS National Hurricane Center Miami FL AL072025
1100 PM AST Wed Sep 17 2025
The overall structure of Gabrielle hasn't changed too much. The
cloud pattern of the cyclone consists of a large comma shape.
GOES-19 CIRA proxy-vis imagery and a recent 17/2342 UTC ASCAT-B
overpass clearly indicate that the surface wind center is at the
bottom of the upper portion of the comma head. The strongest ASCAT
wind vectors are the same magnitudes as the pass from 12 hours
prior, so the intensity is held at 45 kt for this advisory.
Gabrielle still has a very large and broad envelope of convection
and winds. It is quite atypical to see a structure like this for a
tropical cyclone in this part of the world. Strong westerly shear
should continue on Thursday, then gradually abate at some point on
Friday. The other factor that is detrimentally impacting Gabrielle
is the very dry air seen on water vapor imagery in the open area of
the comma, to the south and west of the center. Even after the
shear abates, Gabrielle will continue moving through an environment
of dry air through Friday, with moistening along its path over the
weekend. The official intensity forecast has been decreased during
the 24-48 h period, in agreement with most of the reliable intensity
guidance. The new NHC intensity forecast is near the middle of the
guidance envelope through 48 hours, then near the high end of the
guidance thereafter, and still calls for Gabrielle to be a hurricane
at days 4-5.
The center has jogged westward since the previous advisory, but the
longer term motion is estimated to be west-northwestward, or 300/14
kt. A similar motion is expected for the next couple of days,
followed by a gradual turn toward the west-northwest as Gabrielle
moves on the south side of a subtropical ridge. Over the weekend,
the cyclone should round the southwestern periphery of the ridge and
turn northwestward as it catches up to a slow-moving upper-level low
that should be located just west of Gabrielle. A northward motion
is expected in 4-5 days as Gabrielle gets closer to the mid-latitude
westerlies, which should induce a northeastward turn in about 5
days. The new NHC track forecast is shifted significantly to the
left (southwest) of the previous forecast through 72 h but near the
previous track again at days 4-5. The forecast is in fairly good
agreement with the Google Deep Mind ensemble mean through 72 h, then
leans toward the HCCA Corrected Consensus at days 4-5.
Track forecast confidence remains relatively low. This system
should pass well east and north of the Leeward Islands, but
interests in Bermuda should monitor forecasts during the next
several days.
FORECAST POSITIONS AND MAX WINDS
INIT 18/0300Z 19.5N 49.5W 45 KT 50 MPH
12H 18/1200Z 20.3N 51.0W 45 KT 50 MPH
24H 19/0000Z 21.3N 52.9W 40 KT 45 MPH
36H 19/1200Z 22.2N 54.9W 40 KT 45 MPH
48H 20/0000Z 23.3N 56.9W 40 KT 45 MPH
60H 20/1200Z 24.5N 58.8W 45 KT 50 MPH
72H 21/0000Z 25.8N 60.3W 50 KT 60 MPH
96H 22/0000Z 28.9N 62.7W 65 KT 75 MPH
120H 23/0000Z 32.5N 62.0W 75 KT 85 MPH
$$
Forecaster Hagen Back to Tropical Storm Gabrielle Page
WTNT42 KNHC 180252
TCDAT2
Tropical Storm Gabrielle Discussion Number 4
NWS National Hurricane Center Miami FL AL072025
1100 PM AST Wed Sep 17 2025
The overall structure of Gabrielle hasn't changed too much. The
cloud pattern of the cyclone consists of a large comma shape.
GOES-19 CIRA proxy-vis imagery and a recent 17/2342 UTC ASCAT-B
overpass clearly indicate that the surface wind center is at the
bottom of the upper portion of the comma head. The strongest ASCAT
wind vectors are the same magnitudes as the pass from 12 hours
prior, so the intensity is held at 45 kt for this advisory.
Gabrielle still has a very large and broad envelope of convection
and winds. It is quite atypical to see a structure like this for a
tropical cyclone in this part of the world. Strong westerly shear
should continue on Thursday, then gradually abate at some point on
Friday. The other factor that is detrimentally impacting Gabrielle
is the very dry air seen on water vapor imagery in the open area of
the comma, to the south and west of the center. Even after the
shear abates, Gabrielle will continue moving through an environment
of dry air through Friday, with moistening along its path over the
weekend. The official intensity forecast has been decreased during
the 24-48 h period, in agreement with most of the reliable intensity
guidance. The new NHC intensity forecast is near the middle of the
guidance envelope through 48 hours, then near the high end of the
guidance thereafter, and still calls for Gabrielle to be a hurricane
at days 4-5.
The center has jogged westward since the previous advisory, but the
longer term motion is estimated to be west-northwestward, or 300/14
kt. A similar motion is expected for the next couple of days,
followed by a gradual turn toward the west-northwest as Gabrielle
moves on the south side of a subtropical ridge. Over the weekend,
the cyclone should round the southwestern periphery of the ridge and
turn northwestward as it catches up to a slow-moving upper-level low
that should be located just west of Gabrielle. A northward motion
is expected in 4-5 days as Gabrielle gets closer to the mid-latitude
westerlies, which should induce a northeastward turn in about 5
days. The new NHC track forecast is shifted significantly to the
left (southwest) of the previous forecast through 72 h but near the
previous track again at days 4-5. The forecast is in fairly good
agreement with the Google Deep Mind ensemble mean through 72 h, then
leans toward the HCCA Corrected Consensus at days 4-5.
Track forecast confidence remains relatively low. This system
should pass well east and north of the Leeward Islands, but
interests in Bermuda should monitor forecasts during the next
several days.
FORECAST POSITIONS AND MAX WINDS
INIT 18/0300Z 19.5N 49.5W 45 KT 50 MPH
12H 18/1200Z 20.3N 51.0W 45 KT 50 MPH
24H 19/0000Z 21.3N 52.9W 40 KT 45 MPH
36H 19/1200Z 22.2N 54.9W 40 KT 45 MPH
48H 20/0000Z 23.3N 56.9W 40 KT 45 MPH
60H 20/1200Z 24.5N 58.8W 45 KT 50 MPH
72H 21/0000Z 25.8N 60.3W 50 KT 60 MPH
96H 22/0000Z 28.9N 62.7W 65 KT 75 MPH
120H 23/0000Z 32.5N 62.0W 75 KT 85 MPH
$$
Forecaster Hagen Back to Tropical Storm Gabrielle Page