NATL: GABRIELLE - Advisories

[cycloneye]

BULLETIN
Tropical Depression Seven Advisory Number 1
NWS National Hurricane Center Miami FL AL072025
500 AM AST Wed Sep 17 2025

...TROPICAL DEPRESSION FORMS OVER THE CENTRAL ATLANTIC...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...13.7N 45.9W
ABOUT 1185 MI...1905 KM ESE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES





Tropical Depression Seven Discussion Number 1
NWS National Hurricane Center Miami FL AL072025
500 AM AST Wed Sep 17 2025

Satellite data indicate that Invest 92L over the central tropical
Atlantic has now developed into a tropical depression. ASCAT data
from around 00Z showed that the circulation of the system had
improved, and although it was not well defined at the time of the
pass, the system was only lacking some northerly winds on its west
side. Since deep convection has been persisting and consolidating
near the center, it appears to now meet the convective and
circulation criteria needed to be considered a tropical cyclone.
However, it should be noted that the system is quite large and there
is still considerable north-south elongation in the low-level
structure. The initial intensity is set at 30 kt based on a blend of
the ASCAT data and the latest Dvorak estimate from TAFB. The
development of this system breaks a nearly 3-week streak of no
tropical cyclones in the Atlantic basin during the peak of the
hurricane season.

The depression is well away from land and roughly midway between the
Cabo Verde Islands and the Windward Islands. The system is
estimated to be moving westward at 11 kt, but this is of low
confidence since the center has only recently formed. A turn to the
northwest, perhaps influenced by a center formation, is expected to
occur soon as the depression moves toward a weakness in the Atlantic
subtropical ridge caused by a mid- to upper-level low to its north.
The models show this low weakening in a day or two, which will
likely cause the cyclone to turn back to the west-northwest late
this week. However, the system should reach the western periphery
of the ridge this weekend, resulting in a turn to the northwest or
north. The NHC track forecast is a little to the right of the
consensus aids, giving more weight to the ECMWF and Google Deep Mind
predictions, which are faster and on the right side of the guidance.
Based on the steering pattern, and deterministic and ensemble model
solutions, there is high confidence that this system should pass
well east of the Windward and Leeward Islands. Interests in Bermuda
should monitor forecasts of the depression over the next several
days.

Only modest strengthening is expected over the next day or two as
the depression continues to battle moderate shear from the
aforementioned low aloft and intrusions of dry air. However, more
notable strengthening seems likely by the weekend when the system
moves into more conducive environmental conditions. The NHC
intensity forecast shows the system reaching hurricane strength
toward the end of the period, but it should be noted that the spread
in the models at that time is significant and ranges from solutions
showing a weak low to a major hurricane. This prediction is
generally in line with the IVCN aid.


FORECAST POSITIONS AND MAX WINDS

INIT 17/0900Z 13.7N 45.9W 30 KT 35 MPH
12H 17/1800Z 15.8N 47.4W 35 KT 40 MPH
24H 18/0600Z 17.6N 49.6W 40 KT 45 MPH
36H 18/1800Z 19.0N 51.9W 40 KT 45 MPH
48H 19/0600Z 19.7N 54.0W 45 KT 50 MPH
60H 19/1800Z 20.4N 55.9W 50 KT 60 MPH
72H 20/0600Z 21.6N 57.6W 55 KT 65 MPH
96H 21/0600Z 24.0N 60.0W 65 KT 75 MPH
120H 22/0600Z 26.9N 63.0W 75 KT 85 MPH

$$
Forecaster Cangialosi

[cycloneye]

BULLETIN
Tropical Storm Gabrielle Advisory Number 2
NWS National Hurricane Center Miami FL AL072025
Issued by the NWS Weather Prediction Center College Park MD
1100 AM AST Wed Sep 17 2025

...GABRIELLE FORMS OVER THE CENTRAL TROPICAL ATLANTIC...
...FORECAST TO REMAIN OVER OPEN WATERS FOR SEVERAL DAYS...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...17.5N 46.6W
ABOUT 1085 MI...1745 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 22 MPH...35 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES



Tropical Storm Gabrielle Discussion Number 2
NWS National Hurricane Center Miami FL AL072025
Issued by the NWS Weather Prediction Center College Park MD
1100 AM AST Wed Sep 17 2025

Satellite imagery this morning indicates that the large system is
not well-organized, with an elongated circulation
oriented from north-northwest to south-southeast containing a few
embedded swirls. The advisory center is a mean center of those
swirls, with any associated convection well east of the position due
to southwesterly shear. While it wouldn't appear so from
conventional satellite data, a recent scatterometer pass indicates
upwards of 40-kt winds present, generally northeast and southeast of
the center of circulation. Although the system is at best
marginally well defined, there is enough data to support an initial
intensity of 40 kt, and the depression is named Gabrielle.

Little strengthening is anticipated over the next 48 hours as
Gabrielle faces an unfavorable shear environment from an
upper-level trough and a possible center re-formation, and the
forecast intensity remains nearly steady through Friday. By this
weekend, a more conducive environment is anticipated, which should
allow for gradual intensification. Gabrielle is forecast to become
a hurricane by 96 hours. The NHC intensity forecast remains
fairly similar to the previous forecast cycle, but it should be
noted that there remains considerable spread in the solutions and
overall forecast intensity confidence is low.

Gabrielle is well away from land and about midway between the Cabo
Verde Islands and the Windward Islands. The current estimated
motion is north-northwestward, but this is highly uncertain as the
center could be re-forming to the north. The system is forecast to
move northwestward to west-northwestward due to the subtropical
ridge for the next several days. While the forecast has been
adjusted to the north from the previous one, this is almost
exclusively due to the jump in the initial position. This is a
highly uncertain forecast until a better defined center forms.
Based on the recent trends, this system should pass well east and
north of the Windward and Leeward Islands, but interests in Bermuda
should monitor forecasts during the next several days.

FORECAST POSITIONS AND MAX WINDS

INIT 17/1500Z 17.5N 46.6W 40 KT 45 MPH
12H 18/0000Z 19.5N 48.5W 45 KT 50 MPH
24H 18/1200Z 20.8N 50.6W 45 KT 50 MPH
36H 19/0000Z 21.8N 52.6W 45 KT 50 MPH
48H 19/1200Z 22.7N 54.6W 45 KT 50 MPH
60H 20/0000Z 23.5N 56.6W 50 KT 60 MPH
72H 20/1200Z 24.7N 58.3W 55 KT 65 MPH
96H 21/1200Z 27.4N 60.8W 65 KT 75 MPH
120H 22/1200Z 30.0N 62.5W 75 KT 85 MPH

$$
Forecaster Taylor/Blake

[cycloneye]

BULLETIN
Tropical Storm Gabrielle Advisory Number 3
NWS National Hurricane Center Miami FL AL072025
Issued by the NWS Weather Prediction Center College Park MD
500 PM AST Wed Sep 17 2025

...CENTER OF GABRIELLE RE-FORMS NORTH OF THE PREVIOUS ADVISORY
POSITION...

SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...19.4N 48.0W
ABOUT 990 MI...1595 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES



Tropical Storm Gabrielle Discussion Number 3
NWS National Hurricane Center Miami FL AL072025
Issued by the NWS Weather Prediction Center College Park MD
500 PM AST Wed Sep 17 2025

The biggest change with Gabrielle today has been that the center
has re-formed farther to the north compared with the previous
advisory, similar to earlier model forecasts. While satellite
imagery continues to indicate an elongated circulation with
multiple embedded swirls, it has become better defined than this
morning, and we have continued to make the center position on the
advisory a mean of those swirls. A second scatterometer pass that
intersected the northern semicircle of the storm after the 15Z
advisory did show a large area of 40-45 kt winds. Therefore, the
initial intensity has been increased to 45 knots, even though the
system does not appear appreciably more organized.

The first part of the track forecast has been shifted to the north
based on the recent center re-formation. Gabrielle is moving
northwestward now, and a west-northwestward to northwestward track
is anticipated for the next few days due to steering from the
subtropical ridge. The fundamental forecast question for both
track and intensity is related to the wind shear Gabrielle will
experience and the structural change. Little intensity change is
shown for the next couple of days while the storm remains in a
high-shear but high SST/instability environment. There actually
appears to be good consensus that the shear will relax after Friday,
but there are significant model differences on how much. This leads
to a considerable amount of track and intensity spread as the
forecast progresses into the weekend. Generally the models that
relax the shear more substantially, to around 10 knots or less, show
more intensification and a track to the right of model consensus.
Since the NHC intensity forecast is a bit above the model average
(similar to the last prediction), we favor a track forecast to the
right of the model blend, more consistent with the HCCA corrected
consensus, Google Deep Mind ensemble, and ECMWF ensemble.

Overall, forecast confidence remains relatively low. Based on the
recent trends, this system should pass well east and north of the
Windward and Leeward Islands, but interests in Bermuda should
monitor forecasts during the next several days.

FORECAST POSITIONS AND MAX WINDS

INIT 17/2100Z 19.4N 48.0W 45 KT 50 MPH
12H 18/0600Z 20.6N 49.7W 45 KT 50 MPH
24H 18/1800Z 21.7N 51.6W 45 KT 50 MPH
36H 19/0600Z 22.7N 53.5W 45 KT 50 MPH
48H 19/1800Z 23.5N 55.5W 45 KT 50 MPH
60H 20/0600Z 24.7N 57.4W 50 KT 60 MPH
72H 20/1800Z 26.2N 59.0W 55 KT 65 MPH
96H 21/1800Z 29.0N 62.0W 65 KT 75 MPH
120H 22/1800Z 32.0N 62.5W 75 KT 85 MPH

$$
Forecaster Lamers/Blake

[cycloneye]

BULLETIN
Tropical Storm Gabrielle Advisory Number 4
NWS National Hurricane Center Miami FL AL072025
1100 PM AST Wed Sep 17 2025

...POORLY ORGANIZED GABRIELLE BATTLING STRONG WIND SHEAR AS IT JOGS
TOWARD THE WEST-NORTHWEST...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...19.5N 49.5W
ABOUT 895 MI...1435 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES




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

[cycloneye]

BULLETIN
Tropical Storm Gabrielle Advisory Number 5
NWS National Hurricane Center Miami FL AL072025
500 AM AST Thu Sep 18 2025

...GABRIELLE STRUGGLING OVER THE CENTRAL ATLANTIC...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...20.0N 50.3W
ABOUT 845 MI...1360 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES




Tropical Storm Gabrielle Discussion Number 5
NWS National Hurricane Center Miami FL AL072025
500 AM AST Thu Sep 18 2025

Gabrielle continues to struggle and consists of a swirl of low-level
clouds with patches of deep convection over the northeast and
southeast quadrants of the storm. The poor structure is due to
westerly vertical wind shear and a significant amount of dry air
that is continuously entraining into the circulation. The initial
intensity is held at 45 kt based on the earlier ASCAT data, but this
value is well above the latest satellite intensity estimates.

The atmospheric conditions are expected to remain hostile for a
couple more days, so it seems likely that Gabrielle will either hold
steady or lose strength during that time. However, the models
suggest that the storm could move into more conducive conditions
late in the weekend and early next week, which should cause
Gabrielle to become more symmetric and strengthen. The NHC
intensity forecast is near the middle of the guidance envelope for
the first 3 days, but lies closer to the high end of the guidance at
days 4 and 5.

Gabrielle has been moving erratically due to the storm
reorganizing over the past 12 to 24 hours, but smoothing through
the fixes yields a west-northwestward motion at 13 kt. A continued
west-northwest to northwest motion at about the same forward speed
is expected during the next few days as the storm continues to be
primarily steered by a subtropical ridge over the central Atlantic.
A turn toward the north or northeast is forecast to occur late this
weekend and early next week when Gabrielle rounds the western
periphery of the ridge. The NHC track forecast is very similar to
the previous one from 12 to 72 h, but it has been shifted a little
to the right at days 4 and 5 to be in better agreement with the
latest guidance.

Confidence in the long range forecast remains low, and interests in
Bermuda should continue to monitor Gabrielle over the next several
days.


FORECAST POSITIONS AND MAX WINDS

INIT 18/0900Z 20.0N 50.3W 45 KT 50 MPH
12H 18/1800Z 20.8N 51.7W 40 KT 45 MPH
24H 19/0600Z 21.8N 53.6W 40 KT 45 MPH
36H 19/1800Z 22.8N 55.7W 40 KT 45 MPH
48H 20/0600Z 24.0N 57.7W 40 KT 45 MPH
60H 20/1800Z 25.3N 59.4W 45 KT 50 MPH
72H 21/0600Z 26.8N 60.7W 50 KT 60 MPH
96H 22/0600Z 30.2N 61.5W 65 KT 75 MPH
120H 23/0600Z 34.4N 58.3W 75 KT 85 MPH

$$
Forecaster Cangialosi

[cycloneye]

BULLETIN
Tropical Storm Gabrielle Advisory Number 6
NWS National Hurricane Center Miami FL AL072025
Issued by the NWS Weather Prediction Center College Park MD
1100 AM AST Thu Sep 18 2025

...GABRIELLE STILL STRUGGLING OVER THE CENTRAL ATLANTIC...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...20.3N 51.7W
ABOUT 755 MI...1220 KM ENE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES



Tropical Storm Gabrielle Discussion Number 6
NWS National Hurricane Center Miami FL AL072025
Issued by the NWS Weather Prediction Center College Park MD
1100 AM AST Thu Sep 18 2025

Gabrielle continues to struggle this morning as a pronounced swirl
of low-level clouds is unable to muster up much in the way of deep
convection near its center. Gabrielle's poor structure is due to
ongoing westerly vertical wind shear and a significant amount of
dry air entrainment that is infiltrating its circulation. The
initial intensity is held at 45 kt based on recent scatterometer
data of at least 40 kt, but this value remains above the latest
satellite intensity estimates.

Atmospheric conditions are expected to remain hostile for a
couple more days, meaning Gabrielle is likely maintain its
current intensity or weaken during that time. It is even possible
it could decay into a non-convective post-tropical low for a time.
Assuming it survives, most guidance suggests that the storm will
move into more conducive conditions that persist into early next
week, allowing Gabrielle to organize and strengthen as it tracks
north to northeastward. The NHC intensity forecast is near the low
end of the guidance envelope for the first 3 days, but lies closer
to the middle of the guidance at days 4 and 5.

Gabrielle's more erratic track over the past 24-48 hours has now
smoothed out over the past 12-24 hours with a west-northwestward
motion at 13 kt. This west-northwest to northwest motion should
persist over the next few days as the storm is steered primarily by
a subtropical ridge over the central Atlantic. A turn toward the
north or northeast is forecast to occur late this weekend and early
next week when Gabrielle rounds the western periphery of the ridge
and a frontal system approaches from the west. The NHC track
forecast was adjusted just west of track given the guidance's more
westerly consensus of a weaker system inside the next 48 hours.
Gabrielle's forward motion is a little faster as well, especially
between hours 48-120 when it should accelerate thanks to increased
steering flow on the western side of the Atlantic ridge.

Confidence in the long range forecast remains low, and interests in
Bermuda should continue to monitor Gabrielle over the next several
days.


FORECAST POSITIONS AND MAX WINDS

INIT 18/1500Z 20.3N 51.7W 45 KT 50 MPH
12H 19/0000Z 21.1N 53.2W 40 KT 45 MPH
24H 19/1200Z 22.1N 55.3W 40 KT 45 MPH
36H 20/0000Z 23.2N 57.4W 40 KT 45 MPH
48H 20/1200Z 24.4N 59.2W 40 KT 45 MPH
60H 21/0000Z 25.9N 60.6W 45 KT 50 MPH
72H 21/1200Z 27.7N 61.5W 50 KT 60 MPH
96H 22/1200Z 31.4N 61.9W 70 KT 80 MPH
120H 23/1200Z 36.5N 56.2W 80 KT 90 MPH

$$
Forecaster Mullinax/Blake