BULLETIN
Hurricane Gabrielle Advisory Number 19
NWS National Hurricane Center Miami FL AL072025
500 PM AST Sun Sep 21 2025
...GABRIELLE BECOMES A HURRICANE...
SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...28.5N 61.7W
ABOUT 320 MI...515 KM SE OF BERMUDA
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...992 MB...29.30 INCHES
Hurricane Gabrielle Discussion Number 19
NWS National Hurricane Center Miami FL AL072025
500 PM AST Sun Sep 21 2025
We are fortunate to have three NOAA aircraft (two P3's and one G-IV)
which are conducting research missions into Gabrielle this
afternoon. The data they have provided has been valuable, showing
the storm has become better aligned in the low to mid-levels
compared to this morning, though the eyewall structure has been
coming and going due to occasional dry air mixing out near the
cyclone's core. The highest 750 mb flight-level winds were up to 70
kt, which using a typical 0.85 reduction supports 60 kt. However,
the Tail Doppler Radar (TDR) on board one of the NOAA-P3 aircraft
showed a swath of 0.5 km winds up to 79 kt in the eastern semicircle
at 1741 UTC. Using a more conservative 0.80 reduction factor
for this level supports an intensity of 65 kt, and Gabrielle has
become a hurricane.
Recon fixes this afternoon show that the hurricane is beginning to
turn more north-northwest, with the estimated motion now at
330/9-kt. The track reasoning in the short-term remains the same as
this morning, with Gabrielle rounding the western edge of the
subtropical ridge, which should allow the hurricane to turn
northward and then northeastward over the next couple of days. There
was another small adjustment west in the track over the next 24 h,
but this still keeps Gabrielle's wind field well to the east of
Bermuda when it passes its latitude towards the end of the day
Monday. Thereafter, the hurricane should begin to gradually
accelerate in the westerly flow around the north side of the
aforementioned ridge. The biggest change in the track forecast
towards the end of the period is that the guidance continues to
shift a little more southward, especially the most recent 12 UTC
ECMWF, which shifted closer to the Azores in 4-5 days. For now,
the NHC track forecast will only be shifted a little southward this
cycle, choosing to stay closer to the reliable consensus aids TVCN
and HCCA, though it's possible some southward adjustments will
be needed in subsequent forecasts.
While the structure of Gabrielle on geostationary satellite is still
a little ragged with warmer cloud tops than this morning, it has
become more axis-symmetric, and a recent AMSR2 microwave pass at
1733 UTC indicates a thicker 37-GHz cyan ring than the one observed
this morning. 18 UTC DTOPS guidance, which did well predicting
Erin's rapid intensification period earlier this year, is now
indicating a 62 to 76 percent chance of a 30 kt increase in
intensity over the next 24 h. Thus, I see no reason to not forecast
continued steady to rapid intensification over the next 24-36 h,
which is in line with the higher end of the intensity guidance, but
not as high as the most recent HAFS-A run. After 36 h, SHIPS
guidance shows southwesterly shear steadily increasing, and this
should lead to steady weakening through the end of the forecast
period. There is still some question as to Gabrielle's structure at
the end of the forecast and whether it will be losing tropical
characteristics. The southward shift in the forecast track suggests
it might hang on to tropical characteristics a little longer than
originally expected. The intensity forecast falls back close to the
IVCN and HCCA consensus aids by the end of the forecast period.
KEY MESSAGES:
1. Gabrielle is now a hurricane, but is still expected to pass east
of Bermuda on Monday. While the chances of impacts are still
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 now reaching the east
coast of the United States from North Carolina northward, as well as
Atlantic Canada, and should continue 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 21/2100Z 28.5N 61.7W 65 KT 75 MPH
12H 22/0600Z 29.7N 62.2W 80 KT 90 MPH
24H 22/1800Z 31.2N 62.0W 95 KT 110 MPH
36H 23/0600Z 32.7N 60.6W 100 KT 115 MPH
48H 23/1800Z 34.2N 57.7W 90 KT 105 MPH
60H 24/0600Z 35.2N 53.4W 80 KT 90 MPH
72H 24/1800Z 35.8N 47.6W 70 KT 80 MPH
96H 25/1800Z 37.5N 36.0W 60 KT 70 MPH
120H 26/1800Z 41.5N 25.1W 55 KT 65 MPH
$$
Forecaster Papin
Hurricane Gabrielle Advisory Number 19
NWS National Hurricane Center Miami FL AL072025
500 PM AST Sun Sep 21 2025
...GABRIELLE BECOMES A HURRICANE...
SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...28.5N 61.7W
ABOUT 320 MI...515 KM SE OF BERMUDA
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...992 MB...29.30 INCHES
Hurricane Gabrielle Discussion Number 19
NWS National Hurricane Center Miami FL AL072025
500 PM AST Sun Sep 21 2025
We are fortunate to have three NOAA aircraft (two P3's and one G-IV)
which are conducting research missions into Gabrielle this
afternoon. The data they have provided has been valuable, showing
the storm has become better aligned in the low to mid-levels
compared to this morning, though the eyewall structure has been
coming and going due to occasional dry air mixing out near the
cyclone's core. The highest 750 mb flight-level winds were up to 70
kt, which using a typical 0.85 reduction supports 60 kt. However,
the Tail Doppler Radar (TDR) on board one of the NOAA-P3 aircraft
showed a swath of 0.5 km winds up to 79 kt in the eastern semicircle
at 1741 UTC. Using a more conservative 0.80 reduction factor
for this level supports an intensity of 65 kt, and Gabrielle has
become a hurricane.
Recon fixes this afternoon show that the hurricane is beginning to
turn more north-northwest, with the estimated motion now at
330/9-kt. The track reasoning in the short-term remains the same as
this morning, with Gabrielle rounding the western edge of the
subtropical ridge, which should allow the hurricane to turn
northward and then northeastward over the next couple of days. There
was another small adjustment west in the track over the next 24 h,
but this still keeps Gabrielle's wind field well to the east of
Bermuda when it passes its latitude towards the end of the day
Monday. Thereafter, the hurricane should begin to gradually
accelerate in the westerly flow around the north side of the
aforementioned ridge. The biggest change in the track forecast
towards the end of the period is that the guidance continues to
shift a little more southward, especially the most recent 12 UTC
ECMWF, which shifted closer to the Azores in 4-5 days. For now,
the NHC track forecast will only be shifted a little southward this
cycle, choosing to stay closer to the reliable consensus aids TVCN
and HCCA, though it's possible some southward adjustments will
be needed in subsequent forecasts.
While the structure of Gabrielle on geostationary satellite is still
a little ragged with warmer cloud tops than this morning, it has
become more axis-symmetric, and a recent AMSR2 microwave pass at
1733 UTC indicates a thicker 37-GHz cyan ring than the one observed
this morning. 18 UTC DTOPS guidance, which did well predicting
Erin's rapid intensification period earlier this year, is now
indicating a 62 to 76 percent chance of a 30 kt increase in
intensity over the next 24 h. Thus, I see no reason to not forecast
continued steady to rapid intensification over the next 24-36 h,
which is in line with the higher end of the intensity guidance, but
not as high as the most recent HAFS-A run. After 36 h, SHIPS
guidance shows southwesterly shear steadily increasing, and this
should lead to steady weakening through the end of the forecast
period. There is still some question as to Gabrielle's structure at
the end of the forecast and whether it will be losing tropical
characteristics. The southward shift in the forecast track suggests
it might hang on to tropical characteristics a little longer than
originally expected. The intensity forecast falls back close to the
IVCN and HCCA consensus aids by the end of the forecast period.
KEY MESSAGES:
1. Gabrielle is now a hurricane, but is still expected to pass east
of Bermuda on Monday. While the chances of impacts are still
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 now reaching the east
coast of the United States from North Carolina northward, as well as
Atlantic Canada, and should continue 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 21/2100Z 28.5N 61.7W 65 KT 75 MPH
12H 22/0600Z 29.7N 62.2W 80 KT 90 MPH
24H 22/1800Z 31.2N 62.0W 95 KT 110 MPH
36H 23/0600Z 32.7N 60.6W 100 KT 115 MPH
48H 23/1800Z 34.2N 57.7W 90 KT 105 MPH
60H 24/0600Z 35.2N 53.4W 80 KT 90 MPH
72H 24/1800Z 35.8N 47.6W 70 KT 80 MPH
96H 25/1800Z 37.5N 36.0W 60 KT 70 MPH
120H 26/1800Z 41.5N 25.1W 55 KT 65 MPH
$$
Forecaster Papin
