FLORIDA
STORMS
Tropical Depression Eleven
LOCATED
1320 MI W OF THE AZORES
WINDS
35 MPH
PRESSURE
1010 MB
MOVING
NE AT 12 MPH
From the National Hurricane Center at 1100 PM AST Sat Aug 28 2021
New tropical depression forms over the subtropical central Atlantic.
TAP LINKS BELOW TO FOCUS
Alerts
hazards
summary
DISCUSSION

There are no coastal watches or warnings in effect.

There are no coastal watches or warnings in effect.

None.

None.

At 1100 PM AST (0300 UTC), the center of Tropical Depression Eleven was located near latitude 33.0 North, longitude 49.7 West. The depression is moving toward the northeast near 12 mph (19 km/h). A faster northeastward motion is expected through Monday. Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Gradual strengthening is expected through Sunday, and the depression is expected to strengthen to a tropical storm later tonight or tomorrow. The system is then forecast to become extratropical by Monday. The estimated minimum central pressure is 1010 mb (29.83 inches).

At 1100 PM AST (0300 UTC), the center of Tropical Depression Eleven was located near latitude 33.0 North, longitude 49.7 West. The depression is moving toward the northeast near 12 mph (19 km/h). A faster northeastward motion is expected through Monday. Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Gradual strengthening is expected through Sunday, and the depression is expected to strengthen to a tropical storm later tonight or tomorrow. The system is then forecast to become extratropical by Monday. The estimated minimum central pressure is 1010 mb (29.83 inches).

Before sunset this evening, visible satellite images showed that a well-defined low level circulation was developing in association with the disturbance over the subtropical central Atlantic. However, up until a couple of hours ago, the system lacked sufficient organized deep convection to be considered a tropical cyclone by definition. Since that time, a deep convective burst has increased in size near, and to the east of the estimated center. In addition, a curved band has begun to develop over the southeastern portion of the circulation. Based on this increase in convective organization, advisories are being initiated on Tropical Depression Eleven. There was no ASCAT data this evening over the cyclone, so the initial intensity of 30 kt is based on the latest Dvorak CI number from TAFB.

The initial motion of the depression is 050/10 kt. The cyclone is embedded in southwesterly flow to the southeast of a mid- to upper-level trough and an associated cold front. This flow is forecast to increase as the cold front approaches the cyclone, resulting in the system accelerating northeastward over the next day or so. Once the cyclone interacts with this frontal boundary in a couple of days, a turn to the north is expected. The model guidance is in very good agreement on this scenario, and the NHC track forecast lies in the middle of the consensus tracks.

Baroclinic forcing and upper-level diffluence should aid in intensifying the depression over the next 24 h, despite increasing shear. By 36 h, the combination of interaction with the cold front and passage over much cooler waters should result in extratropical transition. The system is then forecast to become absorbed by a larger low pressure system by midweek. The NHC intensity forecast is near the various multi-model consensus solutions.

The depression continues to slowly organize this morning, with a distinct curved band stretching along the southeastern quadrant of the low-level circulation. However, the deep convection that was closer to the center earlier has recently been sheared off to the northeast due to increasing southwesterly vertical wind shear. The latest subjective Dvorak estimates from TAFB and SAB were T2.0/30 kt and T1.5/25 kt respectively. The latest objective ADT guidance was a bit higher at T2.4/34 kt. Taking a blend of these estimates, the intensity was held at 30 kt for this advisory, though the depression appears close to becoming a tropical storm.

The depression is beginning to gradually accelerate, with the estimated motion now at 050/13 kt. A strong deep-layer trough will continue to steer the depression to the northeast in the short-term with increasing forward motion. After the system becomes a post-tropical cyclone, it is forecast to gradually pivot to the north and then northwest before dissipating in 72 hours. The latest NHC track forecast is a touch faster than the previous one, following the latest consensus track guidance.

While vertical wind shear is expected to increase quite dramatically over the next 24-36 hours, strong baroclinic forcing should offset this negative factor and allow at least steady intensification in the short term especially as the cyclone accelerates. After 24 hours, the system will be crossing into much cooler sea-surface temperatures, and extratropical transition will likely be ongoing as the system merges with an advancing frontal boundary. The latest NHC intensity forecast follows the HCCA consensus aid closely, and is just a bit stronger in the short-term helped by the fast forward motion, with a peak intensity of 50-kt just before extratropical transition occurs.

Before sunset this evening, visible satellite images showed that a well-defined low level circulation was developing in association with the disturbance over the subtropical central Atlantic. However, up until a couple of hours ago, the system lacked sufficient organized deep convection to be considered a tropical cyclone by definition. Since that time, a deep convective burst has increased in size near, and to the east of the estimated center. In addition, a curved band has begun to develop over the southeastern portion of the circulation. Based on this increase in convective organization, advisories are being initiated on Tropical Depression Eleven. There was no ASCAT data this evening over the cyclone, so the initial intensity of 30 kt is based on the latest Dvorak CI number from TAFB.

The initial motion of the depression is 050/10 kt. The cyclone is embedded in southwesterly flow to the southeast of a mid- to upper-level trough and an associated cold front. This flow is forecast to increase as the cold front approaches the cyclone, resulting in the system accelerating northeastward over the next day or so. Once the cyclone interacts with this frontal boundary in a couple of days, a turn to the north is expected. The model guidance is in very good agreement on this scenario, and the NHC track forecast lies in the middle of the consensus tracks.

Baroclinic forcing and upper-level diffluence should aid in intensifying the depression over the next 24 h, despite increasing shear. By 36 h, the combination of interaction with the cold front and passage over much cooler waters should result in extratropical transition. The system is then forecast to become absorbed by a larger low pressure system by midweek. The NHC intensity forecast is near the various multi-model consensus solutions.

The depression continues to slowly organize this morning, with a distinct curved band stretching along the southeastern quadrant of the low-level circulation. However, the deep convection that was closer to the center earlier has recently been sheared off to the northeast due to increasing southwesterly vertical wind shear. The latest subjective Dvorak estimates from TAFB and SAB were T2.0/30 kt and T1.5/25 kt respectively. The latest objective ADT guidance was a bit higher at T2.4/34 kt. Taking a blend of these estimates, the intensity was held at 30 kt for this advisory, though the depression appears close to becoming a tropical storm.

The depression is beginning to gradually accelerate, with the estimated motion now at 050/13 kt. A strong deep-layer trough will continue to steer the depression to the northeast in the short-term with increasing forward motion. After the system becomes a post-tropical cyclone, it is forecast to gradually pivot to the north and then northwest before dissipating in 72 hours. The latest NHC track forecast is a touch faster than the previous one, following the latest consensus track guidance.

While vertical wind shear is expected to increase quite dramatically over the next 24-36 hours, strong baroclinic forcing should offset this negative factor and allow at least steady intensification in the short term especially as the cyclone accelerates. After 24 hours, the system will be crossing into much cooler sea-surface temperatures, and extratropical transition will likely be ongoing as the system merges with an advancing frontal boundary. The latest NHC intensity forecast follows the HCCA consensus aid closely, and is just a bit stronger in the short-term helped by the fast forward motion, with a peak intensity of 50-kt just before extratropical transition occurs.

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