Tropical Storm Mindy

Post Tropical Mindy Track 2300 Hours September 09 2021
Post Tropical Mindy Track 2300 Hours September 09 2021

Tropical Storm Mindy Wind Speed FieldTropical Storm MindyNWS National Hurricane Center Miami FL 1100 PM EDT Thu Sep 09, 2021 (see 11:00 video below)

The structure of Mindy this evening has become quite diffuse, with a linear band of convection mostly associated with a prominent outflow boundary emanating away from the system. The last-light visible low-level cloud motions gave the impression that Mindy was opening up into a trough, with southwesterly flow ahead and northeasterly flow immediately behind the estimated center. Indeed, a ASCAT-A pass valid at 0002 UTC suggested that Mindy no longer has closed cyclonic flow on its northeast side, with a lack of easterly wind vectors in this sector of the system. In addition, a rapidly advancing frontal boundary has already moved off of the Carolina coast and will soon be merging with the leftover vort-max associated with Mindy. The accumulation of all this evidence indicates that Mindy no longer meets the definition of a tropical cyclone, and this will be the final advisory on the system.

The post-tropical remains of Mindy have continued to accelerate to the east-northeast this evening at 070/25 kt, moving almost as quickly as the the maximum sustained winds, which is another reason why the circulation is likely no longer closed. This motion should continue for the next 12-24 hours with a gradual slowdown until what remains of the circulation becomes indistinguishable from the frontal boundary it is becoming embedded in.

FORECAST POSITIONS AND MAX WINDS

INIT  10/0300Z 32.5N  75.0W   30 KT  35 MPH - Post Tropical (ENE Charleston,SC)
 12H  10/1200Z 33.2N  71.6W   25 KT  30 MPH - Post Tropical (ESE Myrtle Beach,SC)
 24H  11/0000Z 34.1N  67.8W   25 KT  30 MPH - Post Tropical (WNW St. George's,Bermuda)
 36H  11/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM EDT Thu Sep 09, 2021 

Doppler radar data and surface observations show that the center of Mindy has recently moved offshore the coast of Georgia. Buoy 41008 located off the Georgia coast recently recorded 1-min sustained winds of 29 kt with gusts as high as 33 kt. Thus, 30 kt is maintained as the intensity for this advisory.

Mindy is located in an environment of strong south to southwesterly vertical wind shear. Over the next 24 h, the shear is expected to become even stronger. The strong shear should prevent restrengthening and is likely to strip away any remaining convection by Friday or Friday night. Mindy is forecast to become post-tropical Friday evening. Most of the global models suggest that the cyclone will open up into a trough in 36-48 h, but it is possible this could happen sooner, as surface observations already show that easterly winds on the north side have become quite weak. The NHC forecast calls for dissipation Friday night, which is sooner than the previous advisory.

Mindy continues moving quickly to the east-northeast or 065/18 kt. There has been no change to the track forecast philosophy. Mindy is forecast to continue moving east-northeastward at a similar speed for the next 24 h near the southern portion of a deep-layer trough moving across the eastern United States. Once the trough begins to lift northeastward, Mindy should slow down a little on Friday. The main adjustment to the NHC track is to show a slightly faster motion toward the east-northeast at the 24-36 h points.

Key Messages:

  • 1. Mindy will produce locally heavy rainfall across portions of coastal South Carolina through early this afternoon. This rainfall may produce isolated to scattered flash, urban, and small stream flooding.
FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 31.5N  80.7W   30 KT  35 MPH - Depression (ENE Sapelo Island,GA)
 12H  10/0000Z 32.5N  77.5W   30 KT  35 MPH - Depression (ESE Charleston,SC)
 24H  10/1200Z 33.6N  73.4W   30 KT  35 MPH - Depression (ESE Myrtle Beach,SC)
 36H  11/0000Z 34.3N  70.3W   25 KT  30 MPH - Post Tropical (WNW St. George's,Bermuda)
 48H  11/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 PM EDT Wed Sep 08, 2021

Doppler radar data and surface observations indicate that the center of Mindy made landfall over St. Vincent Island, Florida, near 0115 UTC. Since that time, the center has been moving along the shoreline of Apalachee Bay. The intensity is held at 40 kt based on continuity from earlier buoy data and a 43-kt wind at an elevated tower south of Apalachicola. The central pressure has been lowered to 1002 mb based on surface obs from the Apalachicola area. It should be noted that while Mindy is not well organized in satellite imagery, but it has a good radar presentation. The initial motion is 055/17. A general east-northeastward motion should continue for the next 24 h or so as Mindy moves along the southern edge of a deep-layer mid-latitude trough moving across the eastern United States. After that, a decrease in forward speed and a more eastward motion are expected as the aforementioned trough moves away from Mindy and the cyclone becomes vertically shallow. The forecast track keeps the center along the Gulf coast for a few more hours, followed by a motion across northern Florida and southeastern Georgia into the Atlantic. The new forecast track is a little faster than the previous forecast.

Little change in strength is likely during the next few hours while the center of Mindy straddles the coast. Weakening should occur as the center moves farther inland later tonight, aided by an increase in westerly vertical wind shear. By the time the cyclone reaches the Atlantic, the shear should be strong enough to make the system continue to weaken. The new intensity forecast is a little stronger than the previous forecast during the first 12 h, then is similar to the previous forecast in calling for the cyclone to dissipate after 72 h.

Key Messages:

  • 1. Tropical Storm Mindy is expected to produce heavy rainfall from the Florida Panhandle into southern portions of Georgia and South Carolina through Thursday morning. This rainfall may produce isolated to scattered flash, urban, and small stream flooding.
  • 2. Tropical storm conditions are expected through tonight in portions of the Florida Panhandle where a Tropical Storm Warning is in effect. Tropical storm conditions are also possible across portions of the northern Florida Peninsula and southeastern Georgia near the center of Mindy.
FORECAST POSITIONS AND MAX WINDS

INIT  09/0300Z 29.9N  84.5W   40 KT  45 MPH - Tropical Storm (WSW St Teresa,FL)
 12H  09/1200Z 31.0N  81.8W   35 KT  40 MPH - Tropical Storm (WNW Hopewell,GA)
 24H  10/0000Z 32.2N  77.7W   30 KT  35 MPH - Depression (ESE Charleston,SC)
 36H  10/1200Z 33.1N  73.7W   30 KT  35 MPH - Depression (ESE Murrells Inlet,SC)
 48H  11/0000Z 33.7N  70.7W   30 KT  35 MPH - Depression (WNW St. George's,Bermuda)
 60H  11/1200Z 34.1N  68.5W   25 KT  30 MPH - Post Tropical (WNW St. George's,Bermuda)
 72H  12/0000Z 34.3N  66.3W   25 KT  30 MPH - Post Tropical (WNW St. George's,Bermuda)
 96H  13/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 400 PM CDT Wed Sep 08, 2021

Through the day, the area of disturbed weather in the northeastern Gulf of Mexico has gradually become better organized on geostationary satellite and Doppler radar imagery. Earlier, a 1515 UTC ASCAT-C pass found a number of southwesterly wind retrievals in the 30-kt range on the southeast side of the formative circulation. The ASCAT-C Ambiguities at that time also hinted that a very small closed circulation was trying to develop along the edge of these stronger winds. Since that time, a well-defined circulation become evident on KEVX Doppler-radar with inbound velocities occasionally nearing 40-45 kt to the southeast of the radar center. These Doppler-radar winds have been increasing over the past couple of hours as the center moves closer to the radar and I am reasonably confident this circulation is now surface based. Just in the last hour or so, NOAA buoy 42039 reported a peak 1-minute sustained wind of 35 kt just southeast of the center, confirming the system now has tropical storm force winds. Thus, advisories are being initiated on tropical storm Mindy with maximum sustained wind of 35 kt.

The most recent estimated motion following the center on radar is to the northeast at 050/18 kt. The track guidance is in good agreement that this quick motion should continue with a gentle shift to the east-northeast in the next 24-36 hours as the system is under the influence of a deep-layer mid-latitude trough moving across the eastern United States. On the current heading, the center of Mindy should move inland over the Florida Panhandle in the next 6-12 hours and then already be offshore of the southeastern United States by 24 hours. A gradual slowdown is expected thereafter as the cyclone is left behind by this mid-latitude trough and also becomes vertically shallow.

Little intensification is expected prior to landfall, with land interaction resulting in Mindy weakening back to a depression by 24 hours. Conditions do not appear favorable for restrengthening off the southeastern United States as shear is forecast to increase above 30 knots in 24 hours. This shear will likely strip away from remaining convection, and both the ECMWF and GFS simulated IR brightness temperatures suggest Mindy should become a remnant low in the day 2-3 period. This remnant low is forecast to open up into a trough shortly thereafter.

Key Messages:

  • 1. Mindy is expected to produce heavy rainfall from the Florida Panhandle into southern portions of Georgia and South Carolina through Thursday morning. This rainfall may produce isolated to scattered flash, urban, and small stream flooding.
  • 2. Tropical storm conditions are expected through tonight in portions of the Florida Panhandle where a Tropical Storm Warning is in effect.
FORECAST POSITIONS AND MAX WINDS

INIT  08/2100Z 29.0N  86.3W   35 KT  40 MPH - Tropical Storm (WSW Cape San Blas,FL)
 12H  09/0600Z 30.3N  84.1W   35 KT  40 MPH - Tropical Storm (WSW Cody,FL)
 24H  09/1800Z 31.3N  80.0W   30 KT  35 MPH - Depression (ESE Sapelo Island,GA)
 36H  10/0600Z 32.3N  75.6W   30 KT  35 MPH - Depression (ESE Charleston,SC)
 48H  10/1800Z 32.9N  72.7W   30 KT  35 MPH - Depression (ESE Charleston,SC)
 60H  11/0600Z 33.4N  69.6W   25 KT  30 MPH - Post Tropical (WNW St. George's,Bermuda)
 72H  11/1800Z 33.3N  68.5W   25 KT  30 MPH - Post Tropical (WNW St. George's,Bermuda)
 96H  12/1800Z...DISSIPATED

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Video: Tropics update: Hurricane Larry, Tropical Depression Mindy and 2 tropical waves