Tropical Storm Danny

Tropical Storm Danny Track 0500 Hours June 29 2021
Tropical Storm Danny Track 0500 Hours June 29 2021

Tropical Storm Danny Wind Speed FieldTropical Storm DannyNWS National Hurricane Center Miami FL 500 AM EDT Tue Jun 29, 2021 (see Tuesday video below)

Surface observations indicate that the low-level circulation associated with Danny is no longer well-defined. Therefore, Danny is no longer classifiable as a tropical cyclone. The observations also indicated that the maximum winds associated with these remnants have decreased to 20 kt or less, while surface pressures have risen to 1019 mb. The remnants of Danny are moving west-northwestward at about 15 kt and this general motion is expected to continue through today, with locally heavy rainfall spreading across portions of northern Georgia and Alabama. This is the last NHC advisory on Danny. For additional information specific to your area, please refer to products issued by your local National Weather Service Forecast Office.

Key Messages:

  • 1. Heavy rainfall from the remnants of Danny may produce isolated flash flooding, especially in urban areas, across western and northern Georgia into central and northern Alabama today.
FORECAST POSITIONS AND MAX WINDS

INIT  29/0900Z 33.0N  83.0W   20 KT  25 MPH - Post Tropical (WSW  Deepstep, GA)
 12H  29/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM EDT Mon Jun 28, 2021

Deep convection has exploded this afternoon over the center of what is now Tropical Storm Danny. Reconnaissance aircraft measured 49 kt winds at the 850-mb fight-level, which equals roughly a 39-kt surface wind. In addition, Doppler velocity data from the Charleston radar measured average velocities of 49 kt at 6000-7000 ft, which also equate to about 40-kt surface winds. A reconnaissance aircraft dropsonde also measured a central pressure of 1009 mb. Based on these data, the advisory intensity has been increased to 40 kt.

The initial motion estimate is 290/14 kt. Tiny Danny is forecast to maintain a west-northwestward motion for the next day or so, with landfall expected along the southern coast of South Carolina likely occurring by 0000 UTC this evening. The small tropical cyclone should continue to move inland across southern South Carolina and eastern Georgia tonight and early Tuesday, with dissipation expected over the mountains of northern Georgia by Tuesday night or early Wednesday. The new NHC track forecast is a little to the left of the previous advisory track, and lies close to the consensus track models HCCA, TVCA, and GFEX.

No additional strengthening is anticipated before Danny makes landfall. Rapid weakening should commence shortly after landfall, with Danny likely becoming a remnant low by Tuesday morning. The official intensity forecast follows a blend for the Decay-SHIPS statistical model for inland tropical cyclones, and the intensity consensus models IVCN and HCCA.

Key Messages:

  • 1. Heavy rainfall is possible from coastal southern South Carolina and Georgia, inland across the Piedmont of Georgia into northeast Alabama. Isolated flooding is possible across urban areas of the southern South Carolina and Georgia coasts.
  • 2. Tropical-storm-force winds are expected across portions of the South Carolina coast late this afternoon and tonight where a Tropical Storm Warning is in effect.
  • 3. Swells generated by Tropical Storm Danny are expected to affect portions of the South Carolina coast through tonight. These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS

INIT  28/2100Z 32.3N  80.1W   40 KT  45 MPH - Tropical Storm (Pritchards Island, SC)
 12H  29/0600Z 33.2N  82.4W   25 KT  30 MPH - Post Tropical (WSW Wrens, GA)
 24H  29/1800Z 34.3N  85.2W   15 KT  15 MPH - Post Tropical (WNW Rome, GA)
 36H  30/0600Z...DISSIPATED INLAND

NWS National Hurricane Center Miami FL 1100 AM EDT Mon Jun 28, 2021

The area of disturbed weather and associated low-pressure system that the NHC has been tracking the past couple of days has developed into a tropical depression off the coast of South Carolina this morning. The inner-core cloud structure noted in high-resolution visible satellite imagery has continued to tighten up and deep convection with cloud top temperatures of -60 deg C have persisted northwest through southwest of the center, yielding a Dvorak shear pattern intensity estimate of 30 kt. This intensity estimate is consistent with overnight scatterometer surface wind data of 31-32 kt just north of the well-defined center.

The initial motion estimate is 300/14 kt. The small tropical cyclone is expected to maintain a west-northwestward to northwestward motion for the next couple of days, resulting in landfall along the south-central coast of South Carolina later this evening. The small cyclone is expected to dissipate by 48 hours, if not sooner, when the system will be located over the southern Appalachian Mountains. The NHC track forecast lies close to the tightly packed GFS- and ECMWF-based Beta-Advection models due to the lack of any significant inner-core convection, which is allowing the cyclone to be steered more by the low-level flow rather than the deep-layer flow as depicted by the global and regional models.

There is a narrow window of opportunity this afternoon for the depression to strengthen into a tropical storm before landfall occurs. During the next few hours, the small cyclone will be passing over the warmer Gulf Stream where sea-surface temperatures are around 28 deg C. In addition, as the outer wind field begins to interact with land, low-level frictional convergence along and just offshore should help to generate deep convection just prior to landfall, helping to spin up the wind field. The NHC forecast shows the system becoming a tropical storm before landfall, and as a result a tropical storm warning has been issued for a portion of the South Carolina coast.

An Air Force Reserve Unit reconnaissance aircraft will investigate the system this afternoon beginning around 1800 UTC, providing more detailed information on the cyclone’s intensity.

Key Messages:

  • 1. Heavy rainfall is possible from coastal southern South Carolina and Georgia, inland across the Piedmont of Georgia into northeast Alabama. Isolated flooding is possible across urban areas of the southern South Carolina and Georgia coasts.
  • 2. Tropical-storm-force winds are expected across portions of the South Carolina coast late this afternoon and tonight where a Tropical Storm Warning is in effect.
  • 3. Swells generated by the depression are expected to affect portions of the South Carolina coast this afternoon and tonight. These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS

INIT  28/1500Z 31.9N  78.3W   30 KT  35 MPH - Depression (ESE Charleston, SC)
 12H  29/0000Z 32.8N  80.6W   35 KT  40 MPH - Tropical Storm (ENE Ritter, SC)
 24H  29/1200Z 34.2N  83.3W   20 KT  25 MPH - Low (WNW Ila, GA)
 36H  30/0000Z 35.2N  85.6W   15 KT  15 MPH - Low (WNW Whitwell, TN)
 48H  30/1200Z...DISSIPATED INLAND

NWS National Hurricane Center Miami FL 800 AM EDT Mon Jun 28, 2021

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. A well-defined low pressure system located about 190 miles east-southeast of Hilton Head Island, South Carolina, is producing a large area of showers and thunderstorms mainly west of the center. However, any additional increase in organization of the thunderstorm activity would result in the issuance of advisories for a tropical depression or tropical storm later this morning or afternoon. The low is forecast to move west-northwestward at 15 to 20 mph, and the system should reach the coast of southern South Carolina or Georgia by this evening. If advisories are initiated, then tropical storm warnings could be required for a portion of the Georgia and South Carolina coasts with short notice. Regardless of development, a few inches of rain are possible along the immediate coasts of Georgia and southern South Carolina through Tuesday. An Air Force Reserve Unit reconnaissance aircraft is scheduled to investigate the system this afternoon. * Formation chance through 48 hours…high…70 percent. * Formation chance through 5 days…high…70 percent.
  • 2. A broad area of low pressure associated with a tropical wave is producing a small cluster of showers and thunderstorms over the central tropical Atlantic Ocean. Some slow development is possible through the end of the week while this system moves quickly westward to west-northwestward at about 20 mph, likely reaching the Lesser Antilles Wednesday night. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…medium…40 percent.

NWS National Hurricane Center Miami FL 800 PM EDT Sun Jun 27, 2021

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. A small low pressure system is located about 425 miles east-southeast of Savannah, Georgia. The associated shower and thunderstorm activity has become less organized since earlier this afternoon, becoming displaced to the northwest of the surface center due to strong upper-level winds. The low is forecast to move quickly west-northwestward at 15 to 20 mph, crossing over the warmer waters of the Gulf Stream Monday morning, and it has some potential to become a tropical depression or tropical storm before reaching the coast of Georgia or southern South Carolina by Monday evening. If the system becomes more organized overnight or on Monday, then tropical storm warnings could be required for a portion of the Georgia and South Carolina coasts with short notice. Regardless of development, a few inches of rain are possible along the immediate coasts of Georgia and southern South Carolina through Monday night. An Air Force Reserve Unit reconnaissance aircraft is scheduled to investigate the system Monday afternoon, if necessary. * Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…medium…50 percent.
  • 2. An area of low pressure associated with a tropical wave is producing a small cluster of showers and thunderstorms over the eastern tropical Atlantic Ocean. Some slow development is possible through the end of the week while this system moves quickly westward to west-northwestward at about 20 mph, likely reaching the Lesser Antilles late Wednesday or Wednesday night. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 200 PM EDT Sun Jun 27, 2021

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. Satellite imagery and nearby buoy and ship observations indicate that a small low-pressure system has formed about 500 miles east-southeast of the Georgia-South Carolina border. Surface pressures have begun to fall across the area, and showers and thunderstorms have recently become better organized. Some additional development of this system will be possible later today, and especially on Monday when the system will move across the warmer waters of the Gulf Stream, and a tropical depression could form before the system makes landfall along the southern U.S. coast. The low is expected to move westward today, and then west-northwestward at about 15 mph on Monday, reaching the coast of the southeastern United States by late Monday. An Air Force Reserve Unit reconnaissance aircraft is scheduled to investigate the system Monday afternoon, if necessary. * Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…medium...50 percent.
  • 2. An area of low pressure associated with a tropical wave located over the eastern tropical Atlantic Ocean more than 700 miles southwest of the Cabo Verde Islands is producing disorganized showers and thunderstorms. Little, if any, development of this system is expected for the next couple of days, followed by some gradual development by Wednesday and continuing through the end of the week while it moves it moves westward to west-northwestward at about 20 mph. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Sun Jun 27, 2021

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. An area of low pressure associated with a tropical wave located over the eastern tropical Atlantic Ocean more than 600 miles southwest of the Cabo Verde Islands is producing a small area of showers and thunderstorms. Some slow development of this system is possible through the middle of the week while it moves a little faster toward the west and then west-northwest at about 20 mph. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…30 percent.
  • 2. A surface trough interacting with an upper-level low is producing a broad area of disorganized showers and thunderstorms about 600 miles east-southeast of the Georgia coast. Surface pressures remain high across the area, and significant development of this system is not anticipated due to dry air and unfavorable upper-level winds. The disturbance is expected to move westward today, and then west-northwestward at about 15 mph on Monday, reaching the coast of the southeastern United States by late Monday. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…20 percent.

NWS National Hurricane Center Miami FL 800 PM EDT Sat Jun 26, 2021

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. A broad area of low pressure associated with a tropical wave located over the eastern tropical Atlantic Ocean several hundred miles southwest of the Cabo Verde Islands continues to produce disorganized shower and thunderstorm activity. Some slow development of this system is possible through the middle of next week while it moves a little faster toward the west and then west-northwest at about 20 mph. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…30 percent.
  • 2. A surface trough located a few hundred miles southwest of Bermuda is producing a broad area of disorganized showers and thunderstorms. Surface pressures are currently high across the area, and significant development of this system is not anticipated while it moves westward and then west-northwestward at about 15 mph over the next few days, reaching the coast of the southeastern United States late Monday.

NWS National Hurricane Center Miami FL 200 PM EDT Sat Jun 26, 2021

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. A tropical wave associated with a broad area of low pressure is located over the eastern tropical Atlantic Ocean about 400 miles south-southwest of the Cabo Verde Islands. Although shower and thunderstorm activity is currently disorganized, some slow development will be possible over the next several days while the disturbance moves generally westward at 15 to 20 mph. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…30 percent.
  • 2. A surface trough located a couple hundred miles south of Bermuda is producing a broad area of disorganized showers and thunderstorms. Although surface pressures are currently high across the area, some additional slow development could occur while the system moves westward at 10 to 15 mph over the next few days. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…10 percent.

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Video:Tropical Storm Danny brings rain