Tropical Storm Danny was a weak and short-lived

tropical cyclone A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...

that caused minor damage to the U.S. states of

South Carolina South Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders North Carolina to the north and northeast, the Atlantic Ocean to the southeast, and Georgia (U.S. state), Georg ...

and

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

. The fourth named storm of the

2021 Atlantic hurricane season The 2021 Atlantic hurricane season was the third-most active Atlantic hurricane season on record in terms of number of tropical cyclones, although many of them were weak and short-lived. With 21 named storms forming, it became the sec ...

, the system formed from an area of low-pressure that developed from an upper-level

trough Trough may refer to: In science * Trough (geology), a long depression less steep than a trench * Trough (meteorology), an elongated region of low atmospheric pressure * Trough (physics), the lowest point on a wave * Trough level (medicine), the l ...

over the central

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

on June 22. Moving west-northwestward, the disturbance gradually developed as

convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...

, or showers and thunderstorms, increased over it. Although it was moving over the warm

Gulf Stream The Gulf Stream is a warm and swift Atlantic ocean current that originates in the Gulf of Mexico and flows through the Straits of Florida and up the eastern coastline of the United States, then veers east near 36°N latitude (North Carolin ...

, the organization of the disturbance was hindered by strong upper-level

wind shear Wind shear (; also written windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical ...

. By 18:00 UTC of June 27, as satellite images showed a well-defined center and thunderstorms, the system was upgraded to a tropical depression by the

National Hurricane Center The National Hurricane Center (NHC) is the division of the United States' NOAA/National Weather Service responsible for tracking and predicting tropical weather systems between the IERS Reference Meridian, Prime Meridian and the 140th meridian ...

(NHC). At 06:00 UTC on the next day, the system further strengthened into ''Tropical Storm Danny'' east-southeast of

Charleston, South Carolina Charleston is the List of municipalities in South Carolina, most populous city in the U.S. state of South Carolina. The city lies just south of the geographical midpoint of South Carolina's coastline on Charleston Harbor, an inlet of the Atla ...

. Danny continued its track towards South Carolina while slowly strengthening, subsequently reaching its peak intensity at that day of and a minimum central pressure of at 18:00 UTC. Danny then made

landfall Landfall is the event of a storm moving over land after being over water. More broadly, and in relation to human travel, it refers to 'the first land that is reached or seen at the end of a journey across the sea or through the air, or the fact ...

in Pritchards Island, north of Hilton Head, in a slightly weakened state at 23:20 UTC on the same day, with winds of and indicating that Danny weakened prior to moving inland. The system then quickly weakened to a tropical depression over east-central Georgia, before dissipating shortly afterward. Danny was one of three systems to make landfall on the U.S. state of South Carolina in the month of June, the others being Hurricane One in 1867 and Tropical Depression One in

1979 Events January * January 1 ** United Nations Secretary-General Kurt Waldheim heralds the start of the ''International Year of the Child''. Many musicians donate to the ''Music for UNICEF Concert'' fund, among them ABBA, who write the song ...

. Heavy rainfall was recorded in some portions of Georgia and South Carolina, causing minor flooding. In addition to flooding, impacts were also limited to some fallen trees and lightning strikes. Ten rescues were required on two different beaches on

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

due to rip currents. No deaths were reported due to Danny, and the damage from it in the Southeastern United States totaled $5,000 (2021 USD).

Meteorological history

On June 22, an upper-level trough separated from the

jet stream Jet streams are fast flowing, narrow thermal wind, air currents in the Earth's Atmosphere of Earth, atmosphere. The main jet streams are located near the altitude of the tropopause and are westerly winds, flowing west to east around the gl ...

and evolved into an upper-level

low-pressure system In meteorology, a low-pressure area (LPA), low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. It is the opposite of a high-pressure area. Low-pressure areas are commonly associated with inclem ...

. Two days later, the low-pressure area turned westward under the influence of a strong

ridge A ridge is a long, narrow, elevated geomorphologic landform, structural feature, or a combination of both separated from the surrounding terrain by steep sides. The sides of a ridge slope away from a narrow top, the crest or ridgecrest, wi ...

to its north. Disorganized convection, or showers and thunderstorms, increased as the system moved over warmer waters. Near this time, a surface trough in relation to the upper-level low became better defined. Over the next few days, the trough moved west-northwestward, and on June 26, the

(NHC) began to monitor the disturbance for development as it passed several hundred miles south of

Bermuda Bermuda is a British Overseas Territories, British Overseas Territory in the Atlantic Ocean, North Atlantic Ocean. The closest land outside the territory is in the American state of North Carolina, about to the west-northwest. Bermuda is an ...

. On June 27, ship observations,

buoy A buoy (; ) is a buoyancy, floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents. History The ultimate origin of buoys is unknown, but by 1295 a seaman's manual referred to navig ...

, and

satellite imagery Satellite images (also Earth observation imagery, spaceborne photography, or simply satellite photo) are images of Earth collected by imaging satellites operated by governments and businesses around the world. Satellite imaging companies sell im ...

revealed that a small area of low pressure had developed about east-southeast of the

border. Surface

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

decreased, and over the next 12 hours, the system continued to organize. At 18:00 UTC on June 27, the disturbance consolidated into a tropical depression, but operationally, the NHC did not upgrade the system to a tropical depression until 15:00 UTC on June 28, while it was located offshore South Carolina. A short time after formation, convection over the system decreased, and low-level circulation center (LLCC) became partially exposed. Convection remained displaced to the northwest of the center due to strong upper-level wind shear. Nevertheless, an advanced

scatterometer A scatterometer or diffusionmeter is a scientific instrument to measure the return of a beam of light or radar waves scattered by diffusion in a medium such as air. Diffusionmeters using visible light are found in airports or along roads to measur ...

pass discovered peak winds of – tropical storm-force – early on June 28. The NHC estimated that the depression strengthened into a tropical storm at 06:00 UTC that day, receiving the name ''Danny''. On the morning of June 28, the cloud structure of the cyclone continued to consolidate, sporting deep convection with cloud top temperatures of on its western periphery. Later, in the afternoon, a mass of deep convection quickly expanded over Danny's center. A

U.S. Air Force The United States Air Force (USAF) is the air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its origins to 1 ...

Hurricane Hunter reconnaissance aircraft found

gale-force The Beaufort scale ( ) is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale. It was devised in 1805 by Francis Beaufort a Hydrography, hydrographer in the Roy ...

surface winds of , and

NEXRAD NEXRAD or Nexrad (Next-Generation Radar) is a network of 159 high-resolution S-band pulse-Doppler radar, Doppler weather radars operated by the National Weather Service (NWS), an agency of the National Oceanic and Atmospheric Administration (NOAA) ...

radar in Charleston also found data supporting this value. Thus, it is estimated that Danny reached its peak intensity with

maximum sustained winds The maximum sustained wind associated with a tropical cyclone is a common indicator of the intensity of the storm. Within a mature tropical cyclone, it is found within the eyewall at a certain distance from the center, known as the radius of ma ...

of and a minimum

barometric pressure Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1,013.2 ...

of at 18:00 UTC on July 28. Steadily maintaining its motion, Danny made landfall on Pritchards Island, South Carolina, north of

Hilton Head Island Hilton Head Island, often referred to as simply Hilton Head, is a Lowcountry resort town and barrier island in Beaufort County, South Carolina, United States. It is northeast of Savannah, Georgia (as the crow flies), and southwest of Charlesto ...

, as a minimal tropical storm at 23:20 UTC, with winds of . This indicated that the storm weakened slightly before moving inland. While moving ashore, a weather station at Folly Beach recorded a wind gust of 41 mph (66 kph) as Danny moved inland. Upon entering the east-central portion of Georgia, the system weakened to a tropical depression as evidenced by

Doppler weather radar A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly pu ...

velocity data and surface observations. The weakening tropical cyclone dissipated by 06:00 UTC on July 29.

Preparations and impact

Danny's

tropical cyclogenesis Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropics, tropical cyclogenesis occur are distinctly different from those through which temperate cyclogenesis occu ...

was poorly forecast due to the disorganized nature of the precursor disturbance and low

model A model is an informative representation of an object, person, or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin , . Models can be divided in ...

confidence. This resulted in

tropical cyclone watches and warnings Tropical cyclone warnings and watches are alerts issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of tropical storm or hurricane intensity. They are notices to the local pop ...

occurring only 12 hours before landfall. A Tropical Storm Warning was issued from Edisto Beach to

Santee River } The Santee River is a river in South Carolina in the United States, and is long. The Santee and its tributaries provide the principal drainage for the coastal areas of southeastern South Carolina and navigation for the central coastal plain of ...

in South Carolina at 15:00 UTC on June 28. The warnings in the state from Danny were canceled at 03:00 UTC on June 29 as the system weakened to a tropical depression, inland Georgia. The

Storm Prediction Center The Storm Prediction Center (SPC) is a US government agency that is part of the National Centers for Environmental Prediction (NCEP), operating under the control of the National Weather Service (NWS), which in turn is part of the National Oceani ...

, in anticipation of Danny, also published a marginal risk of severe weather on the state on June 29, along with a 2 percent tornado risk. As the system moved inland, Lake Wind Advisories were also issued on portions of the South Carolina Midlands on the same day. Despite Danny being predicted not to bring any major impacts to the

Southeastern United States The Southeastern United States, also known as the American Southeast or simply the Southeast, is a geographical List of regions in the United States, region of the United States located in the eastern portion of the Southern United States and t ...

, portions of Georgia, South Carolina, and northern

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

were expected to see increased rainfall from the system, causing the potential of

flash flood A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice and snow. Flash f ...

ing. Double red flags were placed on

Myrtle Beach, South Carolina Myrtle Beach is a resort city on the East Coast of the United States in Horry County, South Carolina. It is located in the center of a long and continuous stretch of beach known as the "Grand Strand” in the northeastern part of the state. Its ...

to warn people that swimming in the area was prohibited, along with a high risk of rip currents from

Sumter Sumter may refer to: People Given name * Sumter S. Arnim (1904–1990), American dentist * Sumter de Leon Lowry Jr. (1893–1985), United States Army general Surname * Rowendy Sumter (born 1988), Curaçaoan footballer * Shavonda E. Sumt ...

to Charleston beaches. This, however, did not stop people from going to beaches. Danny was one of three systems to make landfall in South Carolina in the month of June, the others being an unnamed Category 1 hurricane in 1867 and an unnamed tropical depression in 1979. Palmetto Electric and

Dominion Energy Dominion Energy, Inc., commonly referred to as Dominion, is an American energy company headquartered in Richmond, Virginia that supplies electricity in parts of Virginia, North Carolina, and South Carolina and supplies natural gas to parts of Ut ...

both reported over 1,251 power outages in total in

Beaufort County, South Carolina Beaufort County ( ) is a county in the U.S. state of South Carolina. As of the 2020 census, its population was 187,117. Its county seat is Beaufort and its largest community is Hilton Head Island. Beaufort County is part of the Hilton Hea ...

. Lightning strikes were also observed in the state, along with minor flooding and heavy rainfall. A tree was downed in SC 170 and downed trees also occurred in

Savannah, Georgia Savannah ( ) is the oldest city in the U.S. state of Georgia (U.S. state), Georgia and the county seat of Chatham County, Georgia, Chatham County. Established in 1733 on the Savannah River, the city of Savannah became the Kingdom of Great Brita ...

. Minor flooding was reported in portions of

Jasper Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, is an opaque, impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to ...

and Horry Counties in South Carolina as well as

Chatham County, Georgia Chatham County ( ) is the easternmost county in the U.S. state of Georgia, on the state's Atlantic coast. The county seat and largest city is Savannah. One of the original counties of Georgia, Chatham County was created February 5, 1777, a ...

Purrysburg, South Carolina Purrysburg is an unincorporated community in Jasper County, South Carolina. While the town itself was abandoned, the settlers were successful. The town was located on the South Carolina bank of the Savannah River on 40,000 acres. Purrysburg (a ...

received the highest rainfall total from Danny, accumulating to . Ten rescues were required on Carolina Beach and Wrightsville Beach in North Carolina due to rip currents on June 28.

References

External links

* The NHC'
Advisory Archive on Tropical Storm Danny
{{DEFAULTSORT:Danny (2021) 2021 Atlantic hurricane season Atlantic tropical storms Tropical cyclones in 2021 Hurricanes in South Carolina Hurricanes in Georgia (U.S. state)

Meteorological history

Preparations and impact

See also

References

External links