Tropical Depression One (2009)
Encyclopedia
Tropical Depression One was the first tropical cyclone
to develop during the 2009 Atlantic hurricane season
. Upon being declared a tropical depression on May 28, it marked the third time that a pre-season storm formed in three consecutive years. Originating from a disorganized area of low pressure
off the coast of North Carolina
, Tropical Depression One quickly developed over the Gulf stream
. After attaining winds of 35 mph (55 km/h) along with a minimum pressure of 1006 mbar (hPa; 29.71 inHg), the depression began to weaken due to increasing wind shear
and cooling sea surface temperature
s. During the afternoon of May 29, convection
associated with the system was significantly displaced from the center of circulation
; this led the National Hurricane Center to issue their final advisory on the depression as it had degenerated into a remnant-low pressure area
. As a tropical cyclone, Tropical Depression One had no effects on land; however, the precursor to the depression brought minor rainfall and light winds to parts of coastal North Carolina. Its track, formation, and timing were relatively similar to Tropical Storm One of the 1940 Atlantic hurricane season
.
stalled near The Bahamas
and slowly degenerated. On May 25, a shortwave trough
caused the northern portion of the system to move north of the Bahamas. The following day, an area of low pressure
developed along the boundary about 290 miles (465 km) south-southwest of Wilmington, North Carolina
. Tracking towards the north, the system became increasingly organized. On May 27, the National Hurricane Center
(NHC) began issuing Tropical Weather Outlooks for the low while it was located about 120 miles (195 kilometers) south of Cape Hatteras
, North Carolina
. An upper-level ridge
situated to the southeast of the system was steering it towards the northeast. The NHC issued their final outlook on the low around 8 pm EDT (0000 UTC on May 28) while the system was located about 90 mi (150 km) east of Cape Hatteras, North Carolina, as development of the low was not expected.
On May 28, the NHC once again initiated outlooks on the system as convection quickly redeveloped. Around 11:00 am EDT (1500 UTC), they designated the system as Tropical Depression One while it was located about 310 mi (500 km) south of Providence, Rhode Island
. Upon being classified, the depression exhibited deep convective activity, with the center of circulation
situated on the northwestern edge. The redevelopment of the system was the result of low wind shear
and warm waters, up to 26 °C (78.8 °F), from the Gulf Stream
. Later that day, convection began to diminish as the depression tracked into an area of progressively higher shear and cooler waters. By this time, the system was embedded within the westerlies
between a subtropical ridge
to the southeast and a trough
to the northwest. Around 7:30 pm EDT (2330 UTC), a QuickSCAT satellite pass over the depression found tropical storm-force winds; however, the winds were determined to have been affected by rain and therefore not representative of the depression's actual intensity. Following the satellite pass, the center of circulation became partially exposed to the northwest and the area of convection associated with the depression diminished in area.
Early on May 29, Tropical Depression One nearly attained tropical storm status, with intensity estimates using the Dvorak Technique
reaching T2.5, or 40 mph (65 km/h); however, the estimates were also as low as T1.5, leading to the intensity of the depression remaining at 35 mph (55 km/h). After a burst in convective activity overnight, shower and thunderstorm activity waned once more by 3:00 am EDT (0700 UTC). Situated at the edge of the Gulf Stream, intensification into a tropical storm was no longer anticipated. Later that morning, the center of circulation became fully exposed by strong wind shear; an approaching trough also began absorbing the small depression by this time. The remaining convection associated with the system was displaced to the southeast. With no convection developing around the depression, it degenerated into a remnant-low pressure area
during the afternoon of May 29. At 5:00 pm EDT (2100 UTC) the NHC issued their final advisory on Tropical Depression One. The remnants of the depression persisted until 2 am EDT (0600 UTC) on May 30, at which time it was absorbed by a warm front
, south of Nova Scotia
.
on May 27. Rainfall in Hatteras
amounted to 0.1 in (2.5 mm) on May 27; sustained wind reached 15 mph (24.1 km/h) and gusts were measured up to 23 mph (37 km/h). The lowest sea level pressure recorded in relation to the system was 1009 mbar
(hPa
; 29.81 inHg). Increased winds along coastal areas of the state was possible in relation to the outer edges of the depression. When Tropical Depression One formed on May 28, it marked the third time since 1851
, when reliable records in the Atlantic basin began, that a pre-season cyclone developed in three consecutive years, following Subtropical Storm Andrea
which formed in May of 2007
and Tropical Storm Arthur
in May of 2008
. The first occurrence of this was in 1932
, 1933
, and 1934
, and the second occurrence were the years of 1951
, 1952
, and 1953
. Tropical Depression One was also the farthest north a May tropical cyclone is known to have formed, according to the NHC's Tropical Cyclone Report.
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
to develop during the 2009 Atlantic hurricane season
2009 Atlantic hurricane season
The 2009 Atlantic hurricane season was a below-average year, unlike the 2009 Pacific hurricane season, which was above average, both due to a moderate El Niño. During this year, nine tropical storms formed, the fewest since the 1997 season.An average season has ten tropical storms, six hurricanes...
. Upon being declared a tropical depression on May 28, it marked the third time that a pre-season storm formed in three consecutive years. Originating from a disorganized area of low pressure
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
off the coast of North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
, Tropical Depression One quickly developed over the Gulf stream
Gulf Stream
The Gulf Stream, together with its northern extension towards Europe, the North Atlantic Drift, is a powerful, warm, and swift Atlantic ocean current that originates at the tip of Florida, and follows the eastern coastlines of the United States and Newfoundland before crossing the Atlantic Ocean...
. After attaining winds of 35 mph (55 km/h) along with a minimum pressure of 1006 mbar (hPa; 29.71 inHg), the depression began to weaken due to increasing wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
and cooling sea surface temperature
Sea surface temperature
Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a...
s. During the afternoon of May 29, convection
Atmospheric convection
Atmospheric convection is the result of a parcel-environment instability, or temperature difference, layer in the atmosphere. Different lapse rates within dry and moist air lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to...
associated with the system was significantly displaced from the center of circulation
Eye (cyclone)
The eye is a region of mostly calm weather found at the center of strong tropical cyclones. The eye of a storm is a roughly circular area and typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the second most severe weather of a cyclone...
; this led the National Hurricane Center to issue their final advisory on the depression as it had degenerated into a remnant-low pressure area
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
. As a tropical cyclone, Tropical Depression One had no effects on land; however, the precursor to the depression brought minor rainfall and light winds to parts of coastal North Carolina. Its track, formation, and timing were relatively similar to Tropical Storm One of the 1940 Atlantic hurricane season
1940 Atlantic hurricane season
The 1940 Atlantic hurricane season officially began on June 16, 1940, and lasted until October 31, 1940. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin...
.
Meteorological history
During mid-May, a frontal boundaryWeather front
A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. In surface weather analyses, fronts are depicted using various colored lines and symbols, depending on the type of front...
stalled near The Bahamas
The Bahamas
The Bahamas , officially the Commonwealth of the Bahamas, is a nation consisting of 29 islands, 661 cays, and 2,387 islets . It is located in the Atlantic Ocean north of Cuba and Hispaniola , northwest of the Turks and Caicos Islands, and southeast of the United States...
and slowly degenerated. On May 25, a shortwave trough
Trough (meteorology)
A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts.Unlike fronts, there is not a universal symbol for a trough on a weather chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked...
caused the northern portion of the system to move north of the Bahamas. The following day, an area of low pressure
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
developed along the boundary about 290 miles (465 km) south-southwest of Wilmington, North Carolina
Wilmington, North Carolina
Wilmington is a port city in and is the county seat of New Hanover County, North Carolina, United States. The population is 106,476 according to the 2010 Census, making it the eighth most populous city in the state of North Carolina...
. Tracking towards the north, the system became increasingly organized. On May 27, the National Hurricane Center
National Hurricane Center
The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...
(NHC) began issuing Tropical Weather Outlooks for the low while it was located about 120 miles (195 kilometers) south of Cape Hatteras
Cape Hatteras
Cape Hatteras is a cape on the coast of North Carolina. It is the point that protrudes the farthest to the southeast along the northeast-to-southwest line of the Atlantic coast of North America...
, North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
. An upper-level ridge
High pressure area
A high-pressure area is a region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment. Winds within high-pressure areas flow outward due to the higher density air near their center and friction with land...
situated to the southeast of the system was steering it towards the northeast. The NHC issued their final outlook on the low around 8 pm EDT (0000 UTC on May 28) while the system was located about 90 mi (150 km) east of Cape Hatteras, North Carolina, as development of the low was not expected.
On May 28, the NHC once again initiated outlooks on the system as convection quickly redeveloped. Around 11:00 am EDT (1500 UTC), they designated the system as Tropical Depression One while it was located about 310 mi (500 km) south of Providence, Rhode Island
Providence, Rhode Island
Providence is the capital and most populous city of Rhode Island and was one of the first cities established in the United States. Located in Providence County, it is the third largest city in the New England region...
. Upon being classified, the depression exhibited deep convective activity, with the center of circulation
Eye (cyclone)
The eye is a region of mostly calm weather found at the center of strong tropical cyclones. The eye of a storm is a roughly circular area and typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the second most severe weather of a cyclone...
situated on the northwestern edge. The redevelopment of the system was the result of low wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
and warm waters, up to 26 °C (78.8 °F), from the Gulf Stream
Gulf Stream
The Gulf Stream, together with its northern extension towards Europe, the North Atlantic Drift, is a powerful, warm, and swift Atlantic ocean current that originates at the tip of Florida, and follows the eastern coastlines of the United States and Newfoundland before crossing the Atlantic Ocean...
. Later that day, convection began to diminish as the depression tracked into an area of progressively higher shear and cooler waters. By this time, the system was embedded within the westerlies
Westerlies
The Westerlies, anti-trades, or Prevailing Westerlies, are the prevailing winds in the middle latitudes between 30 and 60 degrees latitude, blowing from the high pressure area in the horse latitudes towards the poles. These prevailing winds blow from the west to the east, and steer extratropical...
between a subtropical ridge
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
to the southeast and a trough
Trough (meteorology)
A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts.Unlike fronts, there is not a universal symbol for a trough on a weather chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked...
to the northwest. Around 7:30 pm EDT (2330 UTC), a QuickSCAT satellite pass over the depression found tropical storm-force winds; however, the winds were determined to have been affected by rain and therefore not representative of the depression's actual intensity. Following the satellite pass, the center of circulation became partially exposed to the northwest and the area of convection associated with the depression diminished in area.
Early on May 29, Tropical Depression One nearly attained tropical storm status, with intensity estimates using the Dvorak Technique
Dvorak technique
The Dvorak technique is a widely used system to subjectively estimate tropical cyclone intensity based solely on visible and infrared satellite images. Several agencies issue Dvorak intensity numbers for cyclones of sufficient intensity...
reaching T2.5, or 40 mph (65 km/h); however, the estimates were also as low as T1.5, leading to the intensity of the depression remaining at 35 mph (55 km/h). After a burst in convective activity overnight, shower and thunderstorm activity waned once more by 3:00 am EDT (0700 UTC). Situated at the edge of the Gulf Stream, intensification into a tropical storm was no longer anticipated. Later that morning, the center of circulation became fully exposed by strong wind shear; an approaching trough also began absorbing the small depression by this time. The remaining convection associated with the system was displaced to the southeast. With no convection developing around the depression, it degenerated into a remnant-low pressure area
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
during the afternoon of May 29. At 5:00 pm EDT (2100 UTC) the NHC issued their final advisory on Tropical Depression One. The remnants of the depression persisted until 2 am EDT (0600 UTC) on May 30, at which time it was absorbed by a warm front
Warm front
A warm front is a density discontinuity located at the leading edge of a homogeneous warm air mass, and is typically located on the equator-facing edge of an isotherm gradient...
, south of Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
.
Preparations, impact and records
The precursor to Tropical Depression One produced light showers over parts of North CarolinaNorth Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
on May 27. Rainfall in Hatteras
Hatteras, North Carolina
Hatteras is an unincorporated community in Dare County, North Carolina, United States, on the Outer Banks island of Hatteras. North Carolina Highway 12 passes through the community linking it to Frisco and Ocracoke . It is south of the famous Cape Hatteras and the Cape Hatteras Lighthouse in Buxton...
amounted to 0.1 in (2.5 mm) on May 27; sustained wind reached 15 mph (24.1 km/h) and gusts were measured up to 23 mph (37 km/h). The lowest sea level pressure recorded in relation to the system was 1009 mbar
Bar (unit)
The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar...
(hPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
; 29.81 inHg). Increased winds along coastal areas of the state was possible in relation to the outer edges of the depression. When Tropical Depression One formed on May 28, it marked the third time since 1851
1851 Atlantic hurricane season
The 1851 Atlantic hurricane season was the first Atlantic hurricane season in the official Atlantic tropical cyclone record. Six known tropical cyclones occurred during the season, the earliest of which formed on June 25 and the latest of which dissipated on October 19. These dates fall within the...
, when reliable records in the Atlantic basin began, that a pre-season cyclone developed in three consecutive years, following Subtropical Storm Andrea
Subtropical Storm Andrea (2007)
Subtropical Storm Andrea was the first named storm and first subtropical cyclone of the 2007 Atlantic hurricane season. It developed out of a previously non-tropical low on May 9 about 150 miles northeast of Daytona Beach, Florida, three weeks before the official start of the season...
which formed in May of 2007
2007 Atlantic hurricane season
The 2007 Atlantic hurricane season was an active Atlantic hurricane season that produced 17 tropical cyclones, 15 tropical storms, six hurricanes, and two major hurricanes. It officially started on June 1 and ended on November 30, dates which conventionally delimit the...
and Tropical Storm Arthur
Tropical Storm Arthur (2008)
Tropical Storm Arthur was the first Atlantic tropical storm that formed during the month of May since 1981. The first tropical cyclone of the 2008 Atlantic hurricane season, the storm formed on May 30 from the interaction of two tropical waves and the remnants of the eastern Pacific Tropical...
in May of 2008
2008 Atlantic hurricane season
The 2008 Atlantic hurricane season was a very active hurricane season with sixteen named storms formed, including eight that became hurricanes and five that became major hurricanes. The season officially started on June 1 and ended on November 30. These dates conventionally delimit the period of...
. The first occurrence of this was in 1932
1932 Atlantic hurricane season
The 1932 Atlantic hurricane season ran through the summer and the first half of fall in 1932. The 1932 season was an active one. An early tropical storm formed in May and hit Hispaniola, causing minimal damage. A Category 4 struck Galveston, Texas and the Galveston Seawall proved its worth. A...
, 1933
1933 Atlantic hurricane season
The 1933 Atlantic hurricane season was the second most active Atlantic hurricane season on record, with 21 storms forming during that year in the northwest Atlantic Ocean. The season ran through the summer and the first half of fall in 1933, and was surpassed in total number of tropical cyclones by...
, and 1934
1934 Atlantic hurricane season
The 1934 Atlantic hurricane season ran through the summer and the first half of fall in 1934. The 1934 season was fairly quiet. However, it was a continuation of deadly seasons that had been going on since 1928....
, and the second occurrence were the years of 1951
1951 Atlantic hurricane season
The 1951 Atlantic hurricane season was moderately active, starting with an pre-season hurricane and lasting until late October. The season officially started on June 15, when the United States Weather Bureau began its daily monitoring for tropical cyclone activity; the season officially ended...
, 1952
1952 Atlantic hurricane season
The 1952 Atlantic hurricane season was the most recent season in which all named storms attained hurricane status, although it was the least active since 1946. The season officially started on June 15; however, a pre-season unnamed storm formed on Groundhog Day, becoming the only storm on...
, and 1953
1953 Atlantic hurricane season
The 1953 Atlantic hurricane season was the first time an organized list of female names was used to name Atlantic storms. It officially began on June 15, and lasted until November 15, although activity occurred both before and after the season's limits...
. Tropical Depression One was also the farthest north a May tropical cyclone is known to have formed, according to the NHC's Tropical Cyclone Report.