page_title: Tropical Depression One (2009)
section_title: Meteorological history
hierarchical_section_title: Tropical Depression One (2009) / Meteorological history
caption_attribution_description: English: Track map of Tropical Depression One of the 2009 Atlantic hurricane season. The points show the location of the storm at 6-hour intervals. The colour represents the storm's maximum sustained wind speeds as classified in the Saffir–Simpson scale (see below), and the shape of the data points represent the nature of the storm, according to the legend below. Saffir–Simpson scale Tropical depression≤38 mph≤62 km/h Category 3111–129 mph178–208 km/h Tropical storm39–73 mph63–118 km/h Category 4130–156 mph209–251 km/h Category 174–95 mph119–153 km/h Category 5≥157 mph≥252 km/h Category 296–110 mph154–177 km/h Unknown Storm type Tropical cyclone Subtropical cyclone Extratropical cyclone / Remnant low / Tropical disturbance / Monsoon depression
context_page_description: Tropical Depression One was the northernmost forming Atlantic tropical cyclone on record in the month of May. Upon being declared a tropical depression on May 28, it marked the third time that a pre-season storm formed in three consecutive years. The first tropical cyclone to develop during the 2009 Atlantic hurricane season, the depression originated from a disorganized area of low pressure off the coast of North Carolina, and quickly developed over the Gulf stream. After attaining winds of 35 mph along with a minimum pressure of 1006 mbar, the depression began to weaken due to increasing wind shear and cooling sea surface temperatures. 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.
context_section_description: During mid-May, a frontal boundary 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 km) 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 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 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 (79 °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 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 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 2100 UTC, the NHC issued their final advisory on Tropical Depression One. The remnants of the tropical depression persisted until 0600 UTC on May 30, at which time it was absorbed by a warm front south of Nova Scotia.
caption: Map plotting the track and the intensity of the storm, according to the Saffir–Simpson scale
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