Tropical Depression One was a tropical depression that did not attain tropical storm status during the 2009 Atlantic hurricane season. The cyclone developed during the last several days of May. This marked the first time that a tropical cyclone developed in the Atlantic during the month of May for three consecutive years since the period of 1951-1953.

The depression caused no damage and no deaths, as it remained well out at sea throughout its existence.

Satellite image of the depression
FormationMay 28, 2009
Dissipation May 29, 2009
Highest winds 35 mph
Lowest pressure 1006 mbar
Deaths None
Damages None
Areas affectedNone
Part of the 2009 Atlantic hurricane season

Meteorological History


The genesis of Tropical Depression One can be traced back to a nearly stationary decaying cold front that stretched from north of the Greater Antilles to the Bahamas for nearly a week. By May 25, a mid- upper-level shortwave trough advanced eastward from Florida, which pushed the western end of the aforementioned front northward. The next day, a low pressure area had developed along the front about 250 miles south-southeast of Wilmington, North Carolina, though deep convection associated with the low remained minimal at this time. The low moved northward then northeastward, embedded within the southwesterly flow ahead of the aforementioned shortwave trough. The low came within 75 miles of the Outer Banks, generating shower activity in the area, as well as gusty winds. Early on May 28, a cluster of deep convection developed near the center of the low and by 0600 UTC that day, it is estimated that the low had acquired enough organization to be designated a tropical depression while centered around 150 miles north-northeast of Cape Hatteras.

Over the following 24 hours, the cyclone moved northeastward then east-northeastward across the warm waters of the Gulf Stream, steered by a trough to the west and a ridge to the east. During this period, the depression generated intermittent bursts of deep convection, but none of them ever persisted long enough for the cyclone to attain tropical storm status. By May 29, westerly shear increased over the system. This, combined with cooler waters north of the Gulf Stream, prevented the depression from generating persistent deep convection near its center. By 0000 UTC May 30, the cyclone had degenerated into a remnant low pressure area while centered about 300 miles south-southeast of Halifax, Nova Scotia. The remnants of the former tropical cyclone dissipated shortly thereafter as it merged with a warm front that extended southeastward from a larger extratropical cyclone centered across eastern Canada.


The precursor disturbance to the cyclone produced light rainfall across portions of North Carolina on May 27, peaking at 0.01 inches at Cape Hatteras. Additionally, sustained winds of 15 mph, with gusts up to 23 mph, was reported, also at Cape Hatteras. The lowest recorded pressure associated with the system on land was 1009 mb.


When the depression developed on May 28, it marked the third consecutive year in the Atlantic basin in which a tropical cyclone developed during the month of May. The last time such an occurrence occurred was during the period of 1951-1953, and prior to that, the period of 1932-1934. In addition, the cyclone is reportedly the furthest north forming May tropical cyclone on record in the basin.

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