Tropical Storm Otto (2004)

Tropical Storm Otto was a tropical storm that formed during the 2004 Atlantic hurricane season. It formed on 29 November, very late in the season, and persisted into December, dissipating on 3 December. Tropical Storm Otto was the fifteenth and final storm to be named in 2004. No damages were reported relating to Otto, as it remained far from land, never moving within 800 miles (1290 km) from the island of Bermuda, the nearest land mass. Tropical Storm Otto was most notable for having been a rather rare out-of-season storm, as it continued its life into the month of December (the official hurricane season ended on 30 November).

Meteorological history
On 21 November, a cold front left the east coast of the United States and slowly moved eastward. It then stalled midway between Bermuda and the Azores Islands on 25 November. At this point, an extratropical low developed along the front, due to a strong upper-level trough that was moving southward. The low formed about 1,150 miles (1,850 km) southwest of the Azores Islands on 26 November. The surface low rapidly deepened and became a large gale area late that day, due to the strong baroclinic effects of the upper-level low. The upper-level trough was still moving southward, and it generated a cutoff low to the south of the surface low on the same day. The upper low and surface low moved generally southward at about 6 to 12 mph (9 to 19 km/h) for three days.

Late on 28 November, weak ridging to the north of the upper-low formed over the surface low, and convective banding features started to form near the low-level centre. The extratropical low gradually lost its frontal structure, and developed into Subtropical Storm Otto on 29 November while located 1,150 miles (1850 km) east-southeast of Bermuda.

On 29 November, Otto was moving to the north-west through a weak area in the mid-level subtropical ridge located north of the storm. The storm strengthened, and at this time, carried maximum sustained winds of 50 mph (85 km/h), which would be Otto's peak intensity. Convection increased further, and Otto attained warm-core characteristics on 30 November located about 700 nautical miles (800 miles, 1300 km) east of Bermuda, which caused it to be designated operationally as Tropical Storm Otto. For the next couple of days, Otto wandered over rather cool water, with sea temperatures of up to 23° Celsius. Otto was under a region of weak vertical shear between two upper-lows to its south and north. However, the slightly favorable upper-level flow pattern allowed the storm to maintain some deep convection in its centre.

As a tropical storm, Otto maintained an intensity of 45 mph (75 km/h), but did not strengthen any further, and was unable to reach the intensity it had gained as a subtropical storm. Operationally, Otto reached a peak intensity of 45 knots at this time, but after reanalysis following the hurricane season, was dropped to 40 knots in the best track data published by the National Hurricane Center. Otto turned to the south-southeast, still moving slowly on 1 December, as north-northwesterly mid to upper-level flow increased on the east side of a developing ridge off the United States East Coast. However, vertical shear increased, displacing the deep convection and weakening the storm. Otto was downgraded to a tropical depression on 2 December, as the shear and the mid-level dry air eroded the convection, and Otto deteriorated into a remnant low on 3 December while located approximately 920 miles (1480 km) southeast of Bermuda. For the next two days, the broad remnant drifted south-southwestward, finally dissipating on 5 December 920 miles (1480 km) northeast of the northern Leeward Islands.

Impact and naming
There were no reports of damage or casualties resulted from Tropical Storm Otto, as the storm stayed at sea and never moved close to any continents or islands.