Tropical Depression Twenty Forms In The Central Atlantic

Tropical Depression Twenty has formed in the Central Atlantic Ocean, forecast to become a hurricane as it moves out to sea with minimal threat to the Lesser Antilles.

This is the twentieth tropical cyclone of the 2020 Atlantic Hurricane Season. This depression is forecast to become a tropical storm on Sunday night. If this system is named, it will be called Teddy and become the earliest 19th named storm in Atlantic history.

The current record for the earliest 19th named storm is Tammy, on October 5th, 2005 while the earliest 19th formed tropical storm occurred on October 4th, 2005.

This tropical cyclone is not forecast to directly impact Trinidad, Tobago, or the Lesser Antilles.

List of names for the 2020 Atlantic Hurricane Season. The next named tropical cyclone will be called Teddy.
List of names for the 2020 Atlantic Hurricane Season. The next named tropical cyclone will be called Teddy.

At 5:00 PM AST, the center of Tropical Depression Twenty was located near latitude 11.4 North, longitude 33.5 West. The depression is moving toward the west-northwest near 9 mph (15 km/h) and this general motion is expected to continue for the next few days with a slight increase in forward speed early next week.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Slow strengthening is expected over the next day or so, and the depression is forecast to become a tropical storm by Sunday night. A faster rate of strengthening is possible early next week. The estimated minimum central pressure is 1005 millibars.

Tropical Depression Twenty Forecast Track as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)
Tropical Depression Twenty Forecast Track as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)

Watches & Warnings

Tropical Depression Twenty Watches and Warnings as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)
Tropical Depression Twenty Watches and Warnings as of 5:00 PM AST Saturday 12th September 2020. (National Hurricane Center)

There are no coastal watches or warnings in effect.

Hazards Affecting Land

Tropical Depression Twenty probabilities for tropical-storm-force winds as of 5:00 PM AST Saturday 12th September 2020, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)

No coastal hazards at this time. However, by Wednesday, long period swells are forecast to affect the Lesser Antilles.

This system is of no direct threat to the Windward Islands, including Trinidad and Tobago.

Tropical Depression Twenty Forecast Discussion

Tropical Depression Twenty in the Central Atlantic, well east of the Lesser Antilles. (Weathernerds)
Tropical Depression Twenty in the Central Atlantic, well east of the Lesser Antilles. (Weathernerds)

The tropical wave and associated area of low pressure that NHC has been tracking since it emerged off of Africa a couple of days ago have become sufficiently organized to be designated as a tropical depression. A curved band of deep convection developed early this morning and persisted just to the west of a well-defined low-level circulation throughout the day. An earlier ASCAT overpass showed that 25-30 kt winds over the northwestern portion of the circulation, which is the basis for the initial intensity being
set at 30 kt.

The depression has a rather large circulation, with the radius of maximum winds nearly 100 n mi from the center and the overall wind field appearing to extend outward over 300 n mi. The environment surrounding the cyclone over the next 36 h is characterized by moderate northeasterly vertical wind shear and plenty of warm water and atmospheric moisture. These factors are supportive of gradual strengthening. However, due to the large size of the system, it may take some time for it to consolidate. The NHC intensity forecast shows only slight strengthening through 36 h as the system consolidates, and that portion of the forecast is well below the
intensity guidance.

By early next week, the wind shear is expected to decrease to under 10 kt, and a faster rate of intensification is indicated from 36-96 h in anticipation of the cyclone having a better structure to take advantage of the lower shear. After 96 h, the intensity is held steady as northwesterly shear is forecast to increase while the system encounters some slightly drier air and moves over lower oceanic heat content. The NHC intensity forecast beyond 36 h starts well below most of the guidance, and trends close to the IVCN/ICON later on in the forecast period.

The depression is moving toward the west-northwest at 8 kt, steered by a mid-level ridge to its north. This ridge is forecast to build westward over the next few days, which should result in a continued general west-northwest motion, perhaps at a slightly faster forward speed early next week. By the middle of next week, a weakness is forecast to develop in the ridge, partially due to the interaction of Paulette and a mid- to- upper-level trough over the northern Atlantic at that time and the cyclone should turn to the northwest into this weakness. Overall, track guidance from the global and regional models is in decent agreement on this scenario, and the NHC forecast is between the HFIP corrected consensus HCCA and the TVCN multimodel consensus.

Forecast Discussion by Forecaster Latto from the NHC.

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