Tropical Update: Dorian Strengthening, Erin Goes Post-Tropical, Two Atlantic Tropical Waves

Tropical Update Overview:
Tropical Wave 41: This tropical wave is located in the Central Atlantic, forecast to move across the Lesser Antilles on Saturday into Sunday. No significant change in the weather forecast, beyond localized afternoon showers and downpours. This increase in moisture may bring localized and brief street flooding.
Tropical Wave 42 – This tropical wave has just moved off the African coast into the Atlantic Ocean. This wave is forecast to move across the Lesser Antilles by mid-next week, with much of the moisture associated with this wave forecast to move across the Northern Windwards and Leewards, north of Trinidad and Tobago. No significant change in weather forecast at this time, beyond localized afternoon showers and downpours. This increase in moisture may bring localized and brief street flooding.
Hurricane Dorian: Hurricane Dorian continues to strengthen as it moves into the Southwestern Atlantic, after battering the Virgin Islands. Based on the latest advisory from the National Hurricane Center, Dorian is forecast to make landfall on Eastern Florida early next week as a Major Category 4 Hurricane.
Post-Tropical Cyclone Erin – Tropical Storm Erin has lost its tropical characteristics and became post-tropical. It continues to move towards Nova Scotia over the next 24 hours, and some slight intensification is expected during that time.
— No direct tropical threats forecast for Trinidad and Tobago over the next five days.

Before we dive into the Tropical Update, a few notes:

  • Tropical waves are a normal part of the rainy season.
  • Not every tropical wave will form into a tropical cyclone.
  • Weaker tropical waves produce more rainfall across Eastern parts of the islands with mostly cloudy conditions and a few showers across western parts of the islands.
  • Rainfall will be more isolated and intermittent with weaker tropical waves that do not have ITCZ or upper-level support.
  • Saharan Dust may weaken tropical waves.

You can read more about the weather associated with Tropical Waves, as well as what to expect as these waves move through the region below.

Tropical Wave 41

A weak tropical wave located at 47W, east of Trinidad and Tobago. This wave is located in an area with dense Saharan dust and is forecast to move across the region Saturday into Sunday with minimal changes in the weather across T&T. Credit: Weathernerds.org
A weak tropical wave located at 47W, east of Trinidad and Tobago. This wave is located in an area with dense Saharan dust and is forecast to move across the region Saturday into Sunday with minimal changes in the weather across T&T. Credit: Weathernerds.org

Tropical Wave 41 is located in the Central Atlantic Ocean, at 47W, along 22N to 6N, moving west at approximately 10-15 knots. This wave is embedded in dry, Saharan air, which is limiting convection near the wave axis.

Though there is a surge of moisture associated with the wave axis, this wave is not forecast to produce any significant rainfall as it moves across Trinidad, Tobago and the Lesser Antilles on Saturday into Sunday.

However, this tropical wave is forecast to weaken the high pressure dominating the region, slackening winds across the islands. Daytime heating and sea breeze convergence with this elevated moisture may cause some heavy afternoon downpours, which may trigger street flooding and be accompanied by gusty winds. This activity will be highly isolated. Similar activity may occur on Sunday, as we move into this usual wet-season-pattern of afternoon downpours after a mostly hot and sunny day.

Tropical Wave 42

 A tropical wave is moving into the Atlantic Ocean off the West Coast of Africa. This wave is forecast to move across the Lesser Antilles next Wednesday into Thursday, with much of the active weather remaining north of Trinidad and Tobago. Credit: Weathernerds.org
A tropical wave is moving into the Atlantic Ocean off the West Coast of Africa. This wave is forecast to move across the Lesser Antilles next Wednesday into Thursday, with much of the active weather remaining north of Trinidad and Tobago. Credit: Weathernerds.org

A Tropical wave is moving into the Atlantic Ocean, located at 20W, along 20N to 5N. This wave is forecast to move across the Lesser Antilles in 6-7 days, so any impacts will be hard to pin down for Trinidad and Tobago at this time. However, based on the latest modeling, much of the moisture associated with this wave will move across the Lesser Antilles north of Trinidad and Tobago. We’ll have more in the following tropical update.

Hurricane Dorian

Hurricane Dorian is forecast to continue strengthening as it moves across the Southwestern Atlantic. It is forecast to become a Category Four hurricane at landfall across Eastern Florida. Credit: Weathernerds.org
Hurricane Dorian is forecast to continue strengthening as it moves across the Southwestern Atlantic. It is forecast to become a Category Four hurricane at landfall across Eastern Florida. Credit: Weathernerds.org

At 11:00 AM, the center of Hurricane Dorian was located near latitude 21.4 North, longitude 67.2 West. Dorian is moving toward the northwest near 20 KM/H, and this general motion is expected to continue through Friday. A west-northwestward motion is forecast to begin by Friday night and continue into the weekend.

On this track, Dorian should move over the Atlantic well east of the southeastern and central Bahamas today and on Friday, approach the northwestern Bahamas Saturday, and move near or over portions of the northwest Bahamas on Sunday.

Maximum sustained winds are near 140 KM/H with higher gusts to 165 KM/H. Strengthening is forecast during the next few days, and Dorian is expected to become a major hurricane on Friday and remain an extremely dangerous hurricane through the weekend.

Hurricane-force winds extend outward up to 30 kilometers from the center and tropical-storm-force winds extend outward up to 150 kilometers.

The minimum central pressure based on data from a NOAA Hurricane Hunter aircraft is 986 millibars.

For the latest, see the updated advisories from the National Hurricane Center.

Post-Tropical Cyclone Erin

The Remnants of Erin remain well offshore the northeastern United States. Erin has lost its tropical characteristics and the last advisory has been issued by the National Hurricane Center. Credit: Weathernerds.org
The Remnants of Erin remain well offshore the northeastern United States. Erin has lost its tropical characteristics and the last advisory has been issued by the National Hurricane Center. Credit: Weathernerds.org

At 5:00 AM, the center of Post-Tropical Cyclone Erin was located near latitude 36.1 North, longitude 71.6 West. The post-tropical cyclone is moving toward the north-northeast near 24 KM/H. A turn toward the northeast and a faster forward motion are expected later today, with this motion continuing through Friday.

Maximum sustained winds are near 55 KM/H with higher gusts. The post-tropical cyclone is expected to strengthen a little on Friday before it is absorbed by a larger extratropical low over eastern Canada Friday night. The estimated minimum central pressure is 1005 millibars.

This system is forecast to move Nova Scotia over the next 24 hours, and some slight intensification is expected during that time. After 24 hours, the system is expected to be absorbed by a larger extratropical low over eastern Canada. This is the last tropical update on this system.

Tropical Cyclone Climatology

Tropical Cyclone Points of Origin during the month of August. This month, the attention goes to tropical waves moving across the Atlantic, particularly as they near the Lesser Antilles, as well as low-pressure systems in the Gulf of Mexico and troughs Southeast of the United States.

In August, we turn our eyes to East of the Lesser Antilles, the Southeastern areas of the United States and the Gulf of Mexico for the formation of tropical cyclones in the Atlantic Basin, historically. However, tropical cyclones can form in the Atlantic Basin, without regard for the location once conditions support development. Stay updated with the latest tropical update!

Overall, conditions have become slightly more favorable for tropical cyclone development though dominating dry, Saharan air remains across the Atlantic.

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