[UPDATED] La Soufrière: Ashfall Advisories & Warnings In Effect For Lesser Antilles Islands

Ashfall in Barbados’ Atlantic Shores on Saturday night, 10th April 2021 (Michael Watkins)

Present La Soufrière Alert Level:YELLOWThe La Soufrière Volcano is restless. Seismicity and/or fumarolic activity are above the historical level at the volcano, or other unusual activity has been observed. This unusual activity will be specified at the time that the alert level is raised. This is level two of four.

As La Soufrière continues to violently erupt, sending plumes of ash high into the atmosphere, ashfall advisories and warnings are in effect for a number of islands across the Windward Islands.

Starting at the source of the eruption, St. Vincent and the Grenadines (SVG) Meteorological Service has issued a weather warning to “take action to protect life and property.” According to the SVG Met. Service, “moderate concentrations of Saharan dust and ash clouds are spreading from volcanic plumes of the ongoing explosive eruption at La Soufrière St. Vincent, contribute to overcast skies with very poor visibility and unhealthy air quality.” In addition, volcanic lightning and thunder are likely across St. Vincent, lessening toward the Grenadines.

For St. Vincent and the Grenadines, a marine warning is also in effect as long-period waves are likely to cause life-threatening surf and rip-currents across SVG by Monday. Hence, small-craft operators and sea-bathers should exercise extreme caution and take action to protect life and property due to very poor visibility and air quality.

The St. Lucia Meteorological Services have also issued a volcanic ash advisory for the island. Presently La Soufrière’s ash cloud is mostly affecting Barbados because of this mid to upper-level flow. Due to the close proximity of St. Vincent, it is expected that some small amount of ashfall will occur over the southern part of Saint Lucia. Residents are asked to take the necessary precautions as outlined by St. Lucia’s National Emergency Management Organization.

Barbados has been experiencing severe ashfall. The Barbados Meteorological Service (BMS) has issued both a Severe Volcanic Ash Warning and a Small Craft Warning for Barbados. A thick plume of volcanic ash from the La Soufrière Volcano in St. Vincent is currently affecting the island. A Small-Craft Warning is issued when reduced visibility (less than 5 kilometers) affects the marine area.

Periodic explosive eruptions from the La Soufriere volcano in St. Vincent continue to send thick plumes of ash traveling eastward towards Barbados. There have been observations and reports of ashfall across the island throughout the last 48 hours. Saharan dust haze also remains present across the island, which will continue to reduce visibility. These adverse conditions are expected to continue to affect Barbados with variations in intensity, and as a result, the Barbados Meteorological Service has issued and extended the Volcanic Ash Warning.

Ashfall has made its way to Grenada and its dependencies overnight Saturday 10th April 2021 through Sunday 11th April 2021. The Grenada Met Office has received reports of ash-like particles on vehicles, vegetation, and buildings throughout the state of Grenada and has issued a Volcanic Ash Advisory. According to their Met Office, “while the forecast is for the ash to move off to the east and northeast of St. Vincent, it is possible for minute ash particles to spread southward and deposit over Grenada. These small and light particles can be carried over Grenada by the low-level winds as they descend through the atmosphere. Ash deposition is likely to increase with periods of precipitation especially across northern parts of the state.” A marine advisory is also in effect for Grenada’s waters as “a combination of Volcanic ash and Saharan dust is expected to reduce visibility.”

Volcanic Ash Advisory issued at 8:30 AM Sunday 11th April 2021 from the Washington DC Volcanic Ash Advisory Center for the La Soufrière Volcano

For the aviation industry, regular “Volcanic Ash Advisories” and “Significant Meteorological Information” are being issued by the Washington DC Volcanic Ash Advisory Center and the Trinidad and Tobago Meteorological Service, respectively. Barbados and St. Vincent’s airports have been closed at least until Monday 12th April 2021.

Ashfall Advisory in effect for marine areas surrounding St. Vincent and Barbados, well north and east of Trinidad and Tobago. (National Hurricane Center – Tropical Analysis and Forecast Branch)

For mariners, an “Ashfall Advisory” is in effect for the marine waters surrounding St. Vincent and extending as far east as east of Barbados from the National Hurricane Center Tropical Analysis and Forecast Branch. Mariners are encouraged to contact the National Hurricane Center at 305-229-4424 if they encounter volcanic ash or floating volcanic debris.

Can La Soufrière’s ashfall impact T&T?

For ash to travel southward, winds will have to originate from the north. This is a highly unusual circumstance only seen when powerful low-pressure systems such as tropical cyclones move across the region, influencing wind speeds and directions across the Windward Islands.

Diagram explaining why Barbados is getting ash, even though St. Vincent is to our west!

Posted by Barbados Meteorological Services on Saturday, April 10, 2021

Through the next 14 days, models indicate mostly easterly winds below the 500 millibar level and mostly westerly to southwesterly winds above the 500 millibar level. Hence the islands most at risk for ashfall remain, St. Vincent, St. Lucia, Barbados, and Martinique. If winds at the mid to upper levels of the atmosphere shift toward the south-southwest, ashfall will be possible across Grenada’s dependencies including Carriacou and Petit Martinique, as well as several small, largely uninhabited islands. This occurred overnight from Saturday 10th April 2021 into Sunday 11th April 2021.

Similarly, as ash drifts further and further southeast over time, it is possible eastern areas of Tobago experience some ashfall by next week (April 12th-19th). For Trinidad, it still remains highly unlikely ash may travel as far south as the island. If an ash cloud does drift this far south, it will be highly dispersed in the upper atmosphere, remaining mainly an aviation hazard with little to no impacts on the ground.

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