Tropical Storm Laura Enters The Caribbean Sea

Tropical Storm Laura (previously INVEST 98L and Tropical Depression Thirteen) remains disorganized Friday night. Laura broke the previous record for the earliest ‘L’ Atlantic named storm is Luis on August 29, 1995.

This tropical cyclone is not forecast to directly impact Trinidad, Tobago and the Windward Islands. However, strong low-level convergence following this system, as well as its influence on our wind regime and moisture will bring inclement weather to the area on Saturday.

At 11:00 PM AST, the center of Tropical Storm Laura was located near latitude 17.0 North, longitude 63.5 West. Laura is moving toward the west-northwest near 18 MPH (30 KM/H) and a generally west-northwestward motion at a slightly faster forward speed is expected over the next few days. On the forecast track, the center of Laura will move near or over portions of the Leeward Islands tonight, near or over Puerto Rico Saturday morning, and near the northern coast of Hispaniola Saturday night and early Sunday.

Maximum sustained winds are near 45 MPH (75 KM/H) with higher gusts. Some slow strengthening is forecast during the next few days. Tropical-storm-force winds extend outward up to 205 miles (335 KM) from the center. The estimated minimum central pressure is 1008 millibars.

Tropical Storm Laura Forecast Track as of 11:00 PM AST Friday 21st August 2020. (National Hurricane Center)
Tropical Storm Laura Forecast Track as of 11:00 PM AST Friday 21st August 2020. (National Hurricane Center)

Watches & Warnings

Tropical Storm Laura Watches and Warnings as of 11:00 PM AST Friday 21st August 2020. (National Hurricane Center)
Tropical Storm Laura Watches and Warnings as of 11:00 PM AST Friday 21st August 2020. (National Hurricane Center)

The government of the Bahamas has upgraded the Tropical Storm Watch to a Tropical Storm Warning for the southeastern Bahamas and Turks and Caicos Islands and issued a Tropical Storm Watch for the central Bahamas.

The government of Antigua has discontinued the Tropical Storm Warning for Antigua, Barbuda, St. Kitts, Nevis, Anguilla, and Montserrat.

A Tropical Storm Warning is in effect for:

  • Puerto Rico, Vieques and Culebra
  • U.S. Virgin Islands
  • British Virgin Islands
  • Saba and St. Eustatius
  • St. Maarten
  • St. Martin and St. Barthelemy
  • The northern coast of the Dominican Republic from Cabo Engano to the border with Haiti
  • The northern coast of Haiti from Le Mole St. Nicholas to the border with the Dominican Republic
  • The southeastern Bahamas and the Turks and Caicos Islands

A Tropical Storm Watch is in effect for:

  • The central Bahamas

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

Interests in Cuba should monitor the progress of Laura.

For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside of the United States, please monitor products issued by your national meteorological service.

Hazards Affecting Land

Tropical Storm Laura probabilities for tropical-storm-force winds as of 11:00 PM AST Friday 21st August 2020, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)
Tropical Storm Laura probabilities for tropical-storm-force winds as of 11:00 PM AST Friday 21st August 2020, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)

RAINFALL: Laura is expected to produce 3 to 6 inches of rain over Puerto Rico and the Virgin Islands, the Dominican Republic, the southern Haitian Peninsula, and eastern Cuba through Sunday. Maximum amounts up to 8 inches are possible along eastern portions and the southern slopes of Puerto Rico, as well as over Haiti, the Dominican Republic, and eastern Cuba. This heavy rainfall could lead to flash and urban flooding, as well as an increased potential for mudslides with minor river flooding in Puerto Rico.

1 to 3 inches of rain with isolated maximum totals of 5 inches are expected over the northern Leeward Islands, the Turks and Caicos, and southeast Bahamas.

WIND: Tropical storm conditions are expected within portions of the warning area tonight through Sunday. Tropical storm conditions are possible within portions of the watch area Sunday night.

SURF: Swells generated by Laura are affecting portions of the northern Leeward Islands. These swells are expected to spread across the northern coasts of Puerto Rico, Hispaniola and Cuba, and much of the Bahamas during the next few days. Please consult products from your local weather office.

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

Tropical Storm Laura Forecast Discussion

Tropical Storm Laura affecting weather across the Lesser Antilles (Weathernerds)

Laura remains quite disorganized this evening. Although satellite and radar images show a fair amount of deep convection over and to the east of the northern Leeward Islands, NOAA Hurricane Hunter data and surface observations indicate that the low-level center is located well to the west of the main area of deep convection. This asymmetric structure indicates that Laura is still not vertically aligned due to at least moderate wind shear. The
initial intensity is held at a possibly generous 40 kt, and most of the strongest winds are well north and east of the center.

The steering pattern for Laura appears to be very well established. A subtropical ridge over the central and western Atlantic is expected to expand westward, and that should cause Laura to move west-northwestward at a fairly quick pace during the next few days. This should take the storm across Puerto Rico on Saturday, near Hispaniola Saturday night, and close to or over Cuba on Sunday and Monday. By early next week, Laura should approach the western end of the ridge and that should cause the storm to slow down and turn toward the northwest over the eastern and central Gulf of Mexico.

Even though the steering pattern is well established, there are still chances of center reformations, which could cause small but important track changes. The NHC track forecast has been adjusted a little to the south of the previous one to account for the more southern initial position and westward motion. Near the end of the period, Laura’s track could also be influenced by Tropical Storm Marco, which is also forecast to be over the Gulf of Mexico, however, the details of that interaction are highly uncertain
at this time.

Although the storm’s structure is quite ragged at the moment, some of the models do show Laura becoming better organized this weekend and early next week due to a decrease in wind shear and very warm waters. However, there is significant uncertainty on how much the circulation will interact with the rugged islands of Hispaniola and Cuba. If the storm is able to stay north of those islands, some notable strengthening is possible as depicted by the HWRF and HMON models. However, if the storm moves over the islands, it might not strengthen at all until it passes through
that area. The bottom line is the intensity forecast is very track dependent, which makes it more uncertain than normal. Given that the new track shows more land interaction, this forecast shows less strengthening in the short term, but is largely unchanged at the longer forecast times.

Key Messages:

  1. Tropical storm conditions are expected across portions of the northern Leeward Islands, the Virgin Islands, and Puerto Rico through Saturday. Tropical storm conditions are also expected along the northern coasts of the Dominican Republic and Haiti, and the Turks and Caicos and southeastern Bahamas Saturday into Sunday. Heavy rainfall is likely across these areas beginning and could cause mudslides and flash and urban flooding through Sunday.
  2. Tropical storm conditions are possible over portions of the central Bahamas Sunday night.
  3. The details of the long-range track and intensity forecasts remain more uncertain than usual since Laura is forecast to move near or over portions of the Greater Antilles through Monday. However, Laura could bring storm surge, rainfall, and wind impacts to portions of Cuba, the Bahamas, and Florida early next week and the northern U.S. Gulf Coast by the middle of next week. Interests there should monitor the progress of Laura and updates to the forecast during the next few days.

Forecast Discussion by Forecaster Cangialosi from the NHC.

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