Tropical Storm Elsa Racing WNW, Showers & Thunderstorms Already Affecting Windwards

Tropical Storm Elsa is intensifying as it rapidly moves west-northwest towards the Windward Islands. Showers and thunderstorms are already affecting Trinidad, Tobago and Barbados ahead of the storm.

Based on available forecast data, this system is expected to traverse the Windward Islands on Friday morning through the afternoon as a strong tropical storm.

Specifically for Trinidad and Tobago, while direct impacts are not expected, periphery impacts such as an atypical wind regime, feeder bands (strong showers, thunderstorms, and gusty winds associated with Tropical Storm Elsa), and agitated seas are likely on Friday into Saturday.  An Adverse Weather Alert (Yellow Level) is in effect for T&T from the Trinidad and Tobago Meteorological Service from 8:00 PM Friday through 12:00 PM Saturday.

The Latest From The National Hurricane Center

Tropical Storm Elsa’s Forecast Track as of 11:00 PM Thursday 1st July, 2021. (National Hurricane Center)

At 11:00 PM AST on July 1st, the center of Tropical Storm Elsa was located near latitude 11.8 North, longitude 55.9 West. Elsa is moving toward the west-northwest near 43 KM/H and this motion is expected to continue for the next couple of days. On the forecast track, Elsa will pass near or over portions of the Windward Islands or the southern Leeward Islands on Friday, move into the eastern Caribbean Sea late Friday and Friday night, and move near the southern coast of Hispaniola on Saturday. By Sunday, Elsa is forecast to move near Jamaica and portions of eastern Cuba.

Recent satellite wind data indicate that maximum sustained winds have increased to near 85 KM/H with higher gusts to 102 KM/H. Some additional strengthening is forecast over the next 12 to 24 hours. Recent satellite wind data also indicates the tropical-storm-force winds now extend outward up to 220 kilometers, mainly to the north of the center. NOAA Buoy 41040, located more than 200 miles north of the center of Elsa, recently reported a wind gust of 61 KM/H. The estimated minimum central pressure is 1003 millibars.

Tropical Storm Elsa’s Forecast Track as of 11:00 PM Thursday 1st July, 2021. (National Hurricane Center)

Tropical Storm Elsa’s Watches & Warnings

Tropical Storm Elsa’s Tropical Storm Watches and Warnings as of 11:00 PM Thursday 1st July 2021. (National Hurricane Center)

A Tropical Storm Warning is in effect for St. Vincent and the Grenadines, Barbados, Martinique and St. Lucia.

A Tropical Storm Watch is in effect for Grenada and its dependencies, the southern and western coasts of Haiti from the southern border of the Dominican Republic to Le Mole St. Nicholas, the southern coast of the Dominican Republic from the southern border of Haiti eastward to Punta Palenque, and Jamaica.

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, in this case within 36 hours.

Other Alerts Issued For Several Islands

A number of other alerts are in effect for several islands across the Lesser Antilles, though some may not be under direct threat from Tropical Storm Elsa.

Trinidad and Tobago

 An Adverse Weather Alert (Yellow Level) is in effect for T&T from the Trinidad and Tobago Meteorological Service from 8:00 PM Friday through 12:00 PM Saturday.

According to the TTMS, “periods of rain and showers of varying intensities, are expected mainly overnight (Friday 2nd July 2021/Saturday 3rd July 2021), with a 70% (high) chance of thunderstorm activity. Gusty winds in excess of 55 KM/H may be experienced especially in the vicinity of downpours and localized flooding is highly likely. Seas can become agitated at times, due to the strong winds.”

Grenada and its dependencies.

A tropical storm watch remains in effect for the country. Grenada, Carriacou and Petite Martinique can expect cloudy to overcast conditions with showers (which may become heavy) and thundershowers accompanied by gusty winds by Friday morning, into Saturday. The likelihood of significant impacts are greater for the sister isles of Carriacou and Petite Martinique. According to the Grenada’s National Disaster Management Agency, potential impacts are expected to be most significant across the northern section of the state, with flash flooding, downed trees and powerlines, landslides, and rockfalls.

St. Vincent and the Grenadines

In addition to a Tropical Storm Warning, St. Vincent and the Grenadines (SVG) also have a red-level high surf advisory warning of above normal swells and gusty winds, calling for small craft operators to remain in port. SVG’s National Emergency Management Organization NEMO is also warning of lahars, mudflows, and flooding.

According to NEMO, “It is expected that whenever rain falls, there will be significant steaming, particularly in the valleys where Pyroclastic Density Currents have come down.  The Pyroclastic Density Currents can result in warm or hot mudflows, which will also steam.  This means that it would not be unusual to have significant steaming in some or all of the valleys on the volcano.  Also, while this steaming would be mainly focused in the upper parts of the valleys, due to the fact that the mudflows can also steam, the steaming can extend all the way down the valley to the coastline.”

Barbados

Alerts in effect from the Barbados Meteorological Service for Barbados as of Thursday night.

There are several advisories in effect for Barbados over the next 72 hours, concerning excess rainfall, marine interests, severe thunderstorms, and wind.

In addition to the Tropical Storm Warning, the Barbados Meteorological Service has issued a High Surf Advisory (orange-level), and a High Wind Warning (red-level).

Martinique, Guadeloupe and the French Antilles

Alerts in effect from Meteo France for the French Antilles (Meteo France)

A Yellow-level alert is in effect for St. Martin and St. Barthelemy for strong winds, yellow-level alerts are in effect for Guadeloupe for heavy rains and thunderstorms, coastal flooding and rough seas as well as strong winds. For Martinique, a Tropical Storm Warning is in effect, as well as orange-level alerts for heavy rains and thunderstorms, coastal flooding and rough seas as well as strong winds.

Dominica

While this country is not under any tropical storm watches or warnings at this time, the Dominica Meteorological Service has issued an advisory for the country.

The Met Service in that country is warning of the following:

  • Winds gusting to tropical storm force, that is, 45 knots, 90 KM/H, 50 MPH, particularly across the south and elevated areas
  • Rainfall amounts of 60 millimeters to 100 millimeters in moderate to heavy showers and thunderstorms
  • Waves up to 4.0 meters or 13..0 feet along the eastern and southern coasts and near 3.0 meters or 10.0 feet along the west coast.
Tropical Storm Elsa’s Tropical Storm Watches and Warnings as of 11:00 PM Thursday 1st July 2021. (National Hurricane Center)

According to the National Hurricane Center, interests elsewhere in the Windward Islands, Leeward Islands, the Virgin Islands, Puerto Rico, the Dominican Republic, Haiti, and eastern Cuba should monitor the progress of Elsa. Additional watches and warnings will likely be required on Friday.

Tropical Storm Elsa: Hazards Affecting Land

Tropical Storm Elsa’s probabilities for tropical-storm-force winds as of 11:00 PM Thursday 1st July 2021. (National Hurricane Center)

WIND: Tropical storm conditions are expected in portions of the Windward and the southern Leeward Islands within the warning areas on Friday. Tropical storm conditions are possible in the watch areas in the Lesser Antilles on Friday. Tropical storm conditions are possible in the watch area in the Dominican Republic and Haiti on Saturday and are possible in Jamaica Saturday night.

STORM SURGE: A storm surge will raise water levels by as much as 1 to 3 feet above normal tide levels in areas of onshore winds along the southern coast of Hispaniola.

RAINFALL: Elsa is expected to produce rainfall totals of 3 to 6 inches with maximum amounts of 10 inches on Friday across the Windward and the southern Leeward Islands, including Barbados. This rain may lead to isolated flash flooding and mudslides.

Over Puerto Rico, rainfall of 1 to 3 inches with localized amounts of 5 inches is expected Friday into Saturday. This rain may lead to isolated flash flooding and minor river flooding, along with the potential for mudslides.

Along portions of southern Hispaniola, rainfall of 4 to 8 inches with isolated maximum amounts of 12 inches is possible on Saturday. This rain may lead to scattered flash flooding and mudslides.

Additional island-specific impacts have been mentioned above.

Tropical Storm Elsa’s probabilities for hurricane-force winds as of 11:00 PM Thursday 1st July 2021. (National Hurricane Center)

This system is of no direct threat to Trinidad and Tobago at this time.

Important Note: The current forecast is based on Tropical Storm Elsa moving just south or across Barbados on Friday, then across the Windward Islands. Adjustments in track southward may increase rain chances for T&T but tropical-storm-force winds are forecast to remain across the northern half of Elsa’s core, thus posing no direct threat to T&T at this time.

Tropical Storm Elsa’s Forecast Discussion

Tropical Storm Elsa (Weathernerds.org)

The convective structure with Elsa tonight appears to be somewhat better organized than earlier, with a bursting type pattern of cold -75 to -80 C cloud top temperatures just to the northeast of the estimated center. However, a SSMIS microwave pass at 2130 UTC revealed that, underneath the cirrus, the deeper convection is still struggling to rotate up-shear as the system moves quickly to the west-northwest. Despite that fact, an ASCAT-A pass clipped the northeastern edge of Elsa and showed several wind retrievals of 44-46 kt. In addition, the most recent subjective Dvorak satellite classification from TAFB was T3.0/45 kt. In support of these data, the current estimated intensity was raised to 45 kt for this advisory.

Tropical Storm Elsa’s Forecast Track as of 11:00 PM 1st July, 2021. (National Hurricane Center)

Elsa continues to move quickly to the west-northwest at 290/23 kt. A continued rapid motion to the west-northwest is expected for the next 36 hours as the storm remains steered by a strong subtropical ridge to its north, and the guidance has trended a bit faster once again tonight. Thereafter, Elsa will reach the western extent of this ridge which will be eroded by a strong mid-latitude trough centered off the eastern US. Once again, the guidance spread increases greatly by this time, with the GFS/UKMET on the slow and left side of the guidance envelope, the ECMWF and its ensembles on the fast and right side, and the Canadian roughly in the middle. Interestingly, the latest GFS ensembles show some bifurcation within the larger guidance envelope, with the strongest members further south and west. The latest NHC track forecast is close to the previous track early on but somewhat faster, and in the latter period was nudged just slightly eastward towards the TVCN consensus. However, the track forecast in the latter time period remains low confidence.

The intensity forecast with Elsa also continues to be challenging this evening. While the GFS-based SHIPS guidance indicates that the current 200-850-hPa vertical wind shear is only 5-10 kt, the strong east-southeasterly low-level flow Elsa is embedded in is resulting in stronger 15-20 kt of west-northwesterly mid-level shear. This mid-level shear has thus far prevented deep convection from wrapping around the circulation and helping to align the low- and mid-level vortex like the GFS/HWRF models have been forecasting over the past day. Despite this convective structure, the fast east-southeasterly low-level flow will likely continue to enhance the winds on the north side of the circulation. For this reason, the intensity forecast still shows intensification in the short term to 55 kt. However, additional intensification beyond that will likely require a better vertically aligned vortex. This structure may be difficult to achieve as moderate mid-level shear continues, counter to the motion vector of the storm. After 48 hours, the intensity forecast shows slight weakening given the possibility of land interaction over the Greater Antilles. The latest intensity forecast continues remain on the conservative side relative to the guidance, especially the HWRF/HMON regional hurricane models, and is also low confidence.

Key Messages:

  1. Tropical storm conditions are expected to begin early Friday in portions of the Windward and the southern Leeward Islands, and are possible over portions of southern Hispaniola on Saturday, and are also possible over Jamaica beginning Saturday night.
  2. Heavy rainfall from Elsa will move quickly across the Windward and the southern Leeward Islands, including Barbados, on Friday. Outer rain bands will impact Puerto Rico on Friday and southern Hispaniola by early Saturday. Flooding and mudslides are possible.
  3. There is a risk of wind and rainfall impacts in portions of Cuba, the Turks and Caicos, and the Bahamas through early next week. Interests in these areas should monitor Elsa’s progress and updates to the forecast.
  4. There is a risk of storm surge, wind, and rainfall impacts in the Florida Keys and portions of the Florida Peninsula early next week. However, the forecast uncertainty remains larger than usual due to Elsa’s potential interaction with the Greater Antilles this weekend. Interests in Florida should monitor Elsa’s progress and updates to the forecast.

Forecast discussion by NHC Forecasters Papin and Brown.

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