Tropical Storm warnings are up for much of the Caribbean’s Lesser Antilles islands after the formation of Tropical Storm Elsa east of the islands at 5 a.m. EDT Thursday, July 1. At 11 a.m. EDT Thursday, Elsa was speeding west at 28 mph with top winds of 45 mph and a central pressure of 1006 mb. The system was positioned at a very low latitude, near 10°. This position close to the equator will slow development of Elsa, as will the relatively large size of the system and its rapid forward speed. However, Elsa otherwise had favorable conditions for development, with sea surface temperatures near 28 degrees Celsius (82°F), light-to-moderate wind shear of 5-15 knots, and a moist atmosphere with a mid-level relative humidity of 70%.

Satellite images showed Elsa with a large area of heavy thunderstorms slowly growing more organized, but northerly wind shear was keeping the heaviest thunderstorms to the south and east of the center. The first hurricane hunter mission into Elsa is scheduled for Friday morning.

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Last year, the season’s fifth named storm (Edouard) formed on July 6, breaking by six days the record set in 2005 for the earliest appearance of the Atlantic’s fifth storm of the season. Elsa’s formation date of July 1 has broken that record by five days. It’s not good to be breaking records from the busiest season on record! (The year 2020 finished with a record 30 named storms.) Elsa’s formation comes approximately two months before the average August 31 arrival of the Atlantic’s fifth named storm, according to the National Hurricane Center.

Also concerning is that Elsa formed early in the season in the main development region for hurricanes (between the coast of Africa and Central America, including the Caribbean). A named storm forming in this region early in the season is typically a harbinger of an active season, as it shows the atmosphere and ocean are conducive for activity. Elsa became a tropical storm at 48.8°W, making it the second named storm on record to form so early in the season east of 50°W. First place is held by a 1933 system that became a tropical storm on June 25 at 45.2°W (thanks go to Brian McNoldy for this stat). The year 1933 was among the busiest seasons on record, with 20 named storms, 11 hurricanes, six major hurricanes, and the highest accumulated cyclone energy (ACE) on record: 259.

The tropics typically are quiet in July: Since the beginning of the satellite era (1966), there have been 71 tropical storms, 28 hurricanes, and four major hurricanes during July in the Atlantic – an average of one named storm every 1.5 years, one hurricane every two years, and one major hurricane every 14 years (thanks go to Tony Brite for these stats). Since 1851, a total of 20 hurricanes have been observed in the Caribbean in the months of March-July – only about one every eight years (Figure 1).

Figure 1. Tracks of all storms that became hurricanes in the Caribbean (or east of the Lesser Antilles Islands) in the months of March-July from 1851-2020. A total of 20 early-season hurricanes have been observed. (Image credit: NOAA)

Forecast for Elsa

As it progresses west to west-northwest at 20-30 mph Thursday through Saturday, Elsa will mostly stay south of the dry air from the Saharan Air Layer, though water vapor imagery showed some dry air on the northwest side of Elsa on Thursday. Conditions will be favorable for development, according to the 12Z Thursday run of the SHIPS model, with light-to-moderate wind shear of 5-15 knots and steadily rising sea surface temperatures.

In addition, Elsa’s development will be favored by a large-scale region of ascending air over the Atlantic, caused by the passage Thursday and Friday of an atmospheric disturbance called a Convectively Coupled Kelvin Wave, as explained in a Tweet by Eric Webb. However, the fast forward speed of Elsa is likely to inhibit development, as fast-moving storms have trouble keeping their cores vertically aligned. The 12Z Thursday run of the SHIPS model gave only a 10% chance that Elsa would rapidly intensify by 35 mph into an 80-mph hurricane in the 24 hours ending at 8 a.m. EDT Friday.

Figure 2. Predicted wind speed (colors) and sea level pressure (black lines) for Tropical Storm Elsa at 2 p.m. EDT (18Z) Friday, July 2, from the 6Z Thursday, July 1, run of the HWRF model. The model predicted Elsa would be moving through the Lesser Antilles as a strong tropical storm with 70 mph winds and a central pressure of 987 mb. Note that because of the fast forward speed of Elsa, its tropical storm-force winds are predicted to be very asymmetric, with much weaker winds on the southwest side of the center. (Image credit: Tropical Tidbits)

As a result of these factors, Elsa is likely to be a slowly intensifying tropical storm when it passes through the Lesser Antilles Islands on Friday. The main threat will be Elsa’s heavy rains of 3-6 inches, with isolated areas of up to 10 inches. These rains are especially a concern on the island of St. Vincent, where ash from a series of eruptions April 9-22 from the Soufrière volcano could potentially mobilize into dangerous mud flows. Given the fast forward speed of Elsa, tropical storm-force winds will mostly be confined to the northern side of the center, with islands to the south of the center getting little wind damage. Elsa is predicted to pass near or just south of Barbados, a somewhat unusual event given the island’s small size and southward location. Only five tropical storms or hurricanes have made direct landfalls on Barbados in NOAA records dating back to 1851.

Figure 3. Track forecasts out to eight days for Elsa from the 6Z (2 a.m. EDT) Thursday, July 1, run of the GFS ensemble model (GEFS). The black line is the mean of the 31 ensemble members; individual ensemble member forecasts are the thin lines, color-coded by the central pressure they predict for Elsa. Most of the members predicted that Elsa would be a tropical storm moving west-northwestward through the Caribbean. There was high uncertainty on the future track of Elsa beyond Sunday morning (72 hours). (Image credit: Tropical Tidbits)

Once Elsa enters the eastern Caribbean on Saturday, it will slow its forward speed, and will likely be moving at about 15 mph on Sunday. This slow-down in forward speed may aid Elsa’s intensification by allowing the storm to get more vertically aligned; the 12Z Thursday run of the SHIPS model gave a 28% chance that Elsa could intensify into a major hurricane with 120 mph winds by 8 a.m. EDT Sunday. However, it is rare for hurricanes to rapidly intensify in the eastern Caribbean, where wind shear is typically strong, and stable sinking air is usually present.

By Saturday night, Elsa will be approaching Hispaniola. Southern portions of Haiti and the Dominican Republic are likely to receive dangerous flooding rains of 5-10 inches Saturday through Sunday, and these heavy rains will spread into eastern Cuba beginning on Saturday evening. The high mountains of Hispaniola and eastern Cuba may disrupt Elsa on Saturday night and Sunday morning, though at that point there is also considerable divergence in the models on Elsa’s future track. In the longer term, Elsa poses a potential threat to the U.S., the Bahamas, Jamaica, and western Cuba, but this threat is difficult to assess until it is apparent how much interaction Elsa will have with the high mountains of Hispaniola and Cuba.

Bob Henson contributed to this post.

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Jeff Masters

Jeff Masters, Ph.D., worked as a hurricane scientist with the NOAA Hurricane Hunters from 1986-1990. After a near-fatal flight into category 5 Hurricane Hugo, he left the Hurricane Hunters to pursue a...