July 28 — With Gonzalo and Hanna hardly even a distant memory, a new tropical threat has emerged in the Atlantic basin that is expected to rapidly strengthen.
A broad area of showers and thunderstorms — a feature that forecasters have been monitoring for tropical development for days — became better organized Tuesday. The National Hurricane Center designated the area potential Tropical Cyclone 9 at 11 a.m. EST.
The system was located about 400 miles east of the Windward Islands with maximum sustained winds of 40 mph and was moving west at 23 mph. AccuWeather meteorologists say it is likely to soon become the next tropical depression and storm of the 2020 season and could remain a viable threat for the next five to 10 days.
Tropical storm warnings were issued for Puerto Rico and the U.S. Virgin Islands in advance of the developing system. The government of Antigua also issued tropical storm warnings for Antigua, Barbuda, the British Virgin Islands, Montserrat, St. Kitts and Nevis.
Unlike Gonzalo, which was a very compact storm that developed in a similar area, the thunderstorms associated with the new storm extend along a swath of ocean about 700 miles long. In comparison, Gonzalo’s tropical storm-force winds only extended across 50 miles.
Despite the size of the budding system, there have been hurdles for it to overcome for development. And even though its 40-mph sustained winds met the criteria for a tropical storm, the system’s lack of a well-defined center is keeping forecasters from upgrading it to a tropical storm status. However, it may soon enter an atmosphere with more favorable conditions for strengthening.
“Moderate wind shear over the feature and dry air to its north has prevented the broad area of thunderstorms from becoming better organized the past few days,” AccuWeather senior meteorologist Rob Miller said. Strong wind shear, or the changing of winds with altitude, can limit tropical development and even tear apart organized systems, causing them to weaken.
“As this feature moves briskly along to the west-northwest, wind shear is forecast to weaken, which should allow a better-defined center to take shape,” Miller said.
AccuWeather meteorologists expect the disturbance to become the next storm of the 2020 Atlantic hurricane season. If it strengthens into a named storm, it would be called Isaias. This name was added after Ike was retired in 2008 but has not yet been used. Should the tropical storm form prior to Aug. 7, it would set another early-formation record for the season.
Irene from 2005, holds the title for earliest ever “I-storm” in the basin.
A NOAA hurricane hunter aircraft is scheduled to fly into the region for further investigation and when meteorologists are able to detect where the center of the feature is situated, that information could be key in determining where the system may track and its impact in the coming days.
If the center of the disturbance was to take shape on the northern part of the mass of moisture, then there would be a greater chance for the system to take a curved path to the northwest, north and then northeast, but perhaps east of the United States over the next seven to 10 days.
Should the center organize much farther south, then there is a more likely chance for the system to pass near or right over the islands of the northern Caribbean from the Lesser Antilles, as well as Puerto Rico, Hispaniola and Cuba later this week and this weekend.
This land interaction, especially the mountainous terrain of the larger islands, would exert a drag on the feature and would tend to take the edge off the overall strength. Such a close track over the islands of the northern Caribbean would also raise the risk to lives and property from flooding rain, mudslides and strong winds.
The feature is expected to gradually gain strength over the next couple of days.
“A large portion of the Leeward Islands, Puerto Rico, and northern sections of the Dominican Republic should prepare for wind gusts of 40-60 mph, regardless of the exact track of the center,” according to AccuWeather meteorologist Randy Adkins.
“Damage to some trees, poorly constructed buildings and temporary structures should be anticipated and power outages may result which could last several days in more remote areas,” he said.
Wind gusts of 80 mph are possible, most likely over Puerto Rico.
The high mountains on Hispaniola, and to some extent Puerto Rico and Cuba, act as a natural barrier to the path of the storm. Tropical systems generally avoid tracking over the heart of these islands as a result. However, the mountains can cause the center of an approaching tropical storm or hurricane to jump from one coast to the other and re-form in the process.
The overall strength of the system may also determine its fate as far as a track is concerned. Early on, a well-organized, stronger system is more likely to curve northwestward and northward faster than one that remains poorly organized and stays weak.
“At this juncture, the realm of possibilities of potential tracks for this system range from the Gulf of Mexico to waters east of the United States and Canada and includes all areas in between,” Miller said.
It matters where the center forms, how quickly it develops and how strong it becomes before a call can be made for the Gulf, the United States or a near-miss for the United States.
AccuWeather chief broadcast meteorologist Bernie Rayno said that whether or not Florida sees impacts depends on whether the storm moves over Hispaniola, where he said it could fall apart. If it stays north of the island and maintains a circulation over water, however, “There could be some development or certainly moisture approaching Florida, or even [elsewhere on] the southeast coast of the United States,” he said.
Other factors include the amount of wind shear near North America, which is never in a steady state. A non-tropical system, associated with a dip in the jet stream, may also help to steer the system to the north and northeast once it approaches the United States.
Waters over the northern Caribbean, western Atlantic and in the Gulf of Mexico are sufficiently warm to not only sustain a tropical system but also potentially add to its strength.
Either way, the mass of moisture will cause an uptick in drenching downpours and gusty thunderstorms that will spread westward through the Leeward and Windward islands at midweek, followed by Puerto Rico, the Dominican Republic, Turks and Caicos, eastern Cuba and the southeastern Bahamas late this week and into this weekend.
“Rainfall amounts of 2-4 inches will be common across the Lesser Antilles, Puerto Rico, and the Dominican Republic. Locally higher amounts of 4-8 inches … are possible over the higher terrain, particularly over Puerto Rico. Flash flooding is likely to result in a number of areas with mudslides a threat along the hills and mountains,” Adkins said.
All interests from the northern Caribbean to the Bahamas, Bermuda, the United States and northeastern Mexico should monitor the progress.The 2020 season has outpaced the formation speed of the 2005 season, but not so much in terms of the number of hurricanes. Hanna became the first hurricane of the Atlantic season early on Saturday and also became the first hurricane to strike the United States. By the time Hanna became a hurricane, the 2005 season had already spawned three hurricanes — Cindy, Dennis and Emily. Dennis and Emily became major hurricanes with peak winds of 150 and 160 mph respectively. Hurricane Irene would follow in August in 2005. Irene peaked with maximum sustained winds of 105 mph, which is a Category 2 hurricane.
Disturbances are lining up over Africa and moving westward with one feature every one to three days apart. This series of disturbances is known as the Cabo Verde part of the hurricane season and is just beginning to ramp up.
Most likely more early-season formation records will be set in the coming weeks with 2005 holdings being swapped with 2020 newcomers. Following Irene’s record from Aug. 7, the “J-storm” record is held by Jose on Aug. 22, 2005 with the “K-storm” record held by the infamous Katrina on Aug. 24, 2005.
The 10th and 11th names on this year’s tropical list, should they be needed, are Josephine and Kyle.