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Tropical Storm Julia forms in the southern Caribbean » Yale Climate Connections

Tropical Storm Julia forms in the southern Caribbean » Yale Climate Connections
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Tropical Storm Julia, which formed off the northern coast of Venezuela at 11 a.m. Friday with sustained winds of 40 mph, is expected to become a hurricane and bring dangerously heavy rain to much of Central America and southeastern Mexico. Julian is forecast to make landfall in Nicaragua on Sunday morning.

Julia’s Oct. 7 date comes nearly two weeks after season 10’s typical Sept. 22 appearance.c a storm called This season’s activity now stands at 10 named storms, four hurricanes and two major hurricanes, with an Accumulated Cyclone Energy (ACE) index of 78% of the historical average. The 1991-2020 averages For October 7, it is 11.6 named storm, 5.6 hurricane and 2.5 major hurricane. So despite Ian’s disastrous onslaught, the Atlantic as a whole is still having a slightly less active season than usual.

Julia formed in an unusual place for a tropical cyclone: ​​very close to the coast of Venezuela. During the tropical depression, between 11:00 PM EDT Thursday and 8:00 AM EDT Friday, Julia crossed the two peninsulas of Venezuela. Paraguana and Guajira, extending northward into the Caribbean Sea. Only one other tropical cyclone made it further south in Venezuela in NOAA records: Tropical Storm Bret (1993), moved physically in northern Venezuela, causing devastating floods and killing more than 200 people.

Figure 1. Tropical depression 13 (center point of circle), forming on the eastern side of the Paraguana Peninsula, and all other tropical cyclones within 60 nautical miles of the location of TD 13 by 11:00 p.m. EDT Thursday, October 6, 2022. ( Image credit: NOAA Historical Hurricane Tracks)

By Friday afternoon, Julia was bringing strong thunderstorms to northern Venezuela and Colombia. satellite images. Julia had modest-sized severe thunderstorms that began to form significant low-level spiral bands that grew in areal extent and organization. Proximity to the coast of South America hindered development.

Forecast for Julia

A ridge of high pressure to the north of Julia will continue to move it on a westward trajectory of about 15 mph into early next week, centered off the coast of South America by Friday afternoon. Except for its proximity to land, conditions for Julia’s development will be favorable, with warm waters of 29.5 degrees Celsius (85 °F), moderate wind shear of 10–15 nautical miles, and a humid atmosphere (moderate relative humidity ) of 75–80%) .

Figure 2. GFS ensemble model 6Z track forecasts for Julia starting Friday, October 7, up to 10 days. The individual forecasts of the 31 ensemble members are color-coded lines with their forecast wind speed in knots for Julia; red colors correspond to category 1 hurricanes. The time in hours since model launch is shown in gray text. (Image credit: weathernerds.org)

Models are in good agreement on Julia’s forward speed, slowing to 12 mph from its current 18 mph by the time the storm makes landfall in Nicaragua on Sunday morning. After Julia makes landfall, models show a likely tilt to the west-northwest, which will keep the center over land until it dissipates. Models are closely grouped in their track forecasts for Julia, and a landfall in Nicaragua is very likely, with the Colombian islands of San Andres and Providence off the coast of Nicaragua also at risk.

After Julia moves away from the South American coast on Friday afternoon, a period of continued intensification is expected, with a burst of more rapid intensification possible Saturday into Sunday. The western Caribbean will have favorable conditions for Julia to become a hurricane this weekend, and this part of the Atlantic is known for seeing some strangely rapid intensification events. 6Z Friday runs of the top two intensity models, HMON and HWRF, show Julian reaching Category 2 with sustained winds of 100 mph as it makes landfall Sunday morning in Nicaragua. On Friday 12Z, the statistics-based SHIPS and DTOPS rapid intensification tools both gave a near 30 percent chance that Julia would reach near hurricane strength by Saturday morning, and SHIPS gave a 29 percent chance that Julia would pack sustained winds of 105 mph. (category 2) until Sunday morning.

Figure 3. European model 0Z forecast 5-day precipitation beginning Friday, October 7, ending at 8:00 PM EDT on Tuesday, October 11. The model predicted showers across much of Central America and southeastern Mexico, with some areas receiving more than 10 inches (dark purple). (Image credit: weathermodels.com)

Heavy rains are the main threat

The main threat from Julia will be the 5 to 10 inches of dangerously heavy rain expected over large parts of Central America and southeastern Mexico beginning Saturday. Much of Central America, including eastern Nicaragua where Julian’s heaviest rains will fall, has been relatively dry over the past three months, receiving an average of 50-80% precipitation. However, the arrival of heavy rains in northwestern Honduras will be unwelcome: the region is facing flooding as a result of heavy rains in the last week of September. A flood in the Ulua River in the Sula Valley has killed 12 people led 16,000 people were evacuated. Saturated soils in the region will cause more flooding if any rain falls from Julia. The 0Z Friday run of the European model (Figure 3) predicted that Julia would bring 5-10 inches of 5-day rainfall to northwestern Honduras.

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