Although Tropical Depression Chantal is very close to becoming a remnant low, the Atlantic likely won’t be entering a lull, as two disturbances have a shot at becoming tropical cyclones this weekend. The first, Invest 98L, is a trough of low pressure just east of South Florida, and is likely to become a tropical depression by Sunday as it moves northeastward. The second, Invest 99L, is a small area of low pressure over the central tropical Atlantic that is gradually becoming better organized. The next two names on the Atlantic naming list are Dorian and Erin. In the eastern Pacific, Tropical Storm Ivo has passed the sparsely populated Clarion Island but is expected to remain offshore of the Baja California Peninsula.

Chantal no threat, likely to be a remnant low soon

Tropical Depression Chantal is gradually losing deep convection and could become a remnant low at any time. As of 11:00 a.m. EDT Friday, Tropical Depression Chantal was centered near 36.6°N 40.8°W, and was moving south-southeast at about 7 mph. Maximum sustained winds were 25 knots (30 mph), with an estimated minimum pressure of 1012 mb. Chantal is no threat to any land areas, and this is my last statement on Chantal on this blog.

Ivo not expected to reach hurricane intensity

As of 9:00 p.m. MDT (11:00 a.m. EDT), Tropical Storm Ivo was centered near 18.9°N 115.0°W. Maximum sustained winds were 55 knots (65 mph), with an estimated minimum pressure of 992 mb. Ivo recently passed by Clarion Island, and surface observations found Ivo was slightly stronger than originally anticipated. However, Ivo is likely at its peak intensity, and weakening should begin soon as it heads for cooler waters.

Invest 98L gradually becoming better organized, likely to develop by Sunday off the southeast U.S. coast

As of 18:00 UTC Friday, Invest 98L was located near 25.6°N 79.9°W. Maximum sustained winds were 25 knots (30 mph), with an estimated minimum pressure of 1013 mb. The National Hurricane Center (NHC) gives 98L a 70 percent chance of development within 48 hours, and a 90 percent chance within five days. An Air Force Hurricane Hunter aircraft is scheduled to investigate 98L on Saturday if necessary. The 12z Friday runs of the ECMWF, GFS and UKMET models all developed 98L into a tropical cyclone by Tuesday. The ECMWF and UKMET models are more aggressive, bringing 98L to hurricane strength. The GFS model is weaker, only developing 98L into a strong tropical storm. The most likely scenario is 98L remains offshore the United States East Coast, but it should still be monitored as it could bring rough surf to the coast next week. Atlantic Canada should also keep an eye on 98L, as a direct hit or close brush remains a distinct possibility at this time.

The 18z SHIPS model run predicted that 98L would have favorable environmental conditions for development for the next 72 hours or so, with wind shear less than 10 knots, sea surface temperatures above 29°C (84.2°F), and a fairly moist mid-level environment. However, wind shear is expected to increase after 72 hours as 98L moves northeastward. The exact intensity of 98L, if development occurs, remains uncertain, but the environment looks favorable after the next 24 hours when it moves away from the Florida Peninsula.

Invest 99L could become 2019’s first cyclone in the deep tropical Atlantic

The Atlantic basin is still yet to have a tropical cyclone form in the deep tropics south of 20°N, but that is likely to change in the next couple days. As of 18:00 UTC Friday, Invest 99L was located near 10.1°N 43.1°W, and was moving slowly westward. Maximum sustained winds were 25 knots (30 mph), with an estimated minimum pressure of 1012 mb. 99L has become much better organized since yesterday, with this morning’s ASCAT pass revealing a nearly closed but still broad circulation.

Aside from dry mid-level air (400-700mb relative humidity values below 50%), environmental conditions are expected to be quite favorable for 99L to gradually develop over the next few days. The 18z SHIPS model predicted that 99L would be in a low-shear environment with sea surface temperatures above 28°C (82.4°F) for the next five days. The GFS model is the most aggressive with 99L, developing it into a strong tropical storm. The ECMWF model is very weak with 99L, but it often struggles with small Atlantic cyclones in the deep tropics. The UKMET model does not currently develop 99L at all. The Lesser Antilles should monitor the progress of 99L over the next several days.