98L may develop next week; 97L not a threat to land

A tropical wave located about 1000 miles east of the Lesser Antilles Islands (Invest 98L) has a large amount of disorganized heavy thunderstorms, and is headed west-northwest at about 15 mph. Wind shear is a light to moderate 5 - 15 knots over 98L, the atmosphere is moist, and ocean temperatures are a very warm 29°C. With wind shear expected to remain in the moderate range through Wednesday morning, some slow development is likely until 98L encounters much higher wind shear of 20 - 35 knots Wednesday night though Friday. This shear will be due to an upper-level trough of low pressure centered a few hundred miles northeast of the Lesser Antilles Islands. Moisture from 98L could arrive in the Lesser Antilles Islands as early as Thursday night. Wind shear may drop to levels capable of allowing 98L to develop into a tropical depression by Saturday, as predicted by the NOGAPS model. The GFS model predicts shear will remain high until early next week. The GFS develops 98L into a tropical depression on Tuesday, a few hundred miles northeast of the northernmost Lesser Antilles Islands. In their 8 am Tropical Weather Outlook, NHC gave 98L a 20% chance of becoming a tropical cyclone by Thursday morning. The long range fate of 98L is uncertain; the ECMWF model shows 98L coming close to the U.S. East Coast in ten or so days, while the other models keep 98L far out to sea.


Figure 1. Morning satellite image of Invest 98L headed towards the Lesser Antilles Islands.

97L near the Bahamas little threat to develop
A tropical disturbance a few hundred miles northeast of the Bahama Islands (Invest 97L) has a moderate amount of disorganized heavy thunderstorms, and is headed northeast at about 10 mph. Satellite loops show that heavy showers from 97L are affecting portions of the Southeast Bahama Islands, and this activity will continue today. Wind shear is a moderate 15 - 20 knots over 97L, but is expected to rise to the high range, 20 - 30 knots, on Tuesday night. This high shear should prevent 97L from developing as it heads northeastwards out to sea. In their 8 am Tropical Weather Outlook, NHC gave 97L a 10% chance of becoming a tropical cyclone by Thursday morning. Rains from 97L will not affect the U.S.

Jeff Masters