The structure of the low pressure system designated as Invest 90L became better organized on Saturday over the southwestern Caribbean Sea north of Panama. At 7:00 p.m. EDT on Saturday the center of Invest 90L was located at latitude 10.8°N and longitude 80.9°W which put it about 220 miles (355 km) east-southeast of Bluefields, Nicaragua. Invest 90L was moving toward the east at 3 m.p.h. (5 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (70 km/h). The minimum surface pressure was 1006 mb.
More thunderstorms developed closer to the center of circulation on Saturday. A band of stronger thunderstorms formed south of the center and a second band of storms developed northeast of the center. Other rainbands appeared to be forming in other areas of the circulation. Storms in the band northeast of the center began to produce upper level divergence that was pumping mass away. An improved convective structure could be a indication that Invest 90L is developing into tropical depression.
The atmospheric environment became more favorable for tropical development on Saturday. Upper level southwesterly winds which were blowing across the top of the low pressure system weakened on Saturday and the vertical wind shear lessened. Less shear allowed more thunderstorms to develop and persist. Since Invest 90L has meandered over the same part of the southwestern Caribbean Sea for several days, it has mixed slightly cooler water to the surface. However, the water in that part of the Caribbean Sea is very warm and Invest 90L is moving over water where the Sea Surface Temperature is still near 29°C. The environment is favorable for development of a tropical cyclone and Invest 90L could become a tropical depression or a tropical storm at any time.
Invest 90L is located underneath an upper level ridge and the steering currents are weak. The low pressure system drifted toward the east on Saturday and some models are suggesting that Invest 90L could make a slow counterclockwise loop over the southwestern Caribbean Sea during the next few days.