Tag Archives: Invest 90L

Invest 90L Organizing North of Panama

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.

Invest 90L Meandering Over Southwest Caribbean Sea

An area of low pressure designated as Invest 90L has meandered over the southwestern Caribbean Sea during the past several days.  At 7:00 p.m. EST on Thursday the center of Invest 90L was located at latitude 12.3°N and longitude 81.3°W which put it about 170 miles (275 km) east of Bluefields, Nicaragua.  Invest 90L was moving toward the west at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 25 m.p.h. (40 km/h) and there were wind gusts to 35 m.p.h. (55 km/h).  The minimum surface pressure was 1006 mb.

Invest 90L consists of a broad area of low pressure over the southwestern Caribbean Sea.  There is a definite area of counterclockwise rotation, but the is no well defined core at the center of the low.  There is a swirl of low clouds and showers at the center of Invest 90L, but there are no thunderstorms near the center.  Thunderstorms form and dissipate in bands around the periphery of the circulation.

The environment around the southwestern Caribbean Sea is not as favorable for the development of a tropical cyclone as it was earlier this week.  Invest 90L is moving over water where the Sea Surface Temperature is near 29°C.  However, northerly winds blowing across the Gulf of Mexico have transported drier air over the northwestern Caribbean Sea.  The drier air has not reached Invest 90L, but the drier air is just to the northwest of the low pressure system.  An upper level trough over the Gulf of Mexico is producing southwesterly winds which are blowing over the top of Invest 90L.  Those winds are generating moderate vertical wind shear which is inhibiting the organization of the low pressure system.  Even with the inhibiting factors the National Hurricane Center is indicating that the probability of the formation of a tropical cyclone during the next five days is 70%.

The fact that there is only a low level circulation means that Invest 90L is being steering by winds closer to the surface.  The winds in the lower levels have been pushing the low pressure system very slowly toward the west.  Guidance from numerical models suggests that Invest 90L could meander over the southwestern Caribbean Sea for several more days.