Tag Archives: Invest 96L

Possible Tropical Development

The National Hurricane Center (NHC) is monitoring two tropical disturbances which are designated Invest 96L and Invest 97L for possible development into tropical cyclones.

At 8:00 p.m. EDT on Thursday the center of Invest 97L was located at latitude 13.4°N and longitude 37.0°W which put it about 1525 miles (2460 km) east-southeast of the Leeward Islands.  Invest 97L was moving toward the west at 21 m.p.h. (34 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 1011 mb.

At 8:00 p.m. EDT on Thursday the center of Invest 96L was located at latitude 11.2°N and longitude 20.9°W which put it about 320 miles (515 km) south-southeast of the Cape Verde Islands.  Invest 96L was moving toward the west-northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1010 mb.

Invest 97L consists of a fast moving tropical wave over the central Atlantic Ocean.  The circulation of Invest 97L is not well organized.  A few thunderstorms are occurring near the northern part of the axis of the tropical wave, but convection is scattered.  The rapid forward motion of the wave is preventing the thunderstorms from consolidating around a center of circulation.

If the forward speed of Invest 97L slows, then it may move into an environment that is more favorable for the development of a tropical cyclone.  It is over water where the Sea Surface Temperature (SST) is near 27°C and it will move over warmer water as it gets closer to the Caribbean Sea.  There is not much vertical wind shear except for the low level shear created by the rapid forward motion of the wave.  There is drier air to the north of Invest 97L, but it is embedded in the moister air closer to the Equator.  NHC has a 30% probability that Invest 97L will develop into a tropical cyclone during the next five days.  As a result, NHC has tentatively tasked a plane to fly reconnaissance into Invest 97L on Saturday if it shows signs of developing as it approaches the Caribbean Sea.

Invest 96L also consists of a tropical wave, but it is more well organized than Invest 97L  There are numerous thunderstorms west of the center of circulation and some rainbands are developing south of the center of circulation.  The thunderstorms west of the center are starting to generate some upper level divergence to the west of Invest 96L.  There are some indications that a low level center of circulation may be forming.

Invest 96L is currently in an environment that is mostly favorable for further development.  It is moving over water where the SSTs are near 28°C.  An upper level ridge north of Invest 96L is causing easterly winds to blow over the top of it.  The vertical wind shear is moderate and shear is the primary factor slowing the organization of the Invest 96L.  NHC has a 40% probability that Invest 96L will develop into a tropical cyclone during the next five days.

Because it is more well organized and it is moving more slowly, Invest 96L has a better chance for developing into a tropical cyclone during the next two days.  However, Invest 96L could move into a less favorable environment after that time.  Invest 97L will be moving into a more favorable environment during the weekend.  If Invest 97L holds together until its forward speed slows, then it could have a better chance of developing in several days.  If Invest 97L becomes a tropical cyclone it could threaten portions of the Caribbean Sea.

Update on Invest 96L

A tropical disturbance approaching the Lesser Antilles was designated Invest 96L by the National Hurricane Center (NHC).  The disturbance appears to consist of a tropical wave, a broad surface low centered east of Guadaloupe and a small cyclonic meso-vortex rotating around the northeastern portion of the broader low pressure system.  The overall system is moving toward the west-northwest at 21 m.p.h.  There appears to be a broad area of light winds within the surface low and stronger winds on the north side of the small meso-vortex.  A reconnaissance aircraft did find winds to tropical storm force on the north side of the system, but it also reported that the overall circulation was poorly defined.

This disturbance has a complicated origin which is linked to its slow development.  The disturbance originally consisted of two tropical waves moving north of a broad but weak low pressure system located within the Intertropical Convergence Zone/monsoon trough.  The complex structure inhibited the development of a dominant center of circulation and several clusters of thunderstorms have produced small meso-vortices like the one mentioned previously.  It appears that there has been a slight increase in organization today as the broad area of low pressures appears to have a more symmetrical shape.  It is unclear if an upper low to the northwest of the system is creating wind shear over the top of it.

NHC is giving a 70% chance that a tropical cyclone will form out of this system within the next five days.  As broad low pressure system moves west-northwest it will affect the weather over the northeastern Caribbean Sea during the next several days.  Another reconnaissance aircraft is scheduled to investigate the disturbance tomorrow afternoon, if necessary.

 

Possible Tropical Development

For the first time this hurricane season the Global System Forecast (GFS) Model is suggesting a classical development of a tropical cyclone east of the Lesser Antilles might occur and that resulting storm could effect the U.S.  A tropical wave is about 600 miles east of the Lesser Antilles and there may be a low pressure center near latitude 10°N and longitude 50°W.  Thunderstorm activity has increased with this system today as it moves westward.

The 0600 UTC run of the GFS model developed a tropical cyclone from this wave and moved it through the Caribbean Sea and into the Gulf of Mexico near Texas by a week from Friday.  The following (1200 UTC) run also developed a tropical cyclone and moved it into the northern Gulf of Mexico by a week from Wednesday evening.  At this time it is prudent to ask if these runs represent model false alarms or a possible depiction of future reality.  If the development of a tropical cyclone does occur, then it may be that a hurricane could approach the coast of the U.S. during the second half of next week.  The first indication that the GFS forecast might verify would be the development of tropical depression east of the Lesser Antilles.

This far out in advance the uncertainty of a track or intensity forecast is very high.  If there was a cone of uncertainty for the track, it might extend from Cancun to Cape Hatteras.  If a center of low pressure organizes, then the model guidance will improve and the uncertainty will decrease.

People along the coast of the U.S. should be aware of this system and maintain a cautious vigilance until we see if it does develop,