Saturday's afternoon forecast from the National Hurricane Center reported the second system being watched in the Atlantic, Invest 99, developed into Tropical Depression #6.
The NHC continued watching four other systems currently in the Atlantic, Caribbean Sea and Gulf of Mexico, all showing a variety of levels of development.
The former Invest 99 now Tropical Depression 6:
Visible imagery has shown a partially-exposed, well-defined low-level circulation for the past several hours. Infrared imagery has also shown deep convection persisting east of the center with cold cloud tops of less than -85 degrees C.
Therefore, the system now meets the necessary requirements to be classified as a tropical cyclone.
Models indicate that the depression is currently in a relatively hostile environment with a strong deep-layer vertical shear and mid-level relative humidities near 40 percent. These conditions are not expected to change much and global models suggest this will be a short-lived depression.
Simulated satellite imagery shows a few bursts of deep convection sheared away by 48 hours. The official forecast shows a steady-state depression through 36 hours that degenerates to a remnant low in 48 hours, and dissipates by 60 hours. This prediction is near the various consensus model guidance.
The depression is moving west-northwestward at 14 knots. It is currently being steered by a narrow low-level ridge to its north.
The system is expected to turn more westward and slow in forward speed over the next day or so followed by a slight bend back to the west-northwest on day 2. The NHC track forecast is near the simple and corrected model consensus aids, and leans towards a more southerly track.
1. Eastern Tropical Atlantic (AL98):
Shower and thunderstorm activity continues in association with a broad area of low pressure located several hundred miles west of the Cabo Verde Islands. Environmental conditions appear generally favorable for further development of this system, and a short-lived tropical depression is likely to form this weekend while it moves west-northwestward or northwestward at about 10 mph across the eastern tropical Atlantic. By early next week, upper-level winds over the system are forecast to increase, and further development is not expected.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 7 days...high...70 percent.
3. East-Southeast of the Lesser Antilles (AL90):
A broad area of low pressure has formed near the Windward Islands, shower and thunderstorm activity has become better organized since yesterday. Some additional development of this system is likely and a tropical depression could form by early next week while this system moves westward to west-northwestward at 10 to 15 mph, across the Lesser Antilles and over the eastern and central Caribbean Sea.
Regardless of development, heavy rainfall is possible over portions of the Windward Islands during the next couple of days. Interests in the eastern and central Caribbean should monitor the progress of this system.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 7 days...medium...60 percent.
4. Western Gulf of Mexico:
An area of disturbed weather located near the northwestern and central Bahamas is expected to move into the Gulf of Mexico by early next week, where a broad area of low pressure is expected to form.
Some slow development of this system is possible thereafter, and a tropical depression could form as it moves westward and approaches the western Gulf of Mexico coastline by the middle of next week.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 7 days...medium...50 percent.
5. Near the coast of Africa:
A tropical wave located near the western coast of Africa is producing a large area of disorganized showers and thunderstorms.
Some slow development is possible while it moves generally west-northwestward across the tropical eastern Atlantic during the next several days.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...20 percent.
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