Tropical Storm Fiona Expected to Strengthen in the Central Atlantic

August 17,2016
Tropical Depression Six developed enough thunderstorm activity on Wednesday afternoon to become Tropical Storm Fiona.

Infrared Satellite Image

Here is the latest status from the National Hurricane Center:

• Tropical Storm Fiona was located nearly 1,000 miles west of the Cabo Verde Islands, as of Wednesday night.
• Fiona is moving toward the west-northwest around 16 mph.
• The storm is forecast to intensify over the next day or two, but is not expected to become a hurricane.

(MORE: Hurricane Central)

Current Storm Status

Forecast Uncertainty

As our forecast path shows, this system will continue heading northwest into the central Atlantic Ocean during the next five days and is no threat to land.

Projected Path

Although some strengthening is expected, it faces a familiar pair of nemeses later in the week.
First, the system is expected to face increased wind shear, namely, differing winds aloft compared to near the surface, roughly near or just the halfway point between Africa and the Lesser Antilles.

Current Satellite, Wind Shear in the Atlantic

Wind shear tends to displace a tropical system's convection from its center of circulation and can also tilt that circulation. While some intense hurricanes can fend off some light to moderate wind shear, weaker systems can be ripped apart if the shear is too strong.
(MORE: Hurricane Season Outlook Update)
The increased southwest winds aloft responsible for the anticipated wind shear, along with a fairly weak Bermuda-Azores high will also cause the system to gain too much latitude to ever be a threat to the Lesser Antilles.
Dry air in the central Atlantic could also wrap into the system, encouraging stronger thunderstorm downdrafts and dispersing the convection from the system's center.

Satellite Image: Where the Dry and Moist Air Is

The uncertainty in the forecast lies in the potential for it to be either:
1) Weakened quickly by wind shear and dry air, degenerating into a remnant low or tropical wave and thus moving farther south (but still generally north of the Antilles)
2) Somehow holding together as a tropical cyclone and, thus, curling faster to the north into the central Atlantic Ocean.
Regardless of the scenario, this system is not a major threat to the Lesser Antilles at this time. If scenario 1 verifies, and the system degrades to a tropical wave, there could be a few more showers in the Leeward Islands early next week on the southern end of that tropical wave.
This is another sign that we're headed into the climatologically most active time of the Atlantic hurricane season.
(MORE: When Atlantic Season Peak Arrives)
This time of year, you can see tropical waves, also known as African easterly waves, lined up over Africa south of the Sahara Desert, ready to emerge into the eastern Atlantic Ocean.
A fraction of these tropical waves serve as the seed for an Atlantic basin tropical storm or hurricane each season.

Africa Infrared Satellite

So, while this latest Atlantic system may not pose a significant threat to land, that may not be the case with subsequent tropical waves in the heart of the hurricane season.
Tropical Depression Six formed late Tuesday night in the central Atlantic Ocean and strengthened into Tropical Storm Fiona by Wednesday evening. Check back with us at weather.com for the latest on this system and any other systems during the hurricane season.

MORE: Retired Atlantic Hurricane Names