The Eastern North Pacific basin continues to be active tropically. Tropical Depression Six-E formed west of Mexico on Tuesday. At 11:00 p.m. EDT on Tuesday the center of Tropical Depression Six-E was located at latitude 12.2°N and longitude 109.9°W which put it about 740 miles (1190 km) south of the southern tip of Baja California. It was moving toward the west at 12 m.p.h. (19 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. (75 km/h). The minimum surface pressure was 1007 mb.
A center of circulation consolidated within a large area of thunderstorms south of Baja California on Tuesday. A primary band of showers and thunderstorms wrapped around the western and southern sides of the center of circulation. Additional bands of showers and thunderstorms were beginning to form north and west of the center. There were not many showers and storms in the eastern half of the circulation. The thunderstorms near the core of the circulation were beginning generate upper level divergence which was pumping away from depression.
Tropical Depression Six-E will move through an environment that will be favorable for intensification. It will move over water where the Sea Surface Temperature (SST) is near 29°C. Tropical Depression Six-E is near the western end of an upper level ridge and the upper level winds are relatively weak. Warm SSTs and little vertical wind shear should allow the depression to strengthen during the next several days. Tropical Depression Six-E is likely to become a tropical storm on Wednesday and it could become a hurricane later this week.
Tropical Depression Six-E is moving south of a subtropical ridge which is steering the depression toward the west. The subtropical ridge is expected to continue to steer the depression toward the west during the next few days. On its anticipated track the depression is expected to move away from the coast of Mexico.
Tropical Depression Six intensified on Wednesday and the National Hurricane Center named it Tropical Storm Fiona. At 5:00 p.m. EDT on Wednesday the center of Tropical Storm Fiona was located at latitude 15.1°N and longitude 37.8°W which put it about 1545 miles (2490 km) east of the Leeward Islands. Fiona was moving toward the northwest at 16 m.p.h. (26 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1006 mb.
Tropical Storm Fiona has a small circulation and winds to tropical storm force only extend out about 25 miles (40 km) from the center circulation. Most of the thunderstorms are occurring close to the center of circulation. Those thunderstorms are generating some upper level divergence, but it does not extend very far from the core of Tropical Storm Fiona. There are bands of lower clouds and showers rotating around the core of Fiona.
Tropical Storm Fiona is moving through an environment that is mostly favorable for intensification. It is moving over water where the Sea Surface Temperature is near 27°C. An upper level ridge north of Fiona is generating northeasterly winds which are blowing across the top of the tropical storm. Those winds are causing some vertical wind shear, but it should only inhibit, but not stop, intensification. There is drier air northwest of Fiona and that is the main negative factor in the environment. If the drier air gets pulled into the core of Tropical Storm Fiona, it will reduce the supply of energy and weaken Fiona. Since the core of Fiona is so small, the tropical storm could intensify or weaken very quickly as the environmental conditions change.
The subtropical high that extends from Africa across the Atlantic Ocean is splitting into an eastern ridge and a western ridge. Tropical Storm Fiona is moving toward the weakness where the split is occurring. This is producing a motion toward the northwest and that general motion is expected to continue during the next several days. On its anticipated track Tropical Storm Fiona could be northeast of the Leeward Islands in a few days.
A center of circulation developed within a tropical wave designated as Invest 98L on Tuesday and the National Hurricane Center classified the system as Tropical Depression Six. At 11:00 p.m. EDT on Tuesday the center of Tropical Depression Six was located at latitude 12.6°N and longitude 34.1°W which put it about 1800 miles (2900 km) east of the Leeward Islands. The depression was moving toward the northwest at 14 m.p.h. (22 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 1008 mb.
The circulation of Tropical Depression Six is still organizing. A center of circulation exists near the surface and thunderstorms are developing near the center. Several partial spiral bands are beginning to form. The thunderstorms near the center are generating a small region of upper level divergence, but the divergence is occurring mainly to the southwest of the depression.
Tropical Depression Six is moving through an environment that favors intensification. It is moving over water where the Sea Surface Temperature is near 27°C. An upper level ridge to the north is causing northeasterly winds to blow across the top of the depression. There is some vertical wind shear, but the shear will only slow the rate of intensification. The shear is not strong enough to prevent intensification and Tropical Depression Six is expected to become a tropical storm during the next day or two.
The subtropical ridge over Africa and the Atlantic Ocean is splitting into two parts and Tropical Depression Six is moving toward the northwest into the split that is developing. The depression is expected to continue to move toward the northwest in the short term. The longer term motion will depend on how strong Tropical Depression Six becomes. If it intensifies more and develops a taller circulation, then the depression will be steered by the winds higher in the atmosphere. The winds at those levels are more likely to carry it into the central Atlantic Ocean. However, if vertical wind shear weakens the depression and the circulation is shallower, then the winds in the lower levels of the atmosphere could carry the depression farther to the west. In either case Tropical Depression Six is no immediate threat to any land area.
An area of low pressure organized quickly after it moved off the coast of West Africa and the National Hurricane Center designated it as Tropical Storm Fred. At 2:00 p.m. EDT on Sunday the center of Tropical Storm Fred was located at latitude 14.1°N and longitude 20.7°W which put it about 195 miles (315 km) east-southeast of Praia in the Cape Verde Islands. Fred was moving toward the northwest at 16 m.p.h. (26 km/h). The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h). The minimum surface pressure was 1000 mb. A Hurricane Warning has been issued for the Cape Verde Islands.
Tropical Storm Fred was a well organized low pressure system when it moved over the eastern Atlantic Ocean from West Africa. The input of energy from the ocean enhanced the existing thunderstorms and the low pressure system quickly reached the intensity necessary to be classified as a tropical storm. The circulation continued to organize further on Sunday. A primary rainband has wrapped almost entirely around the center of circulation. A small eye and an eyewall may be forming and other spiral bands of thunderstorms are developing. The thunderstorms are generating upper level divergence which is pumping out mass. Fred is moving over water where the Sea Surface Temperatures (SSTs) are near 27°C to 28°C. The winds in the upper levels are relatively light and there is not much vertical wind shear. The favorable environmental conditions are allowing Fred to intensify rapidly and it could become a hurricane tonight. As Fred moves farther toward the northwest, it will start to move over cooler SSTs and into a region where there is more vertical wind shear. As a result, Fred is likely to weaken back to tropical storm intensity later this week.
There is a weaker area in the subtropical ridge over the Atlantic Ocean and Fred is moving northwest toward that area. The ridge is expected to strengthen during the week and as it strengthens it will cause Fred to move more toward the west. On its anticipated track Fred will reach the Cape Verde Islands in about 12 hours. It could bring strong winds and heavy rain when it move across those islands.