Subtropical Storm Ernesto formed west of the Azores on Wednesday morning. At 11:00 a.m. EDT on Wednesday the center of Subtropical Storm Ernesto was located at latitude 38.1°N and longitude 46.0°W which put it about 695 miles (1120 km) southeast of Cape Race, Newfoundland. Ernesto was moving toward the north at 8 m.p.h. (13 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 1008 mb.
More thunderstorms formed closer to the center of a low pressure system west of the Azores on Wednesday morning and the National Hurricane Center designated the system as Subtropical Storm Ernesto. Several bands of showers and thunderstorms wrapped around the eastern and northern portions of the circulation. Bands northwest of the center of Ernesto consisted primarily of showers and lower clouds. The circulation may have been transporting some cooler, drier, more stable air into that part of the circulation. Showers and thunderstorms around the center of Ernesto were generating upper level divergence which was pumping mass away to the northeast of the subtropical storm.
Subtropical Storm Ernesto will move through an environment that could support some intensification during the next day or so. Ernesto will move over water where the Sea Surface Temperature is near 26°C. It will move through a region where the upper level winds are not too strong and there will not be much vertical wind shear. Subtropical Storm Ernesto could strengthen during the next 12 to 24 hours. Ernesto will move over cooler water later on Thursday and it will start to weaken. An upper level trough east of the U.S. will approach Subtropical Storm Ernesto from the west. Southwesterly winds ahead of the trough will cause more vertical wind shear and Ernesto could make a transition to an extratropical cyclone.
The southwesterly winds ahead of the upper level trough will steer Subtropical Storm Ernesto in a general northeasterly direction. On its anticipated track Subtropical Ernesto will pass between the Azores and Greenland.
Former Subtropical Storm Debby made a transition to a tropical storm on Wednesday. At 11:00 a.m. EDT on Wednesday the center of Tropical Storm Debby was located at latitude 41.2°N and longitude 48.3°W which put it about 1150 miles (1855 km) west-northwest of the Azores. Debby was moving toward the northeast at 12 m.p.h. (19 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 1003 mb.
The structure of former Subtropical Storm Debby changed on Wednesday and it exhibited the characteristics of a tropical storm. More thunderstorms formed around the center of circulation and those thunderstorms rose higher into the atmosphere. Additional bands of showers and thunderstorms developed and revolved around the core of the circulation. Storms near the core began to generate upper level divergence. The strongest winds occurred closer to the center of circulation. The National Hurricane Center designated Debby as a tropical storm based on information from satellites.
Tropical Storm Debby will move into an environment unfavorable for a tropical storm during the next 24 to 48 hours. Debby was over water where the Sea Surface Temperature was near 26°C, but it will soon move over much cooler water. It will start to weaken when it moves over the cooler water. It could take several days for the circulation around Tropical Storm Debby to spin down.
Tropical Storm Debby will be steered toward the northeast as it moves between an upper level trough to the west and an upper level ridge to the east. On its anticipated track Tropical Storm Debby will move between the Azores and Greenland.
Subtropical Storm Debby formed over the North Atlantic Ocean west of the Azores on Tuesday morning. At 11:00 a.m. EDT on Tuesday the center of Subtropical Storm Debby was located at latitude 38.9°N and longitude 48.5°W which put it about 1160 miles (1870 km) west of the Azores. Debby was moving toward the north 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 1008 mb.
A surface low pressure system revolved around the western side of an upper level low over the North Atlantic Ocean during the past few days. More bands of showers and thunderstorms developed around the surface low on Tuesday morning and its circulation become more circular. The National Hurricane Center designated the low pressure system as Subtropical Storm Debby based on satellite imagery. The strongest winds were occurring in a rainband that wrapped around the northern side of the circulation. Bands south of the center of circulation consisted primarily of showers and lower clouds.
Subtropical Storm Debby will move through an environment somewhat favorable for intensification during the next 24 hours. Debby will move over water where the Sea Surface Temperature is between 26°C and 27°C. Subtropical Storm Debby will move between an upper level trough to its west and an upper level ridge to its east. The trough and ridge will produce southeasterly winds which will cause moderate vertical wind shear. Subtropical Storm Debby could strengthen during the next 24 hours. Debby will move over much colder water in about 36 hours and then it will weaken.
The upper level ridge and trough will steer Subtropical Storm Debby in a mainly northerly direction. On its anticipated track Subtropical Storm Debby will remain west of the Azores.
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.
Tropical Storm Alex weakened to just below hurricane intensity as it moved across the Azores on Friday morning. At 10:00 a.m. EST the center of Hurricane Alex was located at latitude 39.3°N and longitude 27.0°W which put it about 35 miles north of Terceira in the Azores. Alex was moving toward the north at 28 m.p.h. (44 km/h). The maximum sustained wind speed was 70 m.p.h. (115 km/h) and there were wind gusts to 85 m.p.h. (135 km/h). The minimum surface pressure was 986 mb.
It appears that the center of Tropical Storm Alex made landfall on the island of Terceira. Weather stations on Santa Maria and Sao Miguel have measured tropical storm force winds. However, it seems like the core of Tropical Storm Alex which contains the strongest winds remained over water. Higher wind speeds most likely occurred on the windward sides of mountains in the Azores.
In anticipation of the movement of Tropical Storm Alex away from the islands all Hurricane Warnings and Tropical Storm Warnings for the Azores have been discontinued.
Tropical Storm Alex is over water where the Sea Surface Temperature is near 16°C. It will move over even cooler water and Alex will soon be unable to extract enough energy from the ocean to sustain the structure of a tropical cyclone. The structure of Alex will gradually change to the structure of a cold core extratropical cyclone during the next several days. It is likely to maintain much of its intensity as it moves through the extratropical transition.
An upper level trough is steering Tropical Storm Alex toward the north-northwest and a general northwesterly motion is expected to continue for the next two or three days. Tropical Storm Alex could end up south of Greenland over the weekend as a strong extratropical cyclone.
A low pressure system over the eastern Atlantic Ocean has been classified as Subtropical Storm Alex by the National Hurricane Center. At 4:00 p.m. EST on Wednesday the center of Subtropical Storm Alex was located at latitude 27.1°N and longitude 30.8°W which put it about 785 miles (1260 km) south-southwest of the Azores. Alex was moving toward the northeast at 14 m.p.h. (23 km/h). The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h). The minimum surface pressure was 990 mb.
Subtropical Storm Alex evolved out of an extratropical cyclone that formed off the southeastern coast of the U.S. late last week. The extratropical cyclone cycled through the typical stages exhibited by low pressure systems in the middle latitudes as it moved eastward across the central Atlantic Ocean. It eventually became an occluded extratropical cyclone over that region. The low pressure system moved south on Tuesday, which placed it over slightly warmer Sea Surface Temperatures (SSTs). As it began to extract more energy from the warmer ocean, the fronts attached to the low pressure system began to dissipate. The low began to take on a more circular shape and convection began to intensify around the center of circulation. A more circular shape with no fronts and taller clouds prompted the National Hurricane Center to classify the low as a subtropical storm.
A subtropical storm is a hybrid low with some characteristics of a tropical cyclone (circular shape and no fronts) and some characteristics of an extratropical cyclone (cooler air aloft). Subtropical Storm Alex has a well organized low level circulation. There is a clear area in the center that looks a little like the eye of a hurricane. The center is surrounded by a ring of taller clouds. Spirals bands of clouds are rotating around the core of the circulation. However, the vertical structure is different from a tropical cyclone. Subtropical Storm Alex is under an upper level trough and the upper level divergence is limited. Also, the clouds in Alex are not growing as tall as the clouds in a tropical cyclone.
The environment around Subtropical Storm Alex would normally be considered to be unfavorable for intensification of a tropical cyclone. The SSTs are near 23.5°C. However, since Alex is near the center of an upper level trough, there is not much vertical wind shear. So, there could be a chance for some intensification during the next 24 hours. Subtropical Storm Alex will move over cooler SSTs and it is likely to make a transition back to an extratropical cyclone in two or three days.
The upper level trough is steering Alex toward the northeast and a general northward motion is expected to continue for the next several days. On its anticipated track Subtropical Storm Alex could approach the Azores in about 36 hours. It could bring strong winds and locally heavy rain when it moves over the Azores.
Subtropical Storm Alex is the first tropical or subtropical cyclone to form over the North Atlantic Ocean in January since 1978. It is only the fourth tropical or subtropical cyclone on record to form over the Atlantic Ocean in January since 1851.