Tag Archives: Greenland

Hurricane Gert Intensifies to Cat. 2 South of Nova Scotia

Hurricane Gert intensified to Category 2 on the Saffir-Simpson Scale as it sped over the Gulf Stream south of Nova Scotia on Wednesday afternoon.  At 5:00 p.m. EDT on Wednesday the center of Hurricane Gert was located at latitude 38.7°N and longitude 62.4°W which put it about 410 miles (665 km) south of Halifax, Nova Scotia.  Gert was moving toward the northeast at 31 m.p.h. (50 km/h).  The maximum sustained wind speed was 100 mp.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 970 mb.

Although Hurricane Gert is at a fairly high latitude, it has the classic structure of a Hurricane.  There is a fairly small eye at the center of circulation.  The eye is surround by a ring of strong thunderstorm and the strongest winds are occurring in this ring of thunderstorms.  There are additional bands of showers and thunderstorms revolving around the core of the hurricane.  The circulation is symmetrical and thunderstorms in the core are producing upper level divergence which is pumping away mass to the northeast of the hurricane.  Winds to hurricane force extend out about 40 miles (65 km) primarily to the east of the center of circulation.  Winds to tropical storm force extend out about 140 miles (225 km) from the center.

Hurricane Gert is moving over the Gulf Stream which means it is moving over water where the Sea Surface Temperature (SST) is near 28.5°C.  An upper level trough west of Gert is producing southwesterly winds which are blowing toward the top of the hurricane.  However, there is not much change of wind speed with height, which means that there is little vertical wind shear.  The combination of the warm water of the Gulf Stream and little vertical shear, allowed Hurricane Gert to strengthen on Wednesday.

Hurricane Gert could intensify during the next few hours, but it will soon move into a much less favorable environment.  Gert will soon move north of the Gulf Stream where the SSTs are much cooler.  The upper level trough is moving closer to Hurricane Gert and the winds are the upper level are forecast to get stronger.  When those winds increase, there will be much more vertical wind shear.  Colder water and more wind shear will cause Hurricane Gert to weaken on Thursday.  Gert could make a transition to an extratropical cyclone in colder environment of the North Atlantic.

Southwesterly winds in the upper level trough are steering Hurricane  Gert quickly toward the northeast and that general motion is expected to continue.  On its anticipated track, Hurricane Gert will move south of Labrador and Greenland.

Even as Hurricane Gert speeds away over the North Atlantic three new tropical waves over the tropical Atlantic have the potential to develop into tropical cyclones.  A tropical wave about 800 miles (1290 km) east of the Lesser Antilles designated as Invest 91L showed signs of organization on Wednesday.  A few more thunderstorms developed closed to the center of circulation.  A reconnaissance plane is scheduled to investigate this system on Thursday.  A little farther to the east another tropical wave designated Invest 92L was also showing evidence or more organization.  A third tropical wave just west of Africa also has the potential to develop during the next few days.

Tropical Storm Alex Brings Wind and Rain to the Azores

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.