From AL.COM

By Leigh Morgan

Tropical Storm Grace was expected to move westward for the next few days toward the Caribbean. (National Hurricane Center)

There’s a new tropical storm deep in the Atlantic, and it could be on a path for the Caribbean — if it survives that long.

Tropical Storm Grace was located in the eastern Atlantic, about 285 miles south-southwest of the Cape Verde Islands as of 4 p.m. CDT Saturday, according to the National Hurricane Center.

Grace had winds of 40 mph and was moving westward at 14 mph.

The hurricane center thinks that Grace could strengthen some, but at this point forecasters don’t think it will become a hurricane.

Tropical Storm Grace could get a bit stronger in the short term but is expected to weaken or even dissipate before it gets close to the United States. (NOAA)
Grace will be moving through an environment with low wind shear and warm sea surface temperatures for the next 36 hours or so. Forecasters will be watching to see if dry air in the mid-levels of the atmosphere will affect the storm and keep it from strengthening.

After 48 hours or so the hurricane center said Grace will be entering an area with more wind shear, which could be strong enough to kill off the storm entirely in four or five days.
Grace is the seventh named storm of 2015 in the Atlantic.

The hurricane center was also monitoring the progress of Tropical Depression Fred, which was located more than a thousand miles south of the Azores on Saturday afternoon.

Fred moved over the Cape Verde Islands last Monday as a hurricane — the first on record to strike the islands.

For more on this story go to: http://www.al.com/news/index.ssf/2015/09/could_atlantic_have_tropical_s.html

Related story:

In Eastern Atlantic, Grace intensifies while Fred clings to Life

By Bob Henson From Weather Underground

Tropical Storm Grace became the Atlantic’s seventh named storm of the 2015 tropical season on Saturday. Grace’s arrival keeps this year’s pace of named Atlantic storms close to the long-term average: during the period 1966-2009, the average date of formation for the sixth named storm was September 8. With top sustained winds of 45 mph as of 11:00 am EDT Sunday, Grace was moving just north of due west at about 14 mph through the eastern Atlantic, about 450 miles west-southwest of the Cape Verde islands. Grace took advantage of the typical nighttime surge in tropical cyclone convection to build a north-south swath of heavy thunderstorms around its center. The convection has ebbed somewhat in intensity over the last few hours, but Grace remains quite well structured in visible satellite imagery, though its convective envelope remains elongated.

Over the next couple of days, Grace will move over sea-surface temperatures of 27-28°C (80-82°F), slightly above average for this time of year. Wind shear will be relatively light beneath a weak upper-level ridge. The National Hurricane Center projects Grace to become a strong tropical storm by late Monday, and I’d put at least 50-50 odds on the likelihood of Grace making it to minimal hurricane status by Monday or Tuesday. Later in the week, as Grace moves west of 40°W, the storm will encounter an intensifying belt of southwesterly upper-level winds extending from the Caribbean into the central Atlantic. Vertical wind shear of more than 40 knots will develop, and Grace is likely to decay significantly as the shear disrupts its circulation and injects dry air into its core. NHC projects Grace to be no more than a minimal tropical storm by Thursday, as it approaches the Lesser Antilles.

Grace is the fourth storm this year to develop in the deep tropics of the eastern Atlantic–the Cape Verde development region, which can produce some of the longest-lived and most dangerous hurricanes to affect the United States. Getting so many Cape Verde storms this year is a bit surprising given the hostile conditions engendered by this year’s intensifying El Niño event, which is at record strength for early September. As noted by wunderground member Webberweather53, this is the first time that at least four named systems have developed east of latitude 60°W during a strong El Niño event. El Niño is responsible for hurricane-snuffing wind shear that has been at record levels for most of the summer over the Caribbean and nearby waters. It’s no coincidence that this year’s only two Atlantic hurricanes to date, Danny and Fred, both peaked in strength well east of the Lesser Antilles. Although Danny briefly reached Category 3 strength, the Atlantic has seen a total of only about 78 hours of hurricane activity between Danny and Fred. As a result, the Atlantic’s accumulated cyclone energy, or ACE–a measure of the longevity and strength of each year’s tropical cyclones–has reached a mere 20% of the typical end-of-season total. By comparison, the Northeast Pacific has already produced 32% more ACE than a typical season. El Niño typically favors the Northeast Pacific over the Atlantic in tropical cyclone activity.

Fred refuses to quit
Though it was given a terminal diagnosis days ago, Tropical Depression Fred has shown it isn’t quite ready to leave this mortal coil. Now in its seventh day as a tropical cyclone, Fred’s entire life has unfolded east of longitude 45°W. It became the first hurricane in modern records to pass through the Cape Verde islands, and over the last several days it’s survived in the face of persistent wind shear by generating new convection each time a batch of thunderstorms is sheared away from its center. Downgraded to a tropical depression on Saturday evening, Fred is beginning to interact with an upper-level trough to its northwest and should begin moving more rapidly to the northeast over the next several days, then begin curving back toward the southeast as the trough passes it by. Although the ECMWF model merges Fred with the trough, most other models indicate that Fred will get yet another lease on life over the next several days, as wind shear lessens somewhat. Fred will continue to travel over SSTs that are around 1°C (1.8°F) above average for at least the next five days, so it’s possible Fred could linger as a tropical depression or weak tropical storm throughout this week.

Another healthy wave coming off Africa
African continues to generate an impressive supply of easterly waves that have at least a chance of developing into tropical cyclones as they move into the Atlantic. Our next tropical wave is in the process of moving from West Africa into the Atlantic at a fairly low latitude (see Figure 1 above). SSTs remain unusually high in this region, and I expect we will see this wave emerge into a tropical depression and perhaps become Tropical Storm Henri late this week. Once again, the tendency for high wind shear from the Caribbean northeastward will greatly reduce the odds that any tropical cyclone from the deep Atlantic tropics might approach North America relatively intact.

IMAGES:

Figure 1. An infrared view of Tropical Storm Grace (center) and a significant wave moving into the Atlantic from Africa (far right), taken at 1515 GMT (11:15 am EDT) on Sunday, September 6, 2015. Image credit: UW-CIMMS

Figure 2. Disorganized convection associated with Tropical Depression Fred is shown in this enhanced infrared image from the GOES-East satellite at 1615 GMT (12:15 pm EDT) on Sunday, September 6, 2015. Image credit: NOAA/NESDIS.

Figure 3. Sea-surface temperatures (left) and departures from average for this time of year (right), both in degrees C, across the North Atlantic for the week ending on August 29, 2015.

For more on this story go to: http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=3103