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Hurricane Season 2011: Subtropical Storm Sean (Atlantic Ocean)
11.14.11
 
A visible image from GOES at 1445 UTC (9:45 a.m. EST) › View larger image
A visible image from GOES at 1445 UTC (9:45 a.m. EST) showed the clouds associated with the cold front that captured Sean far (right edge) to the eastern Atlantic.
Credit: NASA/NOAA GOES Project
Tropical Storm Sean Absorbed into a Cold Front Over Atlantic

The most recent tropical storm of the Atlantic Hurricane season was absorbed by a cold front early this past weekend.

On Friday, November 11 at 11 a.m. AST, Sean's maximum sustained winds were near 50 mph and it was moving to the northeast at 23 mph. At that time, Sean was just 125 miles (200 km) north-northeast of Bermuda, and a tropical storm warning was still affect for the island. Twelve hours Sean's winds lessened and the tropical storm sped up, which are two signs of a weakening tropical cyclone.

The National Hurricane Center noted on Friday, November 11, 2011 at 11 p.m. AST that Sean had officially merged with a cold front. Satellite imagery from NOAA's GOES-13 satellite shows the cold front moving through the northeastern Atlantic Ocean on November 14. A visible image from GOES at 1445 UTC (9:45 a.m. EST) showed the clouds associated with the cold front that captured Sean. The GOES image was created at NASA/NOAA's GOES Project at NASA's Goddard Space Flight Center, Greenbelt, Md.

At 11 a.m. AST on November 11, Sean was a tropical storm and had maximum sustained winds near 40 mph (65 kmh). Those tropical-storm force winds extended 175 miles from the center, so Sean was about 350 miles in diameter. Sean was 505 miles (815 km) northeast of Bermuda and speeding to the east-northeast at 35 mph (56 kmh). Sean was classified at that time as a post-tropical storm.

Late on Saturday, Sean dissipated and its energies became part of the cold front moving across the northern Atlantic Ocean.

Text credit: Rob Gutro
NASA's Goddard Space Flight Center/, Greenbelt, Md.



November 10, 2011

This 3-D image of Sean from the TRMM satellite was captured on Nov. 10, 2011 at 12:51 a.m. EST. › View larger image
This 3-D image from the TRMM satellite was captured on Nov. 10, 2011 at 12:51 a.m. EST. Thunderstorms around the edge of Sean's center of circulation were reaching to about 11km (~6.8 miles).
Credit: SSAI/NASA, Hal Pierce
This radar image of Tropical Storm Sean's rainfall was captured by TRMM on Nov. 10, 2011 at 12:30 a.m. EST. › View larger image
This radar image of Tropical Storm Sean's rainfall was captured by the TRMM satellite on Nov. 10, 2011 at 12:30 a.m. EST. Sean's northwestern quadrant were the most powerful where rainfall was occurring at a rate of more than 2 inches (50 mm) per hour (in red). The rest of Sean contained mostly scattered moderate to occasionally heavy rainfall, falling at a rate between .78 to 1.57 inches/20 to 40 mm per hour).
Credit: SSAI/NASA, Hal Pierce
NASA's TRMM Satellite Radar Slices Through Tropical Storm Sean

Sometimes you don't know what's in a pie until you slice it up, and the same goes for a tropical storm. NASA's Tropical Rainfall Measuring Mission (TRMM) satellite radar instrument sliced through Tropical Storm Sean and provided scientists with a 3-D look at what's happening inside.

The TRMM satellite had a good look at tropical storm Sean when it flew over on November 10, 2011 at 0541 UTC (12:41 a.m. EST). "TRMM's Precipitation Radar (PR) data were used to show a 3-D cross section through Sean.," said Hal Pierce of the TRMM science team from SSAI at NASA's Goddard Space Flight Center in Greenbelt, Md. "TRMM's PR revealed that heights of storms in the edge of Sean's center of circulation were reaching to about 11km (~6.8 miles). Radar Reflectivity values of 46.0 dBZ data found in these storms also showed that heavy rainfall was falling in that area."

TRMM data was also used to create a "top down" satellite view or rainfall, that showed those high storms in Sean's northwestern quadrant were the most powerful where rainfall was occurring at a rate of more than 2 inches (50 mm) per hour. The rest of Sean contained mostly scattered moderate to occasionally heavy rainfall.

A tropical storm warning is in effect for Bermuda, and rainfall is expected to total between 1 and 3 inches. Dangerous and life-threatening surf and rip-currents are possible along the Bermuda and southeastern U.S. coasts.

At 10 a.m. EST on Nov. 10, Tropical Storm Sean's maximum sustained winds were near 65 mph (100 kmh) and may strengthen to hurricane force over the next day. Sean was about 360 miles (580 km) west-southwest of Bermuda near latitude 30.4 north and longitude 70.5 west. Sean is moving toward the northeast near 7 mph (11 kmh) and is expected to continue in that direction for the next couple of days with an increase In forward speed. Sean is about 510 miles in diameter as tropical-storm-force winds extend outward up to 255 miles (410 km) from the center.

Sean is moving northeast and could become a hurricane within the next 24 hours. Thereafter, as Sean moves northeast into the north central Atlantic, wind shear is forecast to increase which will weaken Sean. Sean is expected to become extra-tropical over the weekend before being absorbed into a cold front.

Text credit: Rob Gutro/Hal Pierce
NASA's Goddard Space Flight Center/, Greenbelt, Md./SSAI



November 9, 2011

Tropical Storm Sean's rainfall was captured by the TRMM satellite on Nov. 9, 2011 at 2:37 a.m. EDT. › View larger image
This radar image of Tropical Storm Sean's rainfall was captured by the TRMM satellite on Nov. 9, 2011 at 2:37 a.m. EDT. The one small red area east of Sean's center indicates heavy rainfall of 2 inches (50 mm) per hour. Light to moderate rainfall (green and blue) around much of the storm was falling at a rate between .78 to 1.57 inches/20 to 40 mm per hour).
Credit: SSAI/NASA, Hal Pierce
This visible image of Tropical Storm Sean was captured by MODIS on Nov. 7th when Sean was off the Bahamas. › View larger image
This visible image of Tropical Storm Sean (the 19th tropical cyclone in the Atlantic) was captured by the MODIS instrument on NASA's Aqua satellite at 2 p.m. EDT on Nov. 7th, when Sean was off the Bahamas.
Credit: NASA Goddard MODIS Rapid Response Team
NASA Satellite Sees Moderate Rainfall in Tropical Storm Sean

Late season Tropical Storm Sean is generating moderate rainfall according to radar data on NASA's TRMM satellite.

The Tropical Rainfall Measuring Mission (TRMM) satellite passed over Sean this morning, Nov. 9 at 0637 UTC (2:37 a.m. EDT). The Precipitation Radar instrument data was used to create an image of the rainfall rates occurring in Sean at NASA's Goddard Space Flight Center in Greenbelt, Md. Most of the rain was falling at a rate between .78 to 1.57 inches (20 to 40 mm per hour). There was just one small area east of Sean's center where rain was falling at over 2 inches (50 mm) per hour.

TRMM Satellite data shows that the convection (rapidly rising air that forms the thunderstorms that power a tropical cyclone like Sean) is becoming more organized, and an eye may be forming. The TRMM image from early this morning gives the appearance of an eye.

A tropical storm warning is in effect for Bermuda as Sean approaches. Tropical storm conditions are expected on Bermuda by Thursday night, according to the National Hurricane Center. In addition, Sean is expected to produce 1 to 3 inches of rain in Bermuda and dangerous surf can be expected there and along the southeastern coast of the U.S. in the next couple of days.

At 10 a.m. EST on Nov. 9, Sean's maximum sustained winds were near 60 mph, and it may strengthen over the next day or two. Sean was located about 455 miles (735 km) southwest of Bermuda near latitude 27.9 north and longitude 70.5 west. Sean is moving toward the northwest near 3 mph (6 km/h) and is gradually expected to turn north and then northeast over the next day or two. The reason Sean is expected to turn to the northeast is because of an approaching elongated area of low pressure (a trough) moving toward the storm from the U.S. east coast.

Sean's center is expected to pass northwest of Bermuda on Friday morning.

Text credit: Rob Gutro
NASA's Goddard Space Flight Center/, Greenbelt, Md.






November 8, 2011

TRMM Sees Subtropical Storm Sean

The TRMM satellite flew directly above Sean a little earlier on 8 November 2011 at 0731 UTC ( 2:31 AM EST)
› View larger image
The National Hurricane Center (NHC) upgraded a low pressure center in the Atlantic Ocean to subtropical storm Sean at 0900 UTC ( 4:00 AM EST). The TRMM satellite flew directly above Sean a little earlier on 8 November 2011 at 0731 UTC ( 2:31 AM EST) collecting data used in the precipitation analyses shown.


TRMM PR data showstorms within Sean were reaching maximum heights of only about 11km (~6.8 miles).
› View larger image
TRMM Precipitation Radar (PR) data in the 3-D display above show that scattered moderate storms within Sean were reaching maximum heights of only about 11km (~6.8 miles). The "top down" view on the right above shows that Sean was well organized but most rainfall was of low to moderate intensity within scattered rain bands around Sean's center of circulation. Maximum reflectivity values of 48.2dBZ where found by TRMM PR within Sean indicating that some storms were dropping moderate to heavy rainfall. Sean is predicted to stay over the open waters of the Atlantic Ocean and move to the northwest of Bermuda on Friday 11 November 2011.

Text credit: Hal Pierce
SSAI/NASA's Goddard Space Flight Center/, Greenbelt, Md.