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Hurricane Season 2011: System 91L (Atlantic Ocean)
04.25.11
 
Aqua passed over the Atlantic low on April and captured this visible image of the comma shaped system. › View larger image
NASA's Aqua satellite passed over the Atlantic low on April 21 at 17:05 UTC (1:05 p.m. EDT) and captured this visible image of the comma shaped system. The majority of the clouds appear north of the center of circulation.
Credit: NASA/JPL, Ed Olsen
Fizzled Tropical Prospects: The Atlantic Low

That low pressure system known as System 91L that caught a lot of attention in the North Atlantic last week is now history. System 91L sparked the interest of forecasters because it had a small chance to develop into a subtropical or tropical storm last week. Now that chance is zero.

On Saturday, April 23, 2011, the showers associated with System 91L diminished. At that time, the low was centered about 360 miles north of San Juan, Puerto Rico. Wind shear had taken its toll on the low and weakened it . As a result, the National Hurricane Center issued their final notice about the system on Saturday.

Currently there are no tropical cyclones expected elsewhere in the Atlantic Ocean, and the official hurricane season doesn't start until June 1.

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



April 22, 2011

Aqua passed over the Atlantic low on April and captured this visible image of the comma shaped system. › View larger image
NASA's Aqua satellite passed over the Atlantic low on April 21 at 17:05 UTC (1:05 p.m. EDT) and captured this visible image of the comma shaped system. The majority of the clouds appear north of the center of circulation.
Credit: NASA/JPL, Ed Olsen
In this infrared image, the small purple areas indicate very high cloud tops and strong thunderstorms (and strong convection). › View larger image
NASA's Aqua satellite passed over the Atlantic low on April 21 at 17:05 UTC (1:05 p.m. EDT) and captured this infrared image. The small purple areas indicate very high cloud tops and strong thunderstorms (and strong convection).
Credit: NASA/JPL, Ed Olsen
NASA Catches Infrared Image of Struggling Atlantic Low in the Tropics

Infrared imagery from NASA's Aqua satellite today is still showing some signs of deep convection in the Atlantic Ocean low pressure area. Despite the convection the system has a slim chance of tropical development.

The low pressure area in the Atlantic Ocean than has been the cause of attention of forecasters at the National Hurricane Center and various satellites still has a low chance of development today. The low is classified as a non-tropical low although it has a small chance of developing into a sub-tropical or tropical storm.

NASA's Aqua satellite passed over the Atlantic low on April 21 at 17:05 UTC (1:05 p.m. EDT) and captured an infrared and visible image of the system. There were isolated areas of very high cloud tops and strong thunderstorms (and strong convection) that appeared more organized than on April 20. Coldest cloud top temperatures in some of the storms were as cold as -63F/-52C indicating strong thunderstorms. The colder the cloud top, the higher and stronger the storm.

By 8:30 a.m. EDT this morning, April 22, the center of the low was about 385 miles south-southeast of Bermuda. The National Hurricane Center noted in a statement today that the system does appear a little better organized. However, winds near the system appear to have decreased below gale force. The low is moving at 10 mph toward the north, and is expected to slow later today. It is still generating 8 to 10 foot high swells.

The National Hurricane Center noted that there is a 20 percent chance, up from yesterday's 10 percent chance, that the low may develop into a subtropical or tropical cyclone within the next 12 to 24 hours, After that time, it may interact with a front moving off the U.S. East coast and run into wind shear, which would weaken it.

Hurricane season begins June 1 and lasts through Nov. 30 and whenever the first tropical storm is named it would be known as Arlene this year.

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



April 21, 2011

TRMM noticed light to moderate rainfall occurring in the storm on April 21. › View larger image
NASA's TRMM satellite flew over the western side of the North Atlantic Low pressure area on April 21 at 1326 UTC (9:26 a.m. EDT) and noticed light to moderate rainfall occurring in the storm. The blue areas indicate rainfall between 10 and 15 mm (.4 and .6 inches) per hour.
Credit: NASA/SSAI, Hal Pierce
NASA's TRMM Satellite Sees Light to Moderate Rains in North Atlantic Low

Rainfall data from NASA's TRMM satellite is hinting that the low pressure area sitting 450 miles north-northeast of San Juan, Puerto Rico appears less likely to develop into a tropical or subtropical storm in the next couple of days.

NASA's Tropical Rainfall Measuring Mission (TRMM) satellite flew over the western side of the North Atlantic Low pressure area on April 21 at 1326 UTC (9:26 a.m. EDT) and noticed light to moderate rainfall occurring in the storm. Most of the rainfall was falling at a rate of 10 and 15 mm (.4 and .6 inches) per hour. Those showers also appeared very poorly organized in satellite imagery today. TRMM is managed by both NASA and the Japanese Space Agency, JAXA.

At 1:45 p.m. EDT on April 21, the National Hurricane Center (NHC) issued a special tropical weather outlook on the low pressure area noting that the chance for development has decreased from 20 percent yesterday to 10 percent today.

Forecasters at NHC noted that upper level winds are expected to become less conducive for development of the low on Friday.

The low has an estimated minimum central pressure of 1009 millibars and has gale force winds that are generating 10-15 foot high seas. The low continues to move northwestward at 10 mph in the Atlantic and is expected to move in a more northerly direction and weaken.

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



April 20, 2011

satellite image of TL No. 1 › View larger image
This visible image of the early tropical low several hundred miles north-northeast of Puerto Rico was captured on April 20 at 17:45 UTC (1:45 p.m. EDT) from the GOES-13 satellite.
Credit: NOAA/NASA GOES Project
GOES-13 Sees an Extraordinarily Early Atlantic Low in the Tropics

Hurricane season doesn't start in the Northern Atlantic Ocean until June 1, but a low pressure system in doesn't seem to want to follow the calendar. There's a low pressure area with a small chance for development north-northeast of Puerto Rico, and the GOES-13 satellite captured a visible image of the storm.

The National Hurricane Center (NHC) issued a Special Tropical Weather Outlook today, April 20, that noted the low pressure area was located about 460 miles northeast of San Juan, Puerto Rico at 3:35 p.m. EDT. The NHC noted that slow development is possible over next couple of days. The low is moving west -northwest at 10mph.

The image was created using satellite imagery was captured on April 20 at 17:45 UTC (1:45 p.m. EDT) from the Geostationary Operational Environmental Satellite (GOES-13). Although it is not easy to pick out the center of circulation in the image, it is located to the west of the largest area of clouds.

GOES satellites are operated by the National Oceanic and Atmospheric Administration. The image was created by NASA's GOES Project, located at NASA's Goddard Space Flight Center, Greenbelt, Md.

The NHC gives this low a 20 percent chance of development into a sub-tropical or tropical storm over the next two days before it hits wind shear, which will weaken it.

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