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Hurricane Season 2010: Tropical Storm Lisa (Atlantic Ocean)
09.27.10
 
September 27, 2010

The image shows much warmer cloud tops (blue) than in previous days, indicating that Lisa was weakening. › View larger image
This infrared image of Lisa' cloud temperatures was captured on Sept. 25 at 1523 UTC (11:23 a.m. EDT) by the AIRS instrument on NASA's Aqua satellite. The image shows much warmer cloud tops (blue) than in previous days, indicating that the strength of the convection has weakened and Lisa was weakening.
Credit: NASA/JPL, Ed Olsen
Tropical Depression Lisa Fades, NASA Watching 2 Other Atlantic Areas

Tropical Depression Lisa faded as NASA watched its cloud top temperatures warm on infrared imagery this weekend. Lisa is now a remnant drifting in the eastern Atlantic Ocean, while two other areas have caught the attention of scientists using NASA satellite data.

NASA's Atmospheric Infrared Sounder (AIRS) instrument flies aboard NASA's Aqua satellite and captures temperatures of cloud tops and sea surface temperatures: two important factors in tropical cyclones (Tropical cyclone is the generic name for tropical depression, tropical storm and hurricane).

When NASA's Aqua satellite flew over Lisa on Sept. 25 at 1523 UTC (11:23 a.m. EDT) the AIRS instrument showed much warmer cloud tops then than were seen in previous days, indicating that the cloud tops were not as high and cold as they were before. The stronger the thunderstorms and convection (rapidly rising air that forms thunderstorms that power a tropical cyclone) the stronger the storm. Therefore, warmer cloud tops indicate that the power in a tropical cyclone is weakening as the clouds don't have the push to bring cloud tops higher.

The last advisory on Lisa was issued by the National Hurricane Center on Sept. 25 at 5 p.m. EDT when Lisa's remnants were near 26.1 North and 29.4 west. At that time, Lisa's remnant low pressure area had maximum sustained winds near 30 mph, and weakening. Lisa was drifting north-northwest and continued in that direction over the weekend. Lisa has no chance for regeneration.

However, two other areas that forecasters are looking at using satellite imagery seem to have slightly better chances for development. One area is a low pressure system located about 725 miles west-southwest of the Cape Verde Islands is producing disorganized showers and thunderstorms. As that system moves slowly, forecasters at the National Hurricane Center (NHC) give it a 10 percent chance of development into a tropical depression in the next two days.

Meanwhile, far to the west, over the northwestern Caribbean Sea, there's an area of low pressure that has disorganized cloudiness and thunderstorms. The environment is favorable for development, so the NHC forecasters give it a 30 percent chance of development in the next 48 hours.

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



September 24, 2010

GOES-13 satellite captured a visible image of Tropical Storm Lisa › View larger image
The GOES-13 satellite captured a visible image of Tropical Storm Lisa (right) at 16 45 UTC (12:45 p.m. EDT) on Sept. 24. The GOES visible imagery showed that Lisa now has a well-organized center of circulation.
Credit: NOAA/NASA GOES Project
GOES-13 Satellite Sees Lisa a Tropical Storm… for Now

The GOES-13 satellite has been keeping an eye on Tropical Storm Lisa and watched her birth, graduation to depression then tropical storm and back to depression. Now, Lisa has grown back to tropical storm status, but it may be short-lived.

At 11 a.m. EDT on Friday, Sept. 24, Tropical Storm Lisa had maximum sustained winds near 50 mph and she may strengthen and weaken over the weekend, but by Sunday colder waters will zap her energy source and she is forecast to be a depression.

Meanwhile, on Sept. 24, she was still frolicking in the eastern Atlantic, about 320 miles northwest of the Cape Verde Islands, near 18.9 North latitude and 27.8 West longitude. Lisa was moving north at 7 mph and is expected to turn north-northwest on Sept. 25. Estimated minimum central pressure is 1000 millibars.

The GOES-13 satellite captured a visible image of Tropical Storm Lisa at 16 45 UTC (12:45 p.m. EDT) on Sept. 24. The GOES visible imagery showed that Lisa now has a well-organized center of circulation, which corresponds with infrared and microwave satellite imagery that showed convection has wrapped around three-fourths of the center of circulation.

The infrared data from the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite today showed that Lisa's thunderstorm cloud tops, north of the center of circulation had cooled down to a frosty -80 Celsius (-112 Fahrenheit), one factor that confirms her re-strengthening. The colder the cloud top temperatures, the higher the thunderstorms, and the more powerful they are. When cloud top temperatures cool, it indicates a strengthening storm. When they warm, a storm is weakening.

Over the weekend, Lisa will move into colder waters and the westerly wind shear will increase ahead of an elongated are of low pressure. The wind shear is forecast to be moderate to strong. So strong that they're expected to "decouple" or separate the low-level circulation from the upper-level circulation in the storm causing it to weaken significantly.

Lisa is expected to become a remnant low pressure system by early next week in the eastern Atlantic.

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



September 23, 2010

NASA Satellites Help See Ups and Downs Ahead for Depression Lisa

Tropical Depression Lisa when she was about 340 miles west-northwest of the Cape Verde Islands. › View larger image
The GOES-13 satellite captured an infrared image of Tropical Depression Lisa's (right) rounded clouds at 1445 UTC (10:45 a.m. EDT) on Sept. 23 when it was about 340 miles west-northwest of the Cape Verde Islands. Julia's remnants are in the top left of the image.
Credit: NOAA/NASA GOES Project
Tropical Depression Lisa has had a struggle, and it appears that she's in for more of the same.

Infrared satellite imagery from the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite shows that the convection (rapidly rising air that forms thunderstorms that make up a tropical cyclone) is increasing in Lisa. The convection is becoming a little better organized and stronger which is will make for some heavy rainfall over the northwestern Cape Verde Islands. It's also an indication that she may be strengthening back into a tropical storm today.

That increased convection is a sign that Lisa is strengthening a little, and that's what the National Hurricane Center is forecasting for the next 24 hours, although there is some dry air nearby in the mid-levels of the atmosphere that Lisa is contending with. Dry air saps the warm, moist "fuel" from tropical cyclones.

So, after 24 hours, Lisa is expected to run into another hurdle. In fact, several hurdles: dry air, cooler sea surface temperatures (AIRS can see those, too) and increasing wind shear from the west. Those are three factors that weaken tropical storms, so Lisa is under a "triple header" threat from her environment after Friday.

As of 11 a.m. EDT on Sept. 23, Tropical Depression Lisa's maximum sustained winds were near 35 mph. It was located about 340 miles west-northwest of the Cape Verde Islands near 17.5 North and 28.9 West. It was drifting at 2 mph to the north. Lisa's minimum central pressure was 1005 millibars.

The latest satellite imagery from the GOES-13 satellite (the Geostationary Operational Environmental Satellite) at 1445 UTC (10:45 a.m. EDT) on Sept. 23 shows Lisa off the western coast of Africa as a rounded circulation.

GOES-13 is operated by the National Oceanic and Atmospheric Administration, and images are created by NASA's GOES Project, located at NASA's Goddard Space Flight Center, in Greenbelt, Md. While Lisa is powering back up, the remnant circulation of former Tropical Depression Julia is located about 750 miles southwest of the Azores islands and there's only a ten percent chance that system will redevelop over the weekend.

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





September 22, 2010

GOES-13's Wide View of Atlantic's Tropical Storm Lisa and Low, Pacific's Georgette

Tropical Storm Lisa (right), a developing tropical low (center), and Tropical Storm Georgette (far left). › View larger image
In this image from 1445 UTC (10:45 a.m. EDT) on Sept. 22, GOES-13 captured Tropical Storm Lisa in the far eastern Atlantic (right), a developing tropical low near in the south-central Caribbean Sea (center), and Tropical Storm Georgette (far left) in the eastern Pacific Ocean, making landfall in Baja California
Credit: NOAA/NASA GOES Project
Georgette was a tropical depression with isolated moderate thunderstorms when the TRMM satellite passed over on Sept. 22. › View larger image
The Tropical Rainfall Measuring Mission (TRMM) satellite passed above Lisa on Sept. 21 at 2309 UTC (7:09 p.m. EDT) and revealed a few areas of moderate to heavy thunderstorms with rain falling at about 2 inches per hour(red) within the storm's circulation. The yellow and green areas indicate moderate rainfall between .78 to 1.57 inches per hour.
Credit: NASA/SSAI, Hal Pierce
The TRMM satellite passed above Lisa and revealed rain falling at about 2 inches per hour (red) within the storm's circulation. › View larger image
Georgette was a tropical depression with isolated moderate thunderstorms near the center when the Tropical Rainfall Measuring Mission (TRMM) satellite passed over on Sept. 22 at 0344 UTC. The yellow and green areas indicate moderate rainfall between .78 to 1.57 inches per hour.
Credit: NASA/SSAI, Hal Pierce
The GOES-13 satellite may be stationed in orbit over the eastern U.S., but it has a wide field of view from the eastern Atlantic to the eastern Pacific, and today it captured three tropical cyclones in one image.

At 1445 UTC (10:45 a.m. EDT) today, Sept. 22, the Geostationary Operational Environmental Satellite called GOES-13 captured Tropical Storm Lisa in the far eastern Atlantic, a developing tropical low in the south-central Caribbean Sea, and Tropical Storm Georgette in the eastern Pacific Ocean, making landfall in Baja California. The GOES series of satellites are managed by NOAA, and NASA's GOES Project at NASA's Goddard Space Flight Center in Greenbelt, Md. creates images and animations from the satellite data.

Tropical Storm Lisa is struggling today in the eastern Atlantic Ocean because of wind shear and dry air. Lisa was producing a small area of deep convection near the surface of her center of her circulation. The center of circulation is also exposed to outside winds, which make the storm prime for weakening. In addition, there is a lot of dry air around Lisa at the middle levels of the troposphere (likely from the Saharan dust that has been blowing off the African coast). All of those things are indicators why Lisa has not been able to intensify.

The Tropical Rainfall Measuring Mission (TRMM) satellite passed above Lisa on Sept. 21 at 2309 UTC (7:09 p.m. EDT) and revealed a few areas of moderate to heavy thunderstorms with rain falling at about 2 inches per hour within the storm's circulation.

At 11 a.m. EDT on Sept. 22, Lisa had maximum sustained winds near 45 mph. The National Hurricane Center noted that some strengthening is possible over the next 48 hours, so the environmental conditions should become more conducive for the tropical cyclone. Lisa was 435 miles west of the Cape Verde Islands, near 17.1 North and 30.5 West. It was moving very little in a southeasterly direction at 3 mph and is forecast to move little in the next couple of days. Estimated minimum central pressure is 1002 millibars.

Meanwhile, there is a low pressure area in the south-central Caribbean Sea that forecasters are watching. Today's GOES-13 satellite image does show some circulation in the clouds associated with the low. NOAA's National Hurricane Center (NHC) noted that this low has the potential to become the 15th tropical depression of the Atlantic Ocean hurricane season over the next day or two. In fact, NHC gives the low a 60 percent chance of making the grade to tropical depression in 48 hours. That low is expected to bring showers and squalls over the Netherlands Antilles and the northern coasts of western Venezuela and Colombia today.

Further west, Tropical Depression Georgette has already crossed over Baja California and is now headed to another landfall on the mainland in Mexico. A tropical storm watch is in effect for the coast of mainland Mexico from Huatabampito Northward to Bahia Kino.

When the Tropical Rainfall Measuring Mission (TRMM) satellite passed over Georgette on Sept. 22 at 0344 UTC ( Sept. 21 11:44 p.m. EDT) the tropical depression had isolated moderate thunderstorms near the center with rainfall between .78 to 1.57 inches per hour.

Georgette is a tropical depression with maximum sustained winds near 35 mph. It is located in the Sea of Cortes (the Gulf of California) and is about 85 miles south of Guaymas, Mexico. It is centered near 26.8 North and 111.0 West, with a minimum central pressure of 1000 millibars.

The depression is moving toward the north-northwest near 14 mph and is expected to turn north later today making landfall tonight. The NHC noted that "Georgette is expected to produce total rainfall accumulations of 4 to 6 inches over the western portions of the state of Sonora with isolated maximum amounts of 10 inches possible."

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





September 21, 2010

NASA Infrared Imagery Sees Tropical Depression 14 Becomes 12th Tropical Storm: Lisa

Image of Tropical Storm Lisa from the AIRS instrument aboard NASA's Aqua satellite. › View larger image
This infrared image of Tropical Storm Lisa from the AIRS instrument aboard NASA's Aqua satellite shows that the strongest convection, highest thunderstorms and heaviest rainfall on Sept. 20 at 15:05 UTC (11:05 a.m. EDT) were concentrated in the system's center (purple) and there were bands of thunderstorms surrounding the center. Those cloud top temperatures were as cold as -94 Fahrenheit, indicating strong thunderstorms.
Credit: NASA/JPL, Ed Olsen
This Atlantic hurricane season has now spawned 14 tropical depressions and 12 of them have strengthened into tropical storms. The latest is now called Tropical Storm Lisa and is in the Eastern Atlantic Ocean. NASA's Aqua satellite flew over Lisa when she was still a low pressure area, but showed a center of circulation and banding of thunderstorms circling it, indicating the storm was getting organized.

The Atmospheric Infrared Sounder (AIRS) instrument that flies aboard NASA's Aqua satellite captured "Lisa" when she was still a low pressure area yesterday, Sept. 20 at 15:05 UTC (11:05 a.m. EDT). AT that time, infrared imagery showed the strongest convection, highest thunderstorms and heaviest rainfall were concentrated in the system's center and there were bands of thunderstorms surrounding the center. Those cloud top temperatures were as cold as -94 Fahrenheit (-70 Celsius), indicating strong thunderstorms. AIRS data indicated that overnight, those cloud top temperatures cooled. That indicates that the thunderstorms that are powering Lisa are higher, colder and stronger than they were yesterday. Infrared imagery helped forecasters see that Tropical Depression 14 became better organized and that it had become a tropical storm. Satellite imagery also showed that bursts of deep convection are forming near Lisa's circulation center.

At 5 a.m. EDT on Sept. 21, Tropical Depression 14 strengthened into Tropical Storm Lisa with maximum sustained winds near 40 mph. Lisa is in the Eastern Atlantic Ocean, about 530 miles west-northwest of the Cape Verde Islands near 17.7 North and 31.8 West. Lisa is moving north near 5 mph and is expected to turn to the north-northwest tomorrow, and then west-northwest on Thursday. The National Hurricane Center in Miami, Fla. noted that some strengthening is possible. Lisa's minimum central pressure is 1005 millibars.

Because Lisa is in an environment with low wind shear, it will allow her to strengthen further. Lisa will remain far at sea for now.

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