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Hurricane Season 2009: Gael (Indian Ocean)
02.11.09
 
Feb. 11, 2009

AIRS image of Gael from Feb. 11, 2009> Larger image
Credit: NASA/JPL Ed Olsen
Gael Has Gone "Extra-Tropical"

Going, Going, Gone…The Joint Typhoon Warning Center issued their final advisory on Tropical Cyclone Gael as it was becoming an extra-tropical storm more than 720 miles south-southeast of La Reunion island in the southern Indian Ocean.

NASA's Aqua satellite flew over Gael and the Atmospheric Infrared Sounder (AIRS) instrument onboard captured this visible image on Feb. 10 at 10:17 UTC (5:17 a.m. EST). In the visible satellite image, Gael is the swirl of clouds on the right center edge of the image. The large island nation of Madagascar is visible in the top left part of this satellite image.

The last advisory, issued Feb. 10 at 03:00 UTC or 7:00 a.m. in Indian/Reunion local time saw Gael at 32.6 degrees south latitude and 62.2 degrees east longitude. At that time, Gael was becoming extra-tropical and moving southeast near 20 knots (23 mph), still holding onto tropical storm-force winds of 55 knots, but weakening. Gael was also generating waves 20 feet high.

What Does "Conversion to an Extratropical Storm" Mean?

A conversion to "extratropical" status means that the area of low pressure (known as Gael in this case) eventually loses its warm core and becomes a cold-core system. During the time it is becoming extratropical the cyclone's primary energy source changes from the release of latent heat from condensation (from thunderstorms near the storm's center) to baroclinic (temperature and air pressure) processes. When a cyclone becomes extratropical it will usually connect with nearby fronts and or troughs (extended areas of low pressure) consistent with a baroclinic (pressure) system. When that happens it appears the system grows larger while the core weakens.

Text credit: Rob Gutro, NASA Goddard Space Flight Center


Feb. 09, 2009

Collage of satellite images of Gael's cloud temperatures show the storm's movements between La Reunion Island and Madagascar Credit: NASA JPL, Ed Olsen
> Larger image
Cyclone Gael Slings Between Madagascar and La Reunion, Now Headed South

Over the weekend of Feb. 7 and 8, the center of Cyclone Gael passed between La Reunion Island and Madagascar staying at sea. Now Gael is headed into the vast open waters of the southern Indian Ocean.

On Friday, Feb. 6, Gael was north of La Reunion Island, and made a southwest track in a "7 a.m. direction on a clock" passing to the island's west. It never made landfall in Madagascar, thankfully, and turned southeast, in a 5 o'clock direction. Its turning point was at sea, parallel to Antananarivo, Madagascar.

Residents of both areas were relieved that this powerful cyclone didn't make landfall. On Saturday, Feb. 7, Gael's strongest sustained winds reached 10 knots (11 mph).

On Monday, February 9, 2009 Gael entered an unfavorable environment, so weakening began. At 0300 Zulu Time (10 p.m. EST Feb 8), Gael's sustained winds were down to 90 knots (103 mph). Gael was located at 27.6 degrees south latitude and 55.4 degrees east longitude about 355 nautical miles south of La Reunion. Gael was moving south-southeastward near 16 knots (18 mph) in the wide open ocean where ocean temperatures are just below 26 degrees Celsius (78 degrees Fahrenheit). That's cool by tropical cyclone standards, as it takes surface waters of 80 degrees Fahrenheit or greater to help a storm maintain strength.

This collage of satellite images of Gael's cloud temperatures show the storm's movements over the weekend. They were created with data from the Atmospheric Infrared Sounder (AIRS) instrument onboard NASA's Aqua satellite. The image in the top right corner was created on February 7 at 3:47 a.m. EST. The large image is from February 8 at 5:29 a.m. EST, and the small image in the bottom left corner was created on Feb. 8 at 4:29 p.m. EST, as Gael had passed La Reunion Island and went into open waters.

The AIRS infrared images show the frigid cloud top temperatures, giving forecasters a clue to a storm's strength. The coldest temperatures (and highest cloud tops) appear in purple. Those purple areas are as cold as 220 degrees Kelvin or minus 63 degrees Fahrenheit (F) or colder, and there are two small such areas on this AIRS image. Lower, less cold clouds are depicted in blue, which are around 240 degrees Kelvin, or minus 27F.

Gael is forecast to transition to a strong extra-tropical system in the next 24 hours.

Text credit: Rob Gutro, NASA Goddard Space Flight Center


Feb. 06, 2009 - second update

NASA Eyes Tropical Cyclone Gael: As a Three-Dimensional Monster

3D image of Gael on Feb. 6, 2009> Larger image
Credit: NASA/SSAI, Hal Pierce
Cyclone Gael was a major hurricane on Feb. 6, and getting stronger. Gael had sustained winds near 100 knots (115 mph). That made Gael a Category Three hurricane on the Saffir-Simpson Scale, and it is expected to increase to a Category 4 status with sustained winds near 125 knots (143 mph) on its track past Madagascar this weekend.

This is a 3-D image from NASA's Tropical Rainfall Measuring Mission (TRMM) satellite of Cyclone Gael, with towering clouds, or "hot towers" over 15 kilometers (9 miles) high! Those high hot towers are an indication of a strong storm. This image was captured by the TRMM satellite as it passed above on February 6, 2009 at 0929 UTC (4:29 a.m. EST).

This second TRMM image shows the horizontal pattern of rain intensity within the storm. The yellow, green and red areas indicate rainfall between 20 and 40 millimeters (.78 to 1.57 inches) per hour. The red area is considered moderate rainfall. The very intense rainfall (over 50 mm/hour or ~2 inches/hr.) shown in the center of the storm was from TRMM's Precipitation Radar data.

TRMM image of Tropical Cyclone Gael on Feb. 6, 2009> Larger image
Credit: NASA/SSAI, Hal Pierce
For more information about how TRMM looks at rainfall, visit NASA's TRMM website at: > TRMM Web site. TRMM is a joint mission between NASA and the Japanese space agency JAXA.

Gael is expected to brush the length of the Madagascar coastline over the weekend.

Text credit: Rob Gutro and Jeff Schmaltz (MODIS)/Goddard Space Flight Center









Feb. 06, 2009

Forecasters Expect Madagascar to Get a Break from Powerful Gael

AIRS image of Gael from Feb. 6, 2009> Larger image
Credit: NASA/JPL
The latest forecasts from the Joint Typhoon Warning Center are a big sigh of relief for the African island nation of Madagascar. Gael is forecast to take a southern turn away from Madagascar and brush its east coast this weekend. Despite the turn away, Gael will still bring strong winds and dangerous high waves, but not as bad as it would as land-falling major hurricane.

On Friday, February 6 at 1500 Zulu Time (10 a.m. EST), Tropical Cyclone Gael had strengthened to a major cyclone with sustained winds near 100 knots (115 mph). That makes Gael a Category Three hurricane on the Saffir-Simpson Scale. A Cat three has sustained winds between 111-130 mph (96-113 knots or 178-209 km/hr). Forecasters expect that Gael could reach Category 4 status (sustained winds 131-155 mph) with sustained winds near 125 knots (143 mph) on its track south this weekend.

On Feb. 6 at 10 a.m. EST, Gael was located near 18.8 degrees south latitude and 52.3 degrees east longitude. That's about 235 nautical miles northwest of the island of La Reunion. Gael was moving westward near 6 knots (7 mph), but is expected to turn southwest, then south, brushing the length of the Madagascar coastline over the weekend. The storm is generating waves 23 feet high.

MODIS image of Gael from Feb. 6, 2009> Larger image
Credit: NASA MODIS Rapid Response Team, Jeff Schmaltz
Satellite imagery indicated that Gael is well-organized and has a defined eye 15 nautical miles across. Gael's eye is visible in this image taken on Feb. 6 at 1041 UTC (5:41 a.m. EST) from NASA's Atmospheric Infrared Sounder (AIRS) instrument aboard the Aqua satellite.

On February 5, Tropical Cyclone Gael grazed the small island of Mauritius, and had approached the central coast of Madagasca when this image was captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite. A wide gap had opened up in the storm west of the eye, but the inward, clockwise spiral of the cloud bands was still apparent. Thunderstorms are embedded in the cloud bands; their high tops seem to boil up from the surrounding clouds. The image was acquired at 2:10 p.m. local time on Reunion Island. The MODIS Rapid Response System at NASA's Goddard Space Flight Center, Greenbelt, Md. provided this image.

Text credit: Rob Gutro and Jeff Schmaltz (MODIS)/Goddard Space Flight Center


Feb. 05, 2009

Tropical Storm Gael's Gales to Brush by La Reunion and Mauritius

AIRS image of Gael from Feb. 5, 2009> Larger image
Credit: NASA/JPL
Tropical Storm Gael's gales are picking up in intensity, just as forecast. Gael is now a strong tropical storm with sustained winds near 55 knots (63 mph) and will soon become a hurricane on its way to Madagascar.

On Thursday, February 5, 2009 at 900 UTC (4:00 a.m. EST) Gael was located about 185 miles north-northeast of La Reunion Island. That's near 18.4 degrees south latitude and 57.0 degrees east longitude. Gael was moving west near 12 knots (13 mph).

The Joint Typhoon Warning Center noted "Gael is moving west, and is slowly gaining intensity amidst increasingly favorable atmospheric conditions. The storm will continue to intensify, reaching 95 knots (109 mph) on Friday. Gael will recurve southwest before reaching Madagascar proper. The islands of La Reunion and Mauritius do not appear to be directly in the cyclone's path, but will be close enough to feel its effects. Residents of these islands should monitor this situation closely."

AIRS image of Gael from Feb. 5, 2009> Larger image
Credit: NASA/JPL
NASA's Aqua satellite flew over Gael and the Atmospheric Infrared Sounder (AIRS) instrument onboard captured both an infrared and visible image of her cloud temperatures on Feb. 5 at 0959 UTC (4:59 a.m. EST). In the infrared and visible satellite images, Gael has the distinct "Comma shape" of a well-formed storm. The large island nation of Madagascar is directly to Gael's west.

The AIRS infrared images show the frigid cloud top temperatures, giving forecasters a clue to a storm's strength. The coldest temperatures (and highest cloud tops) appear in purple. Those purple areas are as cold as 220 degrees Kelvin or minus 63 degrees Fahrenheit (F) or colder, and there are two small such areas on this AIRS image. Lower, less cold clouds are depicted in blue, which are around 240 degrees Kelvin, or minus 27F.

Text credit: Rob Gutro, NASA Goddard Space Flight Center


Feb. 04, 2009

TRMM image of Gael in 3D heading toward Madagascar Credit: NASA/SSAI, Hal Pierce
> Larger image
NASA Captures Tropical Cyclone Gael in 3-D as it Heads to Madagascar

Tropical Storms are three dimensional things, and NASA's Tropical Rainfall Measuring Mission (TRMM) satellite team has been creating 3-D visualizations of tropical cyclone's rainfall for years. This 3-D perspective image of tropical storm Gael was made using TRMM's Precipitation Radar data. It shows thunderstorm or "hot" towers extending to over 17.5 kilometers (4.6 miles) high near Gael's center. These hot towers can be a sign of storm intensification.

Tropical cyclone Gael, also know as Tropical Cyclone 13s, was located approximately 370 nautical miles north-east of La Reunion island, or near 17.8 south and 61.9 east on Wed. Feb. 4 at 900 Zulu Time (4 a.m. EST). Gael had sustained winds near 40 knots (46 mph) with higher gusts and was moving westward near 9 knots (10 mph). This track is expected to hold for the next two days.

Forecasters note that decreasing vertical wind shear (winds that can tear a storm apart or weaken it) and passage across very warm water will fuel intensification especially after the next 12 hours, so Gael could become a hurricane in the next couple of days.

TRMM image of Gael on February 4, 2009 Credit: NASA/SSAI, Hal Pierce
> Larger image
This image shows tropical storm Gael in the Southern Indian Ocean using data captured by the TRMM satellite as it passed above on February 4, 2009 at 0944 UTC (4:44 a.m. EST). This TRMM image shows the horizontal pattern of rain intensity within the storm. The yellow, green and red areas indicate rainfall between 20 and 40 millimeters (.78 to 1.57 inches) per hour. The red area is considered moderate rainfall. The very intense rainfall (over 50 mm/hour or ~2 inches/hr.) shown in the center of the storm was from TRMM's Precipitation Radar data.

For more information about how TRMM looks at rainfall, visit NASA's TRMM website at: http://trmm.gsfc.nasa.gov/. TRMM is a joint mission between NASA and the Japanese space agency JAXA.

Tropical Cyclone Gael is predicted to head westward and may affect Madagascar after strengthening to a hurricane. Madagascar has a history of major disasters caused by deadly tropical cyclones. In 2007, six tropical cyclones hit Madagascar affecting about one-half million people.

Text credit: Rob Gutro, NASA Goddard Space Flight Center


Feb. 03, 2009

AIRS image of Tropical Cyclone Gael> Larger image
Credit: NASA/JPL
Gael Forms in the Southern Indian Ocean, Far From Land

Hurricane season in the southern Indian Ocean rolls on, with the formation of Gael, the 13th tropical cyclone in that ocean basin.

Gael is in the open waters of the Indian Ocean. On Tuesday, Feb. 3, Gael was about 135 nautical miles from Port Louis, Maritus. That puts Gael's center near 16.9 degrees south latitude and 64.8 degrees east longitude. Gael's sustained winds are near 30 knots (34 mph), and the storm is moving west-southwest near 11 knots (13 mph). By February 5, Gael is expected to track north of Maritus and Reunion Island.

Maritus is an island nation off the coast of the African continent in the southwest Indian Ocean, about 560 miles (900 kilometers) east of Madagascar. Reunion Island is approximately 50 miles from Maritus.

The infrared imagery of the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite is used to identify the cloud temperatures in tropical cyclones. It captured this image of Gael on Feb. 2 at 09:29 Zulu Time (4:29 a.m. EST).

Cloud temperatures are a good indicator of whether or not a storm is getting stronger. When cloud temperatures get colder, it means that clouds are getting higher. Building clouds indicate a lot of "uplift" in the atmosphere and stronger thunderstorms, which mean a strengthening or stronger tropical cyclone. The image shows that Gael has a good circular shape to it, indicating an organized storm.

The infrared image also shows a large temperature difference between the tops of the clouds in a tropical cyclone and the warm ocean waters that power it. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up Gael's high clouds. Those temperatures are as cold as or colder than 220 degrees Kelvin or minus 63 degrees Fahrenheit (F). The blue areas are around 240 degrees Kelvin, or minus 27F. This image also shows the warm ocean waters that surround the storm, colored in orange and red. The orange temperatures are 80F (300 degrees Kelvin) or greater, the temperature threshold needed to power tropical cyclones.

Text credit: Rob Gutro, NASA Goddard Space Flight Center