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Hurricane Season 2011: Tropical Storm Errol (Southern Indian Ocean)
04.19.11
 
Visible image from AIRS showing Errol no longer has a circular shape indicating that wind shear has taken its toll on the storm. › View larger image
This visible image from the AIRS instrument aboard NASA's Aqua satellite was captured on April 18. Errol no longer has a circular shape to its clouds indicating that wind shear has taken its toll on the storm. Western Australia is seen at the bottom of the image.
Credit: NASA/JPL, Ed Olsen
Infrared image from AIRS instrument shows areas of strong thunderstorms still exist in Errol's remnants. › View larger image
This infrared image from NASA's Aqua satellite AIRS instrument shows some areas of strong convection (strong thunderstorms) still exist in Errol's remnants. Those areas have high cloud tops with temperatures as cold as or colder than -63 F/-52C and appear in purple.
Credit: NASA/JPL, Ed Olsen
NASA Sees Remnants of A Once-Swashbuckling Cyclone Errol in So. Indian Ocean

Unlike the famous Hollywood actor of days gone by the remnants of cyclone Errol are no longer making a lot of noise in the Southern Indian Ocean. In fact, NASA satellite data reveals that wind shear has taken its toll on the center of the storm's circulation, despite some improved convection.

Errol Flynn was an actor in the 1930s and 40s known for his swashbuckling film roles in movies like Captain Blood and Robin Hood. Cyclone Errol was known for its rains and wind in northern Western Australia and then in Indonesia's West Timor.

When NASA's Aqua satellite passed over Cyclone Errol's remnants on April 18 at 05:35 UTC (1:35 a.m. EDT), the Atmospheric Infrared Sounder (AIRS) instrument captured both an infrared and visible image of the storm. The visible image from AIRS showed that Errol no longer has a circular shape to its clouds indicating that wind shear had taken its toll on the storm. In the infrared image, however, Errol still showed some deep convection occurring over West Timor and over open waters of the Southern Indian Ocean. The problem remains that Errol still has a disorganized low-level center of circulation, so the convection (rapidly rising air that forms thunderstorms) also remains disorganized.

On April 19, Errol's center of circulation was about 110 nautical miles west of Kupang, West Timor near 10.2 South latitude and 122.1 East longitude. Although the wind shear against Errol has relaxed, the Joint Typhoon Warning Center currently gives Errol a poor chance for redevelopment in the next 24 hour.

Despite the poor prognosis for more swashbuckling in the next 24 hours, NASA's AIRS instrument will continue to provide data and peer into Errol's clouds to see if the storm re-organizes and makes more noise in the Southern Indian Ocean.

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







April 18, 2011

On April 18 at 04:53 UTC, AIRS showed very little strong (purple) convection remained in Errol. › View larger image
AIRS instrument aboard NASA's Aqua satellite captured an infrared image on April 18 at 04:53 UTC (12:53 a.m. EDT) that showed very little strong (purple) convection remained in Errol and most cloud tops were warming (blue).
Credit: NASA/JPL, Ed Olsen
NASA's Aqua Satellite Sees Weaker Tropical Depression Errol Crossing West Timor

NASA's Aqua satellite captured an infrared image of Tropical Depression Errol's warming cloud temperatures as it was crossing the southern tip of West Timor today.

West Timor is the western and Indonesian portion of the island of Timor. To the east lies the Timor Sea, to the west is the Southern Indian Ocean.

The Atmospheric Infrared Sounder (AIRS) instrument aboard NASA's Aqua satellite captured an infrared image on April 18 at 04:53 UTC (12:53 a.m. EDT) that showed very little strong convection (rapidly rising air that forms thunderstorms) remained in Errol. The strongest areas of convection had cloud-top temperatures as cold as -63F/-52C. However, AIRS data shows that much of the cloud top temperatures in the depression have since warmed.

Cloud-top temperatures are important because they tell forecasters how high thunderstorms are, and the higher the thunderstorm, the colder the cloud tops and the more powerful the thunderstorms. Warming cloud top temperatures mean lower cloud heights and indicate that the storm is growing weaker. It means that there's not as much power to lift the air up to create the thunderstorms that power it.

As usually happens when a tropical cyclone crosses land, it weakens because it is cut-off from the warm ocean waters that power it. In addition, vertical wind shear has increased to 15 knots (17 mph/28 kmh) providing additional weakening.

Tropical Depression Errol had maximum sustained winds near 30 knots (34 mph/55 kmh) on Monday, April 18 at 1200 UTC (8 a.m. EDT). It was located about 35 nautical miles west-northwest of Kupang, West Timor near 10.0 South and 122.9 East. It was moving northwestward at 1 knot (1 mph/2 kmh). By 12 p.m. EDT on April 18, Kupang, West Timor, Indonesia was reporting cloudy skies and rising pressure, indicating that Tropical Depression Errol was moving away.

Errol is encountering wind shear and is expected to continue weakening as it moves west to west-southwest. The Joint Typhoon Warning Center forecasters note that in addition to being weakened from tracking over land, and encountering increased wind shear, drier air is moving in, which will sap the moisture and ability to generate thunderstorms within. Errol is forecast to dissipate in the open waters of the Southern Indian Ocean in a day or two.

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



April 15, 2011

The purple areas in Errol represent cloud-top temperatures as cold as or colder than -63 F/-52C. › View larger image
This infrared image from NASA's AIRS instrument shows that Tropical Storm Errol's strongest thunderstorms with the coldest, highest cloud tops (purple) are off-shore from the northern coast of Western Australia on April 14 at 0517 UTC. The purple areas represent cloud-top temperatures as cold as or colder than -63 F/-52C.
Credit: NASA/JPL, Ed Olsen
TRMM revealed heavy rainfall (red) in strong thunderstorms where rain was falling at 2 inches/5 mm hour. › View larger image
The Tropical Rainfall Measuring Mission (TRMM) satellite flew over Errol as it organized on April 14 at 1732 UTC. TRMM revealed heavy rainfall (red) in strong thunderstorms where rain was falling at 2 inches/5 mm hour. Image created from TRMM's TMI and PR instruments.
Credit: NASA/SSAI, Hal Pierce
This 3-D image from NASA's TRMM satellite showed Errol's strong thunderstorms (red) and heavy rainfall on April 14. › View larger image
This 3-D image from NASA's TRMM satellite showed Errol's strong thunderstorms (red) and heavy rainfall on April 14. Some of the strongest thunderstorm cloud tops were 9 miles high (15 km).
Credit: NASA/SSAI, Hal Pierce
NASA Sees Australian Newborn Tropical Storm Errol's Strongest T-storms Off-Shore

The low pressure area formerly known as System 92S has strengthened overnight and developed into Tropical Storm Errol today, April 15. Infrared imagery from NASA's Aqua satellite showed strong thunderstorms near Errol's center, but they remained off-shore from Western Australia's northern coast.

An infrared image on April 14 at 0517 UTC (2:47 p.m. Australia/Darwin local time) from NASA's Atmospheric Infrared Sounder (AIRS) instrument (that flies aboard NASA's Aqua satellite) shows that Tropical Storm Errol's strongest thunderstorms with the coldest, highest cloud tops were off-shore from the northern coast of Western Australia. Those thunderstorms had cloud-top temperatures as cold as or colder than -63 F/-52C and brought heavy rainfall.

Multispectral satellite imagery also showed a well-defined center of circulation in Errol, and bands of thunderstorms wrapping around its souther and western edges.

Tropical Storm Errol has sustained winds of 40 knots (46 mph/74 kmh) with higher gusts, and is kicking up rough surf along the northern coast of Western Australia today. Errol's center was about 270 miles (434 km) west of Darwin, Australia near 13.1 South latitude and 126.3 East longitude. Errol is currently drifting south-southwestward at 2 knots (2 mph/~4 km) but is expected to start moving to the west-northwest as a result of a strengthening ridge of high pressure building up over Western Australia.

Forecasters at the Joint Typhoon Warning Center (JTWC) take the storm westward and out to the open waters of the Southern Indian Ocean over the next couple of days, which is good news for residents of Western Australia. However, dangerous surf will continue with gusty winds and heavy downpours over the weekend as Errol moves away. Currently the JTWC notes that Errol is kicking up 12-foot (~3.5 meter) high seas.

The Australian Bureau of Meteorology (ABoM) noted that Errol may intensify on April 16 as it continues to move away from the Kimberley coast of Western Australia. ABoM has posted a Blue Alert for residents who live in areas between Kalumburu and Kuri Bay, including coastal and island communities. The ABoM forecast notes that wind gusts as high as 68 mph (110 kmh), just a little below hurricane-strength, may be experienced along coastal areas from Kalumburu and Kuri Bay later tonight (April 15) or Saturday (April 16) morning depending on the Tropical Storm's movement. Errol is also expected to bring heavy rainfall, so residents should be on guard for local flooding especially in the northern areas of the Kimberley.

Errol is forecast to track west into the Indian Ocean and remain south of the main Indonesian islands.

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












April 14, 2011

System 92S was captured by the MODIS instrument that flies aboard NASA's Aqua satellite on April 13. › View larger image
This visible image of System 92S was captured by the MODIS instrument that flies aboard NASA's Aqua satellite on 0519 UTC (1:19 a.m. EDT) on April 13. The area near the center that appears to have texture is filled with higher, more powerful thunderstorms.
Credit: NASA/NRL
NASA Satellite Sees Powerful Thunderstorms in Australian Developing Tropical Low 92S

Visible imagery from NASA's Aqua satellite showed strong convection around the center of developing tropical low 92S that lies north of the Western Australia coastline.

System 92S is still in the Timor Sea today. Early this morning (EDT), April 14, it was about 315 miles (506 km) west of Darwin, Australia. The southern extent of the low pressure area's clouds, however, already stretch over land in Western Australia. The center of System 92S' circulation at 06:30 UTC (2:30 a.m. EDT) was near 13.0 South latitude and 125.5 East longitude. The system appears to be consolidating and there is strong convection near the center of circulation.

By 8 p.m. WST Australia local time (6:30 a.m. EDT) System 92S' center was near 12.5S and 126.3E. That is 127 miles (205 km) north of Kalumburu. Although it moved from this morning, System 92S is now nearly stationary.

The Australian Bureau of Meteorology has issued a Strong Wind Warning from Kuri Bay to Wyndham for the next 24 to 36 hours. That warning area can expect east-southeasterly wind between 20 (23-34 mph) and 30 knots (37-55 kmh) with higher gusts and squalls. Seas are expected to be 6 to 10 feet (2 to 3 meters).

The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument that flies aboard NASA's Aqua satellite captured a visible image of System 92S on 0519 UTC (1:19 a.m. EDT) on April 13. In the imagery there was area near the center that appears to have texture and shadows. That area is one of higher, more powerful thunderstorms, and is still over open waters of the Timor Sea.

Weather radar from Wyndham (in the Kimberely region of Western Australia) today showed weak convective banding of thunderstorms along the coast northern coast of Western Australia. Microwave imagery also showed the banding of thunderstorms along the southern edge of the storm.

Currently maximum sustained winds are estimated near 20 (23 mph/37 kmh) to 25 knots (29 mph/46 kmh) and the minimum central pressure is 1005 millibars. The Joint Typhoon Warning Center gives this tropical low a fair chance for developing into a tropical storm over the next 24 hours. According to the Australian Bureau of Meteorology, the low is not expected to affect the Western Australian coast in the next 48 hours.

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



April 12, 2011

System 93P is approximately 800 nautical miles wide. › View larger image
A large System 93P in the southwestern Pacific Ocean stretches from 152 to168 East latitude (16 degrees) and is approximately 1040 nautical miles (in longitude)wide. Strongest convection appears far from the center of circulation (purple) wrapping from the northwest to southeast.
Credit: NASA/JPL, Ed Olsen
System 92S is approximately 400 nautical miles wide. › View larger image
System 92S is about half the size of System 93P. System 92S stretches from 123 to 131 East latitude (8 degrees) in the Southern Indian Ocean, which is approximately 520 nautical miles (in longitude) wide. The purple area indicates the strongest convection in the storm, and the highest, coldest, thunderstorm cloud tops.
Credit: NASA/JPL, Ed Olsen
NASA's Aqua Satellite Tracking 2 Southern Hemisphere Systems for Tropical Development

Two tropical low pressure systems caught the infrared eye of NASA's Aqua satellite today and they're being watched for possible development into tropical cyclones. The low in the southwestern Pacific Ocean appears to be twice as wide as the system in the Southern Indian Ocean.

NASA's Aqua satellite circles the globe twice a day and captures a variety of images from several satellites that fly aboard. The Atmospheric Infrared Sounder (AIRS) instrument captured images of the tropical lows on April 13, 2011. System 92S is located in the Southern Indian Ocean about 340 miles west of Darwin, Australia. System 93P is in the Southwestern Pacific Ocean about 580 miles northwest of Noumea, New Caledonia.

System 93P in the southwestern Pacific Ocean stretches from 152 to168 East latitude (16 degrees) approximately 1040800 nautical miles (in longitude) wide. Its center was approximately near 15.2 South latitude and 159.5 East longitude. The width of the AIRS infrared data swath (the width of the false-colored imagery) extends about 1056 miles (1700 kilometers), and System 93P filled up about more than four-fifths of that swath, indicating that the low is very large.

The Joint Typhoon Warning Center (JTWC), the organization that forecasts tropical cyclones in both the Southern Indian Ocean and Southern Pacific Oceans noted that visible imagery of System 93P showed consolidation of convection within the storm. There is also curved banding of thunderstorms around the low-level center. Sea surface temperatures are warm enough to support a tropical cyclone (at least 80F/27C), however, the potential for development of System 93P remains poor over the next 24 hours.

System 92S is about half the size of System 93P. System 92S stretches from 123 to 131 East latitude (8 degrees) in the Southern Indian Ocean, which is approximately 400 520 nautical miles (in longitude) wide. The center of System 92S is near 12.0 South latitude and 125.0 East longitude.

This low appears to be more consolidated and organized than System 93P. System 92S has a larger more concentrated area of strong convection than System 93P, and that convection is located around the northern and western edges of the storm. Because System 93P is in an area of moderate vertical wind shear, the JTWC also gives this low a poor prognosis for development in the next 24 hours, but that could change.

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