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Hurricane Season 2008: Billy (Indian Ocean)
12.19.08
 
Dec. 30, 2008

Cyclone Billy Now a Memory Off the Northwestern Australian Coast

Cyclone Billy off the coast of Australia Credit: Jeff Schmaltz, MODIS Rapid Response Team
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Tropical Cyclone Billy moved off the coast of Western Australia on December 25, 2008. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite took this picture at 3:10 p.m. local time on December 25. Compared to earlier images, the storm appears more compact in this picture, and occurs almost entirely over the ocean.

After canceling a tropical cyclone warning from Pardoo to Port Headland, the Australian Government Bureau of Meteorology issued a cyclone warning for Western Australia coastal communities near Pilbara, on December 25, 2008. The bulletin warned of wind gusts up to 100 kilometers (60 miles) per hour, should the storm take a route more toward the southwest. The bulletin also forecast a high probability of a tropical cyclone in the region from December 26-28, 2008.

On December 28, 2008, the Australian Government Bureau of Meteorology downgraded the storm’s status to that of ex-tropical cyclone, stating that it posed no further threat to communities of Western Australia.

Text Credit: Michon Scott, Goddard Space Flight Center



Dec. 29, 2008

Silent Night in the Tropics: Billy Doesn't Make the New Year

AIRS image of Billy from December 27, 2008> Larger image
Credit: NASA JPL/ Ed Olsen
Cyclone Billy didn't make it into 2009. Just before Christmas, Billy had come off the northwestern coast of Australia and into the open waters of the Indian Ocean. Since that time, Billy first picked up steam near the warm waters of the Australian coast, but later faded when he encountered the cooler waters and stronger wind shear in the open waters.

On Saturday, Dec. 27, the Joint Typhoon Warning Center issued one of their final forecasts for Billy. On that day at 9:00 Zulu Time (4:00 a.m. EST), Billy had maximum sustained winds 50 knots (57 mph) and was still a tropical storm. However, his strength faded soon after and Billy was a low pressure area by Dec. 29th. On the 27, Billy was 425 miles north of Learmonth, Australia, so he was a good distance away from the warm waters of the coast. His position was 15.2 degrees south and 113.0 degrees east, and Billy was crawling along at 3 knots (4 mph) to the west. Two days later, Billy would be gone.

NASA's Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite captured Billy's cloud temperatures. AIRS produced this infrared image on Dec. 27 at 12:53 a.m. EST (5:53 UTC). Billy is depicted in this AIRS image as the round area of clouds northwest of Australia.

The infrared image shows the frigid cloud top temperatures, giving forecasters a clue to the storm's strength. The coldest temperatures (and highest cloud tops) shown in purple are as cold as 220 degrees Kelvin or minus 63 degrees Fahrenheit (F) or colder. The lower clouds are depicted as the blue areas, which are around 240 degrees Kelvin, or minus 27F.

Now that Billy has faded, there are currently no other tropical cyclones happening around the world on Monday, December 29, so it will finally be a "Silent Night" in the tropics.

Text Credit: Rob Gutro/NASA's Goddard Space Flight Center



Dec. 24, 2008

All Australia's Billy Wants for Christmas Weekend is Warm Water

AIRS image of Billy on Dec. 24, 2008> Larger image
Credit: NASA/JPL
Warm water, over 80 degrees Fahrenheit (26.5 Celsius), is what's needed to power and strengthen tropical cyclones, and that's all that Tropical Cyclone Billy wants for the Christmas weekend. His Christmas wish has been granted as he moved into the warm waters off of northwestern Australia.

That warm water has given Billy's winds a kick and on Dec. 24 at 3:00 Zulu Time (Dec. 23 at 10 p.m. EST) his maximum sustained winds were up to 75 knots (86 mph) with gusts to 90 knots (103 mph). Billy is a category one cyclone on the Saffir-Simpson scale.

At that time, Billy had developed a six-mile (in diameter) "pinwheel eye" over open waters in the Indian Ocean and was moving west near 5 knots (6 mph). He was bringing rains to the coastal towns of Port Hedlund, and Karratha. His outer bands extended inland and were raining on the towns of Pannawonica, Tom Price and Newman, Australia around 8 a.m. EST on Dec. 24. Billy was centered about 345 nautical miles northeast of Learmonth, Australia at that time. For local radar: A click on this link.

NASA's Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite captured Billy's cloud temperatures off the Australian northwest coast. AIRS produced this infrared image on Dec. 23 at 12:11 p.m. EST (17:11 UTC).

The infrared image shows the frigid cloud top temperatures, giving forecasters a clue to the storm's strength. The coldest temperatures (and highest cloud tops) shown in purple are as cold as 220 degrees Kelvin or minus 63 degrees Fahrenheit (F) or colder. The lower clouds are depicted as the blue areas, which are around 240 degrees Kelvin, or minus 27F.

Although Billy got his Christmas wish for warmer sea surface temperatures, and will likely be the only storm on the globe on Christmas Day, the winds and cooler waters he encounters in the days after will weaken him at sea. At least Billy poses no direct threat to the residents of northwestern Australia over the holiday weekend.

Text Credit: Rob Gutro/NASA's Goddard Space Flight Center



Dec. 23, 2008

Billy Strengthens Back Into a Cyclone

Typhoon Billy over Australia Credit: Jeff Schmaltz, MODIS Rapid Response Team
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Tropical Cyclone Billy continued traveling along Western Australia’s Kimberley Coast on December 22 and 23, 2008. At 3:55 a.m. local time on December 23, the Australian Government Bureau of Meteorology issued a cyclone warning for coastal and island communities from Kuri Bay to Wallal, and a cyclone watch for coastal areas from Wallal to Roebourne. At the time of the report, Billy was classified as a category 1 storm, and was estimated to be 26 kilometers (16 miles) south southwest of Cape Leveque and 165 kilometers (103 miles) north northeast of Broome. The storm was expected to travel west southwest at 13 kilometers (8 miles) per hour. Coastal communities could anticipate heavy rain, localized flooding, and strong winds.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite took this picture of Tropical Cyclone Billy at 2:40 p.m. local time on December 22, 2008. In this image, the storm stretches across several hundred kilometers of coastline, with intense clouds to the northwest, and clouds stretching inland, far to the southeast. The high-resolution image shows clouds reaching as far as Australia’s Northern Territory.

On December 23, 2008, the Australian Government Bureau of Meteorology issued a forecast track map predicting that Billy would travel west southwest over the next few days, moving off the Australian coast.

Text Credit:Jeff Schmaltz, MODIS Rapid Response Team


Dec. 22, 2008

Tropical Storm Billy Gets a Second Chance at Life

AIRS image of Tropical Storm Billy Credit: NASA JPL/Ed Olsen
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Tropical Storm Billy was almost written off once he made landfall in northwestern Australia over the weekend of Dec. 20-21, but has crossed back into the waters of the Indian Ocean. That means an extended life for Billy. Meanwhile, what was once tropical storm Cinda located further north, has dissipated in the open waters of the Indian Ocean.

On Monday, December 22 at 12:00 Zulu Time (7 a.m. EST), Tropical Storm Billy was located over Yampi Sound, an inlet of the Indian Ocean. Yampi Sound, located in northwestern Australia is 60 miles long (100 km). It is a deep channel off the submerged coast of the Kimberley region. Locally, it is called the "Yampi Peninsula" and is located between Collier Bay and King Sound. That's also about 640 miles east-northeast of Learmonth, Australia, and near 16.3 degrees north latitude and 123.4 degrees east longitude.

Billy's maximum sustained winds are near 40 knots (46 mph) with higher gusts. He's moving southwestward at 6 knots (7 mph) near the Kimberly coastline of northwestern Australia. Because Billy is moving into open waters where strengthening is more favorable, he is expected to intensify in the next couple of days while staying at sea.

The Joint Typhoon Warning Center is the organization that forecasts tropical cyclones in that area of the world and they use data from various satellites to help make their forecasts. The infrared imagery of the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite is one of those used, that identifies cloud temperatures. 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.

The infrared image, taken on Dec. 22 at 12:35 a.m. EST (5:35 UTC) 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 the top of Billy. 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 shows Tropical Storm Billy just coming off the northwestern Australia coast and moving into the warm waters of the Indian Ocean.

AIRS infrared signal doesn't penetrate through clouds, so where there are clear skies AIRS reads the infrared (heat) signal from the ocean and land surfaces, revealing warmer temperatures (colored in orange and red). The orange temperatures are 80F (300 degrees Kelvin) or greater (the darker they are, the warmer they are). Tropical cyclones need sea surface temperatures of 80F to strengthen and maintain their strength.

Text Credit: Rob Gutro (from JTWC reports) NASA's Goddard Space Flight Center



Dec. 19, 2008

Billy and Cinda, a Couple of Indian Ocean Tropical Cyclones

Tropical cyclones Billy and Cinda formed in the Indian Ocean in the last day. Billy is eyeing a weekend landfall while Cinda will spin in the ocean over the weekend of December 19-21.

Tropical Cyclone Billy, also named "05S" is closest to land, as it lay 195 nautical miles southwest of Darwin, (western) Australia on Friday, Dec. 19 at 10 a.m. EST (15:00 Zulu Time). Specifically it was near 14.7 degrees north latitude and 128.4 degrees east longitude.

Billy has sustained winds near 45 knots (52 mph), and was moving west near 2 knots (2 mph). Billy is located over warm sea surface temperatures that will help it maintain its circulation, despite its close proximity to land. Billy is expected to make landfall around 00:00 Zulu Time on Dec. 20, or 9:30 a.m. local (Darwin) time.

Billy is forecast to make landfall near the Adolphus Channel and then move westward inland over Drysdale River National Park where it will dissipate.

Text Credit: Rob Gutro/NASA's Goddard Space Flight Center