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Hurricane Season 2009: Isang (Western Pacific)
07.20.09
 
July 20, 2009

Typhoon Isang (a.k.a. Molave) Made Landfall Near Hong Kong

satellite image of Isang NASA's Terra satellite captured an image of Typhoon Isang (Molave) on July 19 after it made landfall near Hong Kong. Credit: NASA's MODIS Rapid Response Team
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On Saturday, July 18 at 11 a.m. EDT (1500 UTC) Isang (Molave) strengthened to typhoon strength with sustained winds near 74 mph and made landfall near Hong Kong after midnight July 19 with sustained winds near 90 mph.

According to press reports from China Daily.com, Molave made landfall specifically at Nanao town in Shenzhen City of Guangdong Province at 12:50 a.m. Sunday, Beijing Time. At landfall, it had maximum sustained winds near 90 mph, making it a Category One Typhoon. It brought gusty winds and heavy rains to Shenzhen City creating some street flooding. The largest rainfall recorded from Molave was 10.04 inches (255 millimeters) over three hours in Dianbai County, China.

NASA's Terra satellite flew over Molave on Sunday July 19 at 11:20 a.m. local time (03:20 UTC) about 18 hours after the storm made landfall. The Moderate Imaging Spectroradiometer captured a visible image of the storm's clouds as it continued to move west-northwest near 16 knots (18 mph). At that time, its sustained winds had dropped down to 40 knots (46 mph) and it was located near 23.0 north latitude and 112.4 east longitude) in China's Guangxi Province, about 110 miles west-northwest of Hong Kong.

Molave's remnants are dissipating today, July 20.

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



July 17, 2009

QuikScat saw Isang's (Molave's) winds on July 17 when they were over 46 mph (in purple). > View larger image
QuikScat saw Isang's (Molave's) winds on July 17 when they were over 46 mph (in purple).
Credit: NASA JPL, Pedro Falcon III
The AIRS instrument showed the large extent of Isang's cold clouds and rains (in blue and purple). > View larger image
The AIRS instrument showed the large extent of Isang's cold clouds and rains (in blue and purple) over the northern part of the Philippines on July 16. The colder the clouds, the higher they are, and the stronger the thunderstorms. Purple indicates higher clouds than blue.
Credit: NASA JPL, Ed Olsen
Isang Gets a Name Change, Strength Increase, Forecast Landfall

The storm known as Isang in the Philippines has been renamed Molave and is headed for a landfall just north of Hong Kong over the weekend.

Isang's (Molave) winds strengthened into a tropical storm and before it makes landfall in mainland southeastern China this weekend, it is expected to briefly reach typhoon strength. At 11 a.m. EDT on July 17, Isang had sustained winds near 60 knots (69 mph) and was moving northwest near 16 knots (18 mph). It was located about 405 miles east-southeast of Hong Kong, near 20.6 north latitude and 121.2 east longitude.

The tropical storm has a long reach, as tropical storm-force winds of 34 knots (39 mph) extend as far out as 80 miles from the center. Isang is generating 16-foot high waves in the South China Sea. Although Isang is expected to reach typhoon status, it is forecast to make landfall in southeastern China as a strong tropical storm.

QuikScat saw Isang's winds swirling inside its clouds by using microwaves to peer into them. It flew over Isang and captured an image at 6:08 a.m. EDT on July 17. QuikScat can actually determine the speed of a tropical cyclone's rotating winds using microwave technology. QuikScat imagery is false-colored to show different wind speeds, the highest winds are always shown in purple, indicating winds over 40 knots (46 mph). Small barbs are used in the images to indicate wind direction and point to areas of heavy rain.

While QuikScat took a look at Isang's winds, the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite identified the storm's icy cloud temperatures. Those temperatures help determine the height the clouds and thunderstorms. The colder the clouds, the higher they are, and the stronger the thunderstorms. The satellite image, which false-colors clouds based on their temperature, shows a large extent of cloud cover. In AIRS images, purple indicates the highest thunderstorms (and strongest), and blue areas are the second coldest and highest clouds.

Whatever the residents of southeast China decide to call the storm, whether Isang or Molave, they'll still call it very wet and very windy as it makes landfall.

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



July 16, 2009

This TRMM satellite image shows that about 1 inch of rain is falling in an hour near the center of Tropical Storm Isang. > View larger image
This TRMM satellite image shows that about 1 inch of rain is falling in an hour near the center of Tropical Storm Isang as it heads to north Luzon, the Philippines.
Credit: NASA/SSAI, Hal Pierce
Tropical Storm Isang to Brush Northern Luzon, the Philippines

Isang has strengthened into a tropical storm and it threatens to graze northern Luzon in the Philippines with rainfall from its outer bands. NASA and the Japanese Space Agency's Tropical Rainfall Measuring Mission satellite (TRMM) are monitoring the rainfall amounts in Isang as it closes in.

On Thursday, July 16, 2009 at 11 a.m. EDT, Isang was 270 nautical miles northeast of Manila, around 17.8 north latitude and 124.0 east longitude. Isang was moving west-northwest near 10 mph. It has sustained winds near 42 mph (35 knots) and its area of rainfall has been expanding as it nears Northern Luzon. Satellite imagery indicated that Isang is becoming more organized, and that the rainfall is persisting mostly on the southern edge of the storm.

As a tropical storm, Isang is generating a good amount of rainfall over the open ocean on its course for northern Luzon. TRMM acts like a "rain gauge in space" and can estimate rainfall in storms. On July 15 at 2:37 p.m. EDT, TRMM flew above Isang and captured an image of rainfall happening throughout the storm.

Creating an image of TRMM's rainfall in a storm takes some doing. Hal Pierce at NASA's Goddard Space Flight Center in Greenbelt, Maryland, where TRMM is managed, assembles images from various TRMM instruments. To create an image of rainfall analysis, Hal uses data from the TRMM Microwave Imager and Precipitation Radar instruments and overlays it on a TRMM infrared image. The analysis showed moderate rainfall of 20-30 millimeters per hour (~1 inch) in an area near the center of circulation.

Isang is expected to pass northern Luzon and veer toward Hong Kong.

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



July 15, 2009

Tropical Depression Isang is pictured on the right of this NASA Aqua satellite image. > View larger image
Tropical Depression Isang is pictured on the right of this NASA Aqua satellite image that was taken by the AIRS instrument that flies aboard it. Isang is expected to strengthen into a tropical storm as it passes the Philippines to the north.
Credit: NASA JPL, Ed Olsen
Isang Is the Third Tropical Depression in a Week in Western Pacific

The Western Pacific Ocean has now spawned its third tropical depression this week, and the week is only half over! Tropical Depression 07W, referred to in the Philippines as "Isang" will skirt the eastern side of the main island this week before a landfall in China over the weekend.

Although Tropical Depression Isang (07W) isn't expected to make a landfall in the northern Philippines it is expected to bring heavy rainfall as it passes by.

On July 15 at 11 a.m. EDT, Isang was located about 375 nautical miles east of Manila, the Philippines near 15.6 north and 127.2 east. It had maximum sustained winds near 28 mph, and was moving northwest near 11 mph.

Forecasters at the U.S. Navy's Joint Typhoon Warning Center have noted that the storm could intensify into a tropical storm in the next 72 hours, and will be closely monitoring data from various satellites to watch its intensity.

The Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite captured this visible image of Isang on July 15, at 1:15 a.m. EDT as the satellite flew overhead as it was approaching the Philippines.

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