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Hurricane Season 2011: Tropical Storm 27W (Western North Pacific Ocean)
TRMM provided a › View larger image
TRMM provided a "top down" rainfall analysis of Tropical Storm 27W on Dec. 13 at 10:33 a.m. EST. Light to moderate rainfall (green and blue) was falling at a rate between .78 to 1.57 inches/20 to 40 mm per hour northeast and west of the center. The satellite overpass missed the southeastern side of the storm (not shown here).
Credit: SSAI/NASA, Hal Pierce
27W Now a Tropical Storm, NASA Eyes Rainfall from Space

Tropical Depression 27W strengthened into a tropical storm today and is expected to continue strengthening as it makes its way toward the central Philippines. NASA's TRMM satellite analyzed its rainfall rates yesterday and saw moderate rainfall in two quadrants of the storm.

The Tropical Rainfall Measuring Mission (TRMM) satellite saw then tropical depression 27W on December 13, 2011 at 1533 UTC (10:33 a.m. EST). It was upgraded to a Tropical storm by the Joint Typhoon Warning Center (JTWC) the next day, Dec. 14 at 0900 UTC. TRMM's Microwave Imager (TMI) showed that moderate rainfall was located in clusters of strong convective storms within the developing tropical cyclone. The strongest thunderstorms were located to the north of the center of circulation and there were multiple bands of thunderstorms to the south of the center.

On Dec. 14, 2011 at 1500 UTC (10 a.m. EST), Tropical Storm 27W was about 150 nautical miles south of Yap, near 6.9 North latitude and 137.0 East longitude. Yap is an island in the Caroline Islands and is a state of the Federated States of Micronesia. TS27W is moving to the west-northwest at 14 knots (16 mph/26 kmh).

Tropical Cyclones can form in the western Pacific Ocean at any time during the year but they occur most frequently during the months of June through November so tropical storm 27W (TS27W) is a little unusual.

Tropical storm 27W has been predicted to intensify to minimal typhoon strength with winds of 65 knots (~75 mph) before moving over the southern Philippines in the next couple days. In a typical year 6-9 tropical cyclones cross over the Philippines. This year has been unusually deadly with typhoons Nesat and Nalgae causing heavy flooding and loss of life in the Philippines in late September and early October.

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

Dec. 13, 2011

visible light satellite image of TD27W › View larger image
The MODIS instrument on NASA's Aqua satellite captured this visible image of Tropical Depression 27W on Dec. 13 at 0416 UTC (Dec. 12 at 11:16 p.m. EST). TD27W is about 415 miles south of Andersen Air Force Base, Guam. Credit: NASA/NRL
Another New Tropical Depression Forms in Western North Pacific

Tropical Depression 27W formed in the western North Pacific Ocean today, on the heels of Depression 26W, which is now fading.

Tropical Depression 27W (TD27W) formed at 0900 UTC (4 a.m. EST) and by 1500 UTC (10 a.m. EST) was located about 415 miles south of Andersen Air Force Base, Guam. It was centered near 6.4 North latitude and 143.3 East longitude moving to the west-northwest near 18 knots (20 mph/33 kmh). TD27W's maximum sustained winds were near 30 knots (34 mph/55 kmh).

The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA's Aqua satellite captured a visible image of Tropical Depression 27W on Dec. 13 at 0416 UTC (Dec. 12 at 11:16 p.m. EST). The strongest thunderstorms appeared around the center of circulation. Those were also the highest thunderstorms, and they cast shadows on the surrounding lower clouds. An area of central dense overcast has developed over the low-level center of circulation that is about 120 nautical miles in diameter. The forecasters at the Joint Typhoon Warning Center noted that 27W is in an area of low wind shear, which will allow it to strengthen.

The Joint Typhoon Warning Center noted that TD27W threatens to bring parts of the Philippines gusty winds and heavy rainfall. TD27W is expected to intensify to typhoon strength as it moves toward Mindanao. Currently, a tropical storm watch is posted for Koror and Kayangel in Palau, and Ngulu in Yap.

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