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Hurricane Season 2009: Nora (Eastern Pacific)
09.25.09
 
September 25, 2009, second update

NASA's AIRS instrument captured this visible image of Nora seen as a round area of clouds. > View larger image
NASA's AIRS instrument captured this visible image of Nora (top right) on September 24 at 1:30 p.m. PDT, seen as a round area of clouds.
Credit: NASA/JPL, Ed Olsen
Nora No More

Nora has just been archived in the eastern Pacific Hurricane history books today. The National Hurricane Center in Miami, Fla. issued their last advisory on her this morning, September 25 at 5 a.m. EDT.

Nora is a remnant low pressure area, creeping westward near 7mph. Although her sustained winds were near 35 mph at that time, she's weakening. She was located about 890 miles west-southwest of the southern tip of Baja California, near 17.2 north and 122.2 west. Here minimum central pressure was 1006 millibars.

NASA's Aqua satellite flew over Nora during the afternoon hours on September 24 and its Atmospheric Infrared Sounder (AIRS) instrument captured a visible image of the storm, already weakening. At that time, she had sustained winds near 50 mph, down from 60 mph.

Nora was declared a remnant low, because soon after Aqua passed over her, she didn't show any more organized deep convection. That's a sign that a storm has lost its tropical cyclone status.

Even though Nora is moving around in waters near 80F, warm enough to maintain a tropical cyclone, the National Hurricane Center said that "increasing wind shear and a dry mid-tropospheric environment should prevent any significant regeneration."

Elsewhere, there's a broad area of low pressure located about 800 miles southwest of Manzanillo, Mexico, which forecasters are now watching for slow development into a tropical cyclone. The low is producing disorganized showers and thunderstorms, and the National Hurricane Center said, "Some slow development of this system is possible over the next couple of days as it moves west-northwestward at 5 to 10 mph." The Hurricane center gives it less than a 30 percent chance of strengthening into a tropical cyclone over the weekend.

Text credit: Rob Gutro, NASA/Goddard Space Flight Center



September 24, 2009, second update

Nora was showing some areas of moderate rainfallwhen the TRMM satellite passed overhead on September 23, 2009. > View larger image
Nora was showing some areas of moderate rainfall (4 small red areas in the center) when the Tropical Rainfall Measuring Mission (TRMM) satellite passed overhead on September 23, 2009 at 2113 UTC (5:13 p.m. EDT).
Credit: NASA/SSAI, Hal Pierce
AIRS captured an infrared image of Tropical Storm Nora's cold clouds (purple). > View larger image
AIRS captured an infrared image of Tropical Storm Nora's cold clouds (purple) on September 24 at 5:17 a.m. EDT (blue circular area center of image). The Baja California coast is visible to the top right corner of the image.
Credit: NASA/JPL, Ed Olsen
NASA Satellites See Nora Power Up and Power Down

Since last night, Tropical Storm Nora has gained and lost strength and NASA's Aqua and Tropical Rainfall Measuring Mission (TRMM) satellites have seen that fluctuation.

Last night, September 23, by 8 p.m. EDT Nora had maximum sustained winds up to 60 mph. This morning by 11 a.m. EDT, Nora's sustained winds are back down to 50 mph. Nora was located about 760 miles west-southwest of the southern tip of Baja California, near 17.3 north and 120.0 west. She's moving west-northwest near 5mph, and is expected to move on a more westerly route in the next couple of days bringing her farther out to sea. Nora's minimum central pressure is near 1000 millibars.

NASA's TRMM satellite has been eyeing Nora's rainfall as a way to help determine fluctuations in her strength. In a satellite image captured on September 23, Nora had four areas of moderate rainfall around her center. The image was made at NASA's Goddard Space Flight Center in Greenbelt, Md. and it takes some ingenuity to create. The image combines the infrared and visible (VIRS) channels overlaid with a precipitation analysis from the TRMM Microwave Imager (TMI) and Precipitation Radar (PR) instruments.

Forecasters at the National Hurricane Center continually use TRMM data in their forecasting. At 11 a.m. EDT (8 a.m. PDT) on September 24, the National Hurricane Center discussion said "Nora is beginning to be affected by westerly vertical wind shear. Recent TRMM data indicated that the low-level center was near the western edge of the convective mass...which has increased over the last few hours."

NASA's Aqua satellite flew over Tropical Storm Nora and the Atmospheric Infrared Sounder (AIRS) instrument onboard captured an infrared image on September 24 at 5:17 a.m. EDT. Nora appeared as a small circular area of cold clouds on the image. Tropical storm-force winds in Nora only extend up to 50 miles from the center and the AIRS image of Nora's cold clouds reflect that distance. In AIRS infrared imagery, the colder the clouds, the higher they are, and the stronger the thunderstorms. There were some high, strong thunderstorm tops still apparent in Nora, with cloud top temperatures as cold as minus 63 Fahrenheit.

The National Hurricane Center expects Nora to weaken over the next couple of days because of wind shear in the upper-levels of the atmosphere that will tear into her circulation. Nora has likely peaked in intensity and is forecast to weaken to a tropical depression in 36 hours and even further into a remnant low in a few days.

Text credit: Rob Gutro, NASA/Goddard Space Flight Center



September 23, 2009, second update

Image on September 22 revealed that Nora had still not organized. > View larger image
This image on September 22 at 5:29 a.m. EDT revealed that Nora had still not organized enough at that time to be classified as tropical depression 17-E.
Credit: NASA/JPL, Ed Olsen
Seventeenth Tropical Depression Becomes Nora in E. Pacific

Tropical depression seventeen-e formed around 11 p.m. EDT Tuesday night and within twelve hours it strengthened into Tropical Storm Nora.

By 11 a.m. EDT today, Wednesday, September 23, Nora had maximum sustained winds near 45 mph, in the open waters of the eastern Pacific Ocean. Nora's center was about 665 miles southwest of the southern tip of Baja California, near latitude 16.5 north and 117.5 west. Nora is moving west-northwest near 9 mph. Nora's estimated minimum central pressure is 1002 millibars.

The Atmospheric Infrared Sounder (AIRS), instrument that flies aboard NASA's Aqua satellite, captured an image of Tropical Storm Nora yesterday at 5:29 a.m. EDT, that showed she was still coming together. Eighteen hours after the image was taken, Nora formed as tropical depression 17-E.

She's currently a small storm, as tropical storm-force winds only extend out to 40 miles from the center. Some strengthening is expected over the next 24 hours.

Text credit: Rob Gutro, NASA/Goddard Space Flight Center