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.