image: On Sept. 25 at 2:05 a.m. EDT (0605 UTC) the AIRS instrument aboard NASA's Aqua satellite showed some strong thunderstorms (purple) in Pilar, as cold as or colder than minus 63 degrees Fahrenheit (minus 53 Celsius) along the coast, producing heavy rainfall. view more
Credit: Credits: NASA JPL, Ed Olsen
Tropical Storm Pilar formed near the southwestern coast of Mexico on Saturday, Sept. 23 and continued hugging the coast when NASA's Terra and Aqua satellites passed overhead. Pilar weakened to a tropical depression during the late morning on Sept. 25.
The Moderate Resolution Imaging Spectroradiometer or MODIS instrument that flies aboard NASA's Terra satellite captured a visible picture of Tropical Storm Pilar on Sept. 24 at 1:40 p.m. EDT (1740 UTC). At the time Pilar's center was just off the coast of southwestern Mexico and the storm's clouds and showers extended over the Mexican states of Jalisco, western Zacatecas, southern Sinaloa and southern Durango.
An infrared image of Pilar was taken from the Atmospheric Infrared Sounder or AIRS instrument aboard NASA's Aqua satellite on Sept. 25 at 4:53 a.m. EDT (0853 UTC). AIRS measured cloud top temperatures with infrared light. The data showed some strong thunderstorms as cold as or colder than minus 63 degrees Fahrenheit (minus 53 Celsius) along the coast. NASA research has shown that storms with cloud tops that cold have the ability to produce heavy rainfall.
The National Hurricane Center (NHC) said that although Pilar weakened to a depression (after Aqua passed overhead), those strong storms are expected to bring locally heavy rainfall and flooding in the Mexican states of Nayarit, Sinaloa, and Durango.
At 9 a.m. MDT (11 a.m. EDT/1500 UTC), the center of Tropical Depression Pilar was located near 22.8 degrees north latitude and 107.0 degrees west longitude. That's about 45 miles (75 km) southwest of Mazatlan, Mexico.
The depression is moving toward the north-northwest near 7 mph (11 kph) and this general motion is expected to continue for the next day or so until Pilar dissipates. On the forecast track, the center of Pilar is expected to remain just offshore of the coasts of the Mexican states of Nayarit and Sinaloa today.
Maximum sustained winds have decreased to near 35 mph (55 kph) with higher gusts. Additional weakening is forecast, and Pilar is expected to become a remnant low later today and dissipate by Tuesday, Sept. 26.
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For forecast updates on Pilar, visit the National Hurricane Center website: http://www.nhc.noaa.gov.