October 1, 2009
It's a Boy? Tropical Depression 18-E Forms in the Eastern North Pacific
Hurricane Season 2009: Tropical Depression 18E (Eastern Pacific)
At 11 a.m. EDT on October first, the eighteenth tropical depression of the Eastern Pacific hurricane season was born. He's a little guy, but is likely going to grow up to be a tropical storm and get the name Olaf later today or tomorrow. He's not, however, expected to reach hurricane strength.
At the time of his birth, Tropical Depression 18-E (TD18E) had maximum sustained winds near 35 mph. He was located 580 miles west-southwest of the southern tip of Baja California, near 19.0 North and 117.9 West. TD18-E was moving west-northwest at 8 mph and is expected to turn toward the northwest later today or tonight. His estimated minimum central pressure is 1004 millibars.
Forecasters at the National Hurricane Center confirmed TD18E's birth using data from NASA's Atmospheric Infrared Sounder (AIRS) instrument combined with data from the Advanced Microwave Sounding Unit (AMSU) data to create a microwave of the storm. Both AIRS and AMSU are instruments that fly on NASA's Aqua satellite.
NASA's Aqua satellite flew Tropical Depression 18E five and a half hours before it was born. Aqua's instruments were used to create a microwave image from 5:23 a.m. EDT on October 1 that showed high thunderstorms, a sign that the storm was intensifying. The imagery revealed cold areas in the storm that indicate ice in cloud tops, and light to moderate precipitation. The National Hurricane Center reported " overnight microwave (and scatterometer data from NASA's QuikScat satellite) data indicate that the circulation associated with the broad low pressure area southwest of the southern tip of Baja California has become better defined.
The Hurricane Center also said that "The depression does not appear to have much of an opportunity to strengthen. Southerly to southwesterly vertical shear is forecast to increase later today and become stronger thereafter." In addition, TD18E is going to start moving into cooler waters on its northward track.
Rob Gutro, NASA/Goddard Space Flight Center