NASA - National Aeronautics and Space Administration

Fourth Tropical Depression in Eastern Pacific Set to Fizzle

Hurricane forecasters are watching the fourth tropical depression (TD) in the eastern Pacific Ocean on Tuesday, July 10, 2007. So far, two of the previous three tropical depressions made it to tropical storm strength and received names. Those were Tropical Storms Alvin and Barbara. If TD-4 strengthens into a tropical storm it would be named "Cosme," however, forecasters expect it to weaken in the two days before dissipating.


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This satellite image of TD-4 is from the National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite (GOES-11). This image, taken at 14:15 Universal Time (7:15 a.m. Pacific Daylight Time (PDT)) was created by NASA's GOES Project Science Office at NASA's Goddard Space Flight Center, Greenbelt, Md.

The center of TD-4 was located near 18.6 north and 120.8 west as of 1500 Zulu Time (8:00 a.m. PDT) on July 10. TD-4 was moving northwest at 7 knots (8 mph), and had an estimated minimum central pressure of 1006 millibars. Its maximum sustained winds were at 30 knots (34 mph), with gusts to 40 knots (46 mph).

The National Hurricane Center reporters that the depression is currently being steered around the western periphery of a ridge of high pressure to the east and a weakness to the north caused by presence of a mid-level trough (and elongated area of low pressure). Computer models forecast a northwestward track for the next 24 hours or so followed by a turn more toward the west-northwest. As the cyclone weakens it will likely be steered by the low-level winds.

Despite the current deep convection (rising air that helps created thunderstorms) both atmospheric and oceanic conditions are not favorable for intensification. The sea surface temperatures are below 25 degrees Celsius (77 degrees Fahrenheit) and upper-level winds forecast to increase. Waters need to be at least 80 degrees Fahrenheit to power tropical cyclones, and they're just too cool in that area to help the storm strengthen. Upper level winds can shear a storm apart, and the current winds are expected to help gradually weaken TD-4 into a remnant Low pressure system in 36 hours.

Caption Credit: Rob Gutro, Goddard Space Flight Center, from National Hurricane Center reports