By Rob Gutro, NASA’s Goddard Space Flight Center

The first tropical depression of the eastern Pacific Ocean season is making landfall in Mexico and has drenched the state of Sinaloa already.

On June 19, as Tropical Depression One-E (“E” for Eastern Pacific) was trudging into western Mexico, and the state of Sinaloa, it was dropping between 4 and 8 inches of rain, with higher amounts in isolated areas. Tropical Storm Warnings are in effect.

At 11:00 a.m. EDT the center of Tropical Depression One-E (TD1-E) was located near latitude 21.0 north and longitude 107.1 west or about 160 miles south-southwest of Mazatlan, Mexico.

TD-1E's thunderstorms (in blue and purple) are seen as a perfectly round shaped off the western Mexican coast in this Aqua satellite AIRS image. Image by NASA JPL, Ed Olsen

The depression is moving toward the north-northeast near 10 mph and will gradually turn north while slowing down. TD1-E’s center will be near Las Islas Marias today and near the mainland coast of Mexico on June 20. Its current forecast track brings the center of TD1-E between the towns of Culacan and Mazatlan.

Maximum sustained winds are near 35 mph with higher gusts. There is still a possibility that the depression could become a tropical storm later on June 19. Estimated minimum central pressure is 1003 millibars.

The Atmospheric Infrared Sounder (AIRS) instrument on NASA’s Aqua satellite captured an infrared image of the low pressure area on June 19 at 4:35 p.m. EDT (8:35 UTC. In the infrared image, TD1-E’s cold clouds (in purple) resemble a tight almost perfect circle. It is located right next to the western Mexican coast. The storm’s lowest temperatures (in purple) are associated with high, cold cloud tops. Those temperatures are as cold as or colder than 220 degrees Kelvin or minus 63 degrees Fahrenheit (F). The blue areas are around 240 degrees Kelvin, or minus 27F.

What’s that Other Huge Area of Cold Clouds?

The other huge rounded area of purple and blue (high clouds) over the Mexico/Texas border is a mesoscale convective complex (MCC). In an MCC, the area of cold cloud tops exceeds 39,000 square miles with temperatures less than or equal to −32 °C (−25.6 °F); and an area of cloud top of 19,000 square miles with temperature less than or equal to −52 °C (−61.6 °F). They must maintain that size for more than six hours to be considered an MCC, and they’re long-lived, form at night (or early morning, pre-dawn) and have heavy rainfall, wind, hail, lightning and possibly tornadoes. This AIRS image shows that the core area has temperatures colder than -76F (-60 C). So, that other system isn’t a tropical depression, it’s an MCC.

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The Central Pacific Hurricane Center (CPHC) issues tropical cyclone warnings, watches, advisories, discussions, and statements for all tropical cyclones in the Central Pacific from 140 Degrees West Longitude to the International Dateline. The season officially begins on June 1 and ends on November 30. However, tropical cyclones can occur at any time. The National Weather Service Forecast Office in Honolulu activates the CPHC when: (1) a tropical cyclone moves into the Central Pacific from the Eastern Pacific, (2) a tropical cyclone forms in the Central Pacific, or (3) a tropical cyclone moves into the Central Pacific from the West.