Earth's Journal

Atmosphere Journal Entry

Earth's Journal

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Atmosphere Journal Entry

Aletta Kicks Off Eastern Pacific Hurricane Season (May 15, 2012)

TS Aletta

False-color satellite image shows rain bands of Tropical Storm Aletta swirling off the coast of Mexico. Areas of most intense rain are shown in blue and green. TRMM/Hal Pierce.

The 2012 hurricane season officially began today in the eastern Pacific Ocean. Right on cue, Tropical Storm Aletta formed off the southwestern coast of Mexico. The satellite shows its projected path moving away from land and out harmlessly to the open sea. Its peak winds were expected to top out at only 50 miles per hour (80 kilometer/hour), far below the minimum winds (74 mph or 118 km/h) for a hurricane.

Hurricane season in the western Atlantic Ocean kicks off on June 1, although it's possible for storms to arrive earlier. Meteorologists predict the 2012 Atlantic season will see less activity compared to 2011. One reason is strong high-level winds are now in place over the western and central Caribbean region. This increases wind shear (the change of wind speed or direction with altitude) which tears storms apart before they can grow large. In addition, atmospheric pressure near the surface in the Caribbean is not as low as it was this time last year.

Tropical storms form when huge amounts of humid air begin rising above warm tropical waters. Strong winds circulate faster and faster around the low pressure area formed in the center. The storm becomes a named tropical storm when its winds reach 39 mph (62 km/h).