Tropical Storm Sonia forms in Pacific, heads for Mexico

USPA News - Tropical Storm Sonia formed off Mexico`s Pacific coast on early Sunday morning, prompting tropical storm watches and warnings for portions of northwest Mexico`s mainland where it is expected to make landfall on Monday, U.S. forecasters said. Forecasters at the U.S. National Hurricane Center (NHC) had been following the weather system since Tuesday when it emerged as a large area of disturbed weather off southern Mexico.

An area of low pressure formed within the area by Wednesday, after which the system strengthened and was classified as a tropical depression on Thursday night, before being upgraded to a tropical storm on early Sunday. As of 7 a.m. PDT (1500 GMT), the center of Tropical Storm Sonia was located about 205 miles (335 kilometers) south of the southern tip of the Baja California peninsula in Mexico. The tropical cyclone is moving toward the north at a speed near 9 miles (15 kilometers) per hour, with a turn toward the north-northeast expected later on Sunday. "The recent strengthening appears to be the result of decreasing shear as Sonia moved beneath an upper-level ridge axis overnight", said NHC senior hurricane specialist Daniel Brown. "This relaxation in shear is expected to be short-lived as southwesterly upper-level winds ahead of a mid- to upper-level trough will cause a substantial increase in shear tonight, and no significant additional strengthening is expected." The center of Sonia is expected to pass south of the southern tip of Baja California later on Sunday, and will approach Mexico`s mainland by early Monday morning. A tropical storm warning was issued for coastal areas in the state of Sinaloa from Mazatlan to Altata, and a tropical storm watch was in effect from north of Altata to Topolobampo. "Some weakening is possible around the time Sonia reaches the coast as the shear is expected to cause the low- and mid-level centers to decouple. Sonia is forecast to dissipate shortly after landfall over the mountains of western Mexico", Brown explained, adding that Sonia is expected to become a remnant low by Tuesday. Forecasters said tropical storm conditions are expected to reach the warning area by late Sunday evening or early Monday morning. "Sonia is expected to produce total rain accumulations of 3 to 6 inches (7.6 to 15.2 centimeters), with isolated maximum amounts of 10 inches (25.4 centimeters), along the west coast of Mexico across portions of Sinaloa and western Durango", Brown said, warning that this may cause life-threatening flash floods and mudslides. Lorena is the eighteenth tropical cyclone of the 2013 Eastern Pacific hurricane season, which officially began on May 15. An average Eastern Pacific hurricane season produces 15 to 16 named storms, with eight to nine becoming hurricanes and four becoming major hurricanes. The Eastern Pacific hurricane season runs from May 15 through November 30, with peak activity from July through September.