Tropical Storm Don formed at 5 p.m. EDT last night, July 27, in the southern Gulf of Mexico, the fourth tropical storm to form in the 2011 Atlantic hurricane season.
The storm began as the low pressure area called System 90L, strengthened quickly into tropical depression number 4, and then became Tropical Storm Don.
Images from NASA's GOES-13 satellite show the storm to be around 100 miles (160 kilometers) in diameter, with tropical storm-force winds (those between 39 and 73 mph, or 63 and 118 kph) extending 45 miles (72 km) from Don's center. At 5 a.m. EDT on July 28, Don had maximum sustained winds near 40 mph (65 kph). It was located about 495 miles (796 km) east-southeast of Brownsville, Texas.
Don is moving toward the west-northwest near 10 mph (17 kph) and is expected to continue on this track through Friday, according to the National Hurricane Center. Don is also expected to speed up.
As of July 28, a tropical storm watch is in effect for Texas coast from the mouth of the Rio Grande northward to west of San Luis Pass and those conditions are possible by late Friday.
The 2011 hurricane season has gotten off to a slow start, with only four tropical storms (Arlene, Bret, Cindy and now Don) and no hurricanes so far. But typically the most active part of the season comes in August and September.
The season is expected to be a doozy, with the U.S. National Oceanic and Atmospheric Administration (NOAA) forecast predicting between six to 10 hurricanes, three to six major hurricanes (those with winds of up to 111 mph (179 kph) or higher) and 12 to 18 named storms (tropical storms and hurricanes receive names).
The 2010 season was one of the busiest ever, with 12 hurricanes in the Atlantic the second-highest number on record, tied with 1969 and 19 named storms, a tie with 1887 and 1995 as the third-busiest on record. An average Atlantic season produces 11 named storms, six hurricanes and two major hurricanes. The busiest season on record remains 2005, which saw 28 named storms, including Hurricane Katrina .