Dry air could prevent Tropical Storm Katia from strengthening

[News_Editor]

Dry air could prevent Tropical Storm Katia from strengthening

2011-08-31 21:34:16 GMT+7 (ICT)

MIAMI (BNO NEWS) -- Tropical Storm Katia, located in the eastern Atlantic, continued to gradually strengthen on Wednesday morning, forecasters said, but dry air could threaten development of the system later this week.

Katia formed in the far eastern Atlantic on Tuesday morning after it emerged as a large area of showers and thunderstorms off the west coast of Africa on Saturday evening. It became better organized in association with a low pressure area.

As of 5 a.m. AST (0900 GMT) on Wednesday, the center of Katia was located about 985 miles (1585 kilometers) west of the southernmost Cape Verde Islands. It is moving toward the west-northwest at a speed near 21 miles (33 kilometers) per hour, a general motion which is expected to continue during the next few days.

Maximum sustained winds of Katia have increased to near 65 miles (100 kilometers) per hour, with higher gusts. "Satellite imagery this morning indicates that Katia is gradually becoming better organized," said Jack Beven, a senior hurricane specialist at the U.S. National Hurricane Center. "The primary convective band has wrapped farther around the center, and the cloud tops in the band have cooled."

Katia is expected to reach hurricane strength on Wednesday afternoon, and then become a category two hurricane on Thursday afternoon. The storm is currently forecast to become a major, category three, hurricane by Sunday morning, but dry air and other factors could prevent this.

"A couple of issues have appeared regarding the intensity forecast. First, water vapor imagery and microwave total precipitable water data shows dry air not far to the north and east of the core of Katia," Beven said, adding that this has not yet affected development of the system.

"However, there is a possibility that intensification could be slower than forecast if the dry air reaches the center," Beven explained. In addition to the dry air, weather models also indicate that Katia could face strong southwesterly shear later this week, which could also weaken Katia.

As of Wednesday morning, Katia is heading in the direction of the Caribbean, although forecasts show the system should turn toward the northwest on Friday. This would take the storm well north of Puerto Rico, staying away from any land.

But the exact forecast is uncertain, and there is still a chance Katia could be a threat to the Caribbean as the most recent 5-year average errors at this forecast time is about 250 miles (402 kilometers). Forecasts later this week will better determine which countries, if any, are at risk.

Katia was added to this year's rotating storm roster to replace Katrina which killed more than 1,800 people in August 2005 when it made landfall near the Louisiana-Mississippi border. Storm names are retired when they cause a large number of fatalities.

Katia is the eleventh named storm of the 2011 Atlantic hurricane season, following Tropical Storm Jose which formed south of Bermuda on late Sunday afternoon. Jose passed west of Bermuda, causing minor damage but no casualties.

According to figures released earlier this month, NOAA's Climate Prediction Center is expecting an above-normal hurricane season in the Atlantic this year. The outlook calls for 14 to 19 named storms, with seven to ten becoming hurricanes and three to five expected to become a major hurricane (category 3 or higher).

An average Atlantic hurricane season produces 11 named storms, with six becoming hurricanes and two becoming major hurricanes. The Atlantic hurricane season runs from June 1 through November 30, with peak activity in September.

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