MIAMI (AP) _ Hurricane Alberto, the first hurricane of the Atlantic season, strengthened slightly early Monday, but forecasters predicted the storm would not become much stronger.

Forecasters said some computer models predicted the storm would interact with an upper-level trough in the mid Atlantic which would pull it toward colder water and weaken it.

``Alberto has made its nightly westward wobble again,'' said Stacy Stewart, a hurricane specialist with the National Hurricane Center in Miami. ``Alberto is expected to stay on a general west-northwest track.''

However, it was also possible the trough could bypass the storm to the north, which would result in a more westward track than forecast, he said.

``If it continues its present motion, it would likely miss the Caribbean islands, it would pass just to the north of them,'' Stewart said. ``If it moves to the northwest, it misses it completely and lessens a threat to the United States.''

By Monday morning, Alberto was still far from land, with the closest being the Leeward Islands, more than 1,300 miles away, Stewart said. The storm was moving west-northwest at near 15 mph.

The hurricane's top sustained wind blew at 90 mph early Monday and was unchanged by late in the morning. Hurricane-force wind extended 25 miles from the center, with tropical storm-force wind extending 105 miles.

The storm become a hurricane Saturday after crossing the 74 mph top sustained wind threshold. Its wind speed increased by 5 mph during a six-hour period from late Sunday to early Monday.

``That's what we consider no significant change in intensity,'' Stewart said.

While hurricane forecasts normally are considered fairly accurate up to three days, it was still too early to predict if Alberto might pose a threat to the United States or the Caribbean.

``If the trough doesn't pick it up, then it could continue in the general direction of the United States, but there's still no guarantee that it would hit us,'' Stewart said.

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National Hurricane Center: http://www.nhc.noaa.gov/