Simplify the following text for a Grade 8 native English-speaking person.
Original: After fluctuating in intensity for four days , Isabel gradually weakened and made landfall on the Outer Banks of North Carolina with winds of 105 mph ( 165 km\/h ) on September 18 .
Simplified: After weakening and strengthening for four days , Isabel slowly weakened . It moved onto the Outer Banks of North Carolina with winds of 105 mph ( 165 km\/h ) on September 18 .