Input (grade 13): On July 18, Estelle intensified into a hurricane, and located in a favorable environment, Estelle continued strengthening to become the first major hurricane of the season on July 20.
Output (grade 11): On July 18, it intensified into a hurricane. In an environment that favored an increase of the storm's winds, Estelle continued strengthening, and became the first major hurricane of the season on July 20.