The mistake in the original sentence that should jump out at you is at the end of the underlined portion: "to study...and analyzing." Those two verbs need to be parallel, for example, "to study...and to analyze." Thus, (A) is wrong.

Scan the remaining choices for parallel construction. (B), (C), and (D) alter the structure of the sentence so that the two verbs are no longer part of the same list, so those will have to be evaluated independently. (E) uses proper parallelism, with "have studied...and analyzed."

(B) is wrong because the first clause is a modifier and the subject that follows it is not correct. The meteorologists made the observation, so "meteorologists" should be the first word after the comma. (D) has the same problem despite a different modifier. (C) alters the meaning of the sentence, suggesting by the use of the word "when" that the observation of the new pattern and the study of the once-rare storm types are simultaneous. (E) is correct.