Tuesday, 17 April 2018
Champions DEFGH (Sawgrass Marriott)
Chris Vagasky, Vaisala, Inc., Louisville, CO
Hurricanes Irma, Jose, and Maria impacted the Atlantic Basin between 30 August and 30 September 2017. Hurricanes Irma and Maria both reached Category 5 intensity, with maximum sustained wind speeds of 160 and 150 knots, respectively; Hurricane Jose attained a maximum intensity of Category 4, with peak wind speeds of 135 knots. The three hurricanes each developed in the Main Development Region of the tropical Atlantic Basin and moved through portions of the Caribbean during their life cycles. At their peak intensities, Hurricanes Irma and Maria exhibited periods during which an enveloped eyewall lightning (EEL) signature was present, in which lightning completely enveloping the eyewall was detected by the Vaisala Global Lightning Dataset, GLD360. Hurricane Jose did not exhibit the EEL signature during its life cycle.
A review of 82 global Category 4 and 5 TCs between 2012 and 2015 found 32 with the EEL signature, and that those TCs were statistically significantly stronger than TCs without the EEL signature. The mechanisms behind the EEL signature are not fully known yet, and this paper seeks to help improve the understanding of the EEL signature. Using data from the Statistical Hurricane Intensity Prediction Scheme (SHIPS), environmental parameters for Hurricanes Irma, Jose, and Maria are examined. SHIPS has previously been used to identify favorable environments for overshooting tops in TCs and to study how sea surface temperature and vertical wind shear impact lightning in TCs. Irma, Jose, and Maria provide a unique set of TCs to analyze, with all three occurring over a 30 day period in the same geographic region. Comparisons will be made between the environmental parameters for all three storms, in an effort to understand why Irma and Maria produced significant eyewall lightning while Jose did not.
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