  The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is a
ground-based air shower array designed to detect Cherenkov light produced in
water by secondary particles from atmospheric air showers. In order to improve
the sensitivity at the highest energies, especially for the shower cores
falling outside the main array, 345 smaller Water Cherenkov Detectors (WCDs)
were installed around the main array, the outrigger array. This extension
increased the instrumented area of HAWC by a factor of four. With the increased
size of the array, and the ability to detect shower particles further away from
the core, understanding of the time structure of the shower front is crucial
for accurate direction reconstruction and mandates proper modeling. In this
contribution, we present a model of the shower front as expected to be observed
by the outriggers obtained from Monte-Carlo simulations. Applying this model to
shower reconstruction, the improvements on air shower parameter are studied.
