Surface cold pools in the outer rainbands of Tropical Storm Hanna (2008)

This study documents the structure and evolution of surface cold pools associated with three outer rainbands that moved over a coastal mesonet in North Carolina during the landfall of Tropical Storm Hanna (2008). The convective structure and cold pools of each rainband were examined. Strong cold pools were regularly observed beneath those rainband segments with maximum radar reflectivities exceeding 50 dBZ, whereas less intense segments exhibited weaker or no cold pools. The cold pools extended 50-100 km in the cross band direction and showed signs of cross-band expansion through enhanced outflow (inflow) – relative to the cyclone center – along the leading (trailing) edges. Evidence suggests that the strong cold pools were also advected downband toward the cyclone center. The local environment was characterized by moderate CAPE, minimal helicity, and a prominent dry air intrusion that collectively favor the development of strong cold pools. A synopsis of our results and their comparison with previous mid-latitude and tropical cold pools will be presented at the conference.