Summer Mean and Extreme Precipitation Over the Mid-Atlantic Region: Climatological Characteristics and Contributions From Different Precipitation Types

Based on a long-term observational data set from the tracking of mesoscale convective systems (MCSs), isolated deep convection (IDC), and tropical cyclones (TCs), we examine the climatological characteristics of summer (June-August) mean and extreme precipitation during 2004-2017 and their respective contributions from MCS, IDC, TC, and non-convective (NC) systems and the local versus remote influence of MCS and IDC over the Mid-Atlantic region (MAR). On average, MCS, IDC, TC, and NC contribute 22%, 29%, 4%, and 45% to the total summer mean precipitation in the region. While MCS and TC precipitation primarily occurs in the coastal areas east of the Appalachian Mountains, IDC precipitation is more concentrated in the southern MAR and near the mountain windward slopes. Each summer, similar to 41 MCSs with an average lifetime of 19.6 h influence the MAR, with 80% initiated outside and traveling on average 10 h before their centroids enter the region. Around 13 MCSs initiated in the Great Plains and Midwest propagate across the Appalachian Mountains and contribute 20%-40% to MCS precipitation in the central Mid-Atlantic coastal areas each summer. In contrast, similar to 2000 IDC events with an average lifetime of 2.0 h influence the MAR each summer, and 77% are initiated locally. MCS, IDC, TC, and NC contribute 31% (30%), 26% (31%), 17% (7%), and 26% (32%) to the top 1% (5%) extreme daily precipitation, respectively. Considering extreme hourly precipitation, however, the IDC contributions increase to 41% (top 1%) and 38% (top 5%) due to the frequent occurrence and large intensity of IDC precipitation.