Sep 22, 2016

Record Rains in Norfolk From Julia's Remnants

Kempsville, Virginia Beach, VA
USA
by
Jeff Masters and Bob Henson
,
Weather Underground
Precipitation analyzed for the 7-day period ending at 12Z (8:00 am EDT) Thursday, September 22, 2016. Widespread 10-15” totals have occurred over southeast VA and northeast NC since Monday in association with the remnants of Tropical Storm Julia. Image: NOAA/NWS Advanced Hydrologic Prediction Service
Precipitation analyzed for the 7-day period ending at 12Z (8:00 am EDT) Thursday, September 22, 2016. Widespread 10-15” totals have occurred over southeast VA and northeast NC since Monday in association with the remnants of Tropical Storm Julia. Image: NOAA/NWS Advanced Hydrologic Prediction Service

One of the clearest changes in weather globally is the increasing frequency of heavy rain.[1] As the global average temperature increases, so too does the ability of the atmosphere to hold and dump more water when it rains.[2] The average moisture content of the atmosphere has increased by about 4 percent since the 1970s, as expected from the Clausius–Clapeyron law, and Storms reach out and gather water vapor over regions that are 10-25 times as large as the precipitation area, thus multiplying the effect of increased atmospheric moisture.[2][3]

A slow-moving slug of atmospheric moisture associated with former Tropical Storm Julia took up residence this week across the Mid-Atlantic. Together with a lingering front, the moisture has fueled several days of heavy rainfall in southeast Virginia and northeast North Carolina. Preliminary rainfall totals for the period from Sunday through Wednesday night included 13.73” near the Kempsville area of Virginia Beach, VA. By and large, the rains have been prolonged but not extremely intense, producing mainly widespread road closures.

The hardest-hit metropolitan area is Hampton Roads, VA, including Norfolk and Portsmouth. In the 72 hours ending at midnight Wednesday night, Norfolk International Airport picked up 9.35” of rain. That includes three consecutive days of daily-record precipitation: 3.04” on Monday, 2.38” on Tuesday, and 3.93” on Wednesday. As noted by Capital Weather Gang, this is the only instance of three consecutive daily precipitation records in Norfolk data going back to 1874, according to local weathercaster Tim Pandajis. The city’s wettest September--13.80”--occurred in 1979, when Norfolk experienced deluges from Hurricane David as well as a tropical depression later that month. As of this morning, Norfolk’s total for this September was up to around 13”. With showers still in the area today, the September 1979 record is in striking distance