Climate Summary

Temperature and Precipitation by climate division
Departures from Normal for August 2011
Based on Preliminary Data

August 2011 was warm and dry – and then along came Hurricane Irene, which you'll find highlighted in a special section below. While not as unusually warm as July was, August still brought the heat. For most cities in NC, temperatures in August ranked in the top 25% for warmth, while most locations in western NC ranked in the top 25% for dryness. August 2011 also brought several severe thunderstorm outbreaks with damaging winds, hail, and some localized flash flooding reported across the state.

Irene changed everything in eastern North Carolina. Before Irene, drought was the primary concern for municipalities and growers. Afterward, all concerns turned to infrastructure, flooding, and crop damages. Hurricane Irene brought with it the usual ingredients for damage: high winds, storm surge, a few tornadoes, and tremendous rainfall. Certainly, Irene will be retired, and go into the history books as one to remember in North Carolina.

The approach of Irene had many climatologists looking back in history to storms with similar tracks, especially Hurricane Floyd (1999), Hurricane Donna (1960), and the Great Beaufort Hurricane of 1879. Like Floyd in 1999, Irene was very large and produced tremendous rainfall, but Irene arrived during a drought and produced less widespread flooding than Floyd. Like Donna (1960), Irene had some strong winds and created new breaches in barrier islands. The most intense storm with a track similar to Irene's may be the Great Beaufort Hurricane of 1879, which made landfall near Atlantic Beach at Category 3 strength and caused wind gusts upwards of 150 mph, and flooding throughout the streets of coastal towns including Beaufort. It becomes difficult to imagine the damage that might have occurred along today's more developed and densely populated coast if Irene's intensity had been comparable to the storm of 1879.

Local Storms Reports for August 2011
Preliminary Count of LSRs courtesy National Weather Service
http://www.nc-climate.ncsu.edu/lsrdb/index.php

Precipitation for August 2011
Based on estimates from NWS Radar
Data courtesy NWS/NCEP

Precipitation for August 2011: Percent of Normal
Based on estimates from NWS Radar
Data courtesy NWS/NCEP

Impacts to Agriculture and Water Resources

The rainfall from Hurricane Irene resulted in an unprecedented 4 category improvement in the US Drought Monitor for parts of eastern NC. While the drought monitor rarely changes more than 1-2 categories in a single week, the widespread 10+ inch rainfall brought recovery to topsoil, rivers, and groundwater supplies in the region. However, streamflow and groundwater levels continue to be below-normal further inland, resulting in D0 and D1 drought designations even in counties that experienced several inches of rainfall from Irene.

However, continued dryness in western NC led to deterioration of drought conditions for communities in the foothills and mountains.

US Drought Monitor for North Carolina
Courtesy NC DENR Division of Water Resources

Hurricane Irene Strikes NC Coast
by Corey Davis

Hurricane Irene's landfall near Morehead City last month made it the first landfalling storm for North Carolina since Hurricane Isabel nearly eight years ago. Like Isabel, Hurricane Irene targeted the Outer Banks, bringing wind gusts as high as 115 mph near Cedar Island and causing two breaches of the barrier islands and NC Highway 12 just north of Rodanthe. A number of local storm reports were issued by the National Weather Service for the Outer Banks, including road flooding in Nags Head and an 83 mph wind gust on Pea Island.

Irene's impact wasn't limited to the Outer Banks, though. The heaviest rain from the storm fell along the Inner Banks and central coastal plain, with storm total rainfall greater than 10 inches in much of the region. The intense rainfall over a short time period led to flooding problems for some of the major state's major rivers. The Tar River near Greenville reached flood stage, with a crest of 14.79 feet on September 1. Fortunately, the rains did provide welcome relief for the severe drought conditions along much of the coast, and the Juniper Road wildfire in Pender County is now 100% controlled, according to the Forest Service.

At landfall, Irene was a Category 1 storm with maximum sustained winds of 85 mph. However, considering that Irene was at Category 3 strength less than 36 hours before it made landfall, the storm's impact could have been much worse. From a meteorological perspective, the storm first weakened when it underwent an eyewall replacement cycle. Storms often restrengthen once a new eye forms, which helps explain the National Hurricane Center's forecasts for a landfall at category three strength. However, dry air began to wrap around the north side of the eye and the storm encountered damaging vertical wind shear, which caused Irene to remain a weaker storm despite moving over the warm waters of the Gulf Stream. In hindsight, forecasters were able to make very accurate track forecasts nearly five days before the storm's landfall, which represents the significant forecasting improvements that have been made over the past 10 to 15 years – thanks largely to the development of computer models, better monitoring technology, and a more complete knowledge of storm dynamics. Similar advancements in all three areas should lead to improved track and intensity forecasts for Irene's meteorological brothers and sisters in years to come.

Landfalling Category 1 hurricanes within 20 statute miles of Morehead City, NC in past years
Graphic courtesy of the NOAA Coastal Services Center's Historical Hurricane Tracks Tool

We Say Goodbye, We Say Hello!

This month, the State Climate Office says goodbye to Bic Fort, who has served as our administration expert for over 10 years. Bic has served the NC State University community for 19 years, and will retire from NC State University and public service on September 9, 2011. Our warmest wishes go to Bic and his family.

We also welcome a new addition to the Climate Office staff. Heather Dinon has joined as a new climatologist effective August 1. Heather is not a new face to our group – she finished her MS degree this past spring from NC State University and was selected after a national search. She will be contributing to several projects and will focus on our agriculture and forestry science and extension efforts.